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.
16 // Internal use of LookupFieldOrMethod: If the obj result is a method
17 // associated with a concrete (non-interface) type, the method's signature
18 // may not be fully set up. Call Checker.objDecl(obj, nil) before accessing
21 // LookupFieldOrMethod looks up a field or method with given package and name
22 // in T and returns the corresponding *Var or *Func, an index sequence, and a
23 // bool indicating if there were any pointer indirections on the path to the
24 // field or method. If addressable is set, T is the type of an addressable
25 // variable (only matters for method lookups). T must not be nil.
27 // The last index entry is the field or method index in the (possibly embedded)
28 // type where the entry was found, either:
30 // 1. the list of declared methods of a named type; or
31 // 2. the list of all methods (method set) of an interface type; or
32 // 3. the list of fields of a struct type.
34 // The earlier index entries are the indices of the embedded struct fields
35 // traversed to get to the found entry, starting at depth 0.
37 // If no entry is found, a nil object is returned. In this case, the returned
38 // index and indirect values have the following meaning:
40 // - If index != nil, the index sequence points to an ambiguous entry
41 // (the same name appeared more than once at the same embedding level).
43 // - If indirect is set, a method with a pointer receiver type was found
44 // but there was no pointer on the path from the actual receiver type to
45 // the method's formal receiver base type, nor was the receiver addressable.
46 func LookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (obj Object, index []int, indirect bool) {
48 panic("LookupFieldOrMethod on nil type")
51 // Methods cannot be associated to a named pointer type.
52 // (spec: "The type denoted by T is called the receiver base type;
53 // it must not be a pointer or interface type and it must be declared
54 // in the same package as the method.").
55 // Thus, if we have a named pointer type, proceed with the underlying
56 // pointer type but discard the result if it is a method since we would
57 // not have found it for T (see also go.dev/issue/8590).
58 if t, _ := T.(*Named); t != nil {
59 if p, _ := t.Underlying().(*Pointer); p != nil {
60 obj, index, indirect = lookupFieldOrMethodImpl(p, false, pkg, name, false)
61 if _, ok := obj.(*Func); ok {
62 return nil, nil, false
68 obj, index, indirect = lookupFieldOrMethodImpl(T, addressable, pkg, name, false)
70 // If we didn't find anything and if we have a type parameter with a core type,
71 // see if there is a matching field (but not a method, those need to be declared
72 // explicitly in the constraint). If the constraint is a named pointer type (see
73 // above), we are ok here because only fields are accepted as results.
74 const enableTParamFieldLookup = false // see go.dev/issue/51576
75 if enableTParamFieldLookup && obj == nil && isTypeParam(T) {
76 if t := coreType(T); t != nil {
77 obj, index, indirect = lookupFieldOrMethodImpl(t, addressable, pkg, name, false)
78 if _, ok := obj.(*Var); !ok {
79 obj, index, indirect = nil, nil, false // accept fields (variables) only
86 // lookupFieldOrMethodImpl is the implementation of LookupFieldOrMethod.
87 // Notably, in contrast to LookupFieldOrMethod, it won't find struct fields
88 // in base types of defined (*Named) pointer types T. For instance, given
91 // type T *struct{f int}
93 // lookupFieldOrMethodImpl won't find the field f in the defined (*Named) type T
94 // (methods on T are not permitted in the first place).
96 // Thus, lookupFieldOrMethodImpl should only be called by LookupFieldOrMethod
97 // and missingMethod (the latter doesn't care about struct fields).
99 // If foldCase is true, method names are considered equal if they are equal
100 // with case folding.
102 // The resulting object may not be fully type-checked.
103 func lookupFieldOrMethodImpl(T Type, addressable bool, pkg *Package, name string, foldCase bool) (obj Object, index []int, indirect bool) {
104 // WARNING: The code in this function is extremely subtle - do not modify casually!
107 return // blank fields/methods are never found
110 // Importantly, we must not call under before the call to deref below (nor
111 // does deref call under), as doing so could incorrectly result in finding
112 // methods of the pointer base type when T is a (*Named) pointer type.
