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[dev.typealias] go/types: implement type aliases

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Now a TypeName is just that: a name for a type (not just Named and Basic types
as before). If it happens to be an alias, its type won't be a Named or Basic type,
or it won't have the same name. We can determine this externally.

It may be useful to provide a helper predicate to make that test easily accessible,
but we can get to that if there's an actual need.

The field/method lookup code has become more general an simpler, which is a good sign.
The changes in methodset.go are symmetric to the changes in lookup.go.

Known issue: Cycles created via alias types are not properly detected at the moment.

For #18130.

Change-Id: I90a3206be13116f89c221b5ab4d0f577eec6c78a
Reviewed-on: https://go-review.googlesource.com/35091
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>
This commit is contained in:
Robert Griesemer 2016-12-19 17:55:47 -08:00
parent a917097b5e
commit 80d8b69e95
11 changed files with 310 additions and 300 deletions
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3
src/go/types/call.go
View File

@ -275,8 +275,6 @@ func (check *Checker) selector(x *operand, e *ast.SelectorExpr) {
// so we don't need a "package" mode for operands: package names
// can only appear in qualified identifiers which are mapped to
// selector expressions.
// (see also decl.go: checker.aliasDecl)
// TODO(gri) factor this code out and share with checker.aliasDecl
if ident, ok := e.X.(*ast.Ident); ok {
_, obj := check.scope.LookupParent(ident.Name, check.pos)
if pname, _ := obj.(*PkgName); pname != nil {
@ -296,7 +294,6 @@ func (check *Checker) selector(x *operand, e *ast.SelectorExpr) {
// ok to continue
}
check.recordUse(e.Sel, exp)
exp = original(exp)
// avoid further errors if the imported object is an alias that's broken
if exp == nil {

2
src/go/types/check_test.go
View File

@ -68,11 +68,11 @@ var tests = [][]string{
{"testdata/decls1.src"},
{"testdata/decls2a.src", "testdata/decls2b.src"},
{"testdata/decls3.src"},
{"testdata/decls4.src"},
{"testdata/const0.src"},
{"testdata/const1.src"},
{"testdata/constdecl.src"},
{"testdata/vardecl.src"},
//{"testdata/aliasdecl.src"},
{"testdata/expr0.src"},
{"testdata/expr1.src"},
{"testdata/expr2.src"},

193
src/go/types/decl.go
View File

@ -81,14 +81,10 @@ func (check *Checker) objDecl(obj Object, def *Named, path []*TypeName) {
check.varDecl(obj, d.lhs, d.typ, d.init)
case *TypeName:
// invalid recursive types are detected via path
check.typeDecl(obj, d.typ, def, path)
check.typeDecl(obj, d.typ, def, path, d.alias)
case *Func:
// functions may be recursive - no need to track dependencies
check.funcDecl(obj, d)
// Alias-related code. Keep for now.
// case *Alias:
// // aliases cannot be recursive - no need to track dependencies
// check.aliasDecl(obj, d)
default:
unreachable()
}
@ -219,33 +215,42 @@ func (n *Named) setUnderlying(typ Type) {
}
}
func (check *Checker) typeDecl(obj *TypeName, typ ast.Expr, def *Named, path []*TypeName) {
func (check *Checker) typeDecl(obj *TypeName, typ ast.Expr, def *Named, path []*TypeName, alias bool) {
assert(obj.typ == nil)
// type declarations cannot use iota
assert(check.iota == nil)
named := &Named{obj: obj}
def.setUnderlying(named)
obj.typ = named // make sure recursive type declarations terminate
if alias {
// determine underlying type of named
check.typExpr(typ, named, append(path, obj))
obj.typ = Typ[Invalid]
obj.typ = check.typExpr(typ, nil, append(path, obj))
// The underlying type of named may be itself a named type that is
// incomplete:
//
// type (
// A B
// B *C
// C A
// )
//
// The type of C is the (named) type of A which is incomplete,
// and which has as its underlying type the named type B.
// Determine the (final, unnamed) underlying type by resolving
// any forward chain (they always end in an unnamed type).
named.underlying = underlying(named.underlying)
} else {
named := &Named{obj: obj}
def.setUnderlying(named)
obj.typ = named // make sure recursive type declarations terminate
// determine underlying type of named
check.typExpr(typ, named, append(path, obj))
// The underlying type of named may be itself a named type that is
// incomplete:
//
// type (
// A B
// B *C
// C A
// )
//
// The type of C is the (named) type of A which is incomplete,
// and which has as its underlying type the named type B.
// Determine the (final, unnamed) underlying type by resolving
// any forward chain (they always end in an unnamed type).
named.underlying = underlying(named.underlying)
}
// check and add associated methods
// TODO(gri) It's easy to create pathological cases where the
@ -268,21 +273,23 @@ func (check *Checker) addMethodDecls(obj *TypeName) {
// spec: "If the base type is a struct type, the non-blank method
// and field names must be distinct."
base := obj.typ.(*Named)
if t, _ := base.underlying.(*Struct); t != nil {
for _, fld := range t.fields {
if fld.name != "_" {
assert(mset.insert(fld) == nil)
base, _ := obj.typ.(*Named) // nil if receiver base type is type alias
if base != nil {
if t, _ := base.underlying.(*Struct); t != nil {
for _, fld := range t.fields {
if fld.name != "_" {
assert(mset.insert(fld) == nil)
}
}
}
}
// Checker.Files may be called multiple times; additional package files
// may add methods to already type-checked types. Add pre-existing methods
// so that we can detect redeclarations.
for _, m := range base.methods {
assert(m.name != "_")
assert(mset.insert(m) == nil)
// Checker.Files may be called multiple times; additional package files
// may add methods to already type-checked types. Add pre-existing methods
// so that we can detect redeclarations.
for _, m := range base.methods {
assert(m.name != "_")
assert(mset.insert(m) == nil)
}
}
// type-check methods
@ -295,7 +302,7 @@ func (check *Checker) addMethodDecls(obj *TypeName) {
case *Var:
check.errorf(m.pos, "field and method with the same name %s", m.name)
case *Func:
