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// Copyright 2022 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build go1.18
// +build go1.18
package main
import (
"fmt"
"go/ast"
"go/importer"
"go/parser"
"go/token"
"go/types"
"log"
)
const methods = `
//!+input
package methods
type List[E any] []E
func (l List[_]) Len() int {
return len(l)
}
func (l *List[E]) Append(v E) {
*l = append(*l, v)
}
type Pair[L, R comparable] struct {
left L
right R
}
func (p Pair[L, _]) Left() L {
return p.left
}
func (p Pair[_, R]) Right() R {
return p.right
}
func (p Pair[L, R]) Equal(other Pair[L, R]) bool {
return p.Left() == other.Left() && p.Right() == other.Right()
}
//!-input
`
// !+describe
func Describe(fset *token.FileSet, file *ast.File) error {
conf := types.Config{Importer: importer.Default()}
info := &types.Info{
Defs: make(map[*ast.Ident]types.Object),
}
pkg, err := conf.Check("pair", fset, []*ast.File{file}, info)
if err != nil {
return err
}
for _, name := range pkg.Scope().Names() {
obj := pkg.Scope().Lookup(name)
typ := obj.Type().(*types.Named)
fmt.Printf("type %s has %d methods\n", name, typ.NumMethods())
for i := 0; i < typ.NumMethods(); i++ {
m := typ.Method(i)
sig := m.Type().(*types.Signature)
recv := sig.Recv().Type()
fmt.Printf(" %s has %d receiver type parameters\n", m.Name(), sig.RecvTypeParams().Len())
fmt.Printf(" ...and receiver type %+v\n", recv)
}
}
// }
// func foo() {}
for _, decl := range file.Decls {
fdecl, ok := decl.(*ast.FuncDecl)
if !ok {
continue
}
fmt.Printf("Declaration of %q has receiver node type %T\n", fdecl.Name, fdecl.Recv.List[0].Type)
declObj := info.Defs[fdecl.Name]
recvIdent := receiverTypeName(fdecl.Recv.List[0].Type)
typ := pkg.Scope().Lookup(recvIdent.Name).Type().(*types.Named)
// ptr := types.NewPointer(typ)
name := fdecl.Name.Name
methodObj, _, _ := types.LookupFieldOrMethod(typ, false, pkg, name)
if declObj == methodObj {
fmt.Printf(" info.Uses[%s] == types.LookupFieldOrMethod(%s, ..., %q)\n", fdecl.Name, typ, name)
}
}
return nil
}
func receiverTypeName(e ast.Expr) *ast.Ident {
if s, ok := e.(*ast.StarExpr); ok {
e = s.X
}
switch e := e.(type) {
case *ast.IndexExpr:
return e.X.(*ast.Ident)
case *ast.IndexListExpr:
return e.X.(*ast.Ident)
}
panic("unexpected receiver node type")
}
//!-describe
/*
//!+output
> go run golang.org/x/tools/internal/typeparams/example/methoddecls
Pair has 2 methods
Left has 2 receiver type parameters
...and receiver type pair.Pair[L, _]
Right has 2 receiver type parameters
...and receiver type pair.Pair[_, R]
Declaration of "Left" has receiver node type *ast.IndexListExpr
info.Uses[Left] == types.LookupFieldOrMethod(pair.Pair[L, R any], ..., "Left")
Declaration of "Right" has receiver node type *ast.IndexListExpr
info.Uses[Right] == types.LookupFieldOrMethod(pair.Pair[L, R any], ..., "Right")
//!-output
*/
func main() {
// Parse one file.
fset := token.NewFileSet()
f, err := parser.ParseFile(fset, "methods.go", methods, 0)
if err != nil {
log.Fatal(err)
}
if err := Describe(fset, f); err != nil {
log.Fatal(err)
}
}
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