Revert "[Clang][Sema] Retain the expanding index for unevaluated type constraints (#109518)"

This reverts commit 50e5411.

Author: mizvekov

clang/include/clang/Sema/Sema.h

@@ -11350,7 +11350,6 @@ class Sema final : public SemaBase {
                             ConceptDecl *NamedConcept, NamedDecl *FoundDecl,
                             const TemplateArgumentListInfo *TemplateArgs,
                             TemplateTypeParmDecl *ConstrainedParameter,
-                            QualType ConstrainedType,
                             SourceLocation EllipsisLoc);
 
   bool AttachTypeConstraint(AutoTypeLoc TL,

clang/lib/Sema/SemaTemplate.cpp

@@ -1133,8 +1133,7 @@ bool Sema::BuildTypeConstraint(const CXXScopeSpec &SS,
       SS.isSet() ? SS.getWithLocInContext(Context) : NestedNameSpecifierLoc(),
       ConceptName, CD, /*FoundDecl=*/USD ? cast<NamedDecl>(USD) : CD,
       TypeConstr->LAngleLoc.isValid() ? &TemplateArgs : nullptr,
-      ConstrainedParameter, Context.getTypeDeclType(ConstrainedParameter),
-      EllipsisLoc);
+      ConstrainedParameter, EllipsisLoc);
 }
 
 template <typename ArgumentLocAppender>
@@ -1191,7 +1190,6 @@ bool Sema::AttachTypeConstraint(NestedNameSpecifierLoc NS,
                                 ConceptDecl *NamedConcept, NamedDecl *FoundDecl,
                                 const TemplateArgumentListInfo *TemplateArgs,
                                 TemplateTypeParmDecl *ConstrainedParameter,
-                                QualType ConstrainedType,
                                 SourceLocation EllipsisLoc) {
   // C++2a [temp.param]p4:
   //     [...] If Q is of the form C<A1, ..., An>, then let E' be
@@ -1200,7 +1198,7 @@ bool Sema::AttachTypeConstraint(NestedNameSpecifierLoc NS,
     TemplateArgs ? ASTTemplateArgumentListInfo::Create(Context,
                                                        *TemplateArgs) : nullptr;
 
-  QualType ParamAsArgument = ConstrainedType;
+  QualType ParamAsArgument(ConstrainedParameter->getTypeForDecl(), 0);
 
   ExprResult ImmediatelyDeclaredConstraint = formImmediatelyDeclaredConstraint(
       *this, NS, NameInfo, NamedConcept, FoundDecl,

clang/lib/Sema/SemaTemplateInstantiate.cpp

@@ -1717,21 +1717,6 @@ namespace {
                                            SubstTemplateTypeParmPackTypeLoc TL,
                                            bool SuppressObjCLifetime);
 
-    QualType
-    TransformSubstTemplateTypeParmType(TypeLocBuilder &TLB,
-                                       SubstTemplateTypeParmTypeLoc TL) {
-      if (SemaRef.CodeSynthesisContexts.back().Kind !=
-          Sema::CodeSynthesisContext::ConstraintSubstitution)
-        return inherited::TransformSubstTemplateTypeParmType(TLB, TL);
-
-      auto PackIndex = TL.getTypePtr()->getPackIndex();
-      std::optional<Sema::ArgumentPackSubstitutionIndexRAII> SubstIndex;
-      if (SemaRef.ArgumentPackSubstitutionIndex == -1 && PackIndex)
-        SubstIndex.emplace(SemaRef, *PackIndex);
-
-      return inherited::TransformSubstTemplateTypeParmType(TLB, TL);
-    }
-
     CXXRecordDecl::LambdaDependencyKind
     ComputeLambdaDependency(LambdaScopeInfo *LSI) {
       if (auto TypeAlias =
@@ -3166,58 +3151,6 @@ namespace {
 
 } // namespace
 
-namespace {
-
-struct ExpandPackedTypeConstraints
-    : TreeTransform<ExpandPackedTypeConstraints> {
-
-  using inherited = TreeTransform<ExpandPackedTypeConstraints>;
-
-  ExpandPackedTypeConstraints(Sema &SemaRef) : inherited(SemaRef) {}
-
-  using inherited::TransformTemplateTypeParmType;
-
-  QualType TransformTemplateTypeParmType(TypeLocBuilder &TLB,
-                                         TemplateTypeParmTypeLoc TL, bool) {
-    const TemplateTypeParmType *T = TL.getTypePtr();
-    if (!T->isParameterPack()) {
-      TemplateTypeParmTypeLoc NewTL =
-          TLB.push<TemplateTypeParmTypeLoc>(TL.getType());
-      NewTL.setNameLoc(TL.getNameLoc());
-      return TL.getType();
-    }
-
-    assert(SemaRef.ArgumentPackSubstitutionIndex != -1);
-
-    QualType Result = SemaRef.Context.getSubstTemplateTypeParmType(
-        TL.getType(), T->getDecl(), T->getIndex(),
-        SemaRef.ArgumentPackSubstitutionIndex);
-    SubstTemplateTypeParmTypeLoc NewTL =
-        TLB.push<SubstTemplateTypeParmTypeLoc>(Result);
-    NewTL.setNameLoc(TL.getNameLoc());
-    return Result;
-  }
-
-  QualType TransformSubstTemplateTypeParmType(TypeLocBuilder &TLB,
-                                              SubstTemplateTypeParmTypeLoc TL) {
-    const SubstTemplateTypeParmType *T = TL.getTypePtr();
-    if (T->getPackIndex()) {
-      SubstTemplateTypeParmTypeLoc TypeLoc =
-          TLB.push<SubstTemplateTypeParmTypeLoc>(TL.getType());
-      TypeLoc.setNameLoc(TL.getNameLoc());
-      return TypeLoc.getType();
-    }
-    return inherited::TransformSubstTemplateTypeParmType(TLB, TL);
-  }
-
-  bool SubstTemplateArguments(ArrayRef<TemplateArgumentLoc> Args,
-                              TemplateArgumentListInfo &Out) {
-    return inherited::TransformTemplateArguments(Args.begin(), Args.end(), Out);
-  }
-};
-
-} // namespace
-
 bool Sema::SubstTypeConstraint(
     TemplateTypeParmDecl *Inst, const TypeConstraint *TC,
     const MultiLevelTemplateArgumentList &TemplateArgs,
@@ -3226,62 +3159,9 @@ bool Sema::SubstTypeConstraint(
       TC->getTemplateArgsAsWritten();
 
