library/proc_macro/src/lib.rs

   1 //! A support library for macro authors when defining new macros.
   2 //!
   3 //! This library, provided by the standard distribution, provides the types
   4 //! consumed in the interfaces of procedurally defined macro definitions such as
   5 //! function-like macros `#[proc_macro]`, macro attributes `#[proc_macro_attribute]` and
   6 //! custom derive attributes`#[proc_macro_derive]`.
   7 //!
   8 //! See [the book] for more.
   9 //!
  10 //! [the book]: ../book/ch19-06-macros.html#procedural-macros-for-generating-code-from-attributes
  11
  12 #![stable(feature = "proc_macro_lib", since = "1.15.0")]
  13 #![deny(missing_docs)]
  14 #![doc(
  15     html_root_url = "https://doc.rust-lang.org/nightly/",
  16     html_playground_url = "https://play.rust-lang.org/",
  17     issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/",
  18     test(no_crate_inject, attr(deny(warnings))),
  19     test(attr(allow(dead_code, deprecated, unused_variables, unused_mut)))
  20 )]
  21 #![feature(rustc_allow_const_fn_unstable)]
  22 #![feature(nll)]
  23 #![feature(staged_api)]
  24 #![feature(const_fn)]
  25 #![feature(const_fn_fn_ptr_basics)]
  26 #![feature(allow_internal_unstable)]
  27 #![feature(decl_macro)]
  28 #![feature(extern_types)]
  29 #![feature(in_band_lifetimes)]
  30 #![feature(negative_impls)]
  31 #![cfg_attr(bootstrap, feature(optin_builtin_traits))]
  32 #![cfg_attr(not(bootstrap), feature(auto_traits))]
  33 #![feature(restricted_std)]
  34 #![feature(rustc_attrs)]
  35 #![feature(min_specialization)]
  36 #![recursion_limit = "256"]
  37
  38 #[unstable(feature = "proc_macro_internals", issue = "27812")]
  39 #[doc(hidden)]
  40 pub mod bridge;
  41
  42 mod diagnostic;
  43
  44 #[unstable(feature = "proc_macro_diagnostic", issue = "54140")]
  45 pub use diagnostic::{Diagnostic, Level, MultiSpan};
  46
  47 use std::cmp::Ordering;
  48 use std::ops::{Bound, RangeBounds};
  49 use std::path::PathBuf;
  50 use std::str::FromStr;
  51 use std::{error, fmt, iter, mem};
  52
  53 /// Determines whether proc_macro has been made accessible to the currently
  54 /// running program.
  55 ///
  56 /// The proc_macro crate is only intended for use inside the implementation of
  57 /// procedural macros. All the functions in this crate panic if invoked from
  58 /// outside of a procedural macro, such as from a build script or unit test or
  59 /// ordinary Rust binary.
  60 ///
  61 /// With consideration for Rust libraries that are designed to support both
  62 /// macro and non-macro use cases, `proc_macro::is_available()` provides a
  63 /// non-panicking way to detect whether the infrastructure required to use the
  64 /// API of proc_macro is presently available. Returns true if invoked from
  65 /// inside of a procedural macro, false if invoked from any other binary.
  66 #[unstable(feature = "proc_macro_is_available", issue = "71436")]
  67 pub fn is_available() -> bool {
  68     bridge::Bridge::is_available()
  69 }
  70
  71 /// The main type provided by this crate, representing an abstract stream of
  72 /// tokens, or, more specifically, a sequence of token trees.
  73 /// The type provide interfaces for iterating over those token trees and, conversely,
  74 /// collecting a number of token trees into one stream.
  75 ///
  76 /// This is both the input and output of `#[proc_macro]`, `#[proc_macro_attribute]`
  77 /// and `#[proc_macro_derive]` definitions.
  78 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
  79 #[derive(Clone)]
  80 pub struct TokenStream(bridge::client::TokenStream);
  81
  82 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
  83 impl !Send for TokenStream {}
  84 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
  85 impl !Sync for TokenStream {}
  86
  87 /// Error returned from `TokenStream::from_str`.
  88 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
  89 #[derive(Debug)]
  90 pub struct LexError {
  91     _inner: (),
  92 }
  93
  94 #[stable(feature = "proc_macro_lexerror_impls", since = "1.44.0")]
  95 impl fmt::Display for LexError {
  96     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  97         f.write_str("cannot parse string into token stream")
  98     }
  99 }
 100
 101 #[stable(feature = "proc_macro_lexerror_impls", since = "1.44.0")]
 102 impl error::Error for LexError {}
 103
 104 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 105 impl !Send for LexError {}
 106 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 107 impl !Sync for LexError {}
 108
 109 impl TokenStream {
 110     /// Returns an empty `TokenStream` containing no token trees.
 111     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 112     pub fn new() -> TokenStream {
 113         TokenStream(bridge::client::TokenStream::new())
 114     }
 115
 116     /// Checks if this `TokenStream` is empty.
 117     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 118     pub fn is_empty(&self) -> bool {
 119         self.0.is_empty()
 120     }
 121 }
 122
 123 /// Attempts to break the string into tokens and parse those tokens into a token stream.
 124 /// May fail for a number of reasons, for example, if the string contains unbalanced delimiters
 125 /// or characters not existing in the language.
 126 /// All tokens in the parsed stream get `Span::call_site()` spans.
 127 ///
 128 /// NOTE: some errors may cause panics instead of returning `LexError`. We reserve the right to
 129 /// change these errors into `LexError`s later.
 130 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 131 impl FromStr for TokenStream {
 132     type Err = LexError;
 133
 134     fn from_str(src: &str) -> Result<TokenStream, LexError> {
 135         Ok(TokenStream(bridge::client::TokenStream::from_str(src)))
 136     }
 137 }
 138
 139 // N.B., the bridge only provides `to_string`, implement `fmt::Display`
 140 // based on it (the reverse of the usual relationship between the two).
