If a superclass declares a method with a generic return type and a subclass
overrides that method but returns the corresponding raw type then compiling
both classes together with -source 1.5 causes an error message to be printed.

In this situation the compiler should instead print a warning message since
this situation is analogous to that of assigning a value of a raw type to a
variable of a generic type, which is allowed but prints a warning.

% cat G1.java

import java.util.*;

public class G1 {

    Iterator<String> strings() { return null; }

}
% cat G2.java

import java.util.*;

public class G2 extends G1 {

    Iterator strings() { return null; }

}
% /w/auto/tiger/build/latest/bin/javac -source 1.5 G1.java G2.java
G2.java:6: strings() in G2 cannot override strings() in G1; attempting to use incompatible return type
found : java.util.Iterator
required: java.util.Iterator<java.lang.String>
    Iterator strings() { return null; }
             ^
1 error
%