cmd/gc: avoid clobbering the AST in cgen_callmeth.

It confused the detection of init loops when involving
method calls.

Fixes #3890.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/6620067

1 files changed, 35 insertions, 0 deletions

diff --git a/test/fixedbugs/bug459.go b/test/fixedbugs/bug459.go
new file mode 100644
index 0000000000..80abe5d518
--- /dev/null
+++ b/test/fixedbugs/bug459.go
@@ -0,0 +1,35 @@
+// errorcheck
+
+// Copyright 2012 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.
+
+// Issue 3890: missing detection of init loop involving
+// method calls in function bodies.
+
+package flag
+
+var commandLine = NewFlagSet() // ERROR "loop"
+
+type FlagSet struct {
+}
+
+func (f *FlagSet) failf(format string, a ...interface{}) {
+	f.usage()
+}
+
+func (f *FlagSet) usage() {
+	if f == commandLine {
+		panic(3)
+	}
+}
+
+func NewFlagSet() *FlagSet {
+	f := &FlagSet{}
+	f.setErrorHandling(true)
+	return f
+}
+
+func (f *FlagSet) setErrorHandling(b bool) {
+	f.failf("DIE")
+}