proc_macro2/
lib.rs

1//! A wrapper around the procedural macro API of the compiler's [`proc_macro`]
2//! crate. This library serves two purposes:
3//!
4//! [`proc_macro`]: https://doc.rust-lang.org/proc_macro/
5//!
6//! - **Bring proc-macro-like functionality to other contexts like build.rs and
7//!   main.rs.** Types from `proc_macro` are entirely specific to procedural
8//!   macros and cannot ever exist in code outside of a procedural macro.
9//!   Meanwhile `proc_macro2` types may exist anywhere including non-macro code.
10//!   By developing foundational libraries like [syn] and [quote] against
11//!   `proc_macro2` rather than `proc_macro`, the procedural macro ecosystem
12//!   becomes easily applicable to many other use cases and we avoid
13//!   reimplementing non-macro equivalents of those libraries.
14//!
15//! - **Make procedural macros unit testable.** As a consequence of being
16//!   specific to procedural macros, nothing that uses `proc_macro` can be
17//!   executed from a unit test. In order for helper libraries or components of
18//!   a macro to be testable in isolation, they must be implemented using
19//!   `proc_macro2`.
20//!
21//! [syn]: https://github.com/dtolnay/syn
22//! [quote]: https://github.com/dtolnay/quote
23//!
24//! # Usage
25//!
26//! The skeleton of a typical procedural macro typically looks like this:
27//!
28//! ```
29//! extern crate proc_macro;
30//!
31//! # const IGNORE: &str = stringify! {
32//! #[proc_macro_derive(MyDerive)]
33//! # };
34//! # #[cfg(wrap_proc_macro)]
35//! pub fn my_derive(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
36//!     let input = proc_macro2::TokenStream::from(input);
37//!
38//!     let output: proc_macro2::TokenStream = {
39//!         /* transform input */
40//!         # input
41//!     };
42//!
43//!     proc_macro::TokenStream::from(output)
44//! }
45//! ```
46//!
47//! If parsing with [Syn], you'll use [`parse_macro_input!`] instead to
48//! propagate parse errors correctly back to the compiler when parsing fails.
49//!
50//! [`parse_macro_input!`]: https://docs.rs/syn/1.0/syn/macro.parse_macro_input.html
51//!
52//! # Unstable features
53//!
54//! The default feature set of proc-macro2 tracks the most recent stable
55//! compiler API. Functionality in `proc_macro` that is not yet stable is not
56//! exposed by proc-macro2 by default.
57//!
58//! To opt into the additional APIs available in the most recent nightly
59//! compiler, the `procmacro2_semver_exempt` config flag must be passed to
60//! rustc. We will polyfill those nightly-only APIs back to Rust 1.31.0. As
61//! these are unstable APIs that track the nightly compiler, minor versions of
62//! proc-macro2 may make breaking changes to them at any time.
63//!
64//! ```sh
65//! RUSTFLAGS='--cfg procmacro2_semver_exempt' cargo build
66//! ```
67//!
68//! Note that this must not only be done for your crate, but for any crate that
69//! depends on your crate. This infectious nature is intentional, as it serves
70//! as a reminder that you are outside of the normal semver guarantees.
71//!
72//! Semver exempt methods are marked as such in the proc-macro2 documentation.
73//!
74//! # Thread-Safety
75//!
76//! Most types in this crate are `!Sync` because the underlying compiler
77//! types make use of thread-local memory, meaning they cannot be accessed from
78//! a different thread.
79
80// Proc-macro2 types in rustdoc of other crates get linked to here.
81#![doc(html_root_url = "https://docs.rs/proc-macro2/1.0.6")]
82#![cfg_attr(any(proc_macro_span, super_unstable), feature(proc_macro_span))]
83#![cfg_attr(super_unstable, feature(proc_macro_raw_ident, proc_macro_def_site))]
84
85#[cfg(use_proc_macro)]
86extern crate proc_macro;
87
88use std::cmp::Ordering;
89use std::fmt;
90use std::hash::{Hash, Hasher};
91use std::iter::FromIterator;
92use std::marker;
93use std::ops::RangeBounds;
94#[cfg(procmacro2_semver_exempt)]
95use std::path::PathBuf;
96use std::rc::Rc;
97use std::str::FromStr;
98
99#[macro_use]
100mod strnom;
101mod fallback;
102
103#[cfg(not(wrap_proc_macro))]
104use crate::fallback as imp;
105#[path = "wrapper.rs"]
106#[cfg(wrap_proc_macro)]
107mod imp;
108
109/// An abstract stream of tokens, or more concretely a sequence of token trees.
110///
111/// This type provides interfaces for iterating over token trees and for
112/// collecting token trees into one stream.
113///
114/// Token stream is both the input and output of `#[proc_macro]`,
115/// `#[proc_macro_attribute]` and `#[proc_macro_derive]` definitions.
116#[derive(Clone)]
117pub struct TokenStream {
118    inner: imp::TokenStream,
119    _marker: marker::PhantomData<Rc<()>>,
120}
121
122/// Error returned from `TokenStream::from_str`.
