diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -4763,7 +4763,7 @@
     bool isMoveEligible() const { return S != None; };
     bool isCopyElidable() const { return S == MoveEligibleAndCopyElidable; }
   };
-  NamedReturnInfo getNamedReturnInfo(const Expr *E, bool ForceCXX20 = false);
+  NamedReturnInfo getNamedReturnInfo(Expr *&E, bool ForceCXX2b = false);
   NamedReturnInfo getNamedReturnInfo(const VarDecl *VD,
                                      bool ForceCXX20 = false);
   const VarDecl *getCopyElisionCandidate(NamedReturnInfo &Info,
diff --git a/clang/lib/Sema/SemaCoroutine.cpp b/clang/lib/Sema/SemaCoroutine.cpp
--- a/clang/lib/Sema/SemaCoroutine.cpp
+++ b/clang/lib/Sema/SemaCoroutine.cpp
@@ -994,22 +994,10 @@
     E = R.get();
   }
 
-  // Move the return value if we can
-  NamedReturnInfo NRInfo = getNamedReturnInfo(E, /*ForceCXX20=*/true);
-  if (NRInfo.isMoveEligible()) {
-    InitializedEntity Entity = InitializedEntity::InitializeResult(
-        Loc, E->getType(), NRInfo.Candidate);
-    ExprResult MoveResult = PerformMoveOrCopyInitialization(Entity, NRInfo, E);
-    if (MoveResult.get())
-      E = MoveResult.get();
-  }
-
-  // FIXME: If the operand is a reference to a variable that's about to go out
-  // of scope, we should treat the operand as an xvalue for this overload
-  // resolution.
   VarDecl *Promise = FSI->CoroutinePromise;
   ExprResult PC;
   if (E && (isa<InitListExpr>(E) || !E->getType()->isVoidType())) {
+    getNamedReturnInfo(E, /*ForceCXX2b=*/true);
     PC = buildPromiseCall(*this, Promise, Loc, "return_value", E);
   } else {
     E = MakeFullDiscardedValueExpr(E).get();
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -854,10 +854,6 @@
     Diag(OpLoc, diag::err_omp_simd_region_cannot_use_stmt) << "throw";
 
   if (Ex && !Ex->isTypeDependent()) {
-    QualType ExceptionObjectTy = Context.getExceptionObjectType(Ex->getType());
-    if (CheckCXXThrowOperand(OpLoc, ExceptionObjectTy, Ex))
-      return ExprError();
-
     // Initialize the exception result.  This implicitly weeds out
     // abstract types or types with inaccessible copy constructors.
 
@@ -876,6 +872,10 @@
     NamedReturnInfo NRInfo =
         IsThrownVarInScope ? getNamedReturnInfo(Ex) : NamedReturnInfo();
 
+    QualType ExceptionObjectTy = Context.getExceptionObjectType(Ex->getType());
+    if (CheckCXXThrowOperand(OpLoc, ExceptionObjectTy, Ex))
+      return ExprError();
+
     InitializedEntity Entity = InitializedEntity::InitializeException(
         OpLoc, ExceptionObjectTy,
         /*NRVO=*/NRInfo.isCopyElidable());
diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp
--- a/clang/lib/Sema/SemaStmt.cpp
+++ b/clang/lib/Sema/SemaStmt.cpp
@@ -3312,15 +3312,16 @@
 /// without considering function return type, if applicable.
 ///
 /// \param E The expression being returned from the function or block,
-/// being thrown, or being co_returned from a coroutine.
+/// being thrown, or being co_returned from a coroutine. This expression
+/// might be modified by the implementation.
 ///
-/// \param ForceCXX20 Overrides detection of current language mode
-/// and uses the rules for C++20.
+/// \param ForceCXX2b Overrides detection of current language mode
+/// and uses the rules for C++2b.
 ///
 /// \returns An aggregate which contains the Candidate and isMoveEligible
 /// and isCopyElidable methods. If Candidate is non-null, it means
 /// isMoveEligible() would be true under the most permissive language standard.
-Sema::NamedReturnInfo Sema::getNamedReturnInfo(const Expr *E, bool ForceCXX20) {
+Sema::NamedReturnInfo Sema::getNamedReturnInfo(Expr *&E, bool ForceCXX2b) {
   if (!E)
     return NamedReturnInfo();
   // - in a return statement in a function [where] ...
@@ -3331,7 +3332,14 @@
   const auto *VD = dyn_cast<VarDecl>(DR->getDecl());
   if (!VD)
     return NamedReturnInfo();
-  return getNamedReturnInfo(VD, ForceCXX20);
+  NamedReturnInfo Res = getNamedReturnInfo(VD, /*ForceCXX20=*/ForceCXX2b);
+  if (Res.Candidate && !E->isXValue() &&
+      (ForceCXX2b || getLangOpts().CPlusPlus2b)) {
+    E = ImplicitCastExpr::Create(Context, VD->getType().getNonReferenceType(),
+                                 CK_NoOp, E, nullptr, VK_XValue,
+                                 FPOptionsOverride());
+  }
+  return Res;
 }
 
 /// Updates the status in the given NamedReturnInfo object to disallow
@@ -3566,7 +3574,7 @@
                                       const NamedReturnInfo &NRInfo,
                                       Expr *Value) {
 
-  if (NRInfo.Candidate) {
+  if (NRInfo.Candidate && !getLangOpts().CPlusPlus2b) {
     if (NRInfo.isMoveEligible()) {
       ExprResult Res;
       if (!TryMoveInitialization(*this, Entity, NRInfo.Candidate, Value,
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -8899,6 +8899,10 @@
   if (E->isTypeDependent())
     return S.Context.DependentTy;
 
