1 // Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
3 // Copyright 2013 The Go Authors. All rights reserved.
4 // Use of this source code is governed by a BSD-style
5 // license that can be found in the LICENSE file.
7 // This file implements various field and method lookup functions.
17 // Internal use of LookupFieldOrMethod: If the obj result is a method
18 // associated with a concrete (non-interface) type, the method's signature
19 // may not be fully set up. Call Checker.objDecl(obj, nil) before accessing
22 // LookupFieldOrMethod looks up a field or method with given package and name
23 // in T and returns the corresponding *Var or *Func, an index sequence, and a
24 // bool indicating if there were any pointer indirections on the path to the
25 // field or method. If addressable is set, T is the type of an addressable
26 // variable (only matters for method lookups). T must not be nil.
28 // The last index entry is the field or method index in the (possibly embedded)
29 // type where the entry was found, either:
31 // 1. the list of declared methods of a named type; or
32 // 2. the list of all methods (method set) of an interface type; or
33 // 3. the list of fields of a struct type.
35 // The earlier index entries are the indices of the embedded struct fields
36 // traversed to get to the found entry, starting at depth 0.
38 // If no entry is found, a nil object is returned. In this case, the returned
39 // index and indirect values have the following meaning:
41 // - If index != nil, the index sequence points to an ambiguous entry
42 // (the same name appeared more than once at the same embedding level).
44 // - If indirect is set, a method with a pointer receiver type was found
45 // but there was no pointer on the path from the actual receiver type to
46 // the method's formal receiver base type, nor was the receiver addressable.
47 func LookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (obj Object, index []int, indirect bool) {
49 panic("LookupFieldOrMethod on nil type")
52 // Methods cannot be associated to a named pointer type.
53 // (spec: "The type denoted by T is called the receiver base type;
54 // it must not be a pointer or interface type and it must be declared
55 // in the same package as the method.").
56 // Thus, if we have a named pointer type, proceed with the underlying
57 // pointer type but discard the result if it is a method since we would
58 // not have found it for T (see also go.dev/issue/8590).
59 if t := asNamed(T); t != nil {
60 if p, _ := t.Underlying().(*Pointer); p != nil {
61 obj, index, indirect = lookupFieldOrMethodImpl(p, false, pkg, name, false)
62 if _, ok := obj.(*Func); ok {
63 return nil, nil, false
69 obj, index, indirect = lookupFieldOrMethodImpl(T, addressable, pkg, name, false)
71 // If we didn't find anything and if we have a type parameter with a core type,
72 // see if there is a matching field (but not a method, those need to be declared
73 // explicitly in the constraint). If the constraint is a named pointer type (see
74 // above), we are ok here because only fields are accepted as results.
75 const enableTParamFieldLookup = false // see go.dev/issue/51576
76 if enableTParamFieldLookup && obj == nil && isTypeParam(T) {
77 if t := coreType(T); t != nil {
78 obj, index, indirect = lookupFieldOrMethodImpl(t, addressable, pkg, name, false)
79 if _, ok := obj.(*Var); !ok {
80 obj, index, indirect = nil, nil, false // accept fields (variables) only
87 // lookupFieldOrMethodImpl is the implementation of LookupFieldOrMethod.
88 // Notably, in contrast to LookupFieldOrMethod, it won't find struct fields
89 // in base types of defined (*Named) pointer types T. For instance, given
92 // type T *struct{f int}
94 // lookupFieldOrMethodImpl won't find the field f in the defined (*Named) type T
95 // (methods on T are not permitted in the first place).
97 // Thus, lookupFieldOrMethodImpl should only be called by LookupFieldOrMethod
98 // and missingMethod (the latter doesn't care about struct fields).
100 // If foldCase is true, method names are considered equal if they are equal
101 // with case folding.
103 // The resulting object may not be fully type-checked.
104 func lookupFieldOrMethodImpl(T Type, addressable bool, pkg *Package, name string, foldCase bool) (obj Object, index []int, indirect bool) {
105 // WARNING: The code in this function is extremely subtle - do not modify casually!