123pub struct LexError {
124    inner: imp::LexError,
125    _marker: marker::PhantomData<Rc<()>>,
126}
127
128impl TokenStream {
129    fn _new(inner: imp::TokenStream) -> TokenStream {
130        TokenStream {
131            inner,
132            _marker: marker::PhantomData,
133        }
134    }
135
136    fn _new_stable(inner: fallback::TokenStream) -> TokenStream {
137        TokenStream {
138            inner: inner.into(),
139            _marker: marker::PhantomData,
140        }
141    }
142
143    /// Returns an empty `TokenStream` containing no token trees.
144    pub fn new() -> TokenStream {
145        TokenStream::_new(imp::TokenStream::new())
146    }
147
148    /// Checks if this `TokenStream` is empty.
149    pub fn is_empty(&self) -> bool {
150        self.inner.is_empty()
151    }
152}
153
154/// `TokenStream::default()` returns an empty stream,
155/// i.e. this is equivalent with `TokenStream::new()`.
156impl Default for TokenStream {
157    fn default() -> Self {
158        TokenStream::new()
159    }
160}
161
162/// Attempts to break the string into tokens and parse those tokens into a token
163/// stream.
164///
165/// May fail for a number of reasons, for example, if the string contains
166/// unbalanced delimiters or characters not existing in the language.
167///
168/// NOTE: Some errors may cause panics instead of returning `LexError`. We
169/// reserve the right to change these errors into `LexError`s later.
170impl FromStr for TokenStream {
171    type Err = LexError;
172
173    fn from_str(src: &str) -> Result<TokenStream, LexError> {
174        let e = src.parse().map_err(|e| LexError {
175            inner: e,
176            _marker: marker::PhantomData,
177        })?;
178        Ok(TokenStream::_new(e))
179    }
180}
181
182#[cfg(use_proc_macro)]
183impl From<proc_macro::TokenStream> for TokenStream {
184    fn from(inner: proc_macro::TokenStream) -> TokenStream {
185        TokenStream::_new(inner.into())
186    }
187}
188
189#[cfg(use_proc_macro)]
190impl From<TokenStream> for proc_macro::TokenStream {
191    fn from(inner: TokenStream) -> proc_macro::TokenStream {
192        inner.inner.into()
193    }
194}
195
196impl From<TokenTree> for TokenStream {
197    fn from(token: TokenTree) -> Self {
198        TokenStream::_new(imp::TokenStream::from(token))
199    }
200}
201
202impl Extend<TokenTree> for TokenStream {
203    fn extend<I: IntoIterator<Item = TokenTree>>(&mut self, streams: I) {
204        self.inner.extend(streams)
205    }
206}
207
208impl Extend<TokenStream> for TokenStream {
209    fn extend<I: IntoIterator<Item = TokenStream>>(&mut self, streams: I) {
210        self.inner
211            .extend(streams.into_iter().map(|stream| stream.inner))
212    }
213}
214
215/// Collects a number of token trees into a single stream.
216impl FromIterator<TokenTree> for TokenStream {
217    fn from_iter<I: IntoIterator<Item = TokenTree>>(streams: I) -> Self {
218        TokenStream::_new(streams.into_iter().collect())
219    }
220}
221impl FromIterator<TokenStream> for TokenStream {
222    fn from_iter<I: IntoIterator<Item = TokenStream>>(streams: I) -> Self {
223        TokenStream::_new(streams.into_iter().map(|i| i.inner).collect())
224    }
225}
226
227/// Prints the token stream as a string that is supposed to be losslessly
228/// convertible back into the same token stream (modulo spans), except for
229/// possibly `TokenTree::Group`s with `Delimiter::None` delimiters and negative
230/// numeric literals.
231impl fmt::Display for TokenStream {
232    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
233        self.inner.fmt(f)
234    }
235}
236
237/// Prints token in a form convenient for debugging.
238impl fmt::Debug for TokenStream {
239    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
240        self.inner.fmt(f)
241    }
242}
243
244impl fmt::Debug for LexError {
245    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
246        self.inner.fmt(f)
247    }
248}
249
250/// The source file of a given `Span`.
251///
252/// This type is semver exempt and not exposed by default.
253#[cfg(procmacro2_semver_exempt)]
254#[derive(Clone, PartialEq, Eq)]
255pub struct SourceFile {
256    inner: imp::SourceFile,
257    _marker: marker::PhantomData<Rc<()>>,
258}
259
260#[cfg(procmacro2_semver_exempt)]
261impl SourceFile {
262    fn _new(inner: imp::SourceFile) -> Self {
263        SourceFile {
264            inner,
265            _marker: marker::PhantomData,
266        }
267    }
268
269    /// Get the path to this source file.
270    ///
271    /// ### Note
272    ///
273    /// If the code span associated with this `SourceFile` was generated by an
274    /// external macro, this may not be an actual path on the filesystem. Use
275    /// [`is_real`] to check.
276    ///
277    /// Also note that even if `is_real` returns `true`, if
278    /// `--remap-path-prefix` was passed on the command line, the path as given
279    /// may not actually be valid.
280    ///
281    /// [`is_real`]: #method.is_real
282    pub fn path(&self) -> PathBuf {
283        self.inner.path()
284    }
285
286    /// Returns `true` if this source file is a real source file, and not
287    /// generated by an external macro's expansion.
288    pub fn is_real(&self) -> bool {
289        self.inner.is_real()
290    }
291}
292
293#[cfg(procmacro2_semver_exempt)]
294impl fmt::Debug for SourceFile {
295    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
296        self.inner.fmt(f)
297    }
298}
299
300/// A line-column pair representing the start or end of a `Span`.
