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typexpr.go
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typexpr.go
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// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// This file implements type-checking of identifiers and type expressions.
package types
import (
"k8s.io/kubernetes/third_party/golang/go/ast"
"k8s.io/kubernetes/third_party/golang/go/constant"
"k8s.io/kubernetes/third_party/golang/go/token"
"sort"
"strconv"
)
// ident type-checks identifier e and initializes x with the value or type of e.
// If an error occurred, x.mode is set to invalid.
// For the meaning of def and path, see check.typ, below.
//
func (check *Checker) ident(x *operand, e *ast.Ident, def *Named, path []*TypeName) {
x.mode = invalid
x.expr = e
scope, obj := check.scope.LookupParent(e.Name, check.pos)
if obj == nil {
if e.Name == "_" {
check.errorf(e.Pos(), "cannot use _ as value or type")
} else {
check.errorf(e.Pos(), "undeclared name: %s", e.Name)
}
return
}
check.recordUse(e, obj)
check.objDecl(obj, def, path)
typ := obj.Type()
assert(typ != nil)
// The object may be dot-imported: If so, remove its package from
// the map of unused dot imports for the respective file scope.
// (This code is only needed for dot-imports. Without them,
// we only have to mark variables, see *Var case below).
if pkg := obj.Pkg(); pkg != check.pkg && pkg != nil {
delete(check.unusedDotImports[scope], pkg)
}
switch obj := obj.(type) {
case *PkgName:
check.errorf(e.Pos(), "use of package %s not in selector", obj.name)
return
case *Const:
check.addDeclDep(obj)
if typ == Typ[Invalid] {
return
}
if obj == universeIota {
if check.iota == nil {
check.errorf(e.Pos(), "cannot use iota outside constant declaration")
return
}
x.val = check.iota
} else {
x.val = obj.val
}
assert(x.val != nil)
x.mode = constant_
case *TypeName:
x.mode = typexpr
// check for cycle
// (it's ok to iterate forward because each named type appears at most once in path)
for i, prev := range path {
if prev == obj {
check.errorf(obj.pos, "illegal cycle in declaration of %s", obj.name)
// print cycle
for _, obj := range path[i:] {
check.errorf(obj.Pos(), "\t%s refers to", obj.Name()) // secondary error, \t indented
}
check.errorf(obj.Pos(), "\t%s", obj.Name())
// maintain x.mode == typexpr despite error
typ = Typ[Invalid]
break
}
}
case *Var:
if obj.pkg == check.pkg {
obj.used = true
}
check.addDeclDep(obj)
if typ == Typ[Invalid] {
return
}
x.mode = variable
case *Func:
check.addDeclDep(obj)
x.mode = value
case *Builtin:
x.id = obj.id
x.mode = builtin
case *Nil:
x.mode = value
default:
unreachable()
}
x.typ = typ
}
// typExpr type-checks the type expression e and returns its type, or Typ[Invalid].
// If def != nil, e is the type specification for the named type def, declared
// in a type declaration, and def.underlying will be set to the type of e before
// any components of e are type-checked. Path contains the path of named types
// referring to this type.
//
func (check *Checker) typExpr(e ast.Expr, def *Named, path []*TypeName) (T Type) {
if trace {
check.trace(e.Pos(), "%s", e)
check.indent++
defer func() {
check.indent--
check.trace(e.Pos(), "=> %s", T)
}()
}
T = check.typExprInternal(e, def, path)
assert(isTyped(T))
check.recordTypeAndValue(e, typexpr, T, nil)
return
}
func (check *Checker) typ(e ast.Expr) Type {
return check.typExpr(e, nil, nil)
}
// funcType type-checks a function or method type.
