mirror of https://go.googlesource.com/go
608 lines
20 KiB
Go
608 lines
20 KiB
Go
// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
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// Source: ../../cmd/compile/internal/types2/lookup.go
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// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// This file implements various field and method lookup functions.
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package types
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import (
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"bytes"
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"go/token"
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)
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// Internal use of LookupFieldOrMethod: If the obj result is a method
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// associated with a concrete (non-interface) type, the method's signature
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// may not be fully set up. Call Checker.objDecl(obj, nil) before accessing
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// the method's type.
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// LookupFieldOrMethod looks up a field or method with given package and name
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// in T and returns the corresponding *Var or *Func, an index sequence, and a
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// bool indicating if there were any pointer indirections on the path to the
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// field or method. If addressable is set, T is the type of an addressable
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// variable (only matters for method lookups). T must not be nil.
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//
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// The last index entry is the field or method index in the (possibly embedded)
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// type where the entry was found, either:
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//
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// 1. the list of declared methods of a named type; or
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// 2. the list of all methods (method set) of an interface type; or
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// 3. the list of fields of a struct type.
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//
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// The earlier index entries are the indices of the embedded struct fields
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// traversed to get to the found entry, starting at depth 0.
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//
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// If no entry is found, a nil object is returned. In this case, the returned
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// index and indirect values have the following meaning:
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//
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// - If index != nil, the index sequence points to an ambiguous entry
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// (the same name appeared more than once at the same embedding level).
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//
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// - If indirect is set, a method with a pointer receiver type was found
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// but there was no pointer on the path from the actual receiver type to
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// the method's formal receiver base type, nor was the receiver addressable.
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func LookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (obj Object, index []int, indirect bool) {
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if T == nil {
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panic("LookupFieldOrMethod on nil type")
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}
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return lookupFieldOrMethod(T, addressable, pkg, name, false)
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}
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// lookupFieldOrMethod is like LookupFieldOrMethod but with the additional foldCase parameter
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// (see Object.sameId for the meaning of foldCase).
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func lookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string, foldCase bool) (obj Object, index []int, indirect bool) {
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// Methods cannot be associated to a named pointer type.
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// (spec: "The type denoted by T is called the receiver base type;
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// it must not be a pointer or interface type and it must be declared
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// in the same package as the method.").
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// Thus, if we have a named pointer type, proceed with the underlying
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// pointer type but discard the result if it is a method since we would
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// not have found it for T (see also go.dev/issue/8590).
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if t := asNamed(T); t != nil {
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if p, _ := t.Underlying().(*Pointer); p != nil {
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obj, index, indirect = lookupFieldOrMethodImpl(p, false, pkg, name, foldCase)
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if _, ok := obj.(*Func); ok {
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return nil, nil, false
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}
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return
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}
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}
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obj, index, indirect = lookupFieldOrMethodImpl(T, addressable, pkg, name, foldCase)
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// If we didn't find anything and if we have a type parameter with a core type,
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// see if there is a matching field (but not a method, those need to be declared
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// explicitly in the constraint). If the constraint is a named pointer type (see
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// above), we are ok here because only fields are accepted as results.
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const enableTParamFieldLookup = false // see go.dev/issue/51576
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if enableTParamFieldLookup && obj == nil && isTypeParam(T) {
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if t := coreType(T); t != nil {
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obj, index, indirect = lookupFieldOrMethodImpl(t, addressable, pkg, name, foldCase)
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if _, ok := obj.(*Var); !ok {
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obj, index, indirect = nil, nil, false // accept fields (variables) only
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}
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}
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}
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return
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}
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// lookupFieldOrMethodImpl is the implementation of lookupFieldOrMethod.
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// Notably, in contrast to lookupFieldOrMethod, it won't find struct fields
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// in base types of defined (*Named) pointer types T. For instance, given
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// the declaration:
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//
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// type T *struct{f int}
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//
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// lookupFieldOrMethodImpl won't find the field f in the defined (*Named) type T
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// (methods on T are not permitted in the first place).
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//
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// Thus, lookupFieldOrMethodImpl should only be called by lookupFieldOrMethod
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// and missingMethod (the latter doesn't care about struct fields).
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//
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// The resulting object may not be fully type-checked.
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func lookupFieldOrMethodImpl(T Type, addressable bool, pkg *Package, name string, foldCase bool) (obj Object, index []int, indirect bool) {
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// WARNING: The code in this function is extremely subtle - do not modify casually!
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if name == "_" {
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return // blank fields/methods are never found
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}
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// Importantly, we must not call under before the call to deref below (nor
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// does deref call under), as doing so could incorrectly result in finding
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// methods of the pointer base type when T is a (*Named) pointer type.
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typ, isPtr := deref(T)
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// *typ where typ is an interface (incl. a type parameter) has no methods.
