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 #![feature(auto_traits)]
  32 #![feature(restricted_std)]
  33 #![feature(rustc_attrs)]
  34 #![feature(min_specialization)]
  35 #![recursion_limit = "256"]
  36
  37 #[unstable(feature = "proc_macro_internals", issue = "27812")]
  38 #[doc(hidden)]
  39 pub mod bridge;
  40
  41 mod diagnostic;
  42
  43 #[unstable(feature = "proc_macro_diagnostic", issue = "54140")]
  44 pub use diagnostic::{Diagnostic, Level, MultiSpan};
  45
  46 use std::cmp::Ordering;
  47 use std::ops::{Bound, RangeBounds};
  48 use std::path::PathBuf;
  49 use std::str::FromStr;
  50 use std::{error, fmt, iter, mem};
  51
  52 /// Determines whether proc_macro has been made accessible to the currently
  53 /// running program.
  54 ///
  55 /// The proc_macro crate is only intended for use inside the implementation of
  56 /// procedural macros. All the functions in this crate panic if invoked from
  57 /// outside of a procedural macro, such as from a build script or unit test or
  58 /// ordinary Rust binary.
  59 ///
  60 /// With consideration for Rust libraries that are designed to support both
  61 /// macro and non-macro use cases, `proc_macro::is_available()` provides a
  62 /// non-panicking way to detect whether the infrastructure required to use the
  63 /// API of proc_macro is presently available. Returns true if invoked from
  64 /// inside of a procedural macro, false if invoked from any other binary.
  65 #[unstable(feature = "proc_macro_is_available", issue = "71436")]
  66 pub fn is_available() -> bool {
  67     bridge::Bridge::is_available()
  68 }
  69
  70 /// The main type provided by this crate, representing an abstract stream of
  71 /// tokens, or, more specifically, a sequence of token trees.
  72 /// The type provide interfaces for iterating over those token trees and, conversely,
  73 /// collecting a number of token trees into one stream.
  74 ///
  75 /// This is both the input and output of `#[proc_macro]`, `#[proc_macro_attribute]`
  76 /// and `#[proc_macro_derive]` definitions.
  77 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
  78 #[derive(Clone)]
  79 pub struct TokenStream(bridge::client::TokenStream);
  80
  81 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
  82 impl !Send for TokenStream {}
  83 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
  84 impl !Sync for TokenStream {}
  85
  86 /// Error returned from `TokenStream::from_str`.
  87 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
  88 #[derive(Debug)]
  89 pub struct LexError {
  90     _inner: (),
  91 }
  92
  93 #[stable(feature = "proc_macro_lexerror_impls", since = "1.44.0")]
  94 impl fmt::Display for LexError {
  95     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  96         f.write_str("cannot parse string into token stream")
  97     }
  98 }
  99
 100 #[stable(feature = "proc_macro_lexerror_impls", since = "1.44.0")]
 101 impl error::Error for LexError {}
 102
 103 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 104 impl !Send for LexError {}
 105 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 106 impl !Sync for LexError {}
 107
 108 impl TokenStream {
 109     /// Returns an empty `TokenStream` containing no token trees.
 110     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 111     pub fn new() -> TokenStream {
 112         TokenStream(bridge::client::TokenStream::new())
 113     }
 114
 115     /// Checks if this `TokenStream` is empty.
 116     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 117     pub fn is_empty(&self) -> bool {
 118         self.0.is_empty()
 119     }
 120 }
 121
 122 /// Attempts to break the string into tokens and parse those tokens into a token stream.
 123 /// May fail for a number of reasons, for example, if the string contains unbalanced delimiters
 124 /// or characters not existing in the language.
 125 /// All tokens in the parsed stream get `Span::call_site()` spans.
 126 ///
 127 /// NOTE: some errors may cause panics instead of returning `LexError`. We reserve the right to
 128 /// change these errors into `LexError`s later.
 129 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 130 impl FromStr for TokenStream {
 131     type Err = LexError;
 132
 133     fn from_str(src: &str) -> Result<TokenStream, LexError> {
 134         Ok(TokenStream(bridge::client::TokenStream::from_str(src)))
 135     }
 136 }
 137
 138 // N.B., the bridge only provides `to_string`, implement `fmt::Display`
 139 // based on it (the reverse of the usual relationship between the two).
 140 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 141 impl ToString for TokenStream {
 142     fn to_string(&self) -> String {
 143         self.0.to_string()
 144     }
 145 }
 146
 147 /// Prints the token stream as a string that is supposed to be losslessly convertible back
 148 /// into the same token stream (modulo spans), except for possibly `TokenTree::Group`s
 149 /// with `Delimiter::None` delimiters and negative numeric literals.
 150 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 151 impl fmt::Display for TokenStream {
 152     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 153         f.write_str(&self.to_string())
 154     }
 155 }
 156
 157 /// Prints token in a form convenient for debugging.
 158 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 159 impl fmt::Debug for TokenStream {
 160     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 161         f.write_str("TokenStream ")?;
 162         f.debug_list().entries(self.clone()).finish()
 163     }
 164 }
 165
 166 #[stable(feature = "proc_macro_token_stream_default", since = "1.45.0")]
 167 impl Default for TokenStream {
 168     fn default() -> Self {
 169         TokenStream::new()
 170     }
 171 }
 172
 173 #[unstable(feature = "proc_macro_quote", issue = "54722")]
 174 pub use quote::{quote, quote_span};
 175
 176 /// Creates a token stream containing a single token tree.