check.errorf(m.pos, "method %s already declared for %s", m.name, base)
check.errorf(m.pos, "method %s already declared for %s", m.name, obj)
default:
unreachable()
}
@ -303,9 +310,12 @@ func (check *Checker) addMethodDecls(obj *TypeName) {
continue
}
}
// type-check
check.objDecl(m, nil, nil)
// methods with blank _ names cannot be found - don't keep them
if m.name != "_" {
if base != nil && m.name != "_" {
base.methods = append(base.methods, m)
}
}
@ -333,106 +343,6 @@ func (check *Checker) funcDecl(obj *Func, decl *declInfo) {
}
}
// original returns the original Object if obj is an Alias;
// otherwise it returns obj. The result is never an Alias,
// but it may be nil.
func original(obj Object) Object {
// an alias stands for the original object; use that one instead
if alias, _ := obj.(*disabledAlias); alias != nil {
obj = alias.orig
// aliases always refer to non-alias originals
if _, ok := obj.(*disabledAlias); ok {
panic("original is an alias")
}
}
return obj
}
func (check *Checker) aliasDecl(obj *disabledAlias, decl *declInfo) {
assert(obj.typ == nil)
// alias declarations cannot use iota
assert(check.iota == nil)
// assume alias is invalid to start with
obj.typ = Typ[Invalid]
// rhs must be package-qualified identifer pkg.sel (see also call.go: checker.selector)
// TODO(gri) factor this code out and share with checker.selector
rhs := decl.init
var pkg *Package
var sel *ast.Ident
if sexpr, ok := rhs.(*ast.SelectorExpr); ok {
if ident, ok := sexpr.X.(*ast.Ident); ok {
_, obj := check.scope.LookupParent(ident.Name, check.pos)
if pname, _ := obj.(*PkgName); pname != nil {
assert(pname.pkg == check.pkg)
check.recordUse(ident, pname)
pname.used = true
pkg = pname.imported
sel = sexpr.Sel
}
}
}
if pkg == nil {
check.errorf(rhs.Pos(), "invalid alias: %v is not a package-qualified identifier", rhs)
return
}
// qualified identifier must denote an exported object
orig := pkg.scope.Lookup(sel.Name)
if orig == nil || !orig.Exported() {
if !pkg.fake {
check.errorf(rhs.Pos(), "%s is not exported by package %s", sel.Name, pkg.name)
}
return
}
check.recordUse(sel, orig)
orig = original(orig)
// avoid further errors if the imported object is an alias that's broken
if orig == nil {
return
}
// An alias declaration must not refer to package unsafe.
if orig.Pkg() == Unsafe {
check.errorf(rhs.Pos(), "invalid alias: %s refers to package unsafe (%v)", obj.Name(), orig)
return
}
// The original must be of the same kind as the alias declaration.
var why string
switch obj.kind {
case token.CONST:
if _, ok := orig.(*Const); !ok {
why = "constant"
}
case token.TYPE:
if _, ok := orig.(*TypeName); !ok {
why = "type"
}
case token.VAR:
if _, ok := orig.(*Var); !ok {
why = "variable"
}
case token.FUNC:
if _, ok := orig.(*Func); !ok {
why = "function"
}
default:
unreachable()
}
if why != "" {
check.errorf(rhs.Pos(), "invalid alias: %v is not a %s", orig, why)
return
}
// alias is valid
obj.typ = orig.Type()
obj.orig = orig
}
func (check *Checker) declStmt(decl ast.Decl) {
pkg := check.pkg
@ -534,16 +444,13 @@ func (check *Checker) declStmt(decl ast.Decl) {
}
case *ast.TypeSpec:
if s.Assign.IsValid() {
check.errorf(s.Assign, "type alias declarations not yet implemented")
}
obj := NewTypeName(s.Name.Pos(), pkg, s.Name.Name, nil)
// spec: "The scope of a type identifier declared inside a function
// begins at the identifier in the TypeSpec and ends at the end of
// the innermost containing block."
scopePos := s.Name.Pos()
check.declare(check.scope, s.Name, obj, scopePos)
check.typeDecl(obj, s.Type, nil, nil)
check.typeDecl(obj, s.Type, nil, nil, s.Assign.IsValid())
default:
check.invalidAST(s.Pos(), "const, type, or var declaration expected")

