commit e92bd978ad72d35fc61b62a7c0e3296fe3738663
author Dmitry Stefantsov <dmitryas@google.com> Tue Jun 25 08:02:46 2019 +0000
committer commit-bot@chromium.org <commit-bot@chromium.org> Tue Jun 25 08:02:46 2019 +0000
tree a5169d04e60a57025f8daeee8fc4018880765dca
parent f2b31269842eb4e0facbb8000fff5f70a7f3e5c9

Fix 'covariant' bit propagation in mixin applications

In the upstream CL https://dart-review.googlesource.com/c/sdk/+/100580 the
'covariant' bit on parameters of class methods isn't propagated correctly in the
case of mixins.  Effectively, if it's used in a member of the superclass of the
mixin application, it won't be propagated to the mixin application or its
subclasses.  Consider the following:

```
class A {
  void foo(covariant num x) {}
}

class B {
  void foo(num x) {}
}

class C {
  void foo(num x) {}
}

class D extends A with B implements C {
  void foo(int x) {}
}
```

The program above doesn't have any errors, and overriding foo in D using int as
the type of the parameter is allowed, because D's superclass A declares the
parameter as 'covariant'.  Without the changes from this CL, the code will
result in a compile-time error.  With the change, the 'covariant' bit is
propagated correctly, and the program compiles.

An existing test already covers the described behavior: see class Mixed in
tests/language_2/covariant_override/tear_off_type_test.dart.

Change-Id: Ia508a224527c95f5ef04c1f1fb02614f8ff43714
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/101284
Reviewed-by: Aske Simon Christensen <askesc@google.com>