 177 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 178 impl From<TokenTree> for TokenStream {
 179     fn from(tree: TokenTree) -> TokenStream {
 180         TokenStream(bridge::client::TokenStream::from_token_tree(match tree {
 181             TokenTree::Group(tt) => bridge::TokenTree::Group(tt.0),
 182             TokenTree::Punct(tt) => bridge::TokenTree::Punct(tt.0),
 183             TokenTree::Ident(tt) => bridge::TokenTree::Ident(tt.0),
 184             TokenTree::Literal(tt) => bridge::TokenTree::Literal(tt.0),
 185         }))
 186     }
 187 }
 188
 189 /// Collects a number of token trees into a single stream.
 190 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 191 impl iter::FromIterator<TokenTree> for TokenStream {
 192     fn from_iter<I: IntoIterator<Item = TokenTree>>(trees: I) -> Self {
 193         trees.into_iter().map(TokenStream::from).collect()
 194     }
 195 }
 196
 197 /// A "flattening" operation on token streams, collects token trees
 198 /// from multiple token streams into a single stream.
 199 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 200 impl iter::FromIterator<TokenStream> for TokenStream {
 201     fn from_iter<I: IntoIterator<Item = TokenStream>>(streams: I) -> Self {
 202         let mut builder = bridge::client::TokenStreamBuilder::new();
 203         streams.into_iter().for_each(|stream| builder.push(stream.0));
 204         TokenStream(builder.build())
 205     }
 206 }
 207
 208 #[stable(feature = "token_stream_extend", since = "1.30.0")]
 209 impl Extend<TokenTree> for TokenStream {
 210     fn extend<I: IntoIterator<Item = TokenTree>>(&mut self, trees: I) {
 211         self.extend(trees.into_iter().map(TokenStream::from));
 212     }
 213 }
 214
 215 #[stable(feature = "token_stream_extend", since = "1.30.0")]
 216 impl Extend<TokenStream> for TokenStream {
 217     fn extend<I: IntoIterator<Item = TokenStream>>(&mut self, streams: I) {
 218         // FIXME(eddyb) Use an optimized implementation if/when possible.
 219         *self = iter::once(mem::replace(self, Self::new())).chain(streams).collect();
 220     }
 221 }
 222
 223 /// Public implementation details for the `TokenStream` type, such as iterators.
 224 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 225 pub mod token_stream {
 226     use crate::{bridge, Group, Ident, Literal, Punct, TokenStream, TokenTree};
 227
 228     /// An iterator over `TokenStream`'s `TokenTree`s.
 229     /// The iteration is "shallow", e.g., the iterator doesn't recurse into delimited groups,
 230     /// and returns whole groups as token trees.
 231     #[derive(Clone)]
 232     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 233     pub struct IntoIter(bridge::client::TokenStreamIter);
 234
 235     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 236     impl Iterator for IntoIter {
 237         type Item = TokenTree;
 238
 239         fn next(&mut self) -> Option<TokenTree> {
 240             self.0.next().map(|tree| match tree {
 241                 bridge::TokenTree::Group(tt) => TokenTree::Group(Group(tt)),
 242                 bridge::TokenTree::Punct(tt) => TokenTree::Punct(Punct(tt)),
 243                 bridge::TokenTree::Ident(tt) => TokenTree::Ident(Ident(tt)),
 244                 bridge::TokenTree::Literal(tt) => TokenTree::Literal(Literal(tt)),
 245             })
 246         }
 247     }
 248
 249     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 250     impl IntoIterator for TokenStream {
 251         type Item = TokenTree;
 252         type IntoIter = IntoIter;
 253
 254         fn into_iter(self) -> IntoIter {
 255             IntoIter(self.0.into_iter())
 256         }
 257     }
 258 }
 259
 260 /// `quote!(..)` accepts arbitrary tokens and expands into a `TokenStream` describing the input.
 261 /// For example, `quote!(a + b)` will produce a expression, that, when evaluated, constructs
 262 /// the `TokenStream` `[Ident("a"), Punct('+', Alone), Ident("b")]`.
 263 ///
 264 /// Unquoting is done with `$`, and works by taking the single next ident as the unquoted term.
 265 /// To quote `$` itself, use `$$`.
 266 #[unstable(feature = "proc_macro_quote", issue = "54722")]
 267 #[allow_internal_unstable(proc_macro_def_site)]
 268 #[rustc_builtin_macro]
 269 pub macro quote($($t:tt)*) {
 270     /* compiler built-in */
 271 }
 272
 273 #[unstable(feature = "proc_macro_internals", issue = "27812")]
 274 #[doc(hidden)]
 275 mod quote;
 276
 277 /// A region of source code, along with macro expansion information.
 278 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 279 #[derive(Copy, Clone)]
 280 pub struct Span(bridge::client::Span);
 281
 282 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 283 impl !Send for Span {}
 284 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 285 impl !Sync for Span {}
 286
 287 macro_rules! diagnostic_method {
 288     ($name:ident, $level:expr) => {
 289         /// Creates a new `Diagnostic` with the given `message` at the span
 290         /// `self`.
 291         #[unstable(feature = "proc_macro_diagnostic", issue = "54140")]
 292         pub fn $name<T: Into<String>>(self, message: T) -> Diagnostic {
 293             Diagnostic::spanned(self, $level, message)
 294         }
 295     };
 296 }
 297
 298 impl Span {
 299     /// A span that resolves at the macro definition site.
 300     #[unstable(feature = "proc_macro_def_site", issue = "54724")]
 301     pub fn def_site() -> Span {
 302         Span(bridge::client::Span::def_site())
 303     }
 304
 305     /// The span of the invocation of the current procedural macro.
 306     /// Identifiers created with this span will be resolved as if they were written
 307     /// directly at the macro call location (call-site hygiene) and other code
 308     /// at the macro call site will be able to refer to them as well.