 141 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 142 impl ToString for TokenStream {
 143     fn to_string(&self) -> String {
 144         self.0.to_string()
 145     }
 146 }
 147
 148 /// Prints the token stream as a string that is supposed to be losslessly convertible back
 149 /// into the same token stream (modulo spans), except for possibly `TokenTree::Group`s
 150 /// with `Delimiter::None` delimiters and negative numeric literals.
 151 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 152 impl fmt::Display for TokenStream {
 153     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 154         f.write_str(&self.to_string())
 155     }
 156 }
 157
 158 /// Prints token in a form convenient for debugging.
 159 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 160 impl fmt::Debug for TokenStream {
 161     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 162         f.write_str("TokenStream ")?;
 163         f.debug_list().entries(self.clone()).finish()
 164     }
 165 }
 166
 167 #[stable(feature = "proc_macro_token_stream_default", since = "1.45.0")]
 168 impl Default for TokenStream {
 169     fn default() -> Self {
 170         TokenStream::new()
 171     }
 172 }
 173
 174 #[unstable(feature = "proc_macro_quote", issue = "54722")]
 175 pub use quote::{quote, quote_span};
 176
 177 /// Creates a token stream containing a single token tree.
 178 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 179 impl From<TokenTree> for TokenStream {
 180     fn from(tree: TokenTree) -> TokenStream {
 181         TokenStream(bridge::client::TokenStream::from_token_tree(match tree {
 182             TokenTree::Group(tt) => bridge::TokenTree::Group(tt.0),
 183             TokenTree::Punct(tt) => bridge::TokenTree::Punct(tt.0),
 184             TokenTree::Ident(tt) => bridge::TokenTree::Ident(tt.0),
 185             TokenTree::Literal(tt) => bridge::TokenTree::Literal(tt.0),
 186         }))
 187     }
 188 }
 189
 190 /// Collects a number of token trees into a single stream.
 191 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 192 impl iter::FromIterator<TokenTree> for TokenStream {
 193     fn from_iter<I: IntoIterator<Item = TokenTree>>(trees: I) -> Self {
 194         trees.into_iter().map(TokenStream::from).collect()
 195     }
 196 }
 197
 198 /// A "flattening" operation on token streams, collects token trees
 199 /// from multiple token streams into a single stream.
 200 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 201 impl iter::FromIterator<TokenStream> for TokenStream {
 202     fn from_iter<I: IntoIterator<Item = TokenStream>>(streams: I) -> Self {
 203         let mut builder = bridge::client::TokenStreamBuilder::new();
 204         streams.into_iter().for_each(|stream| builder.push(stream.0));
 205         TokenStream(builder.build())
 206     }
 207 }
 208
 209 #[stable(feature = "token_stream_extend", since = "1.30.0")]
 210 impl Extend<TokenTree> for TokenStream {
 211     fn extend<I: IntoIterator<Item = TokenTree>>(&mut self, trees: I) {
 212         self.extend(trees.into_iter().map(TokenStream::from));
 213     }
 214 }
 215
 216 #[stable(feature = "token_stream_extend", since = "1.30.0")]
 217 impl Extend<TokenStream> for TokenStream {
 218     fn extend<I: IntoIterator<Item = TokenStream>>(&mut self, streams: I) {
 219         // FIXME(eddyb) Use an optimized implementation if/when possible.
 220         *self = iter::once(mem::replace(self, Self::new())).chain(streams).collect();
 221     }
 222 }
 223
 224 /// Public implementation details for the `TokenStream` type, such as iterators.
 225 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 226 pub mod token_stream {
 227     use crate::{bridge, Group, Ident, Literal, Punct, TokenStream, TokenTree};
 228
 229     /// An iterator over `TokenStream`'s `TokenTree`s.
 230     /// The iteration is "shallow", e.g., the iterator doesn't recurse into delimited groups,
 231     /// and returns whole groups as token trees.
 232     #[derive(Clone)]
 233     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 234     pub struct IntoIter(bridge::client::TokenStreamIter);
 235
 236     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 237     impl Iterator for IntoIter {
 238         type Item = TokenTree;
 239
 240         fn next(&mut self) -> Option<TokenTree> {
 241             self.0.next().map(|tree| match tree {
 242                 bridge::TokenTree::Group(tt) => TokenTree::Group(Group(tt)),
 243                 bridge::TokenTree::Punct(tt) => TokenTree::Punct(Punct(tt)),
 244                 bridge::TokenTree::Ident(tt) => TokenTree::Ident(Ident(tt)),
 245                 bridge::TokenTree::Literal(tt) => TokenTree::Literal(Literal(tt)),
 246             })
 247         }
 248     }
 249
 250     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 251     impl IntoIterator for TokenStream {
 252         type Item = TokenTree;
 253         type IntoIter = IntoIter;
 254
 255         fn into_iter(self) -> IntoIter {
 256             IntoIter(self.0.into_iter())
 257         }
 258     }
 259 }
 260
 261 /// `quote!(..)` accepts arbitrary tokens and expands into a `TokenStream` describing the input.
 262 /// For example, `quote!(a + b)` will produce a expression, that, when evaluated, constructs
 263 /// the `TokenStream` `[Ident("a"), Punct('+', Alone), Ident("b")]`.
 264 ///
 265 /// Unquoting is done with `$`, and works by taking the single next ident as the unquoted term.
 266 /// To quote `$` itself, use `$$`.
 267 #[unstable(feature = "proc_macro_quote", issue = "54722")]
 268 #[allow_internal_unstable(proc_macro_def_site)]
 269 #[rustc_builtin_macro]
 270 pub macro quote($($t:tt)*) {
 271     /* compiler built-in */
 272 }
 273
 274 #[unstable(feature = "proc_macro_internals", issue = "27812")]
 275 #[doc(hidden)]
 276 mod quote;
 277
 278 /// A region of source code, along with macro expansion information.
