[clang] [clang] fix matching constrained out-of-line definitions of class specialization member function templates (PR #192806)

[Matheus Izvekov via cfe-commits]

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@@ -346,58 +346,56 @@ Response HandleFunction(Sema &SemaRef, const FunctionDecl *Function,
 Response HandleFunctionTemplateDecl(Sema &SemaRef,
                                     const FunctionTemplateDecl *FTD,
                                     MultiLevelTemplateArgumentList &Result) {
-  if (!isa<ClassTemplateSpecializationDecl>(FTD->getDeclContext())) {
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mizvekov wrote:

Yeah look for the changes on `clang/lib/Sema/SemaTemplateDeductionGuide.cpp`, the pre-existing implementation there was relying on this bug.

https://github.com/llvm/llvm-project/pull/192806