Imported Upstream version 58upstream/58

38 files changed, 4680 insertions, 479 deletions

diff --git a/src/pkg/go/ast/ast.go b/src/pkg/go/ast/ast.go
index 2fc1a6032..b1c7d4ab1 100644
--- a/src/pkg/go/ast/ast.go
+++ b/src/pkg/go/ast/ast.go
@@ -121,7 +121,7 @@ func (f *Field) End() token.Pos {
 // A FieldList represents a list of Fields, enclosed by parentheses or braces.
 type FieldList struct {
 	Opening token.Pos // position of opening parenthesis/brace, if any
-	List    []*Field  // field list
+	List    []*Field  // field list; or nil
 	Closing token.Pos // position of closing parenthesis/brace, if any
 }
 
@@ -334,7 +334,7 @@ type (
 	// A FuncType node represents a function type.
 	FuncType struct {
 		Func    token.Pos  // position of "func" keyword
-		Params  *FieldList // (incoming) parameters
+		Params  *FieldList // (incoming) parameters; or nil
 		Results *FieldList // (outgoing) results; or nil
 	}
 
@@ -515,10 +515,10 @@ type (
 
 	// An EmptyStmt node represents an empty statement.
 	// The "position" of the empty statement is the position
-	// of the immediately preceeding semicolon.
+	// of the immediately preceding semicolon.
 	//
 	EmptyStmt struct {
-		Semicolon token.Pos // position of preceeding ";"
+		Semicolon token.Pos // position of preceding ";"
 	}
 
 	// A LabeledStmt node represents a labeled statement.
@@ -596,7 +596,7 @@ type (
 	// An IfStmt node represents an if statement.
 	IfStmt struct {
 		If   token.Pos // position of "if" keyword
-		Init Stmt      // initalization statement; or nil
+		Init Stmt      // initialization statement; or nil
 		Cond Expr      // condition
 		Body *BlockStmt
 		Else Stmt // else branch; or nil
@@ -613,7 +613,7 @@ type (
 	// A SwitchStmt node represents an expression switch statement.
 	SwitchStmt struct {
 		Switch token.Pos  // position of "switch" keyword
-		Init   Stmt       // initalization statement; or nil
+		Init   Stmt       // initialization statement; or nil
 		Tag    Expr       // tag expression; or nil
 		Body   *BlockStmt // CaseClauses only
 	}
@@ -621,7 +621,7 @@ type (
 	// An TypeSwitchStmt node represents a type switch statement.
 	TypeSwitchStmt struct {
 		Switch token.Pos  // position of "switch" keyword
-		Init   Stmt       // initalization statement; or nil
+		Init   Stmt       // initialization statement; or nil
 		Assign Stmt       // x := y.(type) or y.(type)
 		Body   *BlockStmt // CaseClauses only
 	}
@@ -643,7 +643,7 @@ type (
 	// A ForStmt represents a for statement.
 	ForStmt struct {
 		For  token.Pos // position of "for" keyword
-		Init Stmt      // initalization statement; or nil
+		Init Stmt      // initialization statement; or nil
 		Cond Expr      // condition; or nil
 		Post Stmt      // post iteration statement; or nil
 		Body *BlockStmt
@@ -945,10 +945,10 @@ func (f *File) End() token.Pos {
 // collectively building a Go package.
 //
 type Package struct {
-	Name    string            // package name
-	Scope   *Scope            // package scope
-	Imports map[string]*Scope // map of import path -> package scope across all files
-	Files   map[string]*File  // Go source files by filename
+	Name    string             // package name
+	Scope   *Scope             // package scope across all files
+	Imports map[string]*Object // map of package id -> package object
+	Files   map[string]*File   // Go source files by filename
 }
 
 
diff --git a/src/pkg/go/ast/filter.go b/src/pkg/go/ast/filter.go
index 090d08d34..0907fd53d 100644
--- a/src/pkg/go/ast/filter.go
+++ b/src/pkg/go/ast/filter.go
@@ -21,24 +21,26 @@ func identListExports(list []*Ident) []*Ident {
 }
 
 
-// isExportedType assumes that typ is a correct type.
-func isExportedType(typ Expr) bool {
-	switch t := typ.(type) {
+// fieldName assumes that x is the type of an anonymous field and
+// returns the corresponding field name. If x is not an acceptable
+// anonymous field, the result is nil.
+//
+func fieldName(x Expr) *Ident {
+	switch t := x.(type) {
 	case *Ident:
-		return t.IsExported()
-	case *ParenExpr:
-		return isExportedType(t.X)
+		return t
 	case *SelectorExpr:
-		// assume t.X is a typename
-		return t.Sel.IsExported()
+		if _, ok := t.X.(*Ident); ok {
+			return t.Sel
+		}
 	case *StarExpr:
-		return isExportedType(t.X)
+		return fieldName(t.X)
 	}
-	return false
+	return nil
 }
 
 
-func fieldListExports(fields *FieldList, incomplete *bool) {
+func fieldListExports(fields *FieldList) (removedFields bool) {
 	if fields == nil {
 		return
 	}
@@ -53,12 +55,13 @@ func fieldListExports(fields *FieldList, incomplete *bool) {
 			// fields, so this is not absolutely correct.
 			// However, this cannot be done w/o complete
 			// type information.)
-			exported = isExportedType(f.Type)
+			name := fieldName(f.Type)
+			exported = name != nil && name.IsExported()
 		} else {
 			n := len(f.Names)
 			f.Names = identListExports(f.Names)
 			if len(f.Names) < n {
-				*incomplete = true
+				removedFields = true
 			}
 			exported = len(f.Names) > 0
 		}
@@ -69,9 +72,10 @@ func fieldListExports(fields *FieldList, incomplete *bool) {
 		}
 	}
 	if j < len(list) {
-		*incomplete = true
+		removedFields = true
 	}
 	fields.List = list[0:j]
+	return
 }
 
 
@@ -90,12 +94,16 @@ func typeExports(typ Expr) {
 	case *ArrayType:
 		typeExports(t.Elt)
 	case *StructType:
-		fieldListExports(t.Fields, &t.Incomplete)
+		if fieldListExports(t.Fields) {
+			t.Incomplete = true
+		}
 	case *FuncType:
 		paramListExports(t.Params)
 		paramListExports(t.Results)
 	case *InterfaceType:
-		fieldListExports(t.Methods, &t.Incomplete)
+		if fieldListExports(t.Methods) {
+			t.Incomplete = true
+		}
 	case *MapType:
 		typeExports(t.Key)
 		typeExports(t.Value)
@@ -206,13 +214,60 @@ func filterIdentList(list []*Ident, f Filter) []*Ident {
 }
 
 
+func filterFieldList(fields *FieldList, filter Filter) (removedFields bool) {
+	if fields == nil {
+		return false
+	}
+	list := fields.List
+	j := 0
+	for _, f := range list {
+		keepField := false
+		if len(f.Names) == 0 {
+			// anonymous field
+			name := fieldName(f.Type)
+			keepField = name != nil && filter(name.Name)
+		} else {
+			n := len(f.Names)
+			f.Names = filterIdentList(f.Names, filter)
+			if len(f.Names) < n {
+				removedFields = true
+			}
+			keepField = len(f.Names) > 0
+		}
+		if keepField {
+			list[j] = f
+			j++
+		}
+	}
+	if j < len(list) {
+		removedFields = true
+	}
+	fields.List = list[0:j]
+	return
+}
+
+
 func filterSpec(spec Spec, f Filter) bool {
 	switch s := spec.(type) {
 	case *ValueSpec:
 		s.Names = filterIdentList(s.Names, f)
 		return len(s.Names) > 0
 	case *TypeSpec:
-		return f(s.Name.Name)
+		if f(s.Name.Name) {
+			return true
+		}
+		switch t := s.Type.(type) {
+		case *StructType:
+			if filterFieldList(t.Fields, f) {
+				t.Incomplete = true
+			}
+			return len(t.Fields.List) > 0
+		case *InterfaceType:
+			if filterFieldList(t.Methods, f) {
+				t.Incomplete = true
+			}
+			return len(t.Methods.List) > 0
+		}
 	}
 	return false
 }
@@ -230,7 +285,14 @@ func filterSpecList(list []Spec, f Filter) []Spec {
 }
 
 
-func filterDecl(decl Decl, f Filter) bool {
+// FilterDecl trims the AST for a Go declaration in place by removing
+// all names (including struct field and interface method names, but
+// not from parameter lists) that don't pass through the filter f.
+//
+// FilterDecl returns true if there are any declared names left after
+// filtering; it returns false otherwise.
+//
+func FilterDecl(decl Decl, f Filter) bool {
 	switch d := decl.(type) {
 	case *GenDecl:
 		d.Specs = filterSpecList(d.Specs, f)
@@ -243,10 +305,10 @@ func filterDecl(decl Decl, f Filter) bool {
 
 
 // FilterFile trims the AST for a Go file in place by removing all
-// names from top-level declarations (but not from parameter lists
-// or inside types) that don't pass through the filter f. If the
-// declaration is empty afterwards, the declaration is removed from
-// the AST.
+// names from top-level declarations (including struct field and
+// interface method names, but not from parameter lists) that don't
+// pass through the filter f. If the declaration is empty afterwards,
+// the declaration is removed from the AST.
 // The File.comments list is not changed.
 //
 // FilterFile returns true if there are any top-level declarations
@@ -255,7 +317,7 @@ func filterDecl(decl Decl, f Filter) bool {
 func FilterFile(src *File, f Filter) bool {
 	j := 0
 	for _, d := range src.Decls {
-		if filterDecl(d, f) {
+		if FilterDecl(d, f) {
 			src.Decls[j] = d
 			j++
 		}
@@ -266,10 +328,10 @@ func FilterFile(src *File, f Filter) bool {
 
 
 // FilterPackage trims the AST for a Go package in place by removing all
-// names from top-level declarations (but not from parameter lists
-// or inside types) that don't pass through the filter f. If the
-// declaration is empty afterwards, the declaration is removed from
-// the AST.
+// names from top-level declarations (including struct field and
+// interface method names, but not from parameter lists) that don't
+// pass through the filter f. If the declaration is empty afterwards,
+// the declaration is removed from the AST.
 // The pkg.Files list is not changed, so that file names and top-level
 // package comments don't get lost.
 //
diff --git a/src/pkg/go/ast/resolve.go b/src/pkg/go/ast/resolve.go
index fddc3baab..ecd2e8a7c 100644
--- a/src/pkg/go/ast/resolve.go
+++ b/src/pkg/go/ast/resolve.go
@@ -11,6 +11,7 @@ import (
 	"go/scanner"
 	"go/token"
 	"os"
+	"strconv"
 )
 
 
@@ -57,11 +58,16 @@ func resolve(scope *Scope, ident *Ident) bool {
 }
 
 
-// NewPackage uses an Importer to resolve imports. Given an importPath,
-// an importer returns the imported package's name, its scope of exported
-// objects, and an error, if any.
-//
-type Importer func(path string) (name string, scope *Scope, err os.Error)
+// An Importer resolves import paths to package Objects.
+// The imports map records the packages already imported,
+// indexed by package id (canonical import path).
+// An Importer must determine the canonical import path and
+// check the map to see if it is already present in the imports map.
+// If so, the Importer can return the map entry.  Otherwise, the
+// Importer should load the package data for the given path into 
+// a new *Object (pkg), record pkg in the imports map, and then
+// return pkg.
+type Importer func(imports map[string]*Object, path string) (pkg *Object, err os.Error)
 
 
 // NewPackage creates a new Package node from a set of File nodes. It resolves
@@ -70,7 +76,7 @@ type Importer func(path string) (name string, scope *Scope, err os.Error)
 // used to resolve identifiers not declared in any of the package files. Any
 // remaining unresolved identifiers are reported as undeclared. If the files
 // belong to different packages, one package name is selected and files with
-// different package name are reported and then ignored.
+// different package names are reported and then ignored.
 // The result is a package node and a scanner.ErrorList if there were errors.
 //
 func NewPackage(fset *token.FileSet, files map[string]*File, importer Importer, universe *Scope) (*Package, os.Error) {
@@ -96,14 +102,8 @@ func NewPackage(fset *token.FileSet, files map[string]*File, importer Importer,
 		}
 	}
 
-	// imports maps import paths to package names and scopes
-	// TODO(gri): Eventually we like to get to the import scope from
-	//            a package object. Then we can have a map path -> Obj.
-	type importedPkg struct {
-		name  string
-		scope *Scope
-	}
-	imports := make(map[string]*importedPkg)
+	// package global mapping of imported package ids to package objects
+	imports := make(map[string]*Object)
 
 	// complete file scopes with imports and resolve identifiers
 	for _, file := range files {
@@ -117,42 +117,41 @@ func NewPackage(fset *token.FileSet, files map[string]*File, importer Importer,
 		importErrors := false
 		fileScope := NewScope(pkgScope)
 		for _, spec := range file.Imports {
-			// add import to global map of imports
-			path := string(spec.Path.Value)
-			path = path[1 : len(path)-1] // strip ""'s
-			pkg := imports[path]
-			if pkg == nil {
-				if importer == nil {
-					importErrors = true
-					continue
-				}
-				name, scope, err := importer(path)
-				if err != nil {
-					p.errorf(spec.Path.Pos(), "could not import %s (%s)", path, err)
-					importErrors = true
-					continue
-				}
-				pkg = &importedPkg{name, scope}
-				imports[path] = pkg
-				// TODO(gri) If a local package name != "." is provided,
-				// global identifier resolution could proceed even if the
-				// import failed. Consider adjusting the logic here a bit.
+			if importer == nil {
+				importErrors = true
+				continue
+			}
+			path, _ := strconv.Unquote(string(spec.Path.Value))
+			pkg, err := importer(imports, path)
+			if err != nil {
+				p.errorf(spec.Path.Pos(), "could not import %s (%s)", path, err)
+				importErrors = true
+				continue
 			}
+			// TODO(gri) If a local package name != "." is provided,
+			// global identifier resolution could proceed even if the
+			// import failed. Consider adjusting the logic here a bit.
+
 			// local name overrides imported package name
-			name := pkg.name
+			name := pkg.Name
 			if spec.Name != nil {
 				name = spec.Name.Name
 			}
+
 			// add import to file scope
 			if name == "." {
 				// merge imported scope with file scope
-				for _, obj := range pkg.scope.Objects {
+				for _, obj := range pkg.Data.(*Scope).Objects {
 					p.declare(fileScope, pkgScope, obj)
 				}
 			} else {
 				// declare imported package object in file scope
+				// (do not re-use pkg in the file scope but create
+				// a new object instead; the Decl field is different
+				// for different files)
 				obj := NewObj(Pkg, name)
 				obj.Decl = spec
+				obj.Data = pkg.Data
 				p.declare(fileScope, pkgScope, obj)
 			}
 		}
@@ -161,8 +160,8 @@ func NewPackage(fset *token.FileSet, files map[string]*File, importer Importer,
 		if importErrors {
 			// don't use the universe scope without correct imports
 			// (objects in the universe may be shadowed by imports;
-			// with missing imports identifiers might get resolved
-			// wrongly)
+			// with missing imports, identifiers might get resolved
+			// incorrectly to universe objects)
 			pkgScope.Outer = nil
 		}
 		i := 0
@@ -178,11 +177,5 @@ func NewPackage(fset *token.FileSet, files map[string]*File, importer Importer,
 		pkgScope.Outer = universe // reset universe scope
 	}
 
-	// collect all import paths and respective package scopes
-	importedScopes := make(map[string]*Scope)
-	for path, pkg := range imports {
-		importedScopes[path] = pkg.scope
-	}
-
-	return &Package{pkgName, pkgScope, importedScopes, files}, p.GetError(scanner.Sorted)
+	return &Package{pkgName, pkgScope, imports, files}, p.GetError(scanner.Sorted)
 }
diff --git a/src/pkg/go/ast/scope.go b/src/pkg/go/ast/scope.go
index 830d88aef..b966f786f 100644
--- a/src/pkg/go/ast/scope.go
+++ b/src/pkg/go/ast/scope.go
@@ -70,13 +70,24 @@ func (s *Scope) String() string {
 // ----------------------------------------------------------------------------
 // Objects
 
+// TODO(gri) Consider replacing the Object struct with an interface
+//           and a corresponding set of object implementations.
+
 // An Object describes a named language entity such as a package,
 // constant, type, variable, function (incl. methods), or label.
 //
+// The Data fields contains object-specific data:
+//
+//	Kind    Data type    Data value
+//	Pkg	*Scope       package scope
+//	Con     int          iota for the respective declaration
+//	Con     != nil       constant value
+//
 type Object struct {
 	Kind ObjKind
 	Name string      // declared name
 	Decl interface{} // corresponding Field, XxxSpec, FuncDecl, or LabeledStmt; or nil
+	Data interface{} // object-specific data; or nil
 	Type interface{} // place holder for type information; may be nil
 }
 
