diff --git a/clang/include/clang/AST/DeclTemplate.h b/clang/include/clang/AST/DeclTemplate.h
index 3677335fa176f..7cd505218f2b9 100644
--- a/clang/include/clang/AST/DeclTemplate.h
+++ b/clang/include/clang/AST/DeclTemplate.h
@@ -2309,9 +2309,15 @@ class ClassTemplateDecl : public RedeclarableTemplateDecl {
     return static_cast<Common *>(RedeclarableTemplateDecl::getCommonPtr());
   }
 
+  void setCommonPtr(Common *C) {
+    RedeclarableTemplateDecl::Common = C;
+  }
+
 public:
+
   friend class ASTDeclReader;
   friend class ASTDeclWriter;
+  friend class TemplateDeclInstantiator;
 
   /// Load any lazily-loaded specializations from the external source.
   void LoadLazySpecializations() const;
diff --git a/clang/include/clang/Sema/Template.h b/clang/include/clang/Sema/Template.h
index 48e8b78311e12..1de2cc6917b42 100644
--- a/clang/include/clang/Sema/Template.h
+++ b/clang/include/clang/Sema/Template.h
@@ -232,9 +232,21 @@ enum class TemplateSubstitutionKind : char {
     /// Replaces the current 'innermost' level with the provided argument list.
     /// This is useful for type deduction cases where we need to get the entire
     /// list from the AST, but then add the deduced innermost list.
-    void replaceInnermostTemplateArguments(ArgList Args) {
-      assert(TemplateArgumentLists.size() > 0 && "Replacing in an empty list?");
-      TemplateArgumentLists[0].Args = Args;
+    void replaceInnermostTemplateArguments(Decl *AssociatedDecl, ArgList Args) {
+      assert((!TemplateArgumentLists.empty() || NumRetainedOuterLevels) &&
+             "Replacing in an empty list?");
+
+      if (!TemplateArgumentLists.empty()) {
+        assert((TemplateArgumentLists[0].AssociatedDeclAndFinal.getPointer() ||
+                TemplateArgumentLists[0].AssociatedDeclAndFinal.getPointer() ==
+                    AssociatedDecl) &&
+               "Trying to change incorrect declaration?");
+        TemplateArgumentLists[0].Args = Args;
+      } else {
+        --NumRetainedOuterLevels;
+        TemplateArgumentLists.push_back(
+            {{AssociatedDecl, /*Final=*/false}, Args});
+      }
     }
 
     /// Add an outermost level that we are not substituting. We have no
diff --git a/clang/lib/Sema/SemaConcept.cpp b/clang/lib/Sema/SemaConcept.cpp
index 7aa06b615fec2..1126c2c517fe4 100644
--- a/clang/lib/Sema/SemaConcept.cpp
+++ b/clang/lib/Sema/SemaConcept.cpp
@@ -722,7 +722,7 @@ CalculateTemplateDepthForConstraints(Sema &S, const NamedDecl *ND,
       ND, /*Final=*/false, /*Innermost=*/nullptr, /*RelativeToPrimary=*/true,
       /*Pattern=*/nullptr,
       /*ForConstraintInstantiation=*/true, SkipForSpecialization);
-  return MLTAL.getNumSubstitutedLevels();
+  return MLTAL.getNumLevels();
 }
 
