error with redirecting constructors + optional args + mixins

[sigmundch]

This program behaves differently if you run it in the VM or with dart2js:

    class A {}
    
    class B extends A {
      B([x]);
    }
    
    class C extends B with A {
      C() : super(0);
    }
    
    main() => print(new C());

The VM fails with this error:

    'file:///home/sigmund/playground/dart_tests/fwderror.dart': error: line 7 pos 24: forwarding constructors must not have optional parameters
    class C extends B with A {
                           ^

And dart2js successfully compiles and runs it. I believe the dart2js behavior is the correct one in this case.

[iposva-google]

Set owner to @crelier.
Added Accepted label.

[sigmundch]

Just chatting with Emily, and she pointed out that there might be a couple language bugs related to this, so I'm not sure what the right action is anymore.

Here are the other relevant bugs:
  - https://code.google.com/p/dart/issues/detail?id=17610
  - https://code.google.com/p/dart/issues/detail?id=15101

[iposva-google]

The one thing that makes me wonder is: Why does dart2js allow this?

---

Set owner to @gbracha.
Removed Area-VM label.
Added Area-Language label.

[crelier]

See also issues 15101 and 17610.
Improved error message suggesting workaround submitted as r37057.

[lrhn]

Most likely reason for dart2js to allow it: They didn't realize that there was this unexpected and unnecessary limitation.

[gbracha]

Added Duplicate label.
Marked as being merged into #15101.