diff --git a/clang/include/clang/AST/ASTConcept.h b/clang/include/clang/AST/ASTConcept.h
index ace4de0d627726..ef560886924b3a 100644
--- a/clang/include/clang/AST/ASTConcept.h
+++ b/clang/include/clang/AST/ASTConcept.h
@@ -281,54 +281,6 @@ class TypeConstraint {
 
 };
 
-class PartiallyAppliedConcept : public ConceptReference,
-                                public llvm::FoldingSetNode {
-
-  SourceLocation ConceptKWLoc;
-  PartiallyAppliedConcept(NestedNameSpecifierLoc NNS,
-                          DeclarationNameInfo ConceptNameInfo,
-                          SourceLocation ConceptKWLoc, NamedDecl *FoundDecl,
-                          TemplateDecl *NamedConcept,
-                          const ASTTemplateArgumentListInfo *ArgsAsWritten)
-      : ConceptReference(NNS, /*TemplateKWLoc=*/SourceLocation(),
-                         ConceptNameInfo, FoundDecl, NamedConcept,
-                         ArgsAsWritten),
-        ConceptKWLoc(ConceptKWLoc) {}
-
-public:
-  static PartiallyAppliedConcept *
-  Create(const ASTContext &C, NestedNameSpecifierLoc NNS,
-         DeclarationNameInfo ConceptNameInfo, SourceLocation ConceptKWLoc,
-         NamedDecl *FoundDecl, TemplateDecl *NamedConcept,
-         const TemplateArgumentListInfo &TemplateArgs);
-
-  TemplateArgumentDependence getDependence() const;
-
-  bool isDependent() const {
-    return getDependence() & TemplateArgumentDependence::Dependent;
-  }
-
-  bool isInstantiationDependent() const {
-    return getDependence() & TemplateArgumentDependence::Instantiation;
-  }
-
-  void Profile(llvm::FoldingSetNodeID &ID, const ASTContext &C) const {
-    Profile(ID, C, getNamedConcept(), getTemplateArgsAsWritten());
-  }
-
-  static void Profile(llvm::FoldingSetNodeID &ID, const ASTContext &C,
-                      const TemplateDecl *NamedConcept,
-                      const ASTTemplateArgumentListInfo *ArgsAsWritten);
-
-  SourceLocation getConceptKWLoc() const { return ConceptKWLoc; }
-
-  SourceRange getSourceRange() const {
-    return {ConceptKWLoc, ArgsAsWritten->getRAngleLoc()};
-  }
-
-  friend const StreamingDiagnostic &operator<<(const StreamingDiagnostic &DB,
-                                               PartiallyAppliedConcept &C);
-};
 
 } // clang
 
diff --git a/clang/include/clang/AST/ASTContext.h b/clang/include/clang/AST/ASTContext.h
index 272a712fe170c4..ae6430cb932e1b 100644
--- a/clang/include/clang/AST/ASTContext.h
+++ b/clang/include/clang/AST/ASTContext.h
@@ -97,7 +97,6 @@ class ObjCTypeParamDecl;
 class OMPTraitInfo;
 class ParentMapContext;
 struct ParsedTargetAttr;
-class PartiallyAppliedConcept;
 class Preprocessor;
 class ProfileList;
 class StoredDeclsMap;
diff --git a/clang/include/clang/AST/RecursiveASTVisitor.h b/clang/include/clang/AST/RecursiveASTVisitor.h
index c0dd6783336627..1e15f5e372f0ce 100644
--- a/clang/include/clang/AST/RecursiveASTVisitor.h
+++ b/clang/include/clang/AST/RecursiveASTVisitor.h
@@ -904,14 +904,6 @@ bool RecursiveASTVisitor<Derived>::TraverseTemplateArgument(
   case TemplateArgument::Pack:
     return getDerived().TraverseTemplateArguments(Arg.pack_elements());
 
-  case TemplateArgument::Concept: {
-    PartiallyAppliedConcept *C = Arg.getAsPartiallyAppliedConcept();
-    TRY_TO(getDerived().TraverseDecl(C->getNamedConcept()));
-    for (const TemplateArgumentLoc &Arg :
-         C->getTemplateArgsAsWritten()->arguments())
-      TRY_TO(TraverseTemplateArgument(Arg.getArgument()));
-    return true;
-  }
   case TemplateArgument::Universal:
   case TemplateArgument::UniversalExpansion: {
     UniversalTemplateParameterName *UTPN =
@@ -965,14 +957,6 @@ bool RecursiveASTVisitor<Derived>::TraverseTemplateArgumentLoc(
   case TemplateArgument::Pack:
     return getDerived().TraverseTemplateArguments(Arg.pack_elements());
 
-  case TemplateArgument::Concept: {
-    PartiallyAppliedConcept *C = Arg.getAsPartiallyAppliedConcept();
-    TRY_TO(getDerived().TraverseDecl(C->getNamedConcept()));
-    for (const TemplateArgumentLoc &Arg :
-         C->getTemplateArgsAsWritten()->arguments())
-      TRY_TO(TraverseTemplateArgument(Arg.getArgument()));
-    return true;
-  }
   }
 
   return true;
diff --git a/clang/include/clang/AST/TemplateArgumentVisitor.h b/clang/include/clang/AST/TemplateArgumentVisitor.h
index 2e6d3cf9daf0e9..91b7ed1b389dc5 100644
--- a/clang/include/clang/AST/TemplateArgumentVisitor.h
+++ b/clang/include/clang/AST/TemplateArgumentVisitor.h
@@ -42,7 +42,6 @@ class Base {
       DISPATCH(TemplateExpansion);
       DISPATCH(Expression);
       DISPATCH(Pack);
-      DISPATCH(Concept);
       DISPATCH(Universal);
       DISPATCH(UniversalExpansion);
     }
@@ -68,7 +67,6 @@ class Base {
   VISIT_METHOD(TemplateExpansion);
   VISIT_METHOD(Expression);
   VISIT_METHOD(Pack);
-  VISIT_METHOD(Concept);
   VISIT_METHOD(Universal);
   VISIT_METHOD(UniversalExpansion);
 
diff --git a/clang/include/clang/AST/TemplateBase.h b/clang/include/clang/AST/TemplateBase.h
index f4aded4957fe05..03d3cfb5f586aa 100644
--- a/clang/include/clang/AST/TemplateBase.h
+++ b/clang/include/clang/AST/TemplateBase.h
@@ -58,7 +58,6 @@ class Expr;
 struct PrintingPolicy;
 class TypeSourceInfo;
 class ValueDecl;
-class PartiallyAppliedConcept;
 
 /// Represents a template argument.
 class TemplateArgument {
@@ -109,9 +108,6 @@ class TemplateArgument {
     /// in the Args struct.
     Pack,
 
-    // A concept with argument
-    Concept,
-
     /// The template argument refers to a universal template parameter
     Universal,
 
@@ -183,12 +179,6 @@ class TemplateArgument {
     uintptr_t V;
   };
 
