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

[Matheus Izvekov via llvm-branch-commits]

================
@@ -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;
+  case TemplateDeductionResult::NonDeducedMismatch:
+    Diag(AArg->getLocation(), diag::err_non_deduced_mismatch)
+        << Info.FirstArg << Info.SecondArg;
+    return false;
+  case TemplateDeductionResult::Inconsistent:
+    Diag(getAsNamedDecl(Info.Param)->getLocation(),
+         diag::err_inconsistent_deduction)
+        << Info.FirstArg << Info.SecondArg;
+    return false;
+  case TemplateDeductionResult::AlreadyDiagnosed:
     return false;
 
+  // None of these should happen for a plain deduction.
+  case TemplateDeductionResult::Invalid:
+  case TemplateDeductionResult::InstantiationDepth:
+  case TemplateDeductionResult::Incomplete:
+  case TemplateDeductionResult::IncompletePack:
+  case TemplateDeductionResult::Underqualified:
+  case TemplateDeductionResult::SubstitutionFailure:
+  case TemplateDeductionResult::DeducedMismatch:
+  case TemplateDeductionResult::DeducedMismatchNested:
+  case TemplateDeductionResult::TooManyArguments:
+  case TemplateDeductionResult::TooFewArguments:
+  case TemplateDeductionResult::InvalidExplicitArguments:
+  case TemplateDeductionResult::NonDependentConversionFailure:
+  case TemplateDeductionResult::ConstraintsNotSatisfied:
+  case TemplateDeductionResult::CUDATargetMismatch:
----------------
mizvekov wrote:

I think the sheer amount of enumerators here is an indication of this growing without careful design.

We could probably refactor this and collapse a lot of these cases into fewer cases, and such.

I think it would also be helpful to not have one TemplateDeductionResult to rule them all, when some times you are dealing with the subset of the problem and a lot of these cases don't apply at all.

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