lib/kind.rb in kind-1.0.0 vs lib/kind.rb in kind-1.1.0

@@ -1,10 +1,12 @@
 # frozen_string_literal: true
 
 require 'kind/version'
 
 module Kind
+  Undefined = Object.new
+
   class Error < TypeError
     def initialize(klass, object)
       super("#{object.inspect} expected to be a kind of #{klass}")
     end
   end
@@ -45,12 +47,12 @@
       return object if object.is_a?(klass)
 
       raise Kind::Error.new((name || klass.name), object)
     end
 
-    def self.Class(object = nil)
-      return Class if object.nil?
+    def self.Class(object = Undefined)
+      return Class if object == Undefined
 
       self.call(::Class, object)
     end
 
     const_set(:Class, ::Module.new do
@@ -61,12 +63,12 @@
       def self.class?(value); Kind::Is.Class(value); end
 
       def self.instance?(value); class?(value); end
     end)
 
-    def self.Module(object = nil)
-      return Module if object.nil?
+    def self.Module(object = Undefined)
+      return Module if object == Undefined
 
       self.call(::Module, object)
     end
 
     const_set(:Module, ::Module.new do
@@ -84,22 +86,22 @@
     extend self
 
     COLONS = '::'.freeze
 
     KIND_OF = <<-RUBY
-      def self.%{method_name}(object = nil, options = {})
+      def self.%{method_name}(object = Undefined, options = {})
         default = options[:or]
 
-        return Kind::Of::%{kind_name} if object.nil? && default.nil?
+        return Kind::Of::%{kind_name} if object == Undefined && default.nil?
 
         Kind::Of.(::%{kind_name}, (object || default), name: "%{kind_name}".freeze)
       end
     RUBY
 
     KIND_IS = <<-RUBY
-      def self.%{method_name}(value = nil)
-        return Kind::Is::%{kind_name} if value.nil?
+      def self.%{method_name}(value = Undefined)
+        return Kind::Is::%{kind_name} if value == Undefined
 
         Kind::Is.(::%{kind_name}, value)
       end
     RUBY
 
@@ -200,14 +202,14 @@
   end
 
   module Of
     # -- Boolean
 
-    def self.Boolean(object = nil, options = {})
+    def self.Boolean(object = Undefined, options = {})
       default = options[:or]
 
-      return Kind::Of::Boolean if object.nil? && default.nil?
+      return Kind::Of::Boolean if object == Undefined && default.nil?
 
       bool = object.nil? ? default : object
 
       return bool if bool.is_a?(::TrueClass) || bool.is_a?(::FalseClass)
 
@@ -226,13 +228,13 @@
       end
     end)
 
     # -- Lambda
 
-    def self.Lambda(object = nil, options = {})
+    def self.Lambda(object = Undefined, options = {})
       default = options[:or]
 
-      return Kind::Of::Lambda if object.nil? && default.nil?
+      return Kind::Of::Lambda if object == Undefined && default.nil?
 
       func = object || default
 
       return func if func.is_a?(::Proc) && func.lambda?