 309     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 310     pub fn call_site() -> Span {
 311         Span(bridge::client::Span::call_site())
 312     }
 313
 314     /// A span that represents `macro_rules` hygiene, and sometimes resolves at the macro
 315     /// definition site (local variables, labels, `$crate`) and sometimes at the macro
 316     /// call site (everything else).
 317     /// The span location is taken from the call-site.
 318     #[stable(feature = "proc_macro_mixed_site", since = "1.45.0")]
 319     pub fn mixed_site() -> Span {
 320         Span(bridge::client::Span::mixed_site())
 321     }
 322
 323     /// The original source file into which this span points.
 324     #[unstable(feature = "proc_macro_span", issue = "54725")]
 325     pub fn source_file(&self) -> SourceFile {
 326         SourceFile(self.0.source_file())
 327     }
 328
 329     /// The `Span` for the tokens in the previous macro expansion from which
 330     /// `self` was generated from, if any.
 331     #[unstable(feature = "proc_macro_span", issue = "54725")]
 332     pub fn parent(&self) -> Option<Span> {
 333         self.0.parent().map(Span)
 334     }
 335
 336     /// The span for the origin source code that `self` was generated from. If
 337     /// this `Span` wasn't generated from other macro expansions then the return
 338     /// value is the same as `*self`.
 339     #[unstable(feature = "proc_macro_span", issue = "54725")]
 340     pub fn source(&self) -> Span {
 341         Span(self.0.source())
 342     }
 343
 344     /// Gets the starting line/column in the source file for this span.
 345     #[unstable(feature = "proc_macro_span", issue = "54725")]
 346     pub fn start(&self) -> LineColumn {
 347         self.0.start()
 348     }
 349
 350     /// Gets the ending line/column in the source file for this span.
 351     #[unstable(feature = "proc_macro_span", issue = "54725")]
 352     pub fn end(&self) -> LineColumn {
 353         self.0.end()
 354     }
 355
 356     /// Creates a new span encompassing `self` and `other`.
 357     ///
 358     /// Returns `None` if `self` and `other` are from different files.
 359     #[unstable(feature = "proc_macro_span", issue = "54725")]
 360     pub fn join(&self, other: Span) -> Option<Span> {
 361         self.0.join(other.0).map(Span)
 362     }
 363
 364     /// Creates a new span with the same line/column information as `self` but
 365     /// that resolves symbols as though it were at `other`.
 366     #[stable(feature = "proc_macro_span_resolved_at", since = "1.45.0")]
 367     pub fn resolved_at(&self, other: Span) -> Span {
 368         Span(self.0.resolved_at(other.0))
 369     }
 370
 371     /// Creates a new span with the same name resolution behavior as `self` but
 372     /// with the line/column information of `other`.
 373     #[stable(feature = "proc_macro_span_located_at", since = "1.45.0")]
 374     pub fn located_at(&self, other: Span) -> Span {
 375         other.resolved_at(*self)
 376     }
 377
 378     /// Compares to spans to see if they're equal.
 379     #[unstable(feature = "proc_macro_span", issue = "54725")]
 380     pub fn eq(&self, other: &Span) -> bool {
 381         self.0 == other.0
 382     }
 383
 384     /// Returns the source text behind a span. This preserves the original source
 385     /// code, including spaces and comments. It only returns a result if the span
 386     /// corresponds to real source code.
 387     ///
 388     /// Note: The observable result of a macro should only rely on the tokens and
 389     /// not on this source text. The result of this function is a best effort to
 390     /// be used for diagnostics only.
 391     #[unstable(feature = "proc_macro_span", issue = "54725")]
 392     pub fn source_text(&self) -> Option<String> {
 393         self.0.source_text()
 394     }
 395
 396     diagnostic_method!(error, Level::Error);
 397     diagnostic_method!(warning, Level::Warning);
 398     diagnostic_method!(note, Level::Note);
 399     diagnostic_method!(help, Level::Help);
 400 }
 401
 402 /// Prints a span in a form convenient for debugging.
 403 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 404 impl fmt::Debug for Span {
 405     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 406         self.0.fmt(f)
 407     }
 408 }
 409
 410 /// A line-column pair representing the start or end of a `Span`.
 411 #[unstable(feature = "proc_macro_span", issue = "54725")]
 412 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 413 pub struct LineColumn {
 414     /// The 1-indexed line in the source file on which the span starts or ends (inclusive).
 415     #[unstable(feature = "proc_macro_span", issue = "54725")]
 416     pub line: usize,
 417     /// The 0-indexed column (in UTF-8 characters) in the source file on which
 418     /// the span starts or ends (inclusive).
 419     #[unstable(feature = "proc_macro_span", issue = "54725")]
 420     pub column: usize,
 421 }
 422
 423 #[unstable(feature = "proc_macro_span", issue = "54725")]
 424 impl !Send for LineColumn {}
 425 #[unstable(feature = "proc_macro_span", issue = "54725")]
 426 impl !Sync for LineColumn {}
 427
 428 #[unstable(feature = "proc_macro_span", issue = "54725")]
 429 impl Ord for LineColumn {
 430     fn cmp(&self, other: &Self) -> Ordering {
 431         self.line.cmp(&other.line).then(self.column.cmp(&other.column))
 432     }
 433 }
 434
 435 #[unstable(feature = "proc_macro_span", issue = "54725")]
 436 impl PartialOrd for LineColumn {
 437     fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
 438         Some(self.cmp(other))
 439     }
 440 }
 441
 442 /// The source file of a given `Span`.
 443 #[unstable(feature = "proc_macro_span", issue = "54725")]
 444 #[derive(Clone)]
 445 pub struct SourceFile(bridge::client::SourceFile);
 446
 447 impl SourceFile {
 448     /// Gets the path to this source file.
