Adds a `ProcMacro` form of syntax extension
This commit adds syntax extension forms matching the types for procedural macros 2.0 (RFC #1566), these still require the usual syntax extension boiler plate, but this is a first step towards proper implementation and should be useful for macros 1.1 stuff too.
Supports both attribute-like and function-like macros.
Note that RFC #1566 has not been accepted yet, but I think there is consensus that we want to head in vaguely that direction and so this PR will be useful in any case. It is also fairly easy to undo and does not break any existing programs.
This is related to #35957 in that I hope it can be used in the implementation of macros 1.1, however, there is no direct overlap and is more of a complement than a competing proposal. There is still a fair bit of work to do before the two can be combined.
r? @jseyfried
cc @alexcrichton, @cgswords, @eddyb, @aturon
Assign node ids during macro expansion
After this PR,
- The `ExtCtxt` can access `resolve`'s `Resolver` through the trait object `ext::base::Resolver`.
- The `Resolver` trait object can load macros and replaces today's `MacroLoader` trait object.
- The macro expander uses the `Resolver` trait object to resolve macro invocations.
- The macro expander assigns node ids and builds the `Resolver`'s `macros_at_scope` map.
- This is groundwork for merging import resolution and expansion.
- Performance of expansion together with node id assignment improves by ~5%.
**EDIT:** Since Github is reordering the commits, here is `git log`:
- b54e1e399741579612f13e2df98a25ea9447989d: Differentiate between monotonic and non-monotonic expansion and only assign node ids during monotonic expansion.
- 78c00398780db6f59ebf43e765fa9368dad436d2: Expand generated test harnesses and macro registries.
- f3c2dca3539e6edc745f9c91898cb97d281865c1: Remove scope placeholders from the crate root.
- c86c8d41a26b2037e80c9fd028a59313a78b3a66: Perform node id assignment and `macros_at_scope` construction during the `InvocationCollector` and `PlaceholderExpander` folds.
- 72a636975fc5d0bb4af45af7bdd97987cc722a6a: Move macro resolution into `librustc_resolve`.
- 20b43b23230ce063ccf99a4841d85790ad311bdf: Rewrite the unit tests in `ext/expand.rs` as a `compile-fail` test.
- a9821e1658240bb2c056f260a4b6bc9789301fae: Refactor `ExtCtxt` to use a `Resolver` instead of a `MacroLoader`.
- 60440b226d2f70bdae803443ff7ad2e2af2c9b10: Refactor `noop_fold_stmt_kind` out of `noop_fold_stmt`.
- 50f94f6c95c944f08c4af264f48260e42efefd47: Avoid needless reexpansions.
r? @nrc
The span labels for associated types and consts were hardcoded to `Foo`
rather than substituting the name of the trait.
This also normalizes the wording for associated methods', traits', and
consts' span labels.
Fixes#36428.
resolve: Suggest `use self` when import resolves
Improves errors messages by replacing "Maybe a missing `extern crate`" messages
with "Did you mean `self::...`" when the `self` import would succeed.
Fixes#34191.
Thank you for the help @jseyfried!
