[Chapel Merge] Defuturize: ref array formal can't accept iterable

Branch: refs/heads/main
Revision: def068f
Author: vasslitvinov
Link: Defuturize: ref array formal can't accept iterable by vasslitvinov · Pull Request #20137 · chapel-lang/chapel · GitHub
Log Message:

Merge pull request #20137 from vasslitvinov/defuturize_arrArgXXX-promote

Defuturize: ref array formal can't accept iterable

This PR resolves three futures by asserting the following semantics.
A formal argument of an array type cannot accept an iterable, such as
a promoted expression, when the formal's intent is ref or const ref.
This includes the default and const abstract intents.

The rationale is that a ref formal requires an actual argument of the
same type. An iterable expression does not have an array type and there is
no underlying array to refernce.

To force creation of an array out of an iterable when passing the latter
to a formal argument, the formal argument must have an in or const in
intent, see test/users/thom/arrArgIn-promote.chpl .

Next steps, recorded in #20166: should a ref formal accept
an array returned by a function with the default return intent?
What if it is a const ref formal and/or
the function's return intent is const ?
For example:

proc writeArr(ref X) { // what if X has a const ref intent?
proc addEm() { // what if addEm() has a const return intent?
return [1,2];

r: @mppf; discussed with @bradcray

Modified Files:
A test/users/thom/arrArg-fromFunction.bad

A test/users/thom/arrArg-fromFunction.chpl
A test/users/thom/arrArg-fromFunction.future
A test/users/thom/arrArg-fromFunction.good
R test/users/thom/arrArgBlank-promote.bad
R test/users/thom/arrArgBlank-promote.future
R test/users/thom/arrArgConst-promote.bad
R test/users/thom/arrArgConst-promote.future
R test/users/thom/arrArgRef-promote.bad
R test/users/thom/arrArgRef-promote.future
M test/users/thom/arrArgBlank-promote.chpl
M test/users/thom/arrArgBlank-promote.good
M test/users/thom/arrArgConst-promote.chpl
M test/users/thom/arrArgConst-promote.good
M test/users/thom/arrArgRef-promote.chpl
M test/users/thom/arrArgRef-promote.good

Compare: https://github.com/chapel-lang/chapel/compare/c95e18032591...def068f196de