+  Expr *IDExpr = E;
+  if (auto *ImplCastExpr = dyn_cast<ImplicitCastExpr>(E))
+    IDExpr = ImplCastExpr->getSubExpr();
+
   // C++11 [dcl.type.simple]p4:
   //   The type denoted by decltype(e) is defined as follows:
 
@@ -8909,7 +8913,7 @@
   // Note that this does not pick up the implicit 'const' for a template
   // parameter object. This rule makes no difference before C++20 so we apply
   // it unconditionally.
-  if (const auto *SNTTPE = dyn_cast<SubstNonTypeTemplateParmExpr>(E))
+  if (const auto *SNTTPE = dyn_cast<SubstNonTypeTemplateParmExpr>(IDExpr))
     return SNTTPE->getParameterType(S.Context);
 
   //     - if e is an unparenthesized id-expression or an unparenthesized class
@@ -8918,21 +8922,22 @@
   //       functions, the program is ill-formed;
   //
   // We apply the same rules for Objective-C ivar and property references.
-  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
+  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(IDExpr)) {
     const ValueDecl *VD = DRE->getDecl();
     if (auto *TPO = dyn_cast<TemplateParamObjectDecl>(VD))
       return TPO->getType().getUnqualifiedType();
     return VD->getType();
-  } else if (const MemberExpr *ME = dyn_cast<MemberExpr>(E)) {
+  } else if (const MemberExpr *ME = dyn_cast<MemberExpr>(IDExpr)) {
     if (const ValueDecl *VD = ME->getMemberDecl())
       if (isa<FieldDecl>(VD) || isa<VarDecl>(VD))
         return VD->getType();
-  } else if (const ObjCIvarRefExpr *IR = dyn_cast<ObjCIvarRefExpr>(E)) {
+  } else if (const ObjCIvarRefExpr *IR = dyn_cast<ObjCIvarRefExpr>(IDExpr)) {
     return IR->getDecl()->getType();
-  } else if (const ObjCPropertyRefExpr *PR = dyn_cast<ObjCPropertyRefExpr>(E)) {
+  } else if (const ObjCPropertyRefExpr *PR =
+                 dyn_cast<ObjCPropertyRefExpr>(IDExpr)) {
     if (PR->isExplicitProperty())
       return PR->getExplicitProperty()->getType();
-  } else if (auto *PE = dyn_cast<PredefinedExpr>(E)) {
+  } else if (auto *PE = dyn_cast<PredefinedExpr>(IDExpr)) {
     return PE->getType();
   }
 
@@ -8945,8 +8950,8 @@
   //   entity.
   using namespace sema;
   if (S.getCurLambda()) {
-    if (isa<ParenExpr>(E)) {
-      if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E->IgnoreParens())) {
+    if (isa<ParenExpr>(IDExpr)) {
+      if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(IDExpr->IgnoreParens())) {
         if (VarDecl *Var = dyn_cast<VarDecl>(DRE->getDecl())) {
           QualType T = S.getCapturedDeclRefType(Var, DRE->getLocation());
           if (!T.isNull())
diff --git a/clang/test/CXX/class/class.init/class.copy.elision/p3.cpp b/clang/test/CXX/class/class.init/class.copy.elision/p3.cpp
--- a/clang/test/CXX/class/class.init/class.copy.elision/p3.cpp
+++ b/clang/test/CXX/class/class.init/class.copy.elision/p3.cpp
@@ -1,8 +1,8 @@
-// RUN: %clang_cc1 -std=c++2b -fsyntax-only -fcxx-exceptions -verify=expected,cxx20_2b %s
-// RUN: %clang_cc1 -std=c++20 -fsyntax-only -fcxx-exceptions -verify=expected,cxx20_2b %s
-// RUN: %clang_cc1 -std=c++17 -fsyntax-only -fcxx-exceptions -verify=expected,cxx11_17 %s
-// RUN: %clang_cc1 -std=c++14 -fsyntax-only -fcxx-exceptions -verify=expected,cxx11_17 %s
-// RUN: %clang_cc1 -std=c++11 -fsyntax-only -fcxx-exceptions -verify=expected,cxx11_17 %s
+// RUN: %clang_cc1 -std=c++2b -fsyntax-only -fcxx-exceptions -verify=expected,cxx20_2b,cxx2b %s
+// RUN: %clang_cc1 -std=c++20 -fsyntax-only -fcxx-exceptions -verify=expected,cxx11_20,cxx20_2b %s
+// RUN: %clang_cc1 -std=c++17 -fsyntax-only -fcxx-exceptions -verify=expected,cxx11_17,cxx11_20 %s
+// RUN: %clang_cc1 -std=c++14 -fsyntax-only -fcxx-exceptions -verify=expected,cxx11_17,cxx11_20 %s
+// RUN: %clang_cc1 -std=c++11 -fsyntax-only -fcxx-exceptions -verify=expected,cxx11_17,cxx11_20 %s
 
 namespace test_delete_function {
 struct A1 {
@@ -409,8 +409,10 @@
 namespace test_simpler_implicit_move {
 
 struct CopyOnly {
-  CopyOnly();
-  CopyOnly(CopyOnly &);
+  CopyOnly(); // cxx2b-note {{candidate constructor not viable: requires 0 arguments, but 1 was provided}}
+  // cxx2b-note@-1 {{candidate constructor not viable: requires 0 arguments, but 1 was provided}}
+  CopyOnly(CopyOnly &); // cxx2b-note {{candidate constructor not viable: expects an lvalue for 1st argument}}
+  // cxx2b-note@-1 {{candidate constructor not viable: expects an lvalue for 1st argument}}
 };
 struct MoveOnly {
   MoveOnly();
@@ -419,7 +421,7 @@
 MoveOnly &&rref();
 
 MoveOnly &&test1(MoveOnly &&w) {
-  return w; // expected-error {{cannot bind to lvalue of type}}
+  return w; // cxx11_20-error {{cannot bind to lvalue of type}}
 }
 
