Augmentation libraries: Conflict between super constructor and "The augmentation has an 'extends' clause, but an augmentation target already includes an 'extends' clause" and

[rrousselGit]

Hello!

Consider a macro applied on the following class:

class BaseClass {}

@Macro()
class Example extends BaseClass {}

The macro may want to augment that class with a constructor that uses super.field:

Example(super.field): super.someNamedConstructor();

The issue is twofold:

• Augmentations cannot generate an extends if one is present:

  augment class Example extends BaseClass {
    Example(super.field): super.someNamedConstructor();
  }

  This will produce The augmentation has an 'extends' clause, but an augmentation target already includes an 'extends' clause

• If no extends is specified on the augmentation, then the analyzer seems to fail to find the super.namedConstructor and treat super.field as missing. So the following:

  augment class Example {
   Example(super.field): super.someNamedConstructor();
  }

  Will fail with No associated positional super constructor parameter. Try using a normal parameter, or adding more positional parameters to the super

I assume the problem is that super.someNamedConstructor(); should be able to resolve, by looking at the class definition.

[dart-github-bot]

Summary: Augmenting a class with a constructor that uses super fails due to conflicting extends clauses and the analyzer's inability to resolve super.namedConstructor when no extends is specified in the augmentation. This prevents macros from properly augmenting classes with constructors that utilize inheritance.

[lrhn]

Is a bug. If specified this way, it's a bug in the specification too.

You should be able to add a constructor from scratch. The class it's defined on already has a superclass, even it the current declaration doesn't declare it.

I'd be slighlty more worried about the other direction:

class Example {
  Example(super.field);
}
augment class Example extends BaseClass {}

That one is probably not valid because it's impossible to assign a function signature to the Example constructor declaration.
In the other direction it should work.