-  struct ConceptData {
-    unsigned Kind : 31;
-    unsigned IsDefaulted : 1;
-    PartiallyAppliedConcept *C;
-  };
-
   struct UniversalTpl {
     unsigned Kind : 31;
     unsigned IsDefaulted : 1;
@@ -203,7 +193,6 @@ class TemplateArgument {
     struct A Args;
     struct TA TemplateArg;
     struct TV TypeOrValue;
-    struct ConceptData PartialConcept;
     struct UniversalTpl UniversalArg;
   };
 
@@ -311,13 +300,6 @@ class TemplateArgument {
     this->Args.NumArgs = Args.size();
   }
 
-  explicit TemplateArgument(PartiallyAppliedConcept *C,
-                            bool IsDefaulted = false) {
-    PartialConcept.Kind = Concept;
-    PartialConcept.IsDefaulted = IsDefaulted;
-    PartialConcept.C = C;
-  }
-
   explicit TemplateArgument(UniversalTemplateParameterName *U,
                             bool IsDefaulted = false) {
     UniversalArg.Kind = Universal;
@@ -411,11 +393,6 @@ class TemplateArgument {
     return TemplateName::getFromVoidPointer(TemplateArg.Name);
   }
 
-  PartiallyAppliedConcept *getAsPartiallyAppliedConcept() const {
-    assert((getKind() == Concept) && "Unexpected kind");
-    return PartialConcept.C;
-  }
-
   UniversalTemplateParameterName *getAsUniversalTemplateParameterName() const {
     assert((getKind() == Universal) && "Unexpected kind");
     return UniversalArg.D;
@@ -647,8 +624,7 @@ class TemplateArgumentLoc {
       : Argument(Argument),
         LocInfo(Ctx, QualifierLoc, TemplateNameLoc, EllipsisLoc) {
     assert(Argument.getKind() == TemplateArgument::Template ||
-           Argument.getKind() == TemplateArgument::TemplateExpansion ||
-           Argument.getKind() == TemplateArgument::Concept);
+           Argument.getKind() == TemplateArgument::TemplateExpansion);
   }
 
   TemplateArgumentLoc(ASTContext &Ctx, const TemplateArgument &Argument,
@@ -662,8 +638,7 @@ class TemplateArgumentLoc {
   /// - Fetches the primary location of the argument.
   SourceLocation getLocation() const {
     if (Argument.getKind() == TemplateArgument::Template ||
-        Argument.getKind() == TemplateArgument::TemplateExpansion ||
-        Argument.getKind() == TemplateArgument::Concept)
+        Argument.getKind() == TemplateArgument::TemplateExpansion)
       return getTemplateNameLoc();
 
     return getSourceRange().getBegin();
@@ -709,16 +684,14 @@ class TemplateArgumentLoc {
 
   NestedNameSpecifierLoc getTemplateQualifierLoc() const {
     if (Argument.getKind() != TemplateArgument::Template &&
-        Argument.getKind() != TemplateArgument::TemplateExpansion &&
-        Argument.getKind() != TemplateArgument::Concept)
+        Argument.getKind() != TemplateArgument::TemplateExpansion)
       return NestedNameSpecifierLoc();
     return LocInfo.getTemplateQualifierLoc();
   }
 
   SourceLocation getTemplateNameLoc() const {
     if (Argument.getKind() != TemplateArgument::Template &&
-        Argument.getKind() != TemplateArgument::TemplateExpansion &&
-        Argument.getKind() != TemplateArgument::Concept)
+        Argument.getKind() != TemplateArgument::TemplateExpansion)
       return SourceLocation();
     return LocInfo.getTemplateNameLoc();
   }
diff --git a/clang/include/clang/AST/TypeProperties.td b/clang/include/clang/AST/TypeProperties.td
index 74d69045aa2f55..1a89dfc67bc9b4 100644
--- a/clang/include/clang/AST/TypeProperties.td
+++ b/clang/include/clang/AST/TypeProperties.td
@@ -508,7 +508,7 @@ let Class = AutoType in {
   }
   def : Property<"typeConstraintConcept", Optional<TemplateDeclRef>> {
     let Read = [{ makeOptionalFromPointer(
-        const_cast<const TemplateDecl*>(node->getTypeConstraintConcept())) }];
+        node->getTypeConstraintConcept()) }];
   }
   def : Property<"typeConstraintArguments", Array<TemplateArgument>> {
     let Read = [{ node->getTypeConstraintArguments() }];
diff --git a/clang/include/clang/Parse/Parser.h b/clang/include/clang/Parse/Parser.h
index 4bc36c30d94ea1..9bd4376b5005c8 100644
--- a/clang/include/clang/Parse/Parser.h
+++ b/clang/include/clang/Parse/Parser.h
@@ -3865,7 +3865,6 @@ class Parser : public CodeCompletionHandler {
                                 bool IsClassName = false);
   bool ParseTemplateArgumentList(TemplateArgList &TemplateArgs,
                                  TemplateTy Template, SourceLocation OpenLoc);
-  ParsedTemplateArgument ParsePartiallyAppliedConceptTemplateArgument();
   ParsedTemplateArgument ParseTemplateTemplateArgument();
   ParsedTemplateArgument ParseUniversalTemplateParamNameArgument();
   ParsedTemplateArgument ParseTemplateArgument();
diff --git a/clang/include/clang/Sema/ParsedTemplate.h b/clang/include/clang/Sema/ParsedTemplate.h
index 80cd101b3db1d2..c9046561c73547 100644
--- a/clang/include/clang/Sema/ParsedTemplate.h
+++ b/clang/include/clang/Sema/ParsedTemplate.h
@@ -26,7 +26,6 @@
 #include <new>
 
 namespace clang {
-class PartiallyAppliedConcept;
 
 /// Represents the parsed form of a C++ template argument.
 class ParsedTemplateArgument {
@@ -39,8 +38,6 @@ class ParsedTemplateArgument {
     NonType,
     /// A template template argument, stored as a template name.
     Template,
-    /// A partially applied concept
-    PartiallyAppliedConcept,
     /// The name of a Universal Template Parameter
     Universal
   };
@@ -71,11 +68,6 @@ class ParsedTemplateArgument {
       : Kind(ParsedTemplateArgument::Template), Arg(Template.getAsOpaquePtr()),
         SS(SS), Loc(TemplateLoc) {}
 
-  ParsedTemplateArgument(class PartiallyAppliedConcept *Concept,
-                         SourceLocation TemplateLoc)
-      : Kind(ParsedTemplateArgument::PartiallyAppliedConcept), Arg(Concept),
-        Loc(TemplateLoc) {}
-
   ParsedTemplateArgument(UniversalTemplateParamNameTy ParamName,
                          SourceLocation Loc)
       : Kind(ParsedTemplateArgument::Universal),
@@ -105,11 +97,6 @@ class ParsedTemplateArgument {
     return ParsedTemplateTy::getFromOpaquePtr(Arg);
   }
 