 CopyOnly test2(bool b) {
@@ -428,22 +430,22 @@
   if (b) {
     return w1;
   } else {
-    return w2;
+    return w2; // cxx2b-error {{no matching constructor for initialization}}
   }
 }
 
-template <class T> T &&test3(T &&x) { return x; } // expected-error {{cannot bind to lvalue of type}}
+template <class T> T &&test3(T &&x) { return x; } // cxx11_20-error {{cannot bind to lvalue of type}}
 template MoveOnly& test3<MoveOnly&>(MoveOnly&);
-template MoveOnly&& test3<MoveOnly>(MoveOnly&&); // expected-note {{in instantiation of function template specialization}}
+template MoveOnly &&test3<MoveOnly>(MoveOnly &&); // cxx11_20-note {{in instantiation of function template specialization}}
 
 MoveOnly &&test4() {
   MoveOnly &&x = rref();
-  return x; // expected-error {{cannot bind to lvalue of type}}
+  return x; // cxx11_20-error {{cannot bind to lvalue of type}}
 }
 
 void test5() try {
   CopyOnly x;
-  throw x;
+  throw x; // cxx2b-error {{no matching constructor for initialization}}
 } catch (...) {
 }
 
diff --git a/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p7-cxx14.cpp b/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p7-cxx14.cpp
--- a/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p7-cxx14.cpp
+++ b/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p7-cxx14.cpp
@@ -1,6 +1,6 @@
-// RUN: %clang_cc1 -verify -std=c++2b -verify %s
-// RUN: %clang_cc1 -verify -std=c++20 -verify %s
-// RUN: %clang_cc1 -verify -std=c++14 -verify %s
+// RUN: %clang_cc1 -verify -std=c++2b -verify=expected,cxx2b    %s
+// RUN: %clang_cc1 -verify -std=c++20 -verify=expected,cxx14_20 %s
+// RUN: %clang_cc1 -verify -std=c++14 -verify=expected,cxx14_20 %s
 
 namespace std {
   template<typename T> struct initializer_list {
@@ -30,7 +30,7 @@
 auto x4a = (i);
 decltype(auto) x4d = (i);
 using Int = decltype(x4a);
-using IntLRef = decltype(x4d);
+using IntLRef = decltype(x4d); // cxx2b-note {{previous definition is here}}
 
 auto x5a = f();
 decltype(auto) x5d = f();
@@ -81,7 +81,7 @@
 auto f3a(int n) { return (n); }
 decltype(auto) f3d(int n) { return (n); } // expected-warning {{reference to stack memory}}
 using Int = decltype(f3a(0));
-using IntLRef = decltype(f3d(0));
+using IntLRef = decltype(f3d(0)); // cxx2b-error {{type alias redefinition with different types ('decltype(f3d(0))' (aka 'int &&') vs 'decltype(x4d)' (aka 'int &'))}}
 
 auto f4a(int n) { return f(); }
 decltype(auto) f4d(int n) { return f(); }
@@ -91,7 +91,7 @@
 auto f5aa(int n) { auto x = f(); return x; }
 auto f5ad(int n) { decltype(auto) x = f(); return x; }
 decltype(auto) f5da(int n) { auto x = f(); return x; }
-decltype(auto) f5dd(int n) { decltype(auto) x = f(); return x; } // expected-error {{rvalue reference to type 'int' cannot bind to lvalue}}
+decltype(auto) f5dd(int n) { decltype(auto) x = f(); return x; } // cxx14_20-error {{rvalue reference to type 'int' cannot bind to lvalue}}
 using Int = decltype(f5aa(0));
 using Int = decltype(f5ad(0));
 using Int = decltype(f5da(0));
diff --git a/clang/test/CXX/drs/dr3xx.cpp b/clang/test/CXX/drs/dr3xx.cpp
--- a/clang/test/CXX/drs/dr3xx.cpp
+++ b/clang/test/CXX/drs/dr3xx.cpp
@@ -1,9 +1,9 @@
-// RUN: %clang_cc1 -std=c++2b -verify=expected,cxx20_2b -triple %itanium_abi_triple %s -fexceptions -fcxx-exceptions -pedantic-errors
-// RUN: %clang_cc1 -std=c++20 -verify=expected,cxx20_2b -triple %itanium_abi_triple %s -fexceptions -fcxx-exceptions -pedantic-errors
-// RUN: %clang_cc1 -std=c++17 -verify=expected,cxx98_17 -triple %itanium_abi_triple %s -fexceptions -fcxx-exceptions -pedantic-errors
-// RUN: %clang_cc1 -std=c++14 -verify=expected,cxx98_17 -triple %itanium_abi_triple %s -fexceptions -fcxx-exceptions -pedantic-errors
-// RUN: %clang_cc1 -std=c++11 -verify=expected,cxx98_17 -triple %itanium_abi_triple %s -fexceptions -fcxx-exceptions -pedantic-errors
-// RUN: %clang_cc1 -std=c++98 -verify=expected,cxx98_17 -triple %itanium_abi_triple %s -fexceptions -fcxx-exceptions -pedantic-errors
+// RUN: %clang_cc1 -std=c++2b -verify=expected,cxx20_2b,cxx2b    -triple %itanium_abi_triple %s -fexceptions -fcxx-exceptions -pedantic-errors
+// RUN: %clang_cc1 -std=c++20 -verify=expected,cxx98_20,cxx20_2b -triple %itanium_abi_triple %s -fexceptions -fcxx-exceptions -pedantic-errors
+// RUN: %clang_cc1 -std=c++17 -verify=expected,cxx98_17,cxx98_20 -triple %itanium_abi_triple %s -fexceptions -fcxx-exceptions -pedantic-errors
+// RUN: %clang_cc1 -std=c++14 -verify=expected,cxx98_17,cxx98_20 -triple %itanium_abi_triple %s -fexceptions -fcxx-exceptions -pedantic-errors
+// RUN: %clang_cc1 -std=c++11 -verify=expected,cxx98_17,cxx98_20 -triple %itanium_abi_triple %s -fexceptions -fcxx-exceptions -pedantic-errors
+// RUN: %clang_cc1 -std=c++98 -verify=expected,cxx98_17,cxx98_20 -triple %itanium_abi_triple %s -fexceptions -fcxx-exceptions -pedantic-errors
 
