// Comapres xv to yv using operator op
// Both xv and yv must be loaded and have a compatible type (as determined by negotiateType)
func compareOp(op token.Token, xv *Variable, yv *Variable) (bool, error) {
	switch xv.Kind {
	case reflect.Bool:
		fallthrough
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		fallthrough
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
		fallthrough
	case reflect.Float32, reflect.Float64, reflect.Complex64, reflect.Complex128:
		return constantCompare(op, xv.Value, yv.Value)
	case reflect.String:
		if int64(len(constant.StringVal(xv.Value))) != xv.Len || int64(len(constant.StringVal(yv.Value))) != yv.Len {
			return false, fmt.Errorf("string too long for comparison")
		}
		return constantCompare(op, xv.Value, yv.Value)
	}

	if op != token.EQL && op != token.NEQ {
		return false, fmt.Errorf("operator %s not defined on %s", op.String(), xv.Kind.String())
	}

	var eql bool
	var err error

	switch xv.Kind {
	case reflect.Ptr:
		eql = xv.Children[0].Addr == yv.Children[0].Addr
	case reflect.Array:
		if int64(len(xv.Children)) != xv.Len || int64(len(yv.Children)) != yv.Len {
			return false, fmt.Errorf("array too long for comparison")
		}
		eql, err = equalChildren(xv, yv, true)
	case reflect.Struct:
		if len(xv.Children) != len(yv.Children) {
			return false, nil
		}
		if int64(len(xv.Children)) != xv.Len || int64(len(yv.Children)) != yv.Len {
			return false, fmt.Errorf("sturcture too deep for comparison")
		}
		eql, err = equalChildren(xv, yv, false)
	case reflect.Slice, reflect.Map, reflect.Func, reflect.Chan:
		if xv != nilVariable && yv != nilVariable {
			return false, fmt.Errorf("can not compare %s variables", xv.Kind.String())
		}

		eql = xv.base == yv.base
	default:
		return false, fmt.Errorf("unimplemented comparison of %s variables", xv.Kind.String())
	}

	if op == token.NEQ {
		return !eql, err
	}
	return eql, err
}

// goVal returns the Go value for val, or nil.
func goVal(val constant.Value) interface{} {
	// val should exist, but be conservative and check
	if val == nil {
		return nil
	}
	// Match implementation restriction of other compilers.
	// gc only checks duplicates for integer, floating-point
	// and string values, so only create Go values for these
	// types.
	switch val.Kind() {
	case constant.Int:
		if x, ok := constant.Int64Val(val); ok {
			return x
		}
		if x, ok := constant.Uint64Val(val); ok {
			return x
		}
	case constant.Float:
		if x, ok := constant.Float64Val(val); ok {
			return x
		}
	case constant.String:
		return constant.StringVal(val)
	}
	return nil
}

func (p *exporter) value(x constant.Value) {
	if trace {
		p.tracef("value { ")
		defer p.tracef("} ")
	}

	switch kind := x.Kind(); kind {
	case constant.Bool:
		tag := falseTag
		if constant.BoolVal(x) {
			tag = trueTag
		}
		p.int(tag)
	case constant.Int:
		if i, ok := constant.Int64Val(x); ok {
			p.int(int64Tag)
			p.int64(i)
			return
		}
		p.int(floatTag)
		p.float(x)
	case constant.Float:
		p.int(fractionTag)
		p.fraction(x)
	case constant.Complex:
		p.int(complexTag)
		p.fraction(constant.Real(x))
		p.fraction(constant.Imag(x))
	case constant.String:
		p.int(stringTag)
		p.string(constant.StringVal(x))
	default:
		panic(fmt.Sprintf("unexpected value kind %d", kind))
	}
}

func (dbp *Process) getGoInformation() (ver GoVersion, isextld bool, err error) {
	vv, err := dbp.EvalPackageVariable("runtime.buildVersion")
	if err != nil {
		err = fmt.Errorf("Could not determine version number: %v\n", err)
		return
	}
	if vv.Unreadable != nil {
		err = fmt.Errorf("Unreadable version number: %v\n", vv.Unreadable)
		return
	}

