Polymorphic qualifier substitution in member references

[wmdietl]

While working on #2876 I've noticed that polymorphic qualifier substitution does not seem to work for member references.

Take:

import java.util.function.Supplier;
import testlib.util.Encrypted;
import testlib.util.PolyEncrypted;

class PolyMemberRef {
  @SuppressWarnings("return.type.incompatible") // impl
  @PolyEncrypted String id(@PolyEncrypted PolyMemberRef this) { return this.toString(); }

  void giveUnq(Supplier<String> s) {}
  void giveEnc(Supplier<@Encrypted String> s) {}

  void foo(PolyMemberRef u, @Encrypted PolyMemberRef e) {
    giveUnq(u::id);
    giveEnc(e::id);
  }
}

Run something like: ./checker/bin-devel/javac -cp framework/build/classes/java/test -processor org.checkerframework.common.subtyping.SubtypingChecker -Aquals=testlib.util.Encrypted,testlib.util.PolyEncrypted,org.checkerframework.common.subtyping.qual.Unqualified PolyMemberRef.java

And you'll get an error:

PolyMemberRef.java:14: error: [methodref.return.invalid] Incompatible return type
    giveEnc(e::id);
            ^
  Method
    String id(PolyMemberRef this) in PolyMemberRef
  is not a valid method reference for
    @Encrypted String get(Supplier<@Encrypted String> this) in java.util.function.Supplier
  found   : String
  required: @Encrypted String
1 error

The receiver used in the member reference should be used to resolve the polymorphic qualifier.

[smillst]

Here's another example:

import org.checkerframework.checker.tainting.qual.PolyTainted;
import org.checkerframework.checker.tainting.qual.Tainted;

public class PolyReceiver {

    @PolyTainted PolyReceiver polyReceiverReturn(@PolyTainted PolyReceiver this, Object o) {
        return this;
    }

    PolyReceiver noPoly(PolyReceiver this, Object o) {
        return this;
    }

   @PolyTainted Object polyParameterReturn(PolyReceiver this, @PolyTainted Object o) {
        return o;
    }

    interface SetterPolyReceiver {
        @PolyTainted Object consume(@PolyTainted SetterPolyReceiver this, Object p);
    }

    interface SetterTaintedReceiver {
        @PolyTainted Object consume(SetterTaintedReceiver this, @PolyTainted Object p);
    }


    void use(@Tainted PolyReceiver this) {
        // What should theses errors be?
        // :: error: (?)
        SetterPolyReceiver s1 = this::noPoly;
        // :: error: (?)
        SetterPolyReceiver s2 = this::polyReceiverReturn;
        // :: error: (?)
        SetterPolyReceiver s3 = this::polyParameterReturn;

        // The next three assignments issues the correct errors or no error.
        // :: error: (methodref.return.invalid)
        SetterTaintedReceiver s4 = this::noPoly;
        // :: error: (methodref.return.invalid)
        SetterTaintedReceiver s5 = this::polyReceiverReturn;
        // no error
        SetterTaintedReceiver s6 = this::polyParameterReturn;
    }

}

[lnsun]

Here's another example:

import org.checkerframework.checker.tainting.qual.PolyTainted;
import org.checkerframework.checker.tainting.qual.Tainted;

public class PolyReceiver {

    @PolyTainted PolyReceiver polyReceiverReturn(@PolyTainted PolyReceiver this, Object o) {
        return this;
    }

    PolyReceiver noPoly(PolyReceiver this, Object o) {
        return this;
    }

   @PolyTainted Object polyParameterReturn(PolyReceiver this, @PolyTainted Object o) {
        return o;
    }

    interface SetterPolyReceiver {
        @PolyTainted Object consume(@PolyTainted SetterPolyReceiver this, Object p);
    }

    interface SetterTaintedReceiver {
        @PolyTainted Object consume(SetterTaintedReceiver this, @PolyTainted Object p);
    }


    void use(@Tainted PolyReceiver this) {
        // What should theses errors be?
        // :: error: (?)
        SetterPolyReceiver s1 = this::noPoly;
        // :: error: (?)
        SetterPolyReceiver s2 = this::polyReceiverReturn;
        // :: error: (?)
        SetterPolyReceiver s3 = this::polyParameterReturn;

        // The next three assignments issues the correct errors or no error.
        // :: error: (methodref.return.invalid)
        SetterTaintedReceiver s4 = this::noPoly;
        // :: error: (methodref.return.invalid)
        SetterTaintedReceiver s5 = this::polyReceiverReturn;
        // no error
        SetterTaintedReceiver s6 = this::polyParameterReturn;
    }

}

@smillst I think s2 and s5 have a little problem: if the assignment l-value (SetterPolyReceiver and SetterTaintedReceiver) method return type have any poly annotation, r-value (this::polyReceiverReturn) will not be poly resolved*, so the poly annotation on receiver remains. And this causes this::polyReceiverReturn to have a methodref.receiver.bound.invalid error bacause acutal receiver is @Tainted PolyReceiver, not compatible with the declared receiver @PolyTainted PolyReceiver this in polyReceiverReturn.

• checker-framework/framework/src/main/java/org/checkerframework/framework/type/poly/AbstractQualifierPolymorphism.java

  Line 189 in e0f9784

  if (QualifierPolymorphism.hasPolymorphicQualifier(type)) {

(I didn't found java.util.function.Supplier in stub files, so I assume the function in the interface only have default annotation)