[committed] Add testcase for PR c++/84488

[Jakub Jelinek]

Hi!

This testcase got fixed in r257155 aka PR83942, but unlike
the PR83942 testcase which regressed during 8.x stage1 this one used
to fail before too, so I think it is worth adding another testcase for it.

Tested on x86_64-linux, committed to trunk as obvious.

2018-02-20  Jakub Jelinek  <ja...@redhat.com>

        PR c++/84488
        * g++.dg/warn/Wunused-var-30.C: New test.

--- gcc/testsuite/g++.dg/warn/Wunused-var-30.C.jj       2018-02-20 
17:53:26.539480455 +0100
+++ gcc/testsuite/g++.dg/warn/Wunused-var-30.C  2018-02-20 17:53:18.419481675 
+0100
@@ -0,0 +1,11 @@
+// PR c++/84488
+// { dg-do compile }
+// { dg-options "-Wunused-but-set-variable" }
+
+int
+foo ()
+{
+  enum E { A, B, C, D };
+  double r = 1.0;              // { dg-bogus "set but not used" }
+  return static_cast<E>(r);
+}

        Jakub