	ver, ok := parseVersionString(constant.StringVal(vv.Value))
	if !ok {
		err = fmt.Errorf("Could not parse version number: %v\n", vv.Value)
		return
	}

	rdr := dbp.DwarfReader()
	rdr.Seek(0)
	for entry, err := rdr.NextCompileUnit(); entry != nil; entry, err = rdr.NextCompileUnit() {
		if err != nil {
			return ver, isextld, err
		}
		if prod, ok := entry.Val(dwarf.AttrProducer).(string); ok && (strings.HasPrefix(prod, "GNU AS")) {
			isextld = true
			break
		}
	}
	return
}

func (gvar *Variable) parseG() (*G, error) {
	mem := gvar.mem
	dbp := gvar.dbp
	gaddr := uint64(gvar.Addr)
	_, deref := gvar.RealType.(*dwarf.PtrType)

	initialInstructions := make([]byte, dbp.arch.PtrSize()+1)
	initialInstructions[0] = op.DW_OP_addr
	binary.LittleEndian.PutUint64(initialInstructions[1:], gaddr)
	if deref {
		gaddrbytes, err := mem.readMemory(uintptr(gaddr), dbp.arch.PtrSize())
		if err != nil {
			return nil, fmt.Errorf("error derefing *G %s", err)
		}
		initialInstructions = append([]byte{op.DW_OP_addr}, gaddrbytes...)
		gaddr = binary.LittleEndian.Uint64(gaddrbytes)
		if gaddr == 0 {
			id := 0
			if thread, ok := mem.(*Thread); ok {
				id = thread.ID
			}
			return nil, NoGError{tid: id}
		}
	}
	if gaddr == 0 {
		return nil, NoGError{}
	}
	gvar.loadValue()
	if gvar.Unreadable != nil {
		return nil, gvar.Unreadable
	}
	schedVar := gvar.toFieldNamed("sched")
	pc, _ := constant.Int64Val(schedVar.toFieldNamed("pc").Value)
	sp, _ := constant.Int64Val(schedVar.toFieldNamed("sp").Value)
	id, _ := constant.Int64Val(gvar.toFieldNamed("goid").Value)
	gopc, _ := constant.Int64Val(gvar.toFieldNamed("gopc").Value)
	waitReason := constant.StringVal(gvar.toFieldNamed("waitreason").Value)
	d := gvar.toFieldNamed("_defer")
	deferPC := int64(0)
	fnvar := d.toFieldNamed("fn")
	if fnvar != nil {
		fnvalvar := fnvar.toFieldNamed("fn")
		deferPC, _ = constant.Int64Val(fnvalvar.Value)
	}
	status, _ := constant.Int64Val(gvar.toFieldNamed("atomicstatus").Value)
	f, l, fn := gvar.dbp.goSymTable.PCToLine(uint64(pc))
	g := &G{
		ID:         int(id),
		GoPC:       uint64(gopc),
		PC:         uint64(pc),
		SP:         uint64(sp),
		WaitReason: waitReason,
		DeferPC:    uint64(deferPC),
		Status:     uint64(status),
		CurrentLoc: Location{PC: uint64(pc), File: f, Line: l, Fn: fn},
		dbp:        gvar.dbp,
	}
	return g, nil
}

