[llvm-branch-commits] [clang] [clang] Finish implementation of P0522 (PR #96023)

[Matheus Izvekov via llvm-branch-commits]

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@@ -6369,27 +6451,88 @@ bool Sema::isTemplateTemplateParameterAtLeastAsSpecializedAs(
   //   be inverted between Ps and As. On non-deduced context, matching needs to
   //   happen both ways, according to [temp.arg.template]p3, but this is
   //   currently implemented as a special case elsewhere.
-  if (::DeduceTemplateArguments(*this, A, AArgs, PArgs, Info, Deduced,
-                                /*NumberOfArgumentsMustMatch=*/false,
-                                IsDeduced ? PackFold::ArgumentToParameter
-                                          : PackFold::ParameterToArgument) !=
-      TemplateDeductionResult::Success)
+  switch (TemplateDeductionResult Result = ::DeduceTemplateArguments(
+              *this, A, AArgs, PArgs, Info, Deduced,
+              /*NumberOfArgumentsMustMatch=*/false,
+              IsDeduced ? PackFold::ArgumentToParameter : PackFold::Both)) {
+  case clang::TemplateDeductionResult::Success:
+    break;
+
+  case TemplateDeductionResult::MiscellaneousDeductionFailure:
+    Diag(AArg->getLocation(), diag::err_template_param_list_different_arity)
+        << (A->size() > P->size()) << /*isTemplateTemplateParameter=*/true
+        << SourceRange(A->getTemplateLoc(), P->getRAngleLoc());
+    return false;
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mizvekov wrote:

The right thing would be to introduce a new enumerator, but I think this patch keeps the status quo while being large enough already.

https://github.com/llvm/llvm-project/pull/96023