Anonymous modules within a module body are recognized as the part of the module

[palkan]

Input

→ View on sorbet.run

# typed: true

module A
  M = Module.new do
    def empty?
      false
    end
  end

  def empty?(val)
    val.empty?
  end
end

Observed output

editor.rb:10: Method A#empty? redefined without matching argument count. Expected: 0, got: 1 https://srb.help/4010
    10 |  def empty?(val)
          ^^^^^^^^^^^^^^^
    editor.rb:5: Previous definition
     5 |    def empty?
            ^^^^^^^^^^
Errors: 1

Expected behavior

No errors.

---

The provided example is the minimal reproduction.
The real-world example involved using(Module.new do ... end) and could be found here: https://github.com/palkan/rubanok/blob/b4431ac1e13600036315472f863a345675522677/lib/rubanok/rule.rb#L47-L65

[DarkDimius]

Thank you for a great issue report with a great reproducer!
For those interested to contribute, this should be super easy to fix:
https://github.com/sorbet/sorbet/blob/master/dsl/ClassNew.cc is already handling Class.new, it should additionally handle Module.new.

[JoshCheek]

The general case for this is going to be super tricky, If you see a def in a block, it's unclear what it is defined on since that can change at run time. Eg:

M1 = Module.new do
  def empty?
    'first'
  end
end

def Module.new(&b)
  b.call
  allocate
end

M2 = Module.new do
  def empty?
    'second'
  end
end

Object.new.extend(M1).empty? # => "first"
empty?                       # => "second"
Object.new.extend(M2).empty? # => NoMethodError: private method `empty?' called for #<Object:0x00007f8098169cf0>

[searls]

This is also true of anonymous classes, and is preventing me from enabling types for one of the critical sections of Mocktail.

Here's a repro:

# typed: true

class ClassMaker
  def initialize
    # Initializing ClassMaker
  end

  def make
    Class.new(Object) {
      def initialize(*args, **kwargs, &blk)
        # Initializing Some totally unrelated class
      end
    }
  end
end

class_maker.rb:10: Method ClassMaker#initialize redefined without matching argument count. Expected: 0, got: 2 https://srb.help/4010
    10 |      def initialize(*args, **kwargs, &blk)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    class_maker.rb:4: Previous definition
     4 |  def initialize
          ^^^^^^^^^^^^^^