- Add detail on origin of current parser when reaching EOF and stop
saying "found <eof>" and point at the end of macro calls
- Handle empty `cfg_attr` attribute
- Reword empty `derive` attribute error
The current code (expensively) clones the value within an `Rc`. This
commit changes things so that the `Rc` itself is (cheaply) cloned
instead, avoid some allocations.
This requires converting a few `Rc` instances to `Lrc`.
It's present within `Token::Interpolated` as an optimization, so that if
a nonterminal is converted to a `TokenStream` multiple times, the
first-computed value is saved and reused.
But in practice it's not needed. `interpolated_to_tokenstream()` is a
cold function: it's only called a few dozen times while compiling rustc
itself, and a few hundred times across the entire `rustc-perf` suite.
Furthermore, when it is called, it is almost always the first
conversion, so no benefit is gained from it.
So this commit removes `LazyTokenStream`, along with the now-unnecessary
`Token::interpolated()`.
As well as a significant simplification, the removal speeds things up
slightly, mostly due to not having to `drop` the `LazyTokenStream`
instances.
Rename rustc_errors dependency in rust 2018 crates
I think this is a better solution than `use rustc_errors as errors` in `lib.rs` and `use crate::errors` in modules.
Related: rust-lang/cargo#5653
cc #58099
r? @Centril
`create_matches` creates a `Vec<Rc<Vec<NamedMatch>>>`. Even though all the
inner `Vec`s are empty, each one is created separately.
This commit changes `create_matches` so it instead creates one empty inner
`Vec`, and shares it.
The commit also changes `MatcherPos::matches` to a boxed slice, because its
length doesn't change.
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%
```
