Idea for some syntactic sugar

README.md

@@ -10,14 +10,21 @@ def sum(x, y)
 end
 typesig :sum, [Numeric, Numeric] => String
 
+# This type definition can also be written like this:
+
+require 'rubype/syntactic_sugar'
+[Numeric, Numeric, String] > def sum(x, y)
+  (x + y).to_s
+end
+
+
 # Assert first arg has method #to_i
 def sum(x, y)
   x.to_i + y
 end
 typesig :sum, [:to_i, Numeric] => Numeric
 ```
 
-
 This gem brings you advantage of type without changing existing code's behavior.
 
 ## Good point:

lib/rubype/syntactic_sugar.rb

@@ -0,0 +1,20 @@
+require 'binding_of_caller'
+
+class Array
+  def >(*args)
+    args_match = args.length == 1 && args.first.kind_of?(Symbol)
+    self_matches = length > 0 && all? { |e| e.kind_of?(Class) }
+
+    if args_match && self_matches
+      return_type = self.last
+      call_string = "typesig :#{args.first}, [#{self[0...-1].map(&:name).join(', ')}] => #{return_type}"
+      binding.of_caller(1).eval(call_string)
+    else
+      if !args_match
+        raise "You must pass a Symbol as the only argument to a type definition!"
+      else
+        raise "Wrong type definition #{self}"
+      end
+    end
+  end
+end

rubype.gemspec

@@ -20,6 +20,8 @@ Gem::Specification.new do |spec|
 
   spec.required_ruby_version = ">= 2.0.0"
 
+  spec.add_runtime_dependency "binding_of_caller", "~> 0.7.2"
+
   spec.add_development_dependency "bundler", "~> 1.3"
   spec.add_development_dependency "rake"
   spec.add_development_dependency "minitest"

test/minitest_helper.rb

@@ -1,4 +1,5 @@
 $LOAD_PATH.unshift File.expand_path('../../lib', __FILE__)
 require 'rubype'
+require 'rubype/syntactic_sugar'
 require 'pry'
 require 'minitest/autorun'

test/test_rubype.rb

@@ -95,18 +95,17 @@ def test_mth(n1, n2)
       end
       typesig :test_mth, [Numeric, Numeric] => String
     RUBY_CODE
-    Object.const_set('MyClass', klass)
 
-    meth = klass.new.method(:test_mth)
-    assert_equal meth.type_info, { [Numeric, Numeric] => String }
-    assert_equal meth.arg_types, [Numeric, Numeric]
-    assert_equal meth.return_type, String
+    assert_correct_checks_on_class(klass)
+  end
 
-    err = assert_raises(Rubype::ReturnTypeError) { meth.(1,2) }
-    assert_equal err.message, %|Expected MyClass#test_mth to return String but got nil instead|
+  def test_type_info_syntactic_sugar
+    klass = Class.new.class_eval <<-RUBY_CODE
+      [Numeric, Numeric, String] > def test_mth(n1, n2)
+      end
+    RUBY_CODE
 
-    err = assert_raises(Rubype::ArgumentTypeError) { meth.(1,'2') }
-    assert_equal err.message, %|Expected MyClass#test_mth's 2nd argument to be Numeric but got "2" instead|
+    assert_correct_checks_on_class(klass)
   end
 
   private
@@ -126,6 +125,22 @@ def assert_wrong_rtn(type_list, args, val)
       assert_raises(Rubype::ReturnTypeError) { define_test_method(type_list, args, val).call(*args) }
     end
 
+    def assert_correct_checks_on_class(klass)
+      Object.send(:remove_const, 'MyClass') if defined? MyClass
+      Object.const_set('MyClass', klass)
+
+      meth = klass.new.method(:test_mth)
+      assert_equal meth.type_info, { [Numeric, Numeric] => String }
+      assert_equal meth.arg_types, [Numeric, Numeric]
+      assert_equal meth.return_type, String
+
+      err = assert_raises(Rubype::ReturnTypeError) { meth.(1,2) }
+      assert_equal err.message, %|Expected MyClass#test_mth to return String but got nil instead|
+
+      err = assert_raises(Rubype::ArgumentTypeError) { meth.(1,'2') }
+      assert_equal err.message, %|Expected MyClass#test_mth's 2nd argument to be Numeric but got "2" instead|
+    end
+
     def define_test_method(type_list, args, val)
       klass = Class.new.class_eval <<-RUBY_CODE
         def call(#{arg_literal(args.count)})