81
src/go/types/lookup.go
View File

@ -67,24 +67,22 @@ func lookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (o
}
typ, isPtr := deref(T)
named, _ := typ.(*Named)
// *typ where typ is an interface has no methods.
if isPtr {
utyp := typ
if named != nil {
utyp = named.underlying
}
if _, ok := utyp.(*Interface); ok {
return
}
if isPtr && IsInterface(typ) {
return
}
// Start with typ as single entry at shallowest depth.
// If typ is not a named type, insert a nil type instead.
current := []embeddedType{{named, nil, isPtr, false}}
current := []embeddedType{{typ, nil, isPtr, false}}
// named types that we have seen already, allocated lazily
// Named types that we have seen already, allocated lazily.
// Used to avoid endless searches in case of recursive types.
// Since only Named types can be used for recursive types, we
// only need to track those.
// (If we ever allow type aliases to construct recursive types,
// we must use type identity rather than pointer equality for
// the map key comparison, as we do in consolidateMultiples.)
var seen map[*Named]bool
// search current depth
@ -93,11 +91,12 @@ func lookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (o
// look for (pkg, name) in all types at current depth
for _, e := range current {
// The very first time only, e.typ may be nil.
// In this case, we don't have a named type and
// we simply continue with the underlying type.
if e.typ != nil {
if seen[e.typ] {
typ := e.typ
// If we have a named type, we may have associated methods.
// Look for those first.
if named, _ := typ.(*Named); named != nil {
if seen[named] {
// We have seen this type before, at a more shallow depth
// (note that multiples of this type at the current depth
// were consolidated before). The type at that depth shadows
@ -108,10 +107,10 @@ func lookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (o
if seen == nil {
seen = make(map[*Named]bool)
}
seen[e.typ] = true
seen[named] = true
// look for a matching attached method
if i, m := lookupMethod(e.typ.methods, pkg, name); m != nil {
if i, m := lookupMethod(named.methods, pkg, name); m != nil {
// potential match
assert(m.typ != nil)
index = concat(e.index, i)
@ -124,7 +123,7 @@ func lookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (o
}
// continue with underlying type
typ = e.typ.underlying
typ = named.underlying
}
switch t := typ.(type) {
@ -147,16 +146,15 @@ func lookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (o
// we have a name collision on the same depth; in either
// case we don't need to look further).
// Embedded fields are always of the form T or *T where
// T is a named type. If e.typ appeared multiple times at
// T is a type name. If e.typ appeared multiple times at
// this depth, f.typ appears multiple times at the next
// depth.
if obj == nil && f.anonymous {
// Ignore embedded basic types - only user-defined
// named types can have methods or struct fields.
typ, isPtr := deref(f.typ)
if t, _ := typ.(*Named); t != nil {
next = append(next, embeddedType{t, concat(e.index, i), e.indirect || isPtr, e.multiples})
}
// TODO(gri) optimization: ignore types that can't
// have fields or methods (only Named, Struct, and
// Interface types need to be considered).
next = append(next, embeddedType{typ, concat(e.index, i), e.indirect || isPtr, e.multiples})
}
}
@ -193,12 +191,12 @@ func lookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (o
return nil, nil, false // not found
}
// embeddedType represents an embedded named type
// embeddedType represents an embedded type
type embeddedType struct {
typ *Named // nil means use the outer typ variable instead
index []int // embedded field indices, starting with index at depth 0
indirect bool // if set, there was a pointer indirection on the path to this field
multiples bool // if set, typ appears multiple times at this depth
typ Type
index []int // embedded field indices, starting with index at depth 0
indirect bool // if set, there was a pointer indirection on the path to this field
multiples bool // if set, typ appears multiple times at this depth
}
// consolidateMultiples collects multiple list entries with the same type
@ -209,10 +207,10 @@ func consolidateMultiples(list []embeddedType) []embeddedType {
return list // at most one entry - nothing to do
}
n := 0 // number of entries w/ unique type
prev := make(map[*Named]int) // index at which type was previously seen
n := 0 // number of entries w/ unique type
prev := make(map[Type]int) // index at which type was previously seen
for _, e := range list {
if i, found := prev[e.typ]; found {
if i, found := lookupType(prev, e.typ); found {
list[i].multiples = true
// ignore this entry
} else {
@ -224,6 +222,21 @@ func consolidateMultiples(list []embeddedType) []embeddedType {
return list[:n]
}
func lookupType(m map[Type]int, typ Type) (int, bool) {
// fast path: maybe the types are equal
if i, found := m[typ]; found {
return i, true
}
for t, i := range m {
if Identical(t, typ) {
return i, true
}
}
return 0, false
}
// MissingMethod returns (nil, false) if V implements T, otherwise it
// returns a missing method required by T and whether it is missing or
// just has the wrong type.

50
src/go/types/methodset.go
View File

@ -72,24 +72,22 @@ func NewMethodSet(T Type) *MethodSet {
var base methodSet
typ, isPtr := deref(T)
named, _ := typ.(*Named)
// *typ where typ is an interface has no methods.
if isPtr {
utyp := typ
if named != nil {
utyp = named.underlying
}
if _, ok := utyp.(*Interface); ok {
return &emptyMethodSet
}
if isPtr && IsInterface(typ) {
return &emptyMethodSet
}
// Start with typ as single entry at shallowest depth.
// If typ is not a named type, insert a nil type instead.
current := []embeddedType{{named, nil, isPtr, false}}
current := []embeddedType{{typ, nil, isPtr, false}}
// named types that we have seen already, allocated lazily
// Named types that we have seen already, allocated lazily.
// Used to avoid endless searches in case of recursive types.
// Since only Named types can be used for recursive types, we
// only need to track those.
// (If we ever allow type aliases to construct recursive types,
// we must use type identity rather than pointer equality for
// the map key comparison, as we do in consolidateMultiples.)
var seen map[*Named]bool
// collect methods at current depth
@ -101,11 +99,12 @@ func NewMethodSet(T Type) *MethodSet {
var mset methodSet
for _, e := range current {
// The very first time only, e.typ may be nil.
// In this case, we don't have a named type and
// we simply continue with the underlying type.
if e.typ != nil {
if seen[e.typ] {
typ := e.typ
// If we have a named type, we may have associated methods.
// Look for those first.
if named, _ := typ.(*Named); named != nil {
if seen[named] {
// We have seen this type before, at a more shallow depth
// (note that multiples of this type at the current depth
// were consolidated before). The type at that depth shadows
@ -116,12 +115,12 @@ func NewMethodSet(T Type) *MethodSet {
if seen == nil {
seen = make(map[*Named]bool)
}
seen[e.typ] = true
seen[named] = true
mset = mset.add(e.typ.methods, e.index, e.indirect, e.multiples)
mset = mset.add(named.methods, e.index, e.indirect, e.multiples)
// continue with underlying type
typ = e.typ.underlying
typ = named.underlying
}
switch t := typ.(type) {
@ -130,16 +129,15 @@ func NewMethodSet(T Type) *MethodSet {
fset = fset.add(f, e.multiples)
// Embedded fields are always of the form T or *T where
// T is a named type. If typ appeared multiple times at
// T is a type name. If typ appeared multiple times at
// this depth, f.Type appears multiple times at the next
// depth.
if f.anonymous {
// Ignore embedded basic types - only user-defined
// named types can have methods or struct fields.
typ, isPtr := deref(f.typ)
if t, _ := typ.(*Named); t != nil {
next = append(next, embeddedType{t, concat(e.index, i), e.indirect || isPtr, e.multiples})
}
// TODO(gri) optimization: ignore types that can't
// have fields or methods (only Named, Struct, and
// Interface types need to be considered).
next = append(next, embeddedType{typ, concat(e.index, i), e.indirect || isPtr, e.multiples})
}
}

