Positional-only args

[aganders3]

Hello - thanks again for taking the time to label some issues for first-time contributors! Some of the code has moved around a bit since the comments in #1439 so hopefully this is on the right track implementation-wise.

I don't love how rust-fmt stretched out the tests, so I may also try to come up with some shorter names for them.

---

TODO

• an entry in CHANGELOG.md

• docs to all new functions and / or detail in the guide

• tests for all new or changed functions

• Rust tests (Just cargo test or make test if you need to test examples)

• Rust lints (make clippy)

• Rust formatting (cargo fmt)

• Python formatting (black . --check. You can install black with pip install black)

• Compatibility with all supported Python versions for all examples. This uses tox; you can do run it using make test_py.

[birkenfeld]

Generally looks good to me, just a few small things and a potential later refactoring opportunity.

[davidhewitt]

👍 nice work and quick turnaround, thank you for doing this!

As well as the review comments, it would be desirable to add some UI tests to tests/ui/invalid_macro_args.rs to check the error messages for some invalid function signatures (e.g. / after * and similar combinations which should be rejected.)

[aganders3]

Thanks for the feedback and the good suggestions! I think it's just the UI tests remaining and hopefully I can get to that this week some time.

[aganders3]

One more thing. Regarding this line in the issue template:

Compatibility with all supported Python versions for all examples. This uses tox; you can do run it using make test_py.

This didn't work for me without the following changes, but I'm not sure if it's something about my environment. I'm happy to add this to this PR or start a new one if it's something you'd like.

diff --git a/Makefile b/Makefile
index fdd116c4b..95e482453 100644
--- a/Makefile
+++ b/Makefile
@@ -4,7 +4,7 @@ test: lint test_py
 	cargo test

 test_py:
-	for example in examples/*; do tox -e py -c $$example || exit 1; done
+	for example in examples/*/; do TOX_TESTENV_PASSENV=RUSTUP_HOME tox -e py -c $$example || exit 1; done

 fmt:
 	cargo fmt --all -- --check

[davidhewitt]

This didn't work for me without the following changes, but I'm not sure if it's something about my environment. I'm happy to add this to this PR or start a new one if it's something you'd like.

Ah thanks for pointing out. A new PR to fix that would be brilliant 👍

[davidhewitt]

This PR is absolutely great, this is a nice addition to add to the 0.15 release. Thanks for implementing!

[aganders3]

This PR is absolutely great, this is a nice addition to add to the 0.15 release. Thanks for implementing!

You're welcome! This was a fun way to get started. Thanks for the help.