// checkPrintf checks a call to a formatted print routine such as Printf.
// call.Args[formatIndex] is (well, should be) the format argument.
func (f *File) checkPrintf(call *ast.CallExpr, name string, formatIndex int) {
	if formatIndex >= len(call.Args) {
		f.Bad(call.Pos(), "too few arguments in call to", name)
		return
	}
	lit := f.pkg.types[call.Args[formatIndex]].Value
	if lit == nil {
		if *verbose {
			f.Warn(call.Pos(), "can't check non-constant format in call to", name)
		}
		return
	}
	if lit.Kind() != constant.String {
		f.Badf(call.Pos(), "constant %v not a string in call to %s", lit, name)
		return
	}
	format := constant.StringVal(lit)
	firstArg := formatIndex + 1 // Arguments are immediately after format string.
	if !strings.Contains(format, "%") {
		if len(call.Args) > firstArg {
			f.Badf(call.Pos(), "no formatting directive in %s call", name)
		}
		return
	}
	// Hard part: check formats against args.
	argNum := firstArg
	indexed := false
	for i, w := 0, 0; i < len(format); i += w {
		w = 1
		if format[i] == '%' {
			state := f.parsePrintfVerb(call, name, format[i:], firstArg, argNum)
			if state == nil {
				return
			}
			w = len(state.format)
			if state.indexed {
				indexed = true
			}
			if !f.okPrintfArg(call, state) { // One error per format is enough.
				return
			}
			if len(state.argNums) > 0 {
				// Continue with the next sequential argument.
				argNum = state.argNums[len(state.argNums)-1] + 1
			}
		}
	}
	// Dotdotdot is hard.
	if call.Ellipsis.IsValid() && argNum >= len(call.Args)-1 {
		return
	}
	// If the arguments were direct indexed, we assume the programmer knows what's up.
	// Otherwise, there should be no leftover arguments.
	if !indexed && argNum != len(call.Args) {
		expect := argNum - firstArg
		numArgs := len(call.Args) - firstArg
		f.Badf(call.Pos(), "wrong number of args for format in %s call: %d needed but %d args", name, expect, numArgs)
	}
}

// stringConstantArg returns call's string constant argument at the index idx.
//
// ("", false) is returned if call's argument at the index idx isn't a string
// constant.
func stringConstantArg(f *File, call *ast.CallExpr, idx int) (string, bool) {
	if idx >= len(call.Args) {
		return "", false
	}
	arg := call.Args[idx]
	lit := f.pkg.types[arg].Value
	if lit != nil && lit.Kind() == constant.String {
		return constant.StringVal(lit), true
	}
	return "", false
}

// constValue returns the value of the constant with the
// dynamic type tag appropriate for c.Type().
func constValue(c *ssa.Const) value {
	if c.IsNil() {
		return zero(c.Type()) // typed nil
	}

	if t, ok := c.Type().Underlying().(*types.Basic); ok {
		// TODO(adonovan): eliminate untyped constants from SSA form.
		switch t.Kind() {
		case types.Bool, types.UntypedBool:
			return exact.BoolVal(c.Value)
		case types.Int, types.UntypedInt:
			// Assume sizeof(int) is same on host and target.
			return int(c.Int64())
		case types.Int8:
			return int8(c.Int64())
		case types.Int16:
			return int16(c.Int64())
		case types.Int32, types.UntypedRune:
			return int32(c.Int64())
		case types.Int64:
			return c.Int64()
		case types.Uint:
			// Assume sizeof(uint) is same on host and target.
			return uint(c.Uint64())
		case types.Uint8:
			return uint8(c.Uint64())
		case types.Uint16:
			return uint16(c.Uint64())
		case types.Uint32:
			return uint32(c.Uint64())
		case types.Uint64:
			return c.Uint64()
		case types.Uintptr:
			// Assume sizeof(uintptr) is same on host and target.
			return uintptr(c.Uint64())
		case types.Float32:
			return float32(c.Float64())
		case types.Float64, types.UntypedFloat:
			return c.Float64()
		case types.Complex64:
			return complex64(c.Complex128())
		case types.Complex128, types.UntypedComplex:
			return c.Complex128()
		case types.String, types.UntypedString:
			if c.Value.Kind() == exact.String {
				return exact.StringVal(c.Value)
			}
			return string(rune(c.Int64()))
		}
	}

	panic(fmt.Sprintf("constValue: %s", c))
}

func (c *funcContext) identifierConstant(expr ast.Expr) (string, bool) {
	val := c.p.Types[expr].Value
	if val == nil {
		return "", false
	}
	s := constant.StringVal(val)
	if len(s) == 0 {
		return "", false
	}
	for i, c := range s {
		if !((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (i > 0 && c >= '0' && c <= '9') || c == '_' || c == '$') {
			return "", false
		}
	}
	return s, true
}