-  class PartiallyAppliedConcept *getAsConcept() const {
-    assert(Kind == PartiallyAppliedConcept && "Not a concept argument");
-    return reinterpret_cast<class PartiallyAppliedConcept *>(Arg);
-  }
-
   UniversalTemplateParamNameTy getAsUniversalTemplateParamName() const {
     assert(Kind == Universal &&
            "Not a reference to a universal template parameter");
@@ -122,7 +109,7 @@ class ParsedTemplateArgument {
   /// Retrieve the nested-name-specifier that precedes the template
   /// name in a template template argument.
   const CXXScopeSpec &getScopeSpec() const {
-    assert((Kind == Template || Kind == PartiallyAppliedConcept) &&
+    assert((Kind == Template) &&
            "Only template template arguments can have a scope specifier");
     return SS;
   }
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 15910e424ad619..615f2eeb916c70 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -974,7 +974,6 @@ class Sema final : public SemaBase {
 
   typedef OpaquePtr<DeclGroupRef> DeclGroupPtrTy;
   typedef OpaquePtr<TemplateName> TemplateTy;
-  typedef OpaquePtr<PartiallyAppliedConcept> ConceptTy;
   typedef OpaquePtr<UniversalTemplateParameterName *>
       UniversalTemplateParamNameTy;
   typedef OpaquePtr<QualType> TypeTy;
@@ -11537,15 +11536,6 @@ class Sema final : public SemaBase {
                                      bool EnteringContext, TemplateTy &Template,
                                      bool AllowInjectedClassName = false);
 
-  PartiallyAppliedConcept *BuildPartiallyAppliedConcept(
-      NestedNameSpecifierLoc NNS, SourceLocation ConceptKWLoc,
-      DeclarationNameInfo ConceptName, TemplateDecl *TD,
-      const TemplateArgumentListInfo &TemplateArgs);
-  PartiallyAppliedConcept *
-  ActOnPartiallyAppliedConcept(Scope *S, CXXScopeSpec &SS,
-                               SourceLocation ConceptKWLoc,
-                               TemplateIdAnnotation *TemplateId);
-
   bool
   ActOnUniversalTemplateParameterName(Scope *S, const UnqualifiedId &Name,
                                       bool EnteringContext,
@@ -11836,10 +11826,6 @@ class Sema final : public SemaBase {
                                    TemplateArgument &SugaredConverted,
                                    TemplateArgument &CanonicalConverted,
                                    CheckTemplateArgumentKind CTAK);
-  bool
-  CheckPartiallyAppliedConceptTemplateArgument(TemplateTemplateParmDecl *Param,
-                                               TemplateParameterList *Params,
-                                               TemplateArgumentLoc &Arg);
 
   /// Check a template argument against its corresponding
   /// template template parameter.
diff --git a/clang/lib/AST/ASTConcept.cpp b/clang/lib/AST/ASTConcept.cpp
index f787a2cec7eb6f..518bf0d7b6a889 100644
--- a/clang/lib/AST/ASTConcept.cpp
+++ b/clang/lib/AST/ASTConcept.cpp
@@ -113,55 +113,3 @@ void ConceptReference::print(llvm::raw_ostream &OS,
     OS << ">";
   }
 }
-
-
-PartiallyAppliedConcept *PartiallyAppliedConcept::Create(
-    const ASTContext &C, NestedNameSpecifierLoc NNS,
-    DeclarationNameInfo ConceptNameInfo, SourceLocation ConceptKWLoc,
-    NamedDecl *FoundDecl, TemplateDecl *NamedConcept,
-    const TemplateArgumentListInfo &TemplateArgs) {
-
-  return new (C) PartiallyAppliedConcept(
-      NNS, ConceptNameInfo, ConceptKWLoc, FoundDecl, NamedConcept,
-      ASTTemplateArgumentListInfo::Create(C, TemplateArgs));
-}
-
-TemplateArgumentDependence PartiallyAppliedConcept::getDependence() const {
-  auto TA = TemplateArgumentDependence::None;
-  if (isa<TemplateTemplateParmDecl>(getNamedConcept())) {
-    TA |= TemplateArgumentDependence::DependentInstantiation;
-  }
-  const auto InterestingDeps = TemplateArgumentDependence::Instantiation |
-                               TemplateArgumentDependence::UnexpandedPack;
-  for (const TemplateArgumentLoc &ArgLoc :
-       getTemplateArgsAsWritten()->arguments()) {
-    TA |= ArgLoc.getArgument().getDependence() & InterestingDeps;
-    if (TA == InterestingDeps)
-      break;
-  }
-  return TA;
-}
-
-void PartiallyAppliedConcept::Profile(
-    llvm::FoldingSetNodeID &ID, const ASTContext &C,
-    const TemplateDecl *NamedConcept,
-    const ASTTemplateArgumentListInfo *ArgsAsWritten) {
-  ID.AddPointer(NamedConcept);
-  ID.AddInteger(ArgsAsWritten->getNumTemplateArgs());
-  for (auto &Arg : ArgsAsWritten->arguments())
-    Arg.getArgument().Profile(ID, C);
-}
-
-const StreamingDiagnostic &clang::operator<<(const StreamingDiagnostic &DB,
-                                             PartiallyAppliedConcept &C) {
-  std::string NameStr;
-  llvm::raw_string_ostream OS(NameStr);
-  LangOptions LO;
-  LO.CPlusPlus = true;
-  LO.Bool = true;
-  OS << '\'';
-  C.print(OS, PrintingPolicy(LO));
-  OS << '\'';
-  OS.flush();
-  return DB << NameStr;
-}
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index ca47d719deac62..56e8ac1db31265 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -7308,10 +7308,6 @@ ASTContext::getCanonicalTemplateArgument(const TemplateArgument &Arg) const {
     case TemplateArgument::Expression:
       return Arg;
 
-    // FIXME corentin: do concept needs to be canonicalized?
-    case TemplateArgument::Concept:
-      return Arg;
-
     case TemplateArgument::Declaration: {
       auto *D = cast<ValueDecl>(Arg.getAsDecl()->getCanonicalDecl());
       return TemplateArgument(D, getCanonicalType(Arg.getParamTypeForDecl()),
diff --git a/clang/lib/AST/ASTStructuralEquivalence.cpp b/clang/lib/AST/ASTStructuralEquivalence.cpp
index e50c0e64997691..1f314c44c81933 100644
--- a/clang/lib/AST/ASTStructuralEquivalence.cpp
+++ b/clang/lib/AST/ASTStructuralEquivalence.cpp
@@ -661,17 +661,6 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
                                      ArrayRef<TemplateArgumentLoc> Args1,
                                      ArrayRef<TemplateArgumentLoc> Args2);
 
-static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
-                                     const PartiallyAppliedConcept *C1,
-                                     const PartiallyAppliedConcept *C2) {
-  if (!IsStructurallyEquivalent(Context, C1->getNamedConcept(),
-                                C2->getNamedConcept()))
-     return false;
-  return IsStructurallyEquivalent(Context,
-                                  C1->getTemplateArgsAsWritten()->arguments(),
-                                  C2->getTemplateArgsAsWritten()->arguments());
-}
-
 /// Determine whether two template arguments are equivalent.
 static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
                                      const TemplateArgument &Arg1,
@@ -704,11 +693,6 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
     return IsStructurallyEquivalent(Context, Arg1.getAsTemplate(),
                                     Arg2.getAsTemplate());
 