48
src/go/types/object.go
View File

@ -154,7 +154,7 @@ func NewConst(pos token.Pos, pkg *Package, name string, typ Type, val constant.V
func (obj *Const) Val() constant.Value { return obj.val }
func (*Const) isDependency() {} // a constant may be a dependency of an initialization expression
// A TypeName represents a declared type.
// A TypeName represents a name for a (named or alias) type.
type TypeName struct {
object
}
@ -215,28 +215,6 @@ func (obj *Func) FullName() string {
func (obj *Func) Scope() *Scope { return obj.typ.(*Signature).scope }
func (*Func) isDependency() {} // a function may be a dependency of an initialization expression
// An Alias represents a declared alias.
type disabledAlias struct {
object
orig Object // aliased constant, type, variable, or function; never an alias
kind token.Token // token.CONST, token.TYPE, token.VAR, or token.FUNC (only needed during resolve phase)
}
func disabledNewAlias(pos token.Pos, pkg *Package, name string, orig Object) *disabledAlias {
var typ Type = Typ[Invalid]
if orig != nil {
typ = orig.Type()
}
// No need to set a valid Alias.kind - that field is only used during identifier
// resolution (1st type-checker pass). We could store the field outside but it's
// easier to keep it here.
return &disabledAlias{object{nil, pos, pkg, name, typ, 0, token.NoPos}, orig, token.ILLEGAL}
}
// Orig returns the aliased object, or nil if there was an error.
// The returned object is never an Alias.
func (obj *disabledAlias) disabledOrig() Object { return obj.orig }
// A Label represents a declared label.
type Label struct {
object
@ -295,10 +273,6 @@ func writeObject(buf *bytes.Buffer, obj Object, qf Qualifier) {
}
return
// Alias-related code. Keep for now.
// case *Alias:
// buf.WriteString("alias")
case *Label:
buf.WriteString("label")
typ = nil
@ -322,6 +296,9 @@ func writeObject(buf *bytes.Buffer, obj Object, qf Qualifier) {
writePackage(buf, obj.Pkg(), qf)
}
buf.WriteString(obj.Name())
// TODO(gri) indicate type alias if we have one
if typ != nil {
buf.WriteByte(' ')
WriteType(buf, typ, qf)
@ -353,15 +330,14 @@ func ObjectString(obj Object, qf Qualifier) string {
return buf.String()
}
func (obj *PkgName) String() string { return ObjectString(obj, nil) }
func (obj *Const) String() string { return ObjectString(obj, nil) }
func (obj *TypeName) String() string { return ObjectString(obj, nil) }
func (obj *Var) String() string { return ObjectString(obj, nil) }
func (obj *Func) String() string { return ObjectString(obj, nil) }
func (obj *disabledAlias) String() string { return ObjectString(obj, nil) }
func (obj *Label) String() string { return ObjectString(obj, nil) }
func (obj *Builtin) String() string { return ObjectString(obj, nil) }
func (obj *Nil) String() string { return ObjectString(obj, nil) }
func (obj *PkgName) String() string { return ObjectString(obj, nil) }
func (obj *Const) String() string { return ObjectString(obj, nil) }
func (obj *TypeName) String() string { return ObjectString(obj, nil) }
func (obj *Var) String() string { return ObjectString(obj, nil) }
func (obj *Func) String() string { return ObjectString(obj, nil) }
func (obj *Label) String() string { return ObjectString(obj, nil) }
func (obj *Builtin) String() string { return ObjectString(obj, nil) }
func (obj *Nil) String() string { return ObjectString(obj, nil) }
func writeFuncName(buf *bytes.Buffer, f *Func, qf Qualifier) {
if f.typ != nil {

