.is_a? works with constant values

[Blacksmoke16]

Bug Report

This came up in the Discord and was surprised this even works:

require "http/status"

pp HTTP::Status::OK.is_a? HTTP::Status::OK        # => true
pp HTTP::Status::NOT_FOUND.is_a? HTTP::Status::OK # => false

Or more simply:

NUM = 1
 
pp NUM.is_a? NUM # => true

Is this expected?

[straight-shoota]

Seems odd. I suppose it behaves similar to #==?

[HertzDevil]

Duplicate of #11371?

Apparently the compiler relies on this behavior during expansion of case expressions, and A.is_a?(B) becomes B === A.