[PATCH] D44826: Add -Wunused-using, a warning that finds unused using declarations.

[Roman Lebedev via Phabricator via cfe-commits]

lebedev.ri added inline comments.


================
Comment at: include/clang/Basic/DiagnosticSemaKinds.td:282-290
+def warn_unused_using_declaration : Warning<
+  "unused using declaration %0">,
+  InGroup<UnusedUsing>, DefaultIgnore;
+def warn_unused_using_directive : Warning<
+  "unused using directive %0">,
+  InGroup<UnusedUsing>, DefaultIgnore;
+def warn_unused_using_alias : Warning<
----------------
JFYI you can condense it down to just
```
def warn_unused_using_declaration : Warning<
  "unused %select{using declaration|using directive|namespace alias}0 %1">,
  InGroup<UnusedUsing>, DefaultIgnore;
```
if that simplifies the code that actually emits that warning.


https://reviews.llvm.org/D44826