113 typ, isPtr := deref(T)
115 // *typ where typ is an interface (incl. a type parameter) has no methods.
117 if _, ok := under(typ).(*Interface); ok {
122 // Start with typ as single entry at shallowest depth.
123 current := []embeddedType{{typ, nil, isPtr, false}}
125 // seen tracks named types that we have seen already, allocated lazily.
126 // Used to avoid endless searches in case of recursive types.
128 // We must use a lookup on identity rather than a simple map[*Named]bool as
129 // instantiated types may be identical but not equal.
130 var seen instanceLookup
132 // search current depth
133 for len(current) > 0 {
134 var next []embeddedType // embedded types found at current depth
136 // look for (pkg, name) in all types at current depth
137 for _, e := range current {
140 // If we have a named type, we may have associated methods.
141 // Look for those first.
142 if named, _ := typ.(*Named); named != nil {
143 if alt := seen.lookup(named); alt != nil {
144 // We have seen this type before, at a more shallow depth
145 // (note that multiples of this type at the current depth
146 // were consolidated before). The type at that depth shadows
147 // this same type at the current depth, so we can ignore
153 // look for a matching attached method
154 if i, m := named.lookupMethod(pkg, name, foldCase); m != nil {
156 // caution: method may not have a proper signature yet
157 index = concat(e.index, i)
158 if obj != nil || e.multiples {
159 return nil, index, false // collision
162 indirect = e.indirect
163 continue // we can't have a matching field or interface method
167 switch t := under(typ).(type) {
169 // look for a matching field and collect embedded types
170 for i, f := range t.fields {
171 if f.sameId(pkg, name) {
173 index = concat(e.index, i)
174 if obj != nil || e.multiples {
175 return nil, index, false // collision
178 indirect = e.indirect
179 continue // we can't have a matching interface method
181 // Collect embedded struct fields for searching the next
182 // lower depth, but only if we have not seen a match yet
183 // (if we have a match it is either the desired field or
184 // we have a name collision on the same depth; in either
185 // case we don't need to look further).
186 // Embedded fields are always of the form T or *T where
187 // T is a type name. If e.typ appeared multiple times at
188 // this depth, f.typ appears multiple times at the next
190 if obj == nil && f.embedded {
191 typ, isPtr := deref(f.typ)
192 // TODO(gri) optimization: ignore types that can't
193 // have fields or methods (only Named, Struct, and
194 // Interface types need to be considered).
195 next = append(next, embeddedType{typ, concat(e.index, i), e.indirect || isPtr, e.multiples})
200 // look for a matching method (interface may be a type parameter)
201 if i, m := t.typeSet().LookupMethod(pkg, name, foldCase); m != nil {
203 index = concat(e.index, i)
204 if obj != nil || e.multiples {
205 return nil, index, false // collision
208 indirect = e.indirect
214 // found a potential match
215 // spec: "A method call x.m() is valid if the method set of (the type of) x
216 // contains m and the argument list can be assigned to the parameter
217 // list of m. If x is addressable and &x's method set contains m, x.m()
218 // is shorthand for (&x).m()".
219 if f, _ := obj.(*Func); f != nil {
220 // determine if method has a pointer receiver
221 if f.hasPtrRecv() && !indirect && !addressable {
222 return nil, nil, true // pointer/addressable receiver required
228 current = consolidateMultiples(next)
231 return nil, nil, false // not found
234 // embeddedType represents an embedded type
235 type embeddedType struct {
237 index []int // embedded field indices, starting with index at depth 0
238 indirect bool // if set, there was a pointer indirection on the path to this field
239 multiples bool // if set, typ appears multiple times at this depth
242 // consolidateMultiples collects multiple list entries with the same type
243 // into a single entry marked as containing multiples. The result is the
244 // consolidated list.
