Speed up the macro parser
These three commits reduce the number of allocations done by the macro parser, in some cases dramatically. For example, for a clean check builds of html5ever, the number of allocations is reduced by 40%.
Here are the rustc-benchmarks that are sped up by at least 1%.
```
html5ever-check
avg: -6.6% min: -10.3% max: -4.1%
html5ever
avg: -5.2% min: -9.5% max: -2.8%
html5ever-opt
avg: -4.3% min: -9.3% max: -1.6%
crates.io-check
avg: -1.8% min: -2.9% max: -0.6%
crates.io-opt
avg: -1.0% min: -2.2% max: -0.1%
crates.io
avg: -1.1% min: -2.2% max: -0.2%
```
check stability of macro invocations
I haven't implemented tests yet but this should be a pretty solid prototype. I think as-implemented it will also stability-check macro invocations in the same crate, dunno if we want that or not.
I don't know if we want this to go through `rustc::middle::stability` or not, considering the information there wouldn't be available at the time of macro expansion (even for external crates, right?).
r? @nrc
closes#34079
cc @petrochenkov @durka @jseyfried #38356
Started rebasing @sgrif's PR #33135 off of current master. (Well, actually merging it into a new branch based off current master.)
The following files still need to be fixed or at least reviewed:
- `src/libsyntax/ext/tt/macro_parser.rs`: calls `Parser::parse_lifetime`, which doesn't exist anymore
- `src/libsyntax/parse/parser.rs`: @sgrif added an error message to `Parser::parse_lifetime`. Code has since been refactored, so I just took it out for now.
- `src/libsyntax/ext/tt/transcribe.rs`: This code has been refactored bigtime. Not sure whether @sgrif's changes here are still necessary. Took it out for this commit.
trace_macro: Show both the macro call and its expansion. #42072.
See #42072 for the initial motivation behind this.
The change is not the minimal fix, but I want this behavior almost every time I use `trace_macros`.
This is useful if parsing from stdin or a String and don't want to try and read in a module from another file. Instead we just leave a stub in the AST.
This commit extends the current unused macro linter
to support directives like #[allow(unused_macros)]
or #[deny(unused_macros)] directly next to the macro
definition, or in one of the modules the macro is
inside. Before, we only supported such directives
at a per crate level, due to the crate's NodeId
being passed to session.add_lint.
We also had to implement handling of the macro's
NodeId in the lint visitor.
