[all-commits] [llvm/llvm-project] 7284e0: [clang] mangle placeholder for deduced type as a t...

[Matheus Izvekov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 7284e0f3a4f8924a0f69f654db8c4b4d00d232cb
      https://github.com/llvm/llvm-project/commit/7284e0f3a4f8924a0f69f654db8c4b4d00d232cb
  Author: Matheus Izvekov <mizvekov at gmail.com>
  Date:   2024-08-29 (Thu, 29 Aug 2024)

  Changed paths:
    M clang/docs/ReleaseNotes.rst
    M clang/lib/AST/ItaniumMangle.cpp
    A clang/test/CodeGenCXX/GH106182.cpp
    A clang/test/SemaCXX/GH106182.cpp

  Log Message:
  -----------
  [clang] mangle placeholder for deduced type as a template-prefix (#106335)

As agreed on https://github.com/itanium-cxx-abi/cxx-abi/issues/109 these
placeholders should be mangled as a `template-prefix` production.

```
    <template-prefix> ::= <template unqualified-name>           # global template
                      ::= <prefix> <template unqualified-name>  # nested template
                      ::= <template-param>                      # template template parameter
                      ::= <substitution>
```

Previous to this patch, the template template parameter case was not
handled, and template template parameters were incorrectly being handled
as unqualified-names.

Before #95202, DeducedTemplateType was not canonicalized correctly, so
that template template parameter declarations were retained
uncanonicalized.

After #95202, they are correctly canonicalized, but this now leads to
these TTPs being anonymous entities, where the mangling implementation
correctly doesn't expect an anonymous declaration of this kind, leading
to a crash.

Fixes #106182.



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