Imported Upstream version 60

1 files changed, 0 insertions, 2015 deletions

diff --git a/src/pkg/exp/eval/expr.go b/src/pkg/exp/eval/expr.go
deleted file mode 100644
index 14a0659b6..000000000
--- a/src/pkg/exp/eval/expr.go
+++ /dev/null
@@ -1,2015 +0,0 @@
-// 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 eval
-
-import (
-	"big"
-	"fmt"
-	"go/ast"
-	"go/token"
-	"log"
-	"strconv"
-	"strings"
-	"os"
-)
-
-var (
-	idealZero = big.NewInt(0)
-	idealOne  = big.NewInt(1)
-)
-
-// An expr is the result of compiling an expression.  It stores the
-// type of the expression and its evaluator function.
-type expr struct {
-	*exprInfo
-	t Type
-
-	// Evaluate this node as the given type.
-	eval interface{}
-
-	// Map index expressions permit special forms of assignment,
-	// for which we need to know the Map and key.
-	evalMapValue func(t *Thread) (Map, interface{})
-
-	// Evaluate to the "address of" this value; that is, the
-	// settable Value object.  nil for expressions whose address
-	// cannot be taken.
-	evalAddr func(t *Thread) Value
-
-	// Execute this expression as a statement.  Only expressions
-	// that are valid expression statements should set this.
-	exec func(t *Thread)
-
-	// If this expression is a type, this is its compiled type.
-	// This is only permitted in the function position of a call
-	// expression.  In this case, t should be nil.
-	valType Type
-
-	// A short string describing this expression for error
-	// messages.
-	desc string
-}
-
-// exprInfo stores information needed to compile any expression node.
-// Each expr also stores its exprInfo so further expressions can be
-// compiled from it.
-type exprInfo struct {
-	*compiler
-	pos token.Pos
-}
-
-func (a *exprInfo) newExpr(t Type, desc string) *expr {
-	return &expr{exprInfo: a, t: t, desc: desc}
-}
-
-func (a *exprInfo) diag(format string, args ...interface{}) {
-	a.diagAt(a.pos, format, args...)
-}
-
-func (a *exprInfo) diagOpType(op token.Token, vt Type) {
-	a.diag("illegal operand type for '%v' operator\n\t%v", op, vt)
-}
-
-func (a *exprInfo) diagOpTypes(op token.Token, lt Type, rt Type) {
-	a.diag("illegal operand types for '%v' operator\n\t%v\n\t%v", op, lt, rt)
-}
-
-/*
- * Common expression manipulations
- */
-
-// a.convertTo(t) converts the value of the analyzed expression a,
-// which must be a constant, ideal number, to a new analyzed
-// expression with a constant value of type t.
-//
-// TODO(austin) Rename to resolveIdeal or something?
-func (a *expr) convertTo(t Type) *expr {
-	if !a.t.isIdeal() {
-		log.Panicf("attempted to convert from %v, expected ideal", a.t)
-	}
-
-	var rat *big.Rat
-
-	// XXX(Spec)  The spec says "It is erroneous".
-	//
-	// It is an error to assign a value with a non-zero fractional
-	// part to an integer, or if the assignment would overflow or
-	// underflow, or in general if the value cannot be represented
-	// by the type of the variable.
-	switch a.t {
-	case IdealFloatType:
-		rat = a.asIdealFloat()()
-		if t.isInteger() && !rat.IsInt() {
-			a.diag("constant %v truncated to integer", rat.FloatString(6))
-			return nil
-		}
-	case IdealIntType:
-		i := a.asIdealInt()()
-		rat = new(big.Rat).SetInt(i)
-	default:
-		log.Panicf("unexpected ideal type %v", a.t)
-	}
-
-	// Check bounds
-	if t, ok := t.lit().(BoundedType); ok {
-		if rat.Cmp(t.minVal()) < 0 {
-			a.diag("constant %v underflows %v", rat.FloatString(6), t)
-			return nil
-		}
-		if rat.Cmp(t.maxVal()) > 0 {
-			a.diag("constant %v overflows %v", rat.FloatString(6), t)
-			return nil
-		}
-	}
-
-	// Convert rat to type t.
-	res := a.newExpr(t, a.desc)
-	switch t := t.lit().(type) {
-	case *uintType:
-		n, d := rat.Num(), rat.Denom()
-		f := new(big.Int).Quo(n, d)
-		f = f.Abs(f)
-		v := uint64(f.Int64())
-		res.eval = func(*Thread) uint64 { return v }
-	case *intType:
-		n, d := rat.Num(), rat.Denom()
-		f := new(big.Int).Quo(n, d)
-		v := f.Int64()
-		res.eval = func(*Thread) int64 { return v }
-	case *idealIntType:
-		n, d := rat.Num(), rat.Denom()
-		f := new(big.Int).Quo(n, d)
-		res.eval = func() *big.Int { return f }
-	case *floatType:
-		n, d := rat.Num(), rat.Denom()
-		v := float64(n.Int64()) / float64(d.Int64())
-		res.eval = func(*Thread) float64 { return v }
-	case *idealFloatType:
-		res.eval = func() *big.Rat { return rat }
-	default:
-		log.Panicf("cannot convert to type %T", t)
-	}
-
-	return res
-}
-
-// convertToInt converts this expression to an integer, if possible,
-// or produces an error if not.  This accepts ideal ints, uints, and
-// ints.  If max is not -1, produces an error if possible if the value
-// exceeds max.  If negErr is not "", produces an error if possible if
-// the value is negative.
-func (a *expr) convertToInt(max int64, negErr string, errOp string) *expr {
-	switch a.t.lit().(type) {
-	case *idealIntType:
-		val := a.asIdealInt()()
-		if negErr != "" && val.Sign() < 0 {
-			a.diag("negative %s: %s", negErr, val)
-			return nil
-		}
-		bound := max
-		if negErr == "slice" {
-			bound++
-		}
-		if max != -1 && val.Cmp(big.NewInt(bound)) >= 0 {
-			a.diag("index %s exceeds length %d", val, max)
-			return nil
-		}
-		return a.convertTo(IntType)
-
-	case *uintType:
-		// Convert to int
-		na := a.newExpr(IntType, a.desc)
-		af := a.asUint()
-		na.eval = func(t *Thread) int64 { return int64(af(t)) }
-		return na
-
-	case *intType:
-		// Good as is
-		return a
-	}
-
-	a.diag("illegal operand type for %s\n\t%v", errOp, a.t)
-	return nil
-}
-
-// derefArray returns an expression of array type if the given
-// expression is a *array type.  Otherwise, returns the given
-// expression.
-func (a *expr) derefArray() *expr {
-	if pt, ok := a.t.lit().(*PtrType); ok {
-		if _, ok := pt.Elem.lit().(*ArrayType); ok {
-			deref := a.compileStarExpr(a)
-			if deref == nil {
-				log.Panicf("failed to dereference *array")
-			}
-			return deref
-		}
-	}
-	return a
-}
-
-/*
- * Assignments
- */
-
-// An assignCompiler compiles assignment operations.  Anything other
-// than short declarations should use the compileAssign wrapper.
-//
-// There are three valid types of assignment:
-// 1) T = T
-//    Assigning a single expression with single-valued type to a
-//    single-valued type.
-// 2) MT = T, T, ...
-//    Assigning multiple expressions with single-valued types to a
-//    multi-valued type.
-// 3) MT = MT
-//    Assigning a single expression with multi-valued type to a
-//    multi-valued type.
-type assignCompiler struct {
-	*compiler
-	pos token.Pos
-	// The RHS expressions.  This may include nil's for
-	// expressions that failed to compile.
-	rs []*expr
-	// The (possibly unary) MultiType of the RHS.
-	rmt *MultiType
-	// Whether this is an unpack assignment (case 3).
-	isUnpack bool
-	// Whether map special assignment forms are allowed.
-	allowMap bool
-	// Whether this is a "r, ok = a[x]" assignment.
