[Clang][Sema] Avoid crashing for va_arg expressions with bool argument

This change fixes a compiler crash that was introduced in https://reviews.llvm.org/D103611: `Sema::BuildVAArgExpr` attempted to retrieve a corresponding signed type for `bool` by calling `ASTContext::getCorrespondingSignedType`.

rdar://86580370

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D116272

clang/lib/Sema/SemaExpr.cpp

@@ -15946,7 +15946,7 @@ ExprResult Sema::BuildVAArgExpr(SourceLocation BuiltinLoc,
       // promoted type and the underlying type are the same except for
       // signedness. Ask the AST for the correctly corresponding type and see
       // if that's compatible.
-      if (!PromoteType.isNull() &&
+      if (!PromoteType.isNull() && !UnderlyingType->isBooleanType() &&
           PromoteType->isUnsignedIntegerType() !=
               UnderlyingType->isUnsignedIntegerType()) {
         UnderlyingType =

clang/test/SemaCXX/varargs.cpp

@@ -53,6 +53,8 @@ void promotable(int a, ...) {
 
   // Ensure that signed vs unsigned doesn't matter either.
   (void)__builtin_va_arg(ap, unsigned int);
+
+  (void)__builtin_va_arg(ap, bool); // expected-warning {{second argument to 'va_arg' is of promotable type 'bool'; this va_arg has undefined behavior because arguments will be promoted to 'int'}}
 }
 
 #if __cplusplus >= 201103L