 449     ///
 450     /// ### Note
 451     /// If the code span associated with this `SourceFile` was generated by an external macro, this
 452     /// macro, this may not be an actual path on the filesystem. Use [`is_real`] to check.
 453     ///
 454     /// Also note that even if `is_real` returns `true`, if `--remap-path-prefix` was passed on
 455     /// the command line, the path as given may not actually be valid.
 456     ///
 457     /// [`is_real`]: Self::is_real
 458     #[unstable(feature = "proc_macro_span", issue = "54725")]
 459     pub fn path(&self) -> PathBuf {
 460         PathBuf::from(self.0.path())
 461     }
 462
 463     /// Returns `true` if this source file is a real source file, and not generated by an external
 464     /// macro's expansion.
 465     #[unstable(feature = "proc_macro_span", issue = "54725")]
 466     pub fn is_real(&self) -> bool {
 467         // This is a hack until intercrate spans are implemented and we can have real source files
 468         // for spans generated in external macros.
 469         // https://github.com/rust-lang/rust/pull/43604#issuecomment-333334368
 470         self.0.is_real()
 471     }
 472 }
 473
 474 #[unstable(feature = "proc_macro_span", issue = "54725")]
 475 impl fmt::Debug for SourceFile {
 476     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 477         f.debug_struct("SourceFile")
 478             .field("path", &self.path())
 479             .field("is_real", &self.is_real())
 480             .finish()
 481     }
 482 }
 483
 484 #[unstable(feature = "proc_macro_span", issue = "54725")]
 485 impl PartialEq for SourceFile {
 486     fn eq(&self, other: &Self) -> bool {
 487         self.0.eq(&other.0)
 488     }
 489 }
 490
 491 #[unstable(feature = "proc_macro_span", issue = "54725")]
 492 impl Eq for SourceFile {}
 493
 494 /// A single token or a delimited sequence of token trees (e.g., `[1, (), ..]`).
 495 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 496 #[derive(Clone)]
 497 pub enum TokenTree {
 498     /// A token stream surrounded by bracket delimiters.
 499     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 500     Group(#[stable(feature = "proc_macro_lib2", since = "1.29.0")] Group),
 501     /// An identifier.
 502     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 503     Ident(#[stable(feature = "proc_macro_lib2", since = "1.29.0")] Ident),
 504     /// A single punctuation character (`+`, `,`, `$`, etc.).
 505     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 506     Punct(#[stable(feature = "proc_macro_lib2", since = "1.29.0")] Punct),
 507     /// A literal character (`'a'`), string (`"hello"`), number (`2.3`), etc.
 508     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 509     Literal(#[stable(feature = "proc_macro_lib2", since = "1.29.0")] Literal),
 510 }
 511
 512 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 513 impl !Send for TokenTree {}
 514 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 515 impl !Sync for TokenTree {}
 516
 517 impl TokenTree {
 518     /// Returns the span of this tree, delegating to the `span` method of
 519     /// the contained token or a delimited stream.
 520     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 521     pub fn span(&self) -> Span {
 522         match *self {
 523             TokenTree::Group(ref t) => t.span(),
 524             TokenTree::Ident(ref t) => t.span(),
 525             TokenTree::Punct(ref t) => t.span(),
 526             TokenTree::Literal(ref t) => t.span(),
 527         }
 528     }
 529
 530     /// Configures the span for *only this token*.
 531     ///
 532     /// Note that if this token is a `Group` then this method will not configure
 533     /// the span of each of the internal tokens, this will simply delegate to
 534     /// the `set_span` method of each variant.
 535     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 536     pub fn set_span(&mut self, span: Span) {
 537         match *self {
 538             TokenTree::Group(ref mut t) => t.set_span(span),
 539             TokenTree::Ident(ref mut t) => t.set_span(span),
 540             TokenTree::Punct(ref mut t) => t.set_span(span),
 541             TokenTree::Literal(ref mut t) => t.set_span(span),
 542         }
 543     }
 544 }
 545
 546 /// Prints token tree in a form convenient for debugging.
 547 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 548 impl fmt::Debug for TokenTree {
 549     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 550         // Each of these has the name in the struct type in the derived debug,
 551         // so don't bother with an extra layer of indirection
 552         match *self {
 553             TokenTree::Group(ref tt) => tt.fmt(f),
 554             TokenTree::Ident(ref tt) => tt.fmt(f),
 555             TokenTree::Punct(ref tt) => tt.fmt(f),
 556             TokenTree::Literal(ref tt) => tt.fmt(f),
 557         }
 558     }
 559 }
 560
 561 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 562 impl From<Group> for TokenTree {
 563     fn from(g: Group) -> TokenTree {
 564         TokenTree::Group(g)
 565     }
 566 }
 567
 568 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 569 impl From<Ident> for TokenTree {
 570     fn from(g: Ident) -> TokenTree {
 571         TokenTree::Ident(g)
 572     }
 573 }
 574
 575 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 576 impl From<Punct> for TokenTree {
 577     fn from(g: Punct) -> TokenTree {
 578         TokenTree::Punct(g)
 579     }
 580 }
 581
 582 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 583 impl From<Literal> for TokenTree {
 584     fn from(g: Literal) -> TokenTree {
 585         TokenTree::Literal(g)
 586     }
 587 }
 588
 589 // N.B., the bridge only provides `to_string`, implement `fmt::Display`
 590 // based on it (the reverse of the usual relationship between the two).