 279 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 280 #[derive(Copy, Clone)]
 281 pub struct Span(bridge::client::Span);
 282
 283 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 284 impl !Send for Span {}
 285 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 286 impl !Sync for Span {}
 287
 288 macro_rules! diagnostic_method {
 289     ($name:ident, $level:expr) => {
 290         /// Creates a new `Diagnostic` with the given `message` at the span
 291         /// `self`.
 292         #[unstable(feature = "proc_macro_diagnostic", issue = "54140")]
 293         pub fn $name<T: Into<String>>(self, message: T) -> Diagnostic {
 294             Diagnostic::spanned(self, $level, message)
 295         }
 296     };
 297 }
 298
 299 impl Span {
 300     /// A span that resolves at the macro definition site.
 301     #[unstable(feature = "proc_macro_def_site", issue = "54724")]
 302     pub fn def_site() -> Span {
 303         Span(bridge::client::Span::def_site())
 304     }
 305
 306     /// The span of the invocation of the current procedural macro.
 307     /// Identifiers created with this span will be resolved as if they were written
 308     /// directly at the macro call location (call-site hygiene) and other code
 309     /// at the macro call site will be able to refer to them as well.
 310     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 311     pub fn call_site() -> Span {
 312         Span(bridge::client::Span::call_site())
 313     }
 314
 315     /// A span that represents `macro_rules` hygiene, and sometimes resolves at the macro
 316     /// definition site (local variables, labels, `$crate`) and sometimes at the macro
 317     /// call site (everything else).
 318     /// The span location is taken from the call-site.
 319     #[stable(feature = "proc_macro_mixed_site", since = "1.45.0")]
 320     pub fn mixed_site() -> Span {
 321         Span(bridge::client::Span::mixed_site())
 322     }
 323
 324     /// The original source file into which this span points.
 325     #[unstable(feature = "proc_macro_span", issue = "54725")]
 326     pub fn source_file(&self) -> SourceFile {
 327         SourceFile(self.0.source_file())
 328     }
 329
 330     /// The `Span` for the tokens in the previous macro expansion from which
 331     /// `self` was generated from, if any.
 332     #[unstable(feature = "proc_macro_span", issue = "54725")]
 333     pub fn parent(&self) -> Option<Span> {
 334         self.0.parent().map(Span)
 335     }
 336
 337     /// The span for the origin source code that `self` was generated from. If
 338     /// this `Span` wasn't generated from other macro expansions then the return
 339     /// value is the same as `*self`.
 340     #[unstable(feature = "proc_macro_span", issue = "54725")]
 341     pub fn source(&self) -> Span {
 342         Span(self.0.source())
 343     }
 344
 345     /// Gets the starting line/column in the source file for this span.
 346     #[unstable(feature = "proc_macro_span", issue = "54725")]
 347     pub fn start(&self) -> LineColumn {
 348         self.0.start()
 349     }
 350
 351     /// Gets the ending line/column in the source file for this span.
 352     #[unstable(feature = "proc_macro_span", issue = "54725")]
 353     pub fn end(&self) -> LineColumn {
 354         self.0.end()
 355     }
 356
 357     /// Creates a new span encompassing `self` and `other`.
 358     ///
 359     /// Returns `None` if `self` and `other` are from different files.
 360     #[unstable(feature = "proc_macro_span", issue = "54725")]
 361     pub fn join(&self, other: Span) -> Option<Span> {
 362         self.0.join(other.0).map(Span)
 363     }
 364
 365     /// Creates a new span with the same line/column information as `self` but
 366     /// that resolves symbols as though it were at `other`.
 367     #[stable(feature = "proc_macro_span_resolved_at", since = "1.45.0")]
 368     pub fn resolved_at(&self, other: Span) -> Span {
 369         Span(self.0.resolved_at(other.0))
 370     }
 371
 372     /// Creates a new span with the same name resolution behavior as `self` but
 373     /// with the line/column information of `other`.
 374     #[stable(feature = "proc_macro_span_located_at", since = "1.45.0")]
 375     pub fn located_at(&self, other: Span) -> Span {
 376         other.resolved_at(*self)
 377     }
 378
 379     /// Compares to spans to see if they're equal.
 380     #[unstable(feature = "proc_macro_span", issue = "54725")]
 381     pub fn eq(&self, other: &Span) -> bool {
 382         self.0 == other.0
 383     }
 384
 385     /// Returns the source text behind a span. This preserves the original source
 386     /// code, including spaces and comments. It only returns a result if the span
 387     /// corresponds to real source code.
 388     ///
 389     /// Note: The observable result of a macro should only rely on the tokens and
 390     /// not on this source text. The result of this function is a best effort to
 391     /// be used for diagnostics only.
 392     #[unstable(feature = "proc_macro_span", issue = "54725")]
 393     pub fn source_text(&self) -> Option<String> {
 394         self.0.source_text()
 395     }
 396
 397     diagnostic_method!(error, Level::Error);
 398     diagnostic_method!(warning, Level::Warning);
 399     diagnostic_method!(note, Level::Note);
 400     diagnostic_method!(help, Level::Help);
 401 }
 402
 403 /// Prints a span in a form convenient for debugging.
 404 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 405 impl fmt::Debug for Span {
 406     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 407         self.0.fmt(f)
 408     }
 409 }
 410
 411 /// A line-column pair representing the start or end of a `Span`.
 412 #[unstable(feature = "proc_macro_span", issue = "54725")]
 413 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 414 pub struct LineColumn {
 415     /// The 1-indexed line in the source file on which the span starts or ends (inclusive).
 416     #[unstable(feature = "proc_macro_span", issue = "54725")]
 417     pub line: usize,
 418     /// The 0-indexed column (in UTF-8 characters) in the source file on which
 419     /// the span starts or ends (inclusive).
