SILGen: just for fun let's do toll-free bridging for <T : NSError> archetypes too

Swift SVN r31262

Author: slavapestov

lib/SIL/SILType.cpp

@@ -279,9 +279,12 @@ static bool isBridgedErrorClass(SILModule &M,
   if (!t)
     return false;
 
+  if (auto archetypeType = t->getAs<ArchetypeType>())
+    t = archetypeType->getSuperclass();
+
   // NSError (TODO: and CFError) can be bridged.
   auto errorType = M.Types.getNSErrorType();
-  if (errorType && t->isEqual(errorType)) {
+  if (t && errorType && t->isEqual(errorType)) {
     return true;
   }
 

test/SILGen/objc_error.swift

@@ -11,6 +11,13 @@ func NSErrorErrorType_erasure(x: NSError) -> ErrorType {
   return x
 }
 
+// CHECK-LABEL: sil hidden @_TF10objc_error34NSErrorErrorType_archetype_erasureuRdq_CSo7NSError_Fq_PSs9ErrorType_
+// CHECK:         [[ERROR_TYPE:%.*]] = init_existential_ref %0 : $T : $T, $ErrorType
+// CHECK:         return [[ERROR_TYPE]]
+func NSErrorErrorType_archetype_erasure<T : NSError>(t: T) -> ErrorType {
+  return t
+}
+
 // Test patterns that are non-trivial, but irrefutable.  SILGen shouldn't crash
 // on these.
 func test_doesnt_throw() {