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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.
// +build go1.7
// +build gc
package gcexportdata_test
import (
"fmt"
"go/ast"
"go/parser"
"go/token"
"go/types"
"log"
"os"
"path/filepath"
"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)
fmt.Printf("Export data: %s\n", filepath.Base(filename))
// 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)
}
// Print package information.
fmt.Printf("Package members: %s...\n", pkg.Scope().Names()[:5])
println := pkg.Scope().Lookup("Println")
posn := fset.Position(println.Pos())
posn.Line = 123 // make example deterministic
fmt.Printf("Println type: %s\n", println.Type())
fmt.Printf("Println location: %s\n", slashify(posn))
// Output:
//
// Package path: fmt
// Export data: fmt.a
// Package members: [Errorf Formatter Fprint Fprintf Fprintln]...
// Println type: func(a ...interface{}) (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 myscanner
// choosing a package that is unlikely to change across releases
import "text/scanner"
const eof = scanner.EOF
`
fset := token.NewFileSet()
f, err := parser.ParseFile(fset, "myscanner.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("myscanner", fset, []*ast.File{f}, nil)
if err != nil {
log.Fatal(err)
}
// object from imported package
pi := packages["text/scanner"].Scope().Lookup("EOF")
fmt.Printf("const %s.%s %s = %s // %s\n",
pi.Pkg().Path(),
pi.Name(),
pi.Type(),
pi.(*types.Const).Val(),
slashify(fset.Position(pi.Pos())),
)
// object in source package
twopi := pkg.Scope().Lookup("eof")
fmt.Printf("const %s %s = %s // %s\n",
twopi.Name(),
twopi.Type(),
twopi.(*types.Const).Val(),
slashify(fset.Position(twopi.Pos())),
)
// Output:
//
// const text/scanner.EOF untyped int = -1 // $GOROOT/src/text/scanner/scanner.go:75:1
// const eof untyped int = -1 // myscanner.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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