301///
302/// This type is semver exempt and not exposed by default.
303#[cfg(span_locations)]
304#[derive(Copy, Clone, Debug, PartialEq, Eq)]
305pub struct LineColumn {
306    /// The 1-indexed line in the source file on which the span starts or ends
307    /// (inclusive).
308    pub line: usize,
309    /// The 0-indexed column (in UTF-8 characters) in the source file on which
310    /// the span starts or ends (inclusive).
311    pub column: usize,
312}
313
314/// A region of source code, along with macro expansion information.
315#[derive(Copy, Clone)]
316pub struct Span {
317    inner: imp::Span,
318    _marker: marker::PhantomData<Rc<()>>,
319}
320
321impl Span {
322    fn _new(inner: imp::Span) -> Span {
323        Span {
324            inner,
325            _marker: marker::PhantomData,
326        }
327    }
328
329    fn _new_stable(inner: fallback::Span) -> Span {
330        Span {
331            inner: inner.into(),
332            _marker: marker::PhantomData,
333        }
334    }
335
336    /// The span of the invocation of the current procedural macro.
337    ///
338    /// Identifiers created with this span will be resolved as if they were
339    /// written directly at the macro call location (call-site hygiene) and
340    /// other code at the macro call site will be able to refer to them as well.
341    pub fn call_site() -> Span {
342        Span::_new(imp::Span::call_site())
343    }
344
345    /// A span that resolves at the macro definition site.
346    ///
347    /// This method is semver exempt and not exposed by default.
348    #[cfg(procmacro2_semver_exempt)]
349    pub fn def_site() -> Span {
350        Span::_new(imp::Span::def_site())
351    }
352
353    /// Creates a new span with the same line/column information as `self` but
354    /// that resolves symbols as though it were at `other`.
355    ///
356    /// This method is semver exempt and not exposed by default.
357    #[cfg(procmacro2_semver_exempt)]
358    pub fn resolved_at(&self, other: Span) -> Span {
359        Span::_new(self.inner.resolved_at(other.inner))
360    }
361
362    /// Creates a new span with the same name resolution behavior as `self` but
363    /// with the line/column information of `other`.
364    ///
365    /// This method is semver exempt and not exposed by default.
366    #[cfg(procmacro2_semver_exempt)]
367    pub fn located_at(&self, other: Span) -> Span {
368        Span::_new(self.inner.located_at(other.inner))
369    }
370
371    /// Convert `proc_macro2::Span` to `proc_macro::Span`.
372    ///
373    /// This method is available when building with a nightly compiler, or when
374    /// building with rustc 1.29+ *without* semver exempt features.
375    ///
376    /// # Panics
377    ///
378    /// Panics if called from outside of a procedural macro. Unlike
379    /// `proc_macro2::Span`, the `proc_macro::Span` type can only exist within
380    /// the context of a procedural macro invocation.
381    #[cfg(wrap_proc_macro)]
382    pub fn unwrap(self) -> proc_macro::Span {
383        self.inner.unwrap()
384    }
385
386    // Soft deprecated. Please use Span::unwrap.
387    #[cfg(wrap_proc_macro)]
388    #[doc(hidden)]
389    pub fn unstable(self) -> proc_macro::Span {
390        self.unwrap()
391    }
392
393    /// The original source file into which this span points.
394    ///
395    /// This method is semver exempt and not exposed by default.
396    #[cfg(procmacro2_semver_exempt)]
397    pub fn source_file(&self) -> SourceFile {
398        SourceFile::_new(self.inner.source_file())
399    }
400
401    /// Get the starting line/column in the source file for this span.
402    ///
403    /// This method requires the `"span-locations"` feature to be enabled.
404    #[cfg(span_locations)]
405    pub fn start(&self) -> LineColumn {
406        let imp::LineColumn { line, column } = self.inner.start();
407        LineColumn { line, column }
408    }
409
410    /// Get the ending line/column in the source file for this span.
411    ///
412    /// This method requires the `"span-locations"` feature to be enabled.
413    #[cfg(span_locations)]
414    pub fn end(&self) -> LineColumn {
415        let imp::LineColumn { line, column } = self.inner.end();
416        LineColumn { line, column }
417    }
418
419    /// Create a new span encompassing `self` and `other`.
420    ///
421    /// Returns `None` if `self` and `other` are from different files.
422    ///
423    /// Warning: the underlying [`proc_macro::Span::join`] method is
424    /// nightly-only. When called from within a procedural macro not using a
425    /// nightly compiler, this method will always return `None`.
426    ///
427    /// [`proc_macro::Span::join`]: https://doc.rust-lang.org/proc_macro/struct.Span.html#method.join
428    pub fn join(&self, other: Span) -> Option<Span> {
429        self.inner.join(other.inner).map(Span::_new)
430    }
431
432    /// Compares two spans to see if they're equal.
433    ///
434    /// This method is semver exempt and not exposed by default.
435    #[cfg(procmacro2_semver_exempt)]
436    pub fn eq(&self, other: &Span) -> bool {
437        self.inner.eq(&other.inner)
438    }
439}
440
441/// Prints a span in a form convenient for debugging.
