Wildcards should not be allowed in parameterized supertype type arguments

[Jesper Öqvist]

ExtendJ 8.1.1-13-g984cc95 Java SE 8

ExtendJ allows wildcard types as the type arguments of a supertype.

The Java specification disallows this. See JLS 8 section 8.1.2. Specifically, this line:

If the ClassType has type arguments, it must denote a well-formed parameterized type (§4.5), and none of the type arguments may be wildcard type arguments, or a compile-time error occurs.

Here is a test that fails to give an error with ExtendJ:

public class Test2 extends S<? extends Number> { }
class S<T> {}

Expected result: the declarations above should generate a compile error. For example, javac gives this error:

javac Test2.java
Test2.java:1: error: unexpected type
public class Test2 extends S<? extends Number> { }
                            ^
  required: class or interface without bounds
  found:    ? extends Number
1 error

Actual result: no error was reported for the test.