-	isMapUnpack bool
-	// The operation name to use in error messages, such as
-	// "assignment" or "function call".
-	errOp string
-	// The name to use for positions in error messages, such as
-	// "argument".
-	errPosName string
-}
-
-// Type check the RHS of an assignment, returning a new assignCompiler
-// and indicating if the type check succeeded.  This always returns an
-// assignCompiler with rmt set, but if type checking fails, slots in
-// the MultiType may be nil.  If rs contains nil's, type checking will
-// fail and these expressions given a nil type.
-func (a *compiler) checkAssign(pos token.Pos, rs []*expr, errOp, errPosName string) (*assignCompiler, bool) {
-	c := &assignCompiler{
-		compiler:   a,
-		pos:        pos,
-		rs:         rs,
-		errOp:      errOp,
-		errPosName: errPosName,
-	}
-
-	// Is this an unpack?
-	if len(rs) == 1 && rs[0] != nil {
-		if rmt, isUnpack := rs[0].t.(*MultiType); isUnpack {
-			c.rmt = rmt
-			c.isUnpack = true
-			return c, true
-		}
-	}
-
-	// Create MultiType for RHS and check that all RHS expressions
-	// are single-valued.
-	rts := make([]Type, len(rs))
-	ok := true
-	for i, r := range rs {
-		if r == nil {
-			ok = false
-			continue
-		}
-
-		if _, isMT := r.t.(*MultiType); isMT {
-			r.diag("multi-valued expression not allowed in %s", errOp)
-			ok = false
-			continue
-		}
-
-		rts[i] = r.t
-	}
-
-	c.rmt = NewMultiType(rts)
-	return c, ok
-}
-
-func (a *assignCompiler) allowMapForms(nls int) {
-	a.allowMap = true
-
-	// Update unpacking info if this is r, ok = a[x]
-	if nls == 2 && len(a.rs) == 1 && a.rs[0] != nil && a.rs[0].evalMapValue != nil {
-		a.isUnpack = true
-		a.rmt = NewMultiType([]Type{a.rs[0].t, BoolType})
-		a.isMapUnpack = true
-	}
-}
-
-// compile type checks and compiles an assignment operation, returning
-// a function that expects an l-value and the frame in which to
-// evaluate the RHS expressions.  The l-value must have exactly the
-// type given by lt.  Returns nil if type checking fails.
-func (a *assignCompiler) compile(b *block, lt Type) func(Value, *Thread) {
-	lmt, isMT := lt.(*MultiType)
-	rmt, isUnpack := a.rmt, a.isUnpack
-
-	// Create unary MultiType for single LHS
-	if !isMT {
-		lmt = NewMultiType([]Type{lt})
-	}
-
-	// Check that the assignment count matches
-	lcount := len(lmt.Elems)
-	rcount := len(rmt.Elems)
-	if lcount != rcount {
-		msg := "not enough"
-		pos := a.pos
-		if rcount > lcount {
-			msg = "too many"
-			if lcount > 0 {
-				pos = a.rs[lcount-1].pos
-			}
-		}
-		a.diagAt(pos, "%s %ss for %s\n\t%s\n\t%s", msg, a.errPosName, a.errOp, lt, rmt)
-		return nil
-	}
-
-	bad := false
-
-	// If this is an unpack, create a temporary to store the
-	// multi-value and replace the RHS with expressions to pull
-	// out values from the temporary.  Technically, this is only
-	// necessary when we need to perform assignment conversions.
-	var effect func(*Thread)
-	if isUnpack {
-		// This leaks a slot, but is definitely safe.
-		temp := b.DefineTemp(a.rmt)
-		tempIdx := temp.Index
-		if tempIdx < 0 {
-			panic(fmt.Sprintln("tempidx", tempIdx))
-		}
-		if a.isMapUnpack {
-			rf := a.rs[0].evalMapValue
-			vt := a.rmt.Elems[0]
-			effect = func(t *Thread) {
-				m, k := rf(t)
-				v := m.Elem(t, k)
-				found := boolV(true)
-				if v == nil {
-					found = boolV(false)
-					v = vt.Zero()
-				}
-				t.f.Vars[tempIdx] = multiV([]Value{v, &found})
-			}
-		} else {
-			rf := a.rs[0].asMulti()
-			effect = func(t *Thread) { t.f.Vars[tempIdx] = multiV(rf(t)) }
-		}
-		orig := a.rs[0]
-		a.rs = make([]*expr, len(a.rmt.Elems))
-		for i, t := range a.rmt.Elems {
-			if t.isIdeal() {
-				log.Panicf("Right side of unpack contains ideal: %s", rmt)
-			}
-			a.rs[i] = orig.newExpr(t, orig.desc)
-			index := i
-			a.rs[i].genValue(func(t *Thread) Value { return t.f.Vars[tempIdx].(multiV)[index] })
-		}
-	}
-	// Now len(a.rs) == len(a.rmt) and we've reduced any unpacking
-	// to multi-assignment.
-
-	// TODO(austin) Deal with assignment special cases.
-
-	// Values of any type may always be assigned to variables of
-	// compatible static type.
-	for i, lt := range lmt.Elems {
-		rt := rmt.Elems[i]
-
-		// When [an ideal is] (used in an expression) assigned
-		// to a variable or typed constant, the destination
-		// must be able to represent the assigned value.
-		if rt.isIdeal() {
-			a.rs[i] = a.rs[i].convertTo(lmt.Elems[i])
-			if a.rs[i] == nil {
-				bad = true
-				continue
-			}
-			rt = a.rs[i].t
-		}
-
-		// A pointer p to an array can be assigned to a slice
-		// variable v with compatible element type if the type
-		// of p or v is unnamed.
-		if rpt, ok := rt.lit().(*PtrType); ok {
-			if at, ok := rpt.Elem.lit().(*ArrayType); ok {
-				if lst, ok := lt.lit().(*SliceType); ok {
-					if lst.Elem.compat(at.Elem, false) && (rt.lit() == Type(rt) || lt.lit() == Type(lt)) {
-						rf := a.rs[i].asPtr()
-						a.rs[i] = a.rs[i].newExpr(lt, a.rs[i].desc)
-						len := at.Len
-						a.rs[i].eval = func(t *Thread) Slice { return Slice{rf(t).(ArrayValue), len, len} }
-						rt = a.rs[i].t
-					}
-				}
-			}
-		}
-
-		if !lt.compat(rt, false) {
-			if len(a.rs) == 1 {
-				a.rs[0].diag("illegal operand types for %s\n\t%v\n\t%v", a.errOp, lt, rt)
-			} else {
-				a.rs[i].diag("illegal operand types in %s %d of %s\n\t%v\n\t%v", a.errPosName, i+1, a.errOp, lt, rt)
-			}
-			bad = true
-		}
-	}
-	if bad {
-		return nil
-	}
-
-	// Compile
-	if !isMT {
-		// Case 1
-		return genAssign(lt, a.rs[0])
-	}
-	// Case 2 or 3
-	as := make([]func(lv Value, t *Thread), len(a.rs))
-	for i, r := range a.rs {
-		as[i] = genAssign(lmt.Elems[i], r)
-	}
-	return func(lv Value, t *Thread) {
-		if effect != nil {
-			effect(t)
-		}
-		lmv := lv.(multiV)
-		for i, a := range as {
-			a(lmv[i], t)
-		}
-	}
-}
-
-// compileAssign compiles an assignment operation without the full
-// generality of an assignCompiler.  See assignCompiler for a
-// description of the arguments.
-func (a *compiler) compileAssign(pos token.Pos, b *block, lt Type, rs []*expr, errOp, errPosName string) func(Value, *Thread) {
-	ac, ok := a.checkAssign(pos, rs, errOp, errPosName)
-	if !ok {
-		return nil
-	}
-	return ac.compile(b, lt)
-}
-
-/*
- * Expression compiler
- */
-
-// An exprCompiler stores information used throughout the compilation
-// of a single expression.  It does not embed funcCompiler because
-// expressions can appear at top level.
