[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

llvm-svn: 345111

1 files changed, 6 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 2cee761da3c..98025ca27c6 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -11280,6 +11280,12 @@ static bool IgnoreCommaOperand(const Expr *E) {
     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;