1 files changed, 188 insertions, 0 deletions
diff --git a/src/pkg/go/ast/resolve.go b/src/pkg/go/ast/resolve.go
new file mode 100644
index 000000000..fddc3baab
--- /dev/null
+++ b/src/pkg/go/ast/resolve.go
@@ -0,0 +1,188 @@
+// 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 NewPackage.
+
+package ast
+
+import (
+	"fmt"
+	"go/scanner"
+	"go/token"
+	"os"
+)
+
+
+type pkgBuilder struct {
+	scanner.ErrorVector
+	fset *token.FileSet
+}
+
+
+func (p *pkgBuilder) error(pos token.Pos, msg string) {
+	p.Error(p.fset.Position(pos), msg)
+}
+
+
+func (p *pkgBuilder) errorf(pos token.Pos, format string, args ...interface{}) {
+	p.error(pos, fmt.Sprintf(format, args...))
+}
+
+
+func (p *pkgBuilder) declare(scope, altScope *Scope, obj *Object) {
+	alt := scope.Insert(obj)
+	if alt == nil && altScope != nil {
+		// see if there is a conflicting declaration in altScope
+		alt = altScope.Lookup(obj.Name)
+	}
+	if alt != nil {
+		prevDecl := ""
+		if pos := alt.Pos(); pos.IsValid() {
+			prevDecl = fmt.Sprintf("\n\tprevious declaration at %s", p.fset.Position(pos))
+		}
+		p.error(obj.Pos(), fmt.Sprintf("%s redeclared in this block%s", obj.Name, prevDecl))
+	}
+}
+
+
+func resolve(scope *Scope, ident *Ident) bool {
+	for ; scope != nil; scope = scope.Outer {
+		if obj := scope.Lookup(ident.Name); obj != nil {
+			ident.Obj = obj
+			return true
+		}
+	}
+	return false
+}
+
+
+// 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)
+
+
+// NewPackage creates a new Package node from a set of File nodes. It resolves
+// unresolved identifiers across files and updates each file's Unresolved list
+// accordingly. If a non-nil importer and universe scope are provided, they are
+// 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.
+// 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) {
+	var p pkgBuilder
+	p.fset = fset
+
+	// complete package scope
+	pkgName := ""
+	pkgScope := NewScope(universe)
+	for _, file := range files {
+		// package names must match
+		switch name := file.Name.Name; {
+		case pkgName == "":
+			pkgName = name
+		case name != pkgName:
+			p.errorf(file.Package, "package %s; expected %s", name, pkgName)
+			continue // ignore this file
+		}
+
+		// collect top-level file objects in package scope
+		for _, obj := range file.Scope.Objects {
+			p.declare(pkgScope, nil, obj)
+		}
+	}
+
+	// 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)
+
+	// complete file scopes with imports and resolve identifiers
+	for _, file := range files {
+		// ignore file if it belongs to a different package
+		// (error has already been reported)
+		if file.Name.Name != pkgName {
+			continue
+		}
+
+		// build file scope by processing all imports
+		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.
+			}
+			// local name overrides imported package 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 {
+					p.declare(fileScope, pkgScope, obj)
+				}
+			} else {
+				// declare imported package object in file scope
+				obj := NewObj(Pkg, name)
+				obj.Decl = spec
+				p.declare(fileScope, pkgScope, obj)
+			}
+		}
+
+		// resolve identifiers
+		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)
+			pkgScope.Outer = nil
+		}
+		i := 0
+		for _, ident := range file.Unresolved {
+			if !resolve(fileScope, ident) {
+				p.errorf(ident.Pos(), "undeclared name: %s", ident.Name)
+				file.Unresolved[i] = ident
+				i++
+			}
+
+		}
+		file.Unresolved = file.Unresolved[0:i]
+		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)
+}