Add support for regexp matching

README.md

@@ -185,6 +185,23 @@ TODO: fill out this section.
 
 TODO: fill out this section.
 
+### `ShapeOf::Regexp`
+
+The `ShapeOf::Regexp[/regexp pattern/]` is used to match either `Regexp`s as equal or to match a `Regexp` against a `String` using `Regexp#match?`.
+```ruby
+shape = ShapeOf::Regexp[/foobar$/i]
+
+shape.shape_of?("foobar") # => true
+shape.shape_of?(/foobar$/i) # => true
+shape.shape_of?("fOobAr\n") # => true
+shape.shape_of?("\n\nfoobar\n") # => true
+shape.shape_of?("foo\nbarfoo\nfoobar\nfo\nobar\n") # => true
+shape.shape_of?("There once was a barfoo who foobared. Foobar") # => true
+shape.shape_of?(/foobar$/) # => false
+shape.shape_of?(/foobar/i) # => false
+shape.shape_of?("foo\nbar\n") # => false
+```
+
 ### `ShapeOf::Boolean`
 
 TODO: fill out this section.

lib/shape_of.rb

@@ -316,6 +316,47 @@ def self.required?
     end
   end
 
+  class Regexp < Shape
+    @internal_class = ::Regexp 
+
+    def self.shape_of?(object)
+      object.instance_of? @internal_class
+    end
+
+    def self.[](shape)
+      raise TypeError, "Shape must be #{::Regexp.inspect}, was #{shape.inspect}" unless shape.instance_of? ::Regexp
+
+      Class.new(self) do
+        @class_name = "#{superclass.name}[#{shape.inspect}]"
+        @shape = shape
+
+        def self.name
+          @class_name
+        end
+
+        def self.to_s
+          @class_name
+        end
+
+        def self.inspect
+          @class_name
+        end
+
+        def self.shape_of?(object)
+          unless object.instance_of?(::Regexp) || object.instance_of?(String)
+            raise TypeError, "expected #{::Regexp.inspect} or #{String.inspect}, was instead #{object.inspect}"
+          end
+
+          if object.instance_of?(::Regexp)
+            @shape == object
+          else # string
+            @shape.match?(object)
+          end
+        end
+      end
+    end
+  end
+
   Numeric = Union[Integer, Float, Rational, Complex].tap do |this|
     this.instance_variable_set(:@class_name, this.name.sub(/Union.*/, 'Numeric'))
   end

test/test_shape_of.rb

@@ -66,6 +66,11 @@ def test_nothing_is_defined
     assert_equal Class, ShapeOf::Nothing.class
   end
 
+  def test_regexp_is_defined
+    assert_equal "constant", defined? ShapeOf::Regexp
+    assert_equal Class, ShapeOf::Regexp.class
+  end
+
   def test_numeric_is_defined
     assert_equal "constant", defined? ShapeOf::Numeric
     assert_equal Class, ShapeOf::Numeric.class
@@ -279,6 +284,22 @@ def test_nothing_with_hash
     refute_shape_of_many shape, [{ foo: nil }, { foo: :bar }, { hello: "world" }, [{}]]
   end
 
+  # Regexp
+
+  def test_regexp
+    assert_operator ShapeOf::Regexp, :respond_to?, :required?
+    assert_predicate ShapeOf::Regexp, :required?
+    assert_raises(TypeError) { ShapeOf::Regexp['foobar'] }
+    assert_raises(TypeError) { ShapeOf::Regexp[/foobar/].shape_of?(['hello']) }
+
+    assert_shape_of_many ShapeOf::Regexp, [/foo/, //, /bar/, /bz/imx, Regexp.new('foobadfaejralj')]
+    refute_shape_of_many ShapeOf::Regexp, [nil, true, false, '', '/foobar/']
+    assert_shape_of_many ShapeOf::Regexp[/foobar/], [/foobar/, 'foobar', "\n\nfoobar\n\n", /foobar/.to_s, "qwertyuiopasdfghjklzxcvbnmfoobarqwertyuioopasdfghjklzxcvbnm"]
+    refute_shape_of_many ShapeOf::Regexp[/foobar/], [/fobar/, 'fobar', '']
+    assert_shape_of_many ShapeOf::Regexp[/^whoa/i], [/^whoa/i, 'whoa there', 'WHOA there!', "whoa hello\nwhoa there\nwhoa whoa!"]
+    refute_shape_of_many ShapeOf::Regexp[/^whoa/i], [/whoa/, 'hey, whoa there', " WHOA there!"]
+  end
+
   # Numeric
 
   def test_numeric