func (c *Const) RelString(from *types.Package) string {
	var s string
	if c.Value == nil {
		s = "nil"
	} else if c.Value.Kind() == exact.String {
		s = exact.StringVal(c.Value)
		const max = 20
		// TODO(adonovan): don't cut a rune in half.
		if len(s) > max {
			s = s[:max-3] + "..." // abbreviate
		}
		s = strconv.Quote(s)
	} else {
		s = c.Value.String()
	}
	return s + ":" + relType(c.Type(), from)
}

func newConstant(val constant.Value, mem memoryReadWriter) *Variable {
	v := &Variable{Value: val, mem: mem, loaded: true}
	switch val.Kind() {
	case constant.Int:
		v.Kind = reflect.Int
	case constant.Float:
		v.Kind = reflect.Float64
	case constant.Bool:
		v.Kind = reflect.Bool
	case constant.Complex:
		v.Kind = reflect.Complex128
	case constant.String:
		v.Kind = reflect.String
		v.Len = int64(len(constant.StringVal(val)))
	}
	return v
}

func (p *exporter) value(x constant.Value) {
	if trace {
		p.tracef("= ")
	}

	switch x.Kind() {
	case constant.Bool:
		tag := falseTag
		if constant.BoolVal(x) {
			tag = trueTag
		}
		p.tag(tag)

	case constant.Int:
		if v, exact := constant.Int64Val(x); exact {
			// common case: x fits into an int64 - use compact encoding
			p.tag(int64Tag)
			p.int64(v)
			return
		}
		// uncommon case: large x - use float encoding
		// (powers of 2 will be encoded efficiently with exponent)
		p.tag(floatTag)
		p.float(constant.ToFloat(x))

	case constant.Float:
		p.tag(floatTag)
		p.float(x)

	case constant.Complex:
		p.tag(complexTag)
		p.float(constant.Real(x))
		p.float(constant.Imag(x))

	case constant.String:
		p.tag(stringTag)
		p.string(constant.StringVal(x))

	case constant.Unknown:
		// package contains type errors
		p.tag(unknownTag)

	default:
		log.Fatalf("gcimporter: unexpected value %v (%T)", x, x)
	}
}

func ConvertVar(v *proc.Variable) *Variable {
	r := Variable{
		Addr: v.Addr,
		Name: v.Name,
		Kind: v.Kind,
		Len:  v.Len,
		Cap:  v.Cap,
	}

	if v.DwarfType != nil {
		r.Type = v.DwarfType.String()
	}

	if v.RealType != nil {
		r.RealType = v.RealType.String()
	}

	if v.Unreadable != nil {
		r.Unreadable = v.Unreadable.Error()
	}

	if v.Value != nil {
		switch v.Kind {
		case reflect.Float32:
			f, _ := constant.Float64Val(v.Value)
			r.Value = strconv.FormatFloat(f, 'f', -1, 32)
		case reflect.Float64:
			f, _ := constant.Float64Val(v.Value)
			r.Value = strconv.FormatFloat(f, 'f', -1, 64)
		case reflect.String, reflect.Func:
			r.Value = constant.StringVal(v.Value)
		default:
			r.Value = v.Value.String()
		}
	}

	r.Children = make([]Variable, len(v.Children))

	for i := range v.Children {
		r.Children[i] = *ConvertVar(&v.Children[i])
	}

	return &r
}

func (c *converter) convertConstantValue(v goconstant.Value) constant.Value {
	if v == nil {
		return nil
	}
	if v, ok := c.converted[v]; ok {
		return v.(constant.Value)
	}
	var ret constant.Value
	switch v.Kind() {
	case goconstant.Bool:
		ret = constant.MakeBool(goconstant.BoolVal(v))
	case goconstant.String:
		ret = constant.MakeString(goconstant.StringVal(v))
	case goconstant.Int:
		ret = constant.MakeFromLiteral(v.String(), token.INT, 0)
	case goconstant.Float:
		ret = constant.MakeFromLiteral(v.String(), token.FLOAT, 0)
	case goconstant.Complex:
		ret = constant.MakeFromLiteral(v.String(), token.IMAG, 0)
	}
	c.converted[v] = ret
	return ret
}

