[PATCH] D21030: [Sema] Fix rejects-valid where parameter pack was not expanded in type alias

[Faisal Vali via cfe-commits]

faisalv added a comment.

Thanks for working on this bug too!


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Comment at: lib/Sema/TreeTransform.h:4784
@@ +4783,3 @@
+            NewType = getDerived().RebuildPackExpansionType(
+                NewType, SourceRange(), Loc, NumExpansions);
+            if (NewType.isNull())
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Any thoughts on the value of threading EllipsisLoc and PatternRange into this function (they are used primarily for a diagnostic that is triggered in Sema if NewType does not contain an unexpandedparameter pack - which would never get triggered here, so it would be ok to pass in invalid sourelocations and sourceranges with an appropriate comment here) - but the fact that RebuildPackExpandionType is a customization point, it might not be a bad idea to preserve them)?
Alternatively, we could forego calling RebuildPackExpansionType - since OldType is decomposed directly into a PackExpansionType -- NewType could be recomposed directly via Context.getPackExpansionType(NewType, NumExpansions=0)?

Which brings me to - when we create the new pack expansion type, shouldn't the NumExpansions be reset to 0?  The fact that we will have a SubstTemplateParameterType replacing the TemplateParameterType within the pattern might influence the answer to that...

Also - we should be able to assert here that *NumExpansions should be one?  Can you think of a case that it wouldn't be?



http://reviews.llvm.org/D21030