Include "self type" methods like Enumerable#each from RBS files #769
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RBS has the concept of a 'self type', which is a way to refer to the requirements a class must implement in order to use a mix-in. An example would be the 'each' method, which you must implement before you can import 'Enumerable'. The implication of this is that is it reasonably safe to assume that anything that includes Enumerable will have this method, which allows 'Enumerable' to be treated as a de-facto superclass of concrete container classes like 'Hash', 'Set' and 'Array' and allow methods to depend on the Enumerable abstract interface and accept a variety of container types. With this change, we assume that if we receive something with type X, it implements all of its self types. As a result, we won't see typechecking errors when e.g. using #each on an Enumerable. A future typechecking improvement would double check that the concrete class does implement the self type interface when the receiving type requires it.
apiology
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Combined with castwide#769, this allows the _Each#each self-type-method block's parameter to be typed. This also sets the stage for future generic references (e.g., subclassing Array<T>).
castwide
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Mar 15, 2025
* Add support for generic includes via RBS Combined with #769, this allows the _Each#each self-type-method block's parameter to be typed. This also sets the stage for future generic references (e.g., subclassing Array<T>). * Make code Ruby 2.6 compatible * Fix bugs found during use
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RBS has the concept of a 'self type', which is a way to refer to the requirements a class must implement in order to use a mix-in. An example would be the 'each' method, which you must implement before you can import 'Enumerable'.
The implication of this is that is it reasonably safe to assume that anything that includes Enumerable will have this method, which allows 'Enumerable' to be treated as a de-facto superclass of concrete container classes like 'Hash', 'Set' and 'Array' and allow methods to depend on the Enumerable abstract interface and accept a variety of container types.
With this change, we assume that if we receive something with type X, it implements all of its self types. As a result, we won't see typechecking errors when e.g. using #each on an Enumerable.
A future typechecking improvement would double check that the concrete class does implement the self type interface when the receiving type requires it.