[clang] [Clang] Fix crash when ill-formed code is treated as a deduction guide (PR #67373)

[via cfe-commits]

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@@ -375,6 +375,10 @@ Bug Fixes to C++ Support
 - Fixed a bug causing destructors of constant-evaluated structured bindings
   initialized by array elements to be called in the wrong evaluation context.
 
+- Fix crash where ill-formed code was being treated as a deduction guide and
+  we now produce a diagnostic. Fixes:
+  (`65522 <https://github.com/llvm/llvm-project/issues/65522>`_)
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cor3ntin wrote:

```suggestion
  (`#65522 <https://github.com/llvm/llvm-project/issues/65522>`_)
```

https://github.com/llvm/llvm-project/pull/67373