cmd/gc: check duplicate keys in maps with interface{} key type

Fixes issue 7214

LGTM=rsc
R=golang-codereviews, bradfitz, rsc
CC=golang-codereviews, minux.ma
https://codereview.appspot.com/82080044

1 files changed, 30 insertions, 0 deletions

diff --git a/test/fixedbugs/issue7214.go b/test/fixedbugs/issue7214.go
new file mode 100644
index 000000000..82ddf74c3
--- /dev/null
+++ b/test/fixedbugs/issue7214.go
@@ -0,0 +1,30 @@
+// errorcheck
+
+// Copyright 2014 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 7214: No duplicate key error for maps with interface{} key type
+
+package p
+
+var _ = map[interface{}]int{2: 1, 2: 1} // ERROR "duplicate key"
+var _ = map[interface{}]int{int(2): 1, int16(2): 1}
+var _ = map[interface{}]int{int16(2): 1, int16(2): 1} // ERROR "duplicate key"
+
+type S string
+
+var _ = map[interface{}]int{"a": 1, "a": 1} // ERROR "duplicate key"
+var _ = map[interface{}]int{"a": 1, S("a"): 1}
+var _ = map[interface{}]int{S("a"): 1, S("a"): 1} // ERROR "duplicate key"
+
+type I interface {
+	f()
+}
+
+type N int
+
+func (N) f() {}
+
+var _ = map[I]int{N(0): 1, N(2): 1}
+var _ = map[I]int{N(2): 1, N(2): 1} // ERROR "duplicate key"