[clang] [clang] Find conversion function templates for in-class specializations (PR #218316)

[Corentin Jabot via cfe-commits]

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@@ -533,6 +528,8 @@ features cannot lower the translation-unit ABI level;
   parameter that follows a parameter pack (e.g.
   `template <typename... T> S::S(T..., int = 10) {}`).  (#GH216211)
 
+- Allow redeclaration lookup to consider conversion function templates allowing Clang to match an in-class specialization such as `template<> operator int()` against a prior conversion function template `template<class T> operator T()`.
+
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cor3ntin wrote:

```suggestion
- Allow redeclaration lookup to consider conversion function templates allowing Clang to match an in-class specialization such as `template<> operator int()` against a prior conversion function template `template<class T> operator T()`. (#GH218261)

```

https://github.com/llvm/llvm-project/pull/218316