-type exprCompiler struct {
-	*compiler
-	// The block this expression is being compiled in.
-	block *block
-	// Whether this expression is used in a constant context.
-	constant bool
-}
-
-// compile compiles an expression AST.  callCtx should be true if this
-// AST is in the function position of a function call node; it allows
-// the returned expression to be a type or a built-in function (which
-// otherwise result in errors).
-func (a *exprCompiler) compile(x ast.Expr, callCtx bool) *expr {
-	ei := &exprInfo{a.compiler, x.Pos()}
-
-	switch x := x.(type) {
-	// Literals
-	case *ast.BasicLit:
-		switch x.Kind {
-		case token.INT:
-			return ei.compileIntLit(string(x.Value))
-		case token.FLOAT:
-			return ei.compileFloatLit(string(x.Value))
-		case token.CHAR:
-			return ei.compileCharLit(string(x.Value))
-		case token.STRING:
-			return ei.compileStringLit(string(x.Value))
-		default:
-			log.Panicf("unexpected basic literal type %v", x.Kind)
-		}
-
-	case *ast.CompositeLit:
-		goto notimpl
-
-	case *ast.FuncLit:
-		decl := ei.compileFuncType(a.block, x.Type)
-		if decl == nil {
-			// TODO(austin) Try compiling the body,
-			// perhaps with dummy argument definitions
-			return nil
-		}
-		fn := ei.compileFunc(a.block, decl, x.Body)
-		if fn == nil {
-			return nil
-		}
-		if a.constant {
-			a.diagAt(x.Pos(), "function literal used in constant expression")
-			return nil
-		}
-		return ei.compileFuncLit(decl, fn)
-
-	// Types
-	case *ast.ArrayType:
-		// TODO(austin) Use a multi-type case
-		goto typeexpr
-
-	case *ast.ChanType:
-		goto typeexpr
-
-	case *ast.Ellipsis:
-		goto typeexpr
-
-	case *ast.FuncType:
-		goto typeexpr
-
-	case *ast.InterfaceType:
-		goto typeexpr
-
-	case *ast.MapType:
-		goto typeexpr
-
-	// Remaining expressions
-	case *ast.BadExpr:
-		// Error already reported by parser
-		a.silentErrors++
-		return nil
-
-	case *ast.BinaryExpr:
-		l, r := a.compile(x.X, false), a.compile(x.Y, false)
-		if l == nil || r == nil {
-			return nil
-		}
-		return ei.compileBinaryExpr(x.Op, l, r)
-
-	case *ast.CallExpr:
-		l := a.compile(x.Fun, true)
-		args := make([]*expr, len(x.Args))
-		bad := false
-		for i, arg := range x.Args {
-			if i == 0 && l != nil && (l.t == Type(makeType) || l.t == Type(newType)) {
-				argei := &exprInfo{a.compiler, arg.Pos()}
-				args[i] = argei.exprFromType(a.compileType(a.block, arg))
-			} else {
-				args[i] = a.compile(arg, false)
-			}
-			if args[i] == nil {
-				bad = true
-			}
-		}
-		if bad || l == nil {
-			return nil
-		}
-		if a.constant {
-			a.diagAt(x.Pos(), "function call in constant context")
-			return nil
-		}
-
-		if l.valType != nil {
-			a.diagAt(x.Pos(), "type conversions not implemented")
-			return nil
-		} else if ft, ok := l.t.(*FuncType); ok && ft.builtin != "" {
-			return ei.compileBuiltinCallExpr(a.block, ft, args)
-		} else {
-			return ei.compileCallExpr(a.block, l, args)
-		}
-
-	case *ast.Ident:
-		return ei.compileIdent(a.block, a.constant, callCtx, x.Name)
-
-	case *ast.IndexExpr:
-		l, r := a.compile(x.X, false), a.compile(x.Index, false)
-		if l == nil || r == nil {
-			return nil
-		}
-		return ei.compileIndexExpr(l, r)
-
-	case *ast.SliceExpr:
-		var lo, hi *expr
-		arr := a.compile(x.X, false)
-		if x.Low == nil {
-			// beginning was omitted, so we need to provide it
-			ei := &exprInfo{a.compiler, x.Pos()}
-			lo = ei.compileIntLit("0")
-		} else {
-			lo = a.compile(x.Low, false)
-		}
-		if x.High == nil {
-			// End was omitted, so we need to compute len(x.X)
-			ei := &exprInfo{a.compiler, x.Pos()}
-			hi = ei.compileBuiltinCallExpr(a.block, lenType, []*expr{arr})
-		} else {
-			hi = a.compile(x.High, false)
-		}
-		if arr == nil || lo == nil || hi == nil {
-			return nil
-		}
-		return ei.compileSliceExpr(arr, lo, hi)
-
-	case *ast.KeyValueExpr:
-		goto notimpl
-
-	case *ast.ParenExpr:
-		return a.compile(x.X, callCtx)
-
-	case *ast.SelectorExpr:
-		v := a.compile(x.X, false)
-		if v == nil {
-			return nil
-		}
-		return ei.compileSelectorExpr(v, x.Sel.Name)
-
-	case *ast.StarExpr:
-		// We pass down our call context because this could be
-		// a pointer type (and thus a type conversion)
-		v := a.compile(x.X, callCtx)
-		if v == nil {
-			return nil
-		}
-		if v.valType != nil {
-			// Turns out this was a pointer type, not a dereference
-			return ei.exprFromType(NewPtrType(v.valType))
-		}
-		return ei.compileStarExpr(v)
-
-	case *ast.StructType:
-		goto notimpl
-
-	case *ast.TypeAssertExpr:
-		goto notimpl
-
-	case *ast.UnaryExpr:
-		v := a.compile(x.X, false)
-		if v == nil {
-			return nil
-		}
-		return ei.compileUnaryExpr(x.Op, v)
-	}
-	log.Panicf("unexpected ast node type %T", x)
-	panic("unreachable")
-
-typeexpr:
-	if !callCtx {
-		a.diagAt(x.Pos(), "type used as expression")
-		return nil
-	}
-	return ei.exprFromType(a.compileType(a.block, x))
-
-notimpl:
-	a.diagAt(x.Pos(), "%T expression node not implemented", x)
-	return nil
-}
-
-func (a *exprInfo) exprFromType(t Type) *expr {
-	if t == nil {
-		return nil
-	}
-	expr := a.newExpr(nil, "type")
-	expr.valType = t
-	return expr
-}
-
-func (a *exprInfo) compileIdent(b *block, constant bool, callCtx bool, name string) *expr {
-	bl, level, def := b.Lookup(name)
-	if def == nil {
-		a.diag("%s: undefined", name)
-		return nil
-	}
-	switch def := def.(type) {
-	case *Constant:
-		expr := a.newExpr(def.Type, "constant")
-		if ft, ok := def.Type.(*FuncType); ok && ft.builtin != "" {
-			// XXX(Spec) I don't think anything says that
-			// built-in functions can't be used as values.
