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

[Matheus Izvekov via Phabricator via cfe-commits]

mizvekov added a comment.

In D128113#3744315 <https://reviews.llvm.org/D128113#3744315>, @alexfh wrote:

> The whole project seems like a great improvement in clang diagnostics, but I don't yet see how template parameter pack substitution indices fit into the whole picture. If different type parameters in a parameter pack differ only by some other type of suraring, would they be distinguishable in the current state? How do substitution indices affect this?

We need the pack index just as much as the index.

When we are resugaring some type and we find a SubstTemplateParmType, first we try to find a template specialization in the current naming context (ie a nested name specifier) which refers to the same template as the Subst node.

Then we have to rebuild that Subst node using, as the new underlying type, the template argument which appears in the template specialization we found. To find that argument, first we use the index, which already was available in the AST prior to this patch. But in case that index refers to an argument pack, then we need the pack index to be able to find the argument inside that.


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

https://reviews.llvm.org/D128113