[Sass] Allow mixin argument defaults to use : rather than =.

lib/sass/script/lexer.rb

@@ -45,6 +45,7 @@ module Sass
         '/' => :div,
         '%' => :mod,
         '=' => :single_eq,
+        ':' => :colon,
         '(' => :lparen,
         ')' => :rparen,
         ',' => :comma,

lib/sass/script/parser.rb

@@ -226,8 +226,9 @@ RUBY
       def defn_arglist(must_have_default)
         return unless c = try_tok(:const)
         var = Script::Variable.new(c.value)
-        if try_tok(:single_eq)
+        if tok = (try_tok(:colon) || try_tok(:single_eq))
           val = assert_expr(:concat)
+          val.context = :equals if tok.type == :single_eq
         elsif must_have_default
           raise SyntaxError.new("Required argument #{var.inspect} must come before any optional arguments.")
         end

lib/sass/tree/mixin_def_node.rb

@@ -23,7 +23,7 @@ module Sass
           else
             '(' + @args.map do |v, d|
               if d
-                "#{v.to_sass} = #{d.to_sass}"
+                "#{v.to_sass}: #{d.to_sass}"
               else
                 v.to_sass
               end

test/sass/conversion_test.rb

@@ -708,14 +708,34 @@ SCSS
 
   def test_mixin_definition_with_defaults
     assert_renders <<SASS, <<SCSS
-=foo-bar($baz, $bang = 12px)
+=foo-bar($baz, $bang: 12px)
   baz
     a: $baz $bang
 SASS
-@mixin foo-bar($baz, $bang = 12px) {
+@mixin foo-bar($baz, $bang: 12px) {
   baz {
     a: $baz $bang; } }
 SCSS
+
+    assert_scss_to_sass <<SASS, <<SCSS
+=foo-bar($baz, $bang: foo)
+  baz
+    a: $baz $bang
+SASS
+@mixin foo-bar($baz, $bang = "foo") {
+  baz {
+    a: $baz $bang; } }
+SCSS
+
+    assert_sass_to_scss <<SCSS, <<SASS
+@mixin foo-bar($baz, $bang: foo) {
+  baz {
+    a: $baz $bang; } }
+SCSS
+=foo-bar($baz, $bang = "foo")
+  baz
+    a: $baz $bang
+SASS
   end
 
   def test_argless_mixin_include