1 // Copyright 2021 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
10 "go/internal/typeparams"
15 func (check *Checker) interfaceType(ityp *Interface, iface *ast.InterfaceType, def *Named) {
17 var tname *ast.Ident // "type" name of first entry in a type list declaration
19 for _, f := range iface.Methods.List {
20 if len(f.Names) == 0 {
21 // We have an embedded type; possibly a union of types.
22 ityp.embeddeds = append(ityp.embeddeds, parseUnion(check, flattenUnion(nil, f.Type)))
23 check.posMap[ityp] = append(check.posMap[ityp], f.Type.Pos())
27 // We have a method with name f.Names[0], or a type
28 // of a type list (name.Name == "type").
29 // (The parser ensures that there's only one method
30 // and we don't care if a constructed AST has more.)
33 check.errorf(name, _BlankIfaceMethod, "invalid method name _")
37 // TODO(rfindley) Remove type list handling once the parser doesn't accept type lists anymore.
38 if name.Name == "type" {
39 // Report an error for the first type list per interface
40 // if we don't allow type lists, but continue.
41 if !allowTypeLists && tlist == nil {
42 check.softErrorf(name, _Todo, "use generalized embedding syntax instead of a type list")
44 // For now, collect all type list entries as if it
45 // were a single union, where each union element is
47 // TODO(rfindley) remove once we disallow type lists
48 op := new(ast.UnaryExpr)
51 tlist = append(tlist, op)
52 // Report an error if we have multiple type lists in an
53 // interface, but only if they are permitted in the first place.
54 if allowTypeLists && tname != nil && tname != name {
55 check.errorf(name, _Todo, "cannot have multiple type lists in an interface")
61 typ := check.typ(f.Type)
62 sig, _ := typ.(*Signature)
64 if typ != Typ[Invalid] {
65 check.invalidAST(f.Type, "%s is not a method signature", typ)
70 // Always type-check method type parameters but complain if they are not enabled.
71 // (This extra check is needed here because interface method signatures don't have
72 // a receiver specification.)
73 if sig.tparams != nil {
74 var at positioner = f.Type
75 if tparams := typeparams.Get(f.Type); tparams != nil {
78 check.errorf(at, _Todo, "methods cannot have type parameters")
81 // use named receiver type if available (for better error messages)
82 var recvTyp Type = ityp
86 sig.recv = NewVar(name.Pos(), check.pkg, "", recvTyp)
88 m := NewFunc(name.Pos(), check.pkg, name.Name, sig)
89 check.recordDef(name, m)
90 ityp.methods = append(ityp.methods, m)
95 ityp.embeddeds = append(ityp.embeddeds, parseUnion(check, tlist))
96 // Types T in a type list are added as ~T expressions but we don't
97 // have the position of the '~'. Use the first type position instead.
98 check.posMap[ityp] = append(check.posMap[ityp], tlist[0].(*ast.UnaryExpr).X.Pos())
101 if len(ityp.methods) == 0 && len(ityp.embeddeds) == 0 {
103 ityp.allMethods = markComplete
107 // sort for API stability
108 sortMethods(ityp.methods)
109 sortTypes(ityp.embeddeds)
111 check.later(func() { check.completeInterface(iface.Pos(), ityp) })
114 func flattenUnion(list []ast.Expr, x ast.Expr) []ast.Expr {
115 if o, _ := x.(*ast.BinaryExpr); o != nil && o.Op == token.OR {
116 list = flattenUnion(list, o.X)
119 return append(list, x)
122 func (check *Checker) completeInterface(pos token.Pos, ityp *Interface) {
123 if ityp.allMethods != nil {
127 // completeInterface may be called via the LookupFieldOrMethod,
128 // MissingMethod, Identical, or IdenticalIgnoreTags external API
129 // in which case check will be nil. In this case, type-checking
130 // must be finished and all interfaces should have been completed.
132 panic("internal error: incomplete interface")
134 completeInterface(check, pos, ityp)
137 // completeInterface may be called with check == nil.
138 func completeInterface(check *Checker, pos token.Pos, ityp *Interface) {
139 assert(ityp.allMethods == nil)
141 if check != nil && trace {
142 // Types don't generally have position information.
143 // If we don't have a valid pos provided, try to use
145 if !pos.IsValid() && len(ityp.methods) > 0 {
146 pos = ityp.methods[0].pos
149 check.trace(pos, "complete %s", ityp)
153 check.trace(pos, "=> %s (methods = %v, types = %v)", ityp, ityp.allMethods, ityp.allTypes)
157 // An infinitely expanding interface (due to a cycle) is detected
158 // elsewhere (Checker.validType), so here we simply assume we only
159 // have valid interfaces. Mark the interface as complete to avoid
160 // infinite recursion if the validType check occurs later for some
162 ityp.allMethods = markComplete
164 // Methods of embedded interfaces are collected unchanged; i.e., the identity
165 // of a method I.m's Func Object of an interface I is the same as that of
166 // the method m in an interface that embeds interface I. On the other hand,
167 // if a method is embedded via multiple overlapping embedded interfaces, we
168 // don't provide a guarantee which "original m" got chosen for the embedding
169 // interface. See also issue #34421.
