Do not type checks at returns of implicit getter.

runtime/vm/code_generator_ia32.cc

Index: runtime/vm/code_generator_ia32.cc
===================================================================
--- runtime/vm/code_generator_ia32.cc	(revision 1802)
+++ runtime/vm/code_generator_ia32.cc	(working copy)
@@ -797,11 +797,15 @@
 
   // Generate type check.
   if (FLAG_enable_type_checks) {
-    GenerateAssertAssignable(
-        node->id(),
-        node->value()->token_index(),
-        Type::ZoneHandle(parsed_function().function().result_type()),
-        String::ZoneHandle(String::NewSymbol("function result")));
+    RawFunction::Kind  kind = parsed_function().function().kind();
+    if ((kind != RawFunction::kImplicitGetter) &&
+        (kind != RawFunction::kConstImplicitGetter)) {
+      GenerateAssertAssignable(
+          node->id(),
+          node->value()->token_index(),
+          Type::ZoneHandle(parsed_function().function().result_type()),
+          String::ZoneHandle(String::NewSymbol("function result")));
+    }
   }
   // Unchain the context(s) up to context level 0.
   int context_level = state()->context_level();