[Clang] Introduce `CXXTypeidExpr::hasNullCheck` (#95718)

Used to implement CWG2191 where `typeid` for a polymorphic glvalue only
becomes potentially-throwing if the `typeid` operand was already
potentially throwing or a `nullptr` check was inserted:
https://cplusplus.github.io/CWG/issues/2191.html

Also change `Expr::hasSideEffects` for `CXXTypeidExpr` to check the
operand for side-effects instead of always reporting that there are
side-effects

Remove `IsDeref` parameter of `CGCXXABI::shouldTypeidBeNullChecked`
because it should never return `true` if `!IsDeref` (we shouldn't add a
null check that wasn't there in the first place)

1 files changed, 4 insertions, 0 deletions

diff --git a/clang/include/clang/AST/ExprCXX.h b/clang/include/clang/AST/ExprCXX.h
index d2e8d93..c2feac5 100644
--- a/clang/include/clang/AST/ExprCXX.h
+++ b/clang/include/clang/AST/ExprCXX.h
@@ -919,6 +919,10 @@ public:
         reinterpret_cast<Stmt **>(&const_cast<CXXTypeidExpr *>(this)->Operand);
     return const_child_range(begin, begin + 1);
   }
+
+  /// Whether this is of a form like "typeid(*ptr)" that can throw a
+  /// std::bad_typeid if a pointer is a null pointer ([expr.typeid]p2)
+  bool hasNullCheck() const;
 };
 
 /// A member reference to an MSPropertyDecl.