Some errors on creating getter/setters/mixin at record field

[FMorschel]

Repro:

extension on int {
  (bool, bool, {int v, int v2}) get record => (
    myBool,
    myBool2(),
    v: v,
    v2: v2(),
  );
}

Results:

• On stable, we get Create getter but not on master
• The generated getter/method doesn't calculate the expected return type
• At the non-invocation cases, we also get a Create mixin

I'll take a look into this.

[FMorschel]

Here is the CL https://dart-review.googlesource.com/c/sdk/+/432580

[FMorschel]

FYI @kallentu the above CL works with all of the create method options we currently have if you want to use it as a reference.