Golang constant.MakeBool函数代码示例

// Evaluates identifier expressions
func (scope *EvalScope) evalIdent(node *ast.Ident) (*Variable, error) {
	switch node.Name {
	case "true", "false":
		return newConstant(constant.MakeBool(node.Name == "true"), scope.Thread), nil
	case "nil":
		return nilVariable, nil
	}

	// try to interpret this as a local variable
	v, err := scope.extractVarInfo(node.Name)
	if err != nil {
		origErr := err
		// workaround: sometimes go inserts an entry for '&varname' instead of varname
		v, err = scope.extractVarInfo("&" + node.Name)
		if err != nil {
			// if it's not a local variable then it could be a package variable w/o explicit package name
			_, _, fn := scope.Thread.dbp.PCToLine(scope.PC)
			if fn != nil {
				if v, err := scope.packageVarAddr(fn.PackageName() + "." + node.Name); err == nil {
					v.Name = node.Name
					return v, nil
				}
			}
			return nil, origErr
		}
		v = v.maybeDereference()
		v.Name = node.Name
	}
	return v, nil
}

// zeroConst returns a new "zero" constant of the specified type,
// which must not be an array or struct type: the zero values of
// aggregates are well-defined but cannot be represented by Const.
//
func zeroConst(t types.Type) *Const {
	switch t := t.(type) {
	case *types.Basic:
		switch {
		case t.Info()&types.IsBoolean != 0:
			return NewConst(exact.MakeBool(false), t)
		case t.Info()&types.IsNumeric != 0:
			return NewConst(exact.MakeInt64(0), t)
		case t.Info()&types.IsString != 0:
			return NewConst(exact.MakeString(""), t)
		case t.Kind() == types.UnsafePointer:
			fallthrough
		case t.Kind() == types.UntypedNil:
			return nilConst(t)
		default:
			panic(fmt.Sprint("zeroConst for unexpected type:", t))
		}
	case *types.Pointer, *types.Slice, *types.Interface, *types.Chan, *types.Map, *types.Signature:
		return nilConst(t)
	case *types.Named:
		return NewConst(zeroConst(t.Underlying()).Value, t)
	case *types.Array, *types.Struct, *types.Tuple:
		panic(fmt.Sprint("zeroConst applied to aggregate:", t))
	}
	panic(fmt.Sprint("zeroConst: unexpected ", t))
}

func (c *funcContext) zeroValue(ty types.Type) ast.Expr {
	switch t := ty.Underlying().(type) {
	case *types.Basic:
		switch {
		case isBoolean(t):
			return c.newConst(ty, constant.MakeBool(false))
		case isNumeric(t):
			return c.newConst(ty, constant.MakeInt64(0))
		case isString(t):
			return c.newConst(ty, constant.MakeString(""))
		case t.Kind() == types.UnsafePointer:
			// fall through to "nil"
		case t.Kind() == types.UntypedNil:
			panic("Zero value for untyped nil.")
		default:
			panic(fmt.Sprintf("Unhandled basic type: %v\n", t))
		}
	case *types.Array, *types.Struct:
		return c.setType(&ast.CompositeLit{}, ty)
	case *types.Chan, *types.Interface, *types.Map, *types.Signature, *types.Slice, *types.Pointer:
		// fall through to "nil"
	default:
		panic(fmt.Sprintf("Unhandled type: %T\n", t))
	}
	id := c.newIdent("nil", ty)
	c.p.Uses[id] = nilObj
	return id
}

func (p *importer) value() constant.Value {
	switch kind := constant.Kind(p.int()); kind {
	case falseTag:
		return constant.MakeBool(false)
	case trueTag:
		return constant.MakeBool(true)
	case int64Tag:
		return constant.MakeInt64(p.int64())
	case floatTag:
		return p.float()
	case complexTag:
		re := p.float()
		im := p.float()
		return constant.BinaryOp(re, token.ADD, constant.MakeImag(im))
	case stringTag:
		return constant.MakeString(p.string())
	default:
		panic(fmt.Sprintf("unexpected value kind %d", kind))
	}
}

func (p *importer) value() constant.Value {
	switch tag := p.tagOrIndex(); tag {
	case falseTag:
		return constant.MakeBool(false)
	case trueTag:
		return constant.MakeBool(true)
	case int64Tag:
		return constant.MakeInt64(p.int64())
	case floatTag:
		return p.float()
	case complexTag:
		re := p.float()
		im := p.float()
		return constant.BinaryOp(re, token.ADD, constant.MakeImag(im))
	case stringTag:
		return constant.MakeString(p.string())
	default:
		panic(fmt.Sprintf("unexpected value tag %d", tag))
	}
}