-  case TemplateArgument::Concept:
-    return IsStructurallyEquivalent(Context,
-                                    Arg1.getAsPartiallyAppliedConcept(),
-                                    Arg2.getAsPartiallyAppliedConcept());
-
   case TemplateArgument::TemplateExpansion:
     return IsStructurallyEquivalent(Context,
                                     Arg1.getAsTemplateOrTemplatePattern(),
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index 0173f030c2f48e..cad047b6ed54af 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -360,13 +360,6 @@ LinkageComputer::getLVForTemplateArgumentList(ArrayRef<TemplateArgument> Args,
         LV.merge(getLVForDecl(Template, computation));
       continue;
 
-    // FIXME corentin
-    case TemplateArgument::Concept:
-      if (TemplateDecl *Template =
-              Arg.getAsPartiallyAppliedConcept()->getNamedConcept())
-        LV.merge(getLVForDecl(Template, computation));
-      continue;
-
     case TemplateArgument::Pack:
       LV.merge(getLVForTemplateArgumentList(Arg.getPackAsArray(), computation));
       continue;
diff --git a/clang/lib/AST/DeclTemplate.cpp b/clang/lib/AST/DeclTemplate.cpp
index fbf76fcf9e80de..1a77f19d57cba9 100644
--- a/clang/lib/AST/DeclTemplate.cpp
+++ b/clang/lib/AST/DeclTemplate.cpp
@@ -90,7 +90,7 @@ TemplateParameterList::TemplateParameterList(const ASTContext& C,
       if (TTP->hasTypeConstraint())
         HasConstrainedParameters = true;
     } else {
-      llvm_unreachable("unexpected template parameter type");
+      // llvm_unreachable("unexpected template parameter type");
     }
   }
 
@@ -248,7 +248,7 @@ getAssociatedConstraints(llvm::SmallVectorImpl<const Expr *> &AC) const {
           AC.push_back(E);
       }
     }
-  if (HasRequiresClause)
+  if (HasRequiresClause && getRequiresClause())
     AC.push_back(getRequiresClause());
 }
 
@@ -878,7 +878,7 @@ TemplateTemplateParmDecl *
 TemplateTemplateParmDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID)
       TemplateTemplateParmDecl(nullptr, SourceLocation(), 0, 0, nullptr,
-                               TemplateNameKind::TNK_Type_template, false, nullptr, std::nullopt);
+                               TemplateNameKind::TNK_Type_template, false, nullptr, nullptr);
 }
 
 TemplateTemplateParmDecl *
diff --git a/clang/lib/AST/ExprCXX.cpp b/clang/lib/AST/ExprCXX.cpp
index dc50ab6f1d286c..3f9a775f9da0b2 100644
--- a/clang/lib/AST/ExprCXX.cpp
+++ b/clang/lib/AST/ExprCXX.cpp
@@ -1767,7 +1767,7 @@ QualType SubstNonTypeTemplateParmExpr::getParameterType(
   // T', so we can't just compute this from the type and value category.
 
   QualType Type = getType();
-  if (isa<UniversalTemplateParmDecl>(getParameter()))
+  if (isa<UniversalTemplateParmDecl>(getAssociatedDecl()))
     Type = getReplacement()->getType();
 
   if (isReferenceParameter())
@@ -1974,9 +1974,10 @@ CXXFoldExpr::CXXFoldExpr(QualType T, UnresolvedLookupExpr *Callee,
       EllipsisLoc(EllipsisLoc), RParenLoc(RParenLoc),
       NumExpansions(NumExpansions ? *NumExpansions + 1 : 0), Opcode(Opcode) {
   // We rely on asserted invariant to distinguish left and right folds.
-  assert(((LHS && LHS->containsUnexpandedParameterPack()) !=
-          (RHS && RHS->containsUnexpandedParameterPack())) &&
-         "Exactly one of LHS or RHS should contain an unexpanded pack");
+  if(LHS && RHS)
+    assert(LHS->containsUnexpandedParameterPack() !=
+               RHS->containsUnexpandedParameterPack() &&
+           "Exactly one of LHS or RHS should contain an unexpanded pack");
   SubExprs[SubExpr::Callee] = Callee;
   SubExprs[SubExpr::LHS] = LHS;
   SubExprs[SubExpr::RHS] = RHS;
diff --git a/clang/lib/AST/StmtProfile.cpp b/clang/lib/AST/StmtProfile.cpp
index 1ce962f47aeb7d..ad4281986f668e 100644
--- a/clang/lib/AST/StmtProfile.cpp
+++ b/clang/lib/AST/StmtProfile.cpp
@@ -2455,15 +2455,6 @@ void StmtProfiler::VisitTemplateArgument(const TemplateArgument &Arg) {
     VisitTemplateName(Arg.getAsTemplateOrTemplatePattern());
     break;
 
-  case TemplateArgument::Concept: {
-    PartiallyAppliedConcept* C = Arg.getAsPartiallyAppliedConcept();
-    VisitDecl(C->getNamedConcept());
-    for (const auto &P : C->getTemplateArgsAsWritten()->arguments()) {
-      VisitTemplateArgument(P.getArgument());
-    }
-    break;
-  }
-
   case TemplateArgument::Declaration:
     VisitType(Arg.getParamTypeForDecl());
     // FIXME: Do we need to recursively decompose template parameter objects?
diff --git a/clang/lib/AST/TemplateBase.cpp b/clang/lib/AST/TemplateBase.cpp
index d753cf4a5d7a1c..b4bbbb719f09f0 100644
--- a/clang/lib/AST/TemplateBase.cpp
+++ b/clang/lib/AST/TemplateBase.cpp
@@ -308,10 +308,6 @@ TemplateArgumentDependence TemplateArgument::getDependence() const {
               TemplateArgumentDependence::Instantiation;
     return Deps;
 
-  case Concept: {
-    Deps = getAsPartiallyAppliedConcept()->getDependence();
-    return Deps;
-  }
   case Pack:
     for (const auto &P : pack_elements())
       Deps |= P.getDependence();
@@ -337,7 +333,6 @@ bool TemplateArgument::isPackExpansion() const {
   case Pack:
   case Template:
   case NullPtr:
-  case Concept:
   case Universal:
     return false;
 
