Let ... expand NTTP constraints

Author: zyn0217

clang/lib/AST/ASTContext.cpp

@@ -6376,7 +6376,7 @@ ASTContext::getAutoType(QualType DeducedType, AutoTypeKeyword Keyword,
 }
 
 QualType ASTContext::getUnconstrainedType(QualType T) const {
-  QualType CanonT = T.getCanonicalType();
+  QualType CanonT = T.getNonPackExpansionType().getCanonicalType();
 
   // Remove a type-constraint from a top-level auto or decltype(auto).
   if (auto *AT = CanonT->getAs<AutoType>()) {

clang/lib/Sema/SemaTemplate.cpp

@@ -1228,7 +1228,7 @@ bool Sema::AttachTypeConstraint(AutoTypeLoc TL,
                                 NonTypeTemplateParmDecl *NewConstrainedParm,
                                 NonTypeTemplateParmDecl *OrigConstrainedParm,
                                 SourceLocation EllipsisLoc) {
-  if (NewConstrainedParm->getType() != TL.getType() ||
+  if (NewConstrainedParm->getType().getNonPackExpansionType() != TL.getType() ||
       TL.getAutoKeyword() != AutoTypeKeyword::Auto) {
     Diag(NewConstrainedParm->getTypeSourceInfo()->getTypeLoc().getBeginLoc(),
          diag::err_unsupported_placeholder_constraint)
@@ -1530,17 +1530,9 @@ NamedDecl *Sema::ActOnNonTypeTemplateParameter(Scope *S, Declarator &D,
   Param->setAccess(AS_public);
 
   if (AutoTypeLoc TL = TInfo->getTypeLoc().getContainedAutoTypeLoc())
-    if (TL.isConstrained()) {
-      if (const ASTTemplateArgumentListInfo *ArgumentList =
-              TL.getConceptReference()->getTemplateArgsAsWritten())
-        for (const TemplateArgumentLoc &Loc : ArgumentList->arguments()) {
-          Invalid |= DiagnoseUnexpandedParameterPack(
-              Loc, UnexpandedParameterPackContext::UPPC_TypeConstraint);
-        }
-      if (!Invalid &&
-          AttachTypeConstraint(TL, Param, Param, D.getEllipsisLoc()))
+    if (TL.isConstrained())
+      if (AttachTypeConstraint(TL, Param, Param, D.getEllipsisLoc()))
         Invalid = true;
-    }
 
   if (Invalid)
     Param->setInvalidDecl();

clang/lib/Sema/SemaTemplateDeduction.cpp

@@ -857,7 +857,8 @@ class PackDeductionScope {
       if (auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(
               TemplateParams->getParam(Index))) {
         if (!NTTP->isExpandedParameterPack())
-          if (auto *Expansion = dyn_cast<PackExpansionType>(NTTP->getType()))
+          if (auto *Expansion = dyn_cast<PackExpansionType>(
+                  S.Context.getUnconstrainedType(NTTP->getType())))
             ExtraDeductions.push_back(Expansion->getPattern());
       }
       // FIXME: Also collect the unexpanded packs in any type and template