[ObjC] Properly annotate extensions for ARC.

Just like fields, some extension fieldnames can be named such that they appear
to have meaning to ARC. Add the annotation to the compiler will get things
correct.

Add a bunch of extensions to allow inspection on generation to ensure things
are correct.

objectivec/Tests/unittest_objc.proto

@@ -409,6 +409,335 @@ message ObjCRetainedFoo {
   repeated Foo mutableCopy_Val_upper_enum_repeated = 724;
   repeated Foo mutableCopyvalue_lower_no_underscore_enum_repeated = 725;
   repeated Foo mutableCopyValue_upper_no_underscore_enum_repeated = 726;
+
+  extensions 1000 to 3999;
+}
+
+// Extension fields with retained names.
+extend ObjCRetainedFoo {
+  optional string new_val_lower_complex = 1011;
+  optional string new_Val_upper_complex = 1012;
+  optional string newvalue_lower_no_underscore_complex = 1013;
+  optional string newValue_upper_no_underscore_complex = 1014;
+
+  optional int32 new_val_lower_primitive = 1015;
+  optional int32 new_Val_upper_primitive = 1016;
+  optional int32 newvalue_lower_no_underscore_primitive = 1017;
+  optional int32 newValue_upper_no_underscore_primitive = 1018;
+
+  optional self new_val_lower_message = 1019;
+  optional self new_Val_upper_message = 1020;
+  optional self newvalue_lower_no_underscore_message = 1021;
+  optional self newValue_upper_no_underscore_message = 1022;
+
+  optional Foo new_val_lower_enum = 1023;
+  optional Foo new_Val_upper_enum = 1024;
+  optional Foo newvalue_lower_no_underscore_enum = 1025;
+  optional Foo newValue_upper_no_underscore_enum = 1026;
+
+  repeated string new_val_lower_complex_repeated = 1111;
+  repeated string new_Val_upper_complex_repeated = 1112;
+  repeated string newvalue_lower_no_underscore_complex_repeated = 1113;
+  repeated string newValue_upper_no_underscore_complex_repeated = 1114;
+
+  repeated int32 new_val_lower_primitive_repeated = 1115;
+  repeated int32 new_Val_upper_primitive_repeated = 1116;
+  repeated int32 newvalue_lower_no_underscore_primitive_repeated = 1117;
+  repeated int32 newValue_upper_no_underscore_primitive_repeated = 1118;
+
+  repeated self new_val_lower_message_repeated = 1119;
+  repeated self new_Val_upper_message_repeated = 1120;
+  repeated self newvalue_lower_no_underscore_message_repeated = 1121;
+  repeated self newValue_upper_no_underscore_message_repeated = 1122;
+
+  repeated Foo new_val_lower_enum_repeated = 1123;
+  repeated Foo new_Val_upper_enum_repeated = 1124;
+  repeated Foo newvalue_lower_no_underscore_enum_repeated = 1125;
+  repeated Foo newValue_upper_no_underscore_enum_repeated = 1126;
+
+  optional string alloc_val_lower_complex = 1211;
+  optional string alloc_Val_upper_complex = 1212;
+  optional string allocvalue_lower_no_underscore_complex = 1213;
+  optional string allocValue_upper_no_underscore_complex = 1214;
+
+  optional int32 alloc_val_lower_primitive = 1215;
+  optional int32 alloc_Val_upper_primitive = 1216;
+  optional int32 allocvalue_lower_no_underscore_primitive = 1217;
+  optional int32 allocValue_upper_no_underscore_primitive = 1218;
+
+  optional self alloc_val_lower_message = 1219;
+  optional self alloc_Val_upper_message = 1220;
+  optional self allocvalue_lower_no_underscore_message = 1221;
+  optional self allocValue_upper_no_underscore_message = 1222;
+
+  optional Foo alloc_val_lower_enum = 1223;
+  optional Foo alloc_Val_upper_enum = 1224;
+  optional Foo allocvalue_lower_no_underscore_enum = 1225;
+  optional Foo allocValue_upper_no_underscore_enum = 1226;
+
+  repeated string alloc_val_lower_complex_repeated = 1311;
+  repeated string alloc_Val_upper_complex_repeated = 1312;