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if isPtr {
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if _, ok := under(typ).(*Interface); ok {
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return
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}
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}
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// Start with typ as single entry at shallowest depth.
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current := []embeddedType{{typ, nil, isPtr, false}}
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// seen tracks named types that we have seen already, allocated lazily.
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// Used to avoid endless searches in case of recursive types.
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//
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// We must use a lookup on identity rather than a simple map[*Named]bool as
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// instantiated types may be identical but not equal.
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var seen instanceLookup
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// search current depth
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for len(current) > 0 {
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var next []embeddedType // embedded types found at current depth
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// look for (pkg, name) in all types at current depth
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for _, e := range current {
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typ := e.typ
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// If we have a named type, we may have associated methods.
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// Look for those first.
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if named := asNamed(typ); named != nil {
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if alt := seen.lookup(named); alt != nil {
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// We have seen this type before, at a more shallow depth
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// (note that multiples of this type at the current depth
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// were consolidated before). The type at that depth shadows
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// this same type at the current depth, so we can ignore
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// this one.
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continue
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}
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seen.add(named)
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// look for a matching attached method
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if i, m := named.lookupMethod(pkg, name, foldCase); m != nil {
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// potential match
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// caution: method may not have a proper signature yet
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index = concat(e.index, i)
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if obj != nil || e.multiples {
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return nil, index, false // collision
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}
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obj = m
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indirect = e.indirect
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continue // we can't have a matching field or interface method
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}
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}
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switch t := under(typ).(type) {
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case *Struct:
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// look for a matching field and collect embedded types
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for i, f := range t.fields {
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if f.sameId(pkg, name, foldCase) {
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assert(f.typ != nil)
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index = concat(e.index, i)
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if obj != nil || e.multiples {
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return nil, index, false // collision
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}
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obj = f
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indirect = e.indirect
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continue // we can't have a matching interface method
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}
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// Collect embedded struct fields for searching the next
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// lower depth, but only if we have not seen a match yet
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// (if we have a match it is either the desired field or
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// we have a name collision on the same depth; in either
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// case we don't need to look further).
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// Embedded fields are always of the form T or *T where
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// T is a type name. If e.typ appeared multiple times at
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// this depth, f.typ appears multiple times at the next
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// depth.
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if obj == nil && f.embedded {
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typ, isPtr := deref(f.typ)
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// TODO(gri) optimization: ignore types that can't
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// have fields or methods (only Named, Struct, and
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// Interface types need to be considered).
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next = append(next, embeddedType{typ, concat(e.index, i), e.indirect || isPtr, e.multiples})
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}
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}
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case *Interface:
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// look for a matching method (interface may be a type parameter)
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if i, m := t.typeSet().LookupMethod(pkg, name, foldCase); m != nil {
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assert(m.typ != nil)
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index = concat(e.index, i)
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if obj != nil || e.multiples {
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return nil, index, false // collision
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}
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obj = m
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indirect = e.indirect
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}
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}
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}
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if obj != nil {
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// found a potential match
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// spec: "A method call x.m() is valid if the method set of (the type of) x
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// contains m and the argument list can be assigned to the parameter
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// list of m. If x is addressable and &x's method set contains m, x.m()
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// is shorthand for (&x).m()".
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if f, _ := obj.(*Func); f != nil {
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// determine if method has a pointer receiver
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if f.hasPtrRecv() && !indirect && !addressable {
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return nil, nil, true // pointer/addressable receiver required
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}
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}
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return
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}
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current = consolidateMultiples(next)
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}
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return nil, nil, false // not found
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}
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// embeddedType represents an embedded type
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type embeddedType struct {
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typ Type
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index []int // embedded field indices, starting with index at depth 0
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indirect bool // if set, there was a pointer indirection on the path to this field
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multiples bool // if set, typ appears multiple times at this depth
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}
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// consolidateMultiples collects multiple list entries with the same type
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// into a single entry marked as containing multiples. The result is the
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// consolidated list.
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func consolidateMultiples(list []embeddedType) []embeddedType {
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if len(list) <= 1 {
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return list // at most one entry - nothing to do
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}
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n := 0 // number of entries w/ unique type
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prev := make(map[Type]int) // index at which type was previously seen
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for _, e := range list {
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if i, found := lookupType(prev, e.typ); found {
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list[i].multiples = true
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// ignore this entry
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} else {
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prev[e.typ] = n
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list[n] = e
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n++
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}
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}
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return list[:n]
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}
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func lookupType(m map[Type]int, typ Type) (int, bool) {
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// fast path: maybe the types are equal
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if i, found := m[typ]; found {
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return i, true
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}
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for t, i := range m {
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if Identical(t, typ) {
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return i, true
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}
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}
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return 0, false
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}
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type instanceLookup struct {
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// buf is used to avoid allocating the map m in the common case of a small
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// number of instances.