@@ -356,8 +351,8 @@ bool TemplateArgument::isPackExpansion() const {
 }
 
 bool TemplateArgument::isConceptOrConceptTemplateParameter() const {
-  bool isConcept = getKind() == TemplateArgument::Concept;
-  if (!isConcept && getKind() == TemplateArgument::Template) {
+  bool isConcept = false;
+  if (getKind() == TemplateArgument::Template) {
     if (isa<ConceptDecl>(getAsTemplate().getAsTemplateDecl()))
       isConcept = true;
     else if (auto *TTP = dyn_cast_if_present<TemplateTemplateParmDecl>(
@@ -389,7 +384,6 @@ QualType TemplateArgument::getNonTypeTemplateArgumentType() const {
   case TemplateArgument::Template:
   case TemplateArgument::TemplateExpansion:
   case TemplateArgument::Pack:
-  case TemplateArgument::Concept:
   case TemplateArgument::Universal:
   case TemplateArgument::UniversalExpansion:
     return QualType();
@@ -440,10 +434,6 @@ void TemplateArgument::Profile(llvm::FoldingSetNodeID &ID,
     ID.AddPointer(TemplateArg.Name);
     break;
 
-  case Concept:
-    getAsPartiallyAppliedConcept()->Profile(ID, Context);
-    break;
-
   case UniversalExpansion:
     ID.AddInteger(UniversalArg.NumExpansions);
     [[fallthrough]];
@@ -492,22 +482,6 @@ bool TemplateArgument::structurallyEquals(const TemplateArgument &Other) const {
     return UniversalArg.D == Other.UniversalArg.D &&
            UniversalArg.NumExpansions == Other.UniversalArg.NumExpansions;
 
-  case Concept: {
-    PartiallyAppliedConcept *C = getAsPartiallyAppliedConcept();
-    PartiallyAppliedConcept *OC = Other.getAsPartiallyAppliedConcept();
-    if (C->getNamedConcept() != OC->getNamedConcept())
-      return false;
-    const ASTTemplateArgumentListInfo *Args = C->getTemplateArgsAsWritten();
-    const ASTTemplateArgumentListInfo *OArgs = OC->getTemplateArgsAsWritten();
-    if (Args->getNumTemplateArgs() != OArgs->getNumTemplateArgs())
-      return false;
-    for (unsigned I = 0; I < Args->getNumTemplateArgs(); I++)
-      if (!Args->arguments()[I].getArgument().structurallyEquals(
-              OArgs->arguments()[I].getArgument()))
-        return false;
-    return true;
-  }
-
   case Declaration:
     return getAsDecl() == Other.getAsDecl() &&
            getParamTypeForDecl() == Other.getParamTypeForDecl();
@@ -560,7 +534,6 @@ TemplateArgument TemplateArgument::getPackExpansionPattern() const {
   case Pack:
   case Null:
   case Template:
-  case Concept:
   case Universal:
   case NullPtr:
     return TemplateArgument();
@@ -629,10 +602,6 @@ void TemplateArgument::print(const PrintingPolicy &Policy, raw_ostream &Out,
     Out << "...";
     break;
 
-  case Concept:
-    getAsPartiallyAppliedConcept()->print(Out, Policy);
-    break;
-
   case Integral:
     printIntegral(*this, Out, Policy, IncludeType);
     break;
@@ -692,10 +661,6 @@ SourceRange TemplateArgumentLoc::getSourceRange() const {
         getArgument().getAsUniversalTemplateParameterOrPattern()->getLocation(),
         getUniversalEllipsisLoc());
 
-    // Fixme ?
-  case TemplateArgument::Concept:
-    return getArgument().getAsPartiallyAppliedConcept()->getSourceRange();
-
   case TemplateArgument::TemplateExpansion:
     if (getTemplateQualifierLoc())
       return SourceRange(getTemplateQualifierLoc().getBeginLoc(),
@@ -754,9 +719,6 @@ static const T &DiagTemplateArg(const T &DB, const TemplateArgument &Arg) {
   case TemplateArgument::TemplateExpansion:
     return DB << Arg.getAsTemplateOrTemplatePattern() << "...";
 
-  case TemplateArgument::Concept:
-    return DB << *Arg.getAsPartiallyAppliedConcept();
-
   case TemplateArgument::Universal:
     return DB << *Arg.getAsUniversalTemplateParameterName();
 
diff --git a/clang/lib/AST/TextNodeDumper.cpp b/clang/lib/AST/TextNodeDumper.cpp
index c1bd94a34e28db..ea592be2a4b1b9 100644
--- a/clang/lib/AST/TextNodeDumper.cpp
+++ b/clang/lib/AST/TextNodeDumper.cpp
@@ -1237,11 +1237,6 @@ void TextNodeDumper::VisitTemplateExpansionTemplateArgument(
   dumpBareTemplateName(TA.getAsTemplateOrTemplatePattern());
 }
 
-void TextNodeDumper::VisitConceptTemplateArgument(const TemplateArgument &TA) {
-  OS << " concept ";
-  OS << TA.getAsPartiallyAppliedConcept()->getConceptNameInfo().getName();
-}
-
 void TextNodeDumper::VisitUniversalTemplateArgument(
     const TemplateArgument &TA) {
   OS << " universal ";
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 8597304dbd3c88..305c0c53943870 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -5532,8 +5532,6 @@ bool CGDebugInfo::HasReconstitutableArgs(
     ArrayRef<TemplateArgument> Args) const {
   return llvm::all_of(Args, [&](const TemplateArgument &TA) {
     switch (TA.getKind()) {
-    case TemplateArgument::Concept:
-      return false;
     case TemplateArgument::Template:
       // Easy to reconstitute - the value of the parameter in the debug
       // info is the string name of the template. The template name
diff --git a/clang/lib/Parse/ParseTemplate.cpp b/clang/lib/Parse/ParseTemplate.cpp
index f38bef2e713aaa..e58ab5ede3b1ce 100644
--- a/clang/lib/Parse/ParseTemplate.cpp
+++ b/clang/lib/Parse/ParseTemplate.cpp
@@ -1551,30 +1551,6 @@ ParsedTemplateArgument Parser::ParseTemplateTemplateArgument() {
   return Result;
 }
 
-///  partially-applied-concept:
-///    concept id-dexpression < arguments >
-ParsedTemplateArgument Parser::ParsePartiallyAppliedConceptTemplateArgument() {
-  if (Tok.isNot(tok::kw_concept))
-    return {};
-  SourceLocation ConceptLoc = ConsumeToken();
-  CXXScopeSpec SS; // nested-name-specifier, if present
-  ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/nullptr,
-                                 /*ObjectHasErrors=*/false,
-                                 /*EnteringContext=*/false);
-  ParsedTemplateArgument Result;
-  if (Tok.is(tok::annot_template_id)) {
-    TemplateIdAnnotation *TemplateId = takeTemplateIdAnnotation(Tok);
-    ConsumeAnnotationToken();
-    PartiallyAppliedConcept *C = Actions.ActOnPartiallyAppliedConcept(
-        getCurScope(), SS, ConceptLoc, TemplateId);
-    if (!C)
-      return {};
-    Result = ParsedTemplateArgument(C, ConceptLoc);
-    return Result;
-  }
-  return {};
-}
-
 ParsedTemplateArgument Parser::ParseUniversalTemplateParamNameArgument() {
   if (!Tok.isOneOf(tok::identifier, tok::annot_universal))
     return ParsedTemplateArgument();
@@ -1661,13 +1637,6 @@ ParsedTemplateArgument Parser::ParseTemplateArgument() {
     TPA.Revert();
   }
 