func (check *Checker) funcType(sig *Signature, recvPar *ast.FieldList, ftyp *ast.FuncType) {
scope := NewScope(check.scope, token.NoPos, token.NoPos, "function")
check.recordScope(ftyp, scope)
recvList, _ := check.collectParams(scope, recvPar, false)
params, variadic := check.collectParams(scope, ftyp.Params, true)
results, _ := check.collectParams(scope, ftyp.Results, false)
if recvPar != nil {
// recv parameter list present (may be empty)
// spec: "The receiver is specified via an extra parameter section preceding the
// method name. That parameter section must declare a single parameter, the receiver."
var recv *Var
switch len(recvList) {
case 0:
check.error(recvPar.Pos(), "method is missing receiver")
recv = NewParam(0, nil, "", Typ[Invalid]) // ignore recv below
default:
// more than one receiver
check.error(recvList[len(recvList)-1].Pos(), "method must have exactly one receiver")
fallthrough // continue with first receiver
case 1:
recv = recvList[0]
}
// spec: "The receiver type must be of the form T or *T where T is a type name."
// (ignore invalid types - error was reported before)
if t, _ := deref(recv.typ); t != Typ[Invalid] {
var err string
if T, _ := t.(*Named); T != nil {
// spec: "The type denoted by T is called the receiver base type; it must not
// be a pointer or interface type and it must be declared in the same package
// as the method."
if T.obj.pkg != check.pkg {
err = "type not defined in this package"
} else {
// TODO(gri) This is not correct if the underlying type is unknown yet.
switch u := T.underlying.(type) {
case *Basic:
// unsafe.Pointer is treated like a regular pointer
if u.kind == UnsafePointer {
err = "unsafe.Pointer"
}
case *Pointer, *Interface:
err = "pointer or interface type"
}
}
} else {
err = "basic or unnamed type"
}
if err != "" {
check.errorf(recv.pos, "invalid receiver %s (%s)", recv.typ, err)
// ok to continue
}
}
sig.recv = recv
}
sig.scope = scope
sig.params = NewTuple(params...)
sig.results = NewTuple(results...)
sig.variadic = variadic
}
// typExprInternal drives type checking of types.
// Must only be called by typExpr.
//
func (check *Checker) typExprInternal(e ast.Expr, def *Named, path []*TypeName) Type {
switch e := e.(type) {
case *ast.BadExpr:
// ignore - error reported before
case *ast.Ident:
var x operand
check.ident(&x, e, def, path)
switch x.mode {
case typexpr:
typ := x.typ
def.setUnderlying(typ)
return typ
case invalid:
// ignore - error reported before
case novalue:
check.errorf(x.pos(), "%s used as type", &x)
default:
check.errorf(x.pos(), "%s is not a type", &x)
}
case *ast.SelectorExpr:
var x operand
check.selector(&x, e)
switch x.mode {
case typexpr:
typ := x.typ
def.setUnderlying(typ)
return typ
case invalid:
// ignore - error reported before
case novalue:
check.errorf(x.pos(), "%s used as type", &x)
default:
check.errorf(x.pos(), "%s is not a type", &x)
}
case *ast.ParenExpr:
return check.typExpr(e.X, def, path)
case *ast.ArrayType:
if e.Len != nil {
typ := new(Array)
def.setUnderlying(typ)
typ.len = check.arrayLength(e.Len)
typ.elem = check.typExpr(e.Elt, nil, path)
return typ
} else {
typ := new(Slice)
def.setUnderlying(typ)
typ.elem = check.typ(e.Elt)
return typ
}
case *ast.StructType:
typ := new(Struct)
def.setUnderlying(typ)
check.structType(typ, e, path)
return typ
case *ast.StarExpr:
typ := new(Pointer)
def.setUnderlying(typ)
typ.base = check.typ(e.X)
return typ
case *ast.FuncType:
typ := new(Signature)
def.setUnderlying(typ)
check.funcType(typ, nil, e)
return typ
case *ast.InterfaceType:
typ := new(Interface)
def.setUnderlying(typ)
check.interfaceType(typ, e, def, path)
return typ
case *ast.MapType:
typ := new(Map)
def.setUnderlying(typ)
typ.key = check.typ(e.Key)
typ.elem = check.typ(e.Value)
// spec: "The comparison operators == and != must be fully defined
// for operands of the key type; thus the key type must not be a
// function, map, or slice."