 591 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 592 impl ToString for TokenTree {
 593     fn to_string(&self) -> String {
 594         match *self {
 595             TokenTree::Group(ref t) => t.to_string(),
 596             TokenTree::Ident(ref t) => t.to_string(),
 597             TokenTree::Punct(ref t) => t.to_string(),
 598             TokenTree::Literal(ref t) => t.to_string(),
 599         }
 600     }
 601 }
 602
 603 /// Prints the token tree as a string that is supposed to be losslessly convertible back
 604 /// into the same token tree (modulo spans), except for possibly `TokenTree::Group`s
 605 /// with `Delimiter::None` delimiters and negative numeric literals.
 606 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 607 impl fmt::Display for TokenTree {
 608     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 609         f.write_str(&self.to_string())
 610     }
 611 }
 612
 613 /// A delimited token stream.
 614 ///
 615 /// A `Group` internally contains a `TokenStream` which is surrounded by `Delimiter`s.
 616 #[derive(Clone)]
 617 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 618 pub struct Group(bridge::client::Group);
 619
 620 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 621 impl !Send for Group {}
 622 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 623 impl !Sync for Group {}
 624
 625 /// Describes how a sequence of token trees is delimited.
 626 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 627 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 628 pub enum Delimiter {
 629     /// `( ... )`
 630     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 631     Parenthesis,
 632     /// `{ ... }`
 633     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 634     Brace,
 635     /// `[ ... ]`
 636     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 637     Bracket,
 638     /// `Ø ... Ø`
 639     /// An implicit delimiter, that may, for example, appear around tokens coming from a
 640     /// "macro variable" `$var`. It is important to preserve operator priorities in cases like
 641     /// `$var * 3` where `$var` is `1 + 2`.
 642     /// Implicit delimiters may not survive roundtrip of a token stream through a string.
 643     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 644     None,
 645 }
 646
 647 impl Group {
 648     /// Creates a new `Group` with the given delimiter and token stream.
 649     ///
 650     /// This constructor will set the span for this group to
 651     /// `Span::call_site()`. To change the span you can use the `set_span`
 652     /// method below.
 653     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 654     pub fn new(delimiter: Delimiter, stream: TokenStream) -> Group {
 655         Group(bridge::client::Group::new(delimiter, stream.0))
 656     }
 657
 658     /// Returns the delimiter of this `Group`
 659     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 660     pub fn delimiter(&self) -> Delimiter {
 661         self.0.delimiter()
 662     }
 663
 664     /// Returns the `TokenStream` of tokens that are delimited in this `Group`.
 665     ///
 666     /// Note that the returned token stream does not include the delimiter
 667     /// returned above.
 668     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 669     pub fn stream(&self) -> TokenStream {
 670         TokenStream(self.0.stream())
 671     }
 672
 673     /// Returns the span for the delimiters of this token stream, spanning the
 674     /// entire `Group`.
 675     ///
 676     /// ```text
 677     /// pub fn span(&self) -> Span {
 678     ///            ^^^^^^^
 679     /// ```
 680     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 681     pub fn span(&self) -> Span {
 682         Span(self.0.span())
 683     }
 684
 685     /// Returns the span pointing to the opening delimiter of this group.
 686     ///
 687     /// ```text
 688     /// pub fn span_open(&self) -> Span {
 689     ///                 ^
 690     /// ```
 691     #[unstable(feature = "proc_macro_span", issue = "54725")]
 692     pub fn span_open(&self) -> Span {
 693         Span(self.0.span_open())
 694     }
 695
 696     /// Returns the span pointing to the closing delimiter of this group.
 697     ///
 698     /// ```text
 699     /// pub fn span_close(&self) -> Span {
 700     ///                        ^
 701     /// ```
 702     #[unstable(feature = "proc_macro_span", issue = "54725")]
 703     pub fn span_close(&self) -> Span {
 704         Span(self.0.span_close())
 705     }
 706
 707     /// Configures the span for this `Group`'s delimiters, but not its internal
 708     /// tokens.
 709     ///
 710     /// This method will **not** set the span of all the internal tokens spanned
 711     /// by this group, but rather it will only set the span of the delimiter
 712     /// tokens at the level of the `Group`.
 713     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 714     pub fn set_span(&mut self, span: Span) {
 715         self.0.set_span(span.0);
 716     }
 717 }
 718
 719 // N.B., the bridge only provides `to_string`, implement `fmt::Display`
 720 // based on it (the reverse of the usual relationship between the two).
 721 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 722 impl ToString for Group {
 723     fn to_string(&self) -> String {
 724         TokenStream::from(TokenTree::from(self.clone())).to_string()
 725     }
 726 }
 727
 728 /// Prints the group as a string that should be losslessly convertible back
 729 /// into the same group (modulo spans), except for possibly `TokenTree::Group`s
 730 /// with `Delimiter::None` delimiters.
 731 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 732 impl fmt::Display for Group {
 733     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 734         f.write_str(&self.to_string())
 735     }
 736 }
 737
 738 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 739 impl fmt::Debug for Group {
 740     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 741         f.debug_struct("Group")
 742             .field("delimiter", &self.delimiter())
 743             .field("stream", &self.stream())
 744             .field("span", &self.span())
 745             .finish()
 746     }
 747 }
 748
 749 /// An `Punct` is an single punctuation character like `+`, `-` or `#`.
 750 ///
 751 /// Multi-character operators like `+=` are represented as two instances of `Punct` with different
 752 /// forms of `Spacing` returned.
 753 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 754 #[derive(Clone)]
 755 pub struct Punct(bridge::client::Punct);
 756
 757 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 758 impl !Send for Punct {}
 759 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 760 impl !Sync for Punct {}
 761
 762 /// Whether an `Punct` is followed immediately by another `Punct` or
 763 /// followed by another token or whitespace.