 namespace {
@@ -753,27 +753,44 @@ namespace {
   };
 } // namespace
 
+static const Expr *SubstituteConstraintExpression(Sema &S, const NamedDecl *ND,
+                                                  const Expr *ConstrExpr) {
+  MultiLevelTemplateArgumentList MLTAL = S.getTemplateInstantiationArgs(
+      ND, /*Final=*/false, /*Innermost=*/nullptr,
+      /*RelativeToPrimary=*/true,
+      /*Pattern=*/nullptr, /*ForConstraintInstantiation=*/true,
+      /*SkipForSpecialization*/ false);
+  if (MLTAL.getNumSubstitutedLevels() == 0)
+    return ConstrExpr;
+
+  Sema::SFINAETrap SFINAE(S, /*AccessCheckingSFINAE=*/false);
+  std::optional<Sema::CXXThisScopeRAII> ThisScope;
+  if (auto *RD = dyn_cast<CXXRecordDecl>(ND->getDeclContext()))
+    ThisScope.emplace(S, const_cast<CXXRecordDecl *>(RD), Qualifiers());
+  ExprResult SubstConstr =
+      S.SubstConstraintExpr(const_cast<clang::Expr *>(ConstrExpr), MLTAL);
+  if (SFINAE.hasErrorOccurred() || !SubstConstr.isUsable())
+    return nullptr;
+  return SubstConstr.get();
+}
+
 bool Sema::AreConstraintExpressionsEqual(const NamedDecl *Old,
                                          const Expr *OldConstr,
                                          const NamedDecl *New,
                                          const Expr *NewConstr) {
+  if (OldConstr == NewConstr)
+    return true;
   if (Old && New && Old != New) {
-    unsigned Depth1 = CalculateTemplateDepthForConstraints(
-        *this, Old);
-    unsigned Depth2 = CalculateTemplateDepthForConstraints(
-        *this, New);
-
-    // Adjust the 'shallowest' verison of this to increase the depth to match
-    // the 'other'.
-    if (Depth2 > Depth1) {
-      OldConstr = AdjustConstraintDepth(*this, Depth2 - Depth1)
-                      .TransformExpr(const_cast<Expr *>(OldConstr))
-                      .get();
-    } else if (Depth1 > Depth2) {
-      NewConstr = AdjustConstraintDepth(*this, Depth1 - Depth2)
-                      .TransformExpr(const_cast<Expr *>(NewConstr))
-                      .get();
-    }
+    if (const Expr *SubstConstr =
+            SubstituteConstraintExpression(*this, Old, OldConstr))
+      OldConstr = SubstConstr;
+    else
+      return false;
+    if (const Expr *SubstConstr =
+            SubstituteConstraintExpression(*this, New, NewConstr))
+      NewConstr = SubstConstr;
+    else
+      return false;
   }
 
   llvm::FoldingSetNodeID ID1, ID2;
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index 29d6bd852ec67..135bf8053a964 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -1297,7 +1297,7 @@ bool Sema::IsOverload(FunctionDecl *New, FunctionDecl *Old,
     // We check the return type and template parameter lists for function
     // templates first; the remaining checks follow.
     bool SameTemplateParameterList = TemplateParameterListsAreEqual(
-        NewTemplate->getTemplateParameters(),
+        NewTemplate, NewTemplate->getTemplateParameters(), OldTemplate,
         OldTemplate->getTemplateParameters(), false, TPL_TemplateMatch);
     bool SameReturnType = Context.hasSameType(Old->getDeclaredReturnType(),
                                               New->getDeclaredReturnType());
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index b249d389bb677..db72b8b3089e6 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -2882,7 +2882,7 @@ CheckDeducedArgumentConstraints(Sema &S, TemplateDeclT *Template,
   // not class-scope explicit specialization, so replace with Deduced Args
   // instead of adding to inner-most.
   if (NeedsReplacement)
-    MLTAL.replaceInnermostTemplateArguments(CanonicalDeducedArgs);
+    MLTAL.replaceInnermostTemplateArguments(Template, CanonicalDeducedArgs);
 
   if (S.CheckConstraintSatisfaction(Template, AssociatedConstraints, MLTAL,
                                     Info.getLocation(),
diff --git a/clang/lib/Sema/SemaTemplateInstantiate.cpp b/clang/lib/Sema/SemaTemplateInstantiate.cpp
index a25f8175ebcdb..3d5da5f8d8284 100644
--- a/clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -133,6 +133,14 @@ HandleDefaultTempArgIntoTempTempParam(const TemplateTemplateParmDecl *TTP,
   return Response::Done();
 }
 
+Response HandlePartialClassTemplateSpec(
+    const ClassTemplatePartialSpecializationDecl *PartialClassTemplSpec,
+    MultiLevelTemplateArgumentList &Result, bool SkipForSpecialization) {
+  if (!SkipForSpecialization)
+      Result.addOuterRetainedLevels(PartialClassTemplSpec->getTemplateDepth());
+  return Response::Done();
+}
+
 // Add template arguments from a class template instantiation.
 Response
 HandleClassTemplateSpec(const ClassTemplateSpecializationDecl *ClassTemplSpec,
@@ -210,6 +218,21 @@ Response HandleFunction(const FunctionDecl *Function,
   return Response::UseNextDecl(Function);
 }
 