func (c *simplifyContext) makeTag(stmts *[]ast.Stmt, tag ast.Expr, needsTag bool) ast.Expr {
	if tag == nil {
		id := ast.NewIdent("true")
		c.info.Types[id] = types.TypeAndValue{Type: types.Typ[types.Bool], Value: constant.MakeBool(true)}
		return id
	}
	if !needsTag {
		*stmts = append(*stmts, simpleAssign(ast.NewIdent("_"), token.ASSIGN, tag))
		return nil
	}
	return c.newVar(stmts, tag)
}

func (check *Checker) comparison(x, y *operand, op token.Token) {
	// spec: "In any comparison, the first operand must be assignable
	// to the type of the second operand, or vice versa."
	err := ""
	if x.assignableTo(check.conf, y.typ, nil) || y.assignableTo(check.conf, x.typ, nil) {
		defined := false
		switch op {
		case token.EQL, token.NEQ:
			// spec: "The equality operators == and != apply to operands that are comparable."
			defined = Comparable(x.typ) || x.isNil() && hasNil(y.typ) || y.isNil() && hasNil(x.typ)
		case token.LSS, token.LEQ, token.GTR, token.GEQ:
			// spec: The ordering operators <, <=, >, and >= apply to operands that are ordered."
			defined = isOrdered(x.typ)
		default:
			unreachable()
		}
		if !defined {
			typ := x.typ
			if x.isNil() {
				typ = y.typ
			}
			err = check.sprintf("operator %s not defined for %s", op, typ)
		}
	} else {
		err = check.sprintf("mismatched types %s and %s", x.typ, y.typ)
	}

	if err != "" {
		check.errorf(x.pos(), "cannot compare %s %s %s (%s)", x.expr, op, y.expr, err)
		x.mode = invalid
		return
	}

	if x.mode == constant_ && y.mode == constant_ {
		x.val = constant.MakeBool(constant.Compare(x.val, op, y.val))
		// The operands are never materialized; no need to update
		// their types.
	} else {
		x.mode = value
		// The operands have now their final types, which at run-
		// time will be materialized. Update the expression trees.
		// If the current types are untyped, the materialized type
		// is the respective default type.
		check.updateExprType(x.expr, defaultType(x.typ), true)
		check.updateExprType(y.expr, defaultType(y.typ), true)
	}

	// spec: "Comparison operators compare two operands and yield
	//        an untyped boolean value."
	x.typ = Typ[UntypedBool]
}

// Evaluates identifier expressions
func (scope *EvalScope) evalIdent(node *ast.Ident) (*Variable, error) {
	switch node.Name {
	case "true", "false":
		return newConstant(constant.MakeBool(node.Name == "true"), scope.Thread), nil
	case "nil":
		return nilVariable, nil
	}

	// try to interpret this as a local variable
	v, err := scope.extractVarInfo(node.Name)
	if err != nil {
		// if it's not a local variable then it could be a package variable w/o explicit package name
		origErr := err
		_, _, fn := scope.Thread.dbp.PCToLine(scope.PC)
		if fn != nil {
			if v, err := scope.packageVarAddr(fn.PackageName() + "." + node.Name); err == nil {
				v.Name = node.Name
				return v, nil
			}
		}
		return nil, origErr
	}
	return v, nil
}

//.........这里部分代码省略.........
		if fun.Recv != nil {
			recvType := o.Type().(*types.Signature).Recv().Type()
			ptr, isPointer := recvType.(*types.Pointer)
			namedRecvType, _ := recvType.(*types.Named)
			if isPointer {
				namedRecvType = ptr.Elem().(*types.Named)
			}
			d.DceObjectFilter = namedRecvType.Obj().Name()
			if !fun.Name.IsExported() {
				d.DceMethodFilter = o.Name() + "~"
			}
		}

