Nicer error for missing event type

test/aeso_compiler_tests.erl

@@ -496,6 +496,10 @@ failing_contracts() ->
           "and cannot be called from the contract code.">>])
     , ?TEST(bad_top_level_decl,
         [<<?Pos(1, 1) "The definition of 'square' must appear inside a contract or namespace.">>])
+    , ?TEST(missing_event_type,
+        [<<?Pos(3, 5)
+           "Unbound variable Chain.event at line 3, column 5\n"
+           "Did you forget to define the event type?">>])
     ].
 
 -define(Path(File), "code_errors/" ??File).

test/contracts/missing_event_type.aes

@@ -0,0 +1,3 @@
+contract MissingEventType =
+  entrypoint main() =
+    Chain.event("MAIN")