+Response HandleFunctionTemplateDecl(const FunctionTemplateDecl *FTD,
+                                    MultiLevelTemplateArgumentList &Result) {
+  if (!isa<ClassTemplateSpecializationDecl>(FTD->getDeclContext())) {
+    NestedNameSpecifier *NNS = FTD->getTemplatedDecl()->getQualifier();
+    const Type *Ty;
+    const TemplateSpecializationType *TSTy;
+    if (NNS && (Ty = NNS->getAsType()) &&
+        (TSTy = Ty->getAs<TemplateSpecializationType>()))
+      Result.addOuterTemplateArguments(const_cast<FunctionTemplateDecl *>(FTD),
+                                       TSTy->template_arguments(),
+                                       /*Final=*/false);
+  }
+  return Response::ChangeDecl(FTD->getLexicalDeclContext());
+}
+
 Response HandleRecordDecl(const CXXRecordDecl *Rec,
                           MultiLevelTemplateArgumentList &Result,
                           ASTContext &Context,
@@ -220,15 +243,10 @@ Response HandleRecordDecl(const CXXRecordDecl *Rec,
         "Outer template not instantiated?");
     if (ClassTemplate->isMemberSpecialization())
       return Response::Done();
-    if (ForConstraintInstantiation) {
-      QualType RecordType = Context.getTypeDeclType(Rec);
-      QualType Injected = cast<InjectedClassNameType>(RecordType)
-                              ->getInjectedSpecializationType();
-      const auto *InjectedType = cast<TemplateSpecializationType>(Injected);
+    if (ForConstraintInstantiation)
       Result.addOuterTemplateArguments(const_cast<CXXRecordDecl *>(Rec),
-                                       InjectedType->template_arguments(),
+                                       ClassTemplate->getInjectedTemplateArgs(),
                                        /*Final=*/false);
-    }
   }
 
   bool IsFriend = Rec->getFriendObjectKind() ||
@@ -296,18 +314,23 @@ MultiLevelTemplateArgumentList Sema::getTemplateInstantiationArgs(
   // Accumulate the set of template argument lists in this structure.
   MultiLevelTemplateArgumentList Result;
 
-  if (Innermost)
+  using namespace TemplateInstArgsHelpers;
+  const Decl *CurDecl = ND;
+  if (Innermost) {
     Result.addOuterTemplateArguments(const_cast<NamedDecl *>(ND),
                                      Innermost->asArray(), Final);
-
-  const Decl *CurDecl = ND;
+    CurDecl = Response::UseNextDecl(ND).NextDecl;
+  }
 
   while (!CurDecl->isFileContextDecl()) {
-    using namespace TemplateInstArgsHelpers;
     Response R;
     if (const auto *VarTemplSpec =
             dyn_cast<VarTemplateSpecializationDecl>(CurDecl)) {
       R = HandleVarTemplateSpec(VarTemplSpec, Result, SkipForSpecialization);
+    } else if (const auto *PartialClassTemplSpec =
+                   dyn_cast<ClassTemplatePartialSpecializationDecl>(CurDecl)) {
+      R = HandlePartialClassTemplateSpec(PartialClassTemplSpec, Result,
+                                         SkipForSpecialization);
     } else if (const auto *ClassTemplSpec =
                    dyn_cast<ClassTemplateSpecializationDecl>(CurDecl)) {
       R = HandleClassTemplateSpec(ClassTemplSpec, Result,
@@ -320,6 +343,8 @@ MultiLevelTemplateArgumentList Sema::getTemplateInstantiationArgs(
     } else if (const auto *CSD =
                    dyn_cast<ImplicitConceptSpecializationDecl>(CurDecl)) {
       R = HandleImplicitConceptSpecializationDecl(CSD, Result);
+    } else if (const auto *FTD = dyn_cast<FunctionTemplateDecl>(CurDecl)) {
+      R = HandleFunctionTemplateDecl(FTD, Result);
     } else if (!isa<DeclContext>(CurDecl)) {
       R = Response::DontClearRelativeToPrimaryNextDecl(CurDecl);
       if (CurDecl->getDeclContext()->isTranslationUnit()) {
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index e74b2b2e868ee..3c78343eb861b 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -1654,33 +1654,12 @@ Decl *TemplateDeclInstantiator::VisitClassTemplateDecl(ClassTemplateDecl *D) {
         << QualifierLoc.getSourceRange();
       return nullptr;
     }
-
-    if (PrevClassTemplate) {
-      const ClassTemplateDecl *MostRecentPrevCT =
-          PrevClassTemplate->getMostRecentDecl();
-      TemplateParameterList *PrevParams =
-          MostRecentPrevCT->getTemplateParameters();
-
-      // Make sure the parameter lists match.
-      if (!SemaRef.TemplateParameterListsAreEqual(
-              D->getTemplatedDecl(), InstParams,
-              MostRecentPrevCT->getTemplatedDecl(), PrevParams, true,
-              Sema::TPL_TemplateMatch))
-        return nullptr;
-
-      // Do some additional validation, then merge default arguments
-      // from the existing declarations.
-      if (SemaRef.CheckTemplateParameterList(InstParams, PrevParams,
-                                             Sema::TPC_ClassTemplate))
-        return nullptr;
-    }
   }
 
