[pigeon] added error for static fields (#392)

packages/pigeon/CHANGELOG.md

@@ -1,6 +1,7 @@
 ## NEXT
 
 * [front-end] Added a more explicit error if generic fields are used.
+* [front-end] Added a more explicit error for static fields.
 
 ## 0.3.0
 

packages/pigeon/lib/pigeon_lib.dart

@@ -683,7 +683,12 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
   Object? visitFieldDeclaration(dart_ast.FieldDeclaration node) {
     if (_currentClass != null) {
       final dart_ast.TypeAnnotation? type = node.fields.type;
-      if (type is dart_ast.NamedType) {
+      if (node.isStatic) {
+        _errors.add(Error(
+            message:
+                'Pigeon doesn\'t support static fields ("${node.toString()}"), consider using enums.',
+            lineNumber: _calculateLineNumber(source, node.offset)));
+      } else if (type is dart_ast.NamedType) {
         _currentClass!.fields.add(Field(
           name: node.fields.variables[0].name.name,
           dataType: type.toString(),

packages/pigeon/test/pigeon_lib_test.dart

@@ -416,4 +416,26 @@ void main() {
     expect(parseResult.errors[0].message, contains('Generic fields'));
     expect(parseResult.errors[0].lineNumber, isNotNull);
   });
+
+  test('error with static field', () {
+    final Pigeon dartle = Pigeon.setup();
+    const String code = '''
+class WithStaticField {
+  static int? x;
+  int? y;
+}
+
+@HostApi()
+abstract class WithStaticFieldApi {
+  void doit(WithStaticField withTemplate);
+}
+''';
+    _withTempFile('compilationError.dart', (File file) {
+      file.writeAsStringSync(code);
+      final ParseResults parseResult = dartle.parseFile(file.path);
+      expect(parseResult.errors.length, equals(1));
+      expect(parseResult.errors[0].message, contains('static field'));
+      expect(parseResult.errors[0].lineNumber, isNotNull);
+    });
+  });
 }