false positive of "Arguments of || should introduce same variables"

[jurgenvinju]

Describe the bug

This reports:

Arguments of || should introduce same variables, right argument does not introduce key

However, key is not introduced by the left side of ||, it was bound earlier:

if (key <- params, [*_,label(key, sym),*_] := kwTypes || sym := \value())) {
  println("bla");
}

To Reproduce

Simpler situation to test. Produces the same error:

Arguments of || should introduce same variables, right argument does not introduce i

if (int i := 1, [i,j] := [1,2] || int j := 2) {
  println("matches");
}

[jurgenvinju]

I'd like this fixed because there is a new standard library module that depends on it waiting to be merged. Is it something I could try myself @PaulKlint ?

[jurgenvinju]

See https://github.com/usethesource/rascal/pull/1503

[PaulKlint]

@jurgenvinju No chance, it has been waiting for so long because this is a difficult fix

[jurgenvinju]

If we'd add the explicit operator for equality checking in a pattern match, wouldn't this become a lot easier? Maybe it's time we move forward on that anyway. Got bitten by a sneak equality again last week :-)

[PaulKlint]

This is similar to #1515. All depends on the scoping of the operands of ||. Tricky business!

[PaulKlint]

Thanks for reporting. Indeed the handling of || was incorrect and resulted in false positives like the one above. Fixed.