Sorbet error suggests using the type that is being used

[dduugg]

Input

→ View on sorbet.run

# typed: true

class Hash
  extend T::Sig
  sig { returns(T.self_type) }
  def compact_blank
    reject { |_k, v| v } # would be v.blank?
  end
end

Observed output

editor.rb:7: Expected T::Hash[Hash::K, Hash::V] but found T::Hash[Hash::K, Hash::V] for method result type https://srb.help/7005
     7 |    reject { |_k, v| v } # would be v.blank?
            ^^^^^^^^^^^^^^^^^^^^
  Expected T::Hash[Hash::K, Hash::V] for result type of method compact_blank:
    editor.rb:6:
     6 |  def compact_blank
          ^^^^^^^^^^^^^^^^^
  Got T::Hash[Hash::K, Hash::V] originating from:
    editor.rb:7:
     7 |    reject { |_k, v| v } # would be v.blank?
            ^^^^^^^^^^^^^^^^^^^^
Errors: 1

Expected behavior

Error message should not be of the form "Expected X but found X for method result type"

---

(I can get around it in this example with a return type of T::Hash[K, V], but that has issues in the production code, and I'd prefer to be able to use T.self_type here.)