 namespace dr300 { // dr300: yes
   template<typename R, typename A> void f(R (&)(A)) {}
@@ -628,7 +628,8 @@
   struct A {
     template <class T> operator T ***() {
       int ***p = 0;
-      return p; // expected-error {{cannot initialize return object of type 'const int ***' with an lvalue of type 'int ***'}}
+      return p; // cxx98_20-error {{cannot initialize return object of type 'const int ***' with an lvalue of type 'int ***'}}
+      // cxx2b-error@-1 {{cannot initialize return object of type 'const int ***' with an rvalue of type 'int ***'}}
     }
   };
 
diff --git a/clang/test/CXX/expr/expr.prim/expr.prim.lambda/p4-cxx14.cpp b/clang/test/CXX/expr/expr.prim/expr.prim.lambda/p4-cxx14.cpp
--- a/clang/test/CXX/expr/expr.prim/expr.prim.lambda/p4-cxx14.cpp
+++ b/clang/test/CXX/expr/expr.prim/expr.prim.lambda/p4-cxx14.cpp
@@ -1,6 +1,6 @@
-// RUN: %clang_cc1 -std=c++2b -fsyntax-only -verify %s
-// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify %s
-// RUN: %clang_cc1 -std=c++14 -fsyntax-only -verify %s
+// RUN: %clang_cc1 -std=c++2b -fsyntax-only -verify=expected,cxx2b    %s
+// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify=expected,cxx14_20 %s
+// RUN: %clang_cc1 -std=c++14 -fsyntax-only -verify=expected,cxx14_20 %s
 
 int a;
 int &b = [] (int &r) -> decltype(auto) { return r; } (a);
@@ -9,13 +9,15 @@
 int &e = [] (int &r) -> auto { return r; } (a); // expected-error {{cannot bind to a temporary}}
 int &f = [] (int r) -> decltype(auto) { return r; } (a); // expected-error {{cannot bind to a temporary}}
 int &g = [] (int r) -> decltype(auto) { return (r); } (a); // expected-warning {{reference to stack}}
+// cxx2b-error@-1 {{non-const lvalue reference to type 'int' cannot bind to a temporary of type 'int'}}
 
 int test_explicit_auto_return()
 {
     struct X {};
     auto L = [](auto F, auto a) { return F(a); };
     auto M = [](auto a) -> auto { return a; }; // OK
-    auto MRef = [](auto b) -> auto& { return b; }; //expected-warning{{reference to stack}}
+    auto MRef = [](auto b) -> auto & { return b; }; //cxx14_20-warning{{reference to stack}}
+    // cxx2b-error@-1 {{non-const lvalue reference to type 'X' cannot bind to a temporary of type 'X'}}
     auto MPtr = [](auto c) -> auto* { return &c; }; //expected-warning{{address of stack}}
     auto MDeclType = [](auto&& d) -> decltype(auto) { return static_cast<decltype(d)>(d); }; //OK
     M(3);
diff --git a/clang/test/CXX/temp/temp.decls/temp.mem/p5.cpp b/clang/test/CXX/temp/temp.decls/temp.mem/p5.cpp
--- a/clang/test/CXX/temp/temp.decls/temp.mem/p5.cpp
+++ b/clang/test/CXX/temp/temp.decls/temp.mem/p5.cpp
@@ -1,7 +1,7 @@
-// RUN: %clang_cc1 -std=c++2b -fsyntax-only -verify %s
-// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify %s
-// RUN: %clang_cc1 -std=c++98 -fsyntax-only -verify %s
-// RUN: %clang_cc1            -fsyntax-only -verify %s
+// RUN: %clang_cc1 -std=c++2b -fsyntax-only -verify=expected,cxx2b    %s
+// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify=expected,cxx98_20 %s
+// RUN: %clang_cc1 -std=c++98 -fsyntax-only -verify=expected,cxx98_20 %s
+// RUN: %clang_cc1            -fsyntax-only -verify=expected,cxx98_20 %s
 
 struct A {
   template <class T> operator T*();
@@ -67,8 +67,10 @@
 
   template<typename T> operator const T*() const {
     T x = T();
-    return x; // expected-error{{cannot initialize return object of type 'const char *' with an lvalue of type 'char'}} \
-    // expected-error{{cannot initialize return object of type 'const int *' with an lvalue of type 'int'}}
+    return x; // cxx98_20-error{{cannot initialize return object of type 'const char *' with an lvalue of type 'char'}} \
+    // cxx98_20-error{{cannot initialize return object of type 'const int *' with an lvalue of type 'int'}} \
+    // cxx2b-error{{cannot initialize return object of type 'const char *' with an rvalue of type 'char'}} \
+    // cxx2b-error{{cannot initialize return object of type 'const int *' with an rvalue of type 'int'}}
   }
 };
 
