mozilla-central/third_party/rust/paste/src/lib.rs

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//! [![github]](https://github.com/dtolnay/paste) [![crates-io]](https://crates.io/crates/paste) [![docs-rs]](https://docs.rs/paste)
//!
//!
//! <br>
//!
//! The nightly-only [`concat_idents!`] macro in the Rust standard library is
//! notoriously underpowered in that its concatenated identifiers can only refer to
//! existing items, they can never be used to define something new.
//!
//!
//! This crate provides a flexible way to paste together identifiers in a macro,
//! including using pasted identifiers to define new items.
//!
//! This approach works with any Rust compiler 1.31+.
//!
//! <br>
//!
//! # Pasting identifiers
//!
//! Within the `paste!` macro, identifiers inside `[<`...`>]` are pasted
//! together to form a single identifier.
//!
//! ```
//! use paste::paste;
//!
//! paste! {
//! // Defines a const called `QRST`.
//! const [<Q R S T>]: &str = "success!";
//! }
//!
//! fn main() {
//! assert_eq!(
//! paste! { [<Q R S T>].len() },
//! 8,
//! );
//! }
//! ```
//!
//! <br><br>
//!
//! # More elaborate example
//!
//! The next example shows a macro that generates accessor methods for some
//! struct fields. It demonstrates how you might find it useful to bundle a
//! paste invocation inside of a macro\_rules macro.
//!
//! ```
//! use paste::paste;
//!
//! macro_rules! make_a_struct_and_getters {
//! ($name:ident { $($field:ident),* }) => {
//! // Define a struct. This expands to:
//! //
//! // pub struct S {
//! // a: String,
//! // b: String,
//! // c: String,
//! // }
//! pub struct $name {
//! $(
//! $field: String,
//! )*
//! }
//!
//! // Build an impl block with getters. This expands to:
//! //
//! // impl S {
//! // pub fn get_a(&self) -> &str { &self.a }
//! // pub fn get_b(&self) -> &str { &self.b }
//! // pub fn get_c(&self) -> &str { &self.c }
//! // }
//! paste! {
//! impl $name {
//! $(
//! pub fn [<get_ $field>](&self) -> &str {
//! &self.$field
//! }
//! )*
//! }
//! }
//! }
//! }
//!
//! make_a_struct_and_getters!(S { a, b, c });
//!
//! fn call_some_getters(s: &S) -> bool {
//! s.get_a() == s.get_b() && s.get_c().is_empty()
//! }
//! #
//! # fn main() {}
//! ```
//!
//! <br><br>
//!
//! # Case conversion
//!
//! Use `$var:lower` or `$var:upper` in the segment list to convert an
//! interpolated segment to lower- or uppercase as part of the paste. For
//! example, `[<ld_ $reg:lower _expr>]` would paste to `ld_bc_expr` if invoked
//! with $reg=`Bc`.
//!
//! Use `$var:snake` to convert CamelCase input to snake\_case.
//! Use `$var:camel` to convert snake\_case to CamelCase.
//! These compose, so for example `$var:snake:upper` would give you SCREAMING\_CASE.
//!
//! The precise Unicode conversions are as defined by [`str::to_lowercase`] and
//! [`str::to_uppercase`].
//!
//!
//! <br>
//!
//! # Pasting documentation strings
//!
//! Within the `paste!` macro, arguments to a #\[doc ...\] attribute are
//! implicitly concatenated together to form a coherent documentation string.
//!
//! ```
//! use paste::paste;
//!
//! macro_rules! method_new {
//! ($ret:ident) => {
//! paste! {
//! #[doc = "Create a new `" $ret "` object."]
//! pub fn new() -> $ret { todo!() }
//! }
//! };
//! }
//!
//! pub struct Paste {}
//!
