#392. Covariant parameters test added
diff --git a/LanguageFeatures/Extension-methods/syntax_covariant_t01.dart b/LanguageFeatures/Extension-methods/syntax_covariant_t01.dart
new file mode 100644
index 0000000..a057137
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+++ b/LanguageFeatures/Extension-methods/syntax_covariant_t01.dart
@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2019, the Dart project authors. Please see the AUTHORS file
+ * for details. All rights reserved. Use of this source code is governed by a
+ * BSD-style license that can be found in the LICENSE file.
+ */
+/**
+ * @assertion an extension declaration is a top-level declaration with a grammar
+ * similar to:
+ * <extension> ::=
+ * `extension' <identifier>? <typeParameters>? `on' <type> `?'? `{'
+ * memberDeclaration*
+ * `}'
+ * Instance member declaration parameters must not be marked covariant
+ *
+ * @description Check that instance member declaration parameters must not be
+ * marked covariant
+ * @author sgrekhov@unipro.ru
+ */
+// SharedOptions=--enable-experiment=extension-methods
+
+class A {}
+
+class C extends A {
+}
+
+extension on C {
+ addChild(covariant A child) {} //# 01: compile-time error
+ addChild2(A c, [covariant A child]) {} //# 02: compile-time error
+ addChild3(A c, {covariant A child}) {} //# 03: compile-time error
+ void set setter (covariant A value) {} //# 04: compile-time error
+ C operator+(A other) => this; //# 05: compile-time error
+}
+
+main() {
+ new C();
+}