 420     #[unstable(feature = "proc_macro_span", issue = "54725")]
 421     pub column: usize,
 422 }
 423
 424 #[unstable(feature = "proc_macro_span", issue = "54725")]
 425 impl !Send for LineColumn {}
 426 #[unstable(feature = "proc_macro_span", issue = "54725")]
 427 impl !Sync for LineColumn {}
 428
 429 #[unstable(feature = "proc_macro_span", issue = "54725")]
 430 impl Ord for LineColumn {
 431     fn cmp(&self, other: &Self) -> Ordering {
 432         self.line.cmp(&other.line).then(self.column.cmp(&other.column))
 433     }
 434 }
 435
 436 #[unstable(feature = "proc_macro_span", issue = "54725")]
 437 impl PartialOrd for LineColumn {
 438     fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
 439         Some(self.cmp(other))
 440     }
 441 }
 442
 443 /// The source file of a given `Span`.
 444 #[unstable(feature = "proc_macro_span", issue = "54725")]
 445 #[derive(Clone)]
 446 pub struct SourceFile(bridge::client::SourceFile);
 447
 448 impl SourceFile {
 449     /// Gets the path to this source file.
 450     ///
 451     /// ### Note
 452     /// If the code span associated with this `SourceFile` was generated by an external macro, this
 453     /// macro, this may not be an actual path on the filesystem. Use [`is_real`] to check.
 454     ///
 455     /// Also note that even if `is_real` returns `true`, if `--remap-path-prefix` was passed on
 456     /// the command line, the path as given may not actually be valid.
 457     ///
 458     /// [`is_real`]: Self::is_real
 459     #[unstable(feature = "proc_macro_span", issue = "54725")]
 460     pub fn path(&self) -> PathBuf {
 461         PathBuf::from(self.0.path())
 462     }
 463
 464     /// Returns `true` if this source file is a real source file, and not generated by an external
 465     /// macro's expansion.
 466     #[unstable(feature = "proc_macro_span", issue = "54725")]
 467     pub fn is_real(&self) -> bool {
 468         // This is a hack until intercrate spans are implemented and we can have real source files
 469         // for spans generated in external macros.
 470         // https://github.com/rust-lang/rust/pull/43604#issuecomment-333334368
 471         self.0.is_real()
 472     }
 473 }
 474
 475 #[unstable(feature = "proc_macro_span", issue = "54725")]
 476 impl fmt::Debug for SourceFile {
 477     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 478         f.debug_struct("SourceFile")
 479             .field("path", &self.path())
 480             .field("is_real", &self.is_real())
 481             .finish()
 482     }
 483 }
 484
 485 #[unstable(feature = "proc_macro_span", issue = "54725")]
 486 impl PartialEq for SourceFile {
 487     fn eq(&self, other: &Self) -> bool {
 488         self.0.eq(&other.0)
 489     }
 490 }
 491
 492 #[unstable(feature = "proc_macro_span", issue = "54725")]
 493 impl Eq for SourceFile {}
 494
 495 /// A single token or a delimited sequence of token trees (e.g., `[1, (), ..]`).
 496 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 497 #[derive(Clone)]
 498 pub enum TokenTree {
 499     /// A token stream surrounded by bracket delimiters.
 500     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 501     Group(#[stable(feature = "proc_macro_lib2", since = "1.29.0")] Group),
 502     /// An identifier.
 503     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 504     Ident(#[stable(feature = "proc_macro_lib2", since = "1.29.0")] Ident),
 505     /// A single punctuation character (`+`, `,`, `$`, etc.).
 506     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 507     Punct(#[stable(feature = "proc_macro_lib2", since = "1.29.0")] Punct),
 508     /// A literal character (`'a'`), string (`"hello"`), number (`2.3`), etc.
 509     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 510     Literal(#[stable(feature = "proc_macro_lib2", since = "1.29.0")] Literal),
 511 }
 512
 513 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 514 impl !Send for TokenTree {}
 515 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 516 impl !Sync for TokenTree {}
 517
 518 impl TokenTree {
 519     /// Returns the span of this tree, delegating to the `span` method of
 520     /// the contained token or a delimited stream.
 521     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 522     pub fn span(&self) -> Span {
 523         match *self {
 524             TokenTree::Group(ref t) => t.span(),
 525             TokenTree::Ident(ref t) => t.span(),
 526             TokenTree::Punct(ref t) => t.span(),
 527             TokenTree::Literal(ref t) => t.span(),
 528         }
 529     }
 530
 531     /// Configures the span for *only this token*.
 532     ///
 533     /// Note that if this token is a `Group` then this method will not configure
 534     /// the span of each of the internal tokens, this will simply delegate to
 535     /// the `set_span` method of each variant.
 536     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 537     pub fn set_span(&mut self, span: Span) {
 538         match *self {
 539             TokenTree::Group(ref mut t) => t.set_span(span),
 540             TokenTree::Ident(ref mut t) => t.set_span(span),
 541             TokenTree::Punct(ref mut t) => t.set_span(span),
 542             TokenTree::Literal(ref mut t) => t.set_span(span),
 543         }
 544     }
 545 }
 546
 547 /// Prints token tree in a form convenient for debugging.