//! method_new!(Paste); // expands to #[doc = "Create a new `Paste` object"]
//! ```
#![allow(
clippy::derive_partial_eq_without_eq,
clippy::doc_markdown,
clippy::match_same_arms,
clippy::module_name_repetitions,
clippy::needless_doctest_main,
clippy::too_many_lines
)]
extern crate proc_macro;
mod attr;
mod error;
mod segment;
use crate::attr::expand_attr;
use crate::error::{Error, Result};
use crate::segment::Segment;
use proc_macro::{Delimiter, Group, Ident, Punct, Spacing, Span, TokenStream, TokenTree};
use std::char;
use std::iter;
use std::panic;
#[proc_macro]
pub fn paste(input: TokenStream) -> TokenStream {
let mut contains_paste = false;
let flatten_single_interpolation = true;
match expand(
input.clone(),
&mut contains_paste,
flatten_single_interpolation,
) {
Ok(expanded) => {
if contains_paste {
expanded
} else {
input
}
}
Err(err) => err.to_compile_error(),
}
}
#[doc(hidden)]
#[proc_macro]
pub fn item(input: TokenStream) -> TokenStream {
paste(input)
}
#[doc(hidden)]
#[proc_macro]
pub fn expr(input: TokenStream) -> TokenStream {
paste(input)
}
fn expand(
input: TokenStream,
contains_paste: &mut bool,
flatten_single_interpolation: bool,
) -> Result<TokenStream> {
let mut expanded = TokenStream::new();
let mut lookbehind = Lookbehind::Other;
let mut prev_none_group = None::<Group>;
let mut tokens = input.into_iter().peekable();
loop {
let token = tokens.next();
if let Some(group) = prev_none_group.take() {
if match (&token, tokens.peek()) {
(Some(TokenTree::Punct(fst)), Some(TokenTree::Punct(snd))) => {
fst.as_char() == ':' && snd.as_char() == ':' && fst.spacing() == Spacing::Joint
}
_ => false,
} {
expanded.extend(group.stream());
*contains_paste = true;
} else {
expanded.extend(iter::once(TokenTree::Group(group)));
}
}
match token {
Some(TokenTree::Group(group)) => {
let delimiter = group.delimiter();
let content = group.stream();
let span = group.span();
if delimiter == Delimiter::Bracket && is_paste_operation(&content) {
let segments = parse_bracket_as_segments(content, span)?;
let pasted = segment::paste(&segments)?;
let tokens = pasted_to_tokens(pasted, span)?;
expanded.extend(tokens);
*contains_paste = true;
} else if flatten_single_interpolation
&& delimiter == Delimiter::None
&& is_single_interpolation_group(&content)
{
expanded.extend(content);
*contains_paste = true;
} else {
let mut group_contains_paste = false;
let is_attribute = delimiter == Delimiter::Bracket
&& (lookbehind == Lookbehind::Pound || lookbehind == Lookbehind::PoundBang);
let mut nested = expand(
content,
&mut group_contains_paste,
flatten_single_interpolation && !is_attribute,
)?;
if is_attribute {
nested = expand_attr(nested, span, &mut group_contains_paste)?;
}
let group = if group_contains_paste {
let mut group = Group::new(delimiter, nested);
group.set_span(span);
*contains_paste = true;
group
} else {
group.clone()
};
if delimiter != Delimiter::None {
expanded.extend(iter::once(TokenTree::Group(group)));
} else if lookbehind == Lookbehind::DoubleColon {
expanded.extend(group.stream());
*contains_paste = true;
} else {
prev_none_group = Some(group);
}
}
lookbehind = Lookbehind::Other;
}
Some(TokenTree::Punct(punct)) => {
lookbehind = match punct.as_char() {
':' if lookbehind == Lookbehind::JointColon => Lookbehind::DoubleColon,
':' if punct.spacing() == Spacing::Joint => Lookbehind::JointColon,
'#' => Lookbehind::Pound,
'!' if lookbehind == Lookbehind::Pound => Lookbehind::PoundBang,
_ => Lookbehind::Other,
};
expanded.extend(iter::once(TokenTree::Punct(punct)));
}
Some(other) => {
lookbehind = Lookbehind::Other;
expanded.extend(iter::once(other));
}
None => return Ok(expanded),
}
}
}
#[derive(PartialEq)]
enum Lookbehind {
JointColon,
DoubleColon,
Pound,
PoundBang,
Other,
}
fn is_single_interpolation_group(input: &TokenStream) -> bool {
#[derive(PartialEq)]
enum State {