442impl fmt::Debug for Span {
443    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
444        self.inner.fmt(f)
445    }
446}
447
448/// A single token or a delimited sequence of token trees (e.g. `[1, (), ..]`).
449#[derive(Clone)]
450pub enum TokenTree {
451    /// A token stream surrounded by bracket delimiters.
452    Group(Group),
453    /// An identifier.
454    Ident(Ident),
455    /// A single punctuation character (`+`, `,`, `$`, etc.).
456    Punct(Punct),
457    /// A literal character (`'a'`), string (`"hello"`), number (`2.3`), etc.
458    Literal(Literal),
459}
460
461impl TokenTree {
462    /// Returns the span of this tree, delegating to the `span` method of
463    /// the contained token or a delimited stream.
464    pub fn span(&self) -> Span {
465        match *self {
466            TokenTree::Group(ref t) => t.span(),
467            TokenTree::Ident(ref t) => t.span(),
468            TokenTree::Punct(ref t) => t.span(),
469            TokenTree::Literal(ref t) => t.span(),
470        }
471    }
472
473    /// Configures the span for *only this token*.
474    ///
475    /// Note that if this token is a `Group` then this method will not configure
476    /// the span of each of the internal tokens, this will simply delegate to
477    /// the `set_span` method of each variant.
478    pub fn set_span(&mut self, span: Span) {
479        match *self {
480            TokenTree::Group(ref mut t) => t.set_span(span),
481            TokenTree::Ident(ref mut t) => t.set_span(span),
482            TokenTree::Punct(ref mut t) => t.set_span(span),
483            TokenTree::Literal(ref mut t) => t.set_span(span),
484        }
485    }
486}
487
488impl From<Group> for TokenTree {
489    fn from(g: Group) -> TokenTree {
490        TokenTree::Group(g)
491    }
492}
493
494impl From<Ident> for TokenTree {
495    fn from(g: Ident) -> TokenTree {
496        TokenTree::Ident(g)
497    }
498}
499
500impl From<Punct> for TokenTree {
501    fn from(g: Punct) -> TokenTree {
502        TokenTree::Punct(g)
503    }
504}
505
506impl From<Literal> for TokenTree {
507    fn from(g: Literal) -> TokenTree {
508        TokenTree::Literal(g)
509    }
510}
511
512/// Prints the token tree as a string that is supposed to be losslessly
513/// convertible back into the same token tree (modulo spans), except for
514/// possibly `TokenTree::Group`s with `Delimiter::None` delimiters and negative
515/// numeric literals.
516impl fmt::Display for TokenTree {
517    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
518        match *self {
519            TokenTree::Group(ref t) => t.fmt(f),
520            TokenTree::Ident(ref t) => t.fmt(f),
521            TokenTree::Punct(ref t) => t.fmt(f),
522            TokenTree::Literal(ref t) => t.fmt(f),
523        }
524    }
525}
526
527/// Prints token tree in a form convenient for debugging.
528impl fmt::Debug for TokenTree {
529    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
530        // Each of these has the name in the struct type in the derived debug,
531        // so don't bother with an extra layer of indirection
532        match *self {
533            TokenTree::Group(ref t) => t.fmt(f),
534            TokenTree::Ident(ref t) => {
535                let mut debug = f.debug_struct("Ident");
536                debug.field("sym", &format_args!("{}", t));
537                imp::debug_span_field_if_nontrivial(&mut debug, t.span().inner);
538                debug.finish()
539            }
540            TokenTree::Punct(ref t) => t.fmt(f),
541            TokenTree::Literal(ref t) => t.fmt(f),
542        }
543    }
544}
545
546/// A delimited token stream.
547///
548/// A `Group` internally contains a `TokenStream` which is surrounded by
549/// `Delimiter`s.
550#[derive(Clone)]
551pub struct Group {
552    inner: imp::Group,
553}
554
555/// Describes how a sequence of token trees is delimited.
556#[derive(Copy, Clone, Debug, Eq, PartialEq)]
557pub enum Delimiter {
558    /// `( ... )`
559    Parenthesis,
560    /// `{ ... }`
561    Brace,
562    /// `[ ... ]`
563    Bracket,
564    /// `Ø ... Ø`
565    ///
566    /// An implicit delimiter, that may, for example, appear around tokens
567    /// coming from a "macro variable" `$var`. It is important to preserve
568    /// operator priorities in cases like `$var * 3` where `$var` is `1 + 2`.
569    /// Implicit delimiters may not survive roundtrip of a token stream through
570    /// a string.
571    None,
572}
573
574impl Group {
575    fn _new(inner: imp::Group) -> Self {
576        Group { inner }
577    }
578
579    fn _new_stable(inner: fallback::Group) -> Self {
580        Group {
581            inner: inner.into(),
582        }
583    }
584
585    /// Creates a new `Group` with the given delimiter and token stream.
586    ///
587    /// This constructor will set the span for this group to
588    /// `Span::call_site()`. To change the span you can use the `set_span`
589    /// method below.
590    pub fn new(delimiter: Delimiter, stream: TokenStream) -> Group {
591        Group {
592            inner: imp::Group::new(delimiter, stream.inner),
593        }
594    }
595
596    /// Returns the delimiter of this `Group`
597    pub fn delimiter(&self) -> Delimiter {
598        self.inner.delimiter()
599    }
600
601    /// Returns the `TokenStream` of tokens that are delimited in this `Group`.
