[Sass] Add the type-of() sass function to inspect the data type of values.

doc-src/SASS_CHANGELOG.md

@@ -5,6 +5,14 @@
 
 ## 3.0.0.beta.2 (Unreleased)
 
+### New Sass Functions for Introspection
+
+Several new functions were added to make it easier to have
+more flexible arguments to mixins and to enable deprecation
+of obsolete APIs.
+
+* `type-of` -- Returns the type of a value.
+
 ### `@warn`
 
 A new directive `@warn` has been added that allows sass libraries to emit warnings. This can be used to issue deprecation warnings, discourage sloppy coding, etc.

lib/sass/script/functions.rb

@@ -105,6 +105,11 @@ module Sass::Script
   # \{#abs}
   # : Returns the absolute value of a number.
   #
+  # ## Introspection Functions
+  #
+  # \{#type_of}
+  # : Returns the type of a value.
+  #
   # These functions are described in more detail below.
   #
   # ## Adding Custom Functions
@@ -669,6 +674,22 @@ module Sass::Script
       Sass::Script::String.new(str.value, :string)
     end
 
+    # Inspects the type of the argument, returning it as an unquoted string.
+    # For example:
+    #
+    #     type-of(100px)  => number
+    #     type-of(asdf)   => string
+    #     type-of("asdf") => string
+    #     type-of(true)   => bool
+    #     type-of(#fff)   => color
+    #     type-of(blue)   => color
+    #
+    # @param obj [Literal] The object to inspect
+    # @return [String] The unquoted string value of the literal's type
+    def type_of(obj)
+      Sass::Script::String.new(obj.class.name.gsub(/Sass::Script::/,'').downcase)
+    end
+
     # Converts a decimal number to a percentage.
     # For example:
     #

test/sass/functions_test.rb

@@ -505,6 +505,14 @@ The #options attribute is not set on this Sass::Script::String.
 MSG
   end
 
+  def test_type_of
+    assert_equal("string", evaluate("type-of(\"asdf\")"))
+    assert_equal("string", evaluate("type-of(asdf)"))
+    assert_equal("number", evaluate("type-of(1px)"))
+    assert_equal("bool", evaluate("type-of(true)"))
+    assert_equal("color", evaluate("type-of(#fff)"))
+  end
+
   private
 
   def evaluate(value)