   CXXRecordDecl *RecordInst = CXXRecordDecl::Create(
       SemaRef.Context, Pattern->getTagKind(), DC, Pattern->getBeginLoc(),
       Pattern->getLocation(), Pattern->getIdentifier(), PrevDecl,
       /*DelayTypeCreation=*/true);
-
   if (QualifierLoc)
     RecordInst->setQualifierInfo(QualifierLoc);
 
@@ -1690,16 +1669,38 @@ Decl *TemplateDeclInstantiator::VisitClassTemplateDecl(ClassTemplateDecl *D) {
   ClassTemplateDecl *Inst
     = ClassTemplateDecl::Create(SemaRef.Context, DC, D->getLocation(),
                                 D->getIdentifier(), InstParams, RecordInst);
-  assert(!(isFriend && Owner->isDependentContext()));
-  Inst->setPreviousDecl(PrevClassTemplate);
-
   RecordInst->setDescribedClassTemplate(Inst);
 
   if (isFriend) {
-    if (PrevClassTemplate)
+    assert(!Owner->isDependentContext());
+    Inst->setLexicalDeclContext(Owner);
+    RecordInst->setLexicalDeclContext(Owner);
+
+    if (PrevClassTemplate) {
+      Inst->setCommonPtr(PrevClassTemplate->getCommonPtr());
+      RecordInst->setTypeForDecl(
+          PrevClassTemplate->getTemplatedDecl()->getTypeForDecl());
+      const ClassTemplateDecl *MostRecentPrevCT =
+          PrevClassTemplate->getMostRecentDecl();
+      TemplateParameterList *PrevParams =
+          MostRecentPrevCT->getTemplateParameters();
+
+      // Make sure the parameter lists match.
+      if (!SemaRef.TemplateParameterListsAreEqual(
+              RecordInst, InstParams, MostRecentPrevCT->getTemplatedDecl(),
+              PrevParams, true, Sema::TPL_TemplateMatch))
+        return nullptr;
+
+      // Do some additional validation, then merge default arguments
+      // from the existing declarations.
+      if (SemaRef.CheckTemplateParameterList(InstParams, PrevParams,
+                                             Sema::TPC_ClassTemplate))
+        return nullptr;
+
       Inst->setAccess(PrevClassTemplate->getAccess());
-    else
+    } else {
       Inst->setAccess(D->getAccess());
+    }
 
     Inst->setObjectOfFriendDecl();
     // TODO: do we want to track the instantiation progeny of this
@@ -1710,15 +1711,15 @@ Decl *TemplateDeclInstantiator::VisitClassTemplateDecl(ClassTemplateDecl *D) {
       Inst->setInstantiatedFromMemberTemplate(D);
   }
 
+  Inst->setPreviousDecl(PrevClassTemplate);
+
   // Trigger creation of the type for the instantiation.
-  SemaRef.Context.getInjectedClassNameType(RecordInst,
-                                    Inst->getInjectedClassNameSpecialization());
+  SemaRef.Context.getInjectedClassNameType(
+      RecordInst, Inst->getInjectedClassNameSpecialization());
 