245 func consolidateMultiples(list []embeddedType) []embeddedType {
247 return list // at most one entry - nothing to do
250 n := 0 // number of entries w/ unique type
251 prev := make(map[Type]int) // index at which type was previously seen
252 for _, e := range list {
253 if i, found := lookupType(prev, e.typ); found {
254 list[i].multiples = true
265 func lookupType(m map[Type]int, typ Type) (int, bool) {
266 // fast path: maybe the types are equal
267 if i, found := m[typ]; found {
271 for t, i := range m {
272 if Identical(t, typ) {
280 type instanceLookup struct {
281 // buf is used to avoid allocating the map m in the common case of a small
282 // number of instances.
284 m map[*Named][]*Named
287 func (l *instanceLookup) lookup(inst *Named) *Named {
288 for _, t := range l.buf {
289 if t != nil && Identical(inst, t) {
293 for _, t := range l.m[inst.Origin()] {
294 if Identical(inst, t) {
301 func (l *instanceLookup) add(inst *Named) {
302 for i, t := range l.buf {
309 l.m = make(map[*Named][]*Named)
311 insts := l.m[inst.Origin()]
312 l.m[inst.Origin()] = append(insts, inst)
315 // MissingMethod returns (nil, false) if V implements T, otherwise it
316 // returns a missing method required by T and whether it is missing or
317 // just has the wrong type: either a pointer receiver or wrong signature.
319 // For non-interface types V, or if static is set, V implements T if all
320 // methods of T are present in V. Otherwise (V is an interface and static
321 // is not set), MissingMethod only checks that methods of T which are also
322 // present in V have matching types (e.g., for a type assertion x.(T) where
323 // x is of interface type V).
324 func MissingMethod(V Type, T *Interface, static bool) (method *Func, wrongType bool) {
325 return (*Checker)(nil).missingMethod(V, T, static, Identical, nil)
328 // missingMethod is like MissingMethod but accepts a *Checker as receiver,
329 // a comparator equivalent for type comparison, and a *string for error causes.
330 // The receiver may be nil if missingMethod is invoked through an exported
331 // API call (such as MissingMethod), i.e., when all methods have been type-
333 // The underlying type of T must be an interface; T (rather than its under-
334 // lying type) is used for better error messages (reported through *cause).
335 // The comparator is used to compare signatures.
336 // If a method is missing and cause is not nil, *cause describes the error.
337 func (check *Checker) missingMethod(V, T Type, static bool, equivalent func(x, y Type) bool, cause *string) (method *Func, wrongType bool) {
338 methods := under(T).(*Interface).typeSet().methods // T must be an interface
339 if len(methods) == 0 {
354 var m *Func // method on T we're trying to implement
355 var f *Func // method on V, if found (state is one of ok, wrongName, wrongSig)
357 if u, _ := under(V).(*Interface); u != nil {
359 for _, m = range methods {
360 _, f = tset.LookupMethod(m.pkg, m.name, false)
370 if !equivalent(f.typ, m.typ) {
376 for _, m = range methods {
377 obj, index, indirect := lookupFieldOrMethodImpl(V, false, m.pkg, m.name, false)
379 // check if m is ambiguous, on *V, or on V with case-folding
388 obj, _, _ = lookupFieldOrMethodImpl(V, false, m.pkg, m.name, true /* fold case */)
397 // we must have a method (not a struct field)
404 // methods may not have a fully set up signature yet
406 check.objDecl(f, nil)
409 if !equivalent(f.typ, m.typ) {
424 case isInterfacePtr(V):
425 *cause = "(" + check.interfacePtrError(V) + ")"
426 case isInterfacePtr(T):
427 *cause = "(" + check.interfacePtrError(T) + ")"
429 *cause = check.sprintf("(missing method %s)", m.Name())
432 fs, ms := check.funcString(f, false), check.funcString(m, false)
433 *cause = check.sprintf("(missing method %s)\n\t\thave %s\n\t\twant %s",
436 fs, ms := check.funcString(f, false), check.funcString(m, false)
438 // Don't report "want Foo, have Foo".
439 // Add package information to disambiguate (go.dev/issue/54258).
