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// Copyright 2016 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 go1.7 && gc && !android && !ios && !js
// +build go1.7,gc,!android,!ios,!js
package gcexportdata_test
import (
"fmt"
"go/ast"
"go/parser"
"go/token"
"go/types"
"log"
"os"
"path/filepath"
"strings"
"golang.org/x/tools/go/gcexportdata"
)
// ExampleRead uses gcexportdata.Read to load type information for the
// "fmt" package from the fmt.a file produced by the gc compiler.
func ExampleRead() {
// Find the export data file.
filename, path := gcexportdata.Find("fmt", "")
if filename == "" {
log.Fatalf("can't find export data for fmt")
}
fmt.Printf("Package path: %s\n", path)
// Open and read the file.
f, err := os.Open(filename)
if err != nil {
log.Fatal(err)
}
defer f.Close()
r, err := gcexportdata.NewReader(f)
if err != nil {
log.Fatalf("reading export data %s: %v", filename, err)
}
// Decode the export data.
fset := token.NewFileSet()
imports := make(map[string]*types.Package)
pkg, err := gcexportdata.Read(r, fset, imports, path)
if err != nil {
log.Fatal(err)
}
// We can see all the names in Names.
members := pkg.Scope().Names()
foundPrintln := false
for _, member := range members {
if member == "Println" {
foundPrintln = true
break
}
}
fmt.Print("Package members: ")
if foundPrintln {
fmt.Println("Println found")
} else {
fmt.Println("Println not found")
}
// We can also look up a name directly using Lookup.
println := pkg.Scope().Lookup("Println")
// go 1.18+ uses the 'any' alias
typ := strings.ReplaceAll(println.Type().String(), "interface{}", "any")
fmt.Printf("Println type: %s\n", typ)
posn := fset.Position(println.Pos())
// make example deterministic
posn.Line = 123
fmt.Printf("Println location: %s\n", slashify(posn))
// Output:
//
// Package path: fmt
// Package members: Println found
// Println type: func(a ...any) (n int, err error)
// Println location: $GOROOT/src/fmt/print.go:123:1
}
// ExampleNewImporter demonstrates usage of NewImporter to provide type
// information for dependencies when type-checking Go source code.
func ExampleNewImporter() {
const src = `package myrpc
// choosing a package that doesn't change across releases
import "net/rpc"
const serverError rpc.ServerError = ""
`
fset := token.NewFileSet()
f, err := parser.ParseFile(fset, "myrpc.go", src, 0)
if err != nil {
log.Fatal(err)
}
packages := make(map[string]*types.Package)
imp := gcexportdata.NewImporter(fset, packages)
conf := types.Config{Importer: imp}
pkg, err := conf.Check("myrpc", fset, []*ast.File{f}, nil)
if err != nil {
log.Fatal(err)
}
// object from imported package
pi := packages["net/rpc"].Scope().Lookup("ServerError")
fmt.Printf("type %s.%s %s // %s\n",
pi.Pkg().Path(),
pi.Name(),
pi.Type().Underlying(),
slashify(fset.Position(pi.Pos())),
)
// object in source package
twopi := pkg.Scope().Lookup("serverError")
fmt.Printf("const %s %s = %s // %s\n",
twopi.Name(),
twopi.Type(),
twopi.(*types.Const).Val(),
slashify(fset.Position(twopi.Pos())),
)
// Output:
//
// type net/rpc.ServerError string // $GOROOT/src/net/rpc/client.go:20:1
// const serverError net/rpc.ServerError = "" // myrpc.go:6:7
}
func slashify(posn token.Position) token.Position {
posn.Filename = filepath.ToSlash(posn.Filename) // for MS Windows portability
return posn
}
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