		d.DceDeps = collectDependencies(func() {
			d.DeclCode = c.translateToplevelFunction(fun, funcInfo)
		})
		funcDecls = append(funcDecls, &d)
	}
	if typesPkg.Name() == "main" {
		if mainFunc == nil {
			return nil, fmt.Errorf("missing main function")
		}
		id := c.newIdent("", types.NewSignature(nil, nil, nil, false))
		c.p.Uses[id] = mainFunc
		call := &ast.CallExpr{Fun: id}
		ifStmt := &ast.IfStmt{
			Cond: c.newIdent("$pkg === $mainPkg", types.Typ[types.Bool]),
			Body: &ast.BlockStmt{
				List: []ast.Stmt{
					&ast.ExprStmt{X: call},
					&ast.AssignStmt{
						Lhs: []ast.Expr{c.newIdent("$mainFinished", types.Typ[types.Bool])},
						Tok: token.ASSIGN,
						Rhs: []ast.Expr{c.newConst(types.Typ[types.Bool], constant.MakeBool(true))},
					},
				},
			},
		}
		if len(c.p.FuncDeclInfos[mainFunc].Blocking) != 0 {
			c.Blocking[call] = true
			c.Flattened[ifStmt] = true
		}
		funcDecls = append(funcDecls, &Decl{
			InitCode: c.CatchOutput(1, func() {
				c.translateStmt(ifStmt, nil)
			}),
		})
	}

	// named types
	var typeDecls []*Decl
	for _, o := range c.p.typeNames {
		typeName := c.objectName(o)
		d := Decl{
			Vars:            []string{typeName},
			DceObjectFilter: o.Name(),
		}
		d.DceDeps = collectDependencies(func() {
			d.DeclCode = c.CatchOutput(0, func() {
				typeName := c.objectName(o)
				lhs := typeName
				if isPkgLevel(o) {
					lhs += " = $pkg." + encodeIdent(o.Name())
				}
				size := int64(0)
				constructor := "null"

//.........这里部分代码省略.........
		check.expr(&x, s.Cond)
		if x.mode != invalid && !isBoolean(x.typ) {
			check.error(s.Cond.Pos(), "non-boolean condition in if statement")
		}
		check.stmt(inner, s.Body)
		// The parser produces a correct AST but if it was modified
		// elsewhere the else branch may be invalid. Check again.
		switch s.Else.(type) {
		case nil, *ast.BadStmt:
			// valid or error already reported
		case *ast.IfStmt, *ast.BlockStmt:
			check.stmt(inner, s.Else)
		default:
			check.error(s.Else.Pos(), "invalid else branch in if statement")
		}

	case *ast.SwitchStmt:
		inner |= breakOk
		check.openScope(s, "switch")
		defer check.closeScope()

		check.simpleStmt(s.Init)
		var x operand
		if s.Tag != nil {
			check.expr(&x, s.Tag)
			// By checking assignment of x to an invisible temporary
			// (as a compiler would), we get all the relevant checks.
			check.assignment(&x, nil, "switch expression")
		} else {
			// spec: "A missing switch expression is
			// equivalent to the boolean value true."
			x.mode = constant_
			x.typ = Typ[Bool]
			x.val = constant.MakeBool(true)
			x.expr = &ast.Ident{NamePos: s.Body.Lbrace, Name: "true"}
		}

		check.multipleDefaults(s.Body.List)

		seen := make(valueMap) // map of seen case values to positions and types
		for i, c := range s.Body.List {
			clause, _ := c.(*ast.CaseClause)
			if clause == nil {
				check.invalidAST(c.Pos(), "incorrect expression switch case")
				continue
			}
			check.caseValues(&x, clause.List, seen)
			check.openScope(clause, "case")
			inner := inner
			if i+1 < len(s.Body.List) {
				inner |= fallthroughOk
			}
			check.stmtList(inner, clause.Body)
			check.closeScope()
		}

	case *ast.TypeSwitchStmt:
		inner |= breakOk
		check.openScope(s, "type switch")
		defer check.closeScope()

		check.simpleStmt(s.Init)

		// A type switch guard must be of the form:
		//
		//     TypeSwitchGuard = [ identifier ":=" ] PrimaryExpr "." "(" "type" ")" .