171 // If we don't care to provide this identity guarantee anymore, instead of
172 // reusing the original method in embeddings, we can clone the method's Func
173 // Object and give it the position of a corresponding embedded interface. Then
174 // we can get rid of the mpos map below and simply use the cloned method's
180 mpos := make(map[*Func]token.Pos) // method specification or method embedding position, for good error messages
181 addMethod := func(pos token.Pos, m *Func, explicit bool) {
182 switch other := seen.insert(m); {
184 methods = append(methods, m)
188 panic(fmt.Sprintf("%v: duplicate method %s", m.pos, m.name))
191 check.errorf(atPos(pos), _DuplicateDecl, "duplicate method %s", m.name)
192 check.errorf(atPos(mpos[other.(*Func)]), _DuplicateDecl, "\tother declaration of %s", m.name) // secondary error, \t indented
194 // We have a duplicate method name in an embedded (not explicitly declared) method.
195 // Check method signatures after all types are computed (issue #33656).
196 // If we're pre-go1.14 (overlapping embeddings are not permitted), report that
197 // error here as well (even though we could do it eagerly) because it's the same
200 // check method signatures after all locally embedded interfaces are computed
201 todo = append(todo, m, other.(*Func))
206 if !check.allowVersion(m.pkg, 1, 14) || !check.identical(m.typ, other.Type()) {
207 check.errorf(atPos(pos), _DuplicateDecl, "duplicate method %s", m.name)
208 check.errorf(atPos(mpos[other.(*Func)]), _DuplicateDecl, "\tother declaration of %s", m.name) // secondary error, \t indented
214 for _, m := range ityp.methods {
215 addMethod(m.pos, m, true)
218 // collect embedded elements
220 var posList []token.Pos
222 posList = check.posMap[ityp]
224 for i, typ := range ityp.embeddeds {
225 var pos token.Pos // embedding position
230 switch t := under(typ).(type) {
232 if t.allMethods == nil {
233 completeInterface(check, pos, t)
235 for _, m := range t.allMethods {
236 addMethod(pos, m, false) // use embedding position pos rather than m.pos
241 // TODO(gri) combine with default case once we have
242 // converted all tests to new notation and we
243 // can report an error when we don't have an
244 // interface before go1.18.
247 if check != nil && !check.allowVersion(check.pkg, 1, 18) {
248 check.errorf(atPos(pos), _InvalidIfaceEmbed, "%s is a type parameter, not an interface", typ)
253 if typ == Typ[Invalid] {
256 if check != nil && !check.allowVersion(check.pkg, 1, 18) {
257 check.errorf(atPos(pos), _InvalidIfaceEmbed, "%s is not an interface", typ)
262 allTypes = intersect(allTypes, types)
265 // process todo's (this only happens if check == nil)
266 for i := 0; i < len(todo); i += 2 {
269 if !Identical(m.typ, other.typ) {
270 panic(fmt.Sprintf("%v: duplicate method %s", m.pos, m.name))
275 sort.Sort(byUniqueMethodName(methods))
276 ityp.allMethods = methods
278 ityp.allTypes = allTypes
281 func sortTypes(list []Type) {
282 sort.Stable(byUniqueTypeName(list))
285 // byUniqueTypeName named type lists can be sorted by their unique type names.
286 type byUniqueTypeName []Type
288 func (a byUniqueTypeName) Len() int { return len(a) }
289 func (a byUniqueTypeName) Less(i, j int) bool { return sortName(a[i]) < sortName(a[j]) }
290 func (a byUniqueTypeName) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
292 func sortName(t Type) string {
293 if named := asNamed(t); named != nil {
294 return named.obj.Id()
299 func sortMethods(list []*Func) {
300 sort.Sort(byUniqueMethodName(list))
303 func assertSortedMethods(list []*Func) {
305 panic("internal error: assertSortedMethods called outside debug mode")
307 if !sort.IsSorted(byUniqueMethodName(list)) {
308 panic("internal error: methods not sorted")
312 // byUniqueMethodName method lists can be sorted by their unique method names.
313 type byUniqueMethodName []*Func
315 func (a byUniqueMethodName) Len() int { return len(a) }
316 func (a byUniqueMethodName) Less(i, j int) bool { return a[i].Id() < a[j].Id() }
317 func (a byUniqueMethodName) Swap(i, j int) { a[i], a[j] = a[j], a[i] }