[clang] [Clang] Implement CWG2900 (PR #224291)

[Younan Zhang via cfe-commits]

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@@ -234,31 +234,39 @@ class NonTypeOrVarTemplateParmDecl {
   const NamedDecl *Template;
 };
 
-/// If the given expression is of a form that permits the deduction
-/// of a non-type template parameter, return the declaration of that
-/// non-type template parameter.
+/// If the given expression is of a form that names a non-type template
+/// parameter, return the declaration of that parameter. A null \p Depth
+/// accepts a parameter at any depth.
 static NonTypeOrVarTemplateParmDecl
-getDeducedNTTParameterFromExpr(const Expr *E, unsigned Depth) {
+getNTTParameterFromExpr(const Expr *E, UnsignedOrNone Depth) {
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zyn0217 wrote:

There's only 1 client of getTypeOfConstantTemplateParameter, so maybe we want to promote this function rather than a new function in Sema?

https://github.com/llvm/llvm-project/pull/224291