-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
import (
"bytes"
+ "go/token"
"strings"
)
// in the same package as the method.").
// Thus, if we have a named pointer type, proceed with the underlying
// pointer type but discard the result if it is a method since we would
- // not have found it for T (see also issue 8590).
- if t, _ := T.(*Named); t != nil {
+ // not have found it for T (see also go.dev/issue/8590).
+ if t := asNamed(T); t != nil {
if p, _ := t.Underlying().(*Pointer); p != nil {
- obj, index, indirect = lookupFieldOrMethod(p, false, pkg, name, false)
+ obj, index, indirect = lookupFieldOrMethodImpl(p, false, pkg, name, false)
if _, ok := obj.(*Func); ok {
return nil, nil, false
}
}
}
- obj, index, indirect = lookupFieldOrMethod(T, addressable, pkg, name, false)
+ obj, index, indirect = lookupFieldOrMethodImpl(T, addressable, pkg, name, false)
// If we didn't find anything and if we have a type parameter with a core type,
// see if there is a matching field (but not a method, those need to be declared
// explicitly in the constraint). If the constraint is a named pointer type (see
// above), we are ok here because only fields are accepted as results.
- const enableTParamFieldLookup = false // see issue #51576
+ const enableTParamFieldLookup = false // see go.dev/issue/51576
if enableTParamFieldLookup && obj == nil && isTypeParam(T) {
if t := coreType(T); t != nil {
- obj, index, indirect = lookupFieldOrMethod(t, addressable, pkg, name, false)
+ obj, index, indirect = lookupFieldOrMethodImpl(t, addressable, pkg, name, false)
if _, ok := obj.(*Var); !ok {
obj, index, indirect = nil, nil, false // accept fields (variables) only
}
return
}
-// lookupFieldOrMethod should only be called by LookupFieldOrMethod and missingMethod.
-// If foldCase is true, the lookup for methods will include looking for any method
-// which case-folds to the same as 'name' (used for giving helpful error messages).
+// lookupFieldOrMethodImpl is the implementation of LookupFieldOrMethod.
+// Notably, in contrast to LookupFieldOrMethod, it won't find struct fields
+// in base types of defined (*Named) pointer types T. For instance, given
+// the declaration:
+//
+// type T *struct{f int}
+//
+// lookupFieldOrMethodImpl won't find the field f in the defined (*Named) type T
+// (methods on T are not permitted in the first place).
+//
+// Thus, lookupFieldOrMethodImpl should only be called by LookupFieldOrMethod
+// and missingMethod (the latter doesn't care about struct fields).
+//
+// If foldCase is true, method names are considered equal if they are equal
+// with case folding.
//
// The resulting object may not be fully type-checked.
-func lookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string, foldCase bool) (obj Object, index []int, indirect bool) {
+func lookupFieldOrMethodImpl(T Type, addressable bool, pkg *Package, name string, foldCase bool) (obj Object, index []int, indirect bool) {
// WARNING: The code in this function is extremely subtle - do not modify casually!
if name == "_" {
return // blank fields/methods are never found
}
+ // Importantly, we must not call under before the call to deref below (nor
+ // does deref call under), as doing so could incorrectly result in finding
+ // methods of the pointer base type when T is a (*Named) pointer type.
typ, isPtr := deref(T)
// *typ where typ is an interface (incl. a type parameter) has no methods.
// If we have a named type, we may have associated methods.
// Look for those first.
- if named, _ := typ.(*Named); named != nil {
+ if named := asNamed(typ); named != nil {
if alt := seen.lookup(named); alt != nil {
// We have seen this type before, at a more shallow depth
// (note that multiples of this type at the current depth
// 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.
+// just has the wrong type: either a pointer receiver or wrong signature.
//
// For non-interface types V, or if static is set, V implements T if all
// methods of T are present in V. Otherwise (V is an interface and static
// present in V have matching types (e.g., for a type assertion x.(T) where
// x is of interface type V).
func MissingMethod(V Type, T *Interface, static bool) (method *Func, wrongType bool) {
- m, alt := (*Checker)(nil).missingMethod(V, T, static)
- // Only report a wrong type if the alternative method has the same name as m.
- return m, alt != nil && alt.name == m.name // alt != nil implies m != nil
+ return (*Checker)(nil).missingMethod(V, T, static, Identical, nil)
}
-// missingMethod is like MissingMethod but accepts a *Checker as receiver.
+// missingMethod is like MissingMethod but accepts a *Checker as receiver,
+// a comparator equivalent for type comparison, and a *string for error causes.
// The receiver may be nil if missingMethod is invoked through an exported
// API call (such as MissingMethod), i.e., when all methods have been type-
// checked.