diff --git a/src/pkg/go/build/Makefile b/src/pkg/go/build/Makefile
new file mode 100644
index 000000000..4411940ae
--- /dev/null
+++ b/src/pkg/go/build/Makefile
@@ -0,0 +1,22 @@
+# Copyright 2009 The Go Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+include ../../../Make.inc
+
+TARG=go/build
+GOFILES=\
+	build.go\
+	dir.go\
+	path.go\
+	syslist.go\
+
+CLEANFILES+=syslist.go
+
+include ../../../Make.pkg
+
+syslist.go: ../../../Make.inc Makefile
+	echo '// Generated automatically by make.' >$@
+	echo 'package build' >>$@
+	echo 'const goosList = "$(GOOS_LIST)"' >>$@
+	echo 'const goarchList = "$(GOARCH_LIST)"' >>$@
diff --git a/src/pkg/go/build/build.go b/src/pkg/go/build/build.go
new file mode 100644
index 000000000..3cb8efe47
--- /dev/null
+++ b/src/pkg/go/build/build.go
@@ -0,0 +1,272 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package build provides tools for building Go packages.
+package build
+
+import (
+	"bytes"
+	"exec"
+	"fmt"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+)
+
+func (d *DirInfo) Build(targ string) ([]*Cmd, os.Error) {
+	b := &build{obj: "_obj/"}
+
+	goarch := runtime.GOARCH
+	if g := os.Getenv("GOARCH"); g != "" {
+		goarch = g
+	}
+	var err os.Error
+	b.arch, err = ArchChar(goarch)
+	if err != nil {
+		return nil, err
+	}
+
+	var gofiles = d.GoFiles // .go files to be built with gc
+	var ofiles []string     // *.GOARCH files to be linked or packed
+
+	// make build directory
+	b.mkdir(b.obj)
+
+	// cgo
+	if len(d.CgoFiles) > 0 {
+		outGo, outObj := b.cgo(d.CgoFiles)
+		gofiles = append(gofiles, outGo...)
+		ofiles = append(ofiles, outObj...)
+	}
+
+	// compile
+	if len(gofiles) > 0 {
+		ofile := b.obj + "_go_." + b.arch
+		b.gc(ofile, gofiles...)
+		ofiles = append(ofiles, ofile)
+	}
+
+	// assemble
+	for _, sfile := range d.SFiles {
+		ofile := b.obj + sfile[:len(sfile)-1] + b.arch
+		b.asm(ofile, sfile)
+		ofiles = append(ofiles, ofile)
+	}
+
+	if len(ofiles) == 0 {
+		return nil, os.NewError("make: no object files to build")
+	}
+
+	if d.IsCommand() {
+		b.ld(targ, ofiles...)
+	} else {
+		b.gopack(targ, ofiles...)
+	}
+
+	return b.cmds, nil
+}
+
+type Cmd struct {
+	Args   []string // command-line
+	Stdout string   // write standard output to this file, "" is passthrough
+	Input  []string // file paths (dependencies)
+	Output []string // file paths
+}
+
+func (c *Cmd) String() string {
+	return strings.Join(c.Args, " ")
+}
+
+func (c *Cmd) Run(dir string) os.Error {
+	out := new(bytes.Buffer)
+	cmd := exec.Command(c.Args[0], c.Args[1:]...)
+	cmd.Dir = dir
+	cmd.Stdout = out
+	cmd.Stderr = out
+	if c.Stdout != "" {
+		f, err := os.Create(filepath.Join(dir, c.Stdout))
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+		cmd.Stdout = f
+	}
+	if err := cmd.Run(); err != nil {
+		return fmt.Errorf("command %q: %v\n%v", c, err, out)
+	}
+	return nil
+}
+
+func (c *Cmd) Clean(dir string) (err os.Error) {
+	for _, fn := range c.Output {
+		if e := os.RemoveAll(fn); err == nil {
+			err = e
+		}
+	}
+	return
+}
+
+// ArchChar returns the architecture character for the given goarch.
+// For example, ArchChar("amd64") returns "6".
+func ArchChar(goarch string) (string, os.Error) {
+	switch goarch {
+	case "386":
+		return "8", nil
+	case "amd64":
+		return "6", nil
+	case "arm":
+		return "5", nil
+	}
+	return "", os.NewError("unsupported GOARCH " + goarch)
+}
+
+type build struct {
+	cmds []*Cmd
+	obj  string
+	arch string
+}
+
+func (b *build) add(c Cmd) {
+	b.cmds = append(b.cmds, &c)
+}
+
+func (b *build) mkdir(name string) {
+	b.add(Cmd{
+		Args:   []string{"mkdir", "-p", name},
+		Output: []string{name},
+	})
+}
+
+func (b *build) gc(ofile string, gofiles ...string) {
+	gc := b.arch + "g"
+	args := append([]string{gc, "-o", ofile}, gcImportArgs...)
+	args = append(args, gofiles...)
+	b.add(Cmd{
+		Args:   args,
+		Input:  gofiles,
+		Output: []string{ofile},
+	})
+}
+
+func (b *build) asm(ofile string, sfile string) {
+	asm := b.arch + "a"
+	b.add(Cmd{
+		Args:   []string{asm, "-o", ofile, sfile},
+		Input:  []string{sfile},
+		Output: []string{ofile},
+	})
+}
+
+func (b *build) ld(targ string, ofiles ...string) {
+	ld := b.arch + "l"
+	args := append([]string{ld, "-o", targ}, ldImportArgs...)
+	args = append(args, ofiles...)
+	b.add(Cmd{
+		Args:   args,
+		Input:  ofiles,
+		Output: []string{targ},
+	})
+}
+
+func (b *build) gopack(targ string, ofiles ...string) {
+	b.add(Cmd{
+		Args:   append([]string{"gopack", "grc", targ}, ofiles...),
+		Input:  ofiles,
+		Output: []string{targ},
+	})
+}
+
+func (b *build) cc(ofile string, cfiles ...string) {
+	cc := b.arch + "c"
+	dir := fmt.Sprintf("%s_%s", runtime.GOOS, runtime.GOARCH)
+	inc := filepath.Join(runtime.GOROOT(), "pkg", dir)
+	args := []string{cc, "-FVw", "-I", inc, "-o", ofile}
+	b.add(Cmd{
+		Args:   append(args, cfiles...),
+		Input:  cfiles,
+		Output: []string{ofile},
+	})
+}
+
+func (b *build) gccCompile(ofile, cfile string) {
+	b.add(Cmd{
+		Args:   gccArgs(b.arch, "-o", ofile, "-c", cfile),
+		Input:  []string{cfile},
+		Output: []string{ofile},
+	})
+}
+
+func (b *build) gccLink(ofile string, ofiles ...string) {
+	b.add(Cmd{
+		Args:   append(gccArgs(b.arch, "-o", ofile), ofiles...),
+		Input:  ofiles,
+		Output: []string{ofile},
+	})
+}
+
+func gccArgs(arch string, args ...string) []string {
+	// TODO(adg): HOST_CC
+	m := "-m32"
+	if arch == "6" {
+		m = "-m64"
+	}
+	return append([]string{"gcc", m, "-I", ".", "-g", "-fPIC", "-O2"}, args...)
+}
+
+func (b *build) cgo(cgofiles []string) (outGo, outObj []string) {
+	// cgo
+	// TODO(adg): CGOPKGPATH
+	// TODO(adg): CGO_FLAGS
+	gofiles := []string{b.obj + "_cgo_gotypes.go"}
+	cfiles := []string{b.obj + "_cgo_main.c", b.obj + "_cgo_export.c"}
+	for _, fn := range cgofiles {
+		f := b.obj + fn[:len(fn)-2]
+		gofiles = append(gofiles, f+"cgo1.go")
+		cfiles = append(cfiles, f+"cgo2.c")
+	}
+	defunC := b.obj + "_cgo_defun.c"
+	output := append([]string{defunC}, gofiles...)
+	output = append(output, cfiles...)
+	b.add(Cmd{
+		Args:   append([]string{"cgo", "--"}, cgofiles...),
+		Input:  cgofiles,
+		Output: output,
+	})
+	outGo = append(outGo, gofiles...)
+
+	// cc _cgo_defun.c
+	defunObj := b.obj + "_cgo_defun." + b.arch
+	b.cc(defunObj, defunC)
+	outObj = append(outObj, defunObj)
+
+	// gcc
+	linkobj := make([]string, 0, len(cfiles))
+	for _, cfile := range cfiles {
+		ofile := cfile[:len(cfile)-1] + "o"
+		b.gccCompile(ofile, cfile)
+		linkobj = append(linkobj, ofile)
+		if !strings.HasSuffix(ofile, "_cgo_main.o") {
+			outObj = append(outObj, ofile)
+		}
+	}
+	dynObj := b.obj + "_cgo1_.o"
+	b.gccLink(dynObj, linkobj...)
+
+	// cgo -dynimport
+	importC := b.obj + "_cgo_import.c"
+	b.add(Cmd{
+		Args:   []string{"cgo", "-dynimport", dynObj},
+		Stdout: importC,
+		Input:  []string{dynObj},
+		Output: []string{importC},
+	})
+
+	// cc _cgo_import.ARCH
+	importObj := b.obj + "_cgo_import." + b.arch
+	b.cc(importObj, importC)
+	outObj = append(outObj, importObj)
+
+	return
+}
diff --git a/src/pkg/go/build/build_test.go b/src/pkg/go/build/build_test.go
new file mode 100644
index 000000000..c543eddbd
--- /dev/null
+++ b/src/pkg/go/build/build_test.go
@@ -0,0 +1,57 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package build
+
+import (
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"testing"
+)
+
+var buildDirs = []string{
+	"pkg/path",
+	"cmd/gofix",
+	"pkg/big",
+	"pkg/go/build/cgotest",
+}
+
+func TestBuild(t *testing.T) {
+	out, err := filepath.Abs("_test/out")
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, d := range buildDirs {
+		if runtime.GOARCH == "arm" && strings.Contains(d, "/cgo") {
+			// no cgo for arm, yet.
+			continue
+		}
+		dir := filepath.Join(runtime.GOROOT(), "src", d)
+		testBuild(t, dir, out)
+	}
+}
+
+func testBuild(t *testing.T, dir, targ string) {
+	d, err := ScanDir(dir, true)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+	defer os.Remove(targ)
+	cmds, err := d.Build(targ)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+	for _, c := range cmds {
+		t.Log("Run:", c)
+		err = c.Run(dir)
+		if err != nil {
+			t.Error(c, err)
+			return
+		}
+	}
+}
diff --git a/src/pkg/go/build/cgotest/file.go b/src/pkg/go/build/cgotest/file.go
new file mode 100644
index 000000000..3b2a2e7d9
--- /dev/null
+++ b/src/pkg/go/build/cgotest/file.go
@@ -0,0 +1,45 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+A trivial example of wrapping a C library in Go.
+For a more complex example and explanation,
+see ../gmp/gmp.go.
+*/
+
+package stdio
+
+/*
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <errno.h>
+
+char* greeting = "hello, world";
+*/
+import "C"
+import "unsafe"
+
+type File C.FILE
+
+// TODO(brainman): uncomment once stdout and stderr references are working on Windows.
+//var Stdout = (*File)(C.stdout)
+//var Stderr = (*File)(C.stderr)
+
+// Test reference to library symbol.
+// Stdout and stderr are too special to be a reliable test.
+var myerr = C.sys_errlist
+
+func (f *File) WriteString(s string) {
+	p := C.CString(s)
+	C.fputs(p, (*C.FILE)(f))
+	C.free(unsafe.Pointer(p))
+	f.Flush()
+}
+
+func (f *File) Flush() {
+	C.fflush((*C.FILE)(f))
+}
+
+var Greeting = C.GoString(C.greeting)
diff --git a/src/pkg/go/build/dir.go b/src/pkg/go/build/dir.go
new file mode 100644
index 000000000..77e80bff0
--- /dev/null
+++ b/src/pkg/go/build/dir.go
@@ -0,0 +1,173 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package build
+
+import (
+	"go/parser"
+	"go/token"
+	"log"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"runtime"
+)
+
+type DirInfo struct {
+	GoFiles  []string // .go files in dir (excluding CgoFiles)
+	CgoFiles []string // .go files that import "C"
+	CFiles   []string // .c files in dir
+	SFiles   []string // .s files in dir
+	Imports  []string // All packages imported by goFiles
+	PkgName  string   // Name of package in dir
+}
+
+func (d *DirInfo) IsCommand() bool {
+	return d.PkgName == "main"
+}
+
+// ScanDir returns a structure with details about the Go content found
+// in the given directory. The file lists exclude:
+//
+//	- files in package main (unless allowMain is true)
+//	- files in package documentation
+//	- files ending in _test.go
+// 	- files starting with _ or .
+//
+// Only files that satisfy the goodOSArch function are included.
+func ScanDir(dir string, allowMain bool) (info *DirInfo, err os.Error) {
+	f, err := os.Open(dir)
+	if err != nil {
+		return nil, err
+	}
+	dirs, err := f.Readdir(-1)
+	f.Close()
+	if err != nil {
+		return nil, err
+	}
+
+	var di DirInfo
+	imported := make(map[string]bool)
+	pkgName := ""
+	fset := token.NewFileSet()
+	for i := range dirs {
+		d := &dirs[i]
+		if strings.HasPrefix(d.Name, "_") ||
+			strings.HasPrefix(d.Name, ".") {
+			continue
+		}
+		if !goodOSArch(d.Name) {
+			continue
+		}
+
+		switch filepath.Ext(d.Name) {
+		case ".go":
+			if strings.HasSuffix(d.Name, "_test.go") {
+				continue
+			}
+		case ".c":
+			di.CFiles = append(di.CFiles, d.Name)
+			continue
+		case ".s":
+			di.SFiles = append(di.SFiles, d.Name)
+			continue
+		default:
+			continue
+		}
+
+		filename := filepath.Join(dir, d.Name)
+		pf, err := parser.ParseFile(fset, filename, nil, parser.ImportsOnly)
+		if err != nil {
+			return nil, err
+		}
+		s := string(pf.Name.Name)
+		if s == "main" && !allowMain {
+			continue
+		}
+		if s == "documentation" {
+			continue
+		}
+		if pkgName == "" {
+			pkgName = s
+		} else if pkgName != s {
+			// Only if all files in the directory are in package main
+			// do we return pkgName=="main".
+			// A mix of main and another package reverts
+			// to the original (allowMain=false) behaviour.
+			if s == "main" || pkgName == "main" {
+				return ScanDir(dir, false)
+			}
+			return nil, os.ErrorString("multiple package names in " + dir)
+		}
+		isCgo := false
+		for _, spec := range pf.Imports {
+			quoted := string(spec.Path.Value)
+			path, err := strconv.Unquote(quoted)
+			if err != nil {
+				log.Panicf("%s: parser returned invalid quoted string: <%s>", filename, quoted)
+			}
+			imported[path] = true
+			if path == "C" {
+				isCgo = true
+			}
+		}
+		if isCgo {
+			di.CgoFiles = append(di.CgoFiles, d.Name)
+		} else {
+			di.GoFiles = append(di.GoFiles, d.Name)
+		}
+	}
+	di.Imports = make([]string, len(imported))
+	i := 0
+	for p := range imported {
+		di.Imports[i] = p
+		i++
+	}
+	return &di, nil
+}
+
+// goodOSArch returns false if the filename contains a $GOOS or $GOARCH
+// suffix which does not match the current system.
+// The recognized filename formats are:
+//
+//     name_$(GOOS).*
+//     name_$(GOARCH).*
+//     name_$(GOOS)_$(GOARCH).*
+//
+func goodOSArch(filename string) bool {
+	if dot := strings.Index(filename, "."); dot != -1 {
+		filename = filename[:dot]
+	}
+	l := strings.Split(filename, "_", -1)
+	n := len(l)
+	if n == 0 {
+		return true
+	}
+	if good, known := goodOS[l[n-1]]; known {
+		return good
+	}
+	if good, known := goodArch[l[n-1]]; known {
+		if !good || n < 2 {
+			return false
+		}
+		good, known = goodOS[l[n-2]]
+		return good || !known
+	}
+	return true
+}
+
+var goodOS = make(map[string]bool)
+var goodArch = make(map[string]bool)
+
+func init() {
+	goodOS = make(map[string]bool)
+	goodArch = make(map[string]bool)
+	for _, v := range strings.Fields(goosList) {
+		goodOS[v] = v == runtime.GOOS
+	}
+	for _, v := range strings.Fields(goarchList) {
+		goodArch[v] = v == runtime.GOARCH
+	}
+}
diff --git a/src/pkg/go/build/path.go b/src/pkg/go/build/path.go
new file mode 100644
index 000000000..8ad39fb0f
--- /dev/null
+++ b/src/pkg/go/build/path.go
@@ -0,0 +1,163 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package build
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+)
+
+// Path is a validated list of Trees derived from $GOPATH at init.
+var Path []*Tree
+
+// Tree describes a Go source tree, either $GOROOT or one from $GOPATH.
+type Tree struct {
+	Path   string
+	Goroot bool
+}
+
+func newTree(p string) (*Tree, os.Error) {
+	if !filepath.IsAbs(p) {
+		return nil, os.NewError("must be absolute")
+	}
+	ep, err := filepath.EvalSymlinks(p)
+	if err != nil {
+		return nil, err
+	}
+	return &Tree{Path: ep}, nil
+}
+
+// SrcDir returns the tree's package source directory.
+func (t *Tree) SrcDir() string {
+	if t.Goroot {
+		return filepath.Join(t.Path, "src", "pkg")
+	}
+	return filepath.Join(t.Path, "src")
+}
+
+// PkgDir returns the tree's package object directory.
+func (t *Tree) PkgDir() string {
+	goos, goarch := runtime.GOOS, runtime.GOARCH
+	if e := os.Getenv("GOOS"); e != "" {
+		goos = e
+	}
+	if e := os.Getenv("GOARCH"); e != "" {
+		goarch = e
+	}
+	return filepath.Join(t.Path, "pkg", goos+"_"+goarch)
+}
+
+// BinDir returns the tree's binary executable directory.
+func (t *Tree) BinDir() string {
+	return filepath.Join(t.Path, "bin")
+}
+
+// HasSrc returns whether the given package's
+// source can be found inside this Tree.
+func (t *Tree) HasSrc(pkg string) bool {
+	fi, err := os.Stat(filepath.Join(t.SrcDir(), pkg))
+	if err != nil {
+		return false
+	}
+	return fi.IsDirectory()
+}
+
+// HasPkg returns whether the given package's
+// object file can be found inside this Tree.
+func (t *Tree) HasPkg(pkg string) bool {
+	fi, err := os.Stat(filepath.Join(t.PkgDir(), pkg+".a"))
+	if err != nil {
+		return false
+	}
+	return fi.IsRegular()
+	// TODO(adg): check object version is consistent
+}
+
+var ErrNotFound = os.NewError("package could not be found locally")
+
+// FindTree takes an import or filesystem path and returns the
+// tree where the package source should be and the package import path.
+func FindTree(path string) (tree *Tree, pkg string, err os.Error) {
+	if isLocalPath(path) {
+		if path, err = filepath.Abs(path); err != nil {
+			return
+		}
+		for _, t := range Path {
+			tpath := t.SrcDir() + string(filepath.Separator)
+			if !strings.HasPrefix(path, tpath) {
+				continue
+			}
+			tree = t
+			pkg = path[len(tpath):]
+			return
+		}
+		err = fmt.Errorf("path %q not inside a GOPATH", path)
+		return
+	}
+	tree = defaultTree
+	pkg = path
+	for _, t := range Path {
+		if t.HasSrc(pkg) {
+			tree = t
+			return
+		}
+	}
+	err = ErrNotFound
+	return
+}
+
+// isLocalPath returns whether the given path is local (/foo ./foo ../foo . ..)
+func isLocalPath(s string) bool {
+	const sep = string(filepath.Separator)
+	return strings.HasPrefix(s, sep) || strings.HasPrefix(s, "."+sep) || strings.HasPrefix(s, ".."+sep) || s == "." || s == ".."
+}
+
+var (
+	// argument lists used by the build's gc and ld methods
+	gcImportArgs []string
+	ldImportArgs []string
+
+	// default tree for remote packages
+	defaultTree *Tree
+)
+
+// set up Path: parse and validate GOROOT and GOPATH variables
+func init() {
+	root := runtime.GOROOT()
+	p, err := newTree(root)
+	if err != nil {
+		log.Fatalf("Invalid GOROOT %q: %v", root, err)
+	}
+	p.Goroot = true
+	Path = []*Tree{p}
+
+	for _, p := range filepath.SplitList(os.Getenv("GOPATH")) {
+		if p == "" {
+			continue
+		}
+		t, err := newTree(p)
+		if err != nil {
+			log.Printf("Invalid GOPATH %q: %v", p, err)
+			continue
+		}
+		Path = append(Path, t)
+		gcImportArgs = append(gcImportArgs, "-I", t.PkgDir())
+		ldImportArgs = append(ldImportArgs, "-L", t.PkgDir())
+
+		// select first GOPATH entry as default
+		if defaultTree == nil {
+			defaultTree = t
+		}
+	}
+
+	// use GOROOT if no valid GOPATH specified
+	if defaultTree == nil {
+		defaultTree = Path[0]
+	}
+}
diff --git a/src/pkg/go/build/syslist_test.go b/src/pkg/go/build/syslist_test.go
new file mode 100644
index 000000000..eb0e5dcb6
--- /dev/null
+++ b/src/pkg/go/build/syslist_test.go
@@ -0,0 +1,62 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package build
+
+import (
+	"runtime"
+	"testing"
+)
+
+var (
+	thisOS    = runtime.GOOS
+	thisArch  = runtime.GOARCH
+	otherOS   = anotherOS()
+	otherArch = anotherArch()
+)
+
+func anotherOS() string {
+	if thisOS != "darwin" {
+		return "darwin"
+	}
+	return "linux"
+}
+
+func anotherArch() string {
+	if thisArch != "amd64" {
+		return "amd64"
+	}
+	return "386"
+}
+
+type GoodFileTest struct {
+	name   string
+	result bool
+}
+
+var tests = []GoodFileTest{
+	{"file.go", true},
+	{"file.c", true},
+	{"file_foo.go", true},
+	{"file_" + thisArch + ".go", true},
+	{"file_" + otherArch + ".go", false},
+	{"file_" + thisOS + ".go", true},
+	{"file_" + otherOS + ".go", false},
+	{"file_" + thisOS + "_" + thisArch + ".go", true},
+	{"file_" + otherOS + "_" + thisArch + ".go", false},
+	{"file_" + thisOS + "_" + otherArch + ".go", false},
+	{"file_" + otherOS + "_" + otherArch + ".go", false},
+	{"file_foo_" + thisArch + ".go", true},
+	{"file_foo_" + otherArch + ".go", false},
+	{"file_" + thisOS + ".c", true},
+	{"file_" + otherOS + ".c", false},
+}
+
+func TestGoodOSArch(t *testing.T) {
+	for _, test := range tests {
+		if goodOSArch(test.name) != test.result {
+			t.Fatalf("goodOSArch(%q) != %v", test.name, test.result)
+		}
+	}
+}
diff --git a/src/pkg/go/doc/doc.go b/src/pkg/go/doc/doc.go
index 29d205d39..a7a7e0a32 100644
--- a/src/pkg/go/doc/doc.go
+++ b/src/pkg/go/doc/doc.go
@@ -572,6 +572,20 @@ func (doc *docReader) newDoc(importpath string, filenames []string) *PackageDoc
 type Filter func(string) bool
 
 
+func matchFields(fields *ast.FieldList, f Filter) bool {
+	if fields != nil {
+		for _, field := range fields.List {
+			for _, name := range field.Names {
+				if f(name.Name) {
+					return true
+				}
+			}
+		}
+	}
+	return false
+}
+
+
 func matchDecl(d *ast.GenDecl, f Filter) bool {
 	for _, d := range d.Specs {
 		switch v := d.(type) {
@@ -585,6 +599,16 @@ func matchDecl(d *ast.GenDecl, f Filter) bool {
 			if f(v.Name.Name) {
 				return true
 			}
+			switch t := v.Type.(type) {
+			case *ast.StructType:
+				if matchFields(t.Fields, f) {
+					return true
+				}
+			case *ast.InterfaceType:
+				if matchFields(t.Methods, f) {
+					return true
+				}
+			}
 		}
 	}
 	return false
diff --git a/src/pkg/go/parser/parser.go b/src/pkg/go/parser/parser.go
index 5c57e41d1..586ee3a9a 100644
--- a/src/pkg/go/parser/parser.go
+++ b/src/pkg/go/parser/parser.go
@@ -54,7 +54,7 @@ type parser struct {
 	// Non-syntactic parser control
 	exprLev int // < 0: in control clause, >= 0: in expression
 
-	// Ordinary identifer scopes
+	// Ordinary identifier scopes
 	pkgScope   *ast.Scope        // pkgScope.Outer == nil
 	topScope   *ast.Scope        // top-most scope; may be pkgScope
 	unresolved []*ast.Ident      // unresolved identifiers
@@ -131,14 +131,16 @@ func (p *parser) closeLabelScope() {
 }
 
 
-func (p *parser) declare(decl interface{}, scope *ast.Scope, kind ast.ObjKind, idents ...*ast.Ident) {
+func (p *parser) declare(decl, data interface{}, scope *ast.Scope, kind ast.ObjKind, idents ...*ast.Ident) {
 	for _, ident := range idents {
 		assert(ident.Obj == nil, "identifier already declared or resolved")
+		obj := ast.NewObj(kind, ident.Name)
+		// remember the corresponding declaration for redeclaration
+		// errors and global variable resolution/typechecking phase
+		obj.Decl = decl
+		obj.Data = data
+		ident.Obj = obj
 		if ident.Name != "_" {
-			obj := ast.NewObj(kind, ident.Name)
-			// remember the corresponding declaration for redeclaration
-			// errors and global variable resolution/typechecking phase
-			obj.Decl = decl
 			if alt := scope.Insert(obj); alt != nil && p.mode&DeclarationErrors != 0 {
 				prevDecl := ""
 				if pos := alt.Pos(); pos.IsValid() {
@@ -146,7 +148,6 @@ func (p *parser) declare(decl interface{}, scope *ast.Scope, kind ast.ObjKind, i
 				}
 				p.error(ident.Pos(), fmt.Sprintf("%s redeclared in this block%s", ident.Name, prevDecl))
 			}
-			ident.Obj = obj
 		}
 	}
 }
@@ -159,17 +160,17 @@ func (p *parser) shortVarDecl(idents []*ast.Ident) {
 	n := 0 // number of new variables
 	for _, ident := range idents {
 		assert(ident.Obj == nil, "identifier already declared or resolved")
+		obj := ast.NewObj(ast.Var, ident.Name)
+		// short var declarations cannot have redeclaration errors
+		// and are not global => no need to remember the respective
+		// declaration
+		ident.Obj = obj
 		if ident.Name != "_" {
-			obj := ast.NewObj(ast.Var, ident.Name)
-			// short var declarations cannot have redeclaration errors
-			// and are not global => no need to remember the respective
-			// declaration
-			alt := p.topScope.Insert(obj)
-			if alt == nil {
+			if alt := p.topScope.Insert(obj); alt != nil {
+				ident.Obj = alt // redeclaration
+			} else {
 				n++ // new declaration
-				alt = obj
 			}
-			ident.Obj = alt
 		}
 	}
 	if n == 0 && p.mode&DeclarationErrors != 0 {
@@ -596,7 +597,7 @@ func (p *parser) parseFieldDecl(scope *ast.Scope) *ast.Field {
 	p.expectSemi() // call before accessing p.linecomment
 
 	field := &ast.Field{doc, idents, typ, tag, p.lineComment}
-	p.declare(field, scope, ast.Var, idents...)
+	p.declare(field, nil, scope, ast.Var, idents...)
 
 	return field
 }
@@ -707,7 +708,7 @@ func (p *parser) parseParameterList(scope *ast.Scope, ellipsisOk bool) (params [
 		params = append(params, field)
 		// Go spec: The scope of an identifier denoting a function
 		// parameter or result variable is the function body.
-		p.declare(field, scope, ast.Var, idents...)
+		p.declare(field, nil, scope, ast.Var, idents...)
 		if p.tok == token.COMMA {
 			p.next()
 		}
@@ -719,7 +720,7 @@ func (p *parser) parseParameterList(scope *ast.Scope, ellipsisOk bool) (params [
 			params = append(params, field)
 			// Go spec: The scope of an identifier denoting a function
 			// parameter or result variable is the function body.
-			p.declare(field, scope, ast.Var, idents...)
+			p.declare(field, nil, scope, ast.Var, idents...)
 			if p.tok != token.COMMA {
 				break
 			}
@@ -818,11 +819,12 @@ func (p *parser) parseMethodSpec(scope *ast.Scope) *ast.Field {
 	} else {
 		// embedded interface
 		typ = x
+		p.resolve(typ)
 	}
 	p.expectSemi() // call before accessing p.linecomment
 
 	spec := &ast.Field{doc, idents, typ, nil, p.lineComment}
-	p.declare(spec, scope, ast.Fun, idents...)
+	p.declare(spec, nil, scope, ast.Fun, idents...)
 
 	return spec
 }
@@ -1476,7 +1478,7 @@ func (p *parser) parseSimpleStmt(labelOk bool) ast.Stmt {
 			// in which it is declared and excludes the body of any nested
 			// function.
 			stmt := &ast.LabeledStmt{label, colon, p.parseStmt()}
-			p.declare(stmt, p.labelScope, ast.Lbl, label)
+			p.declare(stmt, nil, p.labelScope, ast.Lbl, label)
 			return stmt
 		}
 		p.error(x[0].Pos(), "illegal label declaration")
@@ -1780,10 +1782,6 @@ func (p *parser) parseCommClause() *ast.CommClause {
 				rhs = lhs[0]
 				lhs = nil // there is no lhs
 			}
-			if x, isUnary := rhs.(*ast.UnaryExpr); !isUnary || x.Op != token.ARROW {
-				p.errorExpected(rhs.Pos(), "send or receive operation")
-				rhs = &ast.BadExpr{rhs.Pos(), rhs.End()}
-			}
 			if lhs != nil {
 				comm = &ast.AssignStmt{lhs, pos, tok, []ast.Expr{rhs}}
 			} else {
@@ -2004,7 +2002,7 @@ func parseConstSpec(p *parser, doc *ast.CommentGroup, iota int) ast.Spec {
 	// the end of the innermost containing block.
 	// (Global identifiers are resolved in a separate phase after parsing.)
 	spec := &ast.ValueSpec{doc, idents, typ, values, p.lineComment}
-	p.declare(spec, p.topScope, ast.Con, idents...)
+	p.declare(spec, iota, p.topScope, ast.Con, idents...)
 
 	return spec
 }
@@ -2022,7 +2020,7 @@ func parseTypeSpec(p *parser, doc *ast.CommentGroup, _ int) ast.Spec {
 	// containing block.
 	// (Global identifiers are resolved in a separate phase after parsing.)
 	spec := &ast.TypeSpec{doc, ident, nil, nil}
-	p.declare(spec, p.topScope, ast.Typ, ident)
+	p.declare(spec, nil, p.topScope, ast.Typ, ident)
 
 	spec.Type = p.parseType()
 	p.expectSemi() // call before accessing p.linecomment
@@ -2051,7 +2049,7 @@ func parseVarSpec(p *parser, doc *ast.CommentGroup, _ int) ast.Spec {
 	// the end of the innermost containing block.
 	// (Global identifiers are resolved in a separate phase after parsing.)
 	spec := &ast.ValueSpec{doc, idents, typ, values, p.lineComment}
-	p.declare(spec, p.topScope, ast.Var, idents...)
+	p.declare(spec, nil, p.topScope, ast.Var, idents...)
 
 	return spec
 }
@@ -2143,7 +2141,7 @@ func (p *parser) parseFuncDecl() *ast.FuncDecl {
 		// init() functions cannot be referred to and there may
 		// be more than one - don't put them in the pkgScope
 		if ident.Name != "init" {
-			p.declare(decl, p.pkgScope, ast.Fun, ident)
+			p.declare(decl, nil, p.pkgScope, ast.Fun, ident)
 		}
 	}
 
diff --git a/src/pkg/go/parser/parser_test.go b/src/pkg/go/parser/parser_test.go
index 2f1ee6bfc..5b52f51d4 100644
--- a/src/pkg/go/parser/parser_test.go
+++ b/src/pkg/go/parser/parser_test.go
@@ -51,6 +51,7 @@ var validPrograms = []interface{}{
 	`package p; type T []int; func f() { for _ = range []int{T{42}[0]} {} };`,
 	`package p; var a = T{{1, 2}, {3, 4}}`,
 	`package p; func f() { select { case <- c: case c <- d: case c <- <- d: case <-c <- d: } };`,
+	`package p; func f() { select { case x := (<-c): } };`,
 	`package p; func f() { if ; true {} };`,
 	`package p; func f() { switch ; {} };`,
 }
diff --git a/src/pkg/go/printer/nodes.go b/src/pkg/go/printer/nodes.go
index 86c327930..0fca8a161 100644
--- a/src/pkg/go/printer/nodes.go
+++ b/src/pkg/go/printer/nodes.go
@@ -33,7 +33,7 @@ import (
 // line break was printed; returns false otherwise.
 //
 // TODO(gri): linebreak may add too many lines if the next statement at "line"
-//            is preceeded by comments because the computation of n assumes
+//            is preceded by comments because the computation of n assumes
 //            the current position before the comment and the target position
 //            after the comment. Thus, after interspersing such comments, the
 //            space taken up by them is not considered to reduce the number of
@@ -215,12 +215,13 @@ func (p *printer) exprList(prev0 token.Pos, list []ast.Expr, depth int, mode exp
 		}
 
 		if i > 0 {
-			if mode&commaSep != 0 {
+			switch {
+			case mode&commaSep != 0:
 				p.print(token.COMMA)
-			}
-			if mode&periodSep != 0 {
+			case mode&periodSep != 0:
 				p.print(token.PERIOD)
 			}
+			needsBlank := mode&periodSep == 0 // period-separated list elements don't need a blank
 			if prevLine < line && prevLine > 0 && line > 0 {
 				// lines are broken using newlines so comments remain aligned
 				// unless forceFF is set or there are multiple expressions on
@@ -229,11 +230,12 @@ func (p *printer) exprList(prev0 token.Pos, list []ast.Expr, depth int, mode exp
 					ws = ignore
 					*multiLine = true
 					prevBreak = i
+					needsBlank = false // we got a line break instead
 				}
-			} else if mode&periodSep == 0 {
+			}
+			if needsBlank {
 				p.print(blank)
 			}
-			// period-separated list elements don't need a blank
 		}
 
 		if isPair && size > 0 && len(list) > 1 {
@@ -438,8 +440,8 @@ func (p *printer) fieldList(fields *ast.FieldList, isStruct, isIncomplete bool)
 			if len(list) > 0 {
 				p.print(formfeed)
 			}
-			p.flush(p.fset.Position(rbrace), token.RBRACE) // make sure we don't loose the last line comment
-			p.setLineComment("// contains unexported fields")
+			p.flush(p.fset.Position(rbrace), token.RBRACE) // make sure we don't lose the last line comment
+			p.setLineComment("// contains filtered or unexported fields")
 		}
 
