In checked mode, void now allows every value

[floitschG]

As per dart-lang/sdk#28935, Dart will now allow any value for void.
I'm in the process of committing the changes to dart2js and the VM.
The spec is not yet updated (dart-lang/sdk#28936), but the change should be pretty simple.

The following tests are affected by this change:

Language/Functions/generator_return_type_t01
Language/Functions/generator_return_type_t02
Language/Functions/async_return_type_t01
Language/Types/Type_Void/returning_t02
Language/Types/Type_Void/returning_t03
Language/Types/Type_Void/returning_t04
Language/Types/Type_Void/returning_t05

[sgrekhov]

Will fix this when 1.25 became available

[floitschG]

This change should already be in 1.24 (which should get released soon).

Fyi: here is the commit that updated the spec: https://codereview.chromium.org/2875643002/

[sgrekhov]

@floitschG thank you. I've fixed this issue in co19 master branch. But what about strong mode? What should happen in this case in a strong mode?

[floitschG]

Take the following example:

void foo(A o) => o.bar();

class A { void bar() {} }
class B extends A { int bar() => 499; }

It's completely legal (both in strong and non-strong mode).

Before this change, the checked-mode variant would fail, when foo was given a B as argument. With the change, it simply ignores the value.

In strong mode, the code is correctly typed, and DDC (as well as strong mode) wouldn't even add a check. As such, it should behave the same way.

Currently, DDC does not check for void.

The following example does not raise any errors in DDC.

int bar() { print("in bar"); return 499; }

void foo(Function f) => f();

main() {
  foo(bar);
}

Our general approach is, that void will accept anything dynamically. At runtime, it should basically become just Object. I don't think, we are 100% there yet, though.

@vsmenon, @leafpetersen , in case they have more comments.

[sgrekhov]

@floitschG thank you. I've fixed this issue in a strong mode branch as well. Please note, that this functionality is still not supported by analyzer. I added comment about this to dart-lang/sdk#28935