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Annotations on any type arguments of a method receiver are ignored #104

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zcai1 opened this issue Sep 30, 2021 · 2 comments · May be fixed by #793
Open

Annotations on any type arguments of a method receiver are ignored #104

zcai1 opened this issue Sep 30, 2021 · 2 comments · May be fixed by #793
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@Ao-senXiong
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@zcai1
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zcai1 commented Sep 30, 2021 •
edited by wmdietl
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For example, we have the following test case that throws an NPE:

public class ReceiverTypeArgs {
    static class Box<T> {
        T item;

        public Box(T item) {
            this.item = item;
        }

        void test(Box<@NonNull T> this) {
            System.out.println(this.item.toString());
        }
    }

    private static void foo(Box<@Nullable String> box) {
        // expected: invalid method receiver
        box.test();
    }

    public static void main(String[] args) {
        foo(new Box<>(null));
    }
}

Note that the method receiver parameter Box<@NonNull T> this should not accept the argument Box<@Nullable String> box since generics are invariant. However, the Checker Framework doesn't have any warnings for this test case.
@cpovirk
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cpovirk commented Jan 5, 2022

(Upstream has issue 3203 for this.)

@wmdietl
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wmdietl commented May 7, 2024

I just ran into this again:

import org.checkerframework.checker.nullness.qual.Nullable;

class MyBox<E extends @Nullable Object> {
  E f;

  MyBox(E in) {
    f = in;
  }

  void set(E in) {
    f = in;
  }
  
  void nullOut(MyBox<@Nullable E> this) {
    set(null);
  }

  void demo(MyBox<String> mbs, MyBox<@Nullable String> mbns) {
    mbns.set(null); // ok
    mbs.set(null); // error
  }
  
  void demoNullout(MyBox<String> mbs, MyBox<@Nullable String> mbns) {
    mbns.nullOut(); // ok
    mbs.nullOut(); // should error, but none raised
  }
}

@wmdietl wmdietl mentioned this issue May 7, 2024
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@wmdietl wmdietl linked a pull request Jun 26, 2024 that will close this issue
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Don't erase the type argument of receiver Ao-senXiong/checker-framework
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@cpovirk @wmdietl @zcai1 @Ao-senXiong