Inconsistent runtime behaviour with `dynamic` type on web and native about sdk

[navaronbracke]

I believe this is working as intended.

If you change

  final Map<String,dynamic> test = Map.from( {
      "value1": 1,
      "value2": "1"
  });

to use Object? instead of dynamic, you should get a type error.

  final Map<String, Object?> test = Map.from( {
      "value1": 1,
      "value2": "1"
  });

When you use dynamic, type checks are omitted, so the assignment to int value2 = test['value2']; is actually unchecked.

[hugovangalen]

When you use dynamic, type checks are omitted, so the assignment to int value2 = test['value2']; is actually unchecked.

Interesting. This isn't unchecked on native. Are you implying that the problem lies in the native runtime?

This for example throws an RTE on native (Linux command line) yet no RTE on web:

    dynamic string3 = "3";
    int value3 = string3;

Regardless, it is inconsistent. I believe the exception should happen either in both, or in neither.

(Also, it appears my title for this bug is incorrect as I now realise this doesn't affect Maps. It boils down to "Inconsistent runtime behaviour with dynamic type on web and native" and I will update that accordingly.)

[mraleph]

This is working as intended: dart2js compiler omits implicit type checks at -O3 optimization level or above. (and dart2wasm even omits explicit type checks). Native compilers never omit type checks.

So you need to write all your type checks explicitly if you don't want them to be omitted (e.g. if they are validating input data from JSON).

[hugovangalen]

Okay thanks for clearing that up!