-			if !callCtx {
-				a.diag("built-in function %s cannot be used as a value", ft.builtin)
-				return nil
-			}
-			// Otherwise, we leave the evaluators empty
-			// because this is handled specially
-		} else {
-			expr.genConstant(def.Value)
-		}
-		return expr
-	case *Variable:
-		if constant {
-			a.diag("variable %s used in constant expression", name)
-			return nil
-		}
-		if bl.global {
-			return a.compileGlobalVariable(def)
-		}
-		return a.compileVariable(level, def)
-	case Type:
-		if callCtx {
-			return a.exprFromType(def)
-		}
-		a.diag("type %v used as expression", name)
-		return nil
-	}
-	log.Panicf("name %s has unknown type %T", name, def)
-	panic("unreachable")
-}
-
-func (a *exprInfo) compileVariable(level int, v *Variable) *expr {
-	if v.Type == nil {
-		// Placeholder definition from an earlier error
-		a.silentErrors++
-		return nil
-	}
-	expr := a.newExpr(v.Type, "variable")
-	expr.genIdentOp(level, v.Index)
-	return expr
-}
-
-func (a *exprInfo) compileGlobalVariable(v *Variable) *expr {
-	if v.Type == nil {
-		// Placeholder definition from an earlier error
-		a.silentErrors++
-		return nil
-	}
-	if v.Init == nil {
-		v.Init = v.Type.Zero()
-	}
-	expr := a.newExpr(v.Type, "variable")
-	val := v.Init
-	expr.genValue(func(t *Thread) Value { return val })
-	return expr
-}
-
-func (a *exprInfo) compileIdealInt(i *big.Int, desc string) *expr {
-	expr := a.newExpr(IdealIntType, desc)
-	expr.eval = func() *big.Int { return i }
-	return expr
-}
-
-func (a *exprInfo) compileIntLit(lit string) *expr {
-	i, _ := new(big.Int).SetString(lit, 0)
-	return a.compileIdealInt(i, "integer literal")
-}
-
-func (a *exprInfo) compileCharLit(lit string) *expr {
-	if lit[0] != '\'' {
-		// Caught by parser
-		a.silentErrors++
-		return nil
-	}
-	v, _, tail, err := strconv.UnquoteChar(lit[1:], '\'')
-	if err != nil || tail != "'" {
-		// Caught by parser
-		a.silentErrors++
-		return nil
-	}
-	return a.compileIdealInt(big.NewInt(int64(v)), "character literal")
-}
-
-func (a *exprInfo) compileFloatLit(lit string) *expr {
-	f, ok := new(big.Rat).SetString(lit)
-	if !ok {
-		log.Panicf("malformed float literal %s at %v passed parser", lit, a.pos)
-	}
-	expr := a.newExpr(IdealFloatType, "float literal")
-	expr.eval = func() *big.Rat { return f }
-	return expr
-}
-
-func (a *exprInfo) compileString(s string) *expr {
-	// Ideal strings don't have a named type but they are
-	// compatible with type string.
-
-	// TODO(austin) Use unnamed string type.
-	expr := a.newExpr(StringType, "string literal")
-	expr.eval = func(*Thread) string { return s }
-	return expr
-}
-
-func (a *exprInfo) compileStringLit(lit string) *expr {
-	s, err := strconv.Unquote(lit)
-	if err != nil {
-		a.diag("illegal string literal, %v", err)
-		return nil
-	}
-	return a.compileString(s)
-}
-
-func (a *exprInfo) compileStringList(list []*expr) *expr {
-	ss := make([]string, len(list))
-	for i, s := range list {
-		ss[i] = s.asString()(nil)
-	}
-	return a.compileString(strings.Join(ss, ""))
-}
-
-func (a *exprInfo) compileFuncLit(decl *FuncDecl, fn func(*Thread) Func) *expr {
-	expr := a.newExpr(decl.Type, "function literal")
-	expr.eval = fn
-	return expr
-}
-
-func (a *exprInfo) compileSelectorExpr(v *expr, name string) *expr {
-	// mark marks a field that matches the selector name.  It
-	// tracks the best depth found so far and whether more than
-	// one field has been found at that depth.
-	bestDepth := -1
-	ambig := false
-	amberr := ""
-	mark := func(depth int, pathName string) {
-		switch {
-		case bestDepth == -1 || depth < bestDepth:
-			bestDepth = depth
-			ambig = false
-			amberr = ""
-
-		case depth == bestDepth:
-			ambig = true
-
-		default:
-			log.Panicf("Marked field at depth %d, but already found one at depth %d", depth, bestDepth)
-		}
-		amberr += "\n\t" + pathName[1:]
-	}
-
-	visited := make(map[Type]bool)
-
-	// find recursively searches for the named field, starting at
-	// type t.  If it finds the named field, it returns a function
-	// which takes an expr that represents a value of type 't' and
-	// returns an expr that retrieves the named field.  We delay
-	// expr construction to avoid producing lots of useless expr's
-	// as we search.
-	//
-	// TODO(austin) Now that the expression compiler works on
-	// semantic values instead of AST's, there should be a much
-	// better way of doing this.
-	var find func(Type, int, string) func(*expr) *expr
-	find = func(t Type, depth int, pathName string) func(*expr) *expr {
-		// Don't bother looking if we've found something shallower
-		if bestDepth != -1 && bestDepth < depth {
-			return nil
-		}
-
-		// Don't check the same type twice and avoid loops
-		if visited[t] {
-			return nil
-		}
-		visited[t] = true
-
-		// Implicit dereference
-		deref := false
-		if ti, ok := t.(*PtrType); ok {
-			deref = true
-			t = ti.Elem
-		}
-
-		// If it's a named type, look for methods
-		if ti, ok := t.(*NamedType); ok {
-			_, ok := ti.methods[name]
-			if ok {
-				mark(depth, pathName+"."+name)
-				log.Panic("Methods not implemented")
-			}
-			t = ti.Def
-		}
-
-		// If it's a struct type, check fields and embedded types
-		var builder func(*expr) *expr
-		if t, ok := t.(*StructType); ok {
-			for i, f := range t.Elems {
-				var sub func(*expr) *expr
-				switch {
-				case f.Name == name:
-					mark(depth, pathName+"."+name)
-					sub = func(e *expr) *expr { return e }
-
-				case f.Anonymous:
-					sub = find(f.Type, depth+1, pathName+"."+f.Name)
-					if sub == nil {
-						continue
-					}
-
-				default:
-					continue
-				}
-
-				// We found something.  Create a
-				// builder for accessing this field.
-				ft := f.Type
-				index := i
-				builder = func(parent *expr) *expr {
-					if deref {
-						parent = a.compileStarExpr(parent)
-					}
-					expr := a.newExpr(ft, "selector expression")
-					pf := parent.asStruct()
-					evalAddr := func(t *Thread) Value { return pf(t).Field(t, index) }
-					expr.genValue(evalAddr)
-					return sub(expr)
-				}
-			}
-		}
-
-		return builder
-	}
-
-	builder := find(v.t, 0, "")
-	if builder == nil {
-		a.diag("type %v has no field or method %s", v.t, name)
-		return nil
-	}
-	if ambig {
-		a.diag("field %s is ambiguous in type %v%s", name, v.t, amberr)
-		return nil
-	}
-
-	return builder(v)
-}
-
-func (a *exprInfo) compileSliceExpr(arr, lo, hi *expr) *expr {
-	// Type check object
-	arr = arr.derefArray()
-
-	var at Type
-	var maxIndex int64 = -1
-
-	switch lt := arr.t.lit().(type) {
-	case *ArrayType:
-		at = NewSliceType(lt.Elem)
-		maxIndex = lt.Len
-
-	case *SliceType:
-		at = lt
-
-	case *stringType:
-		at = lt
-
-	default:
-		a.diag("cannot slice %v", arr.t)
-		return nil
-	}
-
-	// Type check index and convert to int
-	// XXX(Spec) It's unclear if ideal floats with no
-	// fractional part are allowed here.  6g allows it.  I
-	// believe that's wrong.
