[clang] [clang] Implement P2582R1: CTAD from inherited constructors (PR #98788)

[via cfe-commits]

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@@ -1398,5 +1807,30 @@ void Sema::DeclareImplicitDeductionGuides(TemplateDecl *Template,
           ->getTemplatedDecl())
       ->setDeductionCandidateKind(DeductionCandidate::Copy);
 
+  CXXRecordDecl *TemplatedDecl = Pattern->getTemplatedDecl();
+  if (getLangOpts().CPlusPlus23 && TemplatedDecl->hasDefinition()) {
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cor3ntin wrote:

Is that something we should support in C++20 as an extension?

https://github.com/llvm/llvm-project/pull/98788