Ignore implicity casts for zero-as-null-pointer-constant warning

Erich Keane · Erich Keane · commit 818cf5bcb372 · 2017-10-25T20:23:13.000Z
The repro in https://bugs.llvm.org/show_bug.cgi?id=34362 caused the left nullptr to be cast to a int* implicitly, which resulted diagnosing this falsely. Differential Revision: https://reviews.llvm.org/D39301 llvm-svn: 316605
diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
@@ -438,7 +438,7 @@ void Sema::diagnoseNullableToNonnullConversion(QualType DstType,
 void Sema::diagnoseZeroToNullptrConversion(CastKind Kind, const Expr* E) {
   if (Kind != CK_NullToPointer && Kind != CK_NullToMemberPointer)
     return;
-  if (E->getType()->isNullPtrType())
+  if (E->IgnoreParenImpCasts()->getType()->isNullPtrType())
     return;
   // nullptr only exists from C++11 on, so don't warn on its absence earlier.
   if (!getLangOpts().CPlusPlus11)
diff --git a/clang/test/SemaCXX/warn-zero-nullptr.cpp b/clang/test/SemaCXX/warn-zero-nullptr.cpp
@@ -25,3 +25,10 @@ void g() {
 // Warn on these too. Matches gcc and arguably makes sense.
 void* pp = (decltype(nullptr))0; // expected-warning{{zero as null pointer constant}}
 void* pp2 = static_cast<decltype(nullptr)>(0); // expected-warning{{zero as null pointer constant}}
+
+// Shouldn't warn.
+namespace pr34362 {
+struct A { operator int*() { return nullptr; } };
+void func() { if (nullptr == A()) {} }
+void func2() { if ((nullptr) == A()) {} }
+}
