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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/parser"
"go/token"
"go/types"
"log"
"golang.org/x/exp/typeparams"
)
const src = `
//!+input
package p
type Pair[L, R any] struct {
left L
right R
}
func (p Pair[L, _]) Left() L {
return p.left
}
func (p Pair[_, R]) Right() R {
return p.right
}
var IntPair Pair[int, int]
//!-input
`
// !+printmethods
func PrintMethods(pkg *types.Package) {
// Look up *Named types in the package scope.
lookup := func(name string) *types.Named {
return pkg.Scope().Lookup(name).Type().(*types.Named)
}
Pair := lookup("Pair")
IntPair := lookup("IntPair")
PrintMethodSet("Pair", Pair)
PrintMethodSet("Pair[int, int]", IntPair)
LeftObj, _, _ := types.LookupFieldOrMethod(Pair, false, pkg, "Left")
LeftRecvType := LeftObj.Type().(*types.Signature).Recv().Type()
PrintMethodSet("Pair[L, _]", LeftRecvType)
}
func PrintMethodSet(name string, typ types.Type) {
fmt.Println(name + ":")
methodSet := types.NewMethodSet(typ)
for i := 0; i < methodSet.Len(); i++ {
method := methodSet.At(i).Obj()
fmt.Println(method)
}
fmt.Println()
}
//!-printmethods
/*
//!+printoutput
Pair:
func (p.Pair[L, _]).Left() L
func (p.Pair[_, R]).Right() R
Pair[int, int]:
func (p.Pair[int, int]).Left() int
func (p.Pair[int, int]).Right() int
Pair[L, _]:
func (p.Pair[L, _]).Left() L
func (p.Pair[L, _]).Right() _
//!-printoutput
*/
// !+compareorigins
func CompareOrigins(pkg *types.Package) {
Pair := pkg.Scope().Lookup("Pair").Type().(*types.Named)
IntPair := pkg.Scope().Lookup("IntPair").Type().(*types.Named)
Left, _, _ := types.LookupFieldOrMethod(Pair, false, pkg, "Left")
LeftInt, _, _ := types.LookupFieldOrMethod(IntPair, false, pkg, "Left")
fmt.Println("Pair.Left == Pair[int, int].Left:", Left == LeftInt)
origin := typeparams.OriginMethod(LeftInt.(*types.Func))
fmt.Println("Pair.Left == OriginMethod(Pair[int, int].Left):", Left == origin)
}
//!-compareorigins
/*
//!+compareoutput
Pair.Left == Pair[int, int].Left: false
Pair.Left == OriginMethod(Pair[int, int].Left): true
//!-compareoutput
*/
func main() {
fset := token.NewFileSet()
f, err := parser.ParseFile(fset, "hello.go", src, 0)
if err != nil {
log.Fatal(err)
}
conf := types.Config{}
pkg, err := conf.Check("p", fset, []*ast.File{f}, nil)
if err != nil {
log.Fatal(err)
}
fmt.Println("=== PrintMethods ===")
PrintMethods(pkg)
fmt.Println("=== CompareOrigins ===")
CompareOrigins(pkg)
}
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