 764 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 765 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 766 pub enum Spacing {
 767     /// e.g., `+` is `Alone` in `+ =`, `+ident` or `+()`.
 768     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 769     Alone,
 770     /// e.g., `+` is `Joint` in `+=` or `'#`.
 771     /// Additionally, single quote `'` can join with identifiers to form lifetimes `'ident`.
 772     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 773     Joint,
 774 }
 775
 776 impl Punct {
 777     /// Creates a new `Punct` from the given character and spacing.
 778     /// The `ch` argument must be a valid punctuation character permitted by the language,
 779     /// otherwise the function will panic.
 780     ///
 781     /// The returned `Punct` will have the default span of `Span::call_site()`
 782     /// which can be further configured with the `set_span` method below.
 783     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 784     pub fn new(ch: char, spacing: Spacing) -> Punct {
 785         Punct(bridge::client::Punct::new(ch, spacing))
 786     }
 787
 788     /// Returns the value of this punctuation character as `char`.
 789     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 790     pub fn as_char(&self) -> char {
 791         self.0.as_char()
 792     }
 793
 794     /// Returns the spacing of this punctuation character, indicating whether it's immediately
 795     /// followed by another `Punct` in the token stream, so they can potentially be combined into
 796     /// a multi-character operator (`Joint`), or it's followed by some other token or whitespace
 797     /// (`Alone`) so the operator has certainly ended.
 798     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 799     pub fn spacing(&self) -> Spacing {
 800         self.0.spacing()
 801     }
 802
 803     /// Returns the span for this punctuation character.
 804     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 805     pub fn span(&self) -> Span {
 806         Span(self.0.span())
 807     }
 808
 809     /// Configure the span for this punctuation character.
 810     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 811     pub fn set_span(&mut self, span: Span) {
 812         self.0 = self.0.with_span(span.0);
 813     }
 814 }
 815
 816 // N.B., the bridge only provides `to_string`, implement `fmt::Display`
 817 // based on it (the reverse of the usual relationship between the two).
 818 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 819 impl ToString for Punct {
 820     fn to_string(&self) -> String {
 821         TokenStream::from(TokenTree::from(self.clone())).to_string()
 822     }
 823 }
 824
 825 /// Prints the punctuation character as a string that should be losslessly convertible
 826 /// back into the same character.
 827 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 828 impl fmt::Display for Punct {
 829     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 830         f.write_str(&self.to_string())
 831     }
 832 }
 833
 834 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 835 impl fmt::Debug for Punct {
 836     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 837         f.debug_struct("Punct")
 838             .field("ch", &self.as_char())
 839             .field("spacing", &self.spacing())
 840             .field("span", &self.span())
 841             .finish()
 842     }
 843 }
 844
 845 #[stable(feature = "proc_macro_punct_eq", since = "1.50.0")]
 846 impl PartialEq<char> for Punct {
 847     fn eq(&self, rhs: &char) -> bool {
 848         self.as_char() == *rhs
 849     }
 850 }
 851
 852 #[stable(feature = "proc_macro_punct_eq_flipped", since = "1.52.0")]
 853 impl PartialEq<Punct> for char {
 854     fn eq(&self, rhs: &Punct) -> bool {
 855         *self == rhs.as_char()
 856     }
 857 }
 858
 859 /// An identifier (`ident`).
 860 #[derive(Clone)]
 861 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 862 pub struct Ident(bridge::client::Ident);
 863
 864 impl Ident {
 865     /// Creates a new `Ident` with the given `string` as well as the specified
 866     /// `span`.
 867     /// The `string` argument must be a valid identifier permitted by the
 868     /// language (including keywords, e.g. `self` or `fn`). Otherwise, the function will panic.
 869     ///
 870     /// Note that `span`, currently in rustc, configures the hygiene information
 871     /// for this identifier.
 872     ///
 873     /// As of this time `Span::call_site()` explicitly opts-in to "call-site" hygiene
 874     /// meaning that identifiers created with this span will be resolved as if they were written
 875     /// directly at the location of the macro call, and other code at the macro call site will be
 876     /// able to refer to them as well.
 877     ///
 878     /// Later spans like `Span::def_site()` will allow to opt-in to "definition-site" hygiene
 879     /// meaning that identifiers created with this span will be resolved at the location of the
 880     /// macro definition and other code at the macro call site will not be able to refer to them.
 881     ///
 882     /// Due to the current importance of hygiene this constructor, unlike other
 883     /// tokens, requires a `Span` to be specified at construction.
 884     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 885     pub fn new(string: &str, span: Span) -> Ident {
 886         Ident(bridge::client::Ident::new(string, span.0, false))
 887     }
 888
 889     /// Same as `Ident::new`, but creates a raw identifier (`r#ident`).
 890     /// The `string` argument be a valid identifier permitted by the language
 891     /// (including keywords, e.g. `fn`). Keywords which are usable in path segments
 892     /// (e.g. `self`, `super`) are not supported, and will cause a panic.
 893     #[stable(feature = "proc_macro_raw_ident", since = "1.47.0")]
 894     pub fn new_raw(string: &str, span: Span) -> Ident {
 895         Ident(bridge::client::Ident::new(string, span.0, true))
 896     }
 897
 898     /// Returns the span of this `Ident`, encompassing the entire string returned
 899     /// by [`to_string`](Self::to_string).
 900     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 901     pub fn span(&self) -> Span {
 902         Span(self.0.span())
 903     }
 904
 905     /// Configures the span of this `Ident`, possibly changing its hygiene context.
 906     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 907     pub fn set_span(&mut self, span: Span) {
 908         self.0 = self.0.with_span(span.0);
 909     }
 910 }
 911
 912 // N.B., the bridge only provides `to_string`, implement `fmt::Display`
 913 // based on it (the reverse of the usual relationship between the two).