// ConstValue     = string | "false" | "true" | ["-"] (int ["'"] | FloatOrComplex) .
// FloatOrComplex = float ["i" | ("+"|"-") float "i"] .
func (p *parser) parseConstValue() (val constant.Value, typ types.Type) {
	switch p.tok {
	case scanner.String:
		str := p.parseString()
		val = constant.MakeString(str)
		typ = types.Typ[types.UntypedString]
		return

	case scanner.Ident:
		b := false
		switch p.lit {
		case "false":
		case "true":
			b = true

		default:
			p.errorf("expected const value, got %s (%q)", scanner.TokenString(p.tok), p.lit)
		}

		p.next()
		val = constant.MakeBool(b)
		typ = types.Typ[types.UntypedBool]
		return
	}

	sign := ""
	if p.tok == '-' {
		p.next()
		sign = "-"
	}

	switch p.tok {
	case scanner.Int:
		val = constant.MakeFromLiteral(sign+p.lit, token.INT, 0)
		if val == nil {
			p.error("could not parse integer literal")
		}

		p.next()
		if p.tok == '\'' {
			p.next()
			typ = types.Typ[types.UntypedRune]
		} else {
			typ = types.Typ[types.UntypedInt]
		}

	case scanner.Float:
		re := sign + p.lit
		p.next()

		var im string
		switch p.tok {
		case '+':
			p.next()
			im = p.expect(scanner.Float)

		case '-':
			p.next()
			im = "-" + p.expect(scanner.Float)

		case scanner.Ident:
			// re is in fact the imaginary component. Expect "i" below.
			im = re
			re = "0"

		default:
			val = constant.MakeFromLiteral(re, token.FLOAT, 0)
			if val == nil {
				p.error("could not parse float literal")
			}
			typ = types.Typ[types.UntypedFloat]
			return
		}

		p.expectKeyword("i")
		reval := constant.MakeFromLiteral(re, token.FLOAT, 0)
		if reval == nil {
			p.error("could not parse real component of complex literal")
		}
		imval := constant.MakeFromLiteral(im+"i", token.IMAG, 0)
		if imval == nil {
			p.error("could not parse imag component of complex literal")
		}
		val = constant.BinaryOp(reval, token.ADD, imval)
		typ = types.Typ[types.UntypedComplex]

	default:
		p.errorf("expected const value, got %s (%q)", scanner.TokenString(p.tok), p.lit)
	}

	return
}

	// Error has a nil package in its qualified name since it is in no package
	res := NewVar(token.NoPos, nil, "", Typ[String])
	sig := &Signature{results: NewTuple(res)}
	err := NewFunc(token.NoPos, nil, "Error", sig)
	typ := &Named{underlying: NewInterface([]*Func{err}, nil).Complete()}
	sig.recv = NewVar(token.NoPos, nil, "", typ)
	def(NewTypeName(token.NoPos, nil, "error", typ))
}

var predeclaredConsts = [...]struct {
	name string
	kind BasicKind
	val  exact.Value
}{
	{"true", UntypedBool, exact.MakeBool(true)},
	{"false", UntypedBool, exact.MakeBool(false)},
	{"iota", UntypedInt, exact.MakeInt64(0)},
}

func defPredeclaredConsts() {
	for _, c := range predeclaredConsts {
		def(NewConst(token.NoPos, nil, c.name, Typ[c.kind], c.val))
	}
}

func defPredeclaredNil() {
	def(&Nil{object{name: "nil", typ: Typ[UntypedNil]}})
}

// A builtinId is the id of a builtin function.

func (scope *EvalScope) evalBinary(node *ast.BinaryExpr) (*Variable, error) {
	switch node.Op {
	case token.INC, token.DEC, token.ARROW:
		return nil, fmt.Errorf("operator %s not supported", node.Op.String())
	}

	xv, err := scope.evalAST(node.X)
	if err != nil {
		return nil, err
	}

	yv, err := scope.evalAST(node.Y)
	if err != nil {
		return nil, err
	}

	xv.loadValue()
	yv.loadValue()

	if xv.Unreadable != nil {
		return nil, xv.Unreadable
	}

	if yv.Unreadable != nil {
		return nil, yv.Unreadable
	}

	typ, err := negotiateType(node.Op, xv, yv)
	if err != nil {
		return nil, err
	}

	op := node.Op
	if typ != nil && (op == token.QUO) {
		_, isint := typ.(*dwarf.IntType)
		_, isuint := typ.(*dwarf.UintType)
		if isint || isuint {
			// forces integer division if the result type is integer
			op = token.QUO_ASSIGN
		}
	}

	switch op {
	case token.EQL, token.LSS, token.GTR, token.NEQ, token.LEQ, token.GEQ:
		v, err := compareOp(op, xv, yv)
		if err != nil {
			return nil, err
		}
		return newConstant(constant.MakeBool(v), xv.mem), nil