-  {
-    ParsedTemplateArgument Concept =
-        ParsePartiallyAppliedConceptTemplateArgument();
-    if (!Concept.isInvalid())
-      return Concept;
-  }
-
   {
       TentativeParsingAction TPA(*this);
       // Parse a non-type template argument.
diff --git a/clang/lib/Sema/SemaLookup.cpp b/clang/lib/Sema/SemaLookup.cpp
index e08499bd0cc17e..0592020a87b88d 100644
--- a/clang/lib/Sema/SemaLookup.cpp
+++ b/clang/lib/Sema/SemaLookup.cpp
@@ -2950,7 +2950,6 @@ addAssociatedClassesAndNamespaces(AssociatedLookup &Result,
       break;
     }
 
-    case TemplateArgument::Concept:
     case clang::TemplateArgument::Universal:
     case clang::TemplateArgument::UniversalExpansion:
     case TemplateArgument::Declaration:
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 896cbf70018aee..799e92558659aa 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -941,14 +941,7 @@ static TemplateArgumentLoc translateTemplateArgument(Sema &SemaRef,
         Arg.getScopeSpec().getWithLocInContext(SemaRef.Context),
         Arg.getLocation(), Arg.getEllipsisLoc());
   }
-  case clang::ParsedTemplateArgument::PartiallyAppliedConcept: {
-    PartiallyAppliedConcept *C = Arg.getAsConcept();
-    TemplateArgument TArg(C);
-    return TemplateArgumentLoc(
-        SemaRef.Context, TArg,
-        Arg.getScopeSpec().getWithLocInContext(SemaRef.Context),
-        Arg.getLocation());
-  }
+
   case clang::ParsedTemplateArgument::Universal: {
     UniversalTemplateParamNameTy U = Arg.getAsUniversalTemplateParamName();
     TemplateArgument TArg;
@@ -1210,8 +1203,7 @@ static ExprResult formImmediatelyDeclaredConstraint(
   if (auto *CD = dyn_cast<ConceptDecl>(NamedConcept)) {
     ImmediatelyDeclaredConstraint = S.CheckConceptTemplateId(
         SS, /*TemplateKWLoc=*/SourceLocation(), NameInfo,
-        // /*FoundDecl=*/FoundDecl ? FoundDecl : NamedConcept,
-        NamedConcept,
+        /*FoundDecl=*/FoundDecl ? FoundDecl : NamedConcept,
         CD, &ConstraintArgs);
     if (ImmediatelyDeclaredConstraint.isInvalid() || !EllipsisLoc.isValid())
       return ImmediatelyDeclaredConstraint;
@@ -4965,47 +4957,6 @@ TemplateNameKind Sema::ActOnTemplateName(Scope *S,
   return TNK_Non_template;
 }
 
-PartiallyAppliedConcept *Sema::BuildPartiallyAppliedConcept(
-    NestedNameSpecifierLoc NNS, SourceLocation ConceptKWLoc,
-    DeclarationNameInfo ConceptName, TemplateDecl *TD,
-    const TemplateArgumentListInfo &TemplateArgs) {
-
-  return PartiallyAppliedConcept::Create(getASTContext(), NNS, ConceptName,
-                                         ConceptKWLoc, TD, TD, TemplateArgs);
-}
-
-PartiallyAppliedConcept *
-Sema::ActOnPartiallyAppliedConcept(Scope *S, CXXScopeSpec &SS,
-                                   SourceLocation ConceptKWLoc,
-                                   TemplateIdAnnotation *TemplateId) {
-
-  if (TemplateId->isInvalid())
-    return nullptr;
-  TemplateName TN = TemplateId->Template.get();
-  if (TN.isNull())
-    return nullptr;
-  bool IsConcept = false;
-  TemplateDecl *TD = TN.getAsTemplateDecl();
-  if(!TD)
-    return nullptr;
-  if (TemplateTemplateParmDecl *TTP = dyn_cast<TemplateTemplateParmDecl>(TD))
-    IsConcept = TTP->kind() == TNK_Concept_template;
-  else
-    IsConcept = isa<ConceptDecl>(TD);
-  if (!IsConcept) {
-    Diag(TemplateId->TemplateNameLoc, diag::err_partial_concept_valid_template);
-    return nullptr;
-  }
-
-  DeclarationNameInfo ConceptName(DeclarationName(TemplateId->Name),
-                                  TemplateId->TemplateNameLoc);
-  TemplateArgumentListInfo TemplateArgs =
-      makeTemplateArgumentListInfo(*this, *TemplateId);
-  NestedNameSpecifierLoc NNS = SS.getWithLocInContext(Context);
-  return BuildPartiallyAppliedConcept(NNS, ConceptKWLoc, ConceptName, TD,
-                                      TemplateArgs);
-}
-
 bool Sema::ActOnUniversalTemplateParameterName(
     Scope *S, const UnqualifiedId &Name, bool EnteringContext,
     UniversalTemplateParamNameTy &Template) {
@@ -5232,7 +5183,6 @@ bool Sema::CheckUniversalTemplateParameterArgument(
     CanonicalConverted.push_back(CanonicalResult);
     break;
   }
-  case TemplateArgument::Concept:
     // TODO check invalid
   case TemplateArgument::Declaration:
   case TemplateArgument::Integral:
@@ -5607,13 +5557,6 @@ bool Sema::CheckTemplateArgument(
           Context.getCanonicalTemplateArgument(Arg.getArgument()));
       break;
 
-    // TODO support non-type concepts
-    case TemplateArgument::Concept:
-      Diag(Arg.getLocation(), diag::err_template_arg_must_be_expr)
-          << Arg.getSourceRange();
-      Diag(Param->getLocation(), diag::note_template_param_here);
-      return true;
-
     case TemplateArgument::Universal:
       SugaredConverted.push_back(Arg.getArgument());
       CanonicalConverted.push_back(
@@ -5750,15 +5693,6 @@ bool Sema::CheckTemplateArgument(
   case TemplateArgument::Null:
     llvm_unreachable("Should never see a NULL template argument here");
 
-  case TemplateArgument::Concept:
-    if (CheckPartiallyAppliedConceptTemplateArgument(TempParm, Params, Arg))
-      return true;
-
-    SugaredConverted.push_back(Arg.getArgument());
-    CanonicalConverted.push_back(
-        Context.getCanonicalTemplateArgument(Arg.getArgument()));
-    break;
-
   case TemplateArgument::Template:
   case TemplateArgument::TemplateExpansion:
     if (CheckTemplateTemplateArgument(TempParm, Params, Arg,
@@ -7874,45 +7808,6 @@ void Sema::NoteTemplateParameterLocation(const NamedDecl &Decl) {
                diag::note_template_param_external);
 }
 