 548 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 549 impl fmt::Debug for TokenTree {
 550     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 551         // Each of these has the name in the struct type in the derived debug,
 552         // so don't bother with an extra layer of indirection
 553         match *self {
 554             TokenTree::Group(ref tt) => tt.fmt(f),
 555             TokenTree::Ident(ref tt) => tt.fmt(f),
 556             TokenTree::Punct(ref tt) => tt.fmt(f),
 557             TokenTree::Literal(ref tt) => tt.fmt(f),
 558         }
 559     }
 560 }
 561
 562 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 563 impl From<Group> for TokenTree {
 564     fn from(g: Group) -> TokenTree {
 565         TokenTree::Group(g)
 566     }
 567 }
 568
 569 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 570 impl From<Ident> for TokenTree {
 571     fn from(g: Ident) -> TokenTree {
 572         TokenTree::Ident(g)
 573     }
 574 }
 575
 576 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 577 impl From<Punct> for TokenTree {
 578     fn from(g: Punct) -> TokenTree {
 579         TokenTree::Punct(g)
 580     }
 581 }
 582
 583 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 584 impl From<Literal> for TokenTree {
 585     fn from(g: Literal) -> TokenTree {
 586         TokenTree::Literal(g)
 587     }
 588 }
 589
 590 // N.B., the bridge only provides `to_string`, implement `fmt::Display`
 591 // based on it (the reverse of the usual relationship between the two).
 592 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 593 impl ToString for TokenTree {
 594     fn to_string(&self) -> String {
 595         match *self {
 596             TokenTree::Group(ref t) => t.to_string(),
 597             TokenTree::Ident(ref t) => t.to_string(),
 598             TokenTree::Punct(ref t) => t.to_string(),
 599             TokenTree::Literal(ref t) => t.to_string(),
 600         }
 601     }
 602 }
 603
 604 /// Prints the token tree as a string that is supposed to be losslessly convertible back
 605 /// into the same token tree (modulo spans), except for possibly `TokenTree::Group`s
 606 /// with `Delimiter::None` delimiters and negative numeric literals.
 607 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 608 impl fmt::Display for TokenTree {
 609     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 610         f.write_str(&self.to_string())
 611     }
 612 }
 613
 614 /// A delimited token stream.
 615 ///
 616 /// A `Group` internally contains a `TokenStream` which is surrounded by `Delimiter`s.
 617 #[derive(Clone)]
 618 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 619 pub struct Group(bridge::client::Group);
 620
 621 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 622 impl !Send for Group {}
 623 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 624 impl !Sync for Group {}
 625
 626 /// Describes how a sequence of token trees is delimited.
 627 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 628 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 629 pub enum Delimiter {
 630     /// `( ... )`
 631     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 632     Parenthesis,
 633     /// `{ ... }`
 634     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 635     Brace,
 636     /// `[ ... ]`
 637     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 638     Bracket,
 639     /// `Ø ... Ø`
 640     /// An implicit delimiter, that may, for example, appear around tokens coming from a
 641     /// "macro variable" `$var`. It is important to preserve operator priorities in cases like
 642     /// `$var * 3` where `$var` is `1 + 2`.
 643     /// Implicit delimiters may not survive roundtrip of a token stream through a string.
 644     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 645     None,
 646 }
 647
 648 impl Group {
 649     /// Creates a new `Group` with the given delimiter and token stream.
 650     ///
 651     /// This constructor will set the span for this group to
 652     /// `Span::call_site()`. To change the span you can use the `set_span`
 653     /// method below.
 654     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 655     pub fn new(delimiter: Delimiter, stream: TokenStream) -> Group {
 656         Group(bridge::client::Group::new(delimiter, stream.0))
 657     }
 658
 659     /// Returns the delimiter of this `Group`
 660     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 661     pub fn delimiter(&self) -> Delimiter {
 662         self.0.delimiter()
 663     }
 664
 665     /// Returns the `TokenStream` of tokens that are delimited in this `Group`.
 666     ///
 667     /// Note that the returned token stream does not include the delimiter
 668     /// returned above.
 669     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 670     pub fn stream(&self) -> TokenStream {
 671         TokenStream(self.0.stream())
 672     }
 673
 674     /// Returns the span for the delimiters of this token stream, spanning the
 675     /// entire `Group`.
 676     ///
 677     /// ```text
 678     /// pub fn span(&self) -> Span {
 679     ///            ^^^^^^^
 680     /// ```
 681     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 682     pub fn span(&self) -> Span {
 683         Span(self.0.span())
 684     }
 685
 686     /// Returns the span pointing to the opening delimiter of this group.
 687     ///
 688     /// ```text
 689     /// pub fn span_open(&self) -> Span {
 690     ///                 ^
 691     /// ```
 692     #[unstable(feature = "proc_macro_span", issue = "54725")]
 693     pub fn span_open(&self) -> Span {
 694         Span(self.0.span_open())
 695     }
 696
 697     /// Returns the span pointing to the closing delimiter of this group.
 698     ///
 699     /// ```text
 700     /// pub fn span_close(&self) -> Span {
 701     ///                        ^
 702     /// ```
 703     #[unstable(feature = "proc_macro_span", issue = "54725")]
 704     pub fn span_close(&self) -> Span {
 705         Span(self.0.span_close())
 706     }
 707
 708     /// Configures the span for this `Group`'s delimiters, but not its internal
 709     /// tokens.
 710     ///
 711     /// This method will **not** set the span of all the internal tokens spanned
 712     /// by this group, but rather it will only set the span of the delimiter
 713     /// tokens at the level of the `Group`.
 714     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 715     pub fn set_span(&mut self, span: Span) {
 716         self.0.set_span(span.0);
 717     }
 718 }
 719
 720 // N.B., the bridge only provides `to_string`, implement `fmt::Display`
 721 // based on it (the reverse of the usual relationship between the two).
 722 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 723 impl ToString for Group {
 724     fn to_string(&self) -> String {
 725         TokenStream::from(TokenTree::from(self.clone())).to_string()
 726     }
 727 }
 728
 729 /// Prints the group as a string that should be losslessly convertible back
 730 /// into the same group (modulo spans), except for possibly `TokenTree::Group`s
 731 /// with `Delimiter::None` delimiters.
 732 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 733 impl fmt::Display for Group {
 734     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 735         f.write_str(&self.to_string())
 736     }
 737 }
 738
 739 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 740 impl fmt::Debug for Group {
 741     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 742         f.debug_struct("Group")
 743             .field("delimiter", &self.delimiter())
 744             .field("stream", &self.stream())
 745             .field("span", &self.span())
 746             .finish()
 747     }
 748 }
 749
 750 /// An `Punct` is an single punctuation character like `+`, `-` or `#`.