602    ///
603    /// Note that the returned token stream does not include the delimiter
604    /// returned above.
605    pub fn stream(&self) -> TokenStream {
606        TokenStream::_new(self.inner.stream())
607    }
608
609    /// Returns the span for the delimiters of this token stream, spanning the
610    /// entire `Group`.
611    ///
612    /// ```text
613    /// pub fn span(&self) -> Span {
614    ///            ^^^^^^^
615    /// ```
616    pub fn span(&self) -> Span {
617        Span::_new(self.inner.span())
618    }
619
620    /// Returns the span pointing to the opening delimiter of this group.
621    ///
622    /// ```text
623    /// pub fn span_open(&self) -> Span {
624    ///                 ^
625    /// ```
626    pub fn span_open(&self) -> Span {
627        Span::_new(self.inner.span_open())
628    }
629
630    /// Returns the span pointing to the closing delimiter of this group.
631    ///
632    /// ```text
633    /// pub fn span_close(&self) -> Span {
634    ///                        ^
635    /// ```
636    pub fn span_close(&self) -> Span {
637        Span::_new(self.inner.span_close())
638    }
639
640    /// Configures the span for this `Group`'s delimiters, but not its internal
641    /// tokens.
642    ///
643    /// This method will **not** set the span of all the internal tokens spanned
644    /// by this group, but rather it will only set the span of the delimiter
645    /// tokens at the level of the `Group`.
646    pub fn set_span(&mut self, span: Span) {
647        self.inner.set_span(span.inner)
648    }
649}
650
651/// Prints the group as a string that should be losslessly convertible back
652/// into the same group (modulo spans), except for possibly `TokenTree::Group`s
653/// with `Delimiter::None` delimiters.
654impl fmt::Display for Group {
655    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
656        fmt::Display::fmt(&self.inner, formatter)
657    }
658}
659
660impl fmt::Debug for Group {
661    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
662        fmt::Debug::fmt(&self.inner, formatter)
663    }
664}
665
666/// An `Punct` is an single punctuation character like `+`, `-` or `#`.
667///
668/// Multicharacter operators like `+=` are represented as two instances of
669/// `Punct` with different forms of `Spacing` returned.
670#[derive(Clone)]
671pub struct Punct {
672    op: char,
673    spacing: Spacing,
674    span: Span,
675}
676
677/// Whether an `Punct` is followed immediately by another `Punct` or followed by
678/// another token or whitespace.
679#[derive(Copy, Clone, Debug, Eq, PartialEq)]
680pub enum Spacing {
681    /// E.g. `+` is `Alone` in `+ =`, `+ident` or `+()`.
682    Alone,
683    /// E.g. `+` is `Joint` in `+=` or `'` is `Joint` in `'#`.
684    ///
685    /// Additionally, single quote `'` can join with identifiers to form
686    /// lifetimes `'ident`.
687    Joint,
688}
689
690impl Punct {
691    /// Creates a new `Punct` from the given character and spacing.
692    ///
693    /// The `ch` argument must be a valid punctuation character permitted by the
694    /// language, otherwise the function will panic.
695    ///
696    /// The returned `Punct` will have the default span of `Span::call_site()`
697    /// which can be further configured with the `set_span` method below.
698    pub fn new(op: char, spacing: Spacing) -> Punct {
699        Punct {
700            op,
701            spacing,
702            span: Span::call_site(),
703        }
704    }
705
706    /// Returns the value of this punctuation character as `char`.
707    pub fn as_char(&self) -> char {
708        self.op
709    }
710
711    /// Returns the spacing of this punctuation character, indicating whether
712    /// it's immediately followed by another `Punct` in the token stream, so
713    /// they can potentially be combined into a multicharacter operator
714    /// (`Joint`), or it's followed by some other token or whitespace (`Alone`)
715    /// so the operator has certainly ended.
716    pub fn spacing(&self) -> Spacing {
717        self.spacing
718    }
719
720    /// Returns the span for this punctuation character.
721    pub fn span(&self) -> Span {
722        self.span
723    }
724
725    /// Configure the span for this punctuation character.
726    pub fn set_span(&mut self, span: Span) {
727        self.span = span;
728    }
729}
730
731/// Prints the punctuation character as a string that should be losslessly
732/// convertible back into the same character.
733impl fmt::Display for Punct {
734    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
735        self.op.fmt(f)
736    }
737}
738
739impl fmt::Debug for Punct {
740    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
741        let mut debug = fmt.debug_struct("Punct");
742        debug.field("op", &self.op);
743        debug.field("spacing", &self.spacing);
744        imp::debug_span_field_if_nontrivial(&mut debug, self.span.inner);
745        debug.finish()
746    }
747}
748
749/// A word of Rust code, which may be a keyword or legal variable name.
750///
751/// An identifier consists of at least one Unicode code point, the first of
752/// which has the XID_Start property and the rest of which have the XID_Continue
753/// property.
754///
755/// - The empty string is not an identifier. Use `Option<Ident>`.
756/// - A lifetime is not an identifier. Use `syn::Lifetime` instead.
757///
758/// An identifier constructed with `Ident::new` is permitted to be a Rust
759/// keyword, though parsing one through its [`Parse`] implementation rejects
760/// Rust keywords. Use `input.call(Ident::parse_any)` when parsing to match the
761/// behaviour of `Ident::new`.