-	lo = lo.convertToInt(maxIndex, "slice", "slice")
-	hi = hi.convertToInt(maxIndex, "slice", "slice")
-	if lo == nil || hi == nil {
-		return nil
-	}
-
-	expr := a.newExpr(at, "slice expression")
-
-	// Compile
-	lof := lo.asInt()
-	hif := hi.asInt()
-	switch lt := arr.t.lit().(type) {
-	case *ArrayType:
-		arrf := arr.asArray()
-		bound := lt.Len
-		expr.eval = func(t *Thread) Slice {
-			arr, lo, hi := arrf(t), lof(t), hif(t)
-			if lo > hi || hi > bound || lo < 0 {
-				t.Abort(SliceError{lo, hi, bound})
-			}
-			return Slice{arr.Sub(lo, bound-lo), hi - lo, bound - lo}
-		}
-
-	case *SliceType:
-		arrf := arr.asSlice()
-		expr.eval = func(t *Thread) Slice {
-			arr, lo, hi := arrf(t), lof(t), hif(t)
-			if lo > hi || hi > arr.Cap || lo < 0 {
-				t.Abort(SliceError{lo, hi, arr.Cap})
-			}
-			return Slice{arr.Base.Sub(lo, arr.Cap-lo), hi - lo, arr.Cap - lo}
-		}
-
-	case *stringType:
-		arrf := arr.asString()
-		// TODO(austin) This pulls over the whole string in a
-		// remote setting, instead of creating a substring backed
-		// by remote memory.
-		expr.eval = func(t *Thread) string {
-			arr, lo, hi := arrf(t), lof(t), hif(t)
-			if lo > hi || hi > int64(len(arr)) || lo < 0 {
-				t.Abort(SliceError{lo, hi, int64(len(arr))})
-			}
-			return arr[lo:hi]
-		}
-
-	default:
-		log.Panicf("unexpected left operand type %T", arr.t.lit())
-	}
-
-	return expr
-}
-
-func (a *exprInfo) compileIndexExpr(l, r *expr) *expr {
-	// Type check object
-	l = l.derefArray()
-
-	var at Type
-	intIndex := false
-	var maxIndex int64 = -1
-
-	switch lt := l.t.lit().(type) {
-	case *ArrayType:
-		at = lt.Elem
-		intIndex = true
-		maxIndex = lt.Len
-
-	case *SliceType:
-		at = lt.Elem
-		intIndex = true
-
-	case *stringType:
-		at = Uint8Type
-		intIndex = true
-
-	case *MapType:
-		at = lt.Elem
-		if r.t.isIdeal() {
-			r = r.convertTo(lt.Key)
-			if r == nil {
-				return nil
-			}
-		}
-		if !lt.Key.compat(r.t, false) {
-			a.diag("cannot use %s as index into %s", r.t, lt)
-			return nil
-		}
-
-	default:
-		a.diag("cannot index into %v", l.t)
-		return nil
-	}
-
-	// Type check index and convert to int if necessary
-	if intIndex {
-		// XXX(Spec) It's unclear if ideal floats with no
-		// fractional part are allowed here.  6g allows it.  I
-		// believe that's wrong.
-		r = r.convertToInt(maxIndex, "index", "index")
-		if r == nil {
-			return nil
-		}
-	}
-
-	expr := a.newExpr(at, "index expression")
-
-	// Compile
-	switch lt := l.t.lit().(type) {
-	case *ArrayType:
-		lf := l.asArray()
-		rf := r.asInt()
-		bound := lt.Len
-		expr.genValue(func(t *Thread) Value {
-			l, r := lf(t), rf(t)
-			if r < 0 || r >= bound {
-				t.Abort(IndexError{r, bound})
-			}
-			return l.Elem(t, r)
-		})
-
-	case *SliceType:
-		lf := l.asSlice()
-		rf := r.asInt()
-		expr.genValue(func(t *Thread) Value {
-			l, r := lf(t), rf(t)
-			if l.Base == nil {
-				t.Abort(NilPointerError{})
-			}
-			if r < 0 || r >= l.Len {
-				t.Abort(IndexError{r, l.Len})
-			}
-			return l.Base.Elem(t, r)
-		})
-
-	case *stringType:
-		lf := l.asString()
-		rf := r.asInt()
-		// TODO(austin) This pulls over the whole string in a
-		// remote setting, instead of just the one character.
-		expr.eval = func(t *Thread) uint64 {
-			l, r := lf(t), rf(t)
-			if r < 0 || r >= int64(len(l)) {
-				t.Abort(IndexError{r, int64(len(l))})
-			}
-			return uint64(l[r])
-		}
-
-	case *MapType:
-		lf := l.asMap()
-		rf := r.asInterface()
-		expr.genValue(func(t *Thread) Value {
-			m := lf(t)
-			k := rf(t)
-			if m == nil {
-				t.Abort(NilPointerError{})
-			}
-			e := m.Elem(t, k)
-			if e == nil {
-				t.Abort(KeyError{k})
-			}
-			return e
-		})
-		// genValue makes things addressable, but map values
-		// aren't addressable.
-		expr.evalAddr = nil
-		expr.evalMapValue = func(t *Thread) (Map, interface{}) {
-			// TODO(austin) Key check?  nil check?
-			return lf(t), rf(t)
-		}
-
-	default:
-		log.Panicf("unexpected left operand type %T", l.t.lit())
-	}
-
-	return expr
-}
-
-func (a *exprInfo) compileCallExpr(b *block, l *expr, as []*expr) *expr {
-	// TODO(austin) Variadic functions.
-
-	// Type check
-
-	// XXX(Spec) Calling a named function type is okay.  I really
-	// think there needs to be a general discussion of named
-	// types.  A named type creates a new, distinct type, but the
-	// type of that type is still whatever it's defined to.  Thus,
-	// in "type Foo int", Foo is still an integer type and in
-	// "type Foo func()", Foo is a function type.
-	lt, ok := l.t.lit().(*FuncType)
-	if !ok {
-		a.diag("cannot call non-function type %v", l.t)
-		return nil
-	}
-
-	// The arguments must be single-valued expressions assignment
-	// compatible with the parameters of F.
-	//
-	// XXX(Spec) The spec is wrong.  It can also be a single
-	// multi-valued expression.
-	nin := len(lt.In)
-	assign := a.compileAssign(a.pos, b, NewMultiType(lt.In), as, "function call", "argument")
-	if assign == nil {
-		return nil
-	}
-
-	var t Type
-	nout := len(lt.Out)
-	switch nout {
-	case 0:
-		t = EmptyType
-	case 1:
-		t = lt.Out[0]
-	default:
-		t = NewMultiType(lt.Out)
-	}
-	expr := a.newExpr(t, "function call")
-
-	// Gather argument and out types to initialize frame variables
-	vts := make([]Type, nin+nout)
-	copy(vts, lt.In)
-	copy(vts[nin:], lt.Out)
-
-	// Compile
-	lf := l.asFunc()
-	call := func(t *Thread) []Value {
-		fun := lf(t)
-		fr := fun.NewFrame()
-		for i, t := range vts {
-			fr.Vars[i] = t.Zero()
-		}
-		assign(multiV(fr.Vars[0:nin]), t)
-		oldf := t.f
-		t.f = fr
-		fun.Call(t)
-		t.f = oldf
-		return fr.Vars[nin : nin+nout]
-	}
-	expr.genFuncCall(call)
-
-	return expr
-}
-
-func (a *exprInfo) compileBuiltinCallExpr(b *block, ft *FuncType, as []*expr) *expr {
-	checkCount := func(min, max int) bool {
-		if len(as) < min {
-			a.diag("not enough arguments to %s", ft.builtin)
-			return false
-		} else if len(as) > max {
-			a.diag("too many arguments to %s", ft.builtin)
-			return false
-		}
-		return true
-	}
-
-	switch ft {
-	case capType:
-		if !checkCount(1, 1) {
-			return nil
-		}
-		arg := as[0].derefArray()
-		expr := a.newExpr(IntType, "function call")
-		switch t := arg.t.lit().(type) {
-		case *ArrayType:
-			// TODO(austin) It would be nice if this could
-			// be a constant int.