 751 ///
 752 /// Multi-character operators like `+=` are represented as two instances of `Punct` with different
 753 /// forms of `Spacing` returned.
 754 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 755 #[derive(Clone)]
 756 pub struct Punct(bridge::client::Punct);
 757
 758 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 759 impl !Send for Punct {}
 760 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 761 impl !Sync for Punct {}
 762
 763 /// Whether an `Punct` is followed immediately by another `Punct` or
 764 /// followed by another token or whitespace.
 765 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 766 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 767 pub enum Spacing {
 768     /// e.g., `+` is `Alone` in `+ =`, `+ident` or `+()`.
 769     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 770     Alone,
 771     /// e.g., `+` is `Joint` in `+=` or `'#`.
 772     /// Additionally, single quote `'` can join with identifiers to form lifetimes `'ident`.
 773     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 774     Joint,
 775 }
 776
 777 impl Punct {
 778     /// Creates a new `Punct` from the given character and spacing.
 779     /// The `ch` argument must be a valid punctuation character permitted by the language,
 780     /// otherwise the function will panic.
 781     ///
 782     /// The returned `Punct` will have the default span of `Span::call_site()`
 783     /// which can be further configured with the `set_span` method below.
 784     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 785     pub fn new(ch: char, spacing: Spacing) -> Punct {
 786         Punct(bridge::client::Punct::new(ch, spacing))
 787     }
 788
 789     /// Returns the value of this punctuation character as `char`.
 790     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 791     pub fn as_char(&self) -> char {
 792         self.0.as_char()
 793     }
 794
 795     /// Returns the spacing of this punctuation character, indicating whether it's immediately
 796     /// followed by another `Punct` in the token stream, so they can potentially be combined into
 797     /// a multi-character operator (`Joint`), or it's followed by some other token or whitespace
 798     /// (`Alone`) so the operator has certainly ended.
 799     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 800     pub fn spacing(&self) -> Spacing {
 801         self.0.spacing()
 802     }
 803
 804     /// Returns the span for this punctuation character.
 805     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 806     pub fn span(&self) -> Span {
 807         Span(self.0.span())
 808     }
 809
 810     /// Configure the span for this punctuation character.
 811     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 812     pub fn set_span(&mut self, span: Span) {
 813         self.0 = self.0.with_span(span.0);
 814     }
 815 }
 816
 817 // N.B., the bridge only provides `to_string`, implement `fmt::Display`
 818 // based on it (the reverse of the usual relationship between the two).
 819 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 820 impl ToString for Punct {
 821     fn to_string(&self) -> String {
 822         TokenStream::from(TokenTree::from(self.clone())).to_string()
 823     }
 824 }
 825
 826 /// Prints the punctuation character as a string that should be losslessly convertible
 827 /// back into the same character.
 828 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 829 impl fmt::Display for Punct {
 830     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 831         f.write_str(&self.to_string())
 832     }
 833 }
 834
 835 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 836 impl fmt::Debug for Punct {
 837     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 838         f.debug_struct("Punct")
 839             .field("ch", &self.as_char())
 840             .field("spacing", &self.spacing())
 841             .field("span", &self.span())
 842             .finish()
 843     }
 844 }
 845
 846 #[stable(feature = "proc_macro_punct_eq", since = "1.49.0")]
 847 impl PartialEq<char> for Punct {
 848     fn eq(&self, rhs: &char) -> bool {
 849         self.as_char() == *rhs
 850     }
 851 }
 852
 853 /// An identifier (`ident`).
 854 #[derive(Clone)]
 855 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 856 pub struct Ident(bridge::client::Ident);
 857
 858 impl Ident {
 859     /// Creates a new `Ident` with the given `string` as well as the specified
 860     /// `span`.
 861     /// The `string` argument must be a valid identifier permitted by the
 862     /// language (including keywords, e.g. `self` or `fn`). Otherwise, the function will panic.
 863     ///
 864     /// Note that `span`, currently in rustc, configures the hygiene information
 865     /// for this identifier.
 866     ///
 867     /// As of this time `Span::call_site()` explicitly opts-in to "call-site" hygiene
 868     /// meaning that identifiers created with this span will be resolved as if they were written
 869     /// directly at the location of the macro call, and other code at the macro call site will be
 870     /// able to refer to them as well.
 871     ///
 872     /// Later spans like `Span::def_site()` will allow to opt-in to "definition-site" hygiene
 873     /// meaning that identifiers created with this span will be resolved at the location of the
 874     /// macro definition and other code at the macro call site will not be able to refer to them.
 875     ///
 876     /// Due to the current importance of hygiene this constructor, unlike other
 877     /// tokens, requires a `Span` to be specified at construction.
 878     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 879     pub fn new(string: &str, span: Span) -> Ident {
 880         Ident(bridge::client::Ident::new(string, span.0, false))
 881     }
 882
 883     /// Same as `Ident::new`, but creates a raw identifier (`r#ident`).
 884     /// The `string` argument be a valid identifier permitted by the language
 885     /// (including keywords, e.g. `fn`). Keywords which are usable in path segments
 886     /// (e.g. `self`, `super`) are not supported, and will cause a panic.
 887     #[stable(feature = "proc_macro_raw_ident", since = "1.47.0")]
 888     pub fn new_raw(string: &str, span: Span) -> Ident {
 889         Ident(bridge::client::Ident::new(string, span.0, true))
 890     }
 891
 892     /// Returns the span of this `Ident`, encompassing the entire string returned
 893     /// by [`to_string`](Self::to_string).
