src/librustc_builtin_macros/format.rs

   1 use ArgumentType::*;
   2 use Position::*;
   3
   4 use rustc_ast::ast;
   5 use rustc_ast::ptr::P;
   6 use rustc_ast::token;
   7 use rustc_ast::tokenstream::TokenStream;
   8 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
   9 use rustc_errors::{pluralize, Applicability, DiagnosticBuilder};
  10 use rustc_expand::base::{self, *};
  11 use rustc_parse_format as parse;
  12 use rustc_span::symbol::{sym, Ident, Symbol};
  13 use rustc_span::{MultiSpan, Span};
  14
  15 use std::borrow::Cow;
  16 use std::collections::hash_map::Entry;
  17
  18 #[derive(PartialEq)]
  19 enum ArgumentType {
  20     Placeholder(&'static str),
  21     Count,
  22 }
  23
  24 enum Position {
  25     Exact(usize),
  26     Named(Symbol),
  27 }
  28
  29 struct Context<'a, 'b> {
  30     ecx: &'a mut ExtCtxt<'b>,
  31     /// The macro's call site. References to unstable formatting internals must
  32     /// use this span to pass the stability checker.
  33     macsp: Span,
  34     /// The span of the format string literal.
  35     fmtsp: Span,
  36
  37     /// List of parsed argument expressions.
  38     /// Named expressions are resolved early, and are appended to the end of
  39     /// argument expressions.
  40     ///
  41     /// Example showing the various data structures in motion:
  42     ///
  43     /// * Original: `"{foo:o} {:o} {foo:x} {0:x} {1:o} {:x} {1:x} {0:o}"`
  44     /// * Implicit argument resolution: `"{foo:o} {0:o} {foo:x} {0:x} {1:o} {1:x} {1:x} {0:o}"`
  45     /// * Name resolution: `"{2:o} {0:o} {2:x} {0:x} {1:o} {1:x} {1:x} {0:o}"`
  46     /// * `arg_types` (in JSON): `[[0, 1, 0], [0, 1, 1], [0, 1]]`
  47     /// * `arg_unique_types` (in simplified JSON): `[["o", "x"], ["o", "x"], ["o", "x"]]`
  48     /// * `names` (in JSON): `{"foo": 2}`
  49     args: Vec<P<ast::Expr>>,
  50     /// Placeholder slot numbers indexed by argument.
  51     arg_types: Vec<Vec<usize>>,
  52     /// Unique format specs seen for each argument.
  53     arg_unique_types: Vec<Vec<ArgumentType>>,
  54     /// Map from named arguments to their resolved indices.
  55     names: FxHashMap<Symbol, usize>,
  56
  57     /// The latest consecutive literal strings, or empty if there weren't any.
  58     literal: String,
  59
  60     /// Collection of the compiled `rt::Argument` structures
  61     pieces: Vec<P<ast::Expr>>,
  62     /// Collection of string literals
  63     str_pieces: Vec<P<ast::Expr>>,
  64     /// Stays `true` if all formatting parameters are default (as in "{}{}").
  65     all_pieces_simple: bool,
  66
  67     /// Mapping between positional argument references and indices into the
  68     /// final generated static argument array. We record the starting indices
  69     /// corresponding to each positional argument, and number of references
  70     /// consumed so far for each argument, to facilitate correct `Position`
  71     /// mapping in `build_piece`. In effect this can be seen as a "flattened"
  72     /// version of `arg_unique_types`.
  73     ///
  74     /// Again with the example described above in docstring for `args`:
  75     ///
  76     /// * `arg_index_map` (in JSON): `[[0, 1, 0], [2, 3, 3], [4, 5]]`
  77     arg_index_map: Vec<Vec<usize>>,
  78
  79     /// Starting offset of count argument slots.
  80     count_args_index_offset: usize,
  81
  82     /// Count argument slots and tracking data structures.
