Description Clovis Seragiotto 2020-07-14 08:32:34 EDT

class Foo implements AutoCloseable {
    static void foo(Foo foo) { foo.method(); } // warning here
    static void bar(java.io.PrintWriter pw) { pw.append('x'); } // no warning here, even though append returns this
    private Foo method() { return this; }
    @Override public void close() { /**/ }
}

Invoking a method on a resource may generate a warning or not if the method returns a reference to the resource itself. It depends.

In the example above, the compiler generates no warning for the class java.io.PrintWriter but generates a warning for the class Foo.

Which behavior is "correct" might be a matter of taste (I'd prefer no warning in this case), but both cannot be correct simultaneously.