diff --git a/clang/test/SemaCXX/constant-expression-cxx11.cpp b/clang/test/SemaCXX/constant-expression-cxx11.cpp
--- a/clang/test/SemaCXX/constant-expression-cxx11.cpp
+++ b/clang/test/SemaCXX/constant-expression-cxx11.cpp
@@ -1,6 +1,6 @@
-// RUN: %clang_cc1 -std=c++2b -fsyntax-only -verify=expected,cxx20_2b -triple x86_64-linux -Wno-string-plus-int -Wno-pointer-arith -Wno-zero-length-array -Wno-c99-designator -fcxx-exceptions -pedantic %s -Wno-comment -Wno-tautological-pointer-compare -Wno-bool-conversion
-// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify=expected,cxx20_2b -triple x86_64-linux -Wno-string-plus-int -Wno-pointer-arith -Wno-zero-length-array -Wno-c99-designator -fcxx-exceptions -pedantic %s -Wno-comment -Wno-tautological-pointer-compare -Wno-bool-conversion
-// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify=expected,cxx11 -triple x86_64-linux -Wno-string-plus-int -Wno-pointer-arith -Wno-zero-length-array -Wno-c99-designator -fcxx-exceptions -pedantic %s -Wno-comment -Wno-tautological-pointer-compare -Wno-bool-conversion
+// RUN: %clang_cc1 -std=c++2b -fsyntax-only -verify=expected,cxx20_2b,cxx2b    -triple x86_64-linux -Wno-string-plus-int -Wno-pointer-arith -Wno-zero-length-array -Wno-c99-designator -fcxx-exceptions -pedantic %s -Wno-comment -Wno-tautological-pointer-compare -Wno-bool-conversion
+// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify=expected,cxx11_20,cxx20_2b -triple x86_64-linux -Wno-string-plus-int -Wno-pointer-arith -Wno-zero-length-array -Wno-c99-designator -fcxx-exceptions -pedantic %s -Wno-comment -Wno-tautological-pointer-compare -Wno-bool-conversion
+// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify=expected,cxx11_20,cxx11    -triple x86_64-linux -Wno-string-plus-int -Wno-pointer-arith -Wno-zero-length-array -Wno-c99-designator -fcxx-exceptions -pedantic %s -Wno-comment -Wno-tautological-pointer-compare -Wno-bool-conversion
 
 namespace StaticAssertFoldTest {
 
@@ -1938,13 +1938,18 @@
   }
 
   constexpr int &get(int &&n) { return n; }
+  // cxx2b-error@-1 {{non-const lvalue reference to type 'int' cannot bind to a temporary of type 'int'}}
+  // cxx2b-error@-2 {{no return statement in constexpr function}} See PR40598
   constexpr int &&get_rv(int &&n) { return static_cast<int&&>(n); }
   struct S {
     int &&r;
     int &s;
     int t;
     constexpr S() : r(get_rv(0)), s(get(0)), t(r) {} // expected-note {{read of object outside its lifetime}}
-    constexpr S(int) : r(get_rv(0)), s(get(0)), t(s) {} // expected-note {{read of object outside its lifetime}}
+    constexpr S(int) : r(get_rv(0)), s(get(0)), t(s) {}
+    // cxx2b-warning@-1 {{reference 's' is not yet bound to a value when used here}}
+    // cxx2b-note@-2    {{read of uninitialized object is not allowed in a constant expression}}
+    // cxx11_20-note@-3 {{read of object outside its lifetime}}
   };
   constexpr int k1 = S().t; // expected-error {{constant expression}} expected-note {{in call}}
   constexpr int k2 = S(0).t; // expected-error {{constant expression}} expected-note {{in call}}
diff --git a/clang/test/SemaCXX/constant-expression-cxx14.cpp b/clang/test/SemaCXX/constant-expression-cxx14.cpp
--- a/clang/test/SemaCXX/constant-expression-cxx14.cpp
+++ b/clang/test/SemaCXX/constant-expression-cxx14.cpp
@@ -1,6 +1,6 @@
-// RUN: %clang_cc1 -std=c++2b -fsyntax-only -verify=expected,cxx20_2b %s -fcxx-exceptions -triple=x86_64-linux-gnu
-// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify=expected,cxx20_2b %s -fcxx-exceptions -triple=x86_64-linux-gnu
-// RUN: %clang_cc1 -std=c++14 -fsyntax-only -verify=expected,cxx14    %s -fcxx-exceptions -triple=x86_64-linux-gnu
+// RUN: %clang_cc1 -std=c++2b -fsyntax-only -verify=expected,cxx20_2b,cxx2b          %s -fcxx-exceptions -triple=x86_64-linux-gnu
+// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify=expected,cxx14_20,cxx20_2b,cxx20 %s -fcxx-exceptions -triple=x86_64-linux-gnu
+// RUN: %clang_cc1 -std=c++14 -fsyntax-only -verify=expected,cxx14_20,cxx14          %s -fcxx-exceptions -triple=x86_64-linux-gnu
 
 struct S {
   // dummy ctor to make this a literal type
@@ -269,16 +269,23 @@
 
 namespace incdec {
   template<typename T> constexpr T &ref(T &&r) { return r; }
+  // cxx2b-error@-1 {{non-const lvalue reference to type 'int' cannot bind to a temporary of type 'int'}}
   template<typename T> constexpr T postinc(T &&r) { return (r++, r); }
   template<typename T> constexpr T postdec(T &&r) { return (r--, r); }
 
+  template int &ref<int>(int &&);
+  // cxx2b-note@-1  {{in instantiation of function template specialization}}
+
+  static_assert(postinc(0) == 1, "");
+  static_assert(postdec(0) == -1, "");
+#if __cplusplus <= 202002L
   static_assert(++ref(0) == 1, "");
   static_assert(ref(0)++ == 0, "");
-  static_assert(postinc(0) == 1, "");
   static_assert(--ref(0) == -1, "");
   static_assert(ref(0)-- == 0, "");
-  static_assert(postdec(0) == -1, "");
+#endif
 