   if (!EvaluateConstraints) {
-    bool ShouldExpandExplicitTemplateArgs =
-        TemplArgInfo && ArgumentPackSubstitutionIndex != -1 &&
-        llvm::any_of(TemplArgInfo->arguments(), [](auto &Arg) {
-          return Arg.getArgument().containsUnexpandedParameterPack();
-        });
-
-    // We want to transform the packs into Subst* nodes for type constraints
-    // inside a pack expansion. For example,
-    //
-    //  template <class... Ts> void foo() {
-    //    bar([](C<Ts> auto value) {}...);
-    //  }
-    //
-    // As we expand Ts in the process of instantiating foo(), and retain
-    // the original template depths of Ts until the constraint evaluation, we
-    // would otherwise have no chance to expand Ts by the time of evaluating
-    // C<auto, Ts>.
-    //
-    // So we form a Subst* node for Ts along with a proper substitution index
-    // here, and substitute the node with a complete MLTAL later in evaluation.
-    if (ShouldExpandExplicitTemplateArgs) {
-      TemplateArgumentListInfo InstArgs;
-      InstArgs.setLAngleLoc(TemplArgInfo->LAngleLoc);
-      InstArgs.setRAngleLoc(TemplArgInfo->RAngleLoc);
-      if (ExpandPackedTypeConstraints(*this).SubstTemplateArguments(
-              TemplArgInfo->arguments(), InstArgs))
-        return true;
-
-      // The type of the original parameter.
-      auto *ConstraintExpr = TC->getImmediatelyDeclaredConstraint();
-      QualType ConstrainedType;
-
-      if (auto *FE = dyn_cast<CXXFoldExpr>(ConstraintExpr)) {
-        assert(FE->getLHS());
-        ConstraintExpr = FE->getLHS();
-      }
-      auto *CSE = cast<ConceptSpecializationExpr>(ConstraintExpr);
-      assert(!CSE->getTemplateArguments().empty() &&
-             "Empty template arguments?");
-      ConstrainedType = CSE->getTemplateArguments()[0].getAsType();
-      assert(!ConstrainedType.isNull() &&
-             "Failed to extract the original ConstrainedType?");
-
-      return AttachTypeConstraint(
-          TC->getNestedNameSpecifierLoc(), TC->getConceptNameInfo(),
-          TC->getNamedConcept(),
-          /*FoundDecl=*/TC->getConceptReference()->getFoundDecl(), &InstArgs,
-          Inst, ConstrainedType,
-          Inst->isParameterPack()
-              ? cast<CXXFoldExpr>(TC->getImmediatelyDeclaredConstraint())
-                    ->getEllipsisLoc()
-              : SourceLocation());
-    }
-    Inst->setTypeConstraint(TC->getConceptReference(),
-                            TC->getImmediatelyDeclaredConstraint());
-    return false;
+      Inst->setTypeConstraint(TC->getConceptReference(),
+                              TC->getImmediatelyDeclaredConstraint());
+      return false;
   }
 
   TemplateArgumentListInfo InstArgs;
@@ -3297,7 +3177,6 @@ bool Sema::SubstTypeConstraint(
       TC->getNestedNameSpecifierLoc(), TC->getConceptNameInfo(),
       TC->getNamedConcept(),
       /*FoundDecl=*/TC->getConceptReference()->getFoundDecl(), &InstArgs, Inst,
-      Context.getTypeDeclType(Inst),
       Inst->isParameterPack()
           ? cast<CXXFoldExpr>(TC->getImmediatelyDeclaredConstraint())
                 ->getEllipsisLoc()

clang/lib/Sema/SemaType.cpp

@@ -3054,9 +3054,7 @@ InventTemplateParameter(TypeProcessingState &state, QualType T,
             AutoLoc.getNestedNameSpecifierLoc(), AutoLoc.getConceptNameInfo(),
             AutoLoc.getNamedConcept(), /*FoundDecl=*/AutoLoc.getFoundDecl(),
             AutoLoc.hasExplicitTemplateArgs() ? &TAL : nullptr,
-            InventedTemplateParam,
-            S.Context.getTypeDeclType(InventedTemplateParam),
-            D.getEllipsisLoc());
+            InventedTemplateParam, D.getEllipsisLoc());
       }
     } else {
       // The 'auto' appears in the decl-specifiers; we've not finished forming
@@ -3093,9 +3091,7 @@ InventTemplateParameter(TypeProcessingState &state, QualType T,
             /*FoundDecl=*/
             USD ? cast<NamedDecl>(USD) : CD,
             TemplateId->LAngleLoc.isValid() ? &TemplateArgsInfo : nullptr,
-            InventedTemplateParam,
-            S.Context.getTypeDeclType(InventedTemplateParam),
-            D.getEllipsisLoc());
+            InventedTemplateParam, D.getEllipsisLoc());
       }
     }
   }