   // Finish handling of friends.
   if (isFriend) {
     DC->makeDeclVisibleInContext(Inst);
-    Inst->setLexicalDeclContext(Owner);
-    RecordInst->setLexicalDeclContext(Owner);
     return Inst;
   }
 
diff --git a/clang/test/SemaTemplate/concepts-friends.cpp b/clang/test/SemaTemplate/concepts-friends.cpp
index 3a9b308a65c5d..5c4609520a3c7 100644
--- a/clang/test/SemaTemplate/concepts-friends.cpp
+++ b/clang/test/SemaTemplate/concepts-friends.cpp
@@ -441,3 +441,27 @@ namespace NTTP {
     templ_func<1>(u2);
   }
 }
+
+
+namespace FriendOfFriend {
+
+template <typename>
+concept Concept = true;
+
+template <Concept> class FriendOfBar;
+
+template <Concept> class Bar {
+  template <Concept> friend class FriendOfBar;
+};
+
+Bar<void> BarInstance;
+
+namespace internal {
+void FriendOfFoo(FriendOfBar<void>);
+}
+
+template <Concept> class Foo {
+  friend void internal::FriendOfFoo(FriendOfBar<void>);
+};
+
+} // namespace FriendOfFriend
diff --git a/clang/test/SemaTemplate/concepts-out-of-line-def.cpp b/clang/test/SemaTemplate/concepts-out-of-line-def.cpp
index 222b78e0d22f7..b7c91712f8713 100644
--- a/clang/test/SemaTemplate/concepts-out-of-line-def.cpp
+++ b/clang/test/SemaTemplate/concepts-out-of-line-def.cpp
@@ -127,3 +127,275 @@ static_assert(S<XY>::specialization("str") == SPECIALIZATION_CONCEPT);
 static_assert(S<int>::specialization("str") == SPECIALIZATION_REQUIRES);
 
