Show the T.attached_class specificity note when the attached class is inside something else

[neilparikh]

Input

→ View on sorbet.run

# typed: true
extend T::Sig

class A
  extend T::Sig

  sig {returns(T.attached_class)}
  def self.make
    A.new
  end
end

class B
  extend T::Sig

  sig {returns(T::Array[T.attached_class])}
  def self.make
    B.new
  end
end

Observed output

editor.rb:9: Expected T.attached_class (of A) but found A for method result type https://srb.help/7005
     9 |    A.new
            ^^^^^
  Expected T.attached_class (of A) for result type of method make:
    editor.rb:8:
     8 |  def self.make
          ^^^^^^^^^^^^^
  Got A originating from:
    editor.rb:9:
     9 |    A.new
            ^^^^^
  Note:
    A is incompatible with T.attached_class (of A) because when this method is called on a subclass T.attached_class (of A) will represent a more specific subclass, meaning A will not be specific enough. See https://sorbet.org/docs/attached-class for more.

editor.rb:18: Expected T::Array[T.attached_class (of B)] but found B for method result type https://srb.help/7005
    18 |    B.new
            ^^^^^
  Expected T::Array[T.attached_class (of B)] for result type of method make:
    editor.rb:17:
    17 |  def self.make
          ^^^^^^^^^^^^^
  Got B originating from:
    editor.rb:18:
    18 |    B.new
            ^^^^^
Errors: 2

Expected behavior

The note about attached class for A should also appear for B.

It would also be nice to recommend to the user that they can replace A.new with self.new if we can detect that.

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