-bool Sema::CheckPartiallyAppliedConceptTemplateArgument(
-    TemplateTemplateParmDecl *Param, TemplateParameterList *Params,
-    TemplateArgumentLoc &Arg) {
-  PartiallyAppliedConcept *C = Arg.getArgument().getAsPartiallyAppliedConcept();
-  TemplateDecl *Template = C->getNamedConcept();
-  if (Template->isInvalidDecl())
-    return true;
-
-  if (!CheckDeclCompatibleWithTemplateTemplate(Template, Param, Arg)) {
-    return true;
-  }
-  if (Params->size() != 1) {
-    Diag(C->getSourceRange().getBegin(),
-         diag::err_partial_concept_param_must_have_one_arg);
-    Diag(Param->getLocation(),
-         diag::note_concept_template_parameter_declared_here)
-        << Param;
-    return true;
-  }
-  unsigned MinArguments =
-      Template->getTemplateParameters()->getMinRequiredArguments();
-
-  auto Passed = C->getTemplateArgsAsWritten()->getNumTemplateArgs();
-  bool TooFew  = MinArguments > Passed + 1;
-  bool TooMany = Passed +1 > Template->getTemplateParameters()->size() &&
-                 !Template->getTemplateParameters()->hasParameterPack();
-
-  if (TooFew || TooMany) {
-    Diag(C->getSourceRange().getBegin(),
-         diag::err_template_arg_list_different_arity)
-        << (TooFew ? 0 : 1) << /*Concept*/ 5 << Template;
-    Diag(Template->getLocation(), diag::note_template_decl_here)
-        << Template->getTemplateParameters()->getSourceRange();
-    return true;
-  }
-
-  return false;
-}
-
 /// Given a non-type template argument that refers to a
 /// declaration and the type of its corresponding non-type template
 /// parameter, produce an expression that properly refers to that
diff --git a/clang/lib/Sema/SemaTemplateInstantiate.cpp b/clang/lib/Sema/SemaTemplateInstantiate.cpp
index 5a93c3243089f7..eedeb09f71a9dd 100644
--- a/clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -1461,9 +1461,6 @@ namespace {
     /// this declaration.
     Decl *TransformDecl(SourceLocation Loc, Decl *D);
 
-    bool InjectAdditionalArgumentsFromPartiallyAppliedConcept(
-        TemplateArgumentListInfo &Args, TemplateDecl *D);
-
     void transformAttrs(Decl *Old, Decl *New) {
       SemaRef.InstantiateAttrs(TemplateArgs, Old, New);
     }
@@ -1866,10 +1863,6 @@ Decl *TemplateInstantiator::TransformDecl(SourceLocation Loc, Decl *D) {
         Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
       }
 
-      if (Arg.getKind() == clang::TemplateArgument::Concept) {
-        return Arg.getAsPartiallyAppliedConcept()->getNamedConcept();
-      }
-
       TemplateName Template = Arg.getAsTemplate();
 
       assert(!Template.isNull() && Template.getAsTemplateDecl() &&
@@ -1889,23 +1882,6 @@ Decl *TemplateInstantiator::TransformDecl(SourceLocation Loc, Decl *D) {
   return SemaRef.FindInstantiatedDecl(Loc, cast<NamedDecl>(D), TemplateArgs);
 }
 
-bool TemplateInstantiator::InjectAdditionalArgumentsFromPartiallyAppliedConcept(
-    TemplateArgumentListInfo &Args, TemplateDecl *D) {
-  auto [Depth, Index] = getDepthAndIndex(D);
-  if (Depth >= TemplateArgs.getNumLevels())
-    return false;
-  if (!TemplateArgs.hasTemplateArgument(Depth, Index))
-    return false;
-  TemplateArgument Arg = TemplateArgs(Depth, Index);
-  if (Arg.getKind() != clang::TemplateArgument::Concept)
-    return false;
-  PartiallyAppliedConcept *C = Arg.getAsPartiallyAppliedConcept();
-  for (auto &Arg : C->getTemplateArgsAsWritten()->arguments()) {
-    Args.addArgument(Arg);
-  }
-  return true;
-}
-
 Decl *TemplateInstantiator::TransformDefinition(SourceLocation Loc, Decl *D) {
   Decl *Inst = getSema().SubstDecl(D, getSema().CurContext, TemplateArgs);
   if (!Inst)
@@ -2113,38 +2089,6 @@ TemplateArgument TemplateInstantiator::TransformNamedTemplateTemplateArgument(
         return TemplateArgument(Name);
 
       TemplateArgument Arg = TemplateArgs(TTP->getDepth(), TTP->getPosition());
-      if (Arg.getKind() == TemplateArgument::Concept) {
-        PartiallyAppliedConcept *C = Arg.getAsPartiallyAppliedConcept();
-        TemplateDecl *T = cast_or_null<TemplateDecl>(getDerived().TransformDecl(
-            C->getConceptNameLoc(), C->getNamedConcept()));
-        if (!T)
-          return TemplateArgument();
-
-        if (T == C->getNamedConcept() && !getDerived().AlwaysRebuild())
-          return Arg;
-
-        DeclarationNameInfo NameInfo = C->getConceptNameInfo();
-        if (NameInfo.getName()) {
-          NameInfo = getDerived().TransformDeclarationNameInfo(NameInfo);
-          if (!NameInfo.getName())
-            return TemplateArgument();
-        }
-
-        TemplateArgumentListInfo NewTemplateArgs;
-        NewTemplateArgs.setLAngleLoc(
-            C->getTemplateArgsAsWritten()->getLAngleLoc());
-        NewTemplateArgs.setLAngleLoc(
-            C->getTemplateArgsAsWritten()->getRAngleLoc());
-        for (auto &Arg : C->getTemplateArgsAsWritten()->arguments())
-          NewTemplateArgs.addArgument(Arg);
-
-        PartiallyAppliedConcept *Transformed =
-            SemaRef.BuildPartiallyAppliedConcept(C->getNestedNameSpecifierLoc(),
-                                                 C->getConceptKWLoc(), NameInfo,
-                                                 T, NewTemplateArgs);
-        if (!Transformed)
-          return TemplateArgument(Transformed);
-      }
     }
   }
   TemplateName TN = getDerived().TransformTemplateName(SS, Name, NameLoc);
@@ -2234,7 +2178,6 @@ NamedDecl *TemplateInstantiator::TransformUniversalTemplateParameter(
   case TemplateArgument::TemplateExpansion:
   case TemplateArgument::UniversalExpansion:
   case TemplateArgument::Pack:
-  case TemplateArgument::Concept:
     assert(false && "non implemented");
     break;
 
