Allow setting a field with partially defined field (#646)

* allow setting a field with partially defined field

* actually run the test

test/goalc/source_templates/with_game/test-partial-define-type-field.gc

@@ -0,0 +1,10 @@
+(declare-type fake-type basic)
+(deftype type-containing-fake-type (basic)
+  ((field fake-type))
+  )
+
+(let ((obj (new 'stack 'type-containing-fake-type)))
+  (-> obj field)
+  (set! (-> obj field) (the fake-type #f))
+  (format #t "~A~%" (-> obj field))
+  )

test/goalc/test_with_game.cpp

@@ -545,6 +545,12 @@ TEST_F(WithGameTests, InlinedPackedBasics) {
                           "0\n"});
 }
 
+TEST_F(WithGameTests, PartialDefineTypeField) {
+  runner.run_static_test(env, testCategory, "test-partial-define-type-field.gc",
+                         {"#f\n"
+                          "0\n"});
+}
+
 // VECTOR FLOAT TESTS
 
 // ---- One off Tests