  83     /// Count arguments are separately tracked for de-duplication in case
  84     /// multiple references are made to one argument. For example, in this
  85     /// format string:
  86     ///
  87     /// * Original: `"{:.*} {:.foo$} {1:.*} {:.0$}"`
  88     /// * Implicit argument resolution: `"{1:.0$} {2:.foo$} {1:.3$} {4:.0$}"`
  89     /// * Name resolution: `"{1:.0$} {2:.5$} {1:.3$} {4:.0$}"`
  90     /// * `count_positions` (in JSON): `{0: 0, 5: 1, 3: 2}`
  91     /// * `count_args`: `vec![Exact(0), Exact(5), Exact(3)]`
  92     count_args: Vec<Position>,
  93     /// Relative slot numbers for count arguments.
  94     count_positions: FxHashMap<usize, usize>,
  95     /// Number of count slots assigned.
  96     count_positions_count: usize,
  97
  98     /// Current position of the implicit positional arg pointer, as if it
  99     /// still existed in this phase of processing.
 100     /// Used only for `all_pieces_simple` tracking in `build_piece`.
 101     curarg: usize,
 102     /// Current piece being evaluated, used for error reporting.
 103     curpiece: usize,
 104     /// Keep track of invalid references to positional arguments.
 105     invalid_refs: Vec<(usize, usize)>,
 106     /// Spans of all the formatting arguments, in order.
 107     arg_spans: Vec<Span>,
 108     /// All the formatting arguments that have formatting flags set, in order for diagnostics.
 109     arg_with_formatting: Vec<parse::FormatSpec<'a>>,
 110
 111     /// Whether this format string came from a string literal, as opposed to a macro.
 112     is_literal: bool,
 113 }
 114
 115 /// Parses the arguments from the given list of tokens, returning the diagnostic
 116 /// if there's a parse error so we can continue parsing other format!
 117 /// expressions.
 118 ///
 119 /// If parsing succeeds, the return value is:
 120 ///
 121 /// ```text
 122 /// Some((fmtstr, parsed arguments, index map for named arguments))
 123 /// ```
 124 fn parse_args<'a>(
 125     ecx: &mut ExtCtxt<'a>,
 126     sp: Span,
 127     tts: TokenStream,
 128 ) -> Result<(P<ast::Expr>, Vec<P<ast::Expr>>, FxHashMap<Symbol, usize>), DiagnosticBuilder<'a>> {
 129     let mut args = Vec::<P<ast::Expr>>::new();
 130     let mut names = FxHashMap::<Symbol, usize>::default();
 131
 132     let mut p = ecx.new_parser_from_tts(tts);
 133
 134     if p.token == token::Eof {
 135         return Err(ecx.struct_span_err(sp, "requires at least a format string argument"));
 136     }
 137
 138     let fmtstr = p.parse_expr()?;
 139     let mut first = true;
 140     let mut named = false;
 141
 142     while p.token != token::Eof {
 143         if !p.eat(&token::Comma) {
 144             if first {
 145                 // After `format!(""` we always expect *only* a comma...
 146                 let mut err = ecx.struct_span_err(p.token.span, "expected token: `,`");
 147                 err.span_label(p.token.span, "expected `,`");
 148                 p.maybe_annotate_with_ascription(&mut err, false);
 149                 return Err(err);
 150             } else {
 151                 // ...after that delegate to `expect` to also include the other expected tokens.
 152                 return Err(p.expect(&token::Comma).err().unwrap());
 153             }
 154         }
 155         first = false;
 156         if p.token == token::Eof {
 157             break;
 158         } // accept trailing commas
 159         match p.token.ident() {
 160             Some((ident, _)) if p.look_ahead(1, |t| *t == token::Eq) => {
 161                 named = true;
 162                 p.bump();
 163                 p.expect(&token::Eq)?;
 164                 let e = p.parse_expr()?;
 165                 if let Some(prev) = names.get(&ident.name) {
 166                     ecx.struct_span_err(e.span, &format!("duplicate argument named `{}`", ident))
 167                         .span_label(args[*prev].span, "previously here")
 168                         .span_label(e.span, "duplicate argument")
 169                         .emit();
 170                     continue;
 171                 }
 172
 173                 // Resolve names into slots early.
