go/gcimporter15: implement support for exporting aliases

Tested with 1.6, 1.7, 1.8.

Change-Id: Ib0f751484c360b02aa34c993ce795cb94656705f
Reviewed-on: https://go-review.googlesource.com/32540
Reviewed-by: Alan Donovan <adonovan@google.com>

go/gcimporter15/bexport.go

@@ -173,6 +173,17 @@ func (p *exporter) pkg(pkg *types.Package, emptypath bool) {
 }
 
 func (p *exporter) obj(obj types.Object) {
+	if orig := original(obj); orig != obj {
+		if orig == nil {
+			// invalid alias - don't export for now (issue 17731)
+			return
+		}
+		p.tag(aliasTag)
+		p.pos(obj)
+		p.string(obj.Name())
+		obj = orig
+	}
+
 	switch obj := obj.(type) {
 	case *types.Const:
 		p.tag(constTag)

go/gcimporter15/gcimporter17_test.go

@@ -35,14 +35,16 @@ func TestImportTestdataNewExport(t *testing.T) {
 		return
 	}
 
-	if outFn := compileNewExport(t, "testdata", "exports.go"); outFn != "" {
+	if outFn := compileNewExport(t, "testdata", testfile); outFn != "" {
 		defer os.Remove(outFn)
 	}
 
-	if pkg := testPath(t, "./testdata/exports", "."); pkg != nil {
+	// filename should end with ".go"
+	filename := testfile[:len(testfile)-3]
+	if pkg := testPath(t, "./testdata/"+filename, "."); pkg != nil {
 		// The package's Imports list must include all packages
-		// explicitly imported by exports.go, plus all packages
+		// explicitly imported by testfile, plus all packages
-		// referenced indirectly via exported objects in exports.go.
+		// referenced indirectly via exported objects in testfile.
 		want := `[package ast ("go/ast") package token ("go/token")]`
 		got := fmt.Sprint(pkg.Imports())
 		if got != want {

go/gcimporter15/gcimporter_test.go

@@ -137,14 +137,16 @@ func TestImportTestdata(t *testing.T) {
 		return
 	}
 
-	if outFn := compile(t, "testdata", "exports.go"); outFn != "" {
+	if outFn := compile(t, "testdata", testfile); outFn != "" {
 		defer os.Remove(outFn)
 	}
 
-	if pkg := testPath(t, "./testdata/exports", "."); pkg != nil {
+	// filename should end with ".go"
+	filename := testfile[:len(testfile)-3]
+	if pkg := testPath(t, "./testdata/"+filename, "."); pkg != nil {
 		// The package's Imports list must include all packages
-		// explicitly imported by exports.go, plus all packages
+		// explicitly imported by testfile, plus all packages
-		// referenced indirectly via exported objects in exports.go.
+		// referenced indirectly via exported objects in testfile.
 		// With the textual export format, the list may also include
 		// additional packages that are not strictly required for
 		// import processing alone (they are exported to err "on

go/gcimporter15/newalias16.go

@@ -15,3 +15,9 @@ func newAlias(pos token.Pos, pkg *types.Package, name string, orig types.Object)
 	errorf("unexpected alias in non-Go1.8 export data: %s.%s => %v", pkg.Name(), name, orig)
 	panic("unreachable")
 }
+
+func original(obj types.Object) types.Object {
+	return obj // don't know about aliases
+}
+
+const testfile = "exports17.go"

go/gcimporter15/newalias18.go

@@ -9,3 +9,13 @@ package gcimporter
 import "go/types"
 
 func newAlias => types.NewAlias
+
+// TODO(gri) Consider exporting this functionality from go/types (issue 17730).
+func original(obj types.Object) types.Object {
+	if orig, ok := obj.(*types.Alias); ok {
+		return orig
+	}
+	return obj
+}
+
+const testfile = "exports18.go"

go/gcimporter15/testdata/exports18.go

@@ -0,0 +1,109 @@
+// Copyright 2011 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.
+
+// This file is used to generate an object file which
+// serves as test file for gcimporter_test.go.
+
+package exports
+
+import (
+	"go/ast"
+	"go/build"
+	"math"
+)
+
+// Issue 3682: Correctly read dotted identifiers from export data.
+const init1 = 0
+
+func init() {}
+
+const (
+	C0 int = 0
+	C1     = 3.14159265
+	C2     = 2.718281828i
+	C3     = -123.456e-789
+	C4     = +123.456E+789
+	C5     = 1234i
+	C6     = "foo\n"
+	C7     = `bar\n`
+)
+
+const (
+	C8 => math.Pi
+)
+
+type (
+	T1  int
+	T2  [10]int
+	T3  []int
+	T4  *int
+	T5  chan int
+	T6a chan<- int
+	T6b chan (<-chan int)
+	T6c chan<- (chan int)
+	T7  <-chan *ast.File
+	T8  struct{}
+	T9  struct {
+		a    int
+		b, c float32
+		d    []string `go:"tag"`
+	}
+	T10 struct {
+		T8
+		T9
+		_ *T10
+	}
+	T11 map[int]string
+	T12 interface{}
+	T13 interface {
+		m1()
+		m2(int) float32
+	}
+	T14 interface {
+		T12
+		T13
+		m3(x ...struct{}) []T9
+	}
+	T15 func()
+	T16 func(int)
+	T17 func(x int)
+	T18 func() float32
+	T19 func() (x float32)
+	T20 func(...interface{})
+	T21 struct{ next *T21 }
+	T22 struct{ link *T23 }
+	T23 struct{ link *T22 }
+	T24 *T24
+	T25 *T26
+	T26 *T27
+	T27 *T25
+	T28 func(T28) T28
+)
+
+type (
+	T29 => ast.File
+	T30 => build.Context
+)
+
+var (
+	V0 int
+	V1         = -991.0
+	V2 float32 = 1.2
+)
+
+var (
+	V3 => build.Default
+)
+
+func F1()         {}
+func F2(x int)    {}
+func F3() int     { return 0 }
+func F4() float32 { return 0 }
+func F5(a, b, c int, u, v, w struct{ x, y T1 }, more ...interface{}) (p, q, r chan<- T10)
+
+func (p *T1) M1()
+
+func F6 => math.Sin
+func F7 => ast.IsExported
+func F8 => build.Import