cmd/compile: fix another invalid switch case panic

Very similar fix to the one made in golang.org/cl/65655. This time it's
for switches on interface values, as we look for duplicates in a
different manner to keep types in mind.

As before, add a small regression test.

Updates #22001.
Fixes #22063.

Change-Id: I9a55d08999aeca262ad276b4649b51848a627b02
Reviewed-on: https://go-review.googlesource.com/66450
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

diff --git a/src/cmd/compile/internal/gc/swt.go b/src/cmd/compile/internal/gc/swt.go
index dc285ae91cd5bed2d1bd5f1f7e5a448f560cfc82..08ce8c44edc4f18faba3ffb8f9878a5cdc062da7 100644 (file)
--- a/src/cmd/compile/internal/gc/swt.go
+++ b/src/cmd/compile/internal/gc/swt.go
@@ -640,6 +640,11 @@ func checkDupExprCases(exprname *Node, clauses []*Node) {
                        if ct := consttype(n); ct < 0 || ct == CTBOOL {
                                continue
                        }
+                       // If the value has no type, we have
+                       // already printed an error about it.
+                       if n.Type == nil {
+                               continue
+                       }
                        tv := typeVal{
                                typ: n.Type.LongString(),
                                val: n.Val().Interface(),

diff --git a/test/fixedbugs/issue22063.go b/test/fixedbugs/issue22063.go
new file mode 100644 (file)
index 0000000..bfdb2e0
--- /dev/null
+++ b/test/fixedbugs/issue22063.go
@@ -0,0 +1,17 @@
+// errorcheck
+
+// 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.
+
+// Issue 22063: panic on interface switch case with invalid name
+
+package p
+
+const X = Wrong(0) // ERROR "undefined: Wrong"
+
+func _() {
+       switch interface{}(nil) {
+       case X:
+       }
+}