Make superclass/interface for immutable Lists that doesn't have mutating methods instead of having throwing methods.

[lrhn]

The current modelling of List uses the same supertype for "normal" lists and for immutable and fixed-length lists, just with, e.g., operator[]= and an add method that throws.

I think it would be better modelling to have a base type for indexable values without those methods, but with extended types that include the operator[]= and add methods. Something like:
  Tuple // Immutable and fixed length, has no add/removeLast or operator[]=
  MutableTuple // Fixed length, has operator[]= but not add/removeLast
  List // The current list - does it all.

("Tuple" is just a suggestion, I'm sure there are better names).

This way, a const<int>[2,4] would be a Tuple<int>, but [2,4] is a List<int>.

Something similar could be done for maps, and you probably don't even want the case where you can mutate the values but not change the keys.

[iposva-google]

We have been in this situation (GrowableArray vs Array) with the unfortunate result of not being able to assign immutable lists to parameters typed as List, which lead to unending confusion. The current situation is the resolution of that situation and I don't think we have enough evidence to restart that discussion.

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cc @kasperl.
Added WontFix label.

[kasperl]

FWIW I think we made the right call and I agree with the WontFix.

[lrhn]

Ok, I see the point, and Dart is a pragmatic language :) And because types are already covariant, you can trust reading from something based on the declared type, but you can't really trust mutating anyway. This actually fits in.