Fix literal /es in sass-convert.

Closes #1787

doc-src/SASS_CHANGELOG.md

@@ -11,6 +11,8 @@
 * Make `is-superselector("a > c d", "a > b c d")` return `false`. This also
   fixes some related `@extend` behavior.
 
+* In `sass-convert`, ensure that literal `/`es are preserved.
+
 ## 3.4.16 (10 July 2015)
 
 * When converting from Sass to SCSS or vice versa, double-space around nested

lib/sass/script/tree/list_literal.rb

@@ -28,12 +28,8 @@ def children; elements; end
     # @see Value#to_sass
     def to_sass(opts = {})
       return "()" if elements.empty?
-      precedence = Sass::Script::Parser.precedence_of(separator)
       members = elements.map do |v|
-        if v.is_a?(ListLiteral) && Sass::Script::Parser.precedence_of(v.separator) <= precedence ||
-            separator == :space && v.is_a?(UnaryOperation) &&
-              (v.operator == :minus || v.operator == :plus) ||
-            separator == :space && v.is_a?(Operation)
+        if element_needs_parens?(v)
           "(#{v.to_sass(opts)})"
         else
           v.to_sass(opts)
@@ -69,6 +65,32 @@ def _perform(environment)
 
     private
 
+    # Returns whether an element in the list should be wrapped in parentheses
+    # when serialized to Sass.
+    def element_needs_parens?(element)
+      if element.is_a?(ListLiteral)
+        return Sass::Script::Parser.precedence_of(element.separator) <=
+               Sass::Script::Parser.precedence_of(separator)
+      end
+
+      return false unless separator == :space
+
+      if element.is_a?(UnaryOperation)
+        return element.operator == :minus || element.operator == :plus
+      end
+
+      return false unless element.is_a?(Operation)
+      return true unless element.operator == :div
+      !(is_literal_number?(element.operand1) && is_literal_number?(element.operand2))
+    end
+
+    # Returns whether a value is a number literal that shouldn't be divided.
+    def is_literal_number?(value)
+      value.is_a?(Literal) &&
+        value.value.is_a?((Sass::Script::Value::Number)) &&
+        !value.value.original.nil?
+    end
+
     def sep_str(opts = options)
       return ' ' if separator == :space
       return ',' if opts && opts[:style] == :compressed

test/sass/conversion_test.rb

@@ -1296,6 +1296,16 @@ def test_literal_slash
 foo {
   a: 1px / 2px;
 }
+SCSS
+
+    # Regression test for issue 1787
+    assert_renders <<SASS, <<SCSS
+foo
+  a: 1px / 2px 3px
+SASS
+foo {
+  a: 1px / 2px 3px;
+}
 SCSS
   end