Avoid repeating default values for super parameters

[goderbauer]

If the default values for super parameters in a subclass are the same as in the super class, they don't have to be repeated as they will be copied from the super constructor. A lint could remind people that the repetition is unnecessary to keep it DRY.

Examples

Bad:

class Bar extends Foo {
  Bar({super.value = true}); // Lint on this line that "= true" isn't necessary.
}

class Foo {
  Foo({this.value = true});
  final bool value;
}

Good:

class Bar extends Foo {
  Bar({super.value}); 
}

class Foo {
  Foo({this.value = true});
  final bool value;
}

Also ok:

class Bar extends Foo {
  Bar({super.value = false}); // Don't lint because the default was changed.
}

class Foo {
  Foo({this.value = true});
  final bool value;
}

Additional context
Rules about copying the default value from the associated super-constructor: https://github.com/dart-lang/language/blob/master/working/1855%20-%20super%20parameters/proposal.md#parameter-types-and-default-values

[pq]

I wonder if extending avoid_redundant_argument_values to handle the super parameter case would be sufficient?

[pq]

Looking a bit closer, this lint currently is only about invocations and leaves redundancy in declarations well enough alone.

If we want to extend it, should we consider cases like this too?

class A {
  int a = 0;
  A([this.a = 0]);
}

[goderbauer]

I think it would make sense to split invocations and declarations into separate lints (not feeling super strongly about this, though). The declaration one could also include the case you mentioned above.

[pq]

I'm leaning that way too. Maybe:

• avoid_redundant_default_values, or
• no_redundant_default_values

[bwilkerson]

I agree that a separate lint is better, and I like the second suggested name better.

[pq]

Closing this in favor of a proposal in #58702.

Thanks @goderbauer!