Chapel's list type should support initialization from an iterator expression

[bradcray]

It seems like it would be convenient / natural to have Chapel's list type support initialization from an initializer expression as follows:

var l: list(t) = myIterYieldingTypeT();

Is there a reason we wouldn't want to that I'm not seeing?

If not, this seems as though it could be implemented by defining an init= for list taking an _iteratorRecord?

[mppf]

After PR #16180 we could alternatively adjust proc init=(other: [?d] this.type.eltType) to use the in intent which should also allow it.

[bradcray]

Would that have the effect of manifesting the array in memory prior to assigning it to the list? (where I'm guessing it would be cheaper to just traverse the iterator and insert the elements one by one?)

[mppf]

@bradcray - yes it would - as a result I would agree that the _iteratorRecord would be better for performance.

[mppf]

Would that have the effect of manifesting the array in memory prior to assigning it to the list? (where I'm guessing it would be cheaper to just traverse the iterator and insert the elements one by one?)

Actually, using the in intent would solve #13583. However the array copy involved is probably not desired.

[mppf]

PR #16708 adds the overload for init=. (We don't have the corresponding proc = overload yet and issue #16714 asks if list should allow cross-type assignments).