Revert "Reland "[clang][Sema] Use original template pattern when declaring implicit deduction guides for nested template classes" (#69676)"

This reverts commit f418319.

Failing test case: #69676 (comment)

Author: antangelo

clang/docs/ReleaseNotes.rst

@@ -665,11 +665,6 @@ Bug Fixes to C++ Support
   declaration definition. Fixes:
   (`#61763 <https://github.com/llvm/llvm-project/issues/61763>`_)
 
-- Fix a bug where implicit deduction guides are not correctly generated for nested template
-  classes. Fixes:
-  (`#46200 <https://github.com/llvm/llvm-project/issues/46200>`_)
-  (`#57812 <https://github.com/llvm/llvm-project/issues/57812>`_)
-
 - Diagnose use of a variable-length array in a coroutine. The design of
   coroutines is such that it is not possible to support VLA use. Fixes:
   (`#65858 <https://github.com/llvm/llvm-project/issues/65858>`_)

clang/lib/Sema/SemaTemplate.cpp

@@ -2253,7 +2253,6 @@ struct ConvertConstructorToDeductionGuideTransform {
 
   Sema &SemaRef;
   ClassTemplateDecl *Template;
-  ClassTemplateDecl *NestedPattern = nullptr;
 
   DeclContext *DC = Template->getDeclContext();
   CXXRecordDecl *Primary = Template->getTemplatedDecl();
@@ -2333,9 +2332,6 @@ struct ConvertConstructorToDeductionGuideTransform {
       Args.addOuterRetainedLevel();
     }
 
-    if (NestedPattern)
-      Args.addOuterRetainedLevels(NestedPattern->getTemplateDepth());
-
     FunctionProtoTypeLoc FPTL = CD->getTypeSourceInfo()->getTypeLoc()
                                    .getAsAdjusted<FunctionProtoTypeLoc>();
     assert(FPTL && "no prototype for constructor declaration");
@@ -2445,17 +2441,10 @@ struct ConvertConstructorToDeductionGuideTransform {
     SmallVector<QualType, 4> ParamTypes;
     const FunctionProtoType *T = TL.getTypePtr();
 
-    MultiLevelTemplateArgumentList OuterInstantiationArgs;
-    if (NestedPattern)
-      OuterInstantiationArgs = SemaRef.getTemplateInstantiationArgs(Template);
-
     //    -- The types of the function parameters are those of the constructor.
     for (auto *OldParam : TL.getParams()) {
       ParmVarDecl *NewParam =
           transformFunctionTypeParam(OldParam, Args, MaterializedTypedefs);
-      if (NestedPattern && NewParam)
-        NewParam = transformFunctionTypeParam(NewParam, OuterInstantiationArgs,
-                                              MaterializedTypedefs);
       if (!NewParam)
         return QualType();
       ParamTypes.push_back(NewParam->getType());
@@ -2661,24 +2650,13 @@ void Sema::DeclareImplicitDeductionGuides(TemplateDecl *Template,
   if (BuildingDeductionGuides.isInvalid())
     return;
 
-  // If the template is nested, then we need to use the original
-  // pattern to iterate over the constructors.
-  ClassTemplateDecl *Pattern = Transform.Template;
-  while (Pattern->getInstantiatedFromMemberTemplate()) {
-    if (Pattern->isMemberSpecialization())
-      break;
-    Pattern = Pattern->getInstantiatedFromMemberTemplate();
-    Transform.NestedPattern = Pattern;
-  }
-
   // Convert declared constructors into deduction guide templates.
   // FIXME: Skip constructors for which deduction must necessarily fail (those
   // for which some class template parameter without a default argument never
   // appears in a deduced context).
-  ContextRAII SavedContext(*this, Pattern->getTemplatedDecl());
   llvm::SmallPtrSet<NamedDecl *, 8> ProcessedCtors;
   bool AddedAny = false;
-  for (NamedDecl *D : LookupConstructors(Pattern->getTemplatedDecl())) {
+  for (NamedDecl *D : LookupConstructors(Transform.Primary)) {
     D = D->getUnderlyingDecl();
     if (D->isInvalidDecl() || D->isImplicit())
       continue;
@@ -2724,8 +2702,6 @@ void Sema::DeclareImplicitDeductionGuides(TemplateDecl *Template,
           Transform.buildSimpleDeductionGuide(Transform.DeducedType))
           ->getTemplatedDecl())
       ->setDeductionCandidateKind(DeductionCandidate::Copy);
-
-  SavedContext.pop();
 }
 
 /// Diagnose the presence of a default template argument on a

clang/test/SemaTemplate/nested-deduction-guides.cpp

@@ -4,15 +4,10 @@
 template<typename T> struct A {
   template<typename U> struct B {
     B(...);
-    B(const B &) = default;
   };
   template<typename U> B(U) -> B<U>;
 };
 A<void>::B b = 123;
-A<void>::B copy = b;
 
 using T = decltype(b);
 using T = A<void>::B<int>;
-
-using Copy = decltype(copy);
-using Copy = A<void>::B<int>;