Added byte position range for `proc_macro::Span`
Currently, the [`Debug`](https://doc.rust-lang.org/beta/proc_macro/struct.Span.html#impl-Debug-for-Span) implementation for [`proc_macro::Span`](https://doc.rust-lang.org/beta/proc_macro/struct.Span.html#) calls the debug function implemented in the trait implementation of `server::Span` for the type `Rustc` in the `rustc-expand` crate.
The current implementation, of the referenced function, looks something like this:
```rust
fn debug(&mut self, span: Self::Span) -> String {
if self.ecx.ecfg.span_debug {
format!("{:?}", span)
} else {
format!("{:?} bytes({}..{})", span.ctxt(), span.lo().0, span.hi().0)
}
}
```
It returns the byte position of the [`Span`](https://doc.rust-lang.org/beta/proc_macro/struct.Span.html#) as an interpolated string.
Because this is currently the only way to get a spans position in the file, I might lead someone, who is interested in this information, to parsing this interpolated string back into a range of bytes, which I think is a very non-rusty way.
The proposed `position()`, method implemented in this PR, gives the ability to directly get this info.
It returns a [`std::ops::Range`](https://doc.rust-lang.org/std/ops/struct.Range.html#) wrapping the lowest and highest byte of the [`Span`](https://doc.rust-lang.org/beta/proc_macro/struct.Span.html#).
I put it behind the `proc_macro_span` feature flag because many of the other functions that have a similar footprint also are annotated with it, I don't actually know if this is right.
It would be great if somebody could take a look at this, thank you very much in advanced.
This method is still only used for Literal::subspan, however the
implementation only depends on the Span component, so it is simpler and
more efficient for now to pass down only the information that is needed.
In the future, if more information about the Literal is required in the
implementation (e.g. to validate that spans line up as expected with
source text), that extra information can be added back with extra
arguments.
This builds on the symbol infrastructure built for `Ident` to replicate
the `LitKind` and `Lit` structures in rustc within the `proc_macro`
client, allowing literals to be fully created and interacted with from
the client thread. Only parsing and subspan operations still require
sync RPC.
Doing this for all unicode identifiers would require a dependency on
`unicode-normalization` and `rustc_lexer`, which is currently not
possible for `proc_macro` due to it being built concurrently with `std`
and `core`. Instead, ASCII identifiers are validated locally, and an RPC
message is used to validate unicode identifiers when needed.
String values are interned on the both the server and client when
deserializing, to avoid unnecessary copies and keep Ident cheap to copy and
move. This appears to be important for performance.
The client-side interner is based roughly on the one from rustc_span, and uses
an arena inspired by rustc_arena.
RPC messages passing symbols always include the full value. This could
potentially be optimized in the future if it is revealed to be a
performance bottleneck.
Despite now having a relevant implementaion of Display for Ident, ToString is
still specialized, as it is a hot-path for this object.
The symbol infrastructure will also be used for literals in the next
part.
This greatly reduces round-trips to fetch relevant extra information about the
token in proc macro code, and avoids RPC messages to create Group tokens.
This greatly reduces round-trips to fetch relevant extra information about the
token in proc macro code, and avoids RPC messages to create Punct tokens.
This is an experimental patch to try to reduce the codegen complexity of
TokenStream's FromIterator and Extend implementations for downstream
crates, by moving the core logic into a helper type. This might help
improve build performance of crates which depend on proc_macro as
iterators are used less, and the compiler may take less time to do
things like attempt specializations or other iterator optimizations.
The change intentionally sacrifices some optimization opportunities,
such as using the specializations for collecting iterators derived from
Vec::into_iter() into Vec.
This is one of the simpler potential approaches to reducing the amount
of code generated in crates depending on proc_macro, so it seems worth
trying before other more-involved changes.
This significantly reduces the cost of common interactions with TokenStream
when running with the CrossThread execution strategy, by reducing the number of
RPC calls required.
The change was "Show invisible delimiters (within comments) when pretty
printing". It's useful to show these delimiters, but is a breaking
change for some proc macros.
Fixes#97608.
Reduce the amount of unstable features used in libproc_macro
This makes it easier to adapt the source for stable when copying it into rust-analyzer to load rustc compiled proc macros.
This updates the standard library's documentation to use the new syntax. The
documentation is worthwhile to update as it should be more idiomatic
(particularly for features like this, which are nice for users to get acquainted
with). The general codebase is likely more hassle than benefit to update: it'll
hurt git blame, and generally updates can be done by folks updating the code if
(and when) that makes things more readable with the new format.
A few places in the compiler and library code are updated (mostly just due to
already having been done when this commit was first authored).
This feature is aimed at giving proc macros access to powers similar to
those used by builtin macros such as `format_args!` or `concat!`. These
macros are able to accept macros in place of string literal parameters,
such as the format string, as they perform recursive macro expansion
while being expanded.
This can be especially useful in many cases thanks to helper macros like
`concat!`, `stringify!` and `include_str!` which are often used to
construct string literals at compile-time in user code.
For now, this method only allows expanding macros which produce
literals, although more expresisons will be supported before the method
is stabilized.
Add proc_macro::Span::{before, after}.
This adds `proc_macro::Span::before()` and `proc_macro::Span::after()` to get a zero width span at the start or end of the span.
These are equivalent to rustc's `Span::shrink_to_lo()` and `Span::shrink_to_hi()` but with a less cryptic name. They are useful when generating diagnostlics like "missing \<thing\> after \<thing\>".
E.g.
```rust
syn::Error::new(ident.span().after(), "missing `:` after field name").into_compile_error()
```