//
// Delay this check because it requires fully setup types;
// it is safe to continue in any case (was issue 6667).
check.delay(func() {
if !Comparable(typ.key) {
check.errorf(e.Key.Pos(), "invalid map key type %s", typ.key)
}
})
return typ
case *ast.ChanType:
typ := new(Chan)
def.setUnderlying(typ)
dir := SendRecv
switch e.Dir {
case ast.SEND | ast.RECV:
// nothing to do
case ast.SEND:
dir = SendOnly
case ast.RECV:
dir = RecvOnly
default:
check.invalidAST(e.Pos(), "unknown channel direction %d", e.Dir)
// ok to continue
}
typ.dir = dir
typ.elem = check.typ(e.Value)
return typ
default:
check.errorf(e.Pos(), "%s is not a type", e)
}
typ := Typ[Invalid]
def.setUnderlying(typ)
return typ
}
// typeOrNil type-checks the type expression (or nil value) e
// and returns the typ of e, or nil.
// If e is neither a type nor nil, typOrNil returns Typ[Invalid].
//
func (check *Checker) typOrNil(e ast.Expr) Type {
var x operand
check.rawExpr(&x, e, nil)
switch x.mode {
case invalid:
// ignore - error reported before
case novalue:
check.errorf(x.pos(), "%s used as type", &x)
case typexpr:
return x.typ
case value:
if x.isNil() {
return nil
}
fallthrough
default:
check.errorf(x.pos(), "%s is not a type", &x)
}
return Typ[Invalid]
}
func (check *Checker) arrayLength(e ast.Expr) int64 {
var x operand
check.expr(&x, e)
if x.mode != constant_ {
if x.mode != invalid {
check.errorf(x.pos(), "array length %s must be constant", &x)
}
return 0
}
if !x.isInteger() {
check.errorf(x.pos(), "array length %s must be integer", &x)
return 0
}
n, ok := constant.Int64Val(x.val)
if !ok || n < 0 {
check.errorf(x.pos(), "invalid array length %s", &x)
return 0
}
return n
}
func (check *Checker) collectParams(scope *Scope, list *ast.FieldList, variadicOk bool) (params []*Var, variadic bool) {
if list == nil {
return
}
var named, anonymous bool
for i, field := range list.List {
ftype := field.Type
if t, _ := ftype.(*ast.Ellipsis); t != nil {
ftype = t.Elt
if variadicOk && i == len(list.List)-1 {
variadic = true
} else {
check.invalidAST(field.Pos(), "... not permitted")
// ignore ... and continue
}
}
typ := check.typ(ftype)
// The parser ensures that f.Tag is nil and we don't
// care if a constructed AST contains a non-nil tag.
if len(field.Names) > 0 {
// named parameter
for _, name := range field.Names {
if name.Name == "" {
check.invalidAST(name.Pos(), "anonymous parameter")
// ok to continue
}
par := NewParam(name.Pos(), check.pkg, name.Name, typ)
check.declare(scope, name, par, scope.pos)
params = append(params, par)
}
named = true
} else {
// anonymous parameter
par := NewParam(ftype.Pos(), check.pkg, "", typ)
check.recordImplicit(field, par)
params = append(params, par)
anonymous = true
}
}
if named && anonymous {
check.invalidAST(list.Pos(), "list contains both named and anonymous parameters")
// ok to continue
}
// For a variadic function, change the last parameter's type from T to []T.
if variadic && len(params) > 0 {
last := params[len(params)-1]
last.typ = &Slice{elem: last.typ}
}
return
}
func (check *Checker) declareInSet(oset *objset, pos token.Pos, obj Object) bool {
if alt := oset.insert(obj); alt != nil {
check.errorf(pos, "%s redeclared", obj.Name())
check.reportAltDecl(alt)
return false
}
return true
}
func (check *Checker) interfaceType(iface *Interface, ityp *ast.InterfaceType, def *Named, path []*TypeName) {
// empty interface: common case
if ityp.Methods == nil {
return
}
// The parser ensures that field tags are nil and we don't
// care if a constructed AST contains non-nil tags.