 	} else { // interface
@@ -465,8 +467,8 @@ func (p *printer) fieldList(fields *ast.FieldList, isStruct, isIncomplete bool)
 			if len(list) > 0 {
 				p.print(formfeed)
 			}
-			p.flush(p.fset.Position(rbrace), token.RBRACE) // make sure we don't loose the last line comment
-			p.setLineComment("// contains unexported methods")
+			p.flush(p.fset.Position(rbrace), token.RBRACE) // make sure we don't lose the last line comment
+			p.setLineComment("// contains filtered or unexported methods")
 		}
 
 	}
@@ -1189,6 +1191,97 @@ func (p *printer) stmt(stmt ast.Stmt, nextIsRBrace bool, multiLine *bool) {
 // ----------------------------------------------------------------------------
 // Declarations
 
+// The keepTypeColumn function determines if the type column of a series of
+// consecutive const or var declarations must be kept, or if initialization
+// values (V) can be placed in the type column (T) instead. The i'th entry
+// in the result slice is true if the type column in spec[i] must be kept.
+//
+// For example, the declaration:
+//
+//	const (
+//		foobar int = 42 // comment
+//		x          = 7  // comment
+//		foo
+//              bar = 991
+//	)
+//
+// leads to the type/values matrix below. A run of value columns (V) can
+// be moved into the type column if there is no type for any of the values
+// in that column (we only move entire columns so that they align properly).
+//
+//	matrix        formatted     result
+//                    matrix
+//	T  V    ->    T  V     ->   true      there is a T and so the type
+//	-  V          -  V          true      column must be kept
+//	-  -          -  -          false
+//	-  V          V  -          false     V is moved into T column
+//
+func keepTypeColumn(specs []ast.Spec) []bool {
+	m := make([]bool, len(specs))
+
+	populate := func(i, j int, keepType bool) {
+		if keepType {
+			for ; i < j; i++ {
+				m[i] = true
+			}
+		}
+	}
+
+	i0 := -1 // if i0 >= 0 we are in a run and i0 is the start of the run
+	var keepType bool
+	for i, s := range specs {
+		t := s.(*ast.ValueSpec)
+		if t.Values != nil {
+			if i0 < 0 {
+				// start of a run of ValueSpecs with non-nil Values
+				i0 = i
+				keepType = false
+			}
+		} else {
+			if i0 >= 0 {
+				// end of a run
+				populate(i0, i, keepType)
+				i0 = -1
+			}
+		}
+		if t.Type != nil {
+			keepType = true
+		}
+	}
+	if i0 >= 0 {
+		// end of a run
+		populate(i0, len(specs), keepType)
+	}
+
+	return m
+}
+
+
+func (p *printer) valueSpec(s *ast.ValueSpec, keepType, doIndent bool, multiLine *bool) {
+	p.setComment(s.Doc)
+	p.identList(s.Names, doIndent, multiLine) // always present
+	extraTabs := 3
+	if s.Type != nil || keepType {
+		p.print(vtab)
+		extraTabs--
+	}
+	if s.Type != nil {
+		p.expr(s.Type, multiLine)
+	}
+	if s.Values != nil {
+		p.print(vtab, token.ASSIGN)
+		p.exprList(token.NoPos, s.Values, 1, blankStart|commaSep, multiLine, token.NoPos)
+		extraTabs--
+	}
+	if s.Comment != nil {
+		for ; extraTabs > 0; extraTabs-- {
+			p.print(vtab)
+		}
+		p.setComment(s.Comment)
+	}
+}
+
+
 // The parameter n is the number of specs in the group. If doIndent is set,
 // multi-line identifier lists in the spec are indented when the first
 // linebreak is encountered.
@@ -1206,38 +1299,20 @@ func (p *printer) spec(spec ast.Spec, n int, doIndent bool, multiLine *bool) {
 		p.setComment(s.Comment)
 
 	case *ast.ValueSpec:
+		if n != 1 {
+			p.internalError("expected n = 1; got", n)
+		}
 		p.setComment(s.Doc)
 		p.identList(s.Names, doIndent, multiLine) // always present
-		if n == 1 {
-			if s.Type != nil {
-				p.print(blank)
-				p.expr(s.Type, multiLine)
-			}
-			if s.Values != nil {
-				p.print(blank, token.ASSIGN)
-				p.exprList(token.NoPos, s.Values, 1, blankStart|commaSep, multiLine, token.NoPos)
-			}
-			p.setComment(s.Comment)
-
-		} else {
-			extraTabs := 3
-			if s.Type != nil {
-				p.print(vtab)
-				p.expr(s.Type, multiLine)
-				extraTabs--
-			}
-			if s.Values != nil {
-				p.print(vtab, token.ASSIGN)
-				p.exprList(token.NoPos, s.Values, 1, blankStart|commaSep, multiLine, token.NoPos)
-				extraTabs--
-			}
-			if s.Comment != nil {
-				for ; extraTabs > 0; extraTabs-- {
-					p.print(vtab)
-				}
-				p.setComment(s.Comment)
-			}
+		if s.Type != nil {
+			p.print(blank)
+			p.expr(s.Type, multiLine)
+		}
+		if s.Values != nil {
+			p.print(blank, token.ASSIGN)
+			p.exprList(token.NoPos, s.Values, 1, blankStart|commaSep, multiLine, token.NoPos)
 		}
+		p.setComment(s.Comment)
 
 	case *ast.TypeSpec:
 		p.setComment(s.Doc)
@@ -1264,15 +1339,29 @@ func (p *printer) genDecl(d *ast.GenDecl, multiLine *bool) {
 	if d.Lparen.IsValid() {
 		// group of parenthesized declarations
 		p.print(d.Lparen, token.LPAREN)
-		if len(d.Specs) > 0 {
+		if n := len(d.Specs); n > 0 {
 			p.print(indent, formfeed)
-			var ml bool
-			for i, s := range d.Specs {
-				if i > 0 {
-					p.linebreak(p.fset.Position(s.Pos()).Line, 1, ignore, ml)
+			if n > 1 && (d.Tok == token.CONST || d.Tok == token.VAR) {
+				// two or more grouped const/var declarations:
+				// determine if the type column must be kept
+				keepType := keepTypeColumn(d.Specs)
+				var ml bool
+				for i, s := range d.Specs {
+					if i > 0 {
+						p.linebreak(p.fset.Position(s.Pos()).Line, 1, ignore, ml)
+					}
+					ml = false
+					p.valueSpec(s.(*ast.ValueSpec), keepType[i], false, &ml)
+				}
+			} else {
+				var ml bool
+				for i, s := range d.Specs {
+					if i > 0 {
+						p.linebreak(p.fset.Position(s.Pos()).Line, 1, ignore, ml)
+					}
+					ml = false
+					p.spec(s, n, false, &ml)
 				}
-				ml = false
-				p.spec(s, len(d.Specs), false, &ml)
 			}
 			p.print(unindent, formfeed)
 			*multiLine = true
@@ -1303,7 +1392,7 @@ func (p *printer) nodeSize(n ast.Node, maxSize int) (size int) {
 	size = maxSize + 1 // assume n doesn't fit
 	p.nodeSizes[n] = size
 
-	// nodeSize computation must be indendent of particular
+	// nodeSize computation must be independent of particular
 	// style so that we always get the same decision; print
 	// in RawFormat
 	cfg := Config{Mode: RawFormat}
diff --git a/src/pkg/go/printer/performance_test.go b/src/pkg/go/printer/performance_test.go
new file mode 100644
index 000000000..31de0b7ad
--- /dev/null
+++ b/src/pkg/go/printer/performance_test.go
@@ -0,0 +1,62 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements a simple printer performance benchmark:
+// gotest -bench=BenchmarkPrint 
+
+package printer
+
+import (
+	"bytes"
+	"go/ast"
+	"go/parser"
+	"io"
+	"io/ioutil"
+	"log"
+	"testing"
+)
+
+
+var testfile *ast.File
+
+
+func testprint(out io.Writer, file *ast.File) {
+	if _, err := (&Config{TabIndent | UseSpaces, 8}).Fprint(out, fset, file); err != nil {
+		log.Fatalf("print error: %s", err)
+	}
+}
+
+
+// cannot initialize in init because (printer) Fprint launches goroutines.
+func initialize() {
+	const filename = "testdata/parser.go"
+
+	src, err := ioutil.ReadFile(filename)
+	if err != nil {
+		log.Fatalf("%s", err)
+	}
+
+	file, err := parser.ParseFile(fset, filename, src, parser.ParseComments)
+	if err != nil {
+		log.Fatalf("%s", err)
+	}
+
+	var buf bytes.Buffer
+	testprint(&buf, file)
+	if !bytes.Equal(buf.Bytes(), src) {
+		log.Fatalf("print error: %s not idempotent", filename)
+	}
+
+	testfile = file
+}
+
+
+func BenchmarkPrint(b *testing.B) {
+	if testfile == nil {
+		initialize()
+	}
+	for i := 0; i < b.N; i++ {
+		testprint(ioutil.Discard, testfile)
+	}
+}
diff --git a/src/pkg/go/printer/printer.go b/src/pkg/go/printer/printer.go
index 01ebf783c..40b15dd79 100644
--- a/src/pkg/go/printer/printer.go
+++ b/src/pkg/go/printer/printer.go
@@ -589,7 +589,7 @@ func (p *printer) writeCommentSuffix(needsLinebreak bool) (droppedFF bool) {
 			// ignore trailing whitespace
 			p.wsbuf[i] = ignore
 		case indent, unindent:
-			// don't loose indentation information
+			// don't lose indentation information
 		case newline, formfeed:
 			// if we need a line break, keep exactly one
 			// but remember if we dropped any formfeeds
diff --git a/src/pkg/go/printer/testdata/comments.golden b/src/pkg/go/printer/testdata/comments.golden
index a86d66174..b177c3571 100644
--- a/src/pkg/go/printer/testdata/comments.golden
+++ b/src/pkg/go/printer/testdata/comments.golden
@@ -22,7 +22,7 @@ const (
 	_	= iota + 10
 	_	// comments
 
-	_	= 10		// comment
+	_		= 10	// comment
 	_	T	= 20	// comment
 )
 
@@ -38,9 +38,9 @@ const (
 	_			// comment
 	_			// comment
 	_	= iota + 10
-	_	// comment
-	_	= 10
-	_	= 20		// comment
+	_		// comment
+	_		= 10
+	_		= 20	// comment
 	_	T	= 0	// comment
 )
 
@@ -436,7 +436,7 @@ func _() {
 
 
 // Comments immediately adjacent to punctuation (for which the go/printer
-// may obly have estimated position information) must remain after the punctuation.
+// may only have estimated position information) must remain after the punctuation.
 func _() {
 	_ = T{
 		1,	// comment after comma
diff --git a/src/pkg/go/printer/testdata/comments.input b/src/pkg/go/printer/testdata/comments.input
index 14cd4cf7a..2a9a86b68 100644
--- a/src/pkg/go/printer/testdata/comments.input
+++ b/src/pkg/go/printer/testdata/comments.input
@@ -434,7 +434,7 @@ func _() {
 
 
 // Comments immediately adjacent to punctuation (for which the go/printer
-// may obly have estimated position information) must remain after the punctuation.
+// may only have estimated position information) must remain after the punctuation.
 func _() {
 	_ = T{
 		1,    // comment after comma
diff --git a/src/pkg/go/printer/testdata/comments.x b/src/pkg/go/printer/testdata/comments.x
index 4d7a928ae..30a182f49 100644
--- a/src/pkg/go/printer/testdata/comments.x
+++ b/src/pkg/go/printer/testdata/comments.x
@@ -8,7 +8,7 @@ type SZ struct{}
 
 // The S0 struct; no field is exported.
 type S0 struct {
-	// contains unexported fields
+	// contains filtered or unexported fields
 }
 
 // The S1 struct; some fields are not exported.
@@ -16,7 +16,7 @@ type S1 struct {
 	S0
 	A, B, C	float	// 3 exported fields
 	D	int	// 2 unexported fields
-	// contains unexported fields
+	// contains filtered or unexported fields
 }
 
 // The S2 struct; all fields are exported.
@@ -30,14 +30,14 @@ type SZ interface{}
 
 // The I0 interface; no method is exported.
 type I0 interface {
-	// contains unexported methods
+	// contains filtered or unexported methods
 }
 
 // The I1 interface; some methods are not exported.
 type I1 interface {
 	I0
 	F(x float) float	// exported methods
-	// contains unexported methods
+	// contains filtered or unexported methods
 }
 
 // The I2 interface; all methods are exported.
@@ -53,5 +53,5 @@ type S3 struct {
 	F1	int	// line comment for F1
 	// lead comment for F2
 	F2	int	// line comment for F2
-	// contains unexported fields
+	// contains filtered or unexported fields
 }
diff --git a/src/pkg/go/printer/testdata/declarations.golden b/src/pkg/go/printer/testdata/declarations.golden
index c1b255842..fac72f651 100644
--- a/src/pkg/go/printer/testdata/declarations.golden
+++ b/src/pkg/go/printer/testdata/declarations.golden
@@ -160,7 +160,6 @@ bar`
 
 
 func _() {
-	// the following decls need a semicolon at the end
 	type _ int
 	type _ *int
 	type _ []int
@@ -175,7 +174,6 @@ func _() {
 	var _ chan int
 	var _ func() int
 
-	// the following decls don't need a semicolon at the end
 	type _ struct{}
 	type _ *struct{}
 	type _ []struct{}
@@ -331,11 +329,11 @@ func _() {
 	)
 	// some entries have a type
 	const (
-		xxxxxx		= 1
-		x		= 2
-		xxx		= 3
+		xxxxxx			= 1
+		x			= 2
+		xxx			= 3
 		yyyyyyyy	float	= iota
-		yyyy		= "bar"
+		yyyy			= "bar"
 		yyy
 		yy	= 2
 	)
@@ -365,7 +363,7 @@ func _() {
 		xxx		string
 		yyyyyyyy	int	= 1234
 		y		float	= 3.14
-		yyyy		= "bar"
+		yyyy			= "bar"
 		yyy		string	= "foo"
 	)
 	// mixed entries - all comments should be aligned
@@ -373,7 +371,7 @@ func _() {
 		a, b, c			int
 		x			= 10
 		d			int			// comment
-		y			= 20			// comment
+		y				= 20		// comment
 		f, ff, fff, ffff	int	= 0, 1, 2, 3	// comment
 	)
 	// respect original line breaks
@@ -401,6 +399,33 @@ func _() {
 	)
 }
 
+// alignment of "=" in consecutive lines (extended example from issue 1414)
+const (
+	umax	uint	= ^uint(0)		// maximum value for a uint
+	bpu		= 1 << (5 + umax>>63)	// bits per uint
+	foo
+	bar	= -1
+)
+
+// typical enum
+const (
+	a	MyType	= iota
+	abcd
+	b
+	c
+	def
+)
+
+// excerpt from godoc.go
+var (
+	goroot		= flag.String("goroot", runtime.GOROOT(), "Go root directory")
+	testDir		= flag.String("testdir", "", "Go root subdirectory - for testing only (faster startups)")
+	pkgPath		= flag.String("path", "", "additional package directories (colon-separated)")
+	filter		= flag.String("filter", "", "filter file containing permitted package directory paths")
+	filterMin	= flag.Int("filter_minutes", 0, "filter file update interval in minutes; disabled if <= 0")
+	filterDelay	delayTime	// actual filter update interval in minutes; usually filterDelay == filterMin, but filterDelay may back off exponentially
+)
+
 
 // formatting of structs
 type _ struct{}
diff --git a/src/pkg/go/printer/testdata/declarations.input b/src/pkg/go/printer/testdata/declarations.input
index c8b37e12b..c6134096b 100644
--- a/src/pkg/go/printer/testdata/declarations.input
+++ b/src/pkg/go/printer/testdata/declarations.input
@@ -159,7 +159,6 @@ bar`
 
 
 func _() {
-	// the following decls need a semicolon at the end
 	type _ int
 	type _ *int
 	type _ []int
@@ -174,7 +173,6 @@ func _() {
 	var _ chan int
 	var _ func() int
 
-	// the following decls don't need a semicolon at the end
 	type _ struct{}
 	type _ *struct{}
 	type _ []struct{}
@@ -400,6 +398,33 @@ func _() {
 	)
 }
 
+// alignment of "=" in consecutive lines (extended example from issue 1414)
+const (
+	umax uint                  = ^uint(0) // maximum value for a uint
+	bpu  = 1 << (5 + umax>>63)            // bits per uint
+	foo
+	bar  = -1
+)
+
+// typical enum
+const (
+	a MyType = iota
+	abcd
+	b
+	c
+	def
+)
+
+// excerpt from godoc.go
+var (
+	goroot = flag.String("goroot", runtime.GOROOT(), "Go root directory")
+	testDir = flag.String("testdir", "", "Go root subdirectory - for testing only (faster startups)")
+	pkgPath = flag.String("path", "", "additional package directories (colon-separated)")
+	filter = flag.String("filter", "", "filter file containing permitted package directory paths")
+	filterMin = flag.Int("filter_minutes", 0, "filter file update interval in minutes; disabled if <= 0")
+	filterDelay delayTime // actual filter update interval in minutes; usually filterDelay == filterMin, but filterDelay may back off exponentially
+)
+
 
 // formatting of structs
 type _ struct{}
diff --git a/src/pkg/go/printer/testdata/expressions.golden b/src/pkg/go/printer/testdata/expressions.golden
index c1a7e970b..a5e2fdc3b 100644
--- a/src/pkg/go/printer/testdata/expressions.golden
+++ b/src/pkg/go/printer/testdata/expressions.golden
@@ -94,30 +94,49 @@ func _() {
 	_ = under_bar - 1
 	_ = Open(dpath+"/file", O_WRONLY|O_CREAT, 0666)
 	_ = int(c0&_Mask4)<<18 | int(c1&_Maskx)<<12 | int(c2&_Maskx)<<6 | int(c3&_Maskx)
-}
-
 
-func _() {
+	// the parser does not restrict expressions that may appear as statements
+	true
+	42
+	"foo"
+	x
+	(x)
 	a + b
 	a + b + c
-	a + b*c
 	a + (b * c)
-	(a + b) * c
-	a + (b * c * d)
-	a + (b*c + d)
+	a + (b / c)
+	1 + a
+	a + 1
+	s[a]
+	x << 1
+	(s[0] << 1) & 0xf
+	"foo" + s
+	x == y
+	x < y || z > 42
+}
+
+
+func _() {
+	_ = a + b
+	_ = a + b + c
+	_ = a + b*c
+	_ = a + (b * c)
+	_ = (a + b) * c
+	_ = a + (b * c * d)
+	_ = a + (b*c + d)
 
-	1 << x
-	-1 << x
-	1<<x - 1
-	-1<<x - 1
+	_ = 1 << x
+	_ = -1 << x
+	_ = 1<<x - 1
+	_ = -1<<x - 1
 
-	f(a + b)
-	f(a + b + c)
-	f(a + b*c)
-	f(a + (b * c))
-	f(1<<x-1, 1<<x-2)
+	_ = f(a + b)
+	_ = f(a + b + c)
+	_ = f(a + b*c)
+	_ = f(a + (b * c))
+	_ = f(1<<x-1, 1<<x-2)
 
-	1<<d.logWindowSize - 1
+	_ = 1<<d.logWindowSize - 1
 
 	buf = make(x, 2*cap(b.buf)+n)
 
@@ -131,7 +150,7 @@ func _() {
 	signed += ' ' * 8
 	tw.octal(header[148:155], chksum)
 
-	x > 0 && i >= 0
+	_ = x > 0 && i >= 0
 
 	x1, x0 := x>>w2, x&m2
 	z0 = t1<<w2 + t0
@@ -141,31 +160,31 @@ func _() {
 	x1 = (x1 << z) | (x0 >> (uint(w) - z))
 	x1 = x1<<z | x0>>(uint(w)-z)
 
-	buf[0 : len(buf)+1]
-	buf[0 : n+1]
+	_ = buf[0 : len(buf)+1]
+	_ = buf[0 : n+1]
 
 	a, b = b, a
 	a = b + c
 	a = b*c + d
-	a*b + c
-	a - b - c
-	a - (b - c)
-	a - b*c
-	a - (b * c)
-	a * b / c
-	a / *b
-	x[a|^b]
-	x[a / *b]
-	a & ^b
-	a + +b
-	a - -b
-	x[a*-b]
-	x[a + +b]
-	x ^ y ^ z
-	b[a>>24] ^ b[(a>>16)&0xFF] ^ b[(a>>8)&0xFF] ^ b[a&0xFF]
-	len(longVariableName) * 2
-
-	token(matchType + xlength<<lengthShift + xoffset)
+	_ = a*b + c
+	_ = a - b - c
+	_ = a - (b - c)
+	_ = a - b*c
+	_ = a - (b * c)
+	_ = a * b / c
+	_ = a / *b
+	_ = x[a|^b]
+	_ = x[a / *b]
+	_ = a & ^b
+	_ = a + +b
+	_ = a - -b
+	_ = x[a*-b]
+	_ = x[a + +b]
+	_ = x ^ y ^ z
+	_ = b[a>>24] ^ b[(a>>16)&0xFF] ^ b[(a>>8)&0xFF] ^ b[a&0xFF]
+	_ = len(longVariableName) * 2
+
+	_ = token(matchType + xlength<<lengthShift + xoffset)
 }
 
 
@@ -625,7 +644,7 @@ func _() {
 func f() {
 	// os.Open parameters should remain on two lines
 	if writer, err = os.Open(outfile, s.O_WRONLY|os.O_CREATE|
-		os.O_TRUNC,0666); err != nil {
+		os.O_TRUNC, 0666); err != nil {
 		log.Fatal(err)
 	}
 }
diff --git a/src/pkg/go/printer/testdata/expressions.input b/src/pkg/go/printer/testdata/expressions.input
index b87381198..d11314983 100644
--- a/src/pkg/go/printer/testdata/expressions.input
+++ b/src/pkg/go/printer/testdata/expressions.input
@@ -94,30 +94,49 @@ func _() {
 	_ = under_bar-1
 	_ = Open(dpath + "/file", O_WRONLY | O_CREAT, 0666)
 	_ = int(c0&_Mask4)<<18 | int(c1&_Maskx)<<12 | int(c2&_Maskx)<<6 | int(c3&_Maskx)
-}
-
 
-func _() {
+	// the parser does not restrict expressions that may appear as statements
+	true
+	42
+	"foo"
+	x
+	(x)
 	a+b
 	a+b+c
-	a+b*c
 	a+(b*c)
-	(a+b)*c
-	a+(b*c*d)
-	a+(b*c+d)
+	a+(b/c)
+	1+a
+	a+1
+	s[a]
+	x<<1
+	(s[0]<<1)&0xf
+	"foo"+s
+	x == y
+	x < y || z > 42
+}
 
-	1<<x
-	-1<<x
-	1<<x-1
-	-1<<x-1
 
-	f(a+b)
-	f(a+b+c)
-	f(a+b*c)
-	f(a+(b*c))
-	f(1<<x-1, 1<<x-2)
+func _() {
+	_ = a+b
+	_ = a+b+c
+	_ = a+b*c
+	_ = a+(b*c)
+	_ = (a+b)*c
+	_ = a+(b*c*d)
+	_ = a+(b*c+d)
+
+	_ = 1<<x
+	_ = -1<<x
+	_ = 1<<x-1
+	_ = -1<<x-1
 
-	1<<d.logWindowSize-1
+	_ = f(a+b)
+	_ = f(a+b+c)
+	_ = f(a+b*c)
+	_ = f(a+(b*c))
+	_ = f(1<<x-1, 1<<x-2)
+
+	_ = 1<<d.logWindowSize-1
 
 	buf = make(x, 2*cap(b.buf) + n)
 
@@ -131,7 +150,7 @@ func _() {
 	signed += ' '*8
 	tw.octal(header[148:155], chksum)
 
-	x > 0 && i >= 0
+	_ = x > 0 && i >= 0
 
 	x1, x0 := x>>w2, x&m2
 	z0 = t1<<w2+t0
@@ -141,31 +160,31 @@ func _() {
 	x1 = (x1<<z)|(x0>>(uint(w)-z))
 	x1 = x1<<z | x0>>(uint(w)-z)
 
