equality and null

[@gavinking] We finally thought of an acceptable approach to equality and null. We propose to make == accept non-definite typed operands, but in the case that both operands are non-definite types, we will assign it the type Boolean?, and have it evaluate to null in the case that both operands evaluate to null.

So, you can write:

if (maybeCat==maybeTruck else false) {
    ...
}

The remaining question is whether we should make this the behavior of a new operator =?=.

[Migrated from ceylon/ceylon-spec#1089]

[CeylonMigrationBot]

[@quintesse] And also that comparing T == T , T == T? or T? == T results in a Boolean while T? == T? results in a Boolean? (given T satisfies Object).

left	right	result
T	T	Boolean
T	T?	Boolean
T?	T	Boolean
T?	T?	Boolean?

[lucono]

Have run into this several times and this change would make those cases a lot better.