 894     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 895     pub fn span(&self) -> Span {
 896         Span(self.0.span())
 897     }
 898
 899     /// Configures the span of this `Ident`, possibly changing its hygiene context.
 900     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 901     pub fn set_span(&mut self, span: Span) {
 902         self.0 = self.0.with_span(span.0);
 903     }
 904 }
 905
 906 // N.B., the bridge only provides `to_string`, implement `fmt::Display`
 907 // based on it (the reverse of the usual relationship between the two).
 908 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 909 impl ToString for Ident {
 910     fn to_string(&self) -> String {
 911         TokenStream::from(TokenTree::from(self.clone())).to_string()
 912     }
 913 }
 914
 915 /// Prints the identifier as a string that should be losslessly convertible
 916 /// back into the same identifier.
 917 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 918 impl fmt::Display for Ident {
 919     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 920         f.write_str(&self.to_string())
 921     }
 922 }
 923
 924 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 925 impl fmt::Debug for Ident {
 926     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 927         f.debug_struct("Ident")
 928             .field("ident", &self.to_string())
 929             .field("span", &self.span())
 930             .finish()
 931     }
 932 }
 933
 934 /// A literal string (`"hello"`), byte string (`b"hello"`),
 935 /// character (`'a'`), byte character (`b'a'`), an integer or floating point number
 936 /// with or without a suffix (`1`, `1u8`, `2.3`, `2.3f32`).
 937 /// Boolean literals like `true` and `false` do not belong here, they are `Ident`s.
 938 #[derive(Clone)]
 939 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 940 pub struct Literal(bridge::client::Literal);
 941
 942 macro_rules! suffixed_int_literals {
 943     ($($name:ident => $kind:ident,)*) => ($(
 944         /// Creates a new suffixed integer literal with the specified value.
 945         ///
 946         /// This function will create an integer like `1u32` where the integer
 947         /// value specified is the first part of the token and the integral is
 948         /// also suffixed at the end.
 949         /// Literals created from negative numbers may not survive round-trips through
 950         /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
 951         ///
 952         /// Literals created through this method have the `Span::call_site()`
 953         /// span by default, which can be configured with the `set_span` method
 954         /// below.
 955         #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 956         pub fn $name(n: $kind) -> Literal {
 957             Literal(bridge::client::Literal::typed_integer(&n.to_string(), stringify!($kind)))
 958         }
 959     )*)
 960 }
 961
 962 macro_rules! unsuffixed_int_literals {
 963     ($($name:ident => $kind:ident,)*) => ($(
 964         /// Creates a new unsuffixed integer literal with the specified value.
 965         ///
 966         /// This function will create an integer like `1` where the integer
 967         /// value specified is the first part of the token. No suffix is
 968         /// specified on this token, meaning that invocations like
 969         /// `Literal::i8_unsuffixed(1)` are equivalent to
 970         /// `Literal::u32_unsuffixed(1)`.
 971         /// Literals created from negative numbers may not survive rountrips through
 972         /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
 973         ///
 974         /// Literals created through this method have the `Span::call_site()`
 975         /// span by default, which can be configured with the `set_span` method
 976         /// below.
 977         #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 978         pub fn $name(n: $kind) -> Literal {
 979             Literal(bridge::client::Literal::integer(&n.to_string()))
 980         }
 981     )*)
 982 }
 983
 984 impl Literal {
 985     suffixed_int_literals! {
 986         u8_suffixed => u8,
 987         u16_suffixed => u16,
 988         u32_suffixed => u32,
 989         u64_suffixed => u64,
 990         u128_suffixed => u128,
 991         usize_suffixed => usize,
 992         i8_suffixed => i8,
 993         i16_suffixed => i16,
 994         i32_suffixed => i32,
 995         i64_suffixed => i64,
 996         i128_suffixed => i128,
 997         isize_suffixed => isize,
 998     }
 999
1000     unsuffixed_int_literals! {
1001         u8_unsuffixed => u8,
1002         u16_unsuffixed => u16,
1003         u32_unsuffixed => u32,
1004         u64_unsuffixed => u64,
1005         u128_unsuffixed => u128,
1006         usize_unsuffixed => usize,
1007         i8_unsuffixed => i8,
1008         i16_unsuffixed => i16,
1009         i32_unsuffixed => i32,
1010         i64_unsuffixed => i64,
1011         i128_unsuffixed => i128,
1012         isize_unsuffixed => isize,
1013     }
1014
1015     /// Creates a new unsuffixed floating-point literal.
1016     ///
1017     /// This constructor is similar to those like `Literal::i8_unsuffixed` where
1018     /// the float's value is emitted directly into the token but no suffix is
1019     /// used, so it may be inferred to be a `f64` later in the compiler.
1020     /// Literals created from negative numbers may not survive rountrips through
1021     /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
1022     ///
1023     /// # Panics
1024     ///
1025     /// This function requires that the specified float is finite, for
1026     /// example if it is infinity or NaN this function will panic.
1027     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
1028     pub fn f32_unsuffixed(n: f32) -> Literal {
1029         if !n.is_finite() {
1030             panic!("Invalid float literal {}", n);
1031         }
1032         Literal(bridge::client::Literal::float(&n.to_string()))
1033     }
1034
1035     /// Creates a new suffixed floating-point literal.
1036     ///
1037     /// This constructor will create a literal like `1.0f32` where the value
1038     /// specified is the preceding part of the token and `f32` is the suffix of
1039     /// the token. This token will always be inferred to be an `f32` in the
1040     /// compiler.
1041     /// Literals created from negative numbers may not survive rountrips through
1042     /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
1043     ///
1044     /// # Panics
1045     ///
1046     /// This function requires that the specified float is finite, for
1047     /// example if it is infinity or NaN this function will panic.
1048     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
1049     pub fn f32_suffixed(n: f32) -> Literal {
1050         if !n.is_finite() {
1051             panic!("Invalid float literal {}", n);
1052         }
1053         Literal(bridge::client::Literal::f32(&n.to_string()))
1054     }
1055
1056     /// Creates a new unsuffixed floating-point literal.