-	buf[0:len(buf)+1]
-	buf[0:n+1]
+	_ = buf[0:len(buf)+1]
+	_ = buf[0:n+1]
 
 	a,b = b,a
 	a = b+c
 	a = b*c+d
-	a*b+c
-	a-b-c
-	a-(b-c)
-	a-b*c
-	a-(b*c)
-	a*b/c
-	a/ *b
-	x[a|^b]
-	x[a/ *b]
-	a& ^b
-	a+ +b
-	a- -b
-	x[a*-b]
-	x[a+ +b]
-	x^y^z
-	b[a>>24] ^ b[(a>>16)&0xFF] ^ b[(a>>8)&0xFF] ^ b[a&0xFF]
-	len(longVariableName)*2
-
-	token(matchType + xlength<<lengthShift + xoffset)
+	_ = a*b+c
+	_ = a-b-c
+	_ = a-(b-c)
+	_ = a-b*c
+	_ = a-(b*c)
+	_ = a*b/c
+	_ = a/ *b
+	_ = x[a|^b]
+	_ = x[a/ *b]
+	_ = a& ^b
+	_ = a+ +b
+	_ = a- -b
+	_ = x[a*-b]
+	_ = x[a+ +b]
+	_ = x^y^z
+	_ = b[a>>24] ^ b[(a>>16)&0xFF] ^ b[(a>>8)&0xFF] ^ b[a&0xFF]
+	_ = len(longVariableName)*2
+
+	_ = token(matchType + xlength<<lengthShift + xoffset)
 }
 
 
diff --git a/src/pkg/go/printer/testdata/expressions.raw b/src/pkg/go/printer/testdata/expressions.raw
index 735cd943e..308d9edff 100644
--- a/src/pkg/go/printer/testdata/expressions.raw
+++ b/src/pkg/go/printer/testdata/expressions.raw
@@ -94,30 +94,49 @@ func _() {
 	_ = under_bar - 1
 	_ = Open(dpath+"/file", O_WRONLY|O_CREAT, 0666)
 	_ = int(c0&_Mask4)<<18 | int(c1&_Maskx)<<12 | int(c2&_Maskx)<<6 | int(c3&_Maskx)
-}
-
 
-func _() {
+	// the parser does not restrict expressions that may appear as statements
+	true
+	42
+	"foo"
+	x
+	(x)
 	a + b
 	a + b + c
-	a + b*c
 	a + (b * c)
-	(a + b) * c
-	a + (b * c * d)
-	a + (b*c + d)
+	a + (b / c)
+	1 + a
+	a + 1
+	s[a]
+	x << 1
+	(s[0] << 1) & 0xf
+	"foo" + s
+	x == y
+	x < y || z > 42
+}
+
+
+func _() {
+	_ = a + b
+	_ = a + b + c
+	_ = a + b*c
+	_ = a + (b * c)
+	_ = (a + b) * c
+	_ = a + (b * c * d)
+	_ = a + (b*c + d)
 
-	1 << x
-	-1 << x
-	1<<x - 1
-	-1<<x - 1
+	_ = 1 << x
+	_ = -1 << x
+	_ = 1<<x - 1
+	_ = -1<<x - 1
 
-	f(a + b)
-	f(a + b + c)
-	f(a + b*c)
-	f(a + (b * c))
-	f(1<<x-1, 1<<x-2)
+	_ = f(a + b)
+	_ = f(a + b + c)
+	_ = f(a + b*c)
+	_ = f(a + (b * c))
+	_ = f(1<<x-1, 1<<x-2)
 
-	1<<d.logWindowSize - 1
+	_ = 1<<d.logWindowSize - 1
 
 	buf = make(x, 2*cap(b.buf)+n)
 
@@ -131,7 +150,7 @@ func _() {
 	signed += ' ' * 8
 	tw.octal(header[148:155], chksum)
 
-	x > 0 && i >= 0
+	_ = x > 0 && i >= 0
 
 	x1, x0 := x>>w2, x&m2
 	z0 = t1<<w2 + t0
@@ -141,31 +160,31 @@ func _() {
 	x1 = (x1 << z) | (x0 >> (uint(w) - z))
 	x1 = x1<<z | x0>>(uint(w)-z)
 
-	buf[0 : len(buf)+1]
-	buf[0 : n+1]
+	_ = buf[0 : len(buf)+1]
+	_ = buf[0 : n+1]
 
 	a, b = b, a
 	a = b + c
 	a = b*c + d
-	a*b + c
-	a - b - c
-	a - (b - c)
-	a - b*c
-	a - (b * c)
-	a * b / c
-	a / *b
-	x[a|^b]
-	x[a / *b]
-	a & ^b
-	a + +b
-	a - -b
-	x[a*-b]
-	x[a + +b]
-	x ^ y ^ z
-	b[a>>24] ^ b[(a>>16)&0xFF] ^ b[(a>>8)&0xFF] ^ b[a&0xFF]
-	len(longVariableName) * 2
-
-	token(matchType + xlength<<lengthShift + xoffset)
+	_ = a*b + c
+	_ = a - b - c
+	_ = a - (b - c)
+	_ = a - b*c
+	_ = a - (b * c)
+	_ = a * b / c
+	_ = a / *b
+	_ = x[a|^b]
+	_ = x[a / *b]
+	_ = a & ^b
+	_ = a + +b
+	_ = a - -b
+	_ = x[a*-b]
+	_ = x[a + +b]
+	_ = x ^ y ^ z
+	_ = b[a>>24] ^ b[(a>>16)&0xFF] ^ b[(a>>8)&0xFF] ^ b[a&0xFF]
+	_ = len(longVariableName) * 2
+
+	_ = token(matchType + xlength<<lengthShift + xoffset)
 }
 
