Implement latest C++ feature test macro recommendations.

We don't yet advertise init capture packs, because I found some bugs
while testing it. We reject-valid and then crash on both of these:

template<int ...a> auto x = [...y = a] {};
template<int ...a> auto x = [y = a...] {};

clang/lib/Frontend/InitPreprocessor.cpp

@@ -484,6 +484,7 @@ static void InitializeCPlusPlusFeatureTestMacros(const LangOptions &LangOpts,
                         LangOpts.CPlusPlus2a ? "201907L" :
                         LangOpts.CPlusPlus17 ? "201603L" :
                         LangOpts.CPlusPlus14 ? "201304L" : "200704");
+    Builder.defineMacro("__cpp_constexpr_in_decltype", "201711L");
     Builder.defineMacro("__cpp_range_based_for",
                         LangOpts.CPlusPlus17 ? "201603L" : "200907");
     Builder.defineMacro("__cpp_static_assert",
@@ -506,8 +507,9 @@ static void InitializeCPlusPlusFeatureTestMacros(const LangOptions &LangOpts,
   if (LangOpts.CPlusPlus14) {
     Builder.defineMacro("__cpp_binary_literals", "201304L");
     Builder.defineMacro("__cpp_digit_separators", "201309L");
-    Builder.defineMacro("__cpp_init_captures", "201304L");
-    Builder.defineMacro("__cpp_generic_lambdas", "201304L");
+    Builder.defineMacro("__cpp_init_captures", "201304L"); // (not latest)
+    Builder.defineMacro("__cpp_generic_lambdas",
+                        LangOpts.CPlusPlus2a ? "201707L" : "201304L");
     Builder.defineMacro("__cpp_decltype_auto", "201304L");
     Builder.defineMacro("__cpp_return_type_deduction", "201304L");
     Builder.defineMacro("__cpp_aggregate_nsdmi", "201304L");
@@ -523,15 +525,16 @@ static void InitializeCPlusPlusFeatureTestMacros(const LangOptions &LangOpts,
     Builder.defineMacro("__cpp_noexcept_function_type", "201510L");
     Builder.defineMacro("__cpp_capture_star_this", "201603L");
     Builder.defineMacro("__cpp_if_constexpr", "201606L");
-    Builder.defineMacro("__cpp_deduction_guides", "201703L");
+    Builder.defineMacro("__cpp_deduction_guides", "201703L"); // (not latest)
     Builder.defineMacro("__cpp_template_auto", "201606L"); // (old name)
     Builder.defineMacro("__cpp_namespace_attributes", "201411L");
     Builder.defineMacro("__cpp_enumerator_attributes", "201411L");
     Builder.defineMacro("__cpp_nested_namespace_definitions", "201411L");
     Builder.defineMacro("__cpp_variadic_using", "201611L");
     Builder.defineMacro("__cpp_aggregate_bases", "201603L");
     Builder.defineMacro("__cpp_structured_bindings", "201606L");
-    Builder.defineMacro("__cpp_nontype_template_args", "201411L");
+    Builder.defineMacro("__cpp_nontype_template_args",
+                        "201411L"); // (not latest)
     Builder.defineMacro("__cpp_fold_expressions", "201603L");
     Builder.defineMacro("__cpp_guaranteed_copy_elision", "201606L");
     Builder.defineMacro("__cpp_nontype_template_parameter_auto", "201606L");
@@ -543,10 +546,17 @@ static void InitializeCPlusPlusFeatureTestMacros(const LangOptions &LangOpts,
 
   // C++20 features.
   if (LangOpts.CPlusPlus2a) {
+    //Builder.defineMacro("__cpp_aggregate_paren_init", "201902L");
+    //Builder.defineMacro("__cpp_concepts", "201907L");
     Builder.defineMacro("__cpp_conditional_explicit", "201806L");
+    //Builder.defineMacro("__cpp_consteval", "201811L");
     Builder.defineMacro("__cpp_constexpr_dynamic_alloc", "201907L");
     Builder.defineMacro("__cpp_constinit", "201907L");
+    //Builder.defineMacro("__cpp_coroutines", "201902L");
+    Builder.defineMacro("__cpp_designated_initializers", "201707L");
     Builder.defineMacro("__cpp_impl_three_way_comparison", "201907L");
+    //Builder.defineMacro("__cpp_modules", "201907L");
+    //Builder.defineMacro("__cpp_using_enum", "201907L");
   }
   if (LangOpts.Char8)
     Builder.defineMacro("__cpp_char8_t", "201811L");

clang/test/Lexer/cxx-features.cpp

@@ -34,14 +34,30 @@
 #error "wrong value for __cpp_char8_t"
 #endif
 
+#if check(conditional_explicit, 0, 0, 0, 0, 201806)
+#error "wrong value for __cpp_conditional_explicit"
+#endif
+
+// constexpr checked below
+
 #if check(constexpr_dynamic_alloc, 0, 0, 0, 0, 201907)
 #error "wrong value for __cpp_constexpr_dynamic_alloc"
 #endif
 
+#if check(constexpr_in_decltype, 0, 201711, 201711, 201711, 201711)
+#error "wrong value for __cpp_constexpr_in_decltype"
+#endif
+
 #if check(constinit, 0, 0, 0, 0, 201907)
 #error "wrong value for __cpp_constinit"
 #endif
 
+#if check(designated_initializers, 0, 0, 0, 0, 201707)
+#error "wrong value for __cpp_designated_initializers"
+#endif
+
+// generic_lambdas checked below
+
 #if check(impl_destroying_delete, 201806, 201806, 201806, 201806, 201806)
 #error "wrong value for __cpp_impl_destroying_delete"
 #endif
@@ -158,7 +174,7 @@
 #error "wrong value for __cpp_init_captures"
 #endif
 
-#if check(generic_lambdas, 0, 0, 201304, 201304, 201304)
+#if check(generic_lambdas, 0, 0, 201304, 201304, 201707)
 #error "wrong value for __cpp_generic_lambdas"
 #endif
 

clang/www/cxx_status.html

@@ -1227,22 +1227,15 @@ <h2 id="ts">Technical specifications and standing documents</h2>
       </td>
     </tr>
     <tr>
-      <td class="partial" align="center">
-        WIP (<a href="https://wg21.link/p1353r0">P1353R0</a>)
-      </td>
-    </tr>
-    <tr>
-      <td class="none" align="center">
-        No (<a href="https://wg21.link/p1902r1">P1902R1</a>)</a>
+      <td class="full" align="center">
+        Clang 9 (<a href="https://wg21.link/p1353r0">P1353R0</a>)
       </td>
     </tr>
-    <!-- FIXME: Implement latest recommendations.
     <tr>
       <td class="svn" align="center">
-        SVN (<a href="https://wg21.link/p0096r3">P0096R3</a>)</a>
+        SVN (<a href="https://wg21.link/p1902r1">P1902R1</a>)</a>
       </td>
     </tr>
-    -->
     <!-- No compiler support is known to be needed for:
            * Concurrency TS
            * Parallelism TS (v1, v2)