108 return // blank fields/methods are never found
111 // Importantly, we must not call under before the call to deref below (nor
112 // does deref call under), as doing so could incorrectly result in finding
113 // methods of the pointer base type when T is a (*Named) pointer type.
114 typ, isPtr := deref(T)
116 // *typ where typ is an interface (incl. a type parameter) has no methods.
118 if _, ok := under(typ).(*Interface); ok {
123 // Start with typ as single entry at shallowest depth.
124 current := []embeddedType{{typ, nil, isPtr, false}}
126 // seen tracks named types that we have seen already, allocated lazily.
127 // Used to avoid endless searches in case of recursive types.
129 // We must use a lookup on identity rather than a simple map[*Named]bool as
130 // instantiated types may be identical but not equal.
131 var seen instanceLookup
133 // search current depth
134 for len(current) > 0 {
135 var next []embeddedType // embedded types found at current depth
137 // look for (pkg, name) in all types at current depth
138 for _, e := range current {
141 // If we have a named type, we may have associated methods.
142 // Look for those first.
143 if named := asNamed(typ); named != nil {
144 if alt := seen.lookup(named); alt != nil {
145 // We have seen this type before, at a more shallow depth
146 // (note that multiples of this type at the current depth
147 // were consolidated before). The type at that depth shadows
148 // this same type at the current depth, so we can ignore
154 // look for a matching attached method
155 if i, m := named.lookupMethod(pkg, name, foldCase); m != nil {
157 // caution: method may not have a proper signature yet
158 index = concat(e.index, i)
159 if obj != nil || e.multiples {
160 return nil, index, false // collision
163 indirect = e.indirect
164 continue // we can't have a matching field or interface method
168 switch t := under(typ).(type) {
170 // look for a matching field and collect embedded types
171 for i, f := range t.fields {
172 if f.sameId(pkg, name) {
174 index = concat(e.index, i)
175 if obj != nil || e.multiples {
176 return nil, index, false // collision
179 indirect = e.indirect
180 continue // we can't have a matching interface method
182 // Collect embedded struct fields for searching the next
183 // lower depth, but only if we have not seen a match yet
184 // (if we have a match it is either the desired field or
185 // we have a name collision on the same depth; in either
186 // case we don't need to look further).
187 // Embedded fields are always of the form T or *T where
188 // T is a type name. If e.typ appeared multiple times at
189 // this depth, f.typ appears multiple times at the next
191 if obj == nil && f.embedded {
192 typ, isPtr := deref(f.typ)
193 // TODO(gri) optimization: ignore types that can't
194 // have fields or methods (only Named, Struct, and
195 // Interface types need to be considered).
196 next = append(next, embeddedType{typ, concat(e.index, i), e.indirect || isPtr, e.multiples})
201 // look for a matching method (interface may be a type parameter)
202 if i, m := t.typeSet().LookupMethod(pkg, name, foldCase); m != nil {
204 index = concat(e.index, i)
205 if obj != nil || e.multiples {
206 return nil, index, false // collision
209 indirect = e.indirect
215 // found a potential match
216 // spec: "A method call x.m() is valid if the method set of (the type of) x
217 // contains m and the argument list can be assigned to the parameter
218 // list of m. If x is addressable and &x's method set contains m, x.m()
219 // is shorthand for (&x).m()".
220 if f, _ := obj.(*Func); f != nil {
221 // determine if method has a pointer receiver
222 if f.hasPtrRecv() && !indirect && !addressable {
223 return nil, nil, true // pointer/addressable receiver required
229 current = consolidateMultiples(next)
232 return nil, nil, false // not found
235 // embeddedType represents an embedded type
236 type embeddedType struct {
238 index []int // embedded field indices, starting with index at depth 0
239 indirect bool // if set, there was a pointer indirection on the path to this field
240 multiples bool // if set, typ appears multiple times at this depth
243 // consolidateMultiples collects multiple list entries with the same type
244 // into a single entry marked as containing multiples. The result is the
245 // consolidated list.
