Guard unstable proc_macro things behind nightly feature
#26
Conversation
This is most of the work for #13. This crate now compiles in two modes: With "nightly" feature enable, `proc_macro_diagnostic` and `proc_macro_span` are enable to improve our error messages. Without the "nightly" feature, we don't use those unstable features and instead build a workaround for the lack of unstable features (something like a poly fill). Most of the workaround can be found in the `diag` module. The crate doesn't compile with the stable compiler quite yet. There are still three feature gates activated. But those three features will be stabilized for Rust 2018 and they are easy to remove by only rewriting a few lines in the whole crate.
The examples are a bit awkward for some reason: examples are compiled when one executes `cargo test`. This is nice, but we actually want those examples to fail. We can't just exclude them, so we only compile the interesting part when the `fail` cfg is set. I hope to find a better solution for this...
- no extern crate anymore (except for quote because of #[macro_use]) - replace `pub(crate)` with `crate` - use lifetime elision in impl
- crate is tested with and without 'nightly' feature - warnings lead to a build failure
src/diag.rs
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| use proc_macro::{Diagnostic, Span}; | ||
| //! This module has two purposes: | ||
| //! | ||
| //! 1. Provide the convenienve method `emit_with_attr_note` and add it via |
Sure! If you have any questions or discuss anything, you can also just write via email or ping me on Discord (I'm rarely on IRC, sorry!). But yes, I'm not completely satisfied with these changes. In particular, fewer Regarding the examples that are supposed to show an error message: what do you think about removing this cfg hack and instead just comment-out the line that's causing the error. So something like: // Add the line below to see the error message.
//#[auto_impl(Boxxi)]
trait Foo {
fn foo(&self) -> u32;
}Then we could also combine the fail examples into one example I think I would like to change that still. What do you think? |
- Do not use in-band lifetimes, as they are probably not stabilized in the current form (and thus are not part of Rust 2018) - Remove `#![feature(rust_2018_preview)]` as it's default now
`extern crate auto_impl` could also be removed :)
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@KodrAus I added a bunch of new commits. The commit messages should explain everything, but the main change is to update several files to a newer nightly version (in particular because of rust-lang/rust#50911). Basically, we have fewer The last commit simplifies the examples. It does what I suggested in the last comment. I think I'm happier with it this way. |
Now, the user has to simply add a line that has been commented to see the error. A lot simpler.
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Yeh this looks nice and clear 👍 Feel free to merge whenever you're ready! |
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Wonderful :) |
This does most of the work for #13. The crate now has a
nightlyfeature that is disabled by default. With that feature disabled, we use not-so-nice diagnostics and call-site hygiene. With the feature enabled, we use nice diagnostics and def-site hygiene.It still doesn't compile on stable, as it uses several Rust 2018 features (as described in #13). But again, those will be stabilized soon. And even if not, they are easy to replace.
The second commit adds two examples that showcase error messages. It's a bit of a hack... I don't know if this is OK like that. (EDIT: I think I don't quite like it. I would probably instead try to add an option to the compile-fail script to just compile a specific example without capturing stdout. But maybe we can still merge it like this and I can change it later.)