Trey Typing

trey_typing.rb

module TreyTyping
  def method_added(name)
    m = instance_method(name)
    file, line = m.source_location
    types = RubyVM::InstructionSequence.disasm(m).lines.slice_before { |l| l['checkkeyword'] }.to_a.drop(1).map { |lines| Object.const_get lines[3].split.last[1..-1] }
    return if file == __FILE__ && line == 1+__LINE__
    define_method name do |*args, **kws|
      kws.zip(types).each do |(name, value), type|
        next if type === value
        raise TypeError, "#{name} should be a #{type}"
      end
      m.bind(self).call(*args, **kws)
    end
  end
end

require 'rspec/autorun'

RSpec.describe 'Trey Typing' do
  extend TreyTyping
  def omg(a: Integer, b: String)
    [a, b]
  end

  it 'can invoke the method with the correct types' do
    expect(omg a: 1, b: 'abc').to eq [1, 'abc']
  end

  it 'explodes if the wrong type is passed' do
    expect { omg a: '1', b: 'abc' }.to raise_error TypeError
  end
end

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