-//
-// If a method is missing on T but is found on *T, or if a method is found
-// on T when looked up with case-folding, this alternative method is returned
-// as the second result.
-func (check *Checker) missingMethod(V Type, T *Interface, static bool) (method, alt *Func) {
- if T.NumMethods() == 0 {
- return
+// The underlying type of T must be an interface; T (rather than its under-
+// lying type) is used for better error messages (reported through *cause).
+// The comparator is used to compare signatures.
+// If a method is missing and cause is not nil, *cause describes the error.
+func (check *Checker) missingMethod(V, T Type, static bool, equivalent func(x, y Type) bool, cause *string) (method *Func, wrongType bool) {
+ methods := under(T).(*Interface).typeSet().methods // T must be an interface
+ if len(methods) == 0 {
+ return nil, false
}
- // V is an interface
+ const (
+ ok = iota
+ notFound
+ wrongName
+ wrongSig
+ ambigSel
+ ptrRecv
+ field
+ )
+
+ state := ok
+ var m *Func // method on T we're trying to implement
+ var f *Func // method on V, if found (state is one of ok, wrongName, wrongSig)
+
if u, _ := under(V).(*Interface); u != nil {
tset := u.typeSet()
- for _, m := range T.typeSet().methods {
- _, f := tset.LookupMethod(m.pkg, m.name, false)
+ for _, m = range methods {
+ _, f = tset.LookupMethod(m.pkg, m.name, false)
if f == nil {
if !static {
continue
}
- return m, nil
+ state = notFound
+ break
}
- if !Identical(f.typ, m.typ) {
- return m, f
+ if !equivalent(f.typ, m.typ) {
+ state = wrongSig
+ break
}
}
+ } else {
+ for _, m = range methods {
+ obj, index, indirect := lookupFieldOrMethodImpl(V, false, m.pkg, m.name, false)
- return
- }
-
- // V is not an interface
- for _, m := range T.typeSet().methods {
- // TODO(gri) should this be calling LookupFieldOrMethod instead (and why not)?
- obj, _, _ := lookupFieldOrMethod(V, false, m.pkg, m.name, false)
-
- // check if m is on *V, or on V with case-folding
- found := obj != nil
- if !found {
- // TODO(gri) Instead of NewPointer(V) below, can we just set the "addressable" argument?
- obj, _, _ = lookupFieldOrMethod(NewPointer(V), false, m.pkg, m.name, false)
+ // check if m is ambiguous, on *V, or on V with case-folding
if obj == nil {
- obj, _, _ = lookupFieldOrMethod(V, false, m.pkg, m.name, true /* fold case */)
+ switch {
+ case index != nil:
+ state = ambigSel
+ case indirect:
+ state = ptrRecv
+ default:
+ state = notFound
+ obj, _, _ = lookupFieldOrMethodImpl(V, false, m.pkg, m.name, true /* fold case */)
+ f, _ = obj.(*Func)
+ if f != nil {
+ state = wrongName
+ }
+ }
+ break
}
- }
- // we must have a method (not a struct field)
- f, _ := obj.(*Func)
- if f == nil {
- return m, nil
- }
+ // we must have a method (not a struct field)
+ f, _ = obj.(*Func)
+ if f == nil {
+ state = field
+ break
+ }
- // methods may not have a fully set up signature yet
- if check != nil {
- check.objDecl(f, nil)
- }
+ // methods may not have a fully set up signature yet
+ if check != nil {
+ check.objDecl(f, nil)
+ }
- if !found || !Identical(f.typ, m.typ) {
- return m, f
+ if !equivalent(f.typ, m.typ) {
+ state = wrongSig
+ break
+ }
}
}
- return
-}
-
-// missingMethodCause returns a string giving the detailed cause for a missing method m,
-// where m is missing from V, but required by T. It puts the cause in parentheses,
-// and may include more have/want info after that. If non-nil, alt is a relevant
-// method that matches in some way. It may have the correct name, but wrong type, or
-// it may have a pointer receiver, or it may have the correct name except wrong case.
-// check may be nil.
-func (check *Checker) missingMethodCause(V, T Type, m, alt *Func) string {
- mname := "method " + m.Name()
-
- if alt != nil {
- if m.Name() != alt.Name() {
- return check.sprintf("(missing %s)\n\t\thave %s\n\t\twant %s",
- mname, check.funcString(alt, false), check.funcString(m, false))
- }
+ if state == ok {
+ return nil, false
+ }
- if Identical(m.typ, alt.typ) {
- return check.sprintf("(%s has pointer receiver)", mname)
+ if cause != nil {
+ if f != nil {
+ // This method may be formatted in funcString below, so must have a fully
+ // set up signature.