 
@@ -625,7 +644,7 @@ func _() {
 func f() {
 	// os.Open parameters should remain on two lines
 	if writer, err = os.Open(outfile, s.O_WRONLY|os.O_CREATE|
-		os.O_TRUNC,0666); err != nil {
+		os.O_TRUNC, 0666); err != nil {
 		log.Fatal(err)
 	}
 }
diff --git a/src/pkg/go/printer/testdata/parser.go b/src/pkg/go/printer/testdata/parser.go
new file mode 100644
index 000000000..5c57e41d1
--- /dev/null
+++ b/src/pkg/go/printer/testdata/parser.go
@@ -0,0 +1,2252 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package parser implements a parser for Go source files. Input may be
+// provided in a variety of forms (see the various Parse* functions); the
+// output is an abstract syntax tree (AST) representing the Go source. The
+// parser is invoked through one of the Parse* functions.
+//
+package parser
+
+import (
+	"fmt"
+	"go/ast"
+	"go/scanner"
+	"go/token"
+)
+
+
+// The mode parameter to the Parse* functions is a set of flags (or 0).
+// They control the amount of source code parsed and other optional
+// parser functionality.
+//
+const (
+	PackageClauseOnly uint = 1 << iota // parsing stops after package clause
+	ImportsOnly                        // parsing stops after import declarations
+	ParseComments                      // parse comments and add them to AST
+	Trace                              // print a trace of parsed productions
+	DeclarationErrors                  // report declaration errors
+)
+
+
+// The parser structure holds the parser's internal state.
+type parser struct {
+	file *token.File
+	scanner.ErrorVector
+	scanner scanner.Scanner
+
+	// Tracing/debugging
+	mode   uint // parsing mode
+	trace  bool // == (mode & Trace != 0)
+	indent uint // indentation used for tracing output
+
+	// Comments
+	comments    []*ast.CommentGroup
+	leadComment *ast.CommentGroup // last lead comment
+	lineComment *ast.CommentGroup // last line comment
+
+	// Next token
+	pos token.Pos   // token position
+	tok token.Token // one token look-ahead
+	lit string      // token literal
+
+	// Non-syntactic parser control
+	exprLev int // < 0: in control clause, >= 0: in expression
+
+	// Ordinary identifer scopes
+	pkgScope   *ast.Scope        // pkgScope.Outer == nil
+	topScope   *ast.Scope        // top-most scope; may be pkgScope
+	unresolved []*ast.Ident      // unresolved identifiers
+	imports    []*ast.ImportSpec // list of imports
+
+	// Label scope
+	// (maintained by open/close LabelScope)
+	labelScope  *ast.Scope     // label scope for current function
+	targetStack [][]*ast.Ident // stack of unresolved labels
+}
+
+
+// scannerMode returns the scanner mode bits given the parser's mode bits.
+func scannerMode(mode uint) uint {
+	var m uint = scanner.InsertSemis
+	if mode&ParseComments != 0 {
+		m |= scanner.ScanComments
+	}
+	return m
+}
+
+
+func (p *parser) init(fset *token.FileSet, filename string, src []byte, mode uint) {
+	p.file = fset.AddFile(filename, fset.Base(), len(src))
+	p.scanner.Init(p.file, src, p, scannerMode(mode))
+
+	p.mode = mode
+	p.trace = mode&Trace != 0 // for convenience (p.trace is used frequently)
+
+	p.next()
+
+	// set up the pkgScope here (as opposed to in parseFile) because
+	// there are other parser entry points (ParseExpr, etc.)
+	p.openScope()
+	p.pkgScope = p.topScope
+
+	// for the same reason, set up a label scope
+	p.openLabelScope()
+}
+
+
+// ----------------------------------------------------------------------------
+// Scoping support
+
+func (p *parser) openScope() {
+	p.topScope = ast.NewScope(p.topScope)
+}
+
+
+func (p *parser) closeScope() {
+	p.topScope = p.topScope.Outer
+}
+
+
+func (p *parser) openLabelScope() {
+	p.labelScope = ast.NewScope(p.labelScope)
+	p.targetStack = append(p.targetStack, nil)
+}
+
+
+func (p *parser) closeLabelScope() {
+	// resolve labels
+	n := len(p.targetStack) - 1
+	scope := p.labelScope
+	for _, ident := range p.targetStack[n] {
+		ident.Obj = scope.Lookup(ident.Name)
+		if ident.Obj == nil && p.mode&DeclarationErrors != 0 {
+			p.error(ident.Pos(), fmt.Sprintf("label %s undefined", ident.Name))
+		}
+	}
+	// pop label scope
+	p.targetStack = p.targetStack[0:n]
+	p.labelScope = p.labelScope.Outer
+}
+
+
+func (p *parser) declare(decl interface{}, scope *ast.Scope, kind ast.ObjKind, idents ...*ast.Ident) {
+	for _, ident := range idents {
+		assert(ident.Obj == nil, "identifier already declared or resolved")
+		if ident.Name != "_" {
+			obj := ast.NewObj(kind, ident.Name)
+			// remember the corresponding declaration for redeclaration
+			// errors and global variable resolution/typechecking phase
+			obj.Decl = decl
+			if alt := scope.Insert(obj); alt != nil && p.mode&DeclarationErrors != 0 {
+				prevDecl := ""
+				if pos := alt.Pos(); pos.IsValid() {
+					prevDecl = fmt.Sprintf("\n\tprevious declaration at %s", p.file.Position(pos))
+				}
+				p.error(ident.Pos(), fmt.Sprintf("%s redeclared in this block%s", ident.Name, prevDecl))
+			}
+			ident.Obj = obj
+		}
+	}
+}
+
+
+func (p *parser) shortVarDecl(idents []*ast.Ident) {
+	// Go spec: A short variable declaration may redeclare variables
+	// provided they were originally declared in the same block with
+	// the same type, and at least one of the non-blank variables is new.
+	n := 0 // number of new variables
+	for _, ident := range idents {
+		assert(ident.Obj == nil, "identifier already declared or resolved")
+		if ident.Name != "_" {
+			obj := ast.NewObj(ast.Var, ident.Name)
+			// short var declarations cannot have redeclaration errors
+			// and are not global => no need to remember the respective
+			// declaration
+			alt := p.topScope.Insert(obj)
+			if alt == nil {
+				n++ // new declaration
+				alt = obj
+			}
+			ident.Obj = alt
+		}
+	}
+	if n == 0 && p.mode&DeclarationErrors != 0 {
+		p.error(idents[0].Pos(), "no new variables on left side of :=")
+	}
+}
+
+
+// The unresolved object is a sentinel to mark identifiers that have been added
+// to the list of unresolved identifiers. The sentinel is only used for verifying
+// internal consistency.
+var unresolved = new(ast.Object)
+
+
+func (p *parser) resolve(x ast.Expr) {
+	// nothing to do if x is not an identifier or the blank identifier
+	ident, _ := x.(*ast.Ident)
+	if ident == nil {
+		return
+	}
+	assert(ident.Obj == nil, "identifier already declared or resolved")
+	if ident.Name == "_" {
+		return
+	}
+	// try to resolve the identifier
+	for s := p.topScope; s != nil; s = s.Outer {
+		if obj := s.Lookup(ident.Name); obj != nil {
+			ident.Obj = obj
+			return
+		}
+	}
+	// all local scopes are known, so any unresolved identifier
+	// must be found either in the file scope, package scope
+	// (perhaps in another file), or universe scope --- collect
+	// them so that they can be resolved later
+	ident.Obj = unresolved
+	p.unresolved = append(p.unresolved, ident)
+}
+
+
+// ----------------------------------------------------------------------------
+// Parsing support
+
+func (p *parser) printTrace(a ...interface{}) {
+	const dots = ". . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . " +
+		". . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . "
+	const n = uint(len(dots))
+	pos := p.file.Position(p.pos)
+	fmt.Printf("%5d:%3d: ", pos.Line, pos.Column)
+	i := 2 * p.indent
+	for ; i > n; i -= n {
+		fmt.Print(dots)
+	}
+	fmt.Print(dots[0:i])
+	fmt.Println(a...)
+}
+
+
+func trace(p *parser, msg string) *parser {
+	p.printTrace(msg, "(")
+	p.indent++
+	return p
+}
+
+
+// Usage pattern: defer un(trace(p, "..."));
+func un(p *parser) {
+	p.indent--
+	p.printTrace(")")
+}
+
+
+// Advance to the next token.
+func (p *parser) next0() {
+	// Because of one-token look-ahead, print the previous token
+	// when tracing as it provides a more readable output. The
+	// very first token (!p.pos.IsValid()) is not initialized
+	// (it is token.ILLEGAL), so don't print it .
+	if p.trace && p.pos.IsValid() {
+		s := p.tok.String()
+		switch {
+		case p.tok.IsLiteral():
+			p.printTrace(s, p.lit)
+		case p.tok.IsOperator(), p.tok.IsKeyword():
+			p.printTrace("\"" + s + "\"")
+		default:
+			p.printTrace(s)
+		}
+	}
+
+	p.pos, p.tok, p.lit = p.scanner.Scan()
+}
+
+// Consume a comment and return it and the line on which it ends.
+func (p *parser) consumeComment() (comment *ast.Comment, endline int) {
+	// /*-style comments may end on a different line than where they start.
+	// Scan the comment for '\n' chars and adjust endline accordingly.
+	endline = p.file.Line(p.pos)
+	if p.lit[1] == '*' {
+		// don't use range here - no need to decode Unicode code points
+		for i := 0; i < len(p.lit); i++ {
+			if p.lit[i] == '\n' {
+				endline++
+			}
+		}
+	}
+
+	comment = &ast.Comment{p.pos, p.lit}
+	p.next0()
+
+	return
+}
+
+
+// Consume a group of adjacent comments, add it to the parser's
+// comments list, and return it together with the line at which
+// the last comment in the group ends. An empty line or non-comment
+// token terminates a comment group.
+//
+func (p *parser) consumeCommentGroup() (comments *ast.CommentGroup, endline int) {
+	var list []*ast.Comment
+	endline = p.file.Line(p.pos)
+	for p.tok == token.COMMENT && endline+1 >= p.file.Line(p.pos) {
+		var comment *ast.Comment
+		comment, endline = p.consumeComment()
+		list = append(list, comment)
+	}
+
+	// add comment group to the comments list
+	comments = &ast.CommentGroup{list}
+	p.comments = append(p.comments, comments)
+
+	return
+}
+
+
+// Advance to the next non-comment token. In the process, collect
+// any comment groups encountered, and remember the last lead and
+// and line comments.
+//
+// A lead comment is a comment group that starts and ends in a
+// line without any other tokens and that is followed by a non-comment
+// token on the line immediately after the comment group.
+//
+// A line comment is a comment group that follows a non-comment
+// token on the same line, and that has no tokens after it on the line
+// where it ends.
+//
+// Lead and line comments may be considered documentation that is
+// stored in the AST.
+//
+func (p *parser) next() {
+	p.leadComment = nil
+	p.lineComment = nil
+	line := p.file.Line(p.pos) // current line
+	p.next0()
+
+	if p.tok == token.COMMENT {
+		var comment *ast.CommentGroup
+		var endline int
+
+		if p.file.Line(p.pos) == line {
+			// The comment is on same line as the previous token; it
+			// cannot be a lead comment but may be a line comment.
+			comment, endline = p.consumeCommentGroup()
+			if p.file.Line(p.pos) != endline {
+				// The next token is on a different line, thus
+				// the last comment group is a line comment.
+				p.lineComment = comment
+			}
+		}
+
+		// consume successor comments, if any
+		endline = -1
+		for p.tok == token.COMMENT {
+			comment, endline = p.consumeCommentGroup()
+		}
+
+		if endline+1 == p.file.Line(p.pos) {
+			// The next token is following on the line immediately after the
+			// comment group, thus the last comment group is a lead comment.
+			p.leadComment = comment
+		}
+	}
+}
+
+
+func (p *parser) error(pos token.Pos, msg string) {
+	p.Error(p.file.Position(pos), msg)
+}
+
+
+func (p *parser) errorExpected(pos token.Pos, msg string) {
+	msg = "expected " + msg
+	if pos == p.pos {
+		// the error happened at the current position;
+		// make the error message more specific
+		if p.tok == token.SEMICOLON && p.lit[0] == '\n' {
+			msg += ", found newline"
+		} else {
+			msg += ", found '" + p.tok.String() + "'"
+			if p.tok.IsLiteral() {
+				msg += " " + p.lit
+			}
+		}
+	}
+	p.error(pos, msg)
+}
+
+
+func (p *parser) expect(tok token.Token) token.Pos {
+	pos := p.pos
+	if p.tok != tok {
+		p.errorExpected(pos, "'"+tok.String()+"'")
+	}
+	p.next() // make progress
+	return pos
+}
+
+
+func (p *parser) expectSemi() {
+	if p.tok != token.RPAREN && p.tok != token.RBRACE {
+		p.expect(token.SEMICOLON)
+	}
+}
+
+
+func assert(cond bool, msg string) {
+	if !cond {
+		panic("go/parser internal error: " + msg)
+	}
+}
+
+
+// ----------------------------------------------------------------------------
+// Identifiers
+
+func (p *parser) parseIdent() *ast.Ident {
+	pos := p.pos
+	name := "_"
+	if p.tok == token.IDENT {
+		name = p.lit
+		p.next()
+	} else {
+		p.expect(token.IDENT) // use expect() error handling
+	}
+	return &ast.Ident{pos, name, nil}
+}
+
+
+func (p *parser) parseIdentList() (list []*ast.Ident) {
+	if p.trace {
+		defer un(trace(p, "IdentList"))
+	}
+
+	list = append(list, p.parseIdent())
+	for p.tok == token.COMMA {
+		p.next()
+		list = append(list, p.parseIdent())
+	}
+
+	return
+}
+
+
+// ----------------------------------------------------------------------------
+// Common productions
+
+// If lhs is set, result list elements which are identifiers are not resolved.
+func (p *parser) parseExprList(lhs bool) (list []ast.Expr) {
+	if p.trace {
+		defer un(trace(p, "ExpressionList"))
+	}
+
+	list = append(list, p.parseExpr(lhs))
+	for p.tok == token.COMMA {
+		p.next()
+		list = append(list, p.parseExpr(lhs))
+	}
+
+	return
+}
+
+
+func (p *parser) parseLhsList() []ast.Expr {
+	list := p.parseExprList(true)
+	switch p.tok {
+	case token.DEFINE:
+		// lhs of a short variable declaration
+		p.shortVarDecl(p.makeIdentList(list))
+	case token.COLON:
+		// lhs of a label declaration or a communication clause of a select
+		// statement (parseLhsList is not called when parsing the case clause
+		// of a switch statement):
+		// - labels are declared by the caller of parseLhsList
+		// - for communication clauses, if there is a stand-alone identifier
+		//   followed by a colon, we have a syntax error; there is no need
+		//   to resolve the identifier in that case
+	default:
+		// identifiers must be declared elsewhere
+		for _, x := range list {
+			p.resolve(x)
+		}
+	}
+	return list
+}
+
+
+func (p *parser) parseRhsList() []ast.Expr {
+	return p.parseExprList(false)
+}
+
+
+// ----------------------------------------------------------------------------
+// Types
+
+func (p *parser) parseType() ast.Expr {
+	if p.trace {
+		defer un(trace(p, "Type"))
+	}
+
+	typ := p.tryType()
+
+	if typ == nil {
+		pos := p.pos
+		p.errorExpected(pos, "type")
+		p.next() // make progress
+		return &ast.BadExpr{pos, p.pos}
+	}
+
+	return typ
+}
+
+
+// If the result is an identifier, it is not resolved.
+func (p *parser) parseTypeName() ast.Expr {
+	if p.trace {
+		defer un(trace(p, "TypeName"))
+	}
+
+	ident := p.parseIdent()
+	// don't resolve ident yet - it may be a parameter or field name
+
+	if p.tok == token.PERIOD {
+		// ident is a package name
+		p.next()
+		p.resolve(ident)
+		sel := p.parseIdent()
+		return &ast.SelectorExpr{ident, sel}
+	}
+
+	return ident
+}
+
+
+func (p *parser) parseArrayType(ellipsisOk bool) ast.Expr {
+	if p.trace {
+		defer un(trace(p, "ArrayType"))
+	}
+
+	lbrack := p.expect(token.LBRACK)
+	var len ast.Expr
+	if ellipsisOk && p.tok == token.ELLIPSIS {
+		len = &ast.Ellipsis{p.pos, nil}
+		p.next()
+	} else if p.tok != token.RBRACK {
+		len = p.parseRhs()
+	}
+	p.expect(token.RBRACK)
+	elt := p.parseType()
+
+	return &ast.ArrayType{lbrack, len, elt}
+}
+
+
+func (p *parser) makeIdentList(list []ast.Expr) []*ast.Ident {
+	idents := make([]*ast.Ident, len(list))
+	for i, x := range list {
+		ident, isIdent := x.(*ast.Ident)
+		if !isIdent {
+			pos := x.(ast.Expr).Pos()
+			p.errorExpected(pos, "identifier")
+			ident = &ast.Ident{pos, "_", nil}
+		}
+		idents[i] = ident
+	}
+	return idents
+}
+
+
+func (p *parser) parseFieldDecl(scope *ast.Scope) *ast.Field {
+	if p.trace {
+		defer un(trace(p, "FieldDecl"))
+	}
+
+	doc := p.leadComment
+
+	// fields
+	list, typ := p.parseVarList(false)
+
+	// optional tag
+	var tag *ast.BasicLit
+	if p.tok == token.STRING {
+		tag = &ast.BasicLit{p.pos, p.tok, p.lit}
+		p.next()
+	}
+
+	// analyze case
+	var idents []*ast.Ident
+	if typ != nil {
+		// IdentifierList Type
+		idents = p.makeIdentList(list)
+	} else {
+		// ["*"] TypeName (AnonymousField)
+		typ = list[0] // we always have at least one element
+		p.resolve(typ)
+		if n := len(list); n > 1 || !isTypeName(deref(typ)) {
+			pos := typ.Pos()
+			p.errorExpected(pos, "anonymous field")
+			typ = &ast.BadExpr{pos, list[n-1].End()}
+		}
+	}
+
+	p.expectSemi() // call before accessing p.linecomment
+
+	field := &ast.Field{doc, idents, typ, tag, p.lineComment}
+	p.declare(field, scope, ast.Var, idents...)
+
+	return field
+}
+
+
+func (p *parser) parseStructType() *ast.StructType {
+	if p.trace {
+		defer un(trace(p, "StructType"))
+	}
+
+	pos := p.expect(token.STRUCT)
+	lbrace := p.expect(token.LBRACE)
+	scope := ast.NewScope(nil) // struct scope
+	var list []*ast.Field
+	for p.tok == token.IDENT || p.tok == token.MUL || p.tok == token.LPAREN {
+		// a field declaration cannot start with a '(' but we accept
+		// it here for more robust parsing and better error messages
+		// (parseFieldDecl will check and complain if necessary)
+		list = append(list, p.parseFieldDecl(scope))
+	}
+	rbrace := p.expect(token.RBRACE)
+
+	// TODO(gri): store struct scope in AST
+	return &ast.StructType{pos, &ast.FieldList{lbrace, list, rbrace}, false}
+}
+
+
+func (p *parser) parsePointerType() *ast.StarExpr {
+	if p.trace {
+		defer un(trace(p, "PointerType"))
+	}
+
+	star := p.expect(token.MUL)
+	base := p.parseType()
+
+	return &ast.StarExpr{star, base}
+}
+
+
+func (p *parser) tryVarType(isParam bool) ast.Expr {
+	if isParam && p.tok == token.ELLIPSIS {
+		pos := p.pos
+		p.next()
+		typ := p.tryIdentOrType(isParam) // don't use parseType so we can provide better error message
+		if typ == nil {
+			p.error(pos, "'...' parameter is missing type")
+			typ = &ast.BadExpr{pos, p.pos}
+		}
+		if p.tok != token.RPAREN {
+			p.error(pos, "can use '...' with last parameter type only")
+		}
+		return &ast.Ellipsis{pos, typ}
+	}
+	return p.tryIdentOrType(false)
+}
+
+
+func (p *parser) parseVarType(isParam bool) ast.Expr {
+	typ := p.tryVarType(isParam)
+	if typ == nil {
+		pos := p.pos
+		p.errorExpected(pos, "type")
+		p.next() // make progress
+		typ = &ast.BadExpr{pos, p.pos}
+	}
+	return typ
+}
+
+
+func (p *parser) parseVarList(isParam bool) (list []ast.Expr, typ ast.Expr) {
+	if p.trace {
+		defer un(trace(p, "VarList"))
+	}
+
+	// a list of identifiers looks like a list of type names
+	for {
+		// parseVarType accepts any type (including parenthesized ones)
+		// even though the syntax does not permit them here: we
+		// accept them all for more robust parsing and complain
+		// afterwards
+		list = append(list, p.parseVarType(isParam))
+		if p.tok != token.COMMA {
+			break
+		}
+		p.next()
+	}
+
+	// if we had a list of identifiers, it must be followed by a type
+	typ = p.tryVarType(isParam)
+	if typ != nil {
+		p.resolve(typ)
+	}
+
+	return
+}
+
+
+func (p *parser) parseParameterList(scope *ast.Scope, ellipsisOk bool) (params []*ast.Field) {
+	if p.trace {
+		defer un(trace(p, "ParameterList"))
+	}
+
+	list, typ := p.parseVarList(ellipsisOk)
+	if typ != nil {
+		// IdentifierList Type
+		idents := p.makeIdentList(list)
+		field := &ast.Field{nil, idents, typ, nil, nil}
+		params = append(params, field)
+		// Go spec: The scope of an identifier denoting a function
+		// parameter or result variable is the function body.
+		p.declare(field, scope, ast.Var, idents...)
+		if p.tok == token.COMMA {
+			p.next()
+		}
+
+		for p.tok != token.RPAREN && p.tok != token.EOF {
+			idents := p.parseIdentList()
+			typ := p.parseVarType(ellipsisOk)
+			field := &ast.Field{nil, idents, typ, nil, nil}
+			params = append(params, field)
+			// Go spec: The scope of an identifier denoting a function
+			// parameter or result variable is the function body.
+			p.declare(field, scope, ast.Var, idents...)
+			if p.tok != token.COMMA {
+				break
+			}
+			p.next()
+		}
+
+	} else {
+		// Type { "," Type } (anonymous parameters)
+		params = make([]*ast.Field, len(list))
+		for i, x := range list {
+			p.resolve(x)
+			params[i] = &ast.Field{Type: x}
+		}
+	}
+
+	return
+}
+
+
+func (p *parser) parseParameters(scope *ast.Scope, ellipsisOk bool) *ast.FieldList {
+	if p.trace {
+		defer un(trace(p, "Parameters"))
+	}
+
+	var params []*ast.Field
+	lparen := p.expect(token.LPAREN)
+	if p.tok != token.RPAREN {
+		params = p.parseParameterList(scope, ellipsisOk)
+	}
+	rparen := p.expect(token.RPAREN)
+
+	return &ast.FieldList{lparen, params, rparen}
+}
+
+
+func (p *parser) parseResult(scope *ast.Scope) *ast.FieldList {
+	if p.trace {
+		defer un(trace(p, "Result"))
+	}
+
+	if p.tok == token.LPAREN {
+		return p.parseParameters(scope, false)
+	}
+
+	typ := p.tryType()
+	if typ != nil {
+		list := make([]*ast.Field, 1)
+		list[0] = &ast.Field{Type: typ}
+		return &ast.FieldList{List: list}
+	}
+
+	return nil
+}
+
+
+func (p *parser) parseSignature(scope *ast.Scope) (params, results *ast.FieldList) {
+	if p.trace {
+		defer un(trace(p, "Signature"))
+	}
+
+	params = p.parseParameters(scope, true)
+	results = p.parseResult(scope)
+
+	return
+}
+
+
+func (p *parser) parseFuncType() (*ast.FuncType, *ast.Scope) {
+	if p.trace {
+		defer un(trace(p, "FuncType"))
+	}
+
+	pos := p.expect(token.FUNC)
+	scope := ast.NewScope(p.topScope) // function scope
+	params, results := p.parseSignature(scope)
+
+	return &ast.FuncType{pos, params, results}, scope
+}
+
+
+func (p *parser) parseMethodSpec(scope *ast.Scope) *ast.Field {
+	if p.trace {
+		defer un(trace(p, "MethodSpec"))
+	}
+
+	doc := p.leadComment
+	var idents []*ast.Ident
+	var typ ast.Expr
+	x := p.parseTypeName()
+	if ident, isIdent := x.(*ast.Ident); isIdent && p.tok == token.LPAREN {
+		// method
+		idents = []*ast.Ident{ident}
+		scope := ast.NewScope(nil) // method scope
+		params, results := p.parseSignature(scope)
+		typ = &ast.FuncType{token.NoPos, params, results}
+	} else {
+		// embedded interface
+		typ = x
+	}
+	p.expectSemi() // call before accessing p.linecomment
+
+	spec := &ast.Field{doc, idents, typ, nil, p.lineComment}
+	p.declare(spec, scope, ast.Fun, idents...)
+
+	return spec
+}
+
+
+func (p *parser) parseInterfaceType() *ast.InterfaceType {
+	if p.trace {
+		defer un(trace(p, "InterfaceType"))
+	}
+
+	pos := p.expect(token.INTERFACE)
+	lbrace := p.expect(token.LBRACE)
+	scope := ast.NewScope(nil) // interface scope
+	var list []*ast.Field
+	for p.tok == token.IDENT {
+		list = append(list, p.parseMethodSpec(scope))
+	}
+	rbrace := p.expect(token.RBRACE)
+
+	// TODO(gri): store interface scope in AST
+	return &ast.InterfaceType{pos, &ast.FieldList{lbrace, list, rbrace}, false}
+}
+
+
+func (p *parser) parseMapType() *ast.MapType {
+	if p.trace {
+		defer un(trace(p, "MapType"))
+	}
+
+	pos := p.expect(token.MAP)
+	p.expect(token.LBRACK)
+	key := p.parseType()
+	p.expect(token.RBRACK)
+	value := p.parseType()
+
+	return &ast.MapType{pos, key, value}
+}
+
+
+func (p *parser) parseChanType() *ast.ChanType {
+	if p.trace {
+		defer un(trace(p, "ChanType"))
+	}
+
+	pos := p.pos
+	dir := ast.SEND | ast.RECV
+	if p.tok == token.CHAN {
+		p.next()
+		if p.tok == token.ARROW {
+			p.next()
+			dir = ast.SEND
+		}
+	} else {
+		p.expect(token.ARROW)
+		p.expect(token.CHAN)
+		dir = ast.RECV
+	}
+	value := p.parseType()
+
+	return &ast.ChanType{pos, dir, value}
+}
+
+
+// If the result is an identifier, it is not resolved.
+func (p *parser) tryIdentOrType(ellipsisOk bool) ast.Expr {
+	switch p.tok {
+	case token.IDENT:
+		return p.parseTypeName()
+	case token.LBRACK:
+		return p.parseArrayType(ellipsisOk)
+	case token.STRUCT:
+		return p.parseStructType()
+	case token.MUL:
+		return p.parsePointerType()
+	case token.FUNC:
+		typ, _ := p.parseFuncType()
+		return typ
+	case token.INTERFACE:
+		return p.parseInterfaceType()
+	case token.MAP:
+		return p.parseMapType()
+	case token.CHAN, token.ARROW:
+		return p.parseChanType()
+	case token.LPAREN:
+		lparen := p.pos
+		p.next()
+		typ := p.parseType()
+		rparen := p.expect(token.RPAREN)
+		return &ast.ParenExpr{lparen, typ, rparen}
+	}
+
+	// no type found
+	return nil
+}
+
+
+func (p *parser) tryType() ast.Expr {
+	typ := p.tryIdentOrType(false)
+	if typ != nil {
+		p.resolve(typ)
+	}
+	return typ
+}
+
+
+// ----------------------------------------------------------------------------
+// Blocks
+
+func (p *parser) parseStmtList() (list []ast.Stmt) {
+	if p.trace {
+		defer un(trace(p, "StatementList"))
+	}
+
+	for p.tok != token.CASE && p.tok != token.DEFAULT && p.tok != token.RBRACE && p.tok != token.EOF {
+		list = append(list, p.parseStmt())
+	}
+
+	return
+}
+
+
+func (p *parser) parseBody(scope *ast.Scope) *ast.BlockStmt {
+	if p.trace {
+		defer un(trace(p, "Body"))
+	}
+
+	lbrace := p.expect(token.LBRACE)
+	p.topScope = scope // open function scope
+	p.openLabelScope()
+	list := p.parseStmtList()
+	p.closeLabelScope()
+	p.closeScope()
+	rbrace := p.expect(token.RBRACE)
+
+	return &ast.BlockStmt{lbrace, list, rbrace}
+}
+
+
+func (p *parser) parseBlockStmt() *ast.BlockStmt {
+	if p.trace {
+		defer un(trace(p, "BlockStmt"))
+	}
+
+	lbrace := p.expect(token.LBRACE)
+	p.openScope()
+	list := p.parseStmtList()
+	p.closeScope()
+	rbrace := p.expect(token.RBRACE)
+
+	return &ast.BlockStmt{lbrace, list, rbrace}
+}
+
+
+// ----------------------------------------------------------------------------
+// Expressions
+
+func (p *parser) parseFuncTypeOrLit() ast.Expr {
+	if p.trace {
+		defer un(trace(p, "FuncTypeOrLit"))
+	}
+
+	typ, scope := p.parseFuncType()
+	if p.tok != token.LBRACE {
+		// function type only
+		return typ
+	}
+
+	p.exprLev++
+	body := p.parseBody(scope)
+	p.exprLev--
+
+	return &ast.FuncLit{typ, body}
+}
+
+
+// parseOperand may return an expression or a raw type (incl. array
+// types of the form [...]T. Callers must verify the result.
+// If lhs is set and the result is an identifier, it is not resolved.
+//
+func (p *parser) parseOperand(lhs bool) ast.Expr {
+	if p.trace {
+		defer un(trace(p, "Operand"))
+	}
+
+	switch p.tok {
+	case token.IDENT:
+		x := p.parseIdent()
+		if !lhs {
+			p.resolve(x)
+		}
+		return x
+
+	case token.INT, token.FLOAT, token.IMAG, token.CHAR, token.STRING:
+		x := &ast.BasicLit{p.pos, p.tok, p.lit}
+		p.next()
+		return x
+
+	case token.LPAREN:
+		lparen := p.pos
+		p.next()
+		p.exprLev++
+		x := p.parseRhs()
+		p.exprLev--
+		rparen := p.expect(token.RPAREN)
+		return &ast.ParenExpr{lparen, x, rparen}
+
+	case token.FUNC:
+		return p.parseFuncTypeOrLit()
+
+	default:
+		if typ := p.tryIdentOrType(true); typ != nil {
+			// could be type for composite literal or conversion
+			_, isIdent := typ.(*ast.Ident)
+			assert(!isIdent, "type cannot be identifier")
+			return typ
+		}
+	}
+
+	pos := p.pos
+	p.errorExpected(pos, "operand")
+	p.next() // make progress
+	return &ast.BadExpr{pos, p.pos}
+}
+
+
+func (p *parser) parseSelector(x ast.Expr) ast.Expr {
+	if p.trace {
+		defer un(trace(p, "Selector"))
+	}
+
+	sel := p.parseIdent()
+
+	return &ast.SelectorExpr{x, sel}
+}
+
+
+func (p *parser) parseTypeAssertion(x ast.Expr) ast.Expr {
+	if p.trace {
+		defer un(trace(p, "TypeAssertion"))
+	}
+
+	p.expect(token.LPAREN)
+	var typ ast.Expr
+	if p.tok == token.TYPE {
+		// type switch: typ == nil
+		p.next()
+	} else {
+		typ = p.parseType()
+	}
+	p.expect(token.RPAREN)
+
+	return &ast.TypeAssertExpr{x, typ}
+}
+
+
+func (p *parser) parseIndexOrSlice(x ast.Expr) ast.Expr {
+	if p.trace {
+		defer un(trace(p, "IndexOrSlice"))
+	}
+
+	lbrack := p.expect(token.LBRACK)
+	p.exprLev++
+	var low, high ast.Expr
+	isSlice := false
+	if p.tok != token.COLON {
+		low = p.parseRhs()
+	}
+	if p.tok == token.COLON {
+		isSlice = true
+		p.next()
+		if p.tok != token.RBRACK {
+			high = p.parseRhs()
+		}
+	}
+	p.exprLev--
+	rbrack := p.expect(token.RBRACK)
+
+	if isSlice {
+		return &ast.SliceExpr{x, lbrack, low, high, rbrack}
+	}
+	return &ast.IndexExpr{x, lbrack, low, rbrack}
+}
+
+
+func (p *parser) parseCallOrConversion(fun ast.Expr) *ast.CallExpr {
+	if p.trace {
+		defer un(trace(p, "CallOrConversion"))
+	}
+
+	lparen := p.expect(token.LPAREN)
+	p.exprLev++
+	var list []ast.Expr
+	var ellipsis token.Pos
+	for p.tok != token.RPAREN && p.tok != token.EOF && !ellipsis.IsValid() {
+		list = append(list, p.parseRhs())
+		if p.tok == token.ELLIPSIS {
+			ellipsis = p.pos
+			p.next()
+		}
+		if p.tok != token.COMMA {
+			break
+		}
+		p.next()
+	}
+	p.exprLev--
+	rparen := p.expect(token.RPAREN)
+
+	return &ast.CallExpr{fun, lparen, list, ellipsis, rparen}
+}
+
+
+func (p *parser) parseElement(keyOk bool) ast.Expr {
+	if p.trace {
+		defer un(trace(p, "Element"))
+	}
+
+	if p.tok == token.LBRACE {
+		return p.parseLiteralValue(nil)
+	}
+
+	x := p.parseExpr(keyOk) // don't resolve if map key
+	if keyOk {
+		if p.tok == token.COLON {
+			colon := p.pos
+			p.next()
+			return &ast.KeyValueExpr{x, colon, p.parseElement(false)}
+		}
+		p.resolve(x) // not a map key
+	}
+
+	return x
+}
+
+
+func (p *parser) parseElementList() (list []ast.Expr) {
+	if p.trace {
+		defer un(trace(p, "ElementList"))
+	}
+
+	for p.tok != token.RBRACE && p.tok != token.EOF {
+		list = append(list, p.parseElement(true))
+		if p.tok != token.COMMA {
+			break
+		}
+		p.next()
+	}
+
+	return
+}
+
+
+func (p *parser) parseLiteralValue(typ ast.Expr) ast.Expr {
+	if p.trace {
+		defer un(trace(p, "LiteralValue"))
+	}
+
+	lbrace := p.expect(token.LBRACE)
+	var elts []ast.Expr
+	p.exprLev++
+	if p.tok != token.RBRACE {
+		elts = p.parseElementList()
+	}
+	p.exprLev--
+	rbrace := p.expect(token.RBRACE)
+	return &ast.CompositeLit{typ, lbrace, elts, rbrace}
+}
+
+
+// checkExpr checks that x is an expression (and not a type).
+func (p *parser) checkExpr(x ast.Expr) ast.Expr {
+	switch t := unparen(x).(type) {
+	case *ast.BadExpr:
+	case *ast.Ident:
+	case *ast.BasicLit:
+	case *ast.FuncLit:
+	case *ast.CompositeLit:
+	case *ast.ParenExpr:
+		panic("unreachable")
+	case *ast.SelectorExpr:
+	case *ast.IndexExpr:
+	case *ast.SliceExpr:
+	case *ast.TypeAssertExpr:
+		if t.Type == nil {
+			// the form X.(type) is only allowed in type switch expressions
+			p.errorExpected(x.Pos(), "expression")
+			x = &ast.BadExpr{x.Pos(), x.End()}
+		}
+	case *ast.CallExpr:
+	case *ast.StarExpr:
+	case *ast.UnaryExpr:
+		if t.Op == token.RANGE {
+			// the range operator is only allowed at the top of a for statement
+			p.errorExpected(x.Pos(), "expression")
+			x = &ast.BadExpr{x.Pos(), x.End()}
+		}
+	case *ast.BinaryExpr:
+	default:
+		// all other nodes are not proper expressions
+		p.errorExpected(x.Pos(), "expression")
+		x = &ast.BadExpr{x.Pos(), x.End()}
+	}
+	return x
+}
+
+
+// isTypeName returns true iff x is a (qualified) TypeName.
+func isTypeName(x ast.Expr) bool {
+	switch t := x.(type) {
+	case *ast.BadExpr:
+	case *ast.Ident:
+	case *ast.SelectorExpr:
+		_, isIdent := t.X.(*ast.Ident)
+		return isIdent
+	default:
+		return false // all other nodes are not type names
+	}
+	return true
+}
+
+
+// isLiteralType returns true iff x is a legal composite literal type.
+func isLiteralType(x ast.Expr) bool {
+	switch t := x.(type) {
+	case *ast.BadExpr:
+	case *ast.Ident:
+	case *ast.SelectorExpr:
+		_, isIdent := t.X.(*ast.Ident)
+		return isIdent
+	case *ast.ArrayType:
+	case *ast.StructType:
+	case *ast.MapType:
+	default:
+		return false // all other nodes are not legal composite literal types
+	}
+	return true
+}
+
+
+// If x is of the form *T, deref returns T, otherwise it returns x.
+func deref(x ast.Expr) ast.Expr {
+	if p, isPtr := x.(*ast.StarExpr); isPtr {
+		x = p.X
+	}
+	return x
+}
+
+
+// If x is of the form (T), unparen returns unparen(T), otherwise it returns x.
+func unparen(x ast.Expr) ast.Expr {
+	if p, isParen := x.(*ast.ParenExpr); isParen {
+		x = unparen(p.X)
+	}
+	return x
+}
+
+
+// checkExprOrType checks that x is an expression or a type
+// (and not a raw type such as [...]T).
+//
+func (p *parser) checkExprOrType(x ast.Expr) ast.Expr {
+	switch t := unparen(x).(type) {
+	case *ast.ParenExpr:
+		panic("unreachable")
+	case *ast.UnaryExpr:
+		if t.Op == token.RANGE {
+			// the range operator is only allowed at the top of a for statement
+			p.errorExpected(x.Pos(), "expression")
+			x = &ast.BadExpr{x.Pos(), x.End()}
+		}
+	case *ast.ArrayType:
+		if len, isEllipsis := t.Len.(*ast.Ellipsis); isEllipsis {
+			p.error(len.Pos(), "expected array length, found '...'")
+			x = &ast.BadExpr{x.Pos(), x.End()}
+		}
+	}
+
+	// all other nodes are expressions or types
+	return x
+}
+
+
+// If lhs is set and the result is an identifier, it is not resolved.
+func (p *parser) parsePrimaryExpr(lhs bool) ast.Expr {
+	if p.trace {
+		defer un(trace(p, "PrimaryExpr"))
+	}
+
+	x := p.parseOperand(lhs)
+L:
+	for {
+		switch p.tok {
+		case token.PERIOD:
+			p.next()
+			if lhs {
+				p.resolve(x)
+			}
+			switch p.tok {
+			case token.IDENT:
+				x = p.parseSelector(p.checkExpr(x))
+			case token.LPAREN:
+				x = p.parseTypeAssertion(p.checkExpr(x))
+			default:
+				pos := p.pos
+				p.next() // make progress
+				p.errorExpected(pos, "selector or type assertion")
+				x = &ast.BadExpr{pos, p.pos}
+			}
+		case token.LBRACK:
+			if lhs {
+				p.resolve(x)
+			}
+			x = p.parseIndexOrSlice(p.checkExpr(x))
+		case token.LPAREN:
+			if lhs {
+				p.resolve(x)
+			}
+			x = p.parseCallOrConversion(p.checkExprOrType(x))
+		case token.LBRACE:
+			if isLiteralType(x) && (p.exprLev >= 0 || !isTypeName(x)) {
+				if lhs {
+					p.resolve(x)
+				}
+				x = p.parseLiteralValue(x)
+			} else {
+				break L
+			}
+		default:
+			break L
+		}
+		lhs = false // no need to try to resolve again
+	}
+
+	return x
+}
+
+
+// If lhs is set and the result is an identifier, it is not resolved.
+func (p *parser) parseUnaryExpr(lhs bool) ast.Expr {
+	if p.trace {
+		defer un(trace(p, "UnaryExpr"))
+	}
+
+	switch p.tok {
+	case token.ADD, token.SUB, token.NOT, token.XOR, token.AND, token.RANGE:
+		pos, op := p.pos, p.tok
+		p.next()
+		x := p.parseUnaryExpr(false)
+		return &ast.UnaryExpr{pos, op, p.checkExpr(x)}
+
+	case token.ARROW:
+		// channel type or receive expression
+		pos := p.pos
+		p.next()
+		if p.tok == token.CHAN {
+			p.next()
+			value := p.parseType()
+			return &ast.ChanType{pos, ast.RECV, value}
+		}
+
+		x := p.parseUnaryExpr(false)
+		return &ast.UnaryExpr{pos, token.ARROW, p.checkExpr(x)}
+
+	case token.MUL:
+		// pointer type or unary "*" expression
+		pos := p.pos
+		p.next()
+		x := p.parseUnaryExpr(false)
+		return &ast.StarExpr{pos, p.checkExprOrType(x)}
+	}
+
+	return p.parsePrimaryExpr(lhs)
+}
+
+
+// If lhs is set and the result is an identifier, it is not resolved.
+func (p *parser) parseBinaryExpr(lhs bool, prec1 int) ast.Expr {
+	if p.trace {
+		defer un(trace(p, "BinaryExpr"))
+	}
+
+	x := p.parseUnaryExpr(lhs)
+	for prec := p.tok.Precedence(); prec >= prec1; prec-- {
+		for p.tok.Precedence() == prec {
+			pos, op := p.pos, p.tok
+			p.next()
+			if lhs {
+				p.resolve(x)
+				lhs = false
+			}
+			y := p.parseBinaryExpr(false, prec+1)
+			x = &ast.BinaryExpr{p.checkExpr(x), pos, op, p.checkExpr(y)}
+		}
+	}
+
+	return x
+}
+
+
+// If lhs is set and the result is an identifier, it is not resolved.
+// TODO(gri): parseExpr may return a type or even a raw type ([..]int) -
+//            should reject when a type/raw type is obviously not allowed
+func (p *parser) parseExpr(lhs bool) ast.Expr {
+	if p.trace {
+		defer un(trace(p, "Expression"))
+	}
+
+	return p.parseBinaryExpr(lhs, token.LowestPrec+1)
+}
+
+
+func (p *parser) parseRhs() ast.Expr {
+	return p.parseExpr(false)
+}
+
+
+// ----------------------------------------------------------------------------
+// Statements
+
+func (p *parser) parseSimpleStmt(labelOk bool) ast.Stmt {
+	if p.trace {
+		defer un(trace(p, "SimpleStmt"))
+	}
+
+	x := p.parseLhsList()
+
+	switch p.tok {
+	case
+		token.DEFINE, token.ASSIGN, token.ADD_ASSIGN,
+		token.SUB_ASSIGN, token.MUL_ASSIGN, token.QUO_ASSIGN,
+		token.REM_ASSIGN, token.AND_ASSIGN, token.OR_ASSIGN,
+		token.XOR_ASSIGN, token.SHL_ASSIGN, token.SHR_ASSIGN, token.AND_NOT_ASSIGN:
+		// assignment statement
+		pos, tok := p.pos, p.tok
+		p.next()
+		y := p.parseRhsList()
+		return &ast.AssignStmt{x, pos, tok, y}
+	}
+
+	if len(x) > 1 {
+		p.errorExpected(x[0].Pos(), "1 expression")
+		// continue with first expression
+	}
+
+	switch p.tok {
+	case token.COLON:
+		// labeled statement
+		colon := p.pos
+		p.next()
+		if label, isIdent := x[0].(*ast.Ident); labelOk && isIdent {
+			// Go spec: The scope of a label is the body of the function
+			// in which it is declared and excludes the body of any nested
+			// function.
+			stmt := &ast.LabeledStmt{label, colon, p.parseStmt()}
+			p.declare(stmt, p.labelScope, ast.Lbl, label)
+			return stmt
+		}
+		p.error(x[0].Pos(), "illegal label declaration")
+		return &ast.BadStmt{x[0].Pos(), colon + 1}
+
+	case token.ARROW:
+		// send statement
+		arrow := p.pos
+		p.next() // consume "<-"
+		y := p.parseRhs()
+		return &ast.SendStmt{x[0], arrow, y}
+
+	case token.INC, token.DEC:
+		// increment or decrement
+		s := &ast.IncDecStmt{x[0], p.pos, p.tok}
+		p.next() // consume "++" or "--"
+		return s
+	}
+
+	// expression
+	return &ast.ExprStmt{x[0]}
+}
+
+
+func (p *parser) parseCallExpr() *ast.CallExpr {
+	x := p.parseRhs()
+	if call, isCall := x.(*ast.CallExpr); isCall {
+		return call
+	}
+	p.errorExpected(x.Pos(), "function/method call")
+	return nil
+}
+
+
+func (p *parser) parseGoStmt() ast.Stmt {
+	if p.trace {
+		defer un(trace(p, "GoStmt"))
+	}
+
+	pos := p.expect(token.GO)
+	call := p.parseCallExpr()
+	p.expectSemi()
+	if call == nil {
+		return &ast.BadStmt{pos, pos + 2} // len("go")
+	}
+
+	return &ast.GoStmt{pos, call}
+}
+
+
+func (p *parser) parseDeferStmt() ast.Stmt {
+	if p.trace {
+		defer un(trace(p, "DeferStmt"))
+	}
+
+	pos := p.expect(token.DEFER)
+	call := p.parseCallExpr()
+	p.expectSemi()
+	if call == nil {
+		return &ast.BadStmt{pos, pos + 5} // len("defer")
+	}
+
+	return &ast.DeferStmt{pos, call}
+}
+
+
+func (p *parser) parseReturnStmt() *ast.ReturnStmt {
+	if p.trace {
+		defer un(trace(p, "ReturnStmt"))
+	}
+
+	pos := p.pos
+	p.expect(token.RETURN)
+	var x []ast.Expr
+	if p.tok != token.SEMICOLON && p.tok != token.RBRACE {
+		x = p.parseRhsList()
+	}
+	p.expectSemi()
+
+	return &ast.ReturnStmt{pos, x}
+}
+
+
+func (p *parser) parseBranchStmt(tok token.Token) *ast.BranchStmt {
+	if p.trace {
+		defer un(trace(p, "BranchStmt"))
+	}
+
+	pos := p.expect(tok)
+	var label *ast.Ident
+	if tok != token.FALLTHROUGH && p.tok == token.IDENT {
+		label = p.parseIdent()
+		// add to list of unresolved targets
+		n := len(p.targetStack) - 1
+		p.targetStack[n] = append(p.targetStack[n], label)
+	}
+	p.expectSemi()
+
+	return &ast.BranchStmt{pos, tok, label}
+}
+
+
+func (p *parser) makeExpr(s ast.Stmt) ast.Expr {
+	if s == nil {
+		return nil
+	}
+	if es, isExpr := s.(*ast.ExprStmt); isExpr {
+		return p.checkExpr(es.X)
+	}
+	p.error(s.Pos(), "expected condition, found simple statement")
+	return &ast.BadExpr{s.Pos(), s.End()}
+}
+
+
+func (p *parser) parseIfStmt() *ast.IfStmt {
+	if p.trace {
+		defer un(trace(p, "IfStmt"))
+	}
+
+	pos := p.expect(token.IF)
+	p.openScope()
+	defer p.closeScope()
+
+	var s ast.Stmt
+	var x ast.Expr
+	{
+		prevLev := p.exprLev
+		p.exprLev = -1
+		if p.tok == token.SEMICOLON {
+			p.next()
+			x = p.parseRhs()
+		} else {
+			s = p.parseSimpleStmt(false)
+			if p.tok == token.SEMICOLON {
+				p.next()
+				x = p.parseRhs()
+			} else {
+				x = p.makeExpr(s)
+				s = nil
+			}
+		}
+		p.exprLev = prevLev
+	}
+
+	body := p.parseBlockStmt()
+	var else_ ast.Stmt
+	if p.tok == token.ELSE {
+		p.next()
+		else_ = p.parseStmt()
+	} else {
+		p.expectSemi()
+	}
+
+	return &ast.IfStmt{pos, s, x, body, else_}
+}
+
+
+func (p *parser) parseTypeList() (list []ast.Expr) {
+	if p.trace {
+		defer un(trace(p, "TypeList"))
+	}
+
+	list = append(list, p.parseType())
+	for p.tok == token.COMMA {
+		p.next()
+		list = append(list, p.parseType())
+	}
+
+	return
+}
+
+
+func (p *parser) parseCaseClause(exprSwitch bool) *ast.CaseClause {
+	if p.trace {
+		defer un(trace(p, "CaseClause"))
+	}
+
+	pos := p.pos
+	var list []ast.Expr
+	if p.tok == token.CASE {
+		p.next()
+		if exprSwitch {
+			list = p.parseRhsList()
+		} else {
+			list = p.parseTypeList()
+		}
+	} else {
+		p.expect(token.DEFAULT)
+	}
+
+	colon := p.expect(token.COLON)
+	p.openScope()
+	body := p.parseStmtList()
+	p.closeScope()
+
+	return &ast.CaseClause{pos, list, colon, body}
+}
+
+
+func isExprSwitch(s ast.Stmt) bool {
+	if s == nil {
+		return true
+	}
+	if e, ok := s.(*ast.ExprStmt); ok {
+		if a, ok := e.X.(*ast.TypeAssertExpr); ok {
+			return a.Type != nil // regular type assertion
+		}
+		return true
+	}
+	return false
+}
+
+
+func (p *parser) parseSwitchStmt() ast.Stmt {
+	if p.trace {
+		defer un(trace(p, "SwitchStmt"))
+	}
+
+	pos := p.expect(token.SWITCH)
+	p.openScope()
+	defer p.closeScope()
+
+	var s1, s2 ast.Stmt
+	if p.tok != token.LBRACE {
+		prevLev := p.exprLev
+		p.exprLev = -1
+		if p.tok != token.SEMICOLON {
+			s2 = p.parseSimpleStmt(false)
+		}
+		if p.tok == token.SEMICOLON {
+			p.next()
+			s1 = s2
+			s2 = nil
+			if p.tok != token.LBRACE {
+				s2 = p.parseSimpleStmt(false)
+			}
+		}
+		p.exprLev = prevLev
+	}
+
+	exprSwitch := isExprSwitch(s2)
+	lbrace := p.expect(token.LBRACE)
+	var list []ast.Stmt
+	for p.tok == token.CASE || p.tok == token.DEFAULT {
+		list = append(list, p.parseCaseClause(exprSwitch))
+	}
+	rbrace := p.expect(token.RBRACE)
+	p.expectSemi()
+	body := &ast.BlockStmt{lbrace, list, rbrace}
+
+	if exprSwitch {
+		return &ast.SwitchStmt{pos, s1, p.makeExpr(s2), body}
+	}
+	// type switch
+	// TODO(gri): do all the checks!
+	return &ast.TypeSwitchStmt{pos, s1, s2, body}
+}
+
+
+func (p *parser) parseCommClause() *ast.CommClause {
+	if p.trace {
+		defer un(trace(p, "CommClause"))
+	}
+
+	p.openScope()
+	pos := p.pos
+	var comm ast.Stmt
+	if p.tok == token.CASE {
+		p.next()
+		lhs := p.parseLhsList()
+		if p.tok == token.ARROW {
+			// SendStmt
+			if len(lhs) > 1 {
+				p.errorExpected(lhs[0].Pos(), "1 expression")
+				// continue with first expression
+			}
+			arrow := p.pos
+			p.next()
+			rhs := p.parseRhs()
+			comm = &ast.SendStmt{lhs[0], arrow, rhs}
+		} else {
+			// RecvStmt
+			pos := p.pos
+			tok := p.tok
+			var rhs ast.Expr
+			if tok == token.ASSIGN || tok == token.DEFINE {
+				// RecvStmt with assignment
+				if len(lhs) > 2 {
+					p.errorExpected(lhs[0].Pos(), "1 or 2 expressions")
+					// continue with first two expressions
+					lhs = lhs[0:2]
+				}
+				p.next()
+				rhs = p.parseRhs()
+			} else {
+				// rhs must be single receive operation
+				if len(lhs) > 1 {
+					p.errorExpected(lhs[0].Pos(), "1 expression")
+					// continue with first expression
+				}
+				rhs = lhs[0]
+				lhs = nil // there is no lhs
+			}
+			if x, isUnary := rhs.(*ast.UnaryExpr); !isUnary || x.Op != token.ARROW {
+				p.errorExpected(rhs.Pos(), "send or receive operation")
+				rhs = &ast.BadExpr{rhs.Pos(), rhs.End()}
+			}
+			if lhs != nil {
+				comm = &ast.AssignStmt{lhs, pos, tok, []ast.Expr{rhs}}
+			} else {
+				comm = &ast.ExprStmt{rhs}
+			}
+		}
+	} else {
+		p.expect(token.DEFAULT)
+	}
+
+	colon := p.expect(token.COLON)
+	body := p.parseStmtList()
+	p.closeScope()
+
+	return &ast.CommClause{pos, comm, colon, body}
+}
+
+
+func (p *parser) parseSelectStmt() *ast.SelectStmt {
+	if p.trace {
+		defer un(trace(p, "SelectStmt"))
+	}
+
+	pos := p.expect(token.SELECT)
+	lbrace := p.expect(token.LBRACE)
+	var list []ast.Stmt
+	for p.tok == token.CASE || p.tok == token.DEFAULT {
+		list = append(list, p.parseCommClause())
+	}
+	rbrace := p.expect(token.RBRACE)
+	p.expectSemi()
+	body := &ast.BlockStmt{lbrace, list, rbrace}
+
+	return &ast.SelectStmt{pos, body}
+}
+
+
+func (p *parser) parseForStmt() ast.Stmt {
+	if p.trace {
+		defer un(trace(p, "ForStmt"))
+	}
+
+	pos := p.expect(token.FOR)
+	p.openScope()
+	defer p.closeScope()
+
+	var s1, s2, s3 ast.Stmt
+	if p.tok != token.LBRACE {
+		prevLev := p.exprLev
+		p.exprLev = -1
+		if p.tok != token.SEMICOLON {
+			s2 = p.parseSimpleStmt(false)
+		}
+		if p.tok == token.SEMICOLON {
+			p.next()
+			s1 = s2
+			s2 = nil
+			if p.tok != token.SEMICOLON {
+				s2 = p.parseSimpleStmt(false)
+			}
+			p.expectSemi()
+			if p.tok != token.LBRACE {
+				s3 = p.parseSimpleStmt(false)
+			}
+		}
+		p.exprLev = prevLev
+	}
+
+	body := p.parseBlockStmt()
+	p.expectSemi()
+
+	if as, isAssign := s2.(*ast.AssignStmt); isAssign {
+		// possibly a for statement with a range clause; check assignment operator
+		if as.Tok != token.ASSIGN && as.Tok != token.DEFINE {
+			p.errorExpected(as.TokPos, "'=' or ':='")
+			return &ast.BadStmt{pos, body.End()}
+		}
+		// check lhs
+		var key, value ast.Expr
+		switch len(as.Lhs) {
+		case 2:
+			key, value = as.Lhs[0], as.Lhs[1]
+		case 1:
+			key = as.Lhs[0]
+		default:
+			p.errorExpected(as.Lhs[0].Pos(), "1 or 2 expressions")
+			return &ast.BadStmt{pos, body.End()}
+		}
+		// check rhs
+		if len(as.Rhs) != 1 {
+			p.errorExpected(as.Rhs[0].Pos(), "1 expression")
+			return &ast.BadStmt{pos, body.End()}
+		}
+		if rhs, isUnary := as.Rhs[0].(*ast.UnaryExpr); isUnary && rhs.Op == token.RANGE {
+			// rhs is range expression
+			// (any short variable declaration was handled by parseSimpleStat above)
+			return &ast.RangeStmt{pos, key, value, as.TokPos, as.Tok, rhs.X, body}
+		}
+		p.errorExpected(s2.Pos(), "range clause")
+		return &ast.BadStmt{pos, body.End()}
+	}
+
+	// regular for statement
+	return &ast.ForStmt{pos, s1, p.makeExpr(s2), s3, body}
+}
+
+
+func (p *parser) parseStmt() (s ast.Stmt) {
+	if p.trace {
+		defer un(trace(p, "Statement"))
+	}
+
+	switch p.tok {
+	case token.CONST, token.TYPE, token.VAR:
+		s = &ast.DeclStmt{p.parseDecl()}
+	case
+		// tokens that may start a top-level expression
+		token.IDENT, token.INT, token.FLOAT, token.CHAR, token.STRING, token.FUNC, token.LPAREN, // operand
+		token.LBRACK, token.STRUCT, // composite type
+		token.MUL, token.AND, token.ARROW, token.ADD, token.SUB, token.XOR: // unary operators
+		s = p.parseSimpleStmt(true)
+		// because of the required look-ahead, labeled statements are
+		// parsed by parseSimpleStmt - don't expect a semicolon after
+		// them
+		if _, isLabeledStmt := s.(*ast.LabeledStmt); !isLabeledStmt {
+			p.expectSemi()
+		}
+	case token.GO:
+		s = p.parseGoStmt()
+	case token.DEFER:
+		s = p.parseDeferStmt()
+	case token.RETURN:
+		s = p.parseReturnStmt()
+	case token.BREAK, token.CONTINUE, token.GOTO, token.FALLTHROUGH:
+		s = p.parseBranchStmt(p.tok)
+	case token.LBRACE:
+		s = p.parseBlockStmt()
+		p.expectSemi()
+	case token.IF:
+		s = p.parseIfStmt()
+	case token.SWITCH:
+		s = p.parseSwitchStmt()
+	case token.SELECT:
+		s = p.parseSelectStmt()
+	case token.FOR:
+		s = p.parseForStmt()
+	case token.SEMICOLON:
+		s = &ast.EmptyStmt{p.pos}
+		p.next()
+	case token.RBRACE:
+		// a semicolon may be omitted before a closing "}"
+		s = &ast.EmptyStmt{p.pos}
+	default:
+		// no statement found
+		pos := p.pos
+		p.errorExpected(pos, "statement")
+		p.next() // make progress
+		s = &ast.BadStmt{pos, p.pos}
+	}
+
+	return
+}
+
+
+// ----------------------------------------------------------------------------
+// Declarations
+
+type parseSpecFunction func(p *parser, doc *ast.CommentGroup, iota int) ast.Spec
+
+
+func parseImportSpec(p *parser, doc *ast.CommentGroup, _ int) ast.Spec {
+	if p.trace {
+		defer un(trace(p, "ImportSpec"))
+	}
+
+	var ident *ast.Ident
+	switch p.tok {
+	case token.PERIOD:
+		ident = &ast.Ident{p.pos, ".", nil}
+		p.next()
+	case token.IDENT:
+		ident = p.parseIdent()
+	}
+
+	var path *ast.BasicLit
+	if p.tok == token.STRING {
+		path = &ast.BasicLit{p.pos, p.tok, p.lit}
+		p.next()
+	} else {
+		p.expect(token.STRING) // use expect() error handling
+	}
+	p.expectSemi() // call before accessing p.linecomment
+
+	// collect imports
+	spec := &ast.ImportSpec{doc, ident, path, p.lineComment}
+	p.imports = append(p.imports, spec)
+
+	return spec
+}
+
+
+func parseConstSpec(p *parser, doc *ast.CommentGroup, iota int) ast.Spec {
+	if p.trace {
+		defer un(trace(p, "ConstSpec"))
+	}
+
+	idents := p.parseIdentList()
+	typ := p.tryType()
+	var values []ast.Expr
+	if typ != nil || p.tok == token.ASSIGN || iota == 0 {
+		p.expect(token.ASSIGN)
+		values = p.parseRhsList()
+	}
+	p.expectSemi() // call before accessing p.linecomment
+
+	// Go spec: The scope of a constant or variable identifier declared inside
+	// a function begins at the end of the ConstSpec or VarSpec and ends at
+	// the end of the innermost containing block.
+	// (Global identifiers are resolved in a separate phase after parsing.)
+	spec := &ast.ValueSpec{doc, idents, typ, values, p.lineComment}
+	p.declare(spec, p.topScope, ast.Con, idents...)
+
+	return spec
+}
+
+
+func parseTypeSpec(p *parser, doc *ast.CommentGroup, _ int) ast.Spec {
+	if p.trace {
+		defer un(trace(p, "TypeSpec"))
+	}
+
+	ident := p.parseIdent()
+
+	// Go spec: The scope of a type identifier declared inside a function begins
+	// at the identifier in the TypeSpec and ends at the end of the innermost
+	// containing block.
+	// (Global identifiers are resolved in a separate phase after parsing.)
+	spec := &ast.TypeSpec{doc, ident, nil, nil}
+	p.declare(spec, p.topScope, ast.Typ, ident)
+
+	spec.Type = p.parseType()
+	p.expectSemi() // call before accessing p.linecomment
+	spec.Comment = p.lineComment
+
+	return spec
+}
+
+
+func parseVarSpec(p *parser, doc *ast.CommentGroup, _ int) ast.Spec {
+	if p.trace {
+		defer un(trace(p, "VarSpec"))
+	}
+
+	idents := p.parseIdentList()
+	typ := p.tryType()
+	var values []ast.Expr
+	if typ == nil || p.tok == token.ASSIGN {
+		p.expect(token.ASSIGN)
+		values = p.parseRhsList()
+	}
+	p.expectSemi() // call before accessing p.linecomment
+
+	// Go spec: The scope of a constant or variable identifier declared inside
+	// a function begins at the end of the ConstSpec or VarSpec and ends at
+	// the end of the innermost containing block.
+	// (Global identifiers are resolved in a separate phase after parsing.)
+	spec := &ast.ValueSpec{doc, idents, typ, values, p.lineComment}
+	p.declare(spec, p.topScope, ast.Var, idents...)
+
+	return spec
+}
+
+
+func (p *parser) parseGenDecl(keyword token.Token, f parseSpecFunction) *ast.GenDecl {
+	if p.trace {
+		defer un(trace(p, "GenDecl("+keyword.String()+")"))
+	}
+
+	doc := p.leadComment
+	pos := p.expect(keyword)
+	var lparen, rparen token.Pos
+	var list []ast.Spec
+	if p.tok == token.LPAREN {
+		lparen = p.pos
+		p.next()
+		for iota := 0; p.tok != token.RPAREN && p.tok != token.EOF; iota++ {
+			list = append(list, f(p, p.leadComment, iota))
+		}
+		rparen = p.expect(token.RPAREN)
+		p.expectSemi()
+	} else {
+		list = append(list, f(p, nil, 0))
+	}
+
+	return &ast.GenDecl{doc, pos, keyword, lparen, list, rparen}
+}
+
+
+func (p *parser) parseReceiver(scope *ast.Scope) *ast.FieldList {
+	if p.trace {
+		defer un(trace(p, "Receiver"))
+	}
+
+	pos := p.pos
+	par := p.parseParameters(scope, false)
+
+	// must have exactly one receiver
+	if par.NumFields() != 1 {
+		p.errorExpected(pos, "exactly one receiver")
+		// TODO determine a better range for BadExpr below
+		par.List = []*ast.Field{&ast.Field{Type: &ast.BadExpr{pos, pos}}}
+		return par
+	}
+
+	// recv type must be of the form ["*"] identifier
+	recv := par.List[0]
+	base := deref(recv.Type)
+	if _, isIdent := base.(*ast.Ident); !isIdent {
+		p.errorExpected(base.Pos(), "(unqualified) identifier")
+		par.List = []*ast.Field{&ast.Field{Type: &ast.BadExpr{recv.Pos(), recv.End()}}}
+	}
+
+	return par
+}
+
+
+func (p *parser) parseFuncDecl() *ast.FuncDecl {
+	if p.trace {
+		defer un(trace(p, "FunctionDecl"))
+	}
+
+	doc := p.leadComment
+	pos := p.expect(token.FUNC)
+	scope := ast.NewScope(p.topScope) // function scope
+
+	var recv *ast.FieldList
+	if p.tok == token.LPAREN {
+		recv = p.parseReceiver(scope)
+	}
+
+	ident := p.parseIdent()
+
+	params, results := p.parseSignature(scope)
+
+	var body *ast.BlockStmt
+	if p.tok == token.LBRACE {
+		body = p.parseBody(scope)
+	}
+	p.expectSemi()
+
+	decl := &ast.FuncDecl{doc, recv, ident, &ast.FuncType{pos, params, results}, body}
+	if recv == nil {
+		// Go spec: The scope of an identifier denoting a constant, type,
+		// variable, or function (but not method) declared at top level
+		// (outside any function) is the package block.
+		//
+		// init() functions cannot be referred to and there may
+		// be more than one - don't put them in the pkgScope
+		if ident.Name != "init" {
+			p.declare(decl, p.pkgScope, ast.Fun, ident)
+		}
+	}
+
+	return decl
+}
+
+
+func (p *parser) parseDecl() ast.Decl {
+	if p.trace {
+		defer un(trace(p, "Declaration"))
+	}
+
+	var f parseSpecFunction
+	switch p.tok {
+	case token.CONST:
+		f = parseConstSpec
+
+	case token.TYPE:
+		f = parseTypeSpec
+
+	case token.VAR:
+		f = parseVarSpec
+
+	case token.FUNC:
+		return p.parseFuncDecl()
+
+	default:
+		pos := p.pos
+		p.errorExpected(pos, "declaration")
+		p.next() // make progress
+		decl := &ast.BadDecl{pos, p.pos}
+		return decl
+	}
+
+	return p.parseGenDecl(p.tok, f)
+}
+
+
+func (p *parser) parseDeclList() (list []ast.Decl) {
+	if p.trace {
+		defer un(trace(p, "DeclList"))
+	}
+
+	for p.tok != token.EOF {
+		list = append(list, p.parseDecl())
+	}
+
+	return
+}
+
+
+// ----------------------------------------------------------------------------
+// Source files
+
+func (p *parser) parseFile() *ast.File {
+	if p.trace {
+		defer un(trace(p, "File"))
+	}
+
+	// package clause
+	doc := p.leadComment
+	pos := p.expect(token.PACKAGE)
+	// Go spec: The package clause is not a declaration;
+	// the package name does not appear in any scope.
+	ident := p.parseIdent()
+	if ident.Name == "_" {
+		p.error(p.pos, "invalid package name _")
+	}
+	p.expectSemi()
+
+	var decls []ast.Decl
+
+	// Don't bother parsing the rest if we had errors already.
+	// Likely not a Go source file at all.
+
+	if p.ErrorCount() == 0 && p.mode&PackageClauseOnly == 0 {
+		// import decls
+		for p.tok == token.IMPORT {
+			decls = append(decls, p.parseGenDecl(token.IMPORT, parseImportSpec))
+		}
+
+		if p.mode&ImportsOnly == 0 {
+			// rest of package body
+			for p.tok != token.EOF {
+				decls = append(decls, p.parseDecl())
+			}
+		}
+	}
+
+	assert(p.topScope == p.pkgScope, "imbalanced scopes")
+
+	// resolve global identifiers within the same file
+	i := 0
+	for _, ident := range p.unresolved {
+		// i <= index for current ident
+		assert(ident.Obj == unresolved, "object already resolved")
+		ident.Obj = p.pkgScope.Lookup(ident.Name) // also removes unresolved sentinel
+		if ident.Obj == nil {
+			p.unresolved[i] = ident
+			i++
+		}
+	}
+
+	// TODO(gri): store p.imports in AST
+	return &ast.File{doc, pos, ident, decls, p.pkgScope, p.imports, p.unresolved[0:i], p.comments}
+}
diff --git a/src/pkg/go/scanner/scanner.go b/src/pkg/go/scanner/scanner.go
index 07b7454c8..509abeca5 100644
--- a/src/pkg/go/scanner/scanner.go
+++ b/src/pkg/go/scanner/scanner.go
@@ -134,36 +134,6 @@ func (S *Scanner) Init(file *token.File, src []byte, err ErrorHandler, mode uint
 }
 
