Index: include/clang/Basic/DiagnosticGroups.td
===================================================================
--- include/clang/Basic/DiagnosticGroups.td
+++ include/clang/Basic/DiagnosticGroups.td
@@ -169,6 +169,9 @@
 def CXXPre1zCompatPedantic : DiagGroup<"c++98-c++11-c++14-compat-pedantic",
                                        [CXXPre1zCompat]>;
 
+// Warnings for C++2a code which is not compatible with prior C++ standards.
+def CXXPre2aCompat : DiagGroup<"c++98-c++11-c++14-c++17-compat">;
+
 def CXX98CompatBindToTemporaryCopy :
   DiagGroup<"c++98-compat-bind-to-temporary-copy">;
 def CXX98CompatLocalTypeTemplateArgs :
@@ -180,7 +183,8 @@
                             [CXX98CompatLocalTypeTemplateArgs,
                              CXX98CompatUnnamedTypeTemplateArgs,
                              CXXPre14Compat,
-                             CXXPre1zCompat]>;
+                             CXXPre1zCompat,
+                             CXXPre2aCompat]>;
 // Warnings for C++11 features which are Extensions in C++98 mode.
 def CXX98CompatPedantic : DiagGroup<"c++98-compat-pedantic",
                                     [CXX98Compat,
@@ -211,7 +215,8 @@
                              CXX11CompatReservedUserDefinedLiteral,
                              CXX11CompatDeprecatedWritableStr,
                              CXXPre14Compat,
-                             CXXPre1zCompat]>;
+                             CXXPre1zCompat,
+                             CXXPre2aCompat]>;
 def : DiagGroup<"c++0x-compat", [CXX11Compat]>;
 def CXX11CompatPedantic : DiagGroup<"c++11-compat-pedantic",
                                     [CXXPre14CompatPedantic,
@@ -784,9 +789,14 @@
 // earlier C++ versions.
 def CXX17 : DiagGroup<"c++17-extensions">;
 
+// A warning group for warnings about using C++2a features as extensions in
+// earlier C++ versions.
+def CXX20 : DiagGroup<"c++20-extensions">;
+
 def : DiagGroup<"c++0x-extensions", [CXX11]>;
 def : DiagGroup<"c++1y-extensions", [CXX14]>;
 def : DiagGroup<"c++1z-extensions", [CXX17]>;
+def : DiagGroup<"c++2a-extensions", [CXX20]>;
 
 def DelegatingCtorCycles :
   DiagGroup<"delegating-ctor-cycles">;
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -4088,6 +4088,13 @@
 def err_pointer_to_member_oper_value_classify: Error<
   "pointer-to-member function type %0 can only be called on an "
   "%select{rvalue|lvalue}1">;
+def ext_pointer_to_const_ref_member_on_rvalue : ExtWarn<
+  "pointer-to-member to const& function on an rvalue is a C++2a extension">,
+  InGroup<CXX20>;
+def warn_cxx17_compat_pointer_to_const_ref_member_on_rvalue : Warning<
+  "pointer-to-member function for const& member function on rvalues is "
+  "incompatible with C++ standards before C++2a">,
+  InGroup<CXXPre2aCompat>, DefaultIgnore;
 def ext_ms_deref_template_argument: ExtWarn<
   "non-type template argument containing a dereference operation is a "
   "Microsoft extension">, InGroup<MicrosoftTemplate>;
Index: lib/Sema/SemaExprCXX.cpp
===================================================================
--- lib/Sema/SemaExprCXX.cpp
+++ lib/Sema/SemaExprCXX.cpp
@@ -5175,9 +5175,16 @@
       break;
 
     case RQ_LValue:
-      if (!isIndirect && !LHS.get()->Classify(Context).isLValue())
-        Diag(Loc, diag::err_pointer_to_member_oper_value_classify)
-          << RHSType << 1 << LHS.get()->getSourceRange();
+      if (!isIndirect && !LHS.get()->Classify(Context).isLValue()) {
+        // C++2a allows functions with ref-qualifier & if they are also 'const'.
+        if (Proto->isConst())
+          Diag(Loc, getLangOpts().CPlusPlus2a
+                        ? diag::warn_cxx17_compat_pointer_to_const_ref_member_on_rvalue
+                        : diag::ext_pointer_to_const_ref_member_on_rvalue);
+        else
+          Diag(Loc, diag::err_pointer_to_member_oper_value_classify)
+              << RHSType << 1 << LHS.get()->getSourceRange();
+      }
       break;
 
     case RQ_RValue:
Index: www/cxx_status.html
===================================================================
--- www/cxx_status.html
+++ www/cxx_status.html
@@ -777,13 +777,12 @@
 
 <h2 id="cxx20">C++2a implementation status</h2>
 
-<p>Clang does not yet support any of the proposed features of
-<!--<p>Clang has <b>experimental</b> support for some proposed features of-->
+<p>Clang has <b>experimental</b> support for some proposed features of
 the C++ standard following C++17, provisionally named C++2a.
 Note that support for these features may change or be removed without notice,
 as the draft C++2a standard evolves.
 
-<!--<p>You can use Clang in C++2a mode with the <code>-std=c++2a</code> option.</p>-->
+<p>You can use Clang in C++2a mode with the <code>-std=c++2a</code> option.</p>
 
 <details open>
 <summary>List of features and minimum Clang version with support</summary>
@@ -803,7 +802,7 @@
     <tr>
       <td><tt>const&amp;</tt>-qualified pointers to members</td>
       <td><a href="http://wg21.link/p0704r1">P0704R1</a></td>
-      <td class="none" align="center">No</td>
+      <td class="svn" align="center">SVN</td>
     </tr>
     <tr>
       <td>Allow <i>lambda-capture</i> <tt>[=, this]</tt></td>