+  repeated string allocvalue_lower_no_underscore_complex_repeated = 1313;
+  repeated string allocValue_upper_no_underscore_complex_repeated = 1314;
+
+  repeated int32 alloc_val_lower_primitive_repeated = 1315;
+  repeated int32 alloc_Val_upper_primitive_repeated = 1316;
+  repeated int32 allocvalue_lower_no_underscore_primitive_repeated = 1317;
+  repeated int32 allocValue_upper_no_underscore_primitive_repeated = 1318;
+
+  repeated self alloc_val_lower_message_repeated = 1319;
+  repeated self alloc_Val_upper_message_repeated = 1320;
+  repeated self allocvalue_lower_no_underscore_message_repeated = 1321;
+  repeated self allocValue_upper_no_underscore_message_repeated = 1322;
+
+  repeated Foo alloc_val_lower_enum_repeated = 1323;
+  repeated Foo alloc_Val_upper_enum_repeated = 1324;
+  repeated Foo allocvalue_lower_no_underscore_enum_repeated = 1325;
+  repeated Foo allocValue_upper_no_underscore_enum_repeated = 1326;
+
+  optional string copy_val_lower_complex = 1411;
+  optional string copy_Val_upper_complex = 1412;
+  optional string copyvalue_lower_no_underscore_complex = 1413;
+  optional string copyValue_upper_no_underscore_complex = 1414;
+
+  optional int32 copy_val_lower_primitive = 1415;
+  optional int32 copy_Val_upper_primitive = 1416;
+  optional int32 copyvalue_lower_no_underscore_primitive = 1417;
+  optional int32 copyValue_upper_no_underscore_primitive = 1418;
+
+  optional self copy_val_lower_message = 1419;
+  optional self copy_Val_upper_message = 1420;
+  optional self copyvalue_lower_no_underscore_message = 1421;
+  optional self copyValue_upper_no_underscore_message = 1422;
+
+  optional Foo copy_val_lower_enum = 1423;
+  optional Foo copy_Val_upper_enum = 1424;
+  optional Foo copyvalue_lower_no_underscore_enum = 1425;
+  optional Foo copyValue_upper_no_underscore_enum = 1426;
+
+  repeated string copy_val_lower_complex_repeated = 1511;
+  repeated string copy_Val_upper_complex_repeated = 1512;
+  repeated string copyvalue_lower_no_underscore_complex_repeated = 1513;
+  repeated string copyValue_upper_no_underscore_complex_repeated = 1514;
+
+  repeated int32 copy_val_lower_primitive_repeated = 1515;
+  repeated int32 copy_Val_upper_primitive_repeated = 1516;
+  repeated int32 copyvalue_lower_no_underscore_primitive_repeated = 1517;
+  repeated int32 copyValue_upper_no_underscore_primitive_repeated = 1518;
+
+  repeated self copy_val_lower_message_repeated = 1519;
+  repeated self copy_Val_upper_message_repeated = 1520;
+  repeated self copyvalue_lower_no_underscore_message_repeated = 1521;
+  repeated self copyValue_upper_no_underscore_message_repeated = 1522;
+
+  repeated Foo copy_val_lower_enum_repeated = 1523;
+  repeated Foo copy_Val_upper_enum_repeated = 1524;
+  repeated Foo copyvalue_lower_no_underscore_enum_repeated = 1525;
+  repeated Foo copyValue_upper_no_underscore_enum_repeated = 1526;
+
+  optional string mutableCopy_val_lower_complex = 1611;
+  optional string mutableCopy_Val_upper_complex = 1612;
+  optional string mutableCopyvalue_lower_no_underscore_complex = 1613;
+  optional string mutableCopyValue_upper_no_underscore_complex = 1614;
+
+  optional int32 mutableCopy_val_lower_primitive = 1615;
+  optional int32 mutableCopy_Val_upper_primitive = 1616;
+  optional int32 mutableCopyvalue_lower_no_underscore_primitive = 1617;
+  optional int32 mutableCopyValue_upper_no_underscore_primitive = 1618;
+
+  optional self mutableCopy_val_lower_message = 1619;
+  optional self mutableCopy_Val_upper_message = 1620;
+  optional self mutableCopyvalue_lower_no_underscore_message = 1621;