// use named receiver type if available (for better error messages)
var recvTyp Type = iface
if def != nil {
recvTyp = def
}
// Phase 1: Collect explicitly declared methods, the corresponding
// signature (AST) expressions, and the list of embedded
// type (AST) expressions. Do not resolve signatures or
// embedded types yet to avoid cycles referring to this
// interface.
var (
mset objset
signatures []ast.Expr // list of corresponding method signatures
embedded []ast.Expr // list of embedded types
)
for _, f := range ityp.Methods.List {
if len(f.Names) > 0 {
// The parser ensures that there's only one method
// and we don't care if a constructed AST has more.
name := f.Names[0]
pos := name.Pos()
// spec: "As with all method sets, in an interface type,
// each method must have a unique non-blank name."
if name.Name == "_" {
check.errorf(pos, "invalid method name _")
continue
}
// Don't type-check signature yet - use an
// empty signature now and update it later.
// Since we know the receiver, set it up now
// (required to avoid crash in ptrRecv; see
// e.g. test case for issue 6638).
// TODO(gri) Consider marking methods signatures
// as incomplete, for better error messages. See
// also the T4 and T5 tests in testdata/cycles2.src.
sig := new(Signature)
sig.recv = NewVar(pos, check.pkg, "", recvTyp)
m := NewFunc(pos, check.pkg, name.Name, sig)
if check.declareInSet(&mset, pos, m) {
iface.methods = append(iface.methods, m)
iface.allMethods = append(iface.allMethods, m)
signatures = append(signatures, f.Type)
check.recordDef(name, m)
}
} else {
// embedded type
embedded = append(embedded, f.Type)
}
}
// Phase 2: Resolve embedded interfaces. Because an interface must not
// embed itself (directly or indirectly), each embedded interface
// can be fully resolved without depending on any method of this
// interface (if there is a cycle or another error, the embedded
// type resolves to an invalid type and is ignored).
// In particular, the list of methods for each embedded interface
// must be complete (it cannot depend on this interface), and so
// those methods can be added to the list of all methods of this
// interface.
for _, e := range embedded {
pos := e.Pos()
typ := check.typExpr(e, nil, path)
// Determine underlying embedded (possibly incomplete) type
// by following its forward chain.
named, _ := typ.(*Named)
under := underlying(named)
embed, _ := under.(*Interface)
if embed == nil {
if typ != Typ[Invalid] {
check.errorf(pos, "%s is not an interface", typ)
}
continue
}
iface.embeddeds = append(iface.embeddeds, named)
// collect embedded methods
for _, m := range embed.allMethods {
if check.declareInSet(&mset, pos, m) {
iface.allMethods = append(iface.allMethods, m)
}
}
}
// Phase 3: At this point all methods have been collected for this interface.
// It is now safe to type-check the signatures of all explicitly
// declared methods, even if they refer to this interface via a cycle
// and embed the methods of this interface in a parameter of interface
// type.
for i, m := range iface.methods {
expr := signatures[i]
typ := check.typ(expr)
sig, _ := typ.(*Signature)
if sig == nil {
if typ != Typ[Invalid] {
check.invalidAST(expr.Pos(), "%s is not a method signature", typ)
}
continue // keep method with empty method signature
}
// update signature, but keep recv that was set up before
old := m.typ.(*Signature)
sig.recv = old.recv
*old = *sig // update signature (don't replace it!)