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buf [3]*Named
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m map[*Named][]*Named
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}
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func (l *instanceLookup) lookup(inst *Named) *Named {
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for _, t := range l.buf {
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if t != nil && Identical(inst, t) {
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return t
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}
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}
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for _, t := range l.m[inst.Origin()] {
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if Identical(inst, t) {
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return t
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}
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}
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return nil
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}
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func (l *instanceLookup) add(inst *Named) {
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for i, t := range l.buf {
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if t == nil {
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l.buf[i] = inst
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return
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}
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}
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if l.m == nil {
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l.m = make(map[*Named][]*Named)
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}
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insts := l.m[inst.Origin()]
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l.m[inst.Origin()] = append(insts, inst)
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}
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// MissingMethod returns (nil, false) if V implements T, otherwise it
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// returns a missing method required by T and whether it is missing or
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// just has the wrong type: either a pointer receiver or wrong signature.
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//
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// For non-interface types V, or if static is set, V implements T if all
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// methods of T are present in V. Otherwise (V is an interface and static
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// is not set), MissingMethod only checks that methods of T which are also
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// present in V have matching types (e.g., for a type assertion x.(T) where
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// x is of interface type V).
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func MissingMethod(V Type, T *Interface, static bool) (method *Func, wrongType bool) {
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return (*Checker)(nil).missingMethod(V, T, static, Identical, nil)
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}
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// missingMethod is like MissingMethod but accepts a *Checker as receiver,
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// a comparator equivalent for type comparison, and a *string for error causes.
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// The receiver may be nil if missingMethod is invoked through an exported
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// API call (such as MissingMethod), i.e., when all methods have been type-
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// checked.
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// The underlying type of T must be an interface; T (rather than its under-
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// lying type) is used for better error messages (reported through *cause).
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// The comparator is used to compare signatures.
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// If a method is missing and cause is not nil, *cause describes the error.
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func (check *Checker) missingMethod(V, T Type, static bool, equivalent func(x, y Type) bool, cause *string) (method *Func, wrongType bool) {
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methods := under(T).(*Interface).typeSet().methods // T must be an interface
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if len(methods) == 0 {
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return nil, false
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}
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const (
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ok = iota
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notFound
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wrongName
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unexported
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wrongSig
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ambigSel
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ptrRecv
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field
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)
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state := ok
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var m *Func // method on T we're trying to implement
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var f *Func // method on V, if found (state is one of ok, wrongName, wrongSig)
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if u, _ := under(V).(*Interface); u != nil {
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tset := u.typeSet()
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for _, m = range methods {
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_, f = tset.LookupMethod(m.pkg, m.name, false)
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if f == nil {
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if !static {
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continue
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}
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state = notFound
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break
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}
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if !equivalent(f.typ, m.typ) {
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state = wrongSig
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break
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}
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}
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} else {
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for _, m = range methods {
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obj, index, indirect := lookupFieldOrMethodImpl(V, false, m.pkg, m.name, false)
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// check if m is ambiguous, on *V, or on V with case-folding
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if obj == nil {
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switch {
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case index != nil:
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state = ambigSel
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case indirect:
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state = ptrRecv
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default:
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state = notFound
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obj, _, _ = lookupFieldOrMethodImpl(V, false, m.pkg, m.name, true /* fold case */)
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f, _ = obj.(*Func)
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if f != nil {
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state = wrongName
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if f.name == m.name {
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// If the names are equal, f must be unexported
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// (otherwise the package wouldn't matter).
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state = unexported
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}
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}
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}
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break
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}
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// we must have a method (not a struct field)
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f, _ = obj.(*Func)
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if f == nil {
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state = field
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break
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}
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// methods may not have a fully set up signature yet
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if check != nil {
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check.objDecl(f, nil)
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}
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if !equivalent(f.typ, m.typ) {
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state = wrongSig
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break
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}
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}
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}
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if state == ok {
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return nil, false
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}
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if cause != nil {
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if f != nil {
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// This method may be formatted in funcString below, so must have a fully
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// set up signature.
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if check != nil {
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check.objDecl(f, nil)
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}
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}
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switch state {
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case notFound:
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switch {
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case isInterfacePtr(V):
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*cause = "(" + check.interfacePtrError(V) + ")"
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case isInterfacePtr(T):
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*cause = "(" + check.interfacePtrError(T) + ")"
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default:
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*cause = check.sprintf("(missing method %s)", m.Name())
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}
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case wrongName:
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fs, ms := check.funcString(f, false), check.funcString(m, false)
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*cause = check.sprintf("(missing method %s)\n\t\thave %s\n\t\twant %s", m.Name(), fs, ms)
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case unexported:
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*cause = check.sprintf("(unexported method %s)", m.Name())
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case wrongSig:
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fs, ms := check.funcString(f, false), check.funcString(m, false)
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if fs == ms {
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// Don't report "want Foo, have Foo".