15
src/go/types/resolver.go
View File

@ -14,13 +14,14 @@ import (
"unicode"
)
// A declInfo describes a package-level const, type, var, func, or alias declaration.
// A declInfo describes a package-level const, type, var, or func declaration.
type declInfo struct {
file *Scope // scope of file containing this declaration
lhs []*Var // lhs of n:1 variable declarations, or nil
typ ast.Expr // type, or nil
init ast.Expr // init/orig expression, or nil
fdecl *ast.FuncDecl // func declaration, or nil
alias bool // type alias declaration
// The deps field tracks initialization expression dependencies.
// As a special (overloaded) case, it also tracks dependencies of
@ -274,13 +275,6 @@ func (check *Checker) collectObjects() {
check.declare(fileScope, nil, obj, token.NoPos)
}
// Alias-related code. Keep for now.
// case *ast.AliasSpec:
// obj := NewAlias(s.Name.Pos(), pkg, s.Name.Name, nil)
// obj.typ = nil // unresolved
// obj.kind = d.Tok
// check.declarePkgObj(s.Name, obj, &declInfo{file: fileScope, init: s.Orig})
case *ast.ValueSpec:
switch d.Tok {
case token.CONST:
@ -346,11 +340,8 @@ func (check *Checker) collectObjects() {
}
case *ast.TypeSpec:
if s.Assign.IsValid() {
check.errorf(s.Assign, "type alias declarations not yet implemented")
}
obj := NewTypeName(s.Name.Pos(), pkg, s.Name.Name, nil)
check.declarePkgObj(s.Name, obj, &declInfo{file: fileScope, typ: s.Type})
check.declarePkgObj(s.Name, obj, &declInfo{file: fileScope, typ: s.Type, alias: s.Assign.IsValid()})
default:
check.invalidAST(s.Pos(), "unknown ast.Spec node %T", s)

8
src/go/types/testdata/decls0.src vendored
View File

@ -208,11 +208,3 @@ func (BlankT) _() {}
func (BlankT) _(int) {}
func (BlankT) _() int { return 0 }
func (BlankT) _(int) int { return 0}
// type alias declarations
// TODO(gri) complete this
type (
__ = /* ERROR not yet implemented */ int
a0 = /* ERROR not yet implemented */ int
a1 = /* ERROR not yet implemented */ struct{}
)