246 func consolidateMultiples(list []embeddedType) []embeddedType {
248 return list // at most one entry - nothing to do
251 n := 0 // number of entries w/ unique type
252 prev := make(map[Type]int) // index at which type was previously seen
253 for _, e := range list {
254 if i, found := lookupType(prev, e.typ); found {
255 list[i].multiples = true
266 func lookupType(m map[Type]int, typ Type) (int, bool) {
267 // fast path: maybe the types are equal
268 if i, found := m[typ]; found {
272 for t, i := range m {
273 if Identical(t, typ) {
281 type instanceLookup struct {
282 // buf is used to avoid allocating the map m in the common case of a small
283 // number of instances.
285 m map[*Named][]*Named
288 func (l *instanceLookup) lookup(inst *Named) *Named {
289 for _, t := range l.buf {
290 if t != nil && Identical(inst, t) {
294 for _, t := range l.m[inst.Origin()] {
295 if Identical(inst, t) {
302 func (l *instanceLookup) add(inst *Named) {
303 for i, t := range l.buf {
310 l.m = make(map[*Named][]*Named)
312 insts := l.m[inst.Origin()]
313 l.m[inst.Origin()] = append(insts, inst)
316 // MissingMethod returns (nil, false) if V implements T, otherwise it
317 // returns a missing method required by T and whether it is missing or
318 // just has the wrong type: either a pointer receiver or wrong signature.
320 // For non-interface types V, or if static is set, V implements T if all
321 // methods of T are present in V. Otherwise (V is an interface and static
322 // is not set), MissingMethod only checks that methods of T which are also
323 // present in V have matching types (e.g., for a type assertion x.(T) where
324 // x is of interface type V).
325 func MissingMethod(V Type, T *Interface, static bool) (method *Func, wrongType bool) {
326 return (*Checker)(nil).missingMethod(V, T, static, Identical, nil)
329 // missingMethod is like MissingMethod but accepts a *Checker as receiver,
330 // a comparator equivalent for type comparison, and a *string for error causes.
331 // The receiver may be nil if missingMethod is invoked through an exported
332 // API call (such as MissingMethod), i.e., when all methods have been type-
334 // The underlying type of T must be an interface; T (rather than its under-
335 // lying type) is used for better error messages (reported through *cause).
336 // The comparator is used to compare signatures.
337 // If a method is missing and cause is not nil, *cause describes the error.
338 func (check *Checker) missingMethod(V, T Type, static bool, equivalent func(x, y Type) bool, cause *string) (method *Func, wrongType bool) {
339 methods := under(T).(*Interface).typeSet().methods // T must be an interface
340 if len(methods) == 0 {
355 var m *Func // method on T we're trying to implement
356 var f *Func // method on V, if found (state is one of ok, wrongName, wrongSig)
358 if u, _ := under(V).(*Interface); u != nil {
360 for _, m = range methods {
361 _, f = tset.LookupMethod(m.pkg, m.name, false)
371 if !equivalent(f.typ, m.typ) {
377 for _, m = range methods {
378 obj, index, indirect := lookupFieldOrMethodImpl(V, false, m.pkg, m.name, false)
380 // check if m is ambiguous, on *V, or on V with case-folding
389 obj, _, _ = lookupFieldOrMethodImpl(V, false, m.pkg, m.name, true /* fold case */)
398 // we must have a method (not a struct field)
405 // methods may not have a fully set up signature yet
407 check.objDecl(f, nil)
410 if !equivalent(f.typ, m.typ) {
423 // This method may be formatted in funcString below, so must have a fully
426 check.objDecl(f, nil)
432 case isInterfacePtr(V):
433 *cause = "(" + check.interfacePtrError(V) + ")"
434 case isInterfacePtr(T):
435 *cause = "(" + check.interfacePtrError(T) + ")"
437 *cause = check.sprintf("(missing method %s)", m.Name())
440 fs, ms := check.funcString(f, false), check.funcString(m, false)
441 *cause = check.sprintf("(missing method %s)\n\t\thave %s\n\t\twant %s",
444 fs, ms := check.funcString(f, false), check.funcString(m, false)
446 // Don't report "want Foo, have Foo".
447 // Add package information to disambiguate (go.dev/issue/54258).