// stringVal returns the (unquoted) string value and true if
// tv is a string constant; otherwise it returns "" and false.
func stringVal(tv types.TypeAndValue) (string, bool) {
	if tv.IsValue() && tv.Value != nil && tv.Value.Kind() == constant.String {
		return constant.StringVal(tv.Value), true
	}
	return "", false
}

// ConvertVar converts from proc.Variable to api.Variable.
func ConvertVar(v *proc.Variable) *Variable {
	r := Variable{
		Addr:     v.Addr,
		OnlyAddr: v.OnlyAddr,
		Name:     v.Name,
		Kind:     v.Kind,
		Len:      v.Len,
		Cap:      v.Cap,
	}

	r.Type = prettyTypeName(v.DwarfType)
	r.RealType = prettyTypeName(v.RealType)

	if v.Unreadable != nil {
		r.Unreadable = v.Unreadable.Error()
	}

	if v.Value != nil {
		switch v.Kind {
		case reflect.Float32:
			f, _ := constant.Float64Val(v.Value)
			r.Value = strconv.FormatFloat(f, 'f', -1, 32)
		case reflect.Float64:
			f, _ := constant.Float64Val(v.Value)
			r.Value = strconv.FormatFloat(f, 'f', -1, 64)
		case reflect.String, reflect.Func:
			r.Value = constant.StringVal(v.Value)
		default:
			r.Value = v.Value.String()
		}
	}

	switch v.Kind {
	case reflect.Complex64:
		r.Children = make([]Variable, 2)
		r.Len = 2

		real, _ := constant.Float64Val(constant.Real(v.Value))
		imag, _ := constant.Float64Val(constant.Imag(v.Value))

		r.Children[0].Name = "real"
		r.Children[0].Kind = reflect.Float32
		r.Children[0].Value = strconv.FormatFloat(real, 'f', -1, 32)

		r.Children[1].Name = "imaginary"
		r.Children[1].Kind = reflect.Float32
		r.Children[1].Value = strconv.FormatFloat(imag, 'f', -1, 32)
	case reflect.Complex128:
		r.Children = make([]Variable, 2)
		r.Len = 2

		real, _ := constant.Float64Val(constant.Real(v.Value))
		imag, _ := constant.Float64Val(constant.Imag(v.Value))

		r.Children[0].Name = "real"
		r.Children[0].Kind = reflect.Float64
		r.Children[0].Value = strconv.FormatFloat(real, 'f', -1, 64)

		r.Children[1].Name = "imaginary"
		r.Children[1].Kind = reflect.Float64
		r.Children[1].Value = strconv.FormatFloat(imag, 'f', -1, 64)

	default:
		r.Children = make([]Variable, len(v.Children))

		for i := range v.Children {
			r.Children[i] = *ConvertVar(&v.Children[i])
		}
	}

	return &r
}

//.........这里部分代码省略.........
			// fallthrough
		}

		// check general case by creating custom signature
		sig := makeSig(S, S, NewSlice(T)) // []T required for variadic signature
		sig.variadic = true
		check.arguments(x, call, sig, func(x *operand, i int) {
			// only evaluate arguments that have not been evaluated before
			if i < len(alist) {
				*x = alist[i]
				return
			}
			arg(x, i)
		}, nargs)
		// ok to continue even if check.arguments reported errors

		x.mode = value
		x.typ = S
		if check.Types != nil {
			check.recordBuiltinType(call.Fun, sig)
		}

	case _Cap, _Len:
		// cap(x)
		// len(x)
		mode := invalid
		var typ Type
		var val constant.Value
		switch typ = implicitArrayDeref(x.typ.Underlying()); t := typ.(type) {
		case *Basic:
			if isString(t) && id == _Len {
				if x.mode == constant_ {
					mode = constant_
					val = constant.MakeInt64(int64(len(constant.StringVal(x.val))))
				} else {
					mode = value
				}
			}