+  optional self mutableCopyValue_upper_no_underscore_message = 1622;
+
+  optional Foo mutableCopy_val_lower_enum = 1623;
+  optional Foo mutableCopy_Val_upper_enum = 1624;
+  optional Foo mutableCopyvalue_lower_no_underscore_enum = 1625;
+  optional Foo mutableCopyValue_upper_no_underscore_enum = 1626;
+
+  repeated string mutableCopy_val_lower_complex_repeated = 1711;
+  repeated string mutableCopy_Val_upper_complex_repeated = 1712;
+  repeated string mutableCopyvalue_lower_no_underscore_complex_repeated = 1713;
+  repeated string mutableCopyValue_upper_no_underscore_complex_repeated = 1714;
+
+  repeated int32 mutableCopy_val_lower_primitive_repeated = 1715;
+  repeated int32 mutableCopy_Val_upper_primitive_repeated = 1716;
+  repeated int32 mutableCopyvalue_lower_no_underscore_primitive_repeated = 1717;
+  repeated int32 mutableCopyValue_upper_no_underscore_primitive_repeated = 1718;
+
+  repeated self mutableCopy_val_lower_message_repeated = 1719;
+  repeated self mutableCopy_Val_upper_message_repeated = 1720;
+  repeated self mutableCopyvalue_lower_no_underscore_message_repeated = 1721;
+  repeated self mutableCopyValue_upper_no_underscore_message_repeated = 1722;
+
+  repeated Foo mutableCopy_val_lower_enum_repeated = 1723;
+  repeated Foo mutableCopy_Val_upper_enum_repeated = 1724;
+  repeated Foo mutableCopyvalue_lower_no_underscore_enum_repeated = 1725;
+  repeated Foo mutableCopyValue_upper_no_underscore_enum_repeated = 1726;
+}
+
+message JustToScopeExtensions {
+  extend ObjCRetainedFoo {
+    optional string new_val_lower_complex = 2011;
+    optional string new_Val_upper_complex = 2012;
+    optional string newvalue_lower_no_underscore_complex = 2013;
+    optional string newValue_upper_no_underscore_complex = 2014;
+
+    optional int32 new_val_lower_primitive = 2015;
+    optional int32 new_Val_upper_primitive = 2016;
+    optional int32 newvalue_lower_no_underscore_primitive = 2017;
+    optional int32 newValue_upper_no_underscore_primitive = 2018;
+
+    optional self new_val_lower_message = 2019;
+    optional self new_Val_upper_message = 2020;
+    optional self newvalue_lower_no_underscore_message = 2021;
+    optional self newValue_upper_no_underscore_message = 2022;
+
+    optional Foo new_val_lower_enum = 2023;
+    optional Foo new_Val_upper_enum = 2024;
+    optional Foo newvalue_lower_no_underscore_enum = 2025;
+    optional Foo newValue_upper_no_underscore_enum = 2026;
+
+    repeated string new_val_lower_complex_repeated = 2111;
+    repeated string new_Val_upper_complex_repeated = 2112;
+    repeated string newvalue_lower_no_underscore_complex_repeated = 2113;
+    repeated string newValue_upper_no_underscore_complex_repeated = 2114;
+
+    repeated int32 new_val_lower_primitive_repeated = 2115;
+    repeated int32 new_Val_upper_primitive_repeated = 2116;
+    repeated int32 newvalue_lower_no_underscore_primitive_repeated = 2117;
+    repeated int32 newValue_upper_no_underscore_primitive_repeated = 2118;
+
+    repeated self new_val_lower_message_repeated = 2119;
+    repeated self new_Val_upper_message_repeated = 2120;
+    repeated self newvalue_lower_no_underscore_message_repeated = 2121;
+    repeated self newValue_upper_no_underscore_message_repeated = 2122;
+
+    repeated Foo new_val_lower_enum_repeated = 2123;
+    repeated Foo new_Val_upper_enum_repeated = 2124;
+    repeated Foo newvalue_lower_no_underscore_enum_repeated = 2125;
+    repeated Foo newValue_upper_no_underscore_enum_repeated = 2126;
+
+    optional string alloc_val_lower_complex = 2211;
+    optional string alloc_Val_upper_complex = 2212;
+    optional string allocvalue_lower_no_underscore_complex = 2213;
