[clang] Look through parens around reinterpret_cast to emit a warning

clang/docs/ReleaseNotes.rst

@@ -274,6 +274,8 @@ Improvements to Clang's diagnostics
   ``ACQUIRED_AFTER(...)`` have been moved to the stable feature set and no
   longer require ``-Wthread-safety-beta`` to be used.
 
+- Clang now looks through parenthesis for ``-Wundefined-reinterpret-cast`` diagnostic.
+
 Improvements to Clang's time-trace
 ----------------------------------
 

clang/lib/Sema/SemaExpr.cpp

@@ -14774,7 +14774,7 @@ static QualType CheckIndirectionOperand(Sema &S, Expr *Op, ExprValueKind &VK,
   QualType OpTy = Op->getType();
   QualType Result;
 
-  if (isa<CXXReinterpretCastExpr>(Op)) {
+  if (isa<CXXReinterpretCastExpr>(Op->IgnoreParens())) {
     QualType OpOrigType = Op->IgnoreParenCasts()->getType();
     S.CheckCompatibleReinterpretCast(OpOrigType, OpTy, /*IsDereference*/true,
                                      Op->getSourceRange());

clang/test/SemaCXX/reinterpret-cast.cpp

@@ -167,6 +167,10 @@ void dereference_reinterpret_cast() {
   (void)reinterpret_cast<float&>(d);  // expected-warning {{reinterpret_cast from 'double' to 'float &' has undefined behavior}}
   (void)*reinterpret_cast<float*>(&d);  // expected-warning {{dereference of type 'float *' that was reinterpret_cast from type 'double *' has undefined behavior}}
 
+  // Look through parens
+  (void)*(reinterpret_cast<double*>(&l));  // expected-warning {{dereference of type 'double *' that was reinterpret_cast from type 'long *' has undefined behavior}}
+  (void)*((reinterpret_cast<double*>((&l))));  // expected-warning {{dereference of type 'double *' that was reinterpret_cast from type 'long *' has undefined behavior}}
+
   // TODO: add warning for tag types
   (void)reinterpret_cast<A&>(b);
   (void)*reinterpret_cast<A*>(&b);