https://github.com/rust-lang/rust http://git.dreamy.place/mirrors/rust/atom?h=1.55.0 2021-07-11T20:08:58+00:00 2021-07-11T20:08:58+00:00 Eric Huss eric@huss.org 2021-07-11T20:08:58+00:00 urn:sha1:4d1daf86833392f9b819938c3ce0848c3adede50 2021-07-06T16:50:33+00:00 bors bors@rust-lang.org 2021-07-06T16:50:33+00:00 urn:sha1:238fd72880776c5dbd3b067acb096562e6af5399 Force warnings even when can_emit_warnings == false Fixes an issue mentioned in #85512 with --cap-lints overriding --force-warnings. Fixes https://github.com/rust-lang/rust/issues/86751 r? `@ehuss` 2021-07-06T11:47:03+00:00 Ryan Levick me@ryanlevick.com 2021-07-06T11:47:03+00:00 urn:sha1:5af5a6d49dd5a72c7c4f48ba9749b84002e0b99e 2021-07-01T10:29:20+00:00 Ryan Levick me@ryanlevick.com 2021-07-01T10:29:20+00:00 urn:sha1:33cc7b1fe21c82d31204e549cd2471ac8ec22aa3 2021-06-30T09:18:33+00:00 Ryan Levick me@ryanlevick.com 2021-06-04T12:37:20+00:00 urn:sha1:a3d6905053ad60e836717976e6e4d38de67888f9 2021-06-28T15:30:49+00:00 Mark Rousskov mark.simulacrum@gmail.com 2021-06-24T16:47:33+00:00 urn:sha1:06661ba7591b1531555cd084f75540d99ef35ac5 2021-06-02T06:49:58+00:00 Tomasz Miąsko tomasz.miasko@gmail.com 2021-06-01T00:00:00+00:00 urn:sha1:c1f6495b8e19325a57702a7ce016e6d5a3f25e26 2021-05-18T05:01:36+00:00 Joshua Nelson jyn514@gmail.com 2021-03-22T05:10:10+00:00 urn:sha1:e48b6b459974245efcfc9edda468b4c587cbf37c # Stabilization report ## Summary This stabilizes using macro expansion in key-value attributes, like so: ```rust #[doc = include_str!("my_doc.md")] struct S; #[path = concat!(env!("OUT_DIR"), "/generated.rs")] mod m; ``` See the changes to the reference for details on what macros are allowed; see Petrochenkov's excellent blog post [on internals](https://internals.rust-lang.org/t/macro-expansion-points-in-attributes/11455) for alternatives that were considered and rejected ("why accept no more and no less?") This has been available on nightly since 1.50 with no major issues. ## Notes ### Accepted syntax The parser accepts arbitrary Rust expressions in this position, but any expression other than a macro invocation will ultimately lead to an error because it is not expected by the built-in expression forms (e.g., `#[doc]`). Note that decorators and the like may be able to observe other expression forms. ### Expansion ordering Expansion of macro expressions in "inert" attributes occurs after decorators have executed, analogously to macro expressions appearing in the function body or other parts of decorator input. There is currently no way for decorators to accept macros in key-value position if macro expansion must be performed before the decorator executes (if the macro can simply be copied into the output for later expansion, that can work). ## Test cases - https://github.com/rust-lang/rust/blob/master/src/test/ui/attributes/key-value-expansion-on-mac.rs - https://github.com/rust-lang/rust/blob/master/src/test/rustdoc/external-doc.rs The feature has also been dogfooded extensively in the compiler and standard library: - https://github.com/rust-lang/rust/pull/83329 - https://github.com/rust-lang/rust/pull/83230 - https://github.com/rust-lang/rust/pull/82641 - https://github.com/rust-lang/rust/pull/80534 ## Implementation history - Initial proposal: https://github.com/rust-lang/rust/issues/55414#issuecomment-554005412 - Experiment to see how much code it would break: https://github.com/rust-lang/rust/pull/67121 - Preliminary work to restrict expansion that would conflict with this feature: https://github.com/rust-lang/rust/pull/77271 - Initial implementation: https://github.com/rust-lang/rust/pull/78837 - Fix for an ICE: https://github.com/rust-lang/rust/pull/80563 ## Unresolved Questions ~~https://github.com/rust-lang/rust/pull/83366#issuecomment-805180738 listed some concerns, but they have been resolved as of this final report.~~ ## Additional Information There are two workarounds that have a similar effect for `#[doc]` attributes on nightly. One is to emulate this behavior by using a limited version of this feature that was stabilized for historical reasons: ```rust macro_rules! forward_inner_docs { ($e:expr => $i:item) => { #[doc = $e] $i }; } forward_inner_docs!(include_str!("lib.rs") => struct S {}); ``` This also works for other attributes (like `#[path = concat!(...)]`). The other is to use `doc(include)`: ```rust #![feature(external_doc)] #[doc(include = "lib.rs")] struct S {} ``` The first works, but is non-trivial for people to discover, and difficult to read and maintain. The second is a strange special-case for a particular use of the macro. This generalizes it to work for any use case, not just including files. I plan to remove `doc(include)` when this is stabilized. The `forward_inner_docs` workaround will still compile without warnings, but I expect it to be used less once it's no longer necessary. 2021-05-12T23:03:06+00:00 Aaron Hill aa1ronham@gmail.com 2021-02-13T19:52:25+00:00 urn:sha1:0dd9f118d973bb077c6ff0e2a57421ca2eecb81c When there are multiple macros in use, it can be difficult to tell which one was responsible for producing an error. 2021-05-09T03:13:04+00:00 Joshua Nelson jyn514@gmail.com 2021-03-28T02:58:25+00:00 urn:sha1:ebbc94957555350cdc71c4c853de430119f59f9f