}
// TODO(gri) The list of explicit methods is only sorted for now to
// produce the same Interface as NewInterface. We may be able to
// claim source order in the future. Revisit.
sort.Sort(byUniqueMethodName(iface.methods))
// TODO(gri) The list of embedded types is only sorted for now to
// produce the same Interface as NewInterface. We may be able to
// claim source order in the future. Revisit.
sort.Sort(byUniqueTypeName(iface.embeddeds))
sort.Sort(byUniqueMethodName(iface.allMethods))
}
// byUniqueTypeName named type lists can be sorted by their unique type names.
type byUniqueTypeName []*Named
func (a byUniqueTypeName) Len() int { return len(a) }
func (a byUniqueTypeName) Less(i, j int) bool { return a[i].obj.Id() < a[j].obj.Id() }
func (a byUniqueTypeName) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
// byUniqueMethodName method lists can be sorted by their unique method names.
type byUniqueMethodName []*Func
func (a byUniqueMethodName) Len() int { return len(a) }
func (a byUniqueMethodName) Less(i, j int) bool { return a[i].Id() < a[j].Id() }
func (a byUniqueMethodName) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
func (check *Checker) tag(t *ast.BasicLit) string {
if t != nil {
if t.Kind == token.STRING {
if val, err := strconv.Unquote(t.Value); err == nil {
return val
}
}
check.invalidAST(t.Pos(), "incorrect tag syntax: %q", t.Value)
}
return ""
}
func (check *Checker) structType(styp *Struct, e *ast.StructType, path []*TypeName) {
list := e.Fields
if list == nil {
return
}
// struct fields and tags
var fields []*Var
var tags []string
// for double-declaration checks
var fset objset
// current field typ and tag
var typ Type
var tag string
// anonymous != nil indicates an anonymous field.
add := func(field *ast.Field, ident *ast.Ident, anonymous *TypeName, pos token.Pos) {
if tag != "" && tags == nil {
tags = make([]string, len(fields))
}
if tags != nil {
tags = append(tags, tag)
}
name := ident.Name
fld := NewField(pos, check.pkg, name, typ, anonymous != nil)
// spec: "Within a struct, non-blank field names must be unique."
if name == "_" || check.declareInSet(&fset, pos, fld) {
fields = append(fields, fld)
check.recordDef(ident, fld)
}
if anonymous != nil {
check.recordUse(ident, anonymous)
}
}
for _, f := range list.List {
typ = check.typExpr(f.Type, nil, path)
tag = check.tag(f.Tag)
if len(f.Names) > 0 {
// named fields
for _, name := range f.Names {
add(f, name, nil, name.Pos())
}
} else {
// anonymous field
name := anonymousFieldIdent(f.Type)
pos := f.Type.Pos()
t, isPtr := deref(typ)
switch t := t.(type) {
case *Basic:
if t == Typ[Invalid] {
// error was reported before
continue
}
// unsafe.Pointer is treated like a regular pointer
if t.kind == UnsafePointer {
check.errorf(pos, "anonymous field type cannot be unsafe.Pointer")
continue
}
add(f, name, Universe.Lookup(t.name).(*TypeName), pos)
case *Named:
// spec: "An embedded type must be specified as a type name
// T or as a pointer to a non-interface type name *T, and T
// itself may not be a pointer type."
switch u := t.underlying.(type) {
case *Basic:
// unsafe.Pointer is treated like a regular pointer
if u.kind == UnsafePointer {
check.errorf(pos, "anonymous field type cannot be unsafe.Pointer")
continue
}
case *Pointer:
check.errorf(pos, "anonymous field type cannot be a pointer")
continue
case *Interface:
if isPtr {
check.errorf(pos, "anonymous field type cannot be a pointer to an interface")
continue
}
}
add(f, name, t.obj, pos)
default:
check.invalidAST(pos, "anonymous field type %s must be named", typ)
}
}
}
styp.fields = fields
styp.tags = tags
}
func anonymousFieldIdent(e ast.Expr) *ast.Ident {
switch e := e.(type) {
case *ast.Ident:
return e
case *ast.StarExpr:
return anonymousFieldIdent(e.X)
case *ast.SelectorExpr:
return e.Sel
}
return nil // invalid anonymous field
}