Add VarNode class for lvar, ivar, cvar and gvar node types

[dvandersluis]

Adds node classes for variables, to have symmetry with the assignment nodes. eg. a lvasgn and lvar for the same variable should have the same value for the #name method.

[dvandersluis]

CasgnNode and Const should have a symmetrical interface so that they can be compared (eg. in Lint/SelfAssignment).

[marcandre]

Sounds good, but maybe the best would be to simply move all the implementation of Const to a module and include this here too?

[dvandersluis]

@marcandre CI is failing on https://github.com/rubocop/rubocop/blob/345be1d50c6f44b8ae1a880f490d5faa1f368945/spec/rubocop/cop/metrics/utils/abc_size_calculator_spec.rb#L345-L360

because of

https://github.com/rubocop/rubocop/blob/2fe4b1a6faca23adff13e1bbff6ecf5b66c6447b/lib/rubocop/cop/metrics/utils/repeated_attribute_discount.rb#L129

Now lvar returns a VarNode, but RepeatedAttributeDiscount uses s(:lvar, ...) which returns a Node, and then it's not considered correctly.

Any ideas?

[marcandre]

Any ideas?

Sorry, that's my code 😅 .
It could be adapted so that it creates the right type of node, base on the existence of VarNode or not...?
Or change the test to compare [type, name] instead of the nodes directly.

[dvandersluis]

Is there a way we can update s to return the right class instead of Node for all node types? That probably would be the "best" solution IMO.

It could be adapted so that it creates the right type of node, base on the existence of VarNode or not...?

Do you mean something like:

if defined?(RuboCop::AST::VarNode) ? RuboCop::AST::VarNode.new(...) : s(...)

Or change the test to compare [type, name] instead of the nodes directly.

I don't think we can do this because I think the issue is this fetch: https://github.com/rubocop/rubocop/blob/2fe4b1a6faca23adff13e1bbff6ecf5b66c6447b/lib/rubocop/cop/metrics/utils/repeated_attribute_discount.rb#L114

I've had a little trouble tracing what's happening in that class though so I may be offbase.