+#if __cplusplus <= 202002L
   constexpr int overflow_int_inc_1 = ref(0x7fffffff)++; // expected-error {{constant}} expected-note {{2147483648}}
   constexpr int overflow_int_inc_1_ok = ref(0x7ffffffe)++;
   constexpr int overflow_int_inc_2 = ++ref(0x7fffffff); // expected-error {{constant}} expected-note {{2147483648}}
@@ -291,37 +298,42 @@
   // inc on bool sets to true
   static_assert(++ref(false), "");
   // cxx14-warning@-1  {{incrementing expression of type bool}}
-  // cxx20_2b-error@-2 {{incrementing expression of type bool}}
+  // cxx20-error@-2 {{incrementing expression of type bool}}
   static_assert(++ref(true), "");
   // cxx14-warning@-1  {{incrementing expression of type bool}}
-  // cxx20_2b-error@-2 {{incrementing expression of type bool}}
+  // cxx20-error@-2 {{incrementing expression of type bool}}
+#endif
 
   int arr[10];
+  static_assert(postinc(&arr[0]) == &arr[1], "");
+  static_assert(postdec(&arr[1]) == &arr[0], "");
+#if __cplusplus <= 202002L
   static_assert(++ref(&arr[0]) == &arr[1], "");
   static_assert(++ref(&arr[9]) == &arr[10], "");
   static_assert(++ref(&arr[10]) == &arr[11], ""); // expected-error {{constant}} expected-note {{cannot refer to element 11}}
   static_assert(ref(&arr[0])++ == &arr[0], "");
   static_assert(ref(&arr[10])++ == &arr[10], ""); // expected-error {{constant}} expected-note {{cannot refer to element 11}}
-  static_assert(postinc(&arr[0]) == &arr[1], "");
   static_assert(--ref(&arr[10]) == &arr[9], "");
   static_assert(--ref(&arr[1]) == &arr[0], "");
   static_assert(--ref(&arr[0]) != &arr[0], ""); // expected-error {{constant}} expected-note {{cannot refer to element -1}}
   static_assert(ref(&arr[1])-- == &arr[1], "");
   static_assert(ref(&arr[0])-- == &arr[0], ""); // expected-error {{constant}} expected-note {{cannot refer to element -1}}
-  static_assert(postdec(&arr[1]) == &arr[0], "");
+#endif
 
+  static_assert(postinc(0.0) == 1.0, "");
+  static_assert(postdec(0.0) == -1.0, "");
+#if __cplusplus <= 202002L
   int x;
   static_assert(++ref(&x) == &x + 1, "");
 
   static_assert(++ref(0.0) == 1.0, "");
   static_assert(ref(0.0)++ == 0.0, "");
-  static_assert(postinc(0.0) == 1.0, "");
   static_assert(--ref(0.0) == -1.0, "");
   static_assert(ref(0.0)-- == 0.0, "");
-  static_assert(postdec(0.0) == -1.0, "");
 
   static_assert(++ref(1e100) == 1e100, "");
   static_assert(--ref(1e100) == 1e100, "");
+#endif
 
   union U {
     int a, b;
@@ -863,9 +875,13 @@
 
 namespace Lifetime {
   constexpr int &get(int &&r) { return r; }
+  // cxx2b-error@-1 {{non-const lvalue reference to type 'int' cannot bind to a temporary of type 'int'}}
+  // cxx2b-error@-2 {{no return statement in constexpr function}} See PR40598
   constexpr int f() {
     int &r = get(123);
-    return r; // expected-note {{read of object outside its lifetime}}
+    return r;
+    // cxx2b-note@-1 {{use of reference outside its lifetime is not allowed in a constant expression}}
+    // cxx14_20-note@-2 {{read of object outside its lifetime}}
   }
   static_assert(f() == 123, ""); // expected-error {{constant expression}} expected-note {{in call}}
 
diff --git a/clang/test/SemaCXX/coroutine-rvo.cpp b/clang/test/SemaCXX/coroutine-rvo.cpp
--- a/clang/test/SemaCXX/coroutine-rvo.cpp
+++ b/clang/test/SemaCXX/coroutine-rvo.cpp
@@ -39,15 +39,14 @@
 };
 
 struct MoveOnly {
-  MoveOnly() {};
+  MoveOnly() = default;
   MoveOnly(const MoveOnly&) = delete;
-  MoveOnly(MoveOnly&&) noexcept {};
-  ~MoveOnly() {};
+  MoveOnly(MoveOnly &&) = default;
 };
 
 struct NoCopyNoMove {
   NoCopyNoMove() = default;
-  NoCopyNoMove(const NoCopyNoMove &) = delete; // expected-note 4{{'NoCopyNoMove' has been explicitly marked deleted here}}
+  NoCopyNoMove(const NoCopyNoMove &) = delete;
 };
 
 template <typename T>
@@ -63,13 +62,12 @@
 
 task<NoCopyNoMove> local2val() {
   NoCopyNoMove value;
-  co_return value; // expected-error {{call to deleted constructor of 'NoCopyNoMove'}}
-  // expected-error@-1 {{value reference to type 'NoCopyNoMove' cannot bind to lvalue of type 'NoCopyNoMove'}}
+  co_return value;
 }
 
 task<NoCopyNoMove &> local2ref() {
   NoCopyNoMove value;
-  co_return value; // expected-error {{call to deleted constructor of 'NoCopyNoMove'}}
+  co_return value; // expected-error {{non-const lvalue reference to type 'NoCopyNoMove' cannot bind to a temporary of type 'NoCopyNoMove'}}
 }
 
 // We need the move constructor for construction of the coroutine.
@@ -82,8 +80,7 @@
 }
 
 task<NoCopyNoMove> rvalue2val(NoCopyNoMove &&value) {
-  co_return value; // expected-error {{rvalue reference to type 'NoCopyNoMove' cannot bind to lvalue of type 'NoCopyNoMove'}}
-  // expected-error@-1 {{call to deleted constructor of 'NoCopyNoMove'}}
+  co_return value;
 }
 
 task<NoCopyNoMove &> lvalue2ref(NoCopyNoMove &value) {
@@ -91,7 +88,7 @@
 }
 
 task<NoCopyNoMove &> rvalue2ref(NoCopyNoMove &&value) {
-  co_return value; // expected-error {{call to deleted constructor of 'NoCopyNoMove'}}
+  co_return value; // expected-error {{non-const lvalue reference to type 'NoCopyNoMove' cannot bind to a temporary of type 'NoCopyNoMove'}}
 }
 
 struct To {
diff --git a/clang/test/SemaCXX/coroutines.cpp b/clang/test/SemaCXX/coroutines.cpp
--- a/clang/test/SemaCXX/coroutines.cpp
+++ b/clang/test/SemaCXX/coroutines.cpp
@@ -1,9 +1,9 @@
 // This file contains references to sections of the Coroutines TS, which can be
 // found at http://wg21.link/coroutines.
 