762///
763/// [`Parse`]: https://docs.rs/syn/1.0/syn/parse/trait.Parse.html
764///
765/// # Examples
766///
767/// A new ident can be created from a string using the `Ident::new` function.
768/// A span must be provided explicitly which governs the name resolution
769/// behavior of the resulting identifier.
770///
771/// ```
772/// use proc_macro2::{Ident, Span};
773///
774/// fn main() {
775///     let call_ident = Ident::new("calligraphy", Span::call_site());
776///
777///     println!("{}", call_ident);
778/// }
779/// ```
780///
781/// An ident can be interpolated into a token stream using the `quote!` macro.
782///
783/// ```
784/// use proc_macro2::{Ident, Span};
785/// use quote::quote;
786///
787/// fn main() {
788///     let ident = Ident::new("demo", Span::call_site());
789///
790///     // Create a variable binding whose name is this ident.
791///     let expanded = quote! { let #ident = 10; };
792///
793///     // Create a variable binding with a slightly different name.
794///     let temp_ident = Ident::new(&format!("new_{}", ident), Span::call_site());
795///     let expanded = quote! { let #temp_ident = 10; };
796/// }
797/// ```
798///
799/// A string representation of the ident is available through the `to_string()`
800/// method.
801///
802/// ```
803/// # use proc_macro2::{Ident, Span};
804/// #
805/// # let ident = Ident::new("another_identifier", Span::call_site());
806/// #
807/// // Examine the ident as a string.
808/// let ident_string = ident.to_string();
809/// if ident_string.len() > 60 {
810///     println!("Very long identifier: {}", ident_string)
811/// }
812/// ```
813#[derive(Clone)]
814pub struct Ident {
815    inner: imp::Ident,
816    _marker: marker::PhantomData<Rc<()>>,
817}
818
819impl Ident {
820    fn _new(inner: imp::Ident) -> Ident {
821        Ident {
822            inner,
823            _marker: marker::PhantomData,
824        }
825    }
826
827    /// Creates a new `Ident` with the given `string` as well as the specified
828    /// `span`.
829    ///
830    /// The `string` argument must be a valid identifier permitted by the
831    /// language, otherwise the function will panic.
832    ///
833    /// Note that `span`, currently in rustc, configures the hygiene information
834    /// for this identifier.
835    ///
836    /// As of this time `Span::call_site()` explicitly opts-in to "call-site"
837    /// hygiene meaning that identifiers created with this span will be resolved
838    /// as if they were written directly at the location of the macro call, and
839    /// other code at the macro call site will be able to refer to them as well.
840    ///
841    /// Later spans like `Span::def_site()` will allow to opt-in to
842    /// "definition-site" hygiene meaning that identifiers created with this
843    /// span will be resolved at the location of the macro definition and other
844    /// code at the macro call site will not be able to refer to them.
845    ///
846    /// Due to the current importance of hygiene this constructor, unlike other
847    /// tokens, requires a `Span` to be specified at construction.
848    ///
849    /// # Panics
850    ///
851    /// Panics if the input string is neither a keyword nor a legal variable
852    /// name. If you are not sure whether the string contains an identifier and
853    /// need to handle an error case, use
854    /// <a href="https://docs.rs/syn/1.0/syn/fn.parse_str.html"><code
855    ///   style="padding-right:0;">syn::parse_str</code></a><code
856    ///   style="padding-left:0;">::&lt;Ident&gt;</code>
857    /// rather than `Ident::new`.
858    pub fn new(string: &str, span: Span) -> Ident {
859        Ident::_new(imp::Ident::new(string, span.inner))
860    }
861
862    /// Same as `Ident::new`, but creates a raw identifier (`r#ident`).
863    ///
864    /// This method is semver exempt and not exposed by default.
865    #[cfg(procmacro2_semver_exempt)]
866    pub fn new_raw(string: &str, span: Span) -> Ident {
867        Ident::_new_raw(string, span)
868    }
869
870    fn _new_raw(string: &str, span: Span) -> Ident {
871        Ident::_new(imp::Ident::new_raw(string, span.inner))
872    }
873
874    /// Returns the span of this `Ident`.
875    pub fn span(&self) -> Span {
876        Span::_new(self.inner.span())
877    }
878
879    /// Configures the span of this `Ident`, possibly changing its hygiene
880    /// context.
881    pub fn set_span(&mut self, span: Span) {
882        self.inner.set_span(span.inner);
883    }
884}
885
886impl PartialEq for Ident {
887    fn eq(&self, other: &Ident) -> bool {
888        self.inner == other.inner
889    }
890}
891
892impl<T> PartialEq<T> for Ident
893where
894    T: ?Sized + AsRef<str>,
895{
896    fn eq(&self, other: &T) -> bool {
897        self.inner == other
898    }
899}
900
901impl Eq for Ident {}
902
903impl PartialOrd for Ident {
904    fn partial_cmp(&self, other: &Ident) -> Option<Ordering> {
905        Some(self.cmp(other))
906    }
907}
908
909impl Ord for Ident {
910    fn cmp(&self, other: &Ident) -> Ordering {
911        self.to_string().cmp(&other.to_string())
912    }
913}
914
915impl Hash for Ident {
916    fn hash<H: Hasher>(&self, hasher: &mut H) {
917        self.to_string().hash(hasher)
918    }
919}
920
921/// Prints the identifier as a string that should be losslessly convertible back
922/// into the same identifier.