	default:
		if xv.Value == nil {
			return nil, fmt.Errorf("operator %s can not be applied to \"%s\"", node.Op.String(), exprToString(node.X))
		}

		if yv.Value == nil {
			return nil, fmt.Errorf("operator %s can not be applied to \"%s\"", node.Op.String(), exprToString(node.Y))
		}

		rc, err := constantBinaryOp(op, xv.Value, yv.Value)
		if err != nil {
			return nil, err
		}

		if typ == nil {
			return newConstant(rc, xv.mem), nil
		}

		r := xv.newVariable("", 0, typ)
		r.Value = rc
		return r, nil
	}
}

func (v *Variable) loadValueInternal(recurseLevel int) {
	if v.Unreadable != nil || v.loaded || (v.Addr == 0 && v.base == 0) {
		return
	}
	v.loaded = true
	switch v.Kind {
	case reflect.Ptr, reflect.UnsafePointer:
		v.Len = 1
		v.Children = []Variable{*v.maybeDereference()}
		// Don't increase the recursion level when dereferencing pointers
		v.Children[0].loadValueInternal(recurseLevel)

	case reflect.Chan:
		sv := v.maybeDereference()
		sv.loadValueInternal(recurseLevel)
		v.Children = sv.Children
		v.Len = sv.Len
		v.base = sv.Addr

	case reflect.Map:
		v.loadMap(recurseLevel)

	case reflect.String:
		var val string
		val, v.Unreadable = v.thread.readStringValue(v.base, v.Len)
		v.Value = constant.MakeString(val)

	case reflect.Slice, reflect.Array:
		v.loadArrayValues(recurseLevel)

	case reflect.Struct:
		t := v.RealType.(*dwarf.StructType)
		v.Len = int64(len(t.Field))
		// Recursively call extractValue to grab
		// the value of all the members of the struct.
		if recurseLevel <= maxVariableRecurse {
			v.Children = make([]Variable, 0, len(t.Field))
			for i, field := range t.Field {
				f, _ := v.toField(field)
				v.Children = append(v.Children, *f)
				v.Children[i].Name = field.Name
				v.Children[i].loadValueInternal(recurseLevel + 1)
			}
		}

	case reflect.Complex64, reflect.Complex128:
		v.readComplex(v.RealType.(*dwarf.ComplexType).ByteSize)
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		var val int64
		val, v.Unreadable = v.thread.readIntRaw(v.Addr, v.RealType.(*dwarf.IntType).ByteSize)
		v.Value = constant.MakeInt64(val)
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
		var val uint64
		val, v.Unreadable = v.thread.readUintRaw(v.Addr, v.RealType.(*dwarf.UintType).ByteSize)
		v.Value = constant.MakeUint64(val)

	case reflect.Bool:
		val, err := v.thread.readMemory(v.Addr, 1)
		v.Unreadable = err
		if err == nil {
			v.Value = constant.MakeBool(val[0] != 0)
		}
	case reflect.Float32, reflect.Float64:
		var val float64
		val, v.Unreadable = v.readFloatRaw(v.RealType.(*dwarf.FloatType).ByteSize)
		v.Value = constant.MakeFloat64(val)
	case reflect.Func:
		v.readFunctionPtr()
	default:
		v.Unreadable = fmt.Errorf("unknown or unsupported kind: \"%s\"", v.Kind.String())
	}
}

	// Error has a nil package in its qualified name since it is in no package
	res := NewVar(token.NoPos, nil, "", Typ[String])
	sig := &Signature{results: NewTuple(res)}
	err := NewFunc(token.NoPos, nil, "Error", sig)
	typ := &Named{underlying: NewInterface([]*Func{err}, nil).Complete()}
	sig.recv = NewVar(token.NoPos, nil, "", typ)
	def(NewTypeName(token.NoPos, nil, "error", typ))
}

var predeclaredConsts = [...]struct {
	name string
	kind BasicKind
	val  constant.Value
}{
	{"true", UntypedBool, constant.MakeBool(true)},
	{"false", UntypedBool, constant.MakeBool(false)},
	{"iota", UntypedInt, constant.MakeInt64(0)},
}

func defPredeclaredConsts() {
	for _, c := range predeclaredConsts {
		def(NewConst(token.NoPos, nil, c.name, Typ[c.kind], c.val))
	}
}

func defPredeclaredNil() {
	def(&Nil{object{name: "nil", typ: Typ[UntypedNil]}})
}

// A builtinId is the id of a builtin function.