+    optional string allocValue_upper_no_underscore_complex = 2214;
+
+    optional int32 alloc_val_lower_primitive = 2215;
+    optional int32 alloc_Val_upper_primitive = 2216;
+    optional int32 allocvalue_lower_no_underscore_primitive = 2217;
+    optional int32 allocValue_upper_no_underscore_primitive = 2218;
+
+    optional self alloc_val_lower_message = 2219;
+    optional self alloc_Val_upper_message = 2220;
+    optional self allocvalue_lower_no_underscore_message = 2221;
+    optional self allocValue_upper_no_underscore_message = 2222;
+
+    optional Foo alloc_val_lower_enum = 2223;
+    optional Foo alloc_Val_upper_enum = 2224;
+    optional Foo allocvalue_lower_no_underscore_enum = 2225;
+    optional Foo allocValue_upper_no_underscore_enum = 2226;
+
+    repeated string alloc_val_lower_complex_repeated = 2311;
+    repeated string alloc_Val_upper_complex_repeated = 2312;
+    repeated string allocvalue_lower_no_underscore_complex_repeated = 2313;
+    repeated string allocValue_upper_no_underscore_complex_repeated = 2314;
+
+    repeated int32 alloc_val_lower_primitive_repeated = 2315;
+    repeated int32 alloc_Val_upper_primitive_repeated = 2316;
+    repeated int32 allocvalue_lower_no_underscore_primitive_repeated = 2317;
+    repeated int32 allocValue_upper_no_underscore_primitive_repeated = 2318;
+
+    repeated self alloc_val_lower_message_repeated = 2319;
+    repeated self alloc_Val_upper_message_repeated = 2320;
+    repeated self allocvalue_lower_no_underscore_message_repeated = 2321;
+    repeated self allocValue_upper_no_underscore_message_repeated = 2322;
+
+    repeated Foo alloc_val_lower_enum_repeated = 2323;
+    repeated Foo alloc_Val_upper_enum_repeated = 2324;
+    repeated Foo allocvalue_lower_no_underscore_enum_repeated = 2325;
+    repeated Foo allocValue_upper_no_underscore_enum_repeated = 2326;
+
+    optional string copy_val_lower_complex = 2411;
+    optional string copy_Val_upper_complex = 2412;
+    optional string copyvalue_lower_no_underscore_complex = 2413;
+    optional string copyValue_upper_no_underscore_complex = 2414;
+
+    optional int32 copy_val_lower_primitive = 2415;
+    optional int32 copy_Val_upper_primitive = 2416;
+    optional int32 copyvalue_lower_no_underscore_primitive = 2417;
+    optional int32 copyValue_upper_no_underscore_primitive = 2418;
+
+    optional self copy_val_lower_message = 2419;
+    optional self copy_Val_upper_message = 2420;
+    optional self copyvalue_lower_no_underscore_message = 2421;
+    optional self copyValue_upper_no_underscore_message = 2422;
+
+    optional Foo copy_val_lower_enum = 2423;
+    optional Foo copy_Val_upper_enum = 2424;
+    optional Foo copyvalue_lower_no_underscore_enum = 2425;
+    optional Foo copyValue_upper_no_underscore_enum = 2426;
+
+    repeated string copy_val_lower_complex_repeated = 2511;
+    repeated string copy_Val_upper_complex_repeated = 2512;
+    repeated string copyvalue_lower_no_underscore_complex_repeated = 2513;
+    repeated string copyValue_upper_no_underscore_complex_repeated = 2514;
+
+    repeated int32 copy_val_lower_primitive_repeated = 2515;
+    repeated int32 copy_Val_upper_primitive_repeated = 2516;
+    repeated int32 copyvalue_lower_no_underscore_primitive_repeated = 2517;
+    repeated int32 copyValue_upper_no_underscore_primitive_repeated = 2518;
+
+    repeated self copy_val_lower_message_repeated = 2519;
+    repeated self copy_Val_upper_message_repeated = 2520;
+    repeated self copyvalue_lower_no_underscore_message_repeated = 2521;
+    repeated self copyValue_upper_no_underscore_message_repeated = 2522;