923impl fmt::Display for Ident {
924    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
925        self.inner.fmt(f)
926    }
927}
928
929impl fmt::Debug for Ident {
930    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
931        self.inner.fmt(f)
932    }
933}
934
935/// A literal string (`"hello"`), byte string (`b"hello"`), character (`'a'`),
936/// byte character (`b'a'`), an integer or floating point number with or without
937/// a suffix (`1`, `1u8`, `2.3`, `2.3f32`).
938///
939/// Boolean literals like `true` and `false` do not belong here, they are
940/// `Ident`s.
941#[derive(Clone)]
942pub struct Literal {
943    inner: imp::Literal,
944    _marker: marker::PhantomData<Rc<()>>,
945}
946
947macro_rules! suffixed_int_literals {
948    ($($name:ident => $kind:ident,)*) => ($(
949        /// Creates a new suffixed integer literal with the specified value.
950        ///
951        /// This function will create an integer like `1u32` where the integer
952        /// value specified is the first part of the token and the integral is
953        /// also suffixed at the end. Literals created from negative numbers may
954        /// not survive rountrips through `TokenStream` or strings and may be
955        /// broken into two tokens (`-` and positive literal).
956        ///
957        /// Literals created through this method have the `Span::call_site()`
958        /// span by default, which can be configured with the `set_span` method
959        /// below.
960        pub fn $name(n: $kind) -> Literal {
961            Literal::_new(imp::Literal::$name(n))
962        }
963    )*)
964}
965
966macro_rules! unsuffixed_int_literals {
967    ($($name:ident => $kind:ident,)*) => ($(
968        /// Creates a new unsuffixed integer literal with the specified value.
969        ///
970        /// This function will create an integer like `1` where the integer
971        /// value specified is the first part of the token. No suffix is
972        /// specified on this token, meaning that invocations like
973        /// `Literal::i8_unsuffixed(1)` are equivalent to
974        /// `Literal::u32_unsuffixed(1)`. Literals created from negative numbers
975        /// may not survive rountrips through `TokenStream` or strings and may
976        /// be broken into two tokens (`-` and positive literal).
977        ///
978        /// Literals created through this method have the `Span::call_site()`
979        /// span by default, which can be configured with the `set_span` method
980        /// below.
981        pub fn $name(n: $kind) -> Literal {
982            Literal::_new(imp::Literal::$name(n))
983        }
984    )*)
985}
986
987impl Literal {
988    fn _new(inner: imp::Literal) -> Literal {
989        Literal {
990            inner,
991            _marker: marker::PhantomData,
992        }
993    }
994
995    fn _new_stable(inner: fallback::Literal) -> Literal {
996        Literal {
997            inner: inner.into(),
998            _marker: marker::PhantomData,
999        }
1000    }
1001
1002    suffixed_int_literals! {
1003        u8_suffixed => u8,
1004        u16_suffixed => u16,
1005        u32_suffixed => u32,
1006        u64_suffixed => u64,
1007        u128_suffixed => u128,
1008        usize_suffixed => usize,
1009        i8_suffixed => i8,
1010        i16_suffixed => i16,
1011        i32_suffixed => i32,
1012        i64_suffixed => i64,
1013        i128_suffixed => i128,
1014        isize_suffixed => isize,
1015    }
1016
1017    unsuffixed_int_literals! {
1018        u8_unsuffixed => u8,
1019        u16_unsuffixed => u16,
1020        u32_unsuffixed => u32,
1021        u64_unsuffixed => u64,
1022        u128_unsuffixed => u128,
1023        usize_unsuffixed => usize,
1024        i8_unsuffixed => i8,
1025        i16_unsuffixed => i16,
1026        i32_unsuffixed => i32,
1027        i64_unsuffixed => i64,
1028        i128_unsuffixed => i128,
1029        isize_unsuffixed => isize,
1030    }
1031
1032    /// Creates a new unsuffixed floating-point literal.
1033    ///
1034    /// This constructor is similar to those like `Literal::i8_unsuffixed` where
1035    /// the float's value is emitted directly into the token but no suffix is
1036    /// used, so it may be inferred to be a `f64` later in the compiler.
1037    /// Literals created from negative numbers may not survive rountrips through
1038    /// `TokenStream` or strings and may be broken into two tokens (`-` and
1039    /// positive literal).
1040    ///
1041    /// # Panics
1042    ///
1043    /// This function requires that the specified float is finite, for example
1044    /// if it is infinity or NaN this function will panic.
1045    pub fn f64_unsuffixed(f: f64) -> Literal {
1046        assert!(f.is_finite());
1047        Literal::_new(imp::Literal::f64_unsuffixed(f))
1048    }
1049
1050    /// Creates a new suffixed floating-point literal.
1051    ///
1052    /// This constructor will create a literal like `1.0f64` where the value
1053    /// specified is the preceding part of the token and `f64` is the suffix of
1054    /// the token. This token will always be inferred to be an `f64` in the
1055    /// compiler. Literals created from negative numbers may not survive
1056    /// rountrips through `TokenStream` or strings and may be broken into two
1057    /// tokens (`-` and positive literal).
