cmd/gc: fix spurious "bad negated constant" for complex constants.
Fixes #7648.
LGTM=r, remyoudompheng
R=golang-codereviews, r, remyoudompheng, jscrockett01
CC=golang-codereviews
https://golang.org/cl/80560045
diff --git a/test/fixedbugs/issue7648.go b/test/fixedbugs/issue7648.go
new file mode 100644
index 0000000..b391c4a
--- /dev/null
+++ b/test/fixedbugs/issue7648.go
@@ -0,0 +1,9 @@
+// compiledir
+
+// 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 7648: spurious "bad negated constant" for complex constants.
+
+package ignored