		case *Array:
			mode = value
			// spec: "The expressions len(s) and cap(s) are constants
			// if the type of s is an array or pointer to an array and
			// the expression s does not contain channel receives or
			// function calls; in this case s is not evaluated."
			if !check.hasCallOrRecv {
				mode = constant_
				val = constant.MakeInt64(t.len)
			}

		case *Slice, *Chan:
			mode = value

		case *Map:
			if id == _Len {
				mode = value
			}
		}

		if mode == invalid {
			check.invalidArg(x.pos(), "%s for %s", x, bin.name)
			return
		}

		x.mode = mode
		x.typ = Typ[Int]

func TestVariableEvaluation(t *testing.T) {
	testcases := []struct {
		name        string
		st          reflect.Kind
		value       interface{}
		length, cap int64
		childrenlen int
	}{
		{"a1", reflect.String, "foofoofoofoofoofoo", 18, 0, 0},
		{"a11", reflect.Array, nil, 3, -1, 3},
		{"a12", reflect.Slice, nil, 2, 2, 2},
		{"a13", reflect.Slice, nil, 3, 3, 3},
		{"a2", reflect.Int, int64(6), 0, 0, 0},
		{"a3", reflect.Float64, float64(7.23), 0, 0, 0},
		{"a4", reflect.Array, nil, 2, -1, 2},
		{"a5", reflect.Slice, nil, 5, 5, 5},
		{"a6", reflect.Struct, nil, 2, 0, 2},
		{"a7", reflect.Ptr, nil, 1, 0, 1},
		{"a8", reflect.Struct, nil, 2, 0, 2},
		{"a9", reflect.Ptr, nil, 1, 0, 1},
		{"baz", reflect.String, "bazburzum", 9, 0, 0},
		{"neg", reflect.Int, int64(-1), 0, 0, 0},
		{"f32", reflect.Float32, float64(float32(1.2)), 0, 0, 0},
		{"c64", reflect.Complex64, complex128(complex64(1 + 2i)), 0, 0, 0},
		{"c128", reflect.Complex128, complex128(2 + 3i), 0, 0, 0},
		{"a6.Baz", reflect.Int, int64(8), 0, 0, 0},
		{"a7.Baz", reflect.Int, int64(5), 0, 0, 0},
		{"a8.Baz", reflect.String, "feh", 3, 0, 0},
		{"a8", reflect.Struct, nil, 2, 0, 2},
		{"i32", reflect.Array, nil, 2, -1, 2},
		{"b1", reflect.Bool, true, 0, 0, 0},
		{"b2", reflect.Bool, false, 0, 0, 0},
		{"f", reflect.Func, "main.barfoo", 0, 0, 0},
		{"ba", reflect.Slice, nil, 200, 200, 64},
	}

	withTestProcess("testvariables", t, func(p *Process, fixture protest.Fixture) {
		assertNoError(p.Continue(), t, "Continue() returned an error")

		for _, tc := range testcases {
			v, err := evalVariable(p, tc.name)
			assertNoError(err, t, fmt.Sprintf("EvalVariable(%s)", tc.name))