1057     ///
1058     /// This constructor is similar to those like `Literal::i8_unsuffixed` where
1059     /// the float's value is emitted directly into the token but no suffix is
1060     /// used, so it may be inferred to be a `f64` later in the compiler.
1061     /// Literals created from negative numbers may not survive rountrips through
1062     /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
1063     ///
1064     /// # Panics
1065     ///
1066     /// This function requires that the specified float is finite, for
1067     /// example if it is infinity or NaN this function will panic.
1068     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
1069     pub fn f64_unsuffixed(n: f64) -> Literal {
1070         if !n.is_finite() {
1071             panic!("Invalid float literal {}", n);
1072         }
1073         Literal(bridge::client::Literal::float(&n.to_string()))
1074     }
1075
1076     /// Creates a new suffixed floating-point literal.
1077     ///
1078     /// This constructor will create a literal like `1.0f64` where the value
1079     /// specified is the preceding part of the token and `f64` is the suffix of
1080     /// the token. This token will always be inferred to be an `f64` in the
1081     /// compiler.
1082     /// Literals created from negative numbers may not survive rountrips through
1083     /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
1084     ///
1085     /// # Panics
1086     ///
1087     /// This function requires that the specified float is finite, for
1088     /// example if it is infinity or NaN this function will panic.
1089     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
1090     pub fn f64_suffixed(n: f64) -> Literal {
1091         if !n.is_finite() {
1092             panic!("Invalid float literal {}", n);
1093         }
1094         Literal(bridge::client::Literal::f64(&n.to_string()))
1095     }
1096
1097     /// String literal.
1098     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
1099     pub fn string(string: &str) -> Literal {
1100         Literal(bridge::client::Literal::string(string))
1101     }
1102
1103     /// Character literal.
1104     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
1105     pub fn character(ch: char) -> Literal {
1106         Literal(bridge::client::Literal::character(ch))
1107     }
1108
1109     /// Byte string literal.
1110     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
1111     pub fn byte_string(bytes: &[u8]) -> Literal {
1112         Literal(bridge::client::Literal::byte_string(bytes))
1113     }
1114
1115     /// Returns the span encompassing this literal.
1116     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
1117     pub fn span(&self) -> Span {
1118         Span(self.0.span())
1119     }
1120
1121     /// Configures the span associated for this literal.
1122     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
1123     pub fn set_span(&mut self, span: Span) {
1124         self.0.set_span(span.0);
1125     }
1126
1127     /// Returns a `Span` that is a subset of `self.span()` containing only the
1128     /// source bytes in range `range`. Returns `None` if the would-be trimmed
1129     /// span is outside the bounds of `self`.
1130     // FIXME(SergioBenitez): check that the byte range starts and ends at a
1131     // UTF-8 boundary of the source. otherwise, it's likely that a panic will
1132     // occur elsewhere when the source text is printed.
1133     // FIXME(SergioBenitez): there is no way for the user to know what
1134     // `self.span()` actually maps to, so this method can currently only be
1135     // called blindly. For example, `to_string()` for the character 'c' returns
1136     // "'\u{63}'"; there is no way for the user to know whether the source text
1137     // was 'c' or whether it was '\u{63}'.
1138     #[unstable(feature = "proc_macro_span", issue = "54725")]
1139     pub fn subspan<R: RangeBounds<usize>>(&self, range: R) -> Option<Span> {
1140         // HACK(eddyb) something akin to `Option::cloned`, but for `Bound<&T>`.
1141         fn cloned_bound<T: Clone>(bound: Bound<&T>) -> Bound<T> {
1142             match bound {
1143                 Bound::Included(x) => Bound::Included(x.clone()),
1144                 Bound::Excluded(x) => Bound::Excluded(x.clone()),
1145                 Bound::Unbounded => Bound::Unbounded,
1146             }
1147         }
1148
1149         self.0.subspan(cloned_bound(range.start_bound()), cloned_bound(range.end_bound())).map(Span)
1150     }
1151 }
1152
1153 // N.B., the bridge only provides `to_string`, implement `fmt::Display`
1154 // based on it (the reverse of the usual relationship between the two).
1155 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
1156 impl ToString for Literal {
1157     fn to_string(&self) -> String {
1158         TokenStream::from(TokenTree::from(self.clone())).to_string()
1159     }
1160 }
1161
1162 /// Prints the literal as a string that should be losslessly convertible
1163 /// back into the same literal (except for possible rounding for floating point literals).
1164 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
1165 impl fmt::Display for Literal {
1166     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1167         f.write_str(&self.to_string())
1168     }
1169 }
1170
1171 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
1172 impl fmt::Debug for Literal {
1173     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1174         self.0.fmt(f)
1175     }
1176 }
1177
1178 /// Tracked access to environment variables.
1179 #[unstable(feature = "proc_macro_tracked_env", issue = "74690")]
1180 pub mod tracked_env {
1181     use std::env::{self, VarError};
1182     use std::ffi::OsStr;
1183
1184     /// Retrieve an environment variable and add it to build dependency info.
1185     /// Build system executing the compiler will know that the variable was accessed during
1186     /// compilation, and will be able to rerun the build when the value of that variable changes.
1187     /// Besides the dependency tracking this function should be equivalent to `env::var` from the
1188     /// standard library, except that the argument must be UTF-8.
1189     #[unstable(feature = "proc_macro_tracked_env", issue = "74690")]
1190     pub fn var<K: AsRef<OsStr> + AsRef<str>>(key: K) -> Result<String, VarError> {
1191         let key: &str = key.as_ref();
1192         let value = env::var(key);
1193         crate::bridge::client::FreeFunctions::track_env_var(key, value.as_deref().ok());
1194         value
1195     }
1196 }