Wollok allows to override a concrete method with an abstract method

[flbulgarelli]

Wollok is accepting the following program, but it shoudn't:

class Foo {
    method foo() { console.println('foo') }
}

class Baz inherits Foo {
    override method foo()
}

Also, in runtime, if you do new Baz().foo(), it evaluates the superclass version.

[javierfernandes]

Done ! Check PR and close please

[flbulgarelli]

Done :smile: