1 files changed, 28 insertions, 11 deletions
diff --git a/src/cmd/gofmt/rewrite.go b/src/cmd/gofmt/rewrite.go
index 93643dced..4c24282f3 100644
--- a/src/cmd/gofmt/rewrite.go
+++ b/src/cmd/gofmt/rewrite.go
@@ -19,6 +19,7 @@ import (
 
 func initRewrite() {
 	if *rewriteRule == "" {
+		rewrite = nil // disable any previous rewrite
 		return
 	}
 	f := strings.Split(*rewriteRule, "->", -1)
@@ -59,26 +60,34 @@ func dump(msg string, val reflect.Value) {
 // rewriteFile applies the rewrite rule 'pattern -> replace' to an entire file.
 func rewriteFile(pattern, replace ast.Expr, p *ast.File) *ast.File {
 	m := make(map[string]reflect.Value)
-	pat := reflect.NewValue(pattern)
-	repl := reflect.NewValue(replace)
+	pat := reflect.ValueOf(pattern)
+	repl := reflect.ValueOf(replace)
 	var f func(val reflect.Value) reflect.Value // f is recursive
 	f = func(val reflect.Value) reflect.Value {
+		// don't bother if val is invalid to start with
+		if !val.IsValid() {
+			return reflect.Value{}
+		}
 		for k := range m {
 			m[k] = reflect.Value{}, false
 		}
 		val = apply(f, val)
 		if match(m, pat, val) {
-			val = subst(m, repl, reflect.NewValue(val.Interface().(ast.Node).Pos()))
+			val = subst(m, repl, reflect.ValueOf(val.Interface().(ast.Node).Pos()))
 		}
 		return val
 	}
-	return apply(f, reflect.NewValue(p)).Interface().(*ast.File)
+	return apply(f, reflect.ValueOf(p)).Interface().(*ast.File)
 }
 
 
 // setValue is a wrapper for x.SetValue(y); it protects
 // the caller from panics if x cannot be changed to y.
 func setValue(x, y reflect.Value) {
+	// don't bother if y is invalid to start with
+	if !y.IsValid() {
+		return
+	}
 	defer func() {
 		if x := recover(); x != nil {
 			if s, ok := x.(string); ok && strings.HasPrefix(s, "type mismatch") {
@@ -94,11 +103,13 @@ func setValue(x, y reflect.Value) {
 
 // Values/types for special cases.
 var (
-	objectPtrNil = reflect.NewValue((*ast.Object)(nil))
+	objectPtrNil = reflect.ValueOf((*ast.Object)(nil))
+	scopePtrNil  = reflect.ValueOf((*ast.Scope)(nil))
 
-	identType     = reflect.Typeof((*ast.Ident)(nil))
-	objectPtrType = reflect.Typeof((*ast.Object)(nil))
-	positionType  = reflect.Typeof(token.NoPos)
+	identType     = reflect.TypeOf((*ast.Ident)(nil))
+	objectPtrType = reflect.TypeOf((*ast.Object)(nil))
+	positionType  = reflect.TypeOf(token.NoPos)
+	scopePtrType  = reflect.TypeOf((*ast.Scope)(nil))
 )
 
 
@@ -115,6 +126,12 @@ func apply(f func(reflect.Value) reflect.Value, val reflect.Value) reflect.Value
 		return objectPtrNil
 	}
 
+	// similarly for scopes: they are likely incorrect after a rewrite;
+	// replace them with nil
+	if val.Type() == scopePtrType {
+		return scopePtrNil
+	}
+
 	switch v := reflect.Indirect(val); v.Kind() {
 	case reflect.Slice:
 		for i := 0; i < v.Len(); i++ {
@@ -259,21 +276,21 @@ func subst(m map[string]reflect.Value, pattern reflect.Value, pos reflect.Value)
 		return v
 
 	case reflect.Struct:
-		v := reflect.Zero(p.Type())
+		v := reflect.New(p.Type()).Elem()
 		for i := 0; i < p.NumField(); i++ {
 			v.Field(i).Set(subst(m, p.Field(i), pos))
 		}
 		return v
 
 	case reflect.Ptr:
-		v := reflect.Zero(p.Type())
+		v := reflect.New(p.Type()).Elem()
 		if elem := p.Elem(); elem.IsValid() {
 			v.Set(subst(m, elem, pos).Addr())
 		}
 		return v
 
 	case reflect.Interface:
-		v := reflect.Zero(p.Type())
+		v := reflect.New(p.Type()).Elem()
 		if elem := p.Elem(); elem.IsValid() {
 			v.Set(subst(m, elem, pos))
 		}