 } // namespace multiple_template_parameter_lists
+
+static constexpr int CONSTRAINED_METHOD_1 = 1;
+static constexpr int CONSTRAINED_METHOD_2 = 2;
+
+namespace constrained_members {
+
+template <int>
+struct S {
+  template <Concept C>
+  static constexpr int constrained_method();
+};
+
+template <>
+template <Concept C>
+constexpr int S<1>::constrained_method() { return CONSTRAINED_METHOD_1; }
+
+template <>
+template <Concept C>
+constexpr int S<2>::constrained_method() { return CONSTRAINED_METHOD_2; }
+
+static_assert(S<1>::constrained_method<XY>() == CONSTRAINED_METHOD_1);
+static_assert(S<2>::constrained_method<XY>() == CONSTRAINED_METHOD_2);
+
+
+template <class T1, class T2>
+concept ConceptT1T2 = true;
+
+template<typename T3>
+struct S12 {
+  template<ConceptT1T2<T3> T4>
+  static constexpr int constrained_method();
+};
+
+template<>
+template<ConceptT1T2<int> T5>
+constexpr int S12<int>::constrained_method() { return CONSTRAINED_METHOD_1; }
+
+template<>
+template<ConceptT1T2<double> T5>
+constexpr int S12<double>::constrained_method() { return CONSTRAINED_METHOD_2; }
+
+static_assert(S12<int>::constrained_method<XY>() == CONSTRAINED_METHOD_1);
+static_assert(S12<double>::constrained_method<XY>() == CONSTRAINED_METHOD_2);
+
+} // namespace constrained members
+
+namespace constrained_members_of_nested_types {
+
+template <int>
+struct S {
+  struct Inner0 {
+    struct Inner1 {
+      template <Concept C>
+      static constexpr int constrained_method();
+    };
+  };
+};
+
+template <>
+template <Concept C>
+constexpr int S<1>::Inner0::Inner1::constrained_method() { return CONSTRAINED_METHOD_1; }
+
+template <>
+template <Concept C>
+constexpr int S<2>::Inner0::Inner1::constrained_method() { return CONSTRAINED_METHOD_2; }
+
+static_assert(S<1>::Inner0::Inner1::constrained_method<XY>() == CONSTRAINED_METHOD_1);
+static_assert(S<2>::Inner0::Inner1::constrained_method<XY>() == CONSTRAINED_METHOD_2);
+
+
+template <class T1, class T2>
+concept ConceptT1T2 = true;
+
+template<typename T3>
+struct S12 {
+  struct Inner0 {
+    struct Inner1 {
+      template<ConceptT1T2<T3> T4>
+      static constexpr int constrained_method();
+    };
+  };
+};
+
+template<>
+template<ConceptT1T2<int> T5>
+constexpr int S12<int>::Inner0::Inner1::constrained_method() { return CONSTRAINED_METHOD_1; }
+
+template<>
+template<ConceptT1T2<double> T5>
+constexpr int S12<double>::Inner0::Inner1::constrained_method() { return CONSTRAINED_METHOD_2; }
+
+static_assert(S12<int>::Inner0::Inner1::constrained_method<XY>() == CONSTRAINED_METHOD_1);
+static_assert(S12<double>::Inner0::Inner1::constrained_method<XY>() == CONSTRAINED_METHOD_2);
+
+} // namespace constrained_members_of_nested_types
+
+namespace constrained_member_sfinae {
+
+template<int N> struct S {
+  template<class T>
+  static constexpr int constrained_method() requires (sizeof(int[N * 1073741824 + 4]) == 16) {
+    return CONSTRAINED_METHOD_1;
+  }
+
+  template<class T>
+  static constexpr int constrained_method() requires (sizeof(int[N]) == 16);
+};
+
+template<>
+template<typename T>
+constexpr int S<4>::constrained_method() requires (sizeof(int[4]) == 16) {
+  return CONSTRAINED_METHOD_2;
+}
+
+// Verify that there is no amiguity in this case.
+static_assert(S<4>::constrained_method<double>() == CONSTRAINED_METHOD_2);
+
+} // namespace constrained_member_sfinae
+
+namespace requires_expression_references_members {
+
+void accept1(int x);
+void accept2(XY xy);
+
+template <class T> struct S {
+  T Field = T();
+
+  constexpr int constrained_method()
+      requires requires { accept1(Field); };
+
+  constexpr int constrained_method()
+      requires requires { accept2(Field); };
+};
+
+template <class T>
+constexpr int S<T>::constrained_method()
+  requires requires { accept1(Field); } {
+  return CONSTRAINED_METHOD_1;
+}
+
+template <class T>
+constexpr int S<T>::constrained_method()
+  requires requires { accept2(Field); } {
+  return CONSTRAINED_METHOD_2;
+}
+
+static_assert(S<int>().constrained_method() == CONSTRAINED_METHOD_1);
+static_assert(S<XY>().constrained_method() == CONSTRAINED_METHOD_2);
+
+} // namespace requires_expression_references_members
+
+namespace GH60231 {
+
+template<typename T0> concept C = true;
+
+template <typename T1>
+struct S {
+  template <typename F1> requires C<S<T1>>
+  void foo1(F1 f);
+
+  template <typename F2>
+  void foo2(F2 f) requires C<S<T1>>;
+
+  template <typename F3> requires C<F3>
+  void foo3(F3 f);
+};
+
+template <typename T2>
+template <typename F4> requires C<S<T2>>
+void S<T2>::foo1(F4 f) {}
+
+template <typename T3>
+template <typename F5>
+void S<T3>::foo2(F5 f) requires C<S<T3>> {}
+
+template <typename T4>
+template <typename F6> requires C<F6>
+void S<T4>::foo3(F6 f) {}
+
+} // namespace GH60231
+
+namespace GH62003 {
+
+template <typename T0> concept Concept = true;
+
+template <class T1>
+struct S1 {
+  template <Concept C1>
+  static constexpr int foo();
+};
+template <class T2>
+template <Concept C2>
+constexpr int S1<T2>::foo() { return 1; }
+
+template <Concept C3>
+struct S2 {
+  template <class T3>
+  static constexpr int foo();
+};
+template <Concept C4>
+template <class T4>
+constexpr int S2<C4>::foo() { return 2; }
+
+template <Concept C5>
+struct S3 {
+  template <Concept C6>
+  static constexpr int foo();
+};
+template <Concept C7>
+template <Concept C8>
+constexpr int S3<C7>::foo() { return 3; }
+
+static_assert(S1<int>::foo<int>() == 1);
+static_assert(S2<int>::foo<int>() == 2);
+static_assert(S3<int>::foo<int>() == 3);
+
+} // namespace GH62003
+
+namespace MultilevelTemplateWithPartialSpecialization {
+template <typename>
+concept Concept = true;
+
+namespace two_level {
+template <typename T1, int>
+struct W0 {
+  template <typename T2>
+  requires (Concept<T2>)
+  void f(const T2 &);
+};
+
+template <typename T3>
+struct W0<T3, 0> {
+  template <typename T4>
+  requires (Concept<T4>)
+  void f(const T4 &);
+};
+
+template <typename T3>
+template <typename T4>
+requires (Concept<T4>)
+inline void W0<T3, 0>::f(const T4 &) {}
+} // namespace two_level
+
+namespace three_level {
+template <typename T1, int>
+struct W0 {
+  template <typename T2>
+  struct W1 {
+    template <typename T3>
+    requires (Concept<T3>)
+    void f(const T3 &);
+  };
+};
+
+template <typename T4>
+struct W0<T4, 0> {
+  template <typename T5>
+  struct W1 {
+    template <typename T6>
+    requires (Concept<T6>)
+    void f(const T6 &);
+  };
+};
+
+template <typename T7>
+template <typename T8>
+template <typename T9>
+requires (Concept<T9>)
+inline void W0<T7, 0>::W1<T8>::f(const T9 &) {}
+} // namespace three_level
+
+} // namespace MultilevelTemplateWithPartialSpecialization
diff --git a/clang/test/SemaTemplate/concepts.cpp b/clang/test/SemaTemplate/concepts.cpp
index d348e7a7efaf9..c6fb5c441abd6 100644
--- a/clang/test/SemaTemplate/concepts.cpp
+++ b/clang/test/SemaTemplate/concepts.cpp
@@ -816,3 +816,101 @@ static_assert(Parent<int>::TakesBinary<int, 0>::i == 0);
 static_assert(Parent<int>::TakesBinary<int, 0ULL>::i == 0);
 }
 