 
-func charString(ch int) string {
-	var s string
-	switch ch {
-	case -1:
-		return `EOF`
-	case '\a':
-		s = `\a`
-	case '\b':
-		s = `\b`
-	case '\f':
-		s = `\f`
-	case '\n':
-		s = `\n`
-	case '\r':
-		s = `\r`
-	case '\t':
-		s = `\t`
-	case '\v':
-		s = `\v`
-	case '\\':
-		s = `\\`
-	case '\'':
-		s = `\'`
-	default:
-		s = string(ch)
-	}
-	return "'" + s + "' (U+" + strconv.Itob(ch, 16) + ")"
-}
-
-
 func (S *Scanner) error(offs int, msg string) {
 	if S.err != nil {
 		S.err.Error(S.file.Position(S.file.Pos(offs)), msg)
@@ -327,6 +297,10 @@ func (S *Scanner) scanNumber(seenDecimalPoint bool) token.Token {
 			// hexadecimal int
 			S.next()
 			S.scanMantissa(16)
+			if S.offset-offs <= 2 {
+				// only scanned "0x" or "0X"
+				S.error(offs, "illegal hexadecimal number")
+			}
 		} else {
 			// octal int or float
 			seenDecimalDigit := false
@@ -700,7 +674,7 @@ scanAgain:
 			tok = S.switch3(token.OR, token.OR_ASSIGN, '|', token.LOR)
 		default:
 			if S.mode&AllowIllegalChars == 0 {
-				S.error(offs, "illegal character "+charString(ch))
+				S.error(offs, "illegal character "+strconv.QuoteRune(ch))
 			}
 			insertSemi = S.insertSemi // preserve insertSemi info
 		}
diff --git a/src/pkg/go/scanner/scanner_test.go b/src/pkg/go/scanner/scanner_test.go
index 8afb00ee5..ee1e830a1 100644
--- a/src/pkg/go/scanner/scanner_test.go
+++ b/src/pkg/go/scanner/scanner_test.go
@@ -89,7 +89,7 @@ var tokens = [...]elt{
 		literal,
 	},
 