448 fs, ms = check.funcString(f, true), check.funcString(m, true)
450 *cause = check.sprintf("(wrong type for method %s)\n\t\thave %s\n\t\twant %s",
453 *cause = check.sprintf("(ambiguous selector %s.%s)", V, m.Name())
455 *cause = check.sprintf("(method %s has pointer receiver)", m.Name())
457 *cause = check.sprintf("(%s.%s is a field, not a method)", V, m.Name())
463 return m, state == wrongSig || state == ptrRecv
466 func isInterfacePtr(T Type) bool {
467 p, _ := under(T).(*Pointer)
468 return p != nil && IsInterface(p.base)
472 func (check *Checker) interfacePtrError(T Type) string {
473 assert(isInterfacePtr(T))
474 if p, _ := under(T).(*Pointer); isTypeParam(p.base) {
475 return check.sprintf("type %s is pointer to type parameter, not type parameter", T)
477 return check.sprintf("type %s is pointer to interface, not interface", T)
480 // funcString returns a string of the form name + signature for f.
482 func (check *Checker) funcString(f *Func, pkgInfo bool) string {
483 buf := bytes.NewBufferString(f.name)
485 if check != nil && !pkgInfo {
488 w := newTypeWriter(buf, qf)
491 w.signature(f.typ.(*Signature))
495 // assertableTo reports whether a value of type V can be asserted to have type T.
496 // The receiver may be nil if assertableTo is invoked through an exported API call
497 // (such as AssertableTo), i.e., when all methods have been type-checked.
498 // The underlying type of V must be an interface.
499 // If the result is false and cause is not nil, *cause describes the error.
500 // TODO(gri) replace calls to this function with calls to newAssertableTo.
501 func (check *Checker) assertableTo(V, T Type, cause *string) bool {
502 // no static check is required if T is an interface
503 // spec: "If T is an interface type, x.(T) asserts that the
504 // dynamic type of x implements the interface T."
508 // TODO(gri) fix this for generalized interfaces
509 m, _ := check.missingMethod(T, V, false, Identical, cause)
513 // newAssertableTo reports whether a value of type V can be asserted to have type T.
514 // It also implements behavior for interfaces that currently are only permitted
515 // in constraint position (we have not yet defined that behavior in the spec).
516 // The underlying type of V must be an interface.
517 // If the result is false and cause is not nil, *cause is set to the error cause.
518 func (check *Checker) newAssertableTo(pos token.Pos, V, T Type, cause *string) bool {
519 // no static check is required if T is an interface
520 // spec: "If T is an interface type, x.(T) asserts that the
521 // dynamic type of x implements the interface T."
525 return check.implements(pos, T, V, false, cause)
528 // deref dereferences typ if it is a *Pointer (but not a *Named type
529 // with an underlying pointer type!) and returns its base and true.
530 // Otherwise it returns (typ, false).
531 func deref(typ Type) (Type, bool) {
532 if p, _ := _Unalias(typ).(*Pointer); p != nil {
533 // p.base should never be nil, but be conservative
536 panic("pointer with nil base type (possibly due to an invalid cyclic declaration)")
538 return Typ[Invalid], true
545 // derefStructPtr dereferences typ if it is a (named or unnamed) pointer to a
546 // (named or unnamed) struct and returns its base. Otherwise it returns typ.
547 func derefStructPtr(typ Type) Type {
548 if p, _ := under(typ).(*Pointer); p != nil {
549 if _, ok := under(p.base).(*Struct); ok {
556 // concat returns the result of concatenating list and i.
557 // The result does not share its underlying array with list.
558 func concat(list []int, i int) []int {
560 t = append(t, list...)
564 // fieldIndex returns the index for the field with matching package and name, or a value < 0.
565 func fieldIndex(fields []*Var, pkg *Package, name string) int {
567 for i, f := range fields {
568 if f.sameId(pkg, name) {
576 // lookupMethod returns the index of and method with matching package and name, or (-1, nil).
577 // If foldCase is true, method names are considered equal if they are equal with case folding.
578 func lookupMethod(methods []*Func, pkg *Package, name string, foldCase bool) (int, *Func) {
580 for i, m := range methods {
581 if (m.name == name || foldCase && strings.EqualFold(m.name, name)) && m.sameId(pkg, m.name) {