+ if check != nil {
+ check.objDecl(f, nil)
+ }
}
-
- altS, mS := check.funcString(alt, false), check.funcString(m, false)
- if altS == mS {
- // Would tell the user that Foo isn't a Foo, add package information to disambiguate. See #54258.
- altS, mS = check.funcString(alt, true), check.funcString(m, true)
+ switch state {
+ case notFound:
+ switch {
+ case isInterfacePtr(V):
+ *cause = "(" + check.interfacePtrError(V) + ")"
+ case isInterfacePtr(T):
+ *cause = "(" + check.interfacePtrError(T) + ")"
+ default:
+ *cause = check.sprintf("(missing method %s)", m.Name())
+ }
+ case wrongName:
+ fs, ms := check.funcString(f, false), check.funcString(m, false)
+ *cause = check.sprintf("(missing method %s)\n\t\thave %s\n\t\twant %s",
+ m.Name(), fs, ms)
+ case wrongSig:
+ fs, ms := check.funcString(f, false), check.funcString(m, false)
+ if fs == ms {
+ // Don't report "want Foo, have Foo".
+ // Add package information to disambiguate (go.dev/issue/54258).
+ fs, ms = check.funcString(f, true), check.funcString(m, true)
+ }
+ *cause = check.sprintf("(wrong type for method %s)\n\t\thave %s\n\t\twant %s",
+ m.Name(), fs, ms)
+ case ambigSel:
+ *cause = check.sprintf("(ambiguous selector %s.%s)", V, m.Name())
+ case ptrRecv:
+ *cause = check.sprintf("(method %s has pointer receiver)", m.Name())
+ case field:
+ *cause = check.sprintf("(%s.%s is a field, not a method)", V, m.Name())
+ default:
+ unreachable()
}
-
- return check.sprintf("(wrong type for %s)\n\t\thave %s\n\t\twant %s",
- mname, altS, mS)
}
- if isInterfacePtr(V) {
- return "(" + check.interfacePtrError(V) + ")"
- }
-
- if isInterfacePtr(T) {
- return "(" + check.interfacePtrError(T) + ")"
- }
-
- obj, _, _ := lookupFieldOrMethod(V, true /* auto-deref */, m.pkg, m.name, false)
- if fld, _ := obj.(*Var); fld != nil {
- return check.sprintf("(%s.%s is a field, not a method)", V, fld.Name())
- }
-
- return check.sprintf("(missing %s)", mname)
+ return m, state == wrongSig || state == ptrRecv
}
func isInterfacePtr(T Type) bool {
}
// assertableTo reports whether a value of type V can be asserted to have type T.
-// It returns (nil, false) as affirmative answer. Otherwise it returns a missing
-// method required by V and whether it is missing or just has the wrong type.
// The receiver may be nil if assertableTo is invoked through an exported API call
// (such as AssertableTo), i.e., when all methods have been type-checked.
+// The underlying type of V must be an interface.
+// If the result is false and cause is not nil, *cause describes the error.
// TODO(gri) replace calls to this function with calls to newAssertableTo.
-func (check *Checker) assertableTo(V *Interface, T Type) (method, wrongType *Func) {
+func (check *Checker) assertableTo(V, T Type, cause *string) bool {
// no static check is required if T is an interface
// spec: "If T is an interface type, x.(T) asserts that the
// dynamic type of x implements the interface T."
if IsInterface(T) {
- return
+ return true
}
// TODO(gri) fix this for generalized interfaces
- return check.missingMethod(T, V, false)
+ m, _ := check.missingMethod(T, V, false, Identical, cause)
+ return m == nil
}
// newAssertableTo reports whether a value of type V can be asserted to have type T.
// It also implements behavior for interfaces that currently are only permitted
// in constraint position (we have not yet defined that behavior in the spec).
-func (check *Checker) newAssertableTo(V *Interface, T Type) bool {
+// The underlying type of V must be an interface.
+// If the result is false and cause is not nil, *cause is set to the error cause.
+func (check *Checker) newAssertableTo(pos token.Pos, V, T Type, cause *string) bool {
// no static check is required if T is an interface
// spec: "If T is an interface type, x.(T) asserts that the
// dynamic type of x implements the interface T."
if IsInterface(T) {
return true
}
- return check.implements(T, V, false, nil)
+ return check.implements(pos, T, V, false, cause)
}
-// deref dereferences typ if it is a *Pointer and returns its base and true.
+// deref dereferences typ if it is a *Pointer (but not a *Named type
+// with an underlying pointer type!) and returns its base and true.
// Otherwise it returns (typ, false).
func deref(typ Type) (Type, bool) {
- if p, _ := typ.(*Pointer); p != nil {
+ if p, _ := _Unalias(typ).(*Pointer); p != nil {
// p.base should never be nil, but be conservative
if p.base == nil {
if debug {