tree e2bf1a5b1c58dba437d4b7548aeef7a7f36f0695
parent 02ff29bf00f5a687b68c19d1283f0954472a44ab
author Marcel van Lohuizen <mpvl@golang.org> 1609529303 +0100
committer Marcel van Lohuizen <mpvl@golang.org> 1609600284 +0000

doc/ref/spec.md: change disjunction rule

Closes #577

This change aims to make default handling more intuitive and
easier to reason about, both for the implementation and user.

This also removes the O1 rule, which is inconsitent
with the above text and not reflecting the implementation
(defaults are always chosen when used as operand to
an operator other than & or |).

This change has the nice mathematical property that
combining terms in resolving disjunctions uses the
same commutative operation for determing default
status regardless of whether it concerns resolving
nested disjunctions or distributing a unification over
disjunctions.

It makes several cases more intuitive and simplifies
reasoning over the implementation.

Closes #625

Change-Id: Ie483b9f2bbfd17756590f74a141f6cec9628baed
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/8001
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>