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// Add package information to disambiguate (go.dev/issue/54258).
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fs, ms = check.funcString(f, true), check.funcString(m, true)
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}
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if fs == ms {
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// We still have "want Foo, have Foo".
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// This is most likely due to different type parameters with
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// the same name appearing in the instantiated signatures
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// (go.dev/issue/61685).
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// Rather than reporting this misleading error cause, for now
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// just point out that the method signature is incorrect.
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// TODO(gri) should find a good way to report the root cause
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*cause = check.sprintf("(wrong type for method %s)", m.Name())
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break
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}
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*cause = check.sprintf("(wrong type for method %s)\n\t\thave %s\n\t\twant %s", m.Name(), fs, ms)
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case ambigSel:
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*cause = check.sprintf("(ambiguous selector %s.%s)", V, m.Name())
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case ptrRecv:
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*cause = check.sprintf("(method %s has pointer receiver)", m.Name())
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case field:
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*cause = check.sprintf("(%s.%s is a field, not a method)", V, m.Name())
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default:
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panic("unreachable")
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}
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}
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return m, state == wrongSig || state == ptrRecv
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}
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func isInterfacePtr(T Type) bool {
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p, _ := under(T).(*Pointer)
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return p != nil && IsInterface(p.base)
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}
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// check may be nil.
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func (check *Checker) interfacePtrError(T Type) string {
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assert(isInterfacePtr(T))
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if p, _ := under(T).(*Pointer); isTypeParam(p.base) {
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return check.sprintf("type %s is pointer to type parameter, not type parameter", T)
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}
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return check.sprintf("type %s is pointer to interface, not interface", T)
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}
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// funcString returns a string of the form name + signature for f.
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// check may be nil.
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func (check *Checker) funcString(f *Func, pkgInfo bool) string {
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buf := bytes.NewBufferString(f.name)
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var qf Qualifier
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if check != nil && !pkgInfo {
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qf = check.qualifier
|
|
}
|
|
w := newTypeWriter(buf, qf)
|
|
w.pkgInfo = pkgInfo
|
|
w.paramNames = false
|
|
w.signature(f.typ.(*Signature))
|
|
return buf.String()
|
|
}
|
|
|
|
// assertableTo reports whether a value of type V can be asserted to have type T.
|
|
// 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, 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
|
|
}
|
|
// TODO(gri) fix this for generalized interfaces
|
|
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).
|
|
// 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(pos, T, V, false, cause)
|
|
}
|
|
|
|
// 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, _ := Unalias(typ).(*Pointer); p != nil {
|
|
// p.base should never be nil, but be conservative
|
|
if p.base == nil {
|
|
if debug {
|
|
panic("pointer with nil base type (possibly due to an invalid cyclic declaration)")
|
|
}
|
|
return Typ[Invalid], true
|
|
}
|
|
return p.base, true
|
|
}
|
|
return typ, false
|
|
}
|
|
|
|
// derefStructPtr dereferences typ if it is a (named or unnamed) pointer to a
|
|
// (named or unnamed) struct and returns its base. Otherwise it returns typ.
|
|
func derefStructPtr(typ Type) Type {
|
|
if p, _ := under(typ).(*Pointer); p != nil {
|
|
if _, ok := under(p.base).(*Struct); ok {
|
|
return p.base
|
|
}
|
|
}
|
|
return typ
|
|
}
|
|
|
|
// concat returns the result of concatenating list and i.
|
|
// The result does not share its underlying array with list.
|
|
func concat(list []int, i int) []int {
|
|
var t []int
|
|
t = append(t, list...)
|
|
return append(t, i)
|
|
}
|
|
|
|
// fieldIndex returns the index for the field with matching package and name, or a value < 0.
|
|
// See Object.sameId for the meaning of foldCase.
|
|
func fieldIndex(fields []*Var, pkg *Package, name string, foldCase bool) int {
|
|
if name != "_" {
|
|
for i, f := range fields {
|
|
if f.sameId(pkg, name, foldCase) {
|
|
return i
|
|
}
|
|
}
|
|
}
|
|
return -1
|
|
}
|
|
|
|
// methodIndex returns the index of and method with matching package and name, or (-1, nil).
|
|
// See Object.sameId for the meaning of foldCase.
|
|
func methodIndex(methods []*Func, pkg *Package, name string, foldCase bool) (int, *Func) {
|
|
if name != "_" {
|
|
for i, m := range methods {
|
|
if m.sameId(pkg, name, foldCase) {
|
|
return i, m
|
|
}
|
|
}
|
|
}
|
|
return -1, nil
|
|
}
|