Init,
Ident,
Literal,
Apostrophe,
Lifetime,
Colon1,
Colon2,
}
let mut state = State::Init;
for tt in input.clone() {
state = match (state, &tt) {
(State::Init, TokenTree::Ident(_)) => State::Ident,
(State::Init, TokenTree::Literal(_)) => State::Literal,
(State::Init, TokenTree::Punct(punct)) if punct.as_char() == '\'' => State::Apostrophe,
(State::Apostrophe, TokenTree::Ident(_)) => State::Lifetime,
(State::Ident, TokenTree::Punct(punct))
if punct.as_char() == ':' && punct.spacing() == Spacing::Joint =>
{
State::Colon1
}
(State::Colon1, TokenTree::Punct(punct))
if punct.as_char() == ':' && punct.spacing() == Spacing::Alone =>
{
State::Colon2
}
(State::Colon2, TokenTree::Ident(_)) => State::Ident,
_ => return false,
};
}
state == State::Ident || state == State::Literal || state == State::Lifetime
}
fn is_paste_operation(input: &TokenStream) -> bool {
let mut tokens = input.clone().into_iter();
match &tokens.next() {
Some(TokenTree::Punct(punct)) if punct.as_char() == '<' => {}
_ => return false,
}
let mut has_token = false;
loop {
match &tokens.next() {
Some(TokenTree::Punct(punct)) if punct.as_char() == '>' => {
return has_token && tokens.next().is_none();
}
Some(_) => has_token = true,
None => return false,
}
}
}
fn parse_bracket_as_segments(input: TokenStream, scope: Span) -> Result<Vec<Segment>> {
let mut tokens = input.into_iter().peekable();
match &tokens.next() {
Some(TokenTree::Punct(punct)) if punct.as_char() == '<' => {}
Some(wrong) => return Err(Error::new(wrong.span(), "expected `<`")),
None => return Err(Error::new(scope, "expected `[< ... >]`")),
}
let mut segments = segment::parse(&mut tokens)?;
match &tokens.next() {
Some(TokenTree::Punct(punct)) if punct.as_char() == '>' => {}
Some(wrong) => return Err(Error::new(wrong.span(), "expected `>`")),
None => return Err(Error::new(scope, "expected `[< ... >]`")),
}
if let Some(unexpected) = tokens.next() {
return Err(Error::new(
unexpected.span(),
"unexpected input, expected `[< ... >]`",
));
}
for segment in &mut segments {
if let Segment::String(string) = segment {
if string.value.starts_with("'\\u{") {
let hex = &string.value[4..string.value.len() - 2];
if let Ok(unsigned) = u32::from_str_radix(hex, 16) {
if let Some(ch) = char::from_u32(unsigned) {
string.value.clear();
string.value.push(ch);
continue;
}
}
}
if string.value.contains(&['#', '\\', '.', '+'][..])
|| string.value.starts_with("b'")
|| string.value.starts_with("b\"")
|| string.value.starts_with("br\"")
{
return Err(Error::new(string.span, "unsupported literal"));
}
let mut range = 0..string.value.len();
if string.value.starts_with("r\"") {
range.start += 2;
range.end -= 1;
} else if string.value.starts_with(&['"', '\''][..]) {
range.start += 1;
range.end -= 1;
}
string.value = string.value[range].replace('-', "_");
}
}
Ok(segments)
}
fn pasted_to_tokens(mut pasted: String, span: Span) -> Result<TokenStream> {
let mut tokens = TokenStream::new();
#[cfg(not(no_literal_fromstr))]
{
use proc_macro::{LexError, Literal};
use std::str::FromStr;
if pasted.starts_with(|ch: char| ch.is_ascii_digit()) {
let literal = match panic::catch_unwind(|| Literal::from_str(&pasted)) {
Ok(Ok(literal)) => TokenTree::Literal(literal),
Ok(Err(LexError { .. })) | Err(_) => {
return Err(Error::new(
span,
&format!("`{:?}` is not a valid literal", pasted),
));
}
};
tokens.extend(iter::once(literal));
return Ok(tokens);
}
}
if pasted.starts_with('\'') {
let mut apostrophe = TokenTree::Punct(Punct::new('\'', Spacing::Joint));
apostrophe.set_span(span);
tokens.extend(iter::once(apostrophe));
pasted.remove(0);
}
let ident = match panic::catch_unwind(|| Ident::new(&pasted, span)) {
Ok(ident) => TokenTree::Ident(ident),
Err(_) => {
return Err(Error::new(
span,
&format!("`{:?}` is not a valid identifier", pasted),
));
}
};
tokens.extend(iter::once(ident));
Ok(tokens)
}