			if v.Kind != tc.st {
				t.Fatalf("%s simple type: expected: %s got: %s", tc.name, tc.st, v.Kind.String())
			}
			if v.Value == nil && tc.value != nil {
				t.Fatalf("%s value: expected: %v got: %v", tc.name, tc.value, v.Value)
			} else {
				switch v.Kind {
				case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
					x, _ := constant.Int64Val(v.Value)
					if y, ok := tc.value.(int64); !ok || x != y {
						t.Fatalf("%s value: expected: %v got: %v", tc.name, tc.value, v.Value)
					}
				case reflect.Float32, reflect.Float64:
					x, _ := constant.Float64Val(v.Value)
					if y, ok := tc.value.(float64); !ok || x != y {
						t.Fatalf("%s value: expected: %v got: %v", tc.name, tc.value, v.Value)
					}
				case reflect.Complex64, reflect.Complex128:
					xr, _ := constant.Float64Val(constant.Real(v.Value))
					xi, _ := constant.Float64Val(constant.Imag(v.Value))
					if y, ok := tc.value.(complex128); !ok || complex(xr, xi) != y {
						t.Fatalf("%s value: expected: %v got: %v", tc.name, tc.value, v.Value)
					}
				case reflect.String:
					if y, ok := tc.value.(string); !ok || constant.StringVal(v.Value) != y {
						t.Fatalf("%s value: expected: %v got: %v", tc.name, tc.value, v.Value)
					}
				}
			}
			if v.Len != tc.length {
				t.Fatalf("%s len: expected: %d got: %d", tc.name, tc.length, v.Len)
			}
			if v.Cap != tc.cap {
				t.Fatalf("%s cap: expected: %d got: %d", tc.name, tc.cap, v.Cap)
			}
			if len(v.Children) != tc.childrenlen {
				t.Fatalf("%s children len: expected %d got: %d", tc.name, tc.childrenlen, len(v.Children))
			}
		}
	})
}

func Test(t *testing.T) {
	switch runtime.GOOS {
	case "windows":
		t.Skipf("skipping test on %q (no /usr/bin/diff)", runtime.GOOS)
	}

	conf := loader.Config{
		Fset:       token.NewFileSet(),
		ParserMode: parser.ParseComments,
	}

	// Each entry is a single-file package.
	// (Multi-file packages aren't interesting for this test.)
	// Order matters: each non-template package is processed using
	// the preceding template package.
	for _, filename := range []string{
		"testdata/A.template",
		"testdata/A1.go",
		"testdata/A2.go",

		"testdata/B.template",
		"testdata/B1.go",

		"testdata/C.template",
		"testdata/C1.go",

		"testdata/D.template",
		"testdata/D1.go",

		"testdata/E.template",
		"testdata/E1.go",

		"testdata/F.template",
		"testdata/F1.go",

		"testdata/G.template",
		"testdata/G1.go",

		"testdata/H.template",
		"testdata/H1.go",

		"testdata/bad_type.template",
		"testdata/no_before.template",
		"testdata/no_after_return.template",
		"testdata/type_mismatch.template",
		"testdata/expr_type_mismatch.template",
	} {
		pkgname := strings.TrimSuffix(filepath.Base(filename), ".go")
		conf.CreateFromFilenames(pkgname, filename)
	}
	iprog, err := conf.Load()
	if err != nil {
		t.Fatal(err)
	}

	var xform *eg.Transformer
	for _, info := range iprog.Created {
		file := info.Files[0]
		filename := iprog.Fset.File(file.Pos()).Name() // foo.go

		if strings.HasSuffix(filename, "template") {
			// a new template
			shouldFail, _ := info.Pkg.Scope().Lookup("shouldFail").(*types.Const)
			xform, err = eg.NewTransformer(iprog.Fset, info.Pkg, file, &info.Info, *verboseFlag)
			if err != nil {
				if shouldFail == nil {
					t.Errorf("NewTransformer(%s): %s", filename, err)
				} else if want := exact.StringVal(shouldFail.Val()); !strings.Contains(err.Error(), want) {
					t.Errorf("NewTransformer(%s): got error %q, want error %q", filename, err, want)
				}
			} else if shouldFail != nil {
				t.Errorf("NewTransformer(%s) succeeded unexpectedly; want error %q",
					filename, shouldFail.Val())
			}
			continue
		}

		if xform == nil {
			t.Errorf("%s: no previous template", filename)
			continue
		}

		// apply previous template to this package
		n := xform.Transform(&info.Info, info.Pkg, file)
		if n == 0 {
			t.Errorf("%s: no matches", filename)
			continue
		}

		got := filename + "t"       // foo.got
		golden := filename + "lden" // foo.golden