-	// Operators and delimitors
+	// Operators and delimiters
 	{token.ADD, "+", operator},
 	{token.SUB, "-", operator},
 	{token.MUL, "*", operator},
@@ -650,7 +650,9 @@ var errors = []struct {
 	pos int
 	err string
 }{
-	{`#`, token.ILLEGAL, 0, "illegal character '#' (U+23)"},
+	{"\a", token.ILLEGAL, 0, "illegal character '\\a'"},
+	{`#`, token.ILLEGAL, 0, "illegal character '#'"},
+	{`…`, token.ILLEGAL, 0, "illegal character '…'"},
 	{`' '`, token.CHAR, 0, ""},
 	{`''`, token.CHAR, 0, "illegal character literal"},
 	{`'\8'`, token.CHAR, 2, "unknown escape sequence"},
@@ -670,6 +672,8 @@ var errors = []struct {
 	{"078e0", token.FLOAT, 0, ""},
 	{"078", token.INT, 0, "illegal octal number"},
 	{"07800000009", token.INT, 0, "illegal octal number"},
+	{"0x", token.INT, 0, "illegal hexadecimal number"},
+	{"0X", token.INT, 0, "illegal hexadecimal number"},
 	{"\"abc\x00def\"", token.STRING, 4, "illegal character NUL"},
 	{"\"abc\x80def\"", token.STRING, 4, "illegal UTF-8 encoding"},
 }
diff --git a/src/pkg/go/token/position.go b/src/pkg/go/token/position.go
index 809e53f0a..23a3cc00f 100644
--- a/src/pkg/go/token/position.go
+++ b/src/pkg/go/token/position.go
@@ -94,10 +94,14 @@ func searchFiles(a []*File, x int) int {
 
 
 func (s *FileSet) file(p Pos) *File {
+	if f := s.last; f != nil && f.base <= int(p) && int(p) <= f.base+f.size {
+		return f
+	}
 	if i := searchFiles(s.files, int(p)); i >= 0 {
 		f := s.files[i]
 		// f.base <= int(p) by definition of searchFiles
 		if int(p) <= f.base+f.size {
+			s.last = f
 			return f
 		}
 	}
@@ -131,7 +135,7 @@ func (f *File) position(p Pos) (pos Position) {
 func (s *FileSet) Position(p Pos) (pos Position) {
 	if p != NoPos {
 		// TODO(gri) consider optimizing the case where p
-		//           is in the last file addded, or perhaps
+		//           is in the last file added, or perhaps
 		//           looked at - will eliminate one level
 		//           of search
 		s.mutex.RLock()
@@ -316,8 +320,26 @@ func (f *File) Position(p Pos) (pos Position) {
 }
 
 
-func searchUints(a []int, x int) int {
-	return sort.Search(len(a), func(i int) bool { return a[i] > x }) - 1
+func searchInts(a []int, x int) int {
+	// This function body is a manually inlined version of:
+	//
+	//   return sort.Search(len(a), func(i int) bool { return a[i] > x }) - 1
+	//
+	// With better compiler optimizations, this may not be needed in the
+	// future, but at the moment this change improves the go/printer
+	// benchmark performance by ~30%. This has a direct impact on the
+	// speed of gofmt and thus seems worthwhile (2011-04-29).
+	i, j := 0, len(a)
+	for i < j {
+		h := i + (j-i)/2 // avoid overflow when computing h
+		// i ≤ h < j
+		if a[h] <= x {
+			i = h + 1
+		} else {
+			j = h
+		}
+	}
+	return i - 1
 }
 
 
@@ -329,14 +351,17 @@ func searchLineInfos(a []lineInfo, x int) int {
 // info returns the file name, line, and column number for a file offset.
 func (f *File) info(offset int) (filename string, line, column int) {
 	filename = f.name
-	if i := searchUints(f.lines, offset); i >= 0 {
+	if i := searchInts(f.lines, offset); i >= 0 {
 		line, column = i+1, offset-f.lines[i]+1
 	}
-	if i := searchLineInfos(f.infos, offset); i >= 0 {
-		alt := &f.infos[i]
-		filename = alt.filename
-		if i := searchUints(f.lines, alt.offset); i >= 0 {
-			line += alt.line - i - 1
+	if len(f.infos) > 0 {
+		// almost no files have extra line infos
+		if i := searchLineInfos(f.infos, offset); i >= 0 {
+			alt := &f.infos[i]
+			filename = alt.filename
+			if i := searchInts(f.lines, alt.offset); i >= 0 {
+				line += alt.line - i - 1
+			}
 		}
 	}
 	return
@@ -348,10 +373,10 @@ func (f *File) info(offset int) (filename string, line, column int) {
 // may invoke them concurrently.
 //
 type FileSet struct {
-	mutex sync.RWMutex  // protects the file set
-	base  int           // base offset for the next file
-	files []*File       // list of files in the order added to the set
-	index map[*File]int // file -> files index for quick lookup
+	mutex sync.RWMutex // protects the file set
+	base  int          // base offset for the next file
+	files []*File      // list of files in the order added to the set
+	last  *File        // cache of last file looked up
 }
 
 
@@ -359,7 +384,6 @@ type FileSet struct {
 func NewFileSet() *FileSet {
 	s := new(FileSet)
 	s.base = 1 // 0 == NoPos
-	s.index = make(map[*File]int)
 	return s
 }
 
@@ -405,8 +429,8 @@ func (s *FileSet) AddFile(filename string, base, size int) *File {
 	}
 	// add the file to the file set
 	s.base = base
-	s.index[f] = len(s.files)
 	s.files = append(s.files, f)
+	s.last = f
 	return f
 }
 
diff --git a/src/pkg/go/types/Makefile b/src/pkg/go/types/Makefile
index 54e762b36..4ca707c73 100644
--- a/src/pkg/go/types/Makefile
+++ b/src/pkg/go/types/Makefile
@@ -6,6 +6,7 @@ include ../../../Make.inc
 
 TARG=go/types
 GOFILES=\
+	check.go\
 	const.go\
 	exportdata.go\
 	gcimporter.go\
diff --git a/src/pkg/go/types/check.go b/src/pkg/go/types/check.go
new file mode 100644
index 000000000..02d662926
--- /dev/null
+++ b/src/pkg/go/types/check.go
@@ -0,0 +1,233 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements the Check function, which typechecks a package.
+
+package types
+
+import (
+	"fmt"
+	"go/ast"
+	"go/scanner"
+	"go/token"
+	"os"
+	"strconv"
+)
+
+
+const debug = false
+
+
+type checker struct {
+	fset *token.FileSet
+	scanner.ErrorVector
+	types map[ast.Expr]Type
+}
+
+
+func (c *checker) errorf(pos token.Pos, format string, args ...interface{}) string {
+	msg := fmt.Sprintf(format, args...)
+	c.Error(c.fset.Position(pos), msg)
+	return msg
+}
+
+
+// collectFields collects struct fields tok = token.STRUCT), interface methods
+// (tok = token.INTERFACE), and function arguments/results (tok = token.FUNC).
+func (c *checker) collectFields(tok token.Token, list *ast.FieldList, cycleOk bool) (fields ObjList, tags []string, isVariadic bool) {
+	if list != nil {
+		for _, field := range list.List {
+			ftype := field.Type
+			if t, ok := ftype.(*ast.Ellipsis); ok {
+				ftype = t.Elt
+				isVariadic = true
+			}
+			typ := c.makeType(ftype, cycleOk)
+			tag := ""
+			if field.Tag != nil {
+				assert(field.Tag.Kind == token.STRING)
+				tag, _ = strconv.Unquote(field.Tag.Value)
+			}
+			if len(field.Names) > 0 {
+				// named fields
+				for _, name := range field.Names {
+					obj := name.Obj
+					obj.Type = typ
+					fields = append(fields, obj)
+					if tok == token.STRUCT {
+						tags = append(tags, tag)
+					}
+				}
+			} else {
+				// anonymous field
+				switch tok {
+				case token.STRUCT:
+					tags = append(tags, tag)
+					fallthrough
+				case token.FUNC:
+					obj := ast.NewObj(ast.Var, "")
+					obj.Type = typ
+					fields = append(fields, obj)
+				case token.INTERFACE:
+					utyp := Underlying(typ)
+					if typ, ok := utyp.(*Interface); ok {
+						// TODO(gri) This is not good enough. Check for double declarations!
+						fields = append(fields, typ.Methods...)
+					} else if _, ok := utyp.(*Bad); !ok {
+						// if utyp is Bad, don't complain (the root cause was reported before)
+						c.errorf(ftype.Pos(), "interface contains embedded non-interface type")
+					}
+				default:
+					panic("unreachable")
+				}
+			}
+		}
+	}
+	return
+}
+
+
+// makeType makes a new type for an AST type specification x or returns
+// the type referred to by a type name x. If cycleOk is set, a type may
+// refer to itself directly or indirectly; otherwise cycles are errors.
+//
+func (c *checker) makeType(x ast.Expr, cycleOk bool) (typ Type) {
+	if debug {
+		fmt.Printf("makeType (cycleOk = %v)\n", cycleOk)
+		ast.Print(c.fset, x)
+		defer func() {
+			fmt.Printf("-> %T %v\n\n", typ, typ)
+		}()
+	}
+
+	switch t := x.(type) {
+	case *ast.BadExpr:
+		return &Bad{}
+
+	case *ast.Ident:
+		// type name
+		obj := t.Obj
+		if obj == nil {
+			// unresolved identifier (error has been reported before)
+			return &Bad{Msg: "unresolved identifier"}
+		}
+		if obj.Kind != ast.Typ {
+			msg := c.errorf(t.Pos(), "%s is not a type", t.Name)
+			return &Bad{Msg: msg}
+		}
+		c.checkObj(obj, cycleOk)
+		if !cycleOk && obj.Type.(*Name).Underlying == nil {
+			// TODO(gri) Enable this message again once its position
+			// is independent of the underlying map implementation.
+			// msg := c.errorf(obj.Pos(), "illegal cycle in declaration of %s", obj.Name)
+			msg := "illegal cycle"
+			return &Bad{Msg: msg}
+		}
+		return obj.Type.(Type)
+
+	case *ast.ParenExpr:
+		return c.makeType(t.X, cycleOk)
+
+	case *ast.SelectorExpr:
+		// qualified identifier
+		// TODO (gri) eventually, this code belongs to expression
+		//            type checking - here for the time being
+		if ident, ok := t.X.(*ast.Ident); ok {
+			if obj := ident.Obj; obj != nil {
+				if obj.Kind != ast.Pkg {
+					msg := c.errorf(ident.Pos(), "%s is not a package", obj.Name)
+					return &Bad{Msg: msg}
+				}
+				// TODO(gri) we have a package name but don't
+				// have the mapping from package name to package
+				// scope anymore (created in ast.NewPackage).
+				return &Bad{} // for now
+			}
+		}
+		// TODO(gri) can this really happen (the parser should have excluded this)?
+		msg := c.errorf(t.Pos(), "expected qualified identifier")
+		return &Bad{Msg: msg}
+
+	case *ast.StarExpr:
+		return &Pointer{Base: c.makeType(t.X, true)}
+
+	case *ast.ArrayType:
+		if t.Len != nil {
+			// TODO(gri) compute length
+			return &Array{Elt: c.makeType(t.Elt, cycleOk)}
+		}
+		return &Slice{Elt: c.makeType(t.Elt, true)}
+
+	case *ast.StructType:
+		fields, tags, _ := c.collectFields(token.STRUCT, t.Fields, cycleOk)
+		return &Struct{Fields: fields, Tags: tags}
+
+	case *ast.FuncType:
+		params, _, _ := c.collectFields(token.FUNC, t.Params, true)
+		results, _, isVariadic := c.collectFields(token.FUNC, t.Results, true)
+		return &Func{Recv: nil, Params: params, Results: results, IsVariadic: isVariadic}
+
+	case *ast.InterfaceType:
+		methods, _, _ := c.collectFields(token.INTERFACE, t.Methods, cycleOk)
+		methods.Sort()
+		return &Interface{Methods: methods}
+
+	case *ast.MapType:
+		return &Map{Key: c.makeType(t.Key, true), Elt: c.makeType(t.Key, true)}
+
+	case *ast.ChanType:
+		return &Chan{Dir: t.Dir, Elt: c.makeType(t.Value, true)}
+	}
+
+	panic(fmt.Sprintf("unreachable (%T)", x))
+}
+
+
+// checkObj type checks an object.
+func (c *checker) checkObj(obj *ast.Object, ref bool) {
+	if obj.Type != nil {
+		// object has already been type checked
+		return
+	}
+
+	switch obj.Kind {
+	case ast.Bad:
+		// ignore
+
+	case ast.Con:
+		// TODO(gri) complete this
+
+	case ast.Typ:
+		typ := &Name{Obj: obj}
+		obj.Type = typ // "mark" object so recursion terminates
+		typ.Underlying = Underlying(c.makeType(obj.Decl.(*ast.TypeSpec).Type, ref))
+
+	case ast.Var:
+		// TODO(gri) complete this
+
+	case ast.Fun:
+		// TODO(gri) complete this
+
+	default:
+		panic("unreachable")
+	}
+}
+
+
+// Check typechecks a package.
+// It augments the AST by assigning types to all ast.Objects and returns a map
+// of types for all expression nodes in statements, and a scanner.ErrorList if
+// there are errors.
+//
+func Check(fset *token.FileSet, pkg *ast.Package) (types map[ast.Expr]Type, err os.Error) {
+	var c checker
+	c.fset = fset
+	c.types = make(map[ast.Expr]Type)
+
+	for _, obj := range pkg.Scope.Objects {
+		c.checkObj(obj, false)
+	}
+
+	return c.types, c.GetError(scanner.NoMultiples)
+}
diff --git a/src/pkg/go/types/check_test.go b/src/pkg/go/types/check_test.go
new file mode 100644
index 000000000..6ecb12b1e
--- /dev/null
+++ b/src/pkg/go/types/check_test.go
@@ -0,0 +1,224 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements a typechecker test harness. The packages specified
+// in tests are typechecked. Error messages reported by the typechecker are
+// compared against the error messages expected in the test files.
+//
+// Expected errors are indicated in the test files by putting a comment
+// of the form /* ERROR "rx" */ immediately following an offending token.
+// The harness will verify that an error matching the regular expression
+// rx is reported at that source position. Consecutive comments may be
+// used to indicate multiple errors for the same token position.
+//
+// For instance, the following test file indicates that a "not declared"
+// error should be reported for the undeclared variable x:
+//
+//	package p
+//	func f() {
+//		_ = x /* ERROR "not declared" */ + 1
+//	}
+
+package types
+
+import (
+	"fmt"
+	"go/ast"
+	"go/parser"
+	"go/scanner"
+	"go/token"
+	"io/ioutil"
+	"os"
+	"regexp"
+	"testing"
+)
+
+
+// The test filenames do not end in .go so that they are invisible
+// to gofmt since they contain comments that must not change their
+// positions relative to surrounding tokens.
+
+var tests = []struct {
+	name  string
+	files []string
+}{
+	{"test0", []string{"testdata/test0.src"}},
+}
+
+
+var fset = token.NewFileSet()
+
+
+// TODO(gri) This functionality should be in token.Fileset.
+func getFile(filename string) *token.File {
+	for f := range fset.Files() {
+		if f.Name() == filename {
+			return f
+		}
+	}
+	return nil
+}
+
+
+// TODO(gri) This functionality should be in token.Fileset.
+func getPos(filename string, offset int) token.Pos {
+	if f := getFile(filename); f != nil {
+		return f.Pos(offset)
+	}
+	return token.NoPos
+}
+
+
+// TODO(gri) Need to revisit parser interface. We should be able to use parser.ParseFiles
+//           or a similar function instead.
+func parseFiles(t *testing.T, testname string, filenames []string) (map[string]*ast.File, os.Error) {
+	files := make(map[string]*ast.File)
+	var errors scanner.ErrorList
+	for _, filename := range filenames {
+		if _, exists := files[filename]; exists {
+			t.Fatalf("%s: duplicate file %s", testname, filename)
+		}
+		file, err := parser.ParseFile(fset, filename, nil, parser.DeclarationErrors)
+		if file == nil {
+			t.Fatalf("%s: could not parse file %s", testname, filename)
+		}
+		files[filename] = file
+		if err != nil {
+			// if the parser returns a non-scanner.ErrorList error
+			// the file couldn't be read in the first place and
+			// file == nil; in that case we shouldn't reach here
+			errors = append(errors, err.(scanner.ErrorList)...)
+		}
+
+	}
+	return files, errors
+}
+
+
+// ERROR comments must be of the form /* ERROR "rx" */ and rx is
+// a regular expression that matches the expected error message.
+//
+var errRx = regexp.MustCompile(`^/\* *ERROR *"([^"]*)" *\*/$`)
+
+// expectedErrors collects the regular expressions of ERROR comments found
+// in files and returns them as a map of error positions to error messages.
+//
+func expectedErrors(t *testing.T, testname string, files map[string]*ast.File) map[token.Pos]string {
+	errors := make(map[token.Pos]string)
+	for filename := range files {
+		src, err := ioutil.ReadFile(filename)
+		if err != nil {
+			t.Fatalf("%s: could not read %s", testname, filename)
+		}
+
+		var s scanner.Scanner
+		// file was parsed already - do not add it again to the file
+		// set otherwise the position information returned here will
+		// not match the position information collected by the parser
+		s.Init(getFile(filename), src, nil, scanner.ScanComments)
+		var prev token.Pos // position of last non-comment token
+
+	scanFile:
+		for {
+			pos, tok, lit := s.Scan()
+			switch tok {
+			case token.EOF:
+				break scanFile
+			case token.COMMENT:
+				s := errRx.FindStringSubmatch(lit)
+				if len(s) == 2 {
+					errors[prev] = string(s[1])
+				}
+			default:
+				prev = pos
+			}
+		}
+	}
+	return errors
+}
+
+
+func eliminate(t *testing.T, expected map[token.Pos]string, errors os.Error) {
+	if errors == nil {
+		return
+	}
+	for _, error := range errors.(scanner.ErrorList) {
+		// error.Pos is a token.Position, but we want
+		// a token.Pos so we can do a map lookup
+		// TODO(gri) Need to move scanner.Errors over
+		//           to use token.Pos and file set info.
+		pos := getPos(error.Pos.Filename, error.Pos.Offset)
+		if msg, found := expected[pos]; found {
+			// we expect a message at pos; check if it matches
+			rx, err := regexp.Compile(msg)
+			if err != nil {
+				t.Errorf("%s: %v", error.Pos, err)
+				continue
+			}
+			if match := rx.MatchString(error.Msg); !match {
+				t.Errorf("%s: %q does not match %q", error.Pos, error.Msg, msg)
+				continue
+			}
+			// we have a match - eliminate this error
+			expected[pos] = "", false
+		} else {
+			// To keep in mind when analyzing failed test output:
+			// If the same error position occurs multiple times in errors,
+			// this message will be triggered (because the first error at
+			// the position removes this position from the expected errors).
+			t.Errorf("%s: no (multiple?) error expected, but found: %s", error.Pos, error.Msg)
+		}
+	}
+}
+
+
+func check(t *testing.T, testname string, testfiles []string) {
+	// TODO(gri) Eventually all these different phases should be
+	//           subsumed into a single function call that takes
+	//           a set of files and creates a fully resolved and
+	//           type-checked AST.
+
+	files, err := parseFiles(t, testname, testfiles)
+
+	// we are expecting the following errors
+	// (collect these after parsing the files so that
+	// they are found in the file set)
+	errors := expectedErrors(t, testname, files)
+
+	// verify errors returned by the parser
+	eliminate(t, errors, err)
+
+	// verify errors returned after resolving identifiers
+	pkg, err := ast.NewPackage(fset, files, GcImporter, Universe)
+	eliminate(t, errors, err)
+
+	// verify errors returned by the typechecker
+	_, err = Check(fset, pkg)
+	eliminate(t, errors, err)
+
+	// there should be no expected errors left
+	if len(errors) > 0 {
+		t.Errorf("%s: %d errors not reported:", testname, len(errors))
+		for pos, msg := range errors {
+			t.Errorf("%s: %s\n", fset.Position(pos), msg)
+		}
+	}
+}
+
+
+func TestCheck(t *testing.T) {
+	// For easy debugging w/o changing the testing code,
+	// if there is a local test file, only test that file.
+	const testfile = "test.go"
+	if fi, err := os.Stat(testfile); err == nil && fi.IsRegular() {
+		fmt.Printf("WARNING: Testing only %s (remove it to run all tests)\n", testfile)
+		check(t, testfile, []string{testfile})
+		return
+	}
+
+	// Otherwise, run all the tests.
+	for _, test := range tests {
+		check(t, test.name, test.files)
+	}
+}
diff --git a/src/pkg/go/types/gcimporter.go b/src/pkg/go/types/gcimporter.go
index 30adc04e7..2cfed7726 100644
--- a/src/pkg/go/types/gcimporter.go
+++ b/src/pkg/go/types/gcimporter.go
@@ -74,15 +74,14 @@ func findPkg(path string) (filename, id string) {
 // object/archive file and populates its scope with the results.
 type gcParser struct {
 	scanner scanner.Scanner
-	tok     int                   // current token
-	lit     string                // literal string; only valid for Ident, Int, String tokens
-	id      string                // package id of imported package
-	scope   *ast.Scope            // scope of imported package; alias for deps[id]
-	deps    map[string]*ast.Scope // package id -> package scope
+	tok     int                    // current token
+	lit     string                 // literal string; only valid for Ident, Int, String tokens
+	id      string                 // package id of imported package
+	imports map[string]*ast.Object // package id -> package object
 }
 
 
-func (p *gcParser) init(filename, id string, src io.Reader) {
+func (p *gcParser) init(filename, id string, src io.Reader, imports map[string]*ast.Object) {
 	p.scanner.Init(src)
 	p.scanner.Error = func(_ *scanner.Scanner, msg string) { p.error(msg) }
 	p.scanner.Mode = scanner.ScanIdents | scanner.ScanInts | scanner.ScanStrings | scanner.ScanComments | scanner.SkipComments
@@ -90,8 +89,7 @@ func (p *gcParser) init(filename, id string, src io.Reader) {
 	p.scanner.Filename = filename // for good error messages
 	p.next()
 	p.id = id
-	p.scope = ast.NewScope(nil)
-	p.deps = map[string]*ast.Scope{"unsafe": Unsafe, id: p.scope}
+	p.imports = imports
 }
 
 
@@ -110,9 +108,9 @@ func (p *gcParser) next() {
 
 
 // GcImporter implements the ast.Importer signature.
-func GcImporter(path string) (name string, scope *ast.Scope, err os.Error) {
+func GcImporter(imports map[string]*ast.Object, path string) (pkg *ast.Object, err os.Error) {
 	if path == "unsafe" {
-		return path, Unsafe, nil
+		return Unsafe, nil
 	}
 
 	defer func() {
@@ -130,6 +128,10 @@ func GcImporter(path string) (name string, scope *ast.Scope, err os.Error) {
 		return
 	}
 
+	if pkg = imports[id]; pkg != nil {
+		return // package was imported before
+	}
+
 	buf, err := ExportData(filename)
 	if err != nil {
 		return
@@ -137,13 +139,12 @@ func GcImporter(path string) (name string, scope *ast.Scope, err os.Error) {
 	defer buf.Close()
 
 	if trace {
-		fmt.Printf("importing %s\n", filename)
+		fmt.Printf("importing %s (%s)\n", id, filename)
 	}
 
 	var p gcParser
-	p.init(filename, id, buf)
-	name, scope = p.parseExport()
-
+	p.init(filename, id, buf, imports)
+	pkg = p.parseExport()
 	return
 }
 
@@ -214,21 +215,31 @@ func (p *gcParser) expectKeyword(keyword string) {
 
 // ImportPath = string_lit .
 //
-func (p *gcParser) parsePkgId() *ast.Scope {
+func (p *gcParser) parsePkgId() *ast.Object {
 	id, err := strconv.Unquote(p.expect(scanner.String))
 	if err != nil {
 		p.error(err)
 	}
 
-	scope := p.scope // id == "" stands for the imported package id
-	if id != "" {
-		if scope = p.deps[id]; scope == nil {
-			scope = ast.NewScope(nil)
-			p.deps[id] = scope
-		}
+	switch id {
+	case "":
+		// id == "" stands for the imported package id
+		// (only known at time of package installation)
+		id = p.id
+	case "unsafe":
+		// package unsafe is not in the imports map - handle explicitly
+		return Unsafe
+	}
+
+	pkg := p.imports[id]
+	if pkg == nil {
+		scope = ast.NewScope(nil)
+		pkg = ast.NewObj(ast.Pkg, "")
+		pkg.Data = scope
+		p.imports[id] = pkg
 	}
 
-	return scope
+	return pkg
 }
 
 
@@ -253,13 +264,14 @@ func (p *gcParser) parseDotIdent() string {
 // ExportedName = ImportPath "." dotIdentifier .
 //
 func (p *gcParser) parseExportedName(kind ast.ObjKind) *ast.Object {
-	scope := p.parsePkgId()
+	pkg := p.parsePkgId()
 	p.expect('.')
 	name := p.parseDotIdent()
 
 	// a type may have been declared before - if it exists
 	// already in the respective package scope, return that
 	// type
+	scope := pkg.Data.(*ast.Scope)
 	if kind == ast.Typ {
 		if obj := scope.Lookup(name); obj != nil {
 			assert(obj.Kind == ast.Typ)
@@ -344,28 +356,22 @@ func (p *gcParser) parseName() (name string) {
 