+
+    repeated Foo copy_val_lower_enum_repeated = 2523;
+    repeated Foo copy_Val_upper_enum_repeated = 2524;
+    repeated Foo copyvalue_lower_no_underscore_enum_repeated = 2525;
+    repeated Foo copyValue_upper_no_underscore_enum_repeated = 2526;
+
+    optional string mutableCopy_val_lower_complex = 2611;
+    optional string mutableCopy_Val_upper_complex = 2612;
+    optional string mutableCopyvalue_lower_no_underscore_complex = 2613;
+    optional string mutableCopyValue_upper_no_underscore_complex = 2614;
+
+    optional int32 mutableCopy_val_lower_primitive = 2615;
+    optional int32 mutableCopy_Val_upper_primitive = 2616;
+    optional int32 mutableCopyvalue_lower_no_underscore_primitive = 2617;
+    optional int32 mutableCopyValue_upper_no_underscore_primitive = 2618;
+
+    optional self mutableCopy_val_lower_message = 2619;
+    optional self mutableCopy_Val_upper_message = 2620;
+    optional self mutableCopyvalue_lower_no_underscore_message = 2621;
+    optional self mutableCopyValue_upper_no_underscore_message = 2622;
+
+    optional Foo mutableCopy_val_lower_enum = 2623;
+    optional Foo mutableCopy_Val_upper_enum = 2624;
+    optional Foo mutableCopyvalue_lower_no_underscore_enum = 2625;
+    optional Foo mutableCopyValue_upper_no_underscore_enum = 2626;
+
+    repeated string mutableCopy_val_lower_complex_repeated = 2711;
+    repeated string mutableCopy_Val_upper_complex_repeated = 2712;
+    repeated string mutableCopyvalue_lower_no_underscore_complex_repeated = 2713;
+    repeated string mutableCopyValue_upper_no_underscore_complex_repeated = 2714;
+
+    repeated int32 mutableCopy_val_lower_primitive_repeated = 2715;
+    repeated int32 mutableCopy_Val_upper_primitive_repeated = 2716;
+    repeated int32 mutableCopyvalue_lower_no_underscore_primitive_repeated = 2717;
+    repeated int32 mutableCopyValue_upper_no_underscore_primitive_repeated = 2718;
+
+    repeated self mutableCopy_val_lower_message_repeated = 2719;
+    repeated self mutableCopy_Val_upper_message_repeated = 2720;
+    repeated self mutableCopyvalue_lower_no_underscore_message_repeated = 2721;
+    repeated self mutableCopyValue_upper_no_underscore_message_repeated = 2722;
+
+    repeated Foo mutableCopy_val_lower_enum_repeated = 2723;
+    repeated Foo mutableCopy_Val_upper_enum_repeated = 2724;
+    repeated Foo mutableCopyvalue_lower_no_underscore_enum_repeated = 2725;
+    repeated Foo mutableCopyValue_upper_no_underscore_enum_repeated = 2726;
+  }
 }
 
 // Test handling of fields that are the retained names.

src/google/protobuf/compiler/objectivec/objectivec_extension.cc

@@ -61,6 +61,11 @@ ExtensionGenerator::~ExtensionGenerator() {}
 void ExtensionGenerator::GenerateMembersHeader(io::Printer* printer) {
   std::map<string, string> vars;
   vars["method_name"] = method_name_;
+  if (IsRetainedName(method_name_)) {
+    vars["storage_attribute"] = " NS_RETURNS_NOT_RETAINED";
+  } else {
+    vars["storage_attribute"] = "";
+  }
   SourceLocation location;
   if (descriptor_->GetSourceLocation(&location)) {
     vars["comments"] = BuildCommentsString(location, true);
@@ -72,7 +77,7 @@ void ExtensionGenerator::GenerateMembersHeader(io::Printer* printer) {
   vars["deprecated_attribute"] = GetOptionalDeprecatedAttribute(descriptor_, descriptor_->file());
   printer->Print(vars,
                  "$comments$"
-                 "+ (GPBExtensionDescriptor *)$method_name$$deprecated_attribute$;\n");
+                 "+ (GPBExtensionDescriptor *)$method_name$$storage_attribute$$deprecated_attribute$;\n");
 }
 
 void ExtensionGenerator::GenerateStaticVariablesInitialization(