[PATCH] D128113: Clang: fix AST representation of expanded template arguments.

[Matheus Izvekov via Phabricator via cfe-commits]

mizvekov added a comment.

In D128113#3753624 <https://reviews.llvm.org/D128113#3753624>, @davrec wrote:

> Or just `SubstTemplateTypeParmType` could store this number in addition to its `TemplateTypeParmType`?  (E.g. the first Ts in an expansion is 0, the second Ts in the same expansion is 1, etc. - but it resets for the next expansion.)

Well that number is just the pack_index, as implemented in this current patch :)

I like the idea obviously, this patch is so simple, and simple solutions are the best when they are good enough.

I am not completely sold that this solution is not good enough, it's hard to make the case that the reproducer is a reasonable program, but at the same time it's obvious that packs where designed to deal very cheaply with very large number of arguments.

And this patch does not make the worst case worse: If all arguments are different types in all expansions, then a different pack_index will not cause an extra uniquing because the underlying types will be different as well anyway.


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  https://reviews.llvm.org/D128113/new/

https://reviews.llvm.org/D128113