[Slash Separator] Parse / as a separator rather than a division operator (#2649)

Closes #663

Author: nex3

CHANGELOG.md

@@ -1,5 +1,9 @@
 ## 2.0.0
 
+* **Breaking change:** `/` is now used for slash-separated lists rather than
+  division in SassScript. You can still use it for division within `calc()` and
+  other calculation expressions, or use `math.div()` instead.
+
 * **Breaking change:** `@elseif` is no longer treated as equivalent to `@else
   if`, and is now treated like any other unknown plain CSS at-rule.
 

lib/src/ast/sass/expression/binary_operation.dart

@@ -24,13 +24,6 @@ final class BinaryOperationExpression extends Expression {
   /// The right-hand operand.
   final Expression right;
 
-  /// Whether this is a [BinaryOperator.dividedBy] operation that may be
-  /// interpreted as slash-separated numbers.
-  ///
-  /// @nodoc
-  @internal
-  final bool allowsSlash;
-
   FileSpan get span {
     // Avoid creating a bunch of intermediate spans for multiple binary
     // expressions in a row by moving to the left- and right-most expressions.
@@ -57,17 +50,7 @@ final class BinaryOperationExpression extends Expression {
           .trim()
       : span;
 
-  BinaryOperationExpression(this.operator, this.left, this.right)
-      : allowsSlash = false;
-
-  /// Creates a [BinaryOperator.dividedBy] operation that may be interpreted as
-  /// slash-separated numbers.
-  ///
-  /// @nodoc
-  @internal
-  BinaryOperationExpression.slash(this.left, this.right)
-      : operator = BinaryOperator.dividedBy,
-        allowsSlash = true;
+  BinaryOperationExpression(this.operator, this.left, this.right);
 
   T accept<T>(ExpressionVisitor<T> visitor) =>
       visitor.visitBinaryOperationExpression(this);
@@ -151,6 +134,10 @@ enum BinaryOperator {
   times('times', '*', 6, associative: true),
 
   /// The division operator, `/`.
+  ///
+  /// **Note:** This is never directly parsed by the Sass stylesheet. It's only
+  /// ever generated at runtime by reorienting the precedence of slash-separated
+  /// lists.
   dividedBy('divided by', '/', 6),
 
   /// The modulo operator, `%`.

lib/src/deprecation.dart

@@ -15,7 +15,7 @@ enum Deprecation {
   // DO NOT EDIT. This section was generated from the language repo.
   // See tool/grind/generate_deprecations.dart for details.
   //
-  // Checksum: 0be67f32391e119205f8e98cd15fa8e7382b6dd2
+  // Checksum: da3a1fd53f628e2633aef3b7560951c00d48e1a1
 
   /// Deprecation for passing a string directly to meta.call().
   callString('call-string',
@@ -51,7 +51,9 @@ enum Deprecation {
 
   /// Deprecation for / operator for division.
   slashDiv('slash-div',
-      deprecatedIn: '1.33.0', description: '/ operator for division.'),
+      deprecatedIn: '1.33.0',
+      obsoleteIn: '2.0.0',
+      description: '/ operator for division.'),
 
   /// Deprecation for leading, trailing, and repeated combinators.
   bogusCombinators('bogus-combinators',
@@ -145,6 +147,10 @@ enum Deprecation {
       deprecatedIn: '1.91.0',
       description: 'A rest parameter before a positional or named parameter.'),
 
+  /// Deprecation for the list.slash() function.
+  listSlash('list-slash',
+      deprecatedIn: '2.0.0', description: 'The list.slash() function.'),
+
   // END AUTOGENERATED CODE
 
   /// Used for deprecations coming from user-authored code.

lib/src/functions/color.dart

@@ -11,7 +11,6 @@ import '../deprecation.dart';
 import '../evaluation_context.dart';
 import '../exception.dart';
 import '../module/built_in.dart';
-import '../parse/scss.dart';
 import '../util/map.dart';
 import '../util/nullable.dart';
 import '../util/number.dart';
@@ -1806,34 +1805,9 @@ Value _parseChannels(
           "${pluralize('was', inputList.length, plural: 'were')} passed.",
           name,
         ),
-      [...var initial, SassString(hasQuotes: false, :var text)] => switch (
-            text.split('/')) {
-          [_] => (input, null),
-          [var channel3, var alpha] => (
-              SassList([
-                ...initial,
-                _parseNumberOrString(channel3),
-              ], ListSeparator.space),
-              _parseNumberOrString(alpha),
-            ),
-          _ => null,
-        },
-      [...var initial, SassNumber(asSlash: (var before, var after))] => (
-          SassList([...initial, before], ListSeparator.space),
-          after,
-        ),
       _ => (input, null),
     };
 
-/// Parses [text] as either a Sass number or an unquoted Sass string.
-Value _parseNumberOrString(String text) {
-  try {
-    return ScssParser(text).parseNumber();
-  } on SassFormatException {
-    return SassString(text, quotes: false);
-  }
-}
-
 /// Creates a [SassColor] for the given [space] from the given channel values,
 /// or throws a [SassScriptException] if the channel values are invalid.
 ///

lib/src/functions/list.dart

@@ -7,6 +7,8 @@ import 'dart:collection';
 import 'package:collection/collection.dart';
 
 import '../callable.dart';
+import '../deprecation.dart';
+import '../evaluation_context.dart';
 import '../exception.dart';
 import '../module/built_in.dart';
 import '../value.dart';
@@ -152,6 +154,14 @@ final _isBracketed = _function(
 );
 
 final _slash = _function("slash", r"$elements...", (arguments) {
+  warnForDeprecation(
+    'list.slash() is no longer necessary. Sass now supports slash-separated '
+    'list literals.\n'
+    'This function is deprecated and will be removed in Dart 3.0.0.\n'
+    'More info and automated migrator: https://sass-lang.com/d/slash-div',
+    Deprecation.listSlash,
+  );
+
   var list = arguments[0].asList;
   if (list.length < 2) {
     throw SassScriptException("At least two elements are required.");

lib/src/functions/math.dart

@@ -257,16 +257,8 @@ final _randomFunction = _function("random", r"$limit: null", (arguments) {
 });
 
 final _div = _function("div", r"$number1, $number2", (arguments) {
-  var number1 = arguments[0];
-  var number2 = arguments[1];
-
-  if (number1 is! SassNumber || number2 is! SassNumber) {
-    warn(
-      "math.div() will only support number arguments in a future release.\n"
-      "Use list.slash() instead for a slash separator.",
-    );
-  }
-
+  var number1 = arguments[0].assertNumber('number1');
+  var number2 = arguments[1].assertNumber('number2');
   return number1.dividedBy(number2);
 });