 // Field = Name Type [ ":" string_lit ] .
 //
-func (p *gcParser) parseField(scope *ast.Scope) {
-	// TODO(gri) The code below is not correct for anonymous fields:
-	//           The name is the type name; it should not be empty.
+func (p *gcParser) parseField() (fld *ast.Object, tag string) {
 	name := p.parseName()
 	ftyp := p.parseType()
 	if name == "" {
 		// anonymous field - ftyp must be T or *T and T must be a type name
-		ftyp = Deref(ftyp)
-		if ftyp, ok := ftyp.(*Name); ok {
-			name = ftyp.Obj.Name
-		} else {
+		if _, ok := Deref(ftyp).(*Name); !ok {
 			p.errorf("anonymous field expected")
 		}
 	}
 	if p.tok == ':' {
 		p.next()
-		tag := p.expect(scanner.String)
-		_ = tag // TODO(gri) store tag somewhere
+		tag = p.expect(scanner.String)
 	}
-	fld := ast.NewObj(ast.Var, name)
+	fld = ast.NewObj(ast.Var, name)
 	fld.Type = ftyp
-	scope.Insert(fld)
+	return
 }
 
 
@@ -373,103 +379,124 @@ func (p *gcParser) parseField(scope *ast.Scope) {
 // FieldList  = Field { ";" Field } .
 //
 func (p *gcParser) parseStructType() Type {
+	var fields []*ast.Object
+	var tags []string
+
+	parseField := func() {
+		fld, tag := p.parseField()
+		fields = append(fields, fld)
+		tags = append(tags, tag)
+	}
+
 	p.expectKeyword("struct")
 	p.expect('{')
-	scope := ast.NewScope(nil)
 	if p.tok != '}' {
-		p.parseField(scope)
+		parseField()
 		for p.tok == ';' {
 			p.next()
-			p.parseField(scope)
+			parseField()
 		}
 	}
 	p.expect('}')
-	return &Struct{}
+
+	return &Struct{Fields: fields, Tags: tags}
 }
 
 
-// Parameter = ( identifier | "?" ) [ "..." ] Type .
+// Parameter = ( identifier | "?" ) [ "..." ] Type [ ":" string_lit ] .
 //
-func (p *gcParser) parseParameter(scope *ast.Scope, isVariadic *bool) {
+func (p *gcParser) parseParameter() (par *ast.Object, isVariadic bool) {
 	name := p.parseName()
 	if name == "" {
 		name = "_" // cannot access unnamed identifiers
 	}
-	if isVariadic != nil {
-		if *isVariadic {
-			p.error("... not on final argument")
-		}
-		if p.tok == '.' {
-			p.expectSpecial("...")
-			*isVariadic = true
-		}
+	if p.tok == '.' {
+		p.expectSpecial("...")
+		isVariadic = true
 	}
 	ptyp := p.parseType()
-	par := ast.NewObj(ast.Var, name)
+	// ignore argument tag
+	if p.tok == ':' {
+		p.next()
+		p.expect(scanner.String)
+	}
+	par = ast.NewObj(ast.Var, name)
 	par.Type = ptyp
-	scope.Insert(par)
+	return
 }
 
 
 // Parameters    = "(" [ ParameterList ] ")" .
 // ParameterList = { Parameter "," } Parameter .
 //
-func (p *gcParser) parseParameters(scope *ast.Scope, isVariadic *bool) {
+func (p *gcParser) parseParameters() (list []*ast.Object, isVariadic bool) {
+	parseParameter := func() {
+		par, variadic := p.parseParameter()
+		list = append(list, par)
+		if variadic {
+			if isVariadic {
+				p.error("... not on final argument")
+			}
+			isVariadic = true
+		}
+	}
+
 	p.expect('(')
 	if p.tok != ')' {
-		p.parseParameter(scope, isVariadic)
+		parseParameter()
 		for p.tok == ',' {
 			p.next()
-			p.parseParameter(scope, isVariadic)
+			parseParameter()
 		}
 	}
 	p.expect(')')
+
+	return
 }
 
 
 // Signature = Parameters [ Result ] .
 // Result    = Type | Parameters .
 //
-func (p *gcParser) parseSignature(scope *ast.Scope, isVariadic *bool) {
-	p.parseParameters(scope, isVariadic)
+func (p *gcParser) parseSignature() *Func {
+	params, isVariadic := p.parseParameters()
 
 	// optional result type
+	var results []*ast.Object
 	switch p.tok {
 	case scanner.Ident, scanner.String, '[', '*', '<':
 		// single, unnamed result
 		result := ast.NewObj(ast.Var, "_")
 		result.Type = p.parseType()
-		scope.Insert(result)
+		results = []*ast.Object{result}
 	case '(':
 		// named or multiple result(s)
-		p.parseParameters(scope, nil)
+		var variadic bool
+		results, variadic = p.parseParameters()
+		if variadic {
+			p.error("... not permitted on result type")
+		}
 	}
-}
-
 
-// FuncType = "func" Signature .
-//
-func (p *gcParser) parseFuncType() Type {
-	// "func" already consumed
-	scope := ast.NewScope(nil)
-	isVariadic := false
-	p.parseSignature(scope, &isVariadic)
-	return &Func{IsVariadic: isVariadic}
+	return &Func{Params: params, Results: results, IsVariadic: isVariadic}
 }
 
 
 // MethodSpec = identifier Signature .
 //
-func (p *gcParser) parseMethodSpec(scope *ast.Scope) {
+func (p *gcParser) parseMethodSpec() *ast.Object {
 	if p.tok == scanner.Ident {
 		p.expect(scanner.Ident)
 	} else {
+		// TODO(gri) should this be parseExportedName here?
 		p.parsePkgId()
 		p.expect('.')
 		p.parseDotIdent()
 	}
-	isVariadic := false
-	p.parseSignature(scope, &isVariadic)
+	p.parseSignature()
+
+	// TODO(gri) compute method object
+	return ast.NewObj(ast.Fun, "_")
 }
 
 
@@ -477,18 +504,26 @@ func (p *gcParser) parseMethodSpec(scope *ast.Scope) {
 // MethodList    = MethodSpec { ";" MethodSpec } .
 //
 func (p *gcParser) parseInterfaceType() Type {
+	var methods ObjList
+
+	parseMethod := func() {
+		meth := p.parseMethodSpec()
+		methods = append(methods, meth)
+	}
+
 	p.expectKeyword("interface")
 	p.expect('{')
-	scope := ast.NewScope(nil)
 	if p.tok != '}' {
-		p.parseMethodSpec(scope)
+		parseMethod()
 		for p.tok == ';' {
 			p.next()
-			p.parseMethodSpec(scope)
+			parseMethod()
 		}
 	}
 	p.expect('}')
-	return &Interface{}
+
+	methods.Sort()
+	return &Interface{Methods: methods}
 }
 
 
@@ -520,6 +555,7 @@ func (p *gcParser) parseChanType() Type {
 // TypeName = ExportedName .
 // SliceType = "[" "]" Type .
 // PointerType = "*" Type .
+// FuncType = "func" Signature .
 //
 func (p *gcParser) parseType() Type {
 	switch p.tok {
@@ -530,8 +566,9 @@ func (p *gcParser) parseType() Type {
 		case "struct":
 			return p.parseStructType()
 		case "func":
-			p.next() // parseFuncType assumes "func" is already consumed
-			return p.parseFuncType()
+			// FuncType
+			p.next()
+			return p.parseSignature()
 		case "interface":
 			return p.parseInterfaceType()
 		case "map":
@@ -578,9 +615,10 @@ func (p *gcParser) parseImportDecl() {
 	// The identifier has no semantic meaning in the import data.
 	// It exists so that error messages can print the real package
 	// name: binary.ByteOrder instead of "encoding/binary".ByteOrder.
-	// TODO(gri): Save package id -> package name mapping.
-	p.expect(scanner.Ident)
-	p.parsePkgId()
+	name := p.expect(scanner.Ident)
+	pkg := p.parsePkgId()
+	assert(pkg.Name == "" || pkg.Name == name)
+	pkg.Name = name
 }
 
 
@@ -681,7 +719,7 @@ func (p *gcParser) parseConstDecl() {
 	if obj.Type == nil {
 		obj.Type = typ
 	}
-	_ = x // TODO(gri) store x somewhere
+	obj.Data = x
 }
 
 
@@ -690,12 +728,18 @@ func (p *gcParser) parseConstDecl() {
 func (p *gcParser) parseTypeDecl() {
 	p.expectKeyword("type")
 	obj := p.parseExportedName(ast.Typ)
+
+	// The type object may have been imported before and thus already
+	// have a type associated with it. We still need to parse the type
+	// structure, but throw it away if the object already has a type.
+	// This ensures that all imports refer to the same type object for
+	// a given type declaration.
 	typ := p.parseType()
 
-	name := obj.Type.(*Name)
-	assert(name.Underlying == nil)
-	assert(Underlying(typ) == typ)
-	name.Underlying = typ
+	if name := obj.Type.(*Name); name.Underlying == nil {
+		assert(Underlying(typ) == typ)
+		name.Underlying = typ
+	}
 }
 
 
@@ -713,7 +757,7 @@ func (p *gcParser) parseVarDecl() {
 func (p *gcParser) parseFuncDecl() {
 	// "func" already consumed
 	obj := p.parseExportedName(ast.Fun)
-	obj.Type = p.parseFuncType()
+	obj.Type = p.parseSignature()
 }
 
 
@@ -722,14 +766,11 @@ func (p *gcParser) parseFuncDecl() {
 //
 func (p *gcParser) parseMethodDecl() {
 	// "func" already consumed
-	scope := ast.NewScope(nil) // method scope
 	p.expect('(')
-	p.parseParameter(scope, nil) // receiver
+	p.parseParameter() // receiver
 	p.expect(')')
 	p.expect(scanner.Ident)
-	isVariadic := false
-	p.parseSignature(scope, &isVariadic)
-
+	p.parseSignature()
 }
 
 
@@ -763,7 +804,7 @@ func (p *gcParser) parseDecl() {
 // Export        = "PackageClause { Decl } "$$" .
 // PackageClause = "package" identifier [ "safe" ] "\n" .
 //
-func (p *gcParser) parseExport() (string, *ast.Scope) {
+func (p *gcParser) parseExport() *ast.Object {
 	p.expectKeyword("package")
 	name := p.expect(scanner.Ident)
 	if p.tok != '\n' {
@@ -774,6 +815,11 @@ func (p *gcParser) parseExport() (string, *ast.Scope) {
 	}
 	p.expect('\n')
 
+	assert(p.imports[p.id] == nil)
+	pkg := ast.NewObj(ast.Pkg, name)
+	pkg.Data = ast.NewScope(nil)
+	p.imports[p.id] = pkg
+
 	for p.tok != '$' && p.tok != scanner.EOF {
 		p.parseDecl()
 	}
@@ -788,5 +834,5 @@ func (p *gcParser) parseExport() (string, *ast.Scope) {
 		p.errorf("expected no scanner errors, got %d", n)
 	}
 
-	return name, p.scope
+	return pkg
 }
diff --git a/src/pkg/go/types/gcimporter_test.go b/src/pkg/go/types/gcimporter_test.go
index 556e761df..10240add5 100644
--- a/src/pkg/go/types/gcimporter_test.go
+++ b/src/pkg/go/types/gcimporter_test.go
@@ -6,6 +6,7 @@ package types
 
 import (
 	"exec"
+	"go/ast"
 	"io/ioutil"
 	"path/filepath"
 	"runtime"
@@ -36,29 +37,23 @@ func init() {
 
 
 func compile(t *testing.T, dirname, filename string) {
-	cmd, err := exec.Run(gcPath, []string{gcPath, filename}, nil, dirname, exec.DevNull, exec.Pipe, exec.MergeWithStdout)
+	cmd := exec.Command(gcPath, filename)
+	cmd.Dir = dirname
+	out, err := cmd.CombinedOutput()
 	if err != nil {
 		t.Errorf("%s %s failed: %s", gcName, filename, err)
 		return
 	}
-	defer cmd.Close()
-
-	msg, err := cmd.Wait(0)
-	if err != nil {
-		t.Errorf("%s %s failed: %s", gcName, filename, err)
-		return
-	}
-
-	if !msg.Exited() || msg.ExitStatus() != 0 {
-		t.Errorf("%s %s failed: exit status = %d", gcName, filename, msg.ExitStatus())
-		output, _ := ioutil.ReadAll(cmd.Stdout)
-		t.Log(string(output))
-	}
+	t.Logf("%s", string(out))
 }
 
 
+// Use the same global imports map for all tests. The effect is
+// as if all tested packages were imported into a single package.
+var imports = make(map[string]*ast.Object)
+
 func testPath(t *testing.T, path string) bool {
-	_, _, err := GcImporter(path)
+	_, err := GcImporter(imports, path)
 	if err != nil {
 		t.Errorf("testPath(%s): %s", path, err)
 		return false
diff --git a/src/pkg/go/types/testdata/exports.go b/src/pkg/go/types/testdata/exports.go
index 13efe012a..1de2e00ad 100644
--- a/src/pkg/go/types/testdata/exports.go
+++ b/src/pkg/go/types/testdata/exports.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// This file is used to generate a .6 object file which
+// This file is used to generate an object file which
 // serves as test file for gcimporter_test.go.
 
 package exports
@@ -14,13 +14,13 @@ import (
 
 const (
 	C0 int = 0
-	C1 = 3.14159265
-	C2 = 2.718281828i
-	C3 = -123.456e-789
-	C4 = +123.456E+789
-	C5 = 1234i
-	C6 = "foo\n"
-	C7 = `bar\n`
+	C1     = 3.14159265
+	C2     = 2.718281828i
+	C3     = -123.456e-789
+	C4     = +123.456E+789
+	C5     = 1234i
+	C6     = "foo\n"
+	C7     = `bar\n`
 )
 
 
diff --git a/src/pkg/go/types/testdata/test0.src b/src/pkg/go/types/testdata/test0.src
new file mode 100644
index 000000000..84a1abe27
--- /dev/null
+++ b/src/pkg/go/types/testdata/test0.src
@@ -0,0 +1,154 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// type declarations
+
+package test0
+
+import "unsafe"
+
+const pi = 3.1415
+
+type (
+	N undeclared /* ERROR "undeclared" */
+	B bool
+	I int32
+	A [10]P
+	T struct {
+		x, y P
+	}
+	P *T
+	R (*R)
+	F func(A) I
+	Y interface {
+		f(A) I
+	}
+	S [](((P)))
+	M map[I]F
+	C chan<- I
+)
+
+
+type (
+	p1 pi /* ERROR "not a package" */ .foo
+	p2 unsafe.Pointer
+)
+
+
+type (
+	Pi pi /* ERROR "not a type" */
+
+	a /* DISABLED "illegal cycle" */ a
+	a /* ERROR "redeclared" */ int
+
+	// where the cycle error appears depends on the
+	// order in which declarations are processed
+	// (which depends on the order in which a map
+	// is iterated through)
+	b c
+	c /* DISABLED "illegal cycle" */ d
+	d e
+	e b
+
+	t *t
+
+	U V
+	V *W
+	W U
+
+	P1 *S2
+	P2 P1
+
+	S0 struct {
+	}
+	S1 struct {
+		a, b, c int
+		u, v, a /* ERROR "redeclared" */ float32
+	}
+	S2 struct {
+		U // anonymous field
+		// TODO(gri) recognize double-declaration below
+		// U /* ERROR "redeclared" */ int
+	}
+	S3 struct {
+		x S2
+	}
+	S4/* DISABLED "illegal cycle" */ struct {
+		S4
+	}
+	S5 struct {
+		S6
+	}
+	S6 /* DISABLED "illegal cycle" */ struct {
+		field S7
+	}
+	S7 struct {
+		S5
+	}
+
+	L1 []L1
+	L2 []int
+
+	A1 [10]int
+	A2 /* DISABLED "illegal cycle" */ [10]A2
+	A3 /* DISABLED "illegal cycle" */ [10]struct {
+		x A4
+	}
+	A4 [10]A3
+
+	F1 func()
+	F2 func(x, y, z float32)
+	F3 func(x, y, x /* ERROR "redeclared" */ float32)
+	F4 func() (x, y, x /* ERROR "redeclared" */ float32)
+	F5 func(x int) (x /* ERROR "redeclared" */ float32)
+	F6 func(x ...int)
+
+	I1 interface{}
+	I2 interface {
+		m1()
+	}
+	I3 interface {
+		m1()
+		m1 /* ERROR "redeclared" */ ()
+	}
+	I4 interface {
+		m1(x, y, x /* ERROR "redeclared" */ float32)
+		m2() (x, y, x /* ERROR "redeclared" */ float32)
+		m3(x int) (x /* ERROR "redeclared" */ float32)
+	}
+	I5 interface {
+		m1(I5)
+	}
+	I6 interface {
+		S0 /* ERROR "non-interface" */
+	}
+	I7 interface {
+		I1
+		I1
+	}
+	I8 /* DISABLED "illegal cycle" */ interface {
+		I8
+	}
+	I9 /* DISABLED "illegal cycle" */ interface {
+		I10
+	}
+	I10 interface {
+		I11
+	}
+	I11 interface {
+		I9
+	}
+
+	C1 chan int
+	C2 <-chan int
+	C3 chan<- C3
+	C4 chan C5
+	C5 chan C6
+	C6 chan C4
+
+	M1 map[Last]string
+	M2 map[string]M2
+
+	Last int
+)
diff --git a/src/pkg/go/types/types.go b/src/pkg/go/types/types.go
index 2ee645d98..10b0145b8 100644
--- a/src/pkg/go/types/types.go
+++ b/src/pkg/go/types/types.go
@@ -7,7 +7,10 @@
 //
 package types
 
-import "go/ast"
+import (
+	"go/ast"
+	"sort"
+)
 
 
 // All types implement the Type interface.
@@ -23,6 +26,13 @@ type ImplementsType struct{}
 func (t *ImplementsType) isType() {}
 
 
+// A Bad type is a non-nil placeholder type when we don't know a type.
+type Bad struct {
+	ImplementsType
+	Msg string // for better error reporting/debugging
+}
+
+
 // A Basic represents a (unnamed) basic type.
 type Basic struct {
 	ImplementsType
@@ -46,9 +56,15 @@ type Slice struct {
 
 
 // A Struct represents a struct type struct{...}.
+// Anonymous fields are represented by objects with empty names.
 type Struct struct {
 	ImplementsType
-	// TODO(gri) need to remember fields.
+	Fields ObjList  // struct fields; or nil
+	Tags   []string // corresponding tags; or nil
+	// TODO(gri) This type needs some rethinking:
+	// - at the moment anonymous fields are marked with "" object names,
+	//   and their names have to be reconstructed
+	// - there is no scope for fast lookup (but the parser creates one)
 }
 
 
@@ -60,17 +76,20 @@ type Pointer struct {
 
 
 // A Func represents a function type func(...) (...).
+// Unnamed parameters are represented by objects with empty names.
 type Func struct {
 	ImplementsType
-	IsVariadic bool
-	// TODO(gri) need to remember parameters.
+	Recv       *ast.Object // nil if not a method
+	Params     ObjList     // (incoming) parameters from left to right; or nil
+	Results    ObjList     // (outgoing) results from left to right; or nil
+	IsVariadic bool        // true if the last parameter's type is of the form ...T
 }
 
 
 // An Interface represents an interface type interface{...}.
 type Interface struct {
 	ImplementsType
-	// TODO(gri) need to remember methods.
+	Methods ObjList // interface methods sorted by name; or nil
 }
 
 
@@ -112,11 +131,143 @@ func Deref(typ Type) Type {
 func Underlying(typ Type) Type {
 	if typ, ok := typ.(*Name); ok {
 		utyp := typ.Underlying
-		if _, ok := utyp.(*Basic); ok {
-			return typ
+		if _, ok := utyp.(*Basic); !ok {
+			return utyp
 		}
-		return utyp
-
+		// the underlying type of a type name referring
+		// to an (untyped) basic type is the basic type
+		// name
 	}
 	return typ
 }
+
+
+// An ObjList represents an ordered (in some fashion) list of objects.
+type ObjList []*ast.Object
+
+// ObjList implements sort.Interface.
+func (list ObjList) Len() int           { return len(list) }
+func (list ObjList) Less(i, j int) bool { return list[i].Name < list[j].Name }
+func (list ObjList) Swap(i, j int)      { list[i], list[j] = list[j], list[i] }
+
+// Sort sorts an object list by object name.
+func (list ObjList) Sort() { sort.Sort(list) }
+
+
+// identicalTypes returns true if both lists a and b have the
+// same length and corresponding objects have identical types.
+func identicalTypes(a, b ObjList) bool {
+	if len(a) == len(b) {
+		for i, x := range a {
+			y := b[i]
+			if !Identical(x.Type.(Type), y.Type.(Type)) {
+				return false
+			}
+		}
+		return true
+	}
+	return false
+}
+
+
+// Identical returns true if two types are identical.
+func Identical(x, y Type) bool {
+	if x == y {
+		return true
+	}
+
+	switch x := x.(type) {
+	case *Bad:
+		// A Bad type is always identical to any other type
+		// (to avoid spurious follow-up errors).
+		return true
+
+	case *Basic:
+		if y, ok := y.(*Basic); ok {
+			panic("unimplemented")
+			_ = y
+		}
+
+	case *Array:
+		// Two array types are identical if they have identical element types
+		// and the same array length.
+		if y, ok := y.(*Array); ok {
+			return x.Len == y.Len && Identical(x.Elt, y.Elt)
+		}
+
+	case *Slice:
+		// Two slice types are identical if they have identical element types.
+		if y, ok := y.(*Slice); ok {
+			return Identical(x.Elt, y.Elt)
+		}
+
+	case *Struct:
+		// Two struct types are identical if they have the same sequence of fields,
+		// and if corresponding fields have the same names, and identical types,
+		// and identical tags. Two anonymous fields are considered to have the same
+		// name. Lower-case field names from different packages are always different.
+		if y, ok := y.(*Struct); ok {
+			// TODO(gri) handle structs from different packages
+			if identicalTypes(x.Fields, y.Fields) {
+				for i, f := range x.Fields {
+					g := y.Fields[i]
+					if f.Name != g.Name || x.Tags[i] != y.Tags[i] {
+						return false
+					}
+				}
+				return true
+			}
+		}
+
+	case *Pointer:
+		// Two pointer types are identical if they have identical base types.
+		if y, ok := y.(*Pointer); ok {
+			return Identical(x.Base, y.Base)
+		}
+
+	case *Func:
+		// Two function types are identical if they have the same number of parameters
+		// and result values, corresponding parameter and result types are identical,
+		// and either both functions are variadic or neither is. Parameter and result
+		// names are not required to match.
+		if y, ok := y.(*Func); ok {
+			return identicalTypes(x.Params, y.Params) &&
+				identicalTypes(x.Results, y.Results) &&
+				x.IsVariadic == y.IsVariadic
+		}
+
+	case *Interface:
+		// Two interface types are identical if they have the same set of methods with
+		// the same names and identical function types. Lower-case method names from
+		// different packages are always different. The order of the methods is irrelevant.
+		if y, ok := y.(*Interface); ok {
+			return identicalTypes(x.Methods, y.Methods) // methods are sorted
+		}
+
+	case *Map:
+		// Two map types are identical if they have identical key and value types.
+		if y, ok := y.(*Map); ok {
+			return Identical(x.Key, y.Key) && Identical(x.Elt, y.Elt)
+		}
+
+	case *Chan:
+		// Two channel types are identical if they have identical value types
+		// and the same direction.
+		if y, ok := y.(*Chan); ok {
+			return x.Dir == y.Dir && Identical(x.Elt, y.Elt)
+		}
+
+	case *Name:
+		// Two named types are identical if their type names originate
+		// in the same type declaration.
+		if y, ok := y.(*Name); ok {
+			return x.Obj == y.Obj ||
+				// permit bad objects to be equal to avoid
+				// follow up errors
+				x.Obj != nil && x.Obj.Kind == ast.Bad ||
+				y.Obj != nil && y.Obj.Kind == ast.Bad
+		}
+	}
+
+	return false
+}
diff --git a/src/pkg/go/types/universe.go b/src/pkg/go/types/universe.go
index 2a54a8ac1..96005cff5 100644
--- a/src/pkg/go/types/universe.go
+++ b/src/pkg/go/types/universe.go
@@ -11,9 +11,9 @@ import "go/ast"
 
 
 var (
-	scope, // current scope to use for initialization
-	Universe,
-	Unsafe *ast.Scope
+	scope    *ast.Scope // current scope to use for initialization
+	Universe *ast.Scope
+	Unsafe   *ast.Object // package unsafe
 )
 
 
@@ -56,8 +56,8 @@ var (
 
 
 func init() {
-	Universe = ast.NewScope(nil)
-	scope = Universe
+	scope = ast.NewScope(nil)
+	Universe = scope
 
 	Bool = defType("bool")
 	defType("byte") // TODO(gri) should be an alias for uint8
@@ -98,8 +98,10 @@ func init() {
 	defFun("real")
 	defFun("recover")
 
-	Unsafe = ast.NewScope(nil)
-	scope = Unsafe
+	scope = ast.NewScope(nil)
+	Unsafe = ast.NewObj(ast.Pkg, "unsafe")
+	Unsafe.Data = scope
+
 	defType("Pointer")
 
 	defFun("Alignof")