-// RUN: %clang_cc1 -std=c++2b                 -fsyntax-only -verify=expected,cxx20_2b %s -fcxx-exceptions -fexceptions -Wunused-result
-// RUN: %clang_cc1 -std=c++20                 -fsyntax-only -verify=expected,cxx20_2b %s -fcxx-exceptions -fexceptions -Wunused-result
-// RUN: %clang_cc1 -std=c++14 -fcoroutines-ts -fsyntax-only -verify=expected          %s -fcxx-exceptions -fexceptions -Wunused-result
+// RUN: %clang_cc1 -std=c++2b                 -fsyntax-only -verify=expected,cxx20_2b,cxx2b    %s -fcxx-exceptions -fexceptions -Wunused-result
+// RUN: %clang_cc1 -std=c++20                 -fsyntax-only -verify=expected,cxx14_20,cxx20_2b %s -fcxx-exceptions -fexceptions -Wunused-result
+// RUN: %clang_cc1 -std=c++14 -fcoroutines-ts -fsyntax-only -verify=expected,cxx14_20          %s -fcxx-exceptions -fexceptions -Wunused-result
 
 void no_coroutine_traits_bad_arg_await() {
   co_await a; // expected-error {{include <experimental/coroutine>}}
@@ -934,7 +934,8 @@
 };
 
 extern "C" int f(mismatch_gro_type_tag2) {
-  // expected-error@-1 {{cannot initialize return object of type 'int' with an lvalue of type 'void *'}}
+  // cxx2b-error@-1 {{cannot initialize return object of type 'int' with an rvalue of type 'void *'}}
+  // cxx14_20-error@-2 {{cannot initialize return object of type 'int' with an lvalue of type 'void *'}}
   co_return; //expected-note {{function is a coroutine due to use of 'co_return' here}}
 }
 
diff --git a/clang/test/SemaCXX/deduced-return-type-cxx14.cpp b/clang/test/SemaCXX/deduced-return-type-cxx14.cpp
--- a/clang/test/SemaCXX/deduced-return-type-cxx14.cpp
+++ b/clang/test/SemaCXX/deduced-return-type-cxx14.cpp
@@ -1,11 +1,11 @@
-// RUN: %clang_cc1 -std=c++2b -fsyntax-only -verify=expected,cxx20_2b %s
-// RUN: %clang_cc1 -std=c++2b -fsyntax-only -verify=expected,cxx20_2b %s -fdelayed-template-parsing -DDELAYED_TEMPLATE_PARSING
+// RUN: %clang_cc1 -std=c++2b -fsyntax-only -verify=expected,cxx20_2b,cxx2b    %s
+// RUN: %clang_cc1 -std=c++2b -fsyntax-only -verify=expected,cxx20_2b,cxx2b    %s -fdelayed-template-parsing -DDELAYED_TEMPLATE_PARSING
 
-// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify=expected,cxx20_2b %s
-// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify=expected,cxx20_2b %s -fdelayed-template-parsing -DDELAYED_TEMPLATE_PARSING
+// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify=expected,cxx14_20,cxx20_2b %s
+// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify=expected,cxx14_20,cxx20_2b %s -fdelayed-template-parsing -DDELAYED_TEMPLATE_PARSING
 
-// RUN: %clang_cc1 -std=c++14 -fsyntax-only -verify=expected,cxx14    %s
-// RUN: %clang_cc1 -std=c++14 -fsyntax-only -verify=expected,cxx14    %s -fdelayed-template-parsing -DDELAYED_TEMPLATE_PARSING
+// RUN: %clang_cc1 -std=c++14 -fsyntax-only -verify=expected,cxx14_20,cxx14    %s
+// RUN: %clang_cc1 -std=c++14 -fsyntax-only -verify=expected,cxx14_20,cxx14    %s -fdelayed-template-parsing -DDELAYED_TEMPLATE_PARSING
 
 auto f(); // expected-note {{previous}}
 int f(); // expected-error {{differ only in their return type}}
@@ -129,10 +129,14 @@
     return T() + 1;
   }
   template<typename T> auto &f2(T &&v) { return v; }
+  // cxx2b-error@-1 {{non-const lvalue reference to type 'int' cannot bind to a temporary of type 'int'}}
+  // cxx2b-error@-2 {{non-const lvalue reference to type 'double' cannot bind to a temporary of type 'double'}}
+  // cxx2b-note@-3  {{candidate template ignored: substitution failure [with T = double]}}
   int a = f1<int>();
-  const int &b = f2(0);
+  const int &b = f2(0); // cxx2b-note {{in instantiation of function template specialization 'Templates::f2<int>' requested here}}
   double d;
   float &c = f2(0.0); // expected-error {{non-const lvalue reference to type 'float' cannot bind to a value of unrelated type 'double'}}
+  // cxx2b-note@-1 {{in instantiation of function template specialization 'Templates::f2<double>' requested here}}
 
   template<typename T> auto fwd_decl(); // expected-note {{declared here}}
   int e = fwd_decl<int>(); // expected-error {{cannot be used before it is defined}}
@@ -145,8 +149,9 @@
   auto (*p)() = f1; // expected-error {{incompatible initializer}}
   auto (*q)() = f1<int>; // ok
 
