Improve the error message for invalid default namespaces (#1513)

CHANGELOG.md

@@ -1,3 +1,8 @@
+## 1.43.2
+
+* Improve the error message when the default namespace of a `@use` rule is not
+  a valid identifier.
+
 ## 1.43.1
 
 * No user-visible changes.

lib/src/parse/stylesheet.dart

@@ -1398,7 +1398,11 @@ abstract class StylesheetParser extends Parser {
     try {
       return Parser.parseIdentifier(namespace, logger: logger);
     } on SassFormatException {
-      error('Invalid Sass identifier "$namespace"', scanner.spanFrom(start));
+      error(
+          'The default namespace "$namespace" is not a valid Sass identifier.\n'
+          "\n"
+          'Recommendation: add an "as" clause to define an explicit namespace.',
+          scanner.spanFrom(start));
     }
   }
 

pubspec.yaml

@@ -1,5 +1,5 @@
 name: sass
-version: 1.43.1
+version: 1.43.2-dev
 description: A Sass implementation in Dart.
 homepage: https://github.com/sass/dart-sass