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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
package main
import (
"fmt"
"go/ast"
"go/parser"
"go/token"
"go/types"
"log"
)
const src = `
//!+input
package p
type Numeric interface{
~int | ~float64 // etc...
}
func Square[N Numeric](n N) N {
return n*n
}
type Findable interface {
comparable
}
func Find[T Findable](s []T, v T) int {
for i, v2 := range s {
if v2 == v {
return i
}
}
return -1
}
//!-input
`
// !+printsyntax
func PrintNumericSyntax(fset *token.FileSet, file *ast.File) {
// node is the AST node corresponding to the declaration for "Numeric."
node := file.Scope.Lookup("Numeric").Decl.(*ast.TypeSpec)
// Find the embedded syntax node.
embedded := node.Type.(*ast.InterfaceType).Methods.List[0].Type
// Use go/ast's built-in Print function to inspect the parsed syntax.
ast.Print(fset, embedded)
}
//!-printsyntax
/*
//!+outputsyntax
0 *ast.BinaryExpr {
1 . X: *ast.UnaryExpr {
2 . . OpPos: p.go:6:2
3 . . Op: ~
4 . . X: *ast.Ident {
5 . . . NamePos: p.go:6:3
6 . . . Name: "int"
7 . . }
8 . }
9 . OpPos: p.go:6:7
10 . Op: |
11 . Y: *ast.UnaryExpr {
12 . . OpPos: p.go:6:9
13 . . Op: ~
14 . . X: *ast.Ident {
15 . . . NamePos: p.go:6:10
16 . . . Name: "float64"
17 . . }
18 . }
19 }
//!-outputsyntax
*/
// !+printtypes
func PrintInterfaceTypes(fset *token.FileSet, file *ast.File) error {
conf := types.Config{}
pkg, err := conf.Check("hello", fset, []*ast.File{file}, nil)
if err != nil {
return err
}
PrintIface(pkg, "Numeric")
PrintIface(pkg, "Findable")
return nil
}
func PrintIface(pkg *types.Package, name string) {
obj := pkg.Scope().Lookup(name)
fmt.Println(obj)
iface := obj.Type().Underlying().(*types.Interface)
for i := 0; i < iface.NumEmbeddeds(); i++ {
fmt.Printf("\tembeded: %s\n", iface.EmbeddedType(i))
}
for i := 0; i < iface.NumMethods(); i++ {
fmt.Printf("\tembeded: %s\n", iface.EmbeddedType(i))
}
fmt.Printf("\tIsComparable(): %t\n", iface.IsComparable())
fmt.Printf("\tIsMethodSet(): %t\n", iface.IsMethodSet())
}
//!-printtypes
/*
//!+outputtypes
type hello.Numeric interface{~int|~float64}
embeded: ~int|~float64
IsComparable(): true
IsMethodSet(): false
type hello.Findable interface{comparable}
embeded: comparable
IsComparable(): true
IsMethodSet(): false
//!-outputtypes
*/
func main() {
// Parse one file.
fset := token.NewFileSet()
f, err := parser.ParseFile(fset, "p.go", src, 0)
if err != nil {
log.Fatal(err)
}
fmt.Println("=== PrintNumericSyntax ==")
PrintNumericSyntax(fset, f)
fmt.Println("=== PrintInterfaceTypes ==")
if err := PrintInterfaceTypes(fset, f); err != nil {
log.Fatal(err)
}
}
|