-			v := t.Len
-			expr.eval = func(t *Thread) int64 { return v }
-
-		case *SliceType:
-			vf := arg.asSlice()
-			expr.eval = func(t *Thread) int64 { return vf(t).Cap }
-
-		//case *ChanType:
-
-		default:
-			a.diag("illegal argument type for cap function\n\t%v", arg.t)
-			return nil
-		}
-		return expr
-
-	case copyType:
-		if !checkCount(2, 2) {
-			return nil
-		}
-		src := as[1]
-		dst := as[0]
-		if src.t != dst.t {
-			a.diag("arguments to built-in function 'copy' must have same type\nsrc: %s\ndst: %s\n", src.t, dst.t)
-			return nil
-		}
-		if _, ok := src.t.lit().(*SliceType); !ok {
-			a.diag("src argument to 'copy' must be a slice (got: %s)", src.t)
-			return nil
-		}
-		if _, ok := dst.t.lit().(*SliceType); !ok {
-			a.diag("dst argument to 'copy' must be a slice (got: %s)", dst.t)
-			return nil
-		}
-		expr := a.newExpr(IntType, "function call")
-		srcf := src.asSlice()
-		dstf := dst.asSlice()
-		expr.eval = func(t *Thread) int64 {
-			src, dst := srcf(t), dstf(t)
-			nelems := src.Len
-			if nelems > dst.Len {
-				nelems = dst.Len
-			}
-			dst.Base.Sub(0, nelems).Assign(t, src.Base.Sub(0, nelems))
-			return nelems
-		}
-		return expr
-
-	case lenType:
-		if !checkCount(1, 1) {
-			return nil
-		}
-		arg := as[0].derefArray()
-		expr := a.newExpr(IntType, "function call")
-		switch t := arg.t.lit().(type) {
-		case *stringType:
-			vf := arg.asString()
-			expr.eval = func(t *Thread) int64 { return int64(len(vf(t))) }
-
-		case *ArrayType:
-			// TODO(austin) It would be nice if this could
-			// be a constant int.
-			v := t.Len
-			expr.eval = func(t *Thread) int64 { return v }
-
-		case *SliceType:
-			vf := arg.asSlice()
-			expr.eval = func(t *Thread) int64 { return vf(t).Len }
-
-		case *MapType:
-			vf := arg.asMap()
-			expr.eval = func(t *Thread) int64 {
-				// XXX(Spec) What's the len of an
-				// uninitialized map?
-				m := vf(t)
-				if m == nil {
-					return 0
-				}
-				return m.Len(t)
-			}
-
-		//case *ChanType:
-
-		default:
-			a.diag("illegal argument type for len function\n\t%v", arg.t)
-			return nil
-		}
-		return expr
-
-	case makeType:
-		if !checkCount(1, 3) {
-			return nil
-		}
-		// XXX(Spec) What are the types of the
-		// arguments?  Do they have to be ints?  6g
-		// accepts any integral type.
-		var lenexpr, capexpr *expr
-		var lenf, capf func(*Thread) int64
-		if len(as) > 1 {
-			lenexpr = as[1].convertToInt(-1, "length", "make function")
-			if lenexpr == nil {
-				return nil
-			}
-			lenf = lenexpr.asInt()
-		}
-		if len(as) > 2 {
-			capexpr = as[2].convertToInt(-1, "capacity", "make function")
-			if capexpr == nil {
-				return nil
-			}
-			capf = capexpr.asInt()
-		}
-
-		switch t := as[0].valType.lit().(type) {
-		case *SliceType:
-			// A new, initialized slice value for a given
-			// element type T is made using the built-in
-			// function make, which takes a slice type and
-			// parameters specifying the length and
-			// optionally the capacity.
-			if !checkCount(2, 3) {
-				return nil
-			}
-			et := t.Elem
-			expr := a.newExpr(t, "function call")
-			expr.eval = func(t *Thread) Slice {
-				l := lenf(t)
-				// XXX(Spec) What if len or cap is
-				// negative?  The runtime panics.
-				if l < 0 {
-					t.Abort(NegativeLengthError{l})
-				}
-				c := l
-				if capf != nil {
-					c = capf(t)
-					if c < 0 {
-						t.Abort(NegativeCapacityError{c})
-					}
-					// XXX(Spec) What happens if
-					// len > cap?  The runtime
-					// sets cap to len.
-					if l > c {
-						c = l
-					}
-				}
-				base := arrayV(make([]Value, c))
-				for i := int64(0); i < c; i++ {
-					base[i] = et.Zero()
-				}
-				return Slice{&base, l, c}
-			}
-			return expr
-
-		case *MapType:
-			// A new, empty map value is made using the
-			// built-in function make, which takes the map
-			// type and an optional capacity hint as
-			// arguments.
-			if !checkCount(1, 2) {
-				return nil
-			}
-			expr := a.newExpr(t, "function call")
-			expr.eval = func(t *Thread) Map {
-				if lenf == nil {
-					return make(evalMap)
-				}
-				l := lenf(t)
-				return make(evalMap, l)
-			}
-			return expr
-
-		//case *ChanType:
-
-		default:
-			a.diag("illegal argument type for make function\n\t%v", as[0].valType)
-			return nil
-		}
-
-	case closeType, closedType:
-		a.diag("built-in function %s not implemented", ft.builtin)
-		return nil
-
-	case newType:
-		if !checkCount(1, 1) {
-			return nil
-		}
-
-		t := as[0].valType
-		expr := a.newExpr(NewPtrType(t), "new")
-		expr.eval = func(*Thread) Value { return t.Zero() }
-		return expr
-
-	case panicType, printType, printlnType:
-		evals := make([]func(*Thread) interface{}, len(as))
-		for i, x := range as {
-			evals[i] = x.asInterface()
-		}
-		spaces := ft == printlnType
-		newline := ft != printType
-		printer := func(t *Thread) {
-			for i, eval := range evals {
-				if i > 0 && spaces {
-					print(" ")
-				}
-				v := eval(t)
-				type stringer interface {
-					String() string
-				}
-				switch v1 := v.(type) {
-				case bool:
-					print(v1)
-				case uint64:
-					print(v1)
-				case int64:
-					print(v1)
-				case float64:
-					print(v1)
-				case string:
-					print(v1)
-				case stringer:
-					print(v1.String())
-				default:
-					print("???")
-				}
-			}
-			if newline {
-				print("\n")
-			}
-		}
-		expr := a.newExpr(EmptyType, "print")
-		expr.exec = printer
-		if ft == panicType {
-			expr.exec = func(t *Thread) {
-				printer(t)
-				t.Abort(os.NewError("panic"))
-			}
-		}
-		return expr
-	}
-
-	log.Panicf("unexpected built-in function '%s'", ft.builtin)
-	panic("unreachable")
-}
-
-func (a *exprInfo) compileStarExpr(v *expr) *expr {
-	switch vt := v.t.lit().(type) {
-	case *PtrType:
-		expr := a.newExpr(vt.Elem, "indirect expression")
-		vf := v.asPtr()
-		expr.genValue(func(t *Thread) Value {
-			v := vf(t)
-			if v == nil {
-				t.Abort(NilPointerError{})
-			}
-			return v
-		})
-		return expr
-	}
-
-	a.diagOpType(token.MUL, v.t)
-	return nil
-}
-
-var unaryOpDescs = make(map[token.Token]string)
-
-func (a *exprInfo) compileUnaryExpr(op token.Token, v *expr) *expr {
-	// Type check
-	var t Type
-	switch op {
-	case token.ADD, token.SUB:
-		if !v.t.isInteger() && !v.t.isFloat() {
-			a.diagOpType(op, v.t)
-			return nil
-		}
-		t = v.t
-
-	case token.NOT:
-		if !v.t.isBoolean() {
-			a.diagOpType(op, v.t)
-			return nil
-		}
-		t = BoolType
-
-	case token.XOR:
-		if !v.t.isInteger() {
-			a.diagOpType(op, v.t)
-			return nil
-		}
-		t = v.t
-
-	case token.AND:
-		// The unary prefix address-of operator & generates
-		// the address of its operand, which must be a
-		// variable, pointer indirection, field selector, or
-		// array or slice indexing operation.
-		if v.evalAddr == nil {
-			a.diag("cannot take the address of %s", v.desc)
-			return nil
-		}
-
-		// TODO(austin) Implement "It is illegal to take the
-		// address of a function result variable" once I have
-		// function result variables.
