[clang] [libcxx] [Clang] Add __builtin_invoke and use it in libc++ (PR #116709)

[Aaron Ballman via cfe-commits]

================
@@ -5406,6 +5408,99 @@ ExprResult Sema::ConvertVectorExpr(Expr *E, TypeSourceInfo *TInfo,
                                    RParenLoc, CurFPFeatureOverrides());
 }
 
+ExprResult Sema::BuiltinInvoke(CallExpr *TheCall) {
+  SourceLocation Loc = TheCall->getBeginLoc();
+  auto Args = MutableArrayRef(TheCall->getArgs(), TheCall->getNumArgs());
+  assert(llvm::none_of(Args,
+                       [](Expr *Arg) { return Arg->isTypeDependent(); }));
+
+  if (Args.size() == 0) {
+    Diag(TheCall->getBeginLoc(), diag::err_typecheck_call_too_few_args_at_least)
+        << /*callee_type=*/0 << /*min_arg_count=*/1 << /*actual_arg_count=*/0
+        << /*is_non_object=*/0 << TheCall->getSourceRange();
+    return ExprError();
+  }
+
+  auto FuncT = Args[0]->getType();
+
+  if (auto *MPT = FuncT->getAs<MemberPointerType>()) {
----------------
AaronBallman wrote:

```suggestion
  if (const auto *MPT = FuncT->getAs<MemberPointerType>()) {
```
You can make this same kind of correction elsewhere; best to try to aim for const correctness where it's not virally annoying.

https://github.com/llvm/llvm-project/pull/116709