Include type_parameters declarations in signatures

[dejmedus]

• closes Generated RBI signatures missing type_parameters declaration #2542

Motivation

Previously, when a compiler used create_method_from_def (ex. ActiveSupportCurrentAttributes) any method signatures would be generated without type_parameters declarations. This created invalid signatures when type params were used in the method sig

- sig { params(a: T.type_parameter(:U)).returns(T.type_parameter(:U)) }
+ sig { type_parameters(:U).params(a: T.type_parameter(:U)).returns(T.type_parameter(:U)) }

Implementation

This PR moves out TYPE_PARAMETER_MATCHER and the type param extraction logic from gem sorbet_signatures.rb file to rbi_helper.rb so that they can also be used by dsl. This way create_method_from_def can pass any type params to create_method so that RBI::Sig.new will be able to include them in the generated signature

Tests

• in compiler_spec.rb compiles a class with methods that have signatures:
  • updated a case to add type_parameters declaration
  • added new case to test more complex type param use
• added a method with type params to active_support_current_attributes_spec.rb copies types from instance methods to class methods

[paracycle]

I'd missed this PR earlier, so sorry for the delayed review, but it seems like this functionality should be a part of the inner working of create_method or RBI::Sig construction, since all the inputs to this method seem to always be params and return_type.

I suggest:

1. Reverting the signature of create_method to remove the type_params parameter
2. Adding a public method to RBI::Sig for doing this calculation and for setting type_params. Something like set_type_params_from_params. Btw, we don't need to pass return_type to that calculation since there is no way that we can have a type param only in the out position, that means the signature is broken in the first place.
3. Making create_method method call this method on the created sig after constructing it.

[dejmedus]

Just saw you beat me to this, thank you! (+ thank you for the detailed feedback)

Btw, we don't need to pass return_type to that calculation since there is no way that we can have a type param only in the out position, that means the signature is broken in the first place.

Ah, that makes sense

[paracycle]

I still left the return type in, just in case, so that we don't end up generating broken signatures, even if the signature itself would be meaningless like that.