1058    ///
1059    /// # Panics
1060    ///
1061    /// This function requires that the specified float is finite, for example
1062    /// if it is infinity or NaN this function will panic.
1063    pub fn f64_suffixed(f: f64) -> Literal {
1064        assert!(f.is_finite());
1065        Literal::_new(imp::Literal::f64_suffixed(f))
1066    }
1067
1068    /// Creates a new unsuffixed floating-point literal.
1069    ///
1070    /// This constructor is similar to those like `Literal::i8_unsuffixed` where
1071    /// the float's value is emitted directly into the token but no suffix is
1072    /// used, so it may be inferred to be a `f64` later in the compiler.
1073    /// Literals created from negative numbers may not survive rountrips through
1074    /// `TokenStream` or strings and may be broken into two tokens (`-` and
1075    /// positive literal).
1076    ///
1077    /// # Panics
1078    ///
1079    /// This function requires that the specified float is finite, for example
1080    /// if it is infinity or NaN this function will panic.
1081    pub fn f32_unsuffixed(f: f32) -> Literal {
1082        assert!(f.is_finite());
1083        Literal::_new(imp::Literal::f32_unsuffixed(f))
1084    }
1085
1086    /// Creates a new suffixed floating-point literal.
1087    ///
1088    /// This constructor will create a literal like `1.0f32` where the value
1089    /// specified is the preceding part of the token and `f32` is the suffix of
1090    /// the token. This token will always be inferred to be an `f32` in the
1091    /// compiler. Literals created from negative numbers may not survive
1092    /// rountrips through `TokenStream` or strings and may be broken into two
1093    /// tokens (`-` and positive literal).
1094    ///
1095    /// # Panics
1096    ///
1097    /// This function requires that the specified float is finite, for example
1098    /// if it is infinity or NaN this function will panic.
1099    pub fn f32_suffixed(f: f32) -> Literal {
1100        assert!(f.is_finite());
1101        Literal::_new(imp::Literal::f32_suffixed(f))
1102    }
1103
1104    /// String literal.
1105    pub fn string(string: &str) -> Literal {
1106        Literal::_new(imp::Literal::string(string))
1107    }
1108
1109    /// Character literal.
1110    pub fn character(ch: char) -> Literal {
1111        Literal::_new(imp::Literal::character(ch))
1112    }
1113
1114    /// Byte string literal.
1115    pub fn byte_string(s: &[u8]) -> Literal {
1116        Literal::_new(imp::Literal::byte_string(s))
1117    }
1118
1119    /// Returns the span encompassing this literal.
1120    pub fn span(&self) -> Span {
1121        Span::_new(self.inner.span())
1122    }
1123
1124    /// Configures the span associated for this literal.
1125    pub fn set_span(&mut self, span: Span) {
1126        self.inner.set_span(span.inner);
1127    }
1128
1129    /// Returns a `Span` that is a subset of `self.span()` containing only
1130    /// the source bytes in range `range`. Returns `None` if the would-be
1131    /// trimmed span is outside the bounds of `self`.
1132    ///
1133    /// Warning: the underlying [`proc_macro::Literal::subspan`] method is
1134    /// nightly-only. When called from within a procedural macro not using a
1135    /// nightly compiler, this method will always return `None`.
1136    ///
1137    /// [`proc_macro::Literal::subspan`]: https://doc.rust-lang.org/proc_macro/struct.Literal.html#method.subspan
1138    pub fn subspan<R: RangeBounds<usize>>(&self, range: R) -> Option<Span> {
1139        self.inner.subspan(range).map(Span::_new)
1140    }
1141}
1142
1143impl fmt::Debug for Literal {
1144    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1145        self.inner.fmt(f)
1146    }
1147}
1148
1149impl fmt::Display for Literal {
1150    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1151        self.inner.fmt(f)
1152    }
1153}
1154
1155/// Public implementation details for the `TokenStream` type, such as iterators.
1156pub mod token_stream {
1157    use std::fmt;
1158    use std::marker;
1159    use std::rc::Rc;
1160
1161    pub use crate::TokenStream;
1162    use crate::{imp, TokenTree};
1163
1164    /// An iterator over `TokenStream`'s `TokenTree`s.
1165    ///
1166    /// The iteration is "shallow", e.g. the iterator doesn't recurse into
1167    /// delimited groups, and returns whole groups as token trees.
1168    #[derive(Clone)]
1169    pub struct IntoIter {
1170        inner: imp::TokenTreeIter,
1171        _marker: marker::PhantomData<Rc<()>>,
1172    }
1173
1174    impl Iterator for IntoIter {
1175        type Item = TokenTree;
1176
1177        fn next(&mut self) -> Option<TokenTree> {
1178            self.inner.next()
1179        }
1180    }
1181
1182    impl fmt::Debug for IntoIter {
1183        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1184            self.inner.fmt(f)
1185        }
1186    }
1187
1188    impl IntoIterator for TokenStream {
1189        type Item = TokenTree;
1190        type IntoIter = IntoIter;
1191
1192        fn into_iter(self) -> IntoIter {
1193            IntoIter {
1194                inner: self.inner.into_iter(),
1195                _marker: marker::PhantomData,
1196            }
1197        }
1198    }
1199}