Language: Will Object.toString() return a non-null String?

[leonsenft]

Once we have NNBD, will the type signature of Object.toString() to be changed to enforce that all implementations must return a non-null String?

Or is it considered a desired feature that this method can indeed return null?

[jonahwilliams]

I would think it should be non-null, if only because of the behavior of string interpolation:

class Foo {
  toString() => null;
}

void main() {  print('${Foo(}'); }

Uncaught exception:
Invalid argument: Instance of 'Foo'

[jonahwilliams]

Ahh, I see you've referenced that in a similar issue

[lrhn]

Yes. The return type of Object.toString will almost certainly be String (non-nullable).
(I can't imagine any issue that would change that, but then, you never know).

[leonsenft]

Great, thanks for clarifying!