go/internal/gcimporter: fix reexporting compiler data

The current versions of the indexed export format encode constant
values based on their type. However, IExportData was encoding
constants values based on their own kind instead. While cmd/compile
internally keeps these matched, go/types does not guarantee the
same (see also golang/go#43891).

This CL fixes this issue, and also extends testing to check reading in
the compiler's export data and that imported packages can be exported
again.

Change-Id: I08f1845f371edd87773df0ef85bcd4e28f5db2f5
Reviewed-on: https://go-review.googlesource.com/c/tools/+/292351
gopls-CI: kokoro <noreply+kokoro@google.com>
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>

go/internal/gcimporter/bexport_test.go

@@ -12,6 +12,7 @@ import (
 	"go/parser"
 	"go/token"
 	"go/types"
+	"path/filepath"
 	"reflect"
 	"runtime"
 	"strings"
@@ -117,7 +118,8 @@ type UnknownType undefined
 
 func fileLine(fset *token.FileSet, obj types.Object) string {
 	posn := fset.Position(obj.Pos())
-	return fmt.Sprintf("%s:%d", posn.Filename, posn.Line)
+	filename := filepath.Clean(strings.ReplaceAll(posn.Filename, "$GOROOT", build.Default.GOROOT))
+	return fmt.Sprintf("%s:%d", filename, posn.Line)
 }
 
 // equalObj reports how x and y differ.  They are assumed to belong to

go/internal/gcimporter/iexport.go

@@ -472,10 +472,10 @@ func (w *exportWriter) param(obj types.Object) {
 func (w *exportWriter) value(typ types.Type, v constant.Value) {
 	w.typ(typ, nil)
 
-	switch v.Kind() {
-	case constant.Bool:
+	switch b := typ.Underlying().(*types.Basic); b.Info() & types.IsConstType {
+	case types.IsBoolean:
 		w.bool(constant.BoolVal(v))
-	case constant.Int:
+	case types.IsInteger:
 		var i big.Int
 		if i64, exact := constant.Int64Val(v); exact {
 			i.SetInt64(i64)
@@ -485,25 +485,27 @@ func (w *exportWriter) value(typ types.Type, v constant.Value) {
 			i.SetString(v.ExactString(), 10)
 		}
 		w.mpint(&i, typ)
-	case constant.Float:
+	case types.IsFloat:
 		f := constantToFloat(v)
 		w.mpfloat(f, typ)
-	case constant.Complex:
+	case types.IsComplex:
 		w.mpfloat(constantToFloat(constant.Real(v)), typ)
 		w.mpfloat(constantToFloat(constant.Imag(v)), typ)
-	case constant.String:
+	case types.IsString:
 		w.string(constant.StringVal(v))
-	case constant.Unknown:
-		// package contains type errors
 	default:
-		panic(internalErrorf("unexpected value %v (%T)", v, v))
+		if b.Kind() == types.Invalid {
+			// package contains type errors
+			break
+		}
+		panic(internalErrorf("unexpected type %v (%v)", typ, typ.Underlying()))
 	}
 }
 
 // constantToFloat converts a constant.Value with kind constant.Float to a
 // big.Float.
 func constantToFloat(x constant.Value) *big.Float {
-	assert(x.Kind() == constant.Float)
+	x = constant.ToFloat(x)
 	// Use the same floating-point precision (512) as cmd/compile
 	// (see Mpprec in cmd/compile/internal/gc/mpfloat.go).
 	const mpprec = 512

go/internal/gcimporter/iexport_test.go

@@ -9,6 +9,7 @@
 package gcimporter_test
 
 import (
+	"bufio"
 	"bytes"
 	"fmt"
 	"go/ast"
@@ -17,7 +18,9 @@ import (
 	"go/parser"
 	"go/token"
 	"go/types"
+	"io/ioutil"
 	"math/big"
+	"os"
 	"reflect"
 	"runtime"
 	"sort"
@@ -29,6 +32,27 @@ import (
 	"golang.org/x/tools/go/loader"
 )
 
+func readExportFile(filename string) ([]byte, error) {
+	f, err := os.Open(filename)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	buf := bufio.NewReader(f)
+	if _, err := gcimporter.FindExportData(buf); err != nil {
+		return nil, err
+	}
+
+	if ch, err := buf.ReadByte(); err != nil {
+		return nil, err
+	} else if ch != 'i' {
+		return nil, fmt.Errorf("unexpected byte: %v", ch)
+	}
+
+	return ioutil.ReadAll(buf)
+}
+
 func iexport(fset *token.FileSet, pkg *types.Package) ([]byte, error) {
 	var buf bytes.Buffer
 	if err := gcimporter.IExportData(&buf, fset, pkg); err != nil {
@@ -54,6 +78,9 @@ func TestIExportData_stdlib(t *testing.T) {
 	conf := loader.Config{
 		Build:       &ctxt,
 		AllowErrors: true,
+		TypeChecker: types.Config{
+			Sizes: types.SizesFor(ctxt.Compiler, ctxt.GOARCH),
+		},
 	}
 	for _, path := range buildutil.AllPackages(conf.Build) {
 		conf.Import(path)
@@ -96,6 +123,16 @@ type UnknownType undefined
 		} else {
 			testPkgData(t, conf.Fset, pkg, exportdata)
 		}
+
+		if pkg.Name() == "main" || pkg.Name() == "haserrors" {
+			// skip; no export data
+		} else if bp, err := ctxt.Import(pkg.Path(), "", build.FindOnly); err != nil {
+			t.Log("warning:", err)
+		} else if exportdata, err := readExportFile(bp.PkgObj); err != nil {
+			t.Log("warning:", err)
+		} else {
+			testPkgData(t, conf.Fset, pkg, exportdata)
+		}
 	}
 }
 
@@ -111,6 +148,10 @@ func testPkgData(t *testing.T, fset *token.FileSet, pkg *types.Package, exportda
 }
 
 func testPkg(t *testing.T, fset *token.FileSet, pkg *types.Package, fset2 *token.FileSet, pkg2 *types.Package) {
+	if _, err := iexport(fset2, pkg2); err != nil {
+		t.Errorf("reexport %q: %v", pkg.Path(), err)
+	}
+
 	// Compare the packages' corresponding members.
 	for _, name := range pkg.Scope().Names() {
 		if !ast.IsExported(name) {