440 fs, ms = check.funcString(f, true), check.funcString(m, true)
442 *cause = check.sprintf("(wrong type for method %s)\n\t\thave %s\n\t\twant %s",
445 *cause = check.sprintf("(ambiguous selector %s.%s)", V, m.Name())
447 *cause = check.sprintf("(method %s has pointer receiver)", m.Name())
449 *cause = check.sprintf("(%s.%s is a field, not a method)", V, m.Name())
455 return m, state == wrongSig || state == ptrRecv
458 func isInterfacePtr(T Type) bool {
459 p, _ := under(T).(*Pointer)
460 return p != nil && IsInterface(p.base)
464 func (check *Checker) interfacePtrError(T Type) string {
465 assert(isInterfacePtr(T))
466 if p, _ := under(T).(*Pointer); isTypeParam(p.base) {
467 return check.sprintf("type %s is pointer to type parameter, not type parameter", T)
469 return check.sprintf("type %s is pointer to interface, not interface", T)
472 // funcString returns a string of the form name + signature for f.
474 func (check *Checker) funcString(f *Func, pkgInfo bool) string {
475 buf := bytes.NewBufferString(f.name)
477 if check != nil && !pkgInfo {
480 w := newTypeWriter(buf, qf)
483 w.signature(f.typ.(*Signature))
487 // assertableTo reports whether a value of type V can be asserted to have type T.
488 // The receiver may be nil if assertableTo is invoked through an exported API call
489 // (such as AssertableTo), i.e., when all methods have been type-checked.
490 // The underlying type of V must be an interface.
491 // If the result is false and cause is not nil, *cause describes the error.
492 // TODO(gri) replace calls to this function with calls to newAssertableTo.
493 func (check *Checker) assertableTo(V, T Type, cause *string) bool {
494 // no static check is required if T is an interface
495 // spec: "If T is an interface type, x.(T) asserts that the
496 // dynamic type of x implements the interface T."
500 // TODO(gri) fix this for generalized interfaces
501 m, _ := check.missingMethod(T, V, false, Identical, cause)
505 // newAssertableTo reports whether a value of type V can be asserted to have type T.
506 // It also implements behavior for interfaces that currently are only permitted
507 // in constraint position (we have not yet defined that behavior in the spec).
508 // The underlying type of V must be an interface.
509 // If the result is false and cause is not nil, *cause is set to the error cause.
510 func (check *Checker) newAssertableTo(V, T Type, cause *string) bool {
511 // no static check is required if T is an interface
512 // spec: "If T is an interface type, x.(T) asserts that the
513 // dynamic type of x implements the interface T."
517 return check.implements(T, V, false, cause)
520 // deref dereferences typ if it is a *Pointer (but not a *Named type
521 // with an underlying pointer type!) and returns its base and true.
522 // Otherwise it returns (typ, false).
523 func deref(typ Type) (Type, bool) {
524 if p, _ := typ.(*Pointer); p != nil {
525 // p.base should never be nil, but be conservative
528 panic("pointer with nil base type (possibly due to an invalid cyclic declaration)")
530 return Typ[Invalid], true
537 // derefStructPtr dereferences typ if it is a (named or unnamed) pointer to a
538 // (named or unnamed) struct and returns its base. Otherwise it returns typ.
539 func derefStructPtr(typ Type) Type {
540 if p, _ := under(typ).(*Pointer); p != nil {
541 if _, ok := under(p.base).(*Struct); ok {
548 // concat returns the result of concatenating list and i.
549 // The result does not share its underlying array with list.
550 func concat(list []int, i int) []int {
552 t = append(t, list...)
556 // fieldIndex returns the index for the field with matching package and name, or a value < 0.
557 func fieldIndex(fields []*Var, pkg *Package, name string) int {
559 for i, f := range fields {
560 if f.sameId(pkg, name) {
568 // lookupMethod returns the index of and method with matching package and name, or (-1, nil).
569 // If foldCase is true, method names are considered equal if they are equal with case folding.
570 func lookupMethod(methods []*Func, pkg *Package, name string, foldCase bool) (int, *Func) {
572 for i, m := range methods {
573 if (m.name == name || foldCase && strings.EqualFold(m.name, name)) && m.sameId(pkg, m.name) {