+namespace TemplateInsideNonTemplateClass {
+template<typename T, typename U> concept C = true;
+
+template<typename T> auto L = []<C<T> U>() {};
+
+struct Q {
+  template<C<int> U> friend constexpr auto decltype(L<int>)::operator()() const;
+};
+
+template <class T>
+concept C1 = false;
+
+struct Foo {
+  template <typename>
+  struct Bar {};
+
+  template <typename T>
+    requires(C1<T>)
+  struct Bar<T>;
+};
+
+Foo::Bar<int> BarInstance;
+} // namespace TemplateInsideNonTemplateClass
+
+namespace GH61959 {
+template <typename T0>
+concept C = (sizeof(T0) >= 4);
+
+template<typename...>
+struct Orig { };
+
+template<typename T>
+struct Orig<T> {
+  template<typename> requires C<T>
+  void f() { }
+
+  template<typename> requires true
+  void f() { }
+};
+
+template <typename...> struct Mod {};
+
+template <typename T1, typename T2>
+struct Mod<T1, T2> {
+  template <typename> requires C<T1>
+  constexpr static int f() { return 1; }
+
+  template <typename> requires C<T2>
+  constexpr static int f() { return 2; }
+};
+
+static_assert(Mod<int, char>::f<double>() == 1);
+static_assert(Mod<char, int>::f<double>() == 2);
+
+template<typename T>
+struct Outer {
+  template<typename ...>
+  struct Inner {};
+
+  template<typename U>
+  struct Inner<U> {
+    template<typename V>
+    void foo()  requires C<U> && C<T> && C<V>{}
+    template<typename V>
+    void foo()  requires true{}
+  };
+};
+
+void bar() {
+  Outer<int>::Inner<float> I;
+  I.foo<char>();
+}
+} // namespace GH61959
+
+
+namespace TemplateInsideTemplateInsideTemplate {
+template<typename T>
+concept C1 = false;
+
+template <unsigned I0>
+struct W0 {
+  template <unsigned I1>
+  struct W1 {
+    template <typename T>
+    struct F {
+      enum { value = 1 };
+    };
+
+    template <typename T>
+      requires C1<T>
+    struct F<T> {
+      enum { value = 2 };
+    };
+  };
+};
+
+static_assert(W0<0>::W1<1>::F<int>::value == 1);
+} // TemplateInsideTemplateInsideTemplate