-
-		t = NewPtrType(v.t)
-
-	case token.ARROW:
-		log.Panicf("Unary op %v not implemented", op)
-
-	default:
-		log.Panicf("unknown unary operator %v", op)
-	}
-
-	desc, ok := unaryOpDescs[op]
-	if !ok {
-		desc = "unary " + op.String() + " expression"
-		unaryOpDescs[op] = desc
-	}
-
-	// Compile
-	expr := a.newExpr(t, desc)
-	switch op {
-	case token.ADD:
-		// Just compile it out
-		expr = v
-		expr.desc = desc
-
-	case token.SUB:
-		expr.genUnaryOpNeg(v)
-
-	case token.NOT:
-		expr.genUnaryOpNot(v)
-
-	case token.XOR:
-		expr.genUnaryOpXor(v)
-
-	case token.AND:
-		vf := v.evalAddr
-		expr.eval = func(t *Thread) Value { return vf(t) }
-
-	default:
-		log.Panicf("Compilation of unary op %v not implemented", op)
-	}
-
-	return expr
-}
-
-var binOpDescs = make(map[token.Token]string)
-
-func (a *exprInfo) compileBinaryExpr(op token.Token, l, r *expr) *expr {
-	// Save the original types of l.t and r.t for error messages.
-	origlt := l.t
-	origrt := r.t
-
-	// XXX(Spec) What is the exact definition of a "named type"?
-
-	// XXX(Spec) Arithmetic operators: "Integer types" apparently
-	// means all types compatible with basic integer types, though
-	// this is never explained.  Likewise for float types, etc.
-	// This relates to the missing explanation of named types.
-
-	// XXX(Spec) Operators: "If both operands are ideal numbers,
-	// the conversion is to ideal floats if one of the operands is
-	// an ideal float (relevant for / and %)."  How is that
-	// relevant only for / and %?  If I add an ideal int and an
-	// ideal float, I get an ideal float.
-
-	if op != token.SHL && op != token.SHR {
-		// Except in shift expressions, if one operand has
-		// numeric type and the other operand is an ideal
-		// number, the ideal number is converted to match the
-		// type of the other operand.
-		if (l.t.isInteger() || l.t.isFloat()) && !l.t.isIdeal() && r.t.isIdeal() {
-			r = r.convertTo(l.t)
-		} else if (r.t.isInteger() || r.t.isFloat()) && !r.t.isIdeal() && l.t.isIdeal() {
-			l = l.convertTo(r.t)
-		}
-		if l == nil || r == nil {
-			return nil
-		}
-
-		// Except in shift expressions, if both operands are
-		// ideal numbers and one is an ideal float, the other
-		// is converted to ideal float.
-		if l.t.isIdeal() && r.t.isIdeal() {
-			if l.t.isInteger() && r.t.isFloat() {
-				l = l.convertTo(r.t)
-			} else if l.t.isFloat() && r.t.isInteger() {
-				r = r.convertTo(l.t)
-			}
-			if l == nil || r == nil {
-				return nil
-			}
-		}
-	}
-
-	// Useful type predicates
-	// TODO(austin) CL 33668 mandates identical types except for comparisons.
-	compat := func() bool { return l.t.compat(r.t, false) }
-	integers := func() bool { return l.t.isInteger() && r.t.isInteger() }
-	floats := func() bool { return l.t.isFloat() && r.t.isFloat() }
-	strings := func() bool {
-		// TODO(austin) Deal with named types
-		return l.t == StringType && r.t == StringType
-	}
-	booleans := func() bool { return l.t.isBoolean() && r.t.isBoolean() }
-
-	// Type check
-	var t Type
-	switch op {
-	case token.ADD:
-		if !compat() || (!integers() && !floats() && !strings()) {
-			a.diagOpTypes(op, origlt, origrt)
-			return nil
-		}
-		t = l.t
-
-	case token.SUB, token.MUL, token.QUO:
-		if !compat() || (!integers() && !floats()) {
-			a.diagOpTypes(op, origlt, origrt)
-			return nil
-		}
-		t = l.t
-
-	case token.REM, token.AND, token.OR, token.XOR, token.AND_NOT:
-		if !compat() || !integers() {
-			a.diagOpTypes(op, origlt, origrt)
-			return nil
-		}
-		t = l.t
-
-	case token.SHL, token.SHR:
-		// XXX(Spec) Is it okay for the right operand to be an
-		// ideal float with no fractional part?  "The right
-		// operand in a shift operation must be always be of
-		// unsigned integer type or an ideal number that can
-		// be safely converted into an unsigned integer type
-		// (§Arithmetic operators)" suggests so and 6g agrees.
-
-		if !l.t.isInteger() || !(r.t.isInteger() || r.t.isIdeal()) {
-			a.diagOpTypes(op, origlt, origrt)
-			return nil
-		}
-
-		// The right operand in a shift operation must be
-		// always be of unsigned integer type or an ideal
-		// number that can be safely converted into an
-		// unsigned integer type.
-		if r.t.isIdeal() {
-			r2 := r.convertTo(UintType)
-			if r2 == nil {
-				return nil
-			}
-
-			// If the left operand is not ideal, convert
-			// the right to not ideal.
-			if !l.t.isIdeal() {
-				r = r2
-			}
-
-			// If both are ideal, but the right side isn't
-			// an ideal int, convert it to simplify things.
-			if l.t.isIdeal() && !r.t.isInteger() {
-				r = r.convertTo(IdealIntType)
-				if r == nil {
-					log.Panicf("conversion to uintType succeeded, but conversion to idealIntType failed")
-				}
-			}
-		} else if _, ok := r.t.lit().(*uintType); !ok {
-			a.diag("right operand of shift must be unsigned")
-			return nil
-		}
-
-		if l.t.isIdeal() && !r.t.isIdeal() {
-			// XXX(Spec) What is the meaning of "ideal >>
-			// non-ideal"?  Russ says the ideal should be
-			// converted to an int.  6g propagates the
-			// type down from assignments as a hint.
-
-			l = l.convertTo(IntType)
-			if l == nil {
-				return nil
-			}
-		}
-
-		// At this point, we should have one of three cases:
-		// 1) uint SHIFT uint
-		// 2) int SHIFT uint
-		// 3) ideal int SHIFT ideal int
-
-		t = l.t
-
-	case token.LOR, token.LAND:
-		if !booleans() {
-			return nil
-		}
-		// XXX(Spec) There's no mention of *which* boolean
-		// type the logical operators return.  From poking at
-		// 6g, it appears to be the named boolean type, NOT
-		// the type of the left operand, and NOT an unnamed
-		// boolean type.
-
-		t = BoolType
-
-	case token.ARROW:
-		// The operands in channel sends differ in type: one
-		// is always a channel and the other is a variable or
-		// value of the channel's element type.
-		log.Panic("Binary op <- not implemented")
-		t = BoolType
-
-	case token.LSS, token.GTR, token.LEQ, token.GEQ:
-		// XXX(Spec) It's really unclear what types which
-		// comparison operators apply to.  I feel like the
-		// text is trying to paint a Venn diagram for me,
-		// which it's really pretty simple: <, <=, >, >= apply
-		// only to numeric types and strings.  == and != apply
-		// to everything except arrays and structs, and there
-		// are some restrictions on when it applies to slices.
-
-		if !compat() || (!integers() && !floats() && !strings()) {
-			a.diagOpTypes(op, origlt, origrt)
-			return nil
-		}
-		t = BoolType
-
-	case token.EQL, token.NEQ:
-		// XXX(Spec) The rules for type checking comparison
-		// operators are spread across three places that all
-		// partially overlap with each other: the Comparison
-		// Compatibility section, the Operators section, and
-		// the Comparison Operators section.  The Operators
-		// section should just say that operators require
-		// identical types (as it does currently) except that
-		// there a few special cases for comparison, which are
-		// described in section X.  Currently it includes just
-		// one of the four special cases.  The Comparison
-		// Compatibility section and the Comparison Operators
-		// section should either be merged, or at least the
-		// Comparison Compatibility section should be
-		// exclusively about type checking and the Comparison
-		// Operators section should be exclusively about
-		// semantics.