-  typedef decltype(f2(1.2)) dbl; // expected-note {{previous}}
-  typedef float dbl; // expected-error {{typedef redefinition with different types ('float' vs 'decltype(f2(1.2))' (aka 'double &'))}}
+  typedef decltype(f2(1.2)) dbl; // cxx14_20-note {{previous}}
+  // cxx2b-error@-1 {{no matching function for call to 'f2'}}
+  typedef float dbl; // cxx14_20-error {{typedef redefinition with different types ('float' vs 'decltype(f2(1.2))' (aka 'double &'))}}
 
   extern template auto fwd_decl<double>();
   int k1 = fwd_decl<double>();
diff --git a/clang/test/SemaCXX/return-stack-addr.cpp b/clang/test/SemaCXX/return-stack-addr.cpp
--- a/clang/test/SemaCXX/return-stack-addr.cpp
+++ b/clang/test/SemaCXX/return-stack-addr.cpp
@@ -1,6 +1,6 @@
-// RUN: %clang_cc1 -std=c++2b -fsyntax-only -verify=expected       %s
-// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify=expected       %s
-// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify=expected,cxx11 %s
+// RUN: %clang_cc1 -std=c++2b -fsyntax-only -verify=expected,cxx2b          %s
+// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify=expected,cxx11_20       %s
+// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify=expected,cxx11_20,cxx11 %s
 
 int* ret_local() {
   int x = 1;
@@ -29,7 +29,8 @@
 
 int& ret_local_ref() {
   int x = 1;
-  return x;  // expected-warning {{reference to stack memory}}
+  return x; // cxx11_20-warning {{reference to stack memory}}
+  // cxx2b-error@-1 {{non-const lvalue reference to type 'int' cannot bind to a temporary of type 'int'}}
 }
 
 int* ret_local_addrOf() {
@@ -154,8 +155,10 @@
   (void) [&]() -> int& { return b; };
   (void) [=]() mutable -> int& { return a; };
   (void) [=]() mutable -> int& { return b; };
-  (void) [&]() -> int& { int a; return a; }; // expected-warning {{reference to stack}}
-  (void) [=]() -> int& { int a; return a; }; // expected-warning {{reference to stack}}
+  (void) [&]() -> int& { int a; return a; }; // cxx11_20-warning {{reference to stack}}
+  // cxx2b-error@-1 {{non-const lvalue reference to type 'int' cannot bind to a temporary of type 'int'}}
+  (void) [=]() -> int& { int a; return a; }; // cxx11_20-warning {{reference to stack}}
+  // cxx2b-error@-1 {{non-const lvalue reference to type 'int' cannot bind to a temporary of type 'int'}}
   (void) [&]() -> int& { int &a = b; return a; };
   (void) [=]() mutable -> int& { int &a = b; return a; };
 
diff --git a/clang/test/SemaCXX/warn-return-std-move.cpp b/clang/test/SemaCXX/warn-return-std-move.cpp
--- a/clang/test/SemaCXX/warn-return-std-move.cpp
+++ b/clang/test/SemaCXX/warn-return-std-move.cpp
@@ -1,8 +1,8 @@
-// RUN: %clang_cc1 -std=c++2b -fsyntax-only -verify=cxx20_2b -fcxx-exceptions -Wreturn-std-move %s
-// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify=cxx20_2b -fcxx-exceptions -Wreturn-std-move %s
-// RUN: %clang_cc1 -std=c++17 -fsyntax-only -verify=cxx11_17 -fcxx-exceptions -Wreturn-std-move %s
-// RUN: %clang_cc1 -std=c++14 -fsyntax-only -verify=cxx11_17 -fcxx-exceptions -Wreturn-std-move %s
-// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify=cxx11_17 -fcxx-exceptions -Wreturn-std-move %s
+// RUN: %clang_cc1 -std=c++2b -fsyntax-only -verify=cxx20_2b,cxx2b -fcxx-exceptions -Wreturn-std-move %s
+// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify=cxx20_2b       -fcxx-exceptions -Wreturn-std-move %s
+// RUN: %clang_cc1 -std=c++17 -fsyntax-only -verify=cxx11_17       -fcxx-exceptions -Wreturn-std-move %s
+// RUN: %clang_cc1 -std=c++14 -fsyntax-only -verify=cxx11_17       -fcxx-exceptions -Wreturn-std-move %s
+// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify=cxx11_17       -fcxx-exceptions -Wreturn-std-move %s
 
 // RUN: %clang_cc1 -std=c++17 -fsyntax-only -fcxx-exceptions -Wreturn-std-move -fdiagnostics-parseable-fixits %s 2>&1 | FileCheck %s -check-prefix=CHECK
 // RUN: %clang_cc1 -std=c++14 -fsyntax-only -fcxx-exceptions -Wreturn-std-move -fdiagnostics-parseable-fixits %s 2>&1 | FileCheck %s -check-prefix=CHECK
@@ -217,8 +217,8 @@
 }
 
 // But if the return type is a reference type, then moving would be wrong.
-Derived& testRetRef1(Derived&& d) { return d; }
-Base& testRetRef2(Derived&& d) { return d; }
+Derived &testRetRef1(Derived &&d) { return d; } // cxx2b-error {{non-const lvalue reference to type 'Derived' cannot bind to a temporary of type 'Derived'}}
+Base &testRetRef2(Derived &&d) { return d; }    // cxx2b-error {{non-const lvalue reference to type 'Base' cannot bind to a temporary of type 'Derived'}}
 #if __cplusplus >= 201402L
 auto&& testRetRef3(Derived&& d) { return d; }
 decltype(auto) testRetRef4(Derived&& d) { return (d); }