[clang] nonblocking/nonallocating attributes (was: nolock/noalloc) (PR #84983)

[Doug Wyatt via cfe-commits]

================
@@ -7525,25 +7525,21 @@ static Attr *getCCTypeAttr(ASTContext &Ctx, ParsedAttr &Attr) {
 
 std::optional<FunctionEffectMode>
 Sema::ActOnEffectExpression(Expr *CondExpr, StringRef AttributeName) {
-  auto BadExpr = [&]() {
-    Diag(CondExpr->getExprLoc(), diag::err_attribute_argument_type)
-        << ("'" + AttributeName.str() + "'") << AANT_ArgumentIntegerConstant
-        << CondExpr->getSourceRange();
+  if (DiagnoseUnexpandedParameterPack(CondExpr))
     return std::nullopt;
-  };
-
-  if (CondExpr->isTypeDependent() || CondExpr->isValueDependent()) {
-    if (CondExpr->containsUnexpandedParameterPack())
-      return BadExpr();
+  if (CondExpr->isTypeDependent() || CondExpr->isValueDependent())
     return FunctionEffectMode::Dependent;
-  }
 
   std::optional<llvm::APSInt> ConditionValue =
       CondExpr->getIntegerConstantExpr(Context);
-  if (!ConditionValue)
-    return BadExpr();
-  return ConditionValue->getExtValue() ? FunctionEffectMode::True
-                                       : FunctionEffectMode::False;
+  if (!ConditionValue) {
+    Diag(CondExpr->getExprLoc(), diag::err_attribute_argument_type)
+        << ("'" + AttributeName.str() + "'") << AANT_ArgumentIntegerConstant
----------------
dougsonos wrote:

The difficulty here is:
- this is a pre-existing diagnostic; I didn't see a need for a new one just for quotes
- the other users  of the pre-existing diagnostic use `<<` with a `ParsedAttr`, which apparently quotes the attribute (?), but this function can be called from `TreeTransform` (for template instantiation), where there is only a `FunctionEffect` (whose name is passed in).

And then there are usages like:
```
    Diag(AttrLoc, diag::err_attribute_argument_type)
        << "vector_size" << AANT_ArgumentIntegerConstant
        << SizeExpr->getSourceRange();
```
, passing a string constant; it would appear that in this case the attribute isn't quoted, which seems inconsistent.

https://github.com/llvm/llvm-project/pull/84983