r345111 - [Sema] Fix -Wcomma in dependent context

[Richard Trieu via cfe-commits]

Author: rtrieu
Date: Tue Oct 23 19:07:41 2018
New Revision: 345111

URL: http://llvm.org/viewvc/llvm-project?rev=345111&view=rev
Log:
[Sema] Fix -Wcomma in dependent context

When there is a dependent type inside a cast, the CastKind becomes CK_Dependent
instead of CK_ToVoid.  This fix will check that there is a dependent cast,
the original type is dependent, and the target type is void to ignore the cast.

https://bugs.llvm.org/show_bug.cgi?id=39375

Modified:
    cfe/trunk/lib/Sema/SemaExpr.cpp
    cfe/trunk/test/SemaCXX/warn-comma-operator.cpp

Modified: cfe/trunk/lib/Sema/SemaExpr.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=345111&r1=345110&r2=345111&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaExpr.cpp (original)
+++ cfe/trunk/lib/Sema/SemaExpr.cpp Tue Oct 23 19:07:41 2018
@@ -11280,6 +11280,12 @@ static bool IgnoreCommaOperand(const Exp
     if (CE->getCastKind() == CK_ToVoid) {
       return true;
     }
+
+    // static_cast<void> on a dependent type will not show up as CK_ToVoid.
+    if (CE->getCastKind() == CK_Dependent && E->getType()->isVoidType() &&
+        CE->getSubExpr()->getType()->isDependentType()) {
+      return true;
+    }
   }
 
   return false;

Modified: cfe/trunk/test/SemaCXX/warn-comma-operator.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/warn-comma-operator.cpp?rev=345111&r1=345110&r2=345111&view=diff
==============================================================================
--- cfe/trunk/test/SemaCXX/warn-comma-operator.cpp (original)
+++ cfe/trunk/test/SemaCXX/warn-comma-operator.cpp Tue Oct 23 19:07:41 2018
@@ -276,3 +276,13 @@ void test14() {
   // CHECK: fix-it:{{.*}}:{[[@LINE-7]]:33-[[@LINE-7]]:33}:"static_cast<void>("
   // CHECK: fix-it:{{.*}}:{[[@LINE-8]]:46-[[@LINE-8]]:46}:")"
 }
+
+// PR39375 - test cast to void to silence warnings
+template <typename T>
+void test15() {
+  (void)42, 0;
+  static_cast<void>(42), 0;
+
+  (void)T{}, 0;
+  static_cast<void>(T{}), 0;
+}