 914 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 915 impl ToString for Ident {
 916     fn to_string(&self) -> String {
 917         TokenStream::from(TokenTree::from(self.clone())).to_string()
 918     }
 919 }
 920
 921 /// Prints the identifier as a string that should be losslessly convertible
 922 /// back into the same identifier.
 923 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 924 impl fmt::Display for Ident {
 925     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 926         f.write_str(&self.to_string())
 927     }
 928 }
 929
 930 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 931 impl fmt::Debug for Ident {
 932     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 933         f.debug_struct("Ident")
 934             .field("ident", &self.to_string())
 935             .field("span", &self.span())
 936             .finish()
 937     }
 938 }
 939
 940 /// A literal string (`"hello"`), byte string (`b"hello"`),
 941 /// character (`'a'`), byte character (`b'a'`), an integer or floating point number
 942 /// with or without a suffix (`1`, `1u8`, `2.3`, `2.3f32`).
 943 /// Boolean literals like `true` and `false` do not belong here, they are `Ident`s.
 944 #[derive(Clone)]
 945 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 946 pub struct Literal(bridge::client::Literal);
 947
 948 macro_rules! suffixed_int_literals {
 949     ($($name:ident => $kind:ident,)*) => ($(
 950         /// Creates a new suffixed integer literal with the specified value.
 951         ///
 952         /// This function will create an integer like `1u32` where the integer
 953         /// value specified is the first part of the token and the integral is
 954         /// also suffixed at the end.
 955         /// Literals created from negative numbers may not survive round-trips through
 956         /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
 957         ///
 958         /// Literals created through this method have the `Span::call_site()`
 959         /// span by default, which can be configured with the `set_span` method
 960         /// below.
 961         #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 962         pub fn $name(n: $kind) -> Literal {
 963             Literal(bridge::client::Literal::typed_integer(&n.to_string(), stringify!($kind)))
 964         }
 965     )*)
 966 }
 967
 968 macro_rules! unsuffixed_int_literals {
 969     ($($name:ident => $kind:ident,)*) => ($(
 970         /// Creates a new unsuffixed integer literal with the specified value.
 971         ///
 972         /// This function will create an integer like `1` where the integer
 973         /// value specified is the first part of the token. No suffix is
 974         /// specified on this token, meaning that invocations like
 975         /// `Literal::i8_unsuffixed(1)` are equivalent to
 976         /// `Literal::u32_unsuffixed(1)`.
 977         /// Literals created from negative numbers may not survive rountrips through
 978         /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
 979         ///
 980         /// Literals created through this method have the `Span::call_site()`
 981         /// span by default, which can be configured with the `set_span` method
 982         /// below.
 983         #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 984         pub fn $name(n: $kind) -> Literal {
 985             Literal(bridge::client::Literal::integer(&n.to_string()))
 986         }
 987     )*)
 988 }
 989
 990 impl Literal {
 991     suffixed_int_literals! {
 992         u8_suffixed => u8,
 993         u16_suffixed => u16,
 994         u32_suffixed => u32,
 995         u64_suffixed => u64,
 996         u128_suffixed => u128,
 997         usize_suffixed => usize,
 998         i8_suffixed => i8,
 999         i16_suffixed => i16,
1000         i32_suffixed => i32,
1001         i64_suffixed => i64,
1002         i128_suffixed => i128,
1003         isize_suffixed => isize,
1004     }
1005
1006     unsuffixed_int_literals! {
1007         u8_unsuffixed => u8,
1008         u16_unsuffixed => u16,
1009         u32_unsuffixed => u32,
1010         u64_unsuffixed => u64,
1011         u128_unsuffixed => u128,
1012         usize_unsuffixed => usize,
1013         i8_unsuffixed => i8,
1014         i16_unsuffixed => i16,
1015         i32_unsuffixed => i32,
1016         i64_unsuffixed => i64,
1017         i128_unsuffixed => i128,
1018         isize_unsuffixed => isize,
1019     }
1020
1021     /// Creates a new unsuffixed floating-point literal.
1022     ///
1023     /// This constructor is similar to those like `Literal::i8_unsuffixed` where
1024     /// the float's value is emitted directly into the token but no suffix is
1025     /// used, so it may be inferred to be a `f64` later in the compiler.
1026     /// Literals created from negative numbers may not survive rountrips through
1027     /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
1028     ///
1029     /// # Panics
1030     ///
1031     /// This function requires that the specified float is finite, for
1032     /// example if it is infinity or NaN this function will panic.
1033     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
1034     pub fn f32_unsuffixed(n: f32) -> Literal {
1035         if !n.is_finite() {
1036             panic!("Invalid float literal {}", n);
1037         }
1038         Literal(bridge::client::Literal::float(&n.to_string()))
1039     }
1040
1041     /// Creates a new suffixed floating-point literal.
1042     ///
1043     /// This constructor will create a literal like `1.0f32` where the value
1044     /// specified is the preceding part of the token and `f32` is the suffix of
1045     /// the token. This token will always be inferred to be an `f32` in the
1046     /// compiler.
1047     /// Literals created from negative numbers may not survive rountrips through
1048     /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
1049     ///
1050     /// # Panics
1051     ///
1052     /// This function requires that the specified float is finite, for
1053     /// example if it is infinity or NaN this function will panic.
1054     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
1055     pub fn f32_suffixed(n: f32) -> Literal {
1056         if !n.is_finite() {
1057             panic!("Invalid float literal {}", n);
1058         }
1059         Literal(bridge::client::Literal::f32(&n.to_string()))
1060     }
1061
1062     /// Creates a new unsuffixed floating-point literal.
