Issue 24791: *args regression - Python tracker

The following code is allowed by the grammar of Python 3.4, but not Python 3.5:

`def f(): g(*a or b)`

where unary `*` has the lowest precedence, i.e. it is equivalent to:

`def f(): g(*(a or b))`

The cause of the regression that the 3.4 grammar for `arglist` uses `'*' test` but the 3.5 grammar uses `'*' expr`. This is likely an oversight due to the PEP 448 changes; the fix should most likely be applied to the new `display`s as well as fixing the regression.


***

Thanks to zware on IRC for actually testing this for me, since I don't have a runnable python3.5, just docs.

Related: bug 24176 fixed this for the `**` case.

New changeset 3c170f68407f by Zachary Ware in branch '3.4':
Issue #24791: Add tests for things that regressed with PEP 448
https://hg.python.org/cpython/rev/3c170f68407f

Test committed on 3.4; I'm not comfortable enough with the grammar to actually fix the issue (the obvious change of `star_expr` => `'*' test` isn't enough, I tried :)).

The attached patch should fix that. Please review.

Also consider:

*() or (), *() or ()
[*() or (), *() or ()]
{*() or (), *() or ()}
{**{} or {}, **{} or {}}

Note that the second-or-later argument is a separate part of the grammar so that's why I wrote it twice.

Actually, I think `star_expr` will probably go away entirely.

> Actually, I think `star_expr` will probably go away entirely.

I'm not so concerned with supporting [*[] or []] stuff, but rather fixing the immediate regression in 3.5.0.  I'd keep the patch size to the minimum.

New changeset e4cb64628673 by Yury Selivanov in branch '3.5':
Issue #24791: Fix grammar regression for call syntax: 'g(*a or b)'.
https://hg.python.org/cpython/rev/e4cb64628673

New changeset 4c89dd5199e5 by Yury Selivanov in branch 'default':
Merge 3.5 (issue #24791)
https://hg.python.org/cpython/rev/4c89dd5199e5

New changeset 40c391d12741 by Yury Selivanov in branch '3.5':
Issue #24791: More tests in test_parser
https://hg.python.org/cpython/rev/40c391d12741

New changeset a572137b4f05 by Yury Selivanov in branch 'default':
Merge 3.5 (issue #24791; more tests in test_parser)
https://hg.python.org/cpython/rev/a572137b4f05

New changeset 20e0906a808e by Terry Jan Reedy in branch '3.5':
Issue #24791: Escape rst markup char in NEWS entry to avoid Sphinx warning.
https://hg.python.org/cpython/rev/20e0906a808e