		// Write actual output to foo.got.
		if err := eg.WriteAST(iprog.Fset, got, file); err != nil {
			t.Error(err)
		}
		defer os.Remove(got)

		// Compare foo.got with foo.golden.
		var cmd *exec.Cmd
//.........这里部分代码省略.........

func (c *funcContext) translateExpr(expr ast.Expr) *expression {
	exprType := c.p.TypeOf(expr)
	if value := c.p.Types[expr].Value; value != nil {
		basic := exprType.Underlying().(*types.Basic)
		switch {
		case isBoolean(basic):
			return c.formatExpr("%s", strconv.FormatBool(constant.BoolVal(value)))
		case isInteger(basic):
			if is64Bit(basic) {
				if basic.Kind() == types.Int64 {
					d, ok := constant.Int64Val(constant.ToInt(value))
					if !ok {
						panic("could not get exact uint")
					}
					return c.formatExpr("new %s(%s, %s)", c.typeName(exprType), strconv.FormatInt(d>>32, 10), strconv.FormatUint(uint64(d)&(1<<32-1), 10))
				}
				d, ok := constant.Uint64Val(constant.ToInt(value))
				if !ok {
					panic("could not get exact uint")
				}
				return c.formatExpr("new %s(%s, %s)", c.typeName(exprType), strconv.FormatUint(d>>32, 10), strconv.FormatUint(d&(1<<32-1), 10))
			}
			d, ok := constant.Int64Val(constant.ToInt(value))
			if !ok {
				panic("could not get exact int")
			}
			return c.formatExpr("%s", strconv.FormatInt(d, 10))
		case isFloat(basic):
			f, _ := constant.Float64Val(value)
			return c.formatExpr("%s", strconv.FormatFloat(f, 'g', -1, 64))
		case isComplex(basic):
			r, _ := constant.Float64Val(constant.Real(value))
			i, _ := constant.Float64Val(constant.Imag(value))
			if basic.Kind() == types.UntypedComplex {
				exprType = types.Typ[types.Complex128]
			}
			return c.formatExpr("new %s(%s, %s)", c.typeName(exprType), strconv.FormatFloat(r, 'g', -1, 64), strconv.FormatFloat(i, 'g', -1, 64))
		case isString(basic):
			return c.formatExpr("%s", encodeString(constant.StringVal(value)))
		default:
			panic("Unhandled constant type: " + basic.String())
		}
	}

	var obj types.Object
	switch e := expr.(type) {
	case *ast.SelectorExpr:
		obj = c.p.Uses[e.Sel]
	case *ast.Ident:
		obj = c.p.Defs[e]
		if obj == nil {
			obj = c.p.Uses[e]
		}
	}

	if obj != nil && typesutil.IsJsPackage(obj.Pkg()) {
		switch obj.Name() {
		case "Global":
			return c.formatExpr("$global")
		case "Module":
			return c.formatExpr("$module")
		case "Undefined":
			return c.formatExpr("undefined")
		}
	}

	switch e := expr.(type) {
	case *ast.CompositeLit:
		if ptrType, isPointer := exprType.(*types.Pointer); isPointer {
			exprType = ptrType.Elem()
		}

		collectIndexedElements := func(elementType types.Type) []string {
			var elements []string
			i := 0
			zero := c.translateExpr(c.zeroValue(elementType)).String()
			for _, element := range e.Elts {
				if kve, isKve := element.(*ast.KeyValueExpr); isKve {
					key, ok := constant.Int64Val(constant.ToInt(c.p.Types[kve.Key].Value))
					if !ok {
						panic("could not get exact int")
					}
					i = int(key)
					element = kve.Value
				}
				for len(elements) <= i {
					elements = append(elements, zero)
				}
				elements[i] = c.translateImplicitConversionWithCloning(element, elementType).String()
				i++
			}
			return elements
		}

		switch t := exprType.Underlying().(type) {
		case *types.Array:
			elements := collectIndexedElements(t.Elem())
			if len(elements) == 0 {
				return c.formatExpr("%s.zero()", c.typeName(t))
			}
//.........这里部分代码省略.........