1063     ///
1064     /// This constructor is similar to those like `Literal::i8_unsuffixed` where
1065     /// the float's value is emitted directly into the token but no suffix is
1066     /// used, so it may be inferred to be a `f64` later in the compiler.
1067     /// Literals created from negative numbers may not survive rountrips through
1068     /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
1069     ///
1070     /// # Panics
1071     ///
1072     /// This function requires that the specified float is finite, for
1073     /// example if it is infinity or NaN this function will panic.
1074     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
1075     pub fn f64_unsuffixed(n: f64) -> Literal {
1076         if !n.is_finite() {
1077             panic!("Invalid float literal {}", n);
1078         }
1079         Literal(bridge::client::Literal::float(&n.to_string()))
1080     }
1081
1082     /// Creates a new suffixed floating-point literal.
1083     ///
1084     /// This constructor will create a literal like `1.0f64` where the value
1085     /// specified is the preceding part of the token and `f64` is the suffix of
1086     /// the token. This token will always be inferred to be an `f64` in the
1087     /// compiler.
1088     /// Literals created from negative numbers may not survive rountrips through
1089     /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
1090     ///
1091     /// # Panics
1092     ///
1093     /// This function requires that the specified float is finite, for
1094     /// example if it is infinity or NaN this function will panic.
1095     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
1096     pub fn f64_suffixed(n: f64) -> Literal {
1097         if !n.is_finite() {
1098             panic!("Invalid float literal {}", n);
1099         }
1100         Literal(bridge::client::Literal::f64(&n.to_string()))
1101     }
1102
1103     /// String literal.
1104     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
1105     pub fn string(string: &str) -> Literal {
1106         Literal(bridge::client::Literal::string(string))
1107     }
1108
1109     /// Character literal.
1110     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
1111     pub fn character(ch: char) -> Literal {
1112         Literal(bridge::client::Literal::character(ch))
1113     }
1114
1115     /// Byte string literal.
1116     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
1117     pub fn byte_string(bytes: &[u8]) -> Literal {
1118         Literal(bridge::client::Literal::byte_string(bytes))
1119     }
1120
1121     /// Returns the span encompassing this literal.
1122     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
1123     pub fn span(&self) -> Span {
1124         Span(self.0.span())
1125     }
1126
1127     /// Configures the span associated for this literal.
1128     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
1129     pub fn set_span(&mut self, span: Span) {
1130         self.0.set_span(span.0);
1131     }
1132
1133     /// Returns a `Span` that is a subset of `self.span()` containing only the
1134     /// source bytes in range `range`. Returns `None` if the would-be trimmed
1135     /// span is outside the bounds of `self`.
1136     // FIXME(SergioBenitez): check that the byte range starts and ends at a
1137     // UTF-8 boundary of the source. otherwise, it's likely that a panic will
1138     // occur elsewhere when the source text is printed.
1139     // FIXME(SergioBenitez): there is no way for the user to know what
1140     // `self.span()` actually maps to, so this method can currently only be
1141     // called blindly. For example, `to_string()` for the character 'c' returns
1142     // "'\u{63}'"; there is no way for the user to know whether the source text
1143     // was 'c' or whether it was '\u{63}'.
1144     #[unstable(feature = "proc_macro_span", issue = "54725")]
1145     pub fn subspan<R: RangeBounds<usize>>(&self, range: R) -> Option<Span> {
1146         // HACK(eddyb) something akin to `Option::cloned`, but for `Bound<&T>`.
1147         fn cloned_bound<T: Clone>(bound: Bound<&T>) -> Bound<T> {
1148             match bound {
1149                 Bound::Included(x) => Bound::Included(x.clone()),
1150                 Bound::Excluded(x) => Bound::Excluded(x.clone()),
1151                 Bound::Unbounded => Bound::Unbounded,
1152             }
1153         }
1154
1155         self.0.subspan(cloned_bound(range.start_bound()), cloned_bound(range.end_bound())).map(Span)
1156     }
1157 }
1158
1159 // N.B., the bridge only provides `to_string`, implement `fmt::Display`
1160 // based on it (the reverse of the usual relationship between the two).
1161 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
1162 impl ToString for Literal {
1163     fn to_string(&self) -> String {
1164         TokenStream::from(TokenTree::from(self.clone())).to_string()
1165     }
1166 }
1167
1168 /// Prints the literal as a string that should be losslessly convertible
1169 /// back into the same literal (except for possible rounding for floating point literals).
1170 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
1171 impl fmt::Display for Literal {
1172     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1173         f.write_str(&self.to_string())
1174     }
1175 }
1176
1177 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
1178 impl fmt::Debug for Literal {
1179     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1180         self.0.fmt(f)
1181     }
1182 }
1183
1184 /// Tracked access to environment variables.
1185 #[unstable(feature = "proc_macro_tracked_env", issue = "74690")]
1186 pub mod tracked_env {
1187     use std::env::{self, VarError};
1188     use std::ffi::OsStr;
1189
1190     /// Retrieve an environment variable and add it to build dependency info.
1191     /// Build system executing the compiler will know that the variable was accessed during
1192     /// compilation, and will be able to rerun the build when the value of that variable changes.
1193     /// Besides the dependency tracking this function should be equivalent to `env::var` from the
1194     /// standard library, except that the argument must be UTF-8.
1195     #[unstable(feature = "proc_macro_tracked_env", issue = "74690")]
1196     pub fn var<K: AsRef<OsStr> + AsRef<str>>(key: K) -> Result<String, VarError> {
1197         let key: &str = key.as_ref();
1198         let value = env::var(key);
1199         crate::bridge::client::FreeFunctions::track_env_var(key, value.as_deref().ok());
1200         value
1201     }
1202 }