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

[Haojian Wu via cfe-commits]

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@@ -944,12 +950,63 @@ getRHSTemplateDeclAndArgs(Sema &SemaRef, TypeAliasTemplateDecl *AliasTemplate) {
   return {Template, AliasRhsTemplateArgs};
 }
 
+// Build the type for a deduction guide generated from an inherited constructor
+// [over.match.class.deduct]p1.10:
+// ... the set contains the guides of A with the return type R
+// of each guide replaced with `typename CC<R>::type` ...
+std::pair<TypeSourceInfo *, QualType>
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hokein wrote:

nit: we can just return a `TypeSourceInfo`, the QualType is the return type of the `FunctionProtoTyp` which can be retrieved from the `TypeSourceInfo`.

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