gofmt: don't crash when rewriting nil interfaces in AST.

The new reflection API makes it an error to call value.Set(x)
if x is invalid. Guard for it.

Added corresponding test case.

Fixes #1696.

R=rsc, r
CC=golang-dev
https://golang.org/cl/4398047

diff --git a/src/cmd/gofmt/gofmt_test.go b/src/cmd/gofmt/gofmt_test.go
index 4ec94e2933006322f1a0ea69bf899f02724ab984..a72530307eeac7c257396750107f7c45d0cf3c41 100644 (file)
--- a/src/cmd/gofmt/gofmt_test.go
+++ b/src/cmd/gofmt/gofmt_test.go
@@ -71,6 +71,7 @@ var tests = []struct {
        {".", "gofmt_test.go", "gofmt_test.go", ""},
        {"testdata", "composites.input", "composites.golden", "-s"},
        {"testdata", "rewrite1.input", "rewrite1.golden", "-r=Foo->Bar"},
+       {"testdata", "rewrite2.input", "rewrite2.golden", "-r=int->bool"},
 }
 
 

diff --git a/src/cmd/gofmt/rewrite.go b/src/cmd/gofmt/rewrite.go
index 93643dced25f933ad41c85d3969af5f917967a8a..631c513310ca49285331ee6dc1a0cdab60039e2b 100644 (file)
--- a/src/cmd/gofmt/rewrite.go
+++ b/src/cmd/gofmt/rewrite.go
@@ -63,6 +63,10 @@ func rewriteFile(pattern, replace ast.Expr, p *ast.File) *ast.File {
        repl := reflect.NewValue(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
                }
@@ -79,6 +83,10 @@ func rewriteFile(pattern, replace ast.Expr, p *ast.File) *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") {
@@ -95,10 +103,12 @@ func setValue(x, y reflect.Value) {
 // Values/types for special cases.
 var (
        objectPtrNil = reflect.NewValue((*ast.Object)(nil))
+       scopePtrNil  = reflect.NewValue((*ast.Scope)(nil))
 
        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 +125,12 @@ 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++ {

diff --git a/src/cmd/gofmt/testdata/rewrite1.golden b/src/cmd/gofmt/testdata/rewrite1.golden
index 3f909ff4ad248e15dd6f1d22547a8d4ddc297f01..d9beb370582c9eb7a392447312f5873886183814 100644 (file)
--- a/src/cmd/gofmt/testdata/rewrite1.golden
+++ b/src/cmd/gofmt/testdata/rewrite1.golden
@@ -1,3 +1,7 @@
+// 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.
+
 package main
 
 type Bar int

diff --git a/src/cmd/gofmt/testdata/rewrite1.input b/src/cmd/gofmt/testdata/rewrite1.input
index 1f10e3601cf0014485e18d0bcc699cdae4e9de6b..bdb894320d37f26417707e82873d94b0b859a34a 100644 (file)
--- a/src/cmd/gofmt/testdata/rewrite1.input
+++ b/src/cmd/gofmt/testdata/rewrite1.input
@@ -1,3 +1,7 @@
+// 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.
+
 package main
 
 type Foo int

diff --git a/src/cmd/gofmt/testdata/rewrite2.golden b/src/cmd/gofmt/testdata/rewrite2.golden
new file mode 100644 (file)
index 0000000..64c67ff
--- /dev/null
+++ b/src/cmd/gofmt/testdata/rewrite2.golden
@@ -0,0 +1,10 @@
+// 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.
+
+package p
+
+// Slices have nil Len values in the corresponding ast.ArrayType
+// node and reflect.NewValue(slice.Len) is an invalid reflect.Value.
+// The rewriter must not crash in that case. Was issue 1696.
+func f() []bool {}

diff --git a/src/cmd/gofmt/testdata/rewrite2.input b/src/cmd/gofmt/testdata/rewrite2.input
new file mode 100644 (file)
index 0000000..2117144
--- /dev/null
+++ b/src/cmd/gofmt/testdata/rewrite2.input
@@ -0,0 +1,10 @@
+// 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.
+
+package p
+
+// Slices have nil Len values in the corresponding ast.ArrayType
+// node and reflect.NewValue(slice.Len) is an invalid reflect.Value.
+// The rewriter must not crash in that case. Was issue 1696.
+func f() []int {}