New Issue: challenges initializing an empty array of non-nilable classes

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1

20512, "mppf", "challenges initializing an empty array of non-nilable classes", "2022-08-25T16:50:37Z"

I'd like to be able to create an array of non-nilable classes.
However, creating such an array is actually quite hard.

Here is the obvious code:

class C { }

proc main() {
  var A: [1..0] owned C;
}

That fails with error: cannot default-initialize the array A because it has a non-nilable element type 'owned C'.

But, that is annoying, because the array has 0 elements, so no element needs to be default-initialized.

We have domain.unsafeAssign for initializing non-default initializable array elements. Could there be a similar feature for initializing an array? Note that I can't use it to initialize an array (because the array has to exist first in order for me to assign it...)

In the meantime, one can use ugly workarounds like this:

class C { }

proc main() {
  var A: [1..0] owned C = for i in 1..0 do new C();
}

or, for an array of borrows:

class C { }

proc main() {
  var dummyC: unmanaged C? = nil;
  var A: [1..0] borrowed C = for i in 1..0 do dummyC!;
}