 174                 // Since all the positional args are already seen at this point
 175                 // if the input is valid, we can simply append to the positional
 176                 // args. And remember the names.
 177                 let slot = args.len();
 178                 names.insert(ident.name, slot);
 179                 args.push(e);
 180             }
 181             _ => {
 182                 let e = p.parse_expr()?;
 183                 if named {
 184                     let mut err = ecx.struct_span_err(
 185                         e.span,
 186                         "positional arguments cannot follow named arguments",
 187                     );
 188                     err.span_label(e.span, "positional arguments must be before named arguments");
 189                     for pos in names.values() {
 190                         err.span_label(args[*pos].span, "named argument");
 191                     }
 192                     err.emit();
 193                 }
 194                 args.push(e);
 195             }
 196         }
 197     }
 198     Ok((fmtstr, args, names))
 199 }
 200
 201 impl<'a, 'b> Context<'a, 'b> {
 202     fn resolve_name_inplace(&self, p: &mut parse::Piece<'_>) {
 203         // NOTE: the `unwrap_or` branch is needed in case of invalid format
 204         // arguments, e.g., `format_args!("{foo}")`.
 205         let lookup = |s: Symbol| *self.names.get(&s).unwrap_or(&0);
 206
 207         match *p {
 208             parse::String(_) => {}
 209             parse::NextArgument(ref mut arg) => {
 210                 if let parse::ArgumentNamed(s) = arg.position {
 211                     arg.position = parse::ArgumentIs(lookup(s));
 212                 }
 213                 if let parse::CountIsName(s) = arg.format.width {
 214                     arg.format.width = parse::CountIsParam(lookup(s));
 215                 }
 216                 if let parse::CountIsName(s) = arg.format.precision {
 217                     arg.format.precision = parse::CountIsParam(lookup(s));
 218                 }
 219             }
 220         }
 221     }
 222
 223     /// Verifies one piece of a parse string, and remembers it if valid.
 224     /// All errors are not emitted as fatal so we can continue giving errors
 225     /// about this and possibly other format strings.
 226     fn verify_piece(&mut self, p: &parse::Piece<'_>) {
 227         match *p {
 228             parse::String(..) => {}
 229             parse::NextArgument(ref arg) => {
 230                 // width/precision first, if they have implicit positional
 231                 // parameters it makes more sense to consume them first.
 232                 self.verify_count(arg.format.width);
 233                 self.verify_count(arg.format.precision);
 234
 235                 // argument second, if it's an implicit positional parameter
 236                 // it's written second, so it should come after width/precision.
 237                 let pos = match arg.position {
 238                     parse::ArgumentIs(i) | parse::ArgumentImplicitlyIs(i) => Exact(i),
 239                     parse::ArgumentNamed(s) => Named(s),
 240                 };
 241
 242                 let ty = Placeholder(match &arg.format.ty[..] {
 243                     "" => "Display",
 244                     "?" => "Debug",
 245                     "e" => "LowerExp",
 246                     "E" => "UpperExp",
 247                     "o" => "Octal",
 248                     "p" => "Pointer",
 249                     "b" => "Binary",
 250                     "x" => "LowerHex",
 251                     "X" => "UpperHex",
 252                     _ => {
 253                         let fmtsp = self.fmtsp;
 254                         let sp = arg.format.ty_span.map(|sp| fmtsp.from_inner(sp));
 255                         let mut err = self.ecx.struct_span_err(
 256                             sp.unwrap_or(fmtsp),
 257                             &format!("unknown format trait `{}`", arg.format.ty),
 258                         );
 259                         err.note(
 260                             "the only appropriate formatting traits are:\n\
 261                                 - ``