diff --git a/go/internal/gcimporter/bexport.go b/go/internal/gcimporter/bexport.go
index 6a9821ae4b..9f65049140 100644
--- a/go/internal/gcimporter/bexport.go
+++ b/go/internal/gcimporter/bexport.go
@@ -209,7 +209,7 @@ func (p *exporter) obj(obj types.Object) {
 		p.value(obj.Val())
 
 	case *types.TypeName:
-		if isAlias(obj) {
+		if obj.IsAlias() {
 			p.tag(aliasTag)
 			p.pos(obj)
 			p.qualifiedName(obj)
diff --git a/go/internal/gcimporter/bexport19_test.go b/go/internal/gcimporter/bexport19_test.go
deleted file mode 100644
index 5c3cf2ddd4..0000000000
--- a/go/internal/gcimporter/bexport19_test.go
+++ /dev/null
@@ -1,96 +0,0 @@
-// 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 go1.9
-
-package gcimporter_test
-
-import (
-	"go/ast"
-	"go/parser"
-	"go/token"
-	"go/types"
-	"testing"
-
-	"golang.org/x/tools/go/internal/gcimporter"
-)
-
-const src = `
-package p
-
-type (
-	T0 = int32
-	T1 = struct{}
-	T2 = struct{ T1 }
-	Invalid = foo // foo is undeclared
-)
-`
-
-func checkPkg(t *testing.T, pkg *types.Package, label string) {
-	T1 := types.NewStruct(nil, nil)
-	T2 := types.NewStruct([]*types.Var{types.NewField(0, pkg, "T1", T1, true)}, nil)
-
-	for _, test := range []struct {
-		name string
-		typ  types.Type
-	}{
-		{"T0", types.Typ[types.Int32]},
-		{"T1", T1},
-		{"T2", T2},
-		{"Invalid", types.Typ[types.Invalid]},
-	} {
-		obj := pkg.Scope().Lookup(test.name)
-		if obj == nil {
-			t.Errorf("%s: %s not found", label, test.name)
-			continue
-		}
-		tname, _ := obj.(*types.TypeName)
-		if tname == nil {
-			t.Errorf("%s: %v not a type name", label, obj)
-			continue
-		}
-		if !tname.IsAlias() {
-			t.Errorf("%s: %v: not marked as alias", label, tname)
-			continue
-		}
-		if got := tname.Type(); !types.Identical(got, test.typ) {
-			t.Errorf("%s: %v: got %v; want %v", label, tname, got, test.typ)
-		}
-	}
-}
-
-func TestTypeAliases(t *testing.T) {
-	// parse and typecheck
-	fset1 := token.NewFileSet()
-	f, err := parser.ParseFile(fset1, "p.go", src, 0)
-	if err != nil {
-		t.Fatal(err)
-	}
-	var conf types.Config
-	pkg1, err := conf.Check("p", fset1, []*ast.File{f}, nil)
-	if err == nil {
-		// foo in undeclared in src; we should see an error
-		t.Fatal("invalid source type-checked without error")
-	}
-	if pkg1 == nil {
-		// despite incorrect src we should see a (partially) type-checked package
-		t.Fatal("nil package returned")
-	}
-	checkPkg(t, pkg1, "export")
-
-	// export
-	exportdata, err := gcimporter.BExportData(fset1, pkg1)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	// import
-	imports := make(map[string]*types.Package)
-	fset2 := token.NewFileSet()
-	_, pkg2, err := gcimporter.BImportData(fset2, imports, exportdata, pkg1.Path())
-	if err != nil {
-		t.Fatalf("BImportData(%s): %v", pkg1.Path(), err)
-	}
-	checkPkg(t, pkg2, "import")
-}
diff --git a/go/internal/gcimporter/bexport_test.go b/go/internal/gcimporter/bexport_test.go
index e78b78db06..3c98a5ec6f 100644
--- a/go/internal/gcimporter/bexport_test.go
+++ b/go/internal/gcimporter/bexport_test.go
@@ -333,3 +333,82 @@ func TestVeryLongFile(t *testing.T) {
 			posn2, want, posn1)
 	}
 }
+
+const src = `
+package p
+
+type (
+	T0 = int32
+	T1 = struct{}
+	T2 = struct{ T1 }
+	Invalid = foo // foo is undeclared
+)
+`
+
+func checkPkg(t *testing.T, pkg *types.Package, label string) {
+	T1 := types.NewStruct(nil, nil)
+	T2 := types.NewStruct([]*types.Var{types.NewField(0, pkg, "T1", T1, true)}, nil)
+
+	for _, test := range []struct {
+		name string
+		typ  types.Type
+	}{
+		{"T0", types.Typ[types.Int32]},
+		{"T1", T1},
+		{"T2", T2},
+		{"Invalid", types.Typ[types.Invalid]},
+	} {
+		obj := pkg.Scope().Lookup(test.name)
+		if obj == nil {
+			t.Errorf("%s: %s not found", label, test.name)
+			continue
+		}
+		tname, _ := obj.(*types.TypeName)
+		if tname == nil {
+			t.Errorf("%s: %v not a type name", label, obj)
+			continue
+		}
+		if !tname.IsAlias() {
+			t.Errorf("%s: %v: not marked as alias", label, tname)
+			continue
+		}
+		if got := tname.Type(); !types.Identical(got, test.typ) {
+			t.Errorf("%s: %v: got %v; want %v", label, tname, got, test.typ)
+		}
+	}
+}
+
+func TestTypeAliases(t *testing.T) {
+	// parse and typecheck
+	fset1 := token.NewFileSet()
+	f, err := parser.ParseFile(fset1, "p.go", src, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var conf types.Config
+	pkg1, err := conf.Check("p", fset1, []*ast.File{f}, nil)
+	if err == nil {
+		// foo in undeclared in src; we should see an error
+		t.Fatal("invalid source type-checked without error")
+	}
+	if pkg1 == nil {
+		// despite incorrect src we should see a (partially) type-checked package
+		t.Fatal("nil package returned")
+	}
+	checkPkg(t, pkg1, "export")
+
+	// export
+	exportdata, err := gcimporter.BExportData(fset1, pkg1)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// import
+	imports := make(map[string]*types.Package)
+	fset2 := token.NewFileSet()
+	_, pkg2, err := gcimporter.BImportData(fset2, imports, exportdata, pkg1.Path())
+	if err != nil {
+		t.Fatalf("BImportData(%s): %v", pkg1.Path(), err)
+	}
+	checkPkg(t, pkg2, "import")
+}
diff --git a/go/internal/gcimporter/isAlias18.go b/go/internal/gcimporter/isAlias18.go
deleted file mode 100644
index 225ffeedfa..0000000000
--- a/go/internal/gcimporter/isAlias18.go
+++ /dev/null
@@ -1,13 +0,0 @@
-// Copyright 2017 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 !go1.9
-
-package gcimporter
-
-import "go/types"
-
-func isAlias(obj *types.TypeName) bool {
-	return false // there are no type aliases before Go 1.9
-}
diff --git a/go/internal/gcimporter/isAlias19.go b/go/internal/gcimporter/isAlias19.go
deleted file mode 100644
index c2025d84a9..0000000000
--- a/go/internal/gcimporter/isAlias19.go
+++ /dev/null
@@ -1,13 +0,0 @@
-// Copyright 2017 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 go1.9
-
-package gcimporter
-
-import "go/types"
-
-func isAlias(obj *types.TypeName) bool {
-	return obj.IsAlias()
-}