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index d5b636423253b6..aee84e54c23e88 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -25,6 +25,7 @@
 #include "clang/AST/Type.h"
 #include "clang/AST/TypeLoc.h"
 #include "clang/AST/TypeLocVisitor.h"
+#include "clang/Basic/LLVM.h"
 #include "clang/Basic/LangOptions.h"
 #include "clang/Basic/PartialDiagnostic.h"
 #include "clang/Basic/SourceLocation.h"
@@ -3062,13 +3063,12 @@ InventTemplateParameter(TypeProcessingState &state, QualType T,
       if (!Invalid) {
         UsingShadowDecl *USD =
             TemplateId->Template.get().getAsUsingShadowDecl();
-        auto *CD =
-            cast<ConceptDecl>(TemplateId->Template.get().getAsTemplateDecl());
+        TemplateDecl *CD = TemplateId->Template.get().getAsTemplateDecl();
         S.AttachTypeConstraint(
             D.getDeclSpec().getTypeSpecScope().getWithLocInContext(S.Context),
             DeclarationNameInfo(DeclarationName(TemplateId->Name),
                                 TemplateId->TemplateNameLoc),
-            cast<TemplateDecl>(TemplateId->Template.get().getAsTemplateDecl()),
+            CD,
             /*FoundDecl=*/USD ? cast<NamedDecl>(USD) : CD,
             TemplateId->LAngleLoc.isValid() ? &TemplateArgsInfo : nullptr,
             InventedTemplateParam, D.getEllipsisLoc());
diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index 174ebf067a6be5..3902996b227402 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -649,11 +649,6 @@ class TreeTransform {
                                       Uneval);
   }
 
-  bool InjectAdditionalArgumentsFromPartiallyAppliedConcept(
-      TemplateArgumentListInfo &, TemplateDecl *) {
-    return true;
-  }
-
   /// Transform the given set of template arguments.
   ///
   /// By default, this operation transforms all of the template arguments
@@ -4029,7 +4024,6 @@ class TreeTransform {
     case TemplateArgument::UniversalExpansion:
     case TemplateArgument::TemplateExpansion:
     case TemplateArgument::NullPtr:
-    case TemplateArgument::Concept:
       llvm_unreachable("Pack expansion pattern has no parameter packs");
 
     case TemplateArgument::Type:
@@ -4842,36 +4836,6 @@ bool TreeTransform<Derived>::TransformTemplateArgument(
     return false;
   }
 
-  case TemplateArgument::Concept: {
-    PartiallyAppliedConcept *C = Arg.getAsPartiallyAppliedConcept();
-    TemplateDecl *T = cast_or_null<TemplateDecl>(getDerived().TransformDecl(
-        C->getConceptNameLoc(), C->getNamedConcept()));
-    if (!T)
-      return true;
-    DeclarationNameInfo NameInfo = C->getConceptNameInfo();
-    if (NameInfo.getName()) {
-      NameInfo = getDerived().TransformDeclarationNameInfo(NameInfo);
-      if (!NameInfo.getName())
-        return true;
-    }
-
-    TemplateArgumentListInfo NewTemplateArgs;
-    getDerived().TransformTemplateArguments(
-        C->getTemplateArgsAsWritten()->getTemplateArgs(),
-        C->getTemplateArgsAsWritten()->getNumTemplateArgs(), NewTemplateArgs);
-
-    PartiallyAppliedConcept *Transformed = SemaRef.BuildPartiallyAppliedConcept(
-        C->getNestedNameSpecifierLoc(), C->getConceptKWLoc(), NameInfo, T,
-        NewTemplateArgs);
-    if (!Transformed)
-      return true;
-
-    Output = TemplateArgumentLoc(SemaRef.Context, TemplateArgument(Transformed),
-                                 C->getNestedNameSpecifierLoc(),
-                                 NameInfo.getLoc(), SourceLocation());
-    return false;
-  }
-
   case TemplateArgument::Universal: {
     UniversalTemplateParameterName *N =
         Arg.getAsUniversalTemplateParameterName();
@@ -5103,8 +5067,8 @@ bool TreeTransform<Derived>::TransformConceptTemplateArguments(
     bool Uneval) {
 
   auto isConcept = [](const TemplateArgument &Arg) {
-    bool isConcept = Arg.getKind() == TemplateArgument::Concept;
-    if (!isConcept && Arg.getKind() == TemplateArgument::Template)
+    bool isConcept = false;
+    if (Arg.getKind() == TemplateArgument::Template)
       if (auto *TTP = dyn_cast_if_present<TemplateTemplateParmDecl>(
               Arg.getAsTemplate().getAsTemplateDecl()))
         isConcept = TTP->kind() == TNK_Concept_template;
@@ -14065,12 +14029,6 @@ TreeTransform<Derived>::TransformUnresolvedLookupExpr(UnresolvedLookupExpr *Old,
     R.clear();
     return ExprError();
   }
-
-  if (Old->isConceptReference()) {
-    getDerived().InjectAdditionalArgumentsFromPartiallyAppliedConcept(
-        TransArgs, Old->getTemplateDecl());
-  }
-
   // An UnresolvedLookupExpr can refer to a class member. This occurs e.g. when
   // a non-static data member is named in an unevaluated operand, or when
   // a member is named in a dependent class scope function template explicit
diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 9272e23c7da3fc..38dead8d9dba5d 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -2715,6 +2715,7 @@ void ASTDeclReader::VisitNonTypeTemplateParmDecl(NonTypeTemplateParmDecl *D) {
 
 void ASTDeclReader::VisitTemplateTemplateParmDecl(TemplateTemplateParmDecl *D) {
   VisitTemplateDecl(D);
+  D->ParameterKind = static_cast<TemplateNameKind>(Record.readInt());
   D->setDeclaredWithTypename(Record.readBool());
   // TemplateParmPosition.
   D->setDepth(Record.readInt());
diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index 555f6325da646b..7c4af76de1eff3 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -1952,6 +1952,7 @@ void ASTDeclWriter::VisitTemplateTemplateParmDecl(TemplateTemplateParmDecl *D) {
     Record.push_back(D->getNumExpansionTemplateParameters());
 
   VisitTemplateDecl(D);
+  Record.push_back(D->kind());
   Record.push_back(D->wasDeclaredWithTypename());
   // TemplateParmPosition.
   Record.push_back(D->getDepth());
diff --git a/clang/test/Sema/cxx2c-partially-applied-concepts.cpp b/clang/test/Sema/cxx2c-partially-applied-concepts.cpp
deleted file mode 100644
index 15f67888552ea3..00000000000000
--- a/clang/test/Sema/cxx2c-partially-applied-concepts.cpp
+++ /dev/null
@@ -1,38 +0,0 @@
-// RUN:  %clang_cc1 -std=c++2b -verify %s
-
-template <typename C, typename>
-concept Concept = true; // expected-note 2{{template is declared here}}
-
-template <template <typename> concept C>
-struct S {
-};
-
-template <typename>
-struct NotAConcept {};
-
-S<concept Concept<int>> s;
-S<concept Concept<int, int>> s; // expected-error {{too many template arguments for concept 'Concept'}}
-S<concept Concept<>> s; // expected-error {{too few template arguments for concept 'Concept'}}
-
-
-
-S<concept Concept<1>> s2;
-S<concept NotAConcept<int>> s3; // expected-error {{name of template argument does not refer to concept, or concept template parameter}} \
-                                // expected-error {{expected expression}}
-namespace BasicOverloading {
-
-template <template <typename...T> concept C>
-void f();
-
-template <bool b>
-void f();
-
-template <typename...>
-concept C = true;
-
-void test() {
-    f<C<int>>();
-    f<concept C<int>>();
-}
-
-}