149
src/go/types/testdata/decls4.src vendored Normal file
View File

@ -0,0 +1,149 @@
// Copyright 2016 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.
// type aliases
package decls4
type (
T0 [10]int
T1 []byte
T2 struct {
x int
}
T3 interface{
m() T2
}
T4 func(int, T0) chan T2
)
type (
Ai = int
A0 = T0
A1 = T1
A2 = T2
A3 = T3
A4 = T4
A10 = [10]int
A11 = []byte
A12 = struct {
x int
}
A13 = interface{
m() A2
}
A14 = func(int, A0) chan A2
)
// check assignment compatibility due to equality of types
var (
xi_ int
ai Ai = xi_
x0 T0
a0 A0 = x0
x1 T1
a1 A1 = x1
x2 T2
a2 A2 = x2
x3 T3
a3 A3 = x3
x4 T4
a4 A4 = x4
)
// alias receiver types
func (Ai /* ERROR "invalid receiver" */) m1() {}
func (T0) m1() {}
func (A0) m1 /* ERROR already declared */ () {}
func (A0) m2 () {}
func (A10 /* ERROR invalid receiver */ ) m1() {}
// x0 has methods m1, m2 declared via receiver type names T0 and A0
var _ interface{ m1(); m2() } = x0
// cycles
type (
C2 /* ERROR illegal cycle */ = C2
C3 /* ERROR illegal cycle */ = C4
C4 = C3
C5 struct {
f *C6
}
C6 = C5
C7 /* ERROR illegal cycle */ struct {
f C8
}
C8 = C7
)
// embedded fields
var (
s0 struct { T0 }
s1 struct { A0 } = s0 /* ERROR cannot use */ // embedded field names are different
)
// embedding and lookup of fields and methods
func _(s struct{A0}) { s.A0 = x0 }
type eX struct{xf int}
func (eX) xm()
type eY = struct{eX} // field/method set of eY includes xf, xm
type eZ = *struct{eX} // field/method set of eZ includes xf, xm
type eA struct {
eX // eX contributes xf, xm to eA
}
type eA2 struct {
*eX // *eX contributes xf, xm to eA
}
type eB struct {
eY // eY contributes xf, xm to eB
}
type eB2 struct {
*eY // *eY contributes xf, xm to eB
}
type eC struct {
eZ // eZ contributes xf, xm to eC
}
var (
_ = eA{}.xf
_ = eA{}.xm
_ = eA2{}.xf
_ = eA2{}.xm
_ = eB{}.xf
_ = eB{}.xm
_ = eB2{}.xf
_ = eB2{}.xm
_ = eC{}.xf
_ = eC{}.xm
)
// ambiguous selectors due to embedding via type aliases
type eD struct {
eY
eZ
}
var (
_ = eD /* ERROR ambiguous selector */ {}.xf
_ = eD /* ERROR ambiguous selector */ {}.xm
)
var (
_ interface{ xm() } = eD /* ERROR missing method xm */ {}
)

1
src/go/types/typestring.go
View File

@ -56,6 +56,7 @@ func RelativeTo(pkg *Package) Qualifier {
// This flag is exported in the x/tools/go/types package. We don't
// need it at the moment in the std repo and so we don't export it
// anymore. We should eventually try to remove it altogether.
// TODO(gri) remove this
var gcCompatibilityMode bool
// TypeString returns the string representation of typ.

60
src/go/types/typexpr.go
View File

@ -45,17 +45,6 @@ func (check *Checker) ident(x *operand, e *ast.Ident, def *Named, path []*TypeNa
delete(check.unusedDotImports[scope], pkg)
}
// Alias-related code. Keep for now.
// An alias stands for the original object; use that one instead.
// TODO(gri) We should be able to factor out the Typ[Invalid] test.
// if alias, _ := obj.(*Alias); alias != nil {
// obj = original(obj)
// if obj == nil || typ == Typ[Invalid] {
// return
// }
// assert(typ == obj.Type())
// }
switch obj := obj.(type) {
case *PkgName:
check.errorf(e.Pos(), "use of package %s not in selector", obj.name)
@ -661,47 +650,41 @@ func (check *Checker) structType(styp *Struct, e *ast.StructType, path []*TypeNa
}
} else {
// anonymous field
name := anonymousFieldIdent(f.Type)
// 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."
pos := f.Type.Pos()
name := anonymousFieldIdent(f.Type)
if name == nil {
check.invalidAST(pos, "anonymous field type %s has no name", f.Type)
continue
}
t, isPtr := deref(typ)
switch t := t.(type) {
// Because we have a name, typ must be of the form T or *T, where T is the name
// of a (named or alias) type, and t (= deref(typ)) must be the type of T.
switch t := t.Underlying().(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, true, 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")
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
case *Interface:
if isPtr {
check.errorf(pos, "anonymous field type cannot be a pointer to an interface")
continue
}
}
add(f, name, true, pos)
default:
check.invalidAST(pos, "anonymous field type %s must be named", typ)
}
add(f, name, true, pos)
}
}
@ -714,7 +697,10 @@ func anonymousFieldIdent(e ast.Expr) *ast.Ident {
case *ast.Ident:
return e
case *ast.StarExpr:
return anonymousFieldIdent(e.X)
// *T is valid, but **T is not
if _, ok := e.X.(*ast.StarExpr); !ok {
return anonymousFieldIdent(e.X)
}
case *ast.SelectorExpr:
return e.Sel
}