-
-		// XXX(Spec) Comparison operators: "All comparison
-		// operators apply to basic types except bools."  This
-		// is very difficult to parse.  It's explained much
-		// better in the Comparison Compatibility section.
-
-		// XXX(Spec) Comparison compatibility: "Function
-		// values are equal if they refer to the same
-		// function." is rather vague.  It should probably be
-		// similar to the way the rule for map values is
-		// written: Function values are equal if they were
-		// created by the same execution of a function literal
-		// or refer to the same function declaration.  This is
-		// *almost* but not quite what 6g implements.  If a
-		// function literals does not capture any variables,
-		// then multiple executions of it will result in the
-		// same closure.  Russ says he'll change that.
-
-		// TODO(austin) Deal with remaining special cases
-
-		if !compat() {
-			a.diagOpTypes(op, origlt, origrt)
-			return nil
-		}
-		// Arrays and structs may not be compared to anything.
-		switch l.t.(type) {
-		case *ArrayType, *StructType:
-			a.diagOpTypes(op, origlt, origrt)
-			return nil
-		}
-		t = BoolType
-
-	default:
-		log.Panicf("unknown binary operator %v", op)
-	}
-
-	desc, ok := binOpDescs[op]
-	if !ok {
-		desc = op.String() + " expression"
-		binOpDescs[op] = desc
-	}
-
-	// Check for ideal divide by zero
-	switch op {
-	case token.QUO, token.REM:
-		if r.t.isIdeal() {
-			if (r.t.isInteger() && r.asIdealInt()().Sign() == 0) ||
-				(r.t.isFloat() && r.asIdealFloat()().Sign() == 0) {
-				a.diag("divide by zero")
-				return nil
-			}
-		}
-	}
-
-	// Compile
-	expr := a.newExpr(t, desc)
-	switch op {
-	case token.ADD:
-		expr.genBinOpAdd(l, r)
-
-	case token.SUB:
-		expr.genBinOpSub(l, r)
-
-	case token.MUL:
-		expr.genBinOpMul(l, r)
-
-	case token.QUO:
-		expr.genBinOpQuo(l, r)
-
-	case token.REM:
-		expr.genBinOpRem(l, r)
-
-	case token.AND:
-		expr.genBinOpAnd(l, r)
-
-	case token.OR:
-		expr.genBinOpOr(l, r)
-
-	case token.XOR:
-		expr.genBinOpXor(l, r)
-
-	case token.AND_NOT:
-		expr.genBinOpAndNot(l, r)
-
-	case token.SHL:
-		if l.t.isIdeal() {
-			lv := l.asIdealInt()()
-			rv := r.asIdealInt()()
-			const maxShift = 99999
-			if rv.Cmp(big.NewInt(maxShift)) > 0 {
-				a.diag("left shift by %v; exceeds implementation limit of %v", rv, maxShift)
-				expr.t = nil
-				return nil
-			}
-			val := new(big.Int).Lsh(lv, uint(rv.Int64()))
-			expr.eval = func() *big.Int { return val }
-		} else {
-			expr.genBinOpShl(l, r)
-		}
-
-	case token.SHR:
-		if l.t.isIdeal() {
-			lv := l.asIdealInt()()
-			rv := r.asIdealInt()()
-			val := new(big.Int).Rsh(lv, uint(rv.Int64()))
-			expr.eval = func() *big.Int { return val }
-		} else {
-			expr.genBinOpShr(l, r)
-		}
-
-	case token.LSS:
-		expr.genBinOpLss(l, r)
-
-	case token.GTR:
-		expr.genBinOpGtr(l, r)
-
-	case token.LEQ:
-		expr.genBinOpLeq(l, r)
-
-	case token.GEQ:
-		expr.genBinOpGeq(l, r)
-
-	case token.EQL:
-		expr.genBinOpEql(l, r)
-
-	case token.NEQ:
-		expr.genBinOpNeq(l, r)
-
-	case token.LAND:
-		expr.genBinOpLogAnd(l, r)
-
-	case token.LOR:
-		expr.genBinOpLogOr(l, r)
-
-	default:
-		log.Panicf("Compilation of binary op %v not implemented", op)
-	}
-
-	return expr
-}
-
-// TODO(austin) This is a hack to eliminate a circular dependency
-// between type.go and expr.go
-func (a *compiler) compileArrayLen(b *block, expr ast.Expr) (int64, bool) {
-	lenExpr := a.compileExpr(b, true, expr)
-	if lenExpr == nil {
-		return 0, false
-	}
-
-	// XXX(Spec) Are ideal floats with no fractional part okay?
-	if lenExpr.t.isIdeal() {
-		lenExpr = lenExpr.convertTo(IntType)
-		if lenExpr == nil {
-			return 0, false
-		}
-	}
-
-	if !lenExpr.t.isInteger() {
-		a.diagAt(expr.Pos(), "array size must be an integer")
-		return 0, false
-	}
-
-	switch lenExpr.t.lit().(type) {
-	case *intType:
-		return lenExpr.asInt()(nil), true
-	case *uintType:
-		return int64(lenExpr.asUint()(nil)), true
-	}
-	log.Panicf("unexpected integer type %T", lenExpr.t)
-	return 0, false
-}
-
-func (a *compiler) compileExpr(b *block, constant bool, expr ast.Expr) *expr {
-	ec := &exprCompiler{a, b, constant}
-	nerr := a.numError()
-	e := ec.compile(expr, false)
-	if e == nil && nerr == a.numError() {
-		log.Panicf("expression compilation failed without reporting errors")
-	}
-	return e
-}
-
-// extractEffect separates out any effects that the expression may
-// have, returning a function that will perform those effects and a
-// new exprCompiler that is guaranteed to be side-effect free.  These
-// are the moral equivalents of "temp := expr" and "temp" (or "temp :=
-// &expr" and "*temp" for addressable exprs).  Because this creates a
-// temporary variable, the caller should create a temporary block for
-// the compilation of this expression and the evaluation of the
-// results.
-func (a *expr) extractEffect(b *block, errOp string) (func(*Thread), *expr) {
-	// Create "&a" if a is addressable
-	rhs := a
-	if a.evalAddr != nil {
-		rhs = a.compileUnaryExpr(token.AND, rhs)
-	}
-
-	// Create temp
-	ac, ok := a.checkAssign(a.pos, []*expr{rhs}, errOp, "")
-	if !ok {
-		return nil, nil
-	}
-	if len(ac.rmt.Elems) != 1 {
-		a.diag("multi-valued expression not allowed in %s", errOp)
-		return nil, nil
-	}
-	tempType := ac.rmt.Elems[0]
-	if tempType.isIdeal() {
-		// It's too bad we have to duplicate this rule.
-		switch {
-		case tempType.isInteger():
-			tempType = IntType
-		case tempType.isFloat():
-			tempType = Float64Type
-		default:
-			log.Panicf("unexpected ideal type %v", tempType)
-		}
-	}
-	temp := b.DefineTemp(tempType)
-	tempIdx := temp.Index
-
-	// Create "temp := rhs"
-	assign := ac.compile(b, tempType)
-	if assign == nil {
-		log.Panicf("compileAssign type check failed")
-	}
-
-	effect := func(t *Thread) {
-		tempVal := tempType.Zero()
-		t.f.Vars[tempIdx] = tempVal
-		assign(tempVal, t)
-	}
-
-	// Generate "temp" or "*temp"
-	getTemp := a.compileVariable(0, temp)
-	if a.evalAddr == nil {
-		return effect, getTemp
-	}
-
-	deref := a.compileStarExpr(getTemp)
-	if deref == nil {
-		return nil, nil
-	}
-	return effect, deref
-}