yet another bug related to refining type arguments of supertypes

[gavinking]

This code:

class XX() satisfies Scalar<XX>&Comparable<XX|YY> {
    compare(XX|YY other) => nothing;
    divided(XX other) => nothing;
    float => nothing;
    fractionalPart => nothing;
    integer => nothing;
    magnitude => nothing;
    negated => nothing;
    negative => nothing;
    plus(XX other) => nothing;
    plusInteger(Integer integer) => nothing;
    positive => nothing;
    sign => nothing;
    times(XX other) => nothing;
    timesInteger(Integer integer) => nothing;
    wholePart => nothing;
}

class YY() satisfies Scalar<YY>&Comparable<XX|YY> {
    compare(XX|YY other) => nothing;
    divided(YY other) => nothing;
    float => nothing;
    fractionalPart => nothing;
    integer => nothing;
    magnitude => nothing;
    negated => nothing;
    negative => nothing;
    plus(YY other) => nothing;
    plusInteger(Integer integer) => nothing;
    positive => nothing;
    sign => nothing;
    times(YY other) => nothing;
    timesInteger(Integer integer) => nothing;
    wholePart => nothing;
}

Results in:

Name clash: compare(ceylon.language.Comparable) in foo.XX and compare(Other) in ceylon.language.Comparable have the same erasure, yet neither overrides the other

This bug blocks ceylon/ceylon.language#453.

[lucaswerkmeister]

Here’s updated code after Scalar was merged with Number (ceylon/ceylon.language#452):

class XX() satisfies Number<XX>&Comparable<XX|YY> {
    compare(XX|YY other) => nothing;
    divided(XX other) => nothing;
    fractionalPart => nothing;
    magnitude => nothing;
    negated => nothing;
    negative => nothing;
    plus(XX other) => nothing;
    plusInteger(Integer integer) => nothing;
    positive => nothing;
    sign => nothing;
    times(XX other) => nothing;
    timesInteger(Integer integer) => nothing;
    wholePart => nothing;
    powerOfInteger(Integer integer) => nothing;

}

class YY() satisfies Number<YY>&Comparable<XX|YY> {
    compare(XX|YY other) => nothing;
    divided(YY other) => nothing;
    fractionalPart => nothing;
    magnitude => nothing;
    negated => nothing;
    negative => nothing;
    plus(YY other) => nothing;
    plusInteger(Integer integer) => nothing;
    positive => nothing;
    sign => nothing;
    times(YY other) => nothing;
    timesInteger(Integer integer) => nothing;
    wholePart => nothing;
    powerOfInteger(Integer integer) => nothing;
}

And here’s much shorter code by making the classes abstract:

abstract class XX() satisfies Number<XX>&Comparable<XX|YY> {
    compare(XX|YY other) => nothing;
}

abstract class YY() satisfies Number<YY>&Comparable<XX|YY> {
    compare(XX|YY other) => nothing;
}

[tombentley]

Once we've fixed the declaration there's another issue with call sites:

void use(XX xx, XX|YY xy) {
    variable value c = xx <=> xy;
}

We currently do not downcast the Object xy argument to Comparable, so javac fails.

[tombentley]

This is going to be too hard to fix in the remaining time for 1.1, and the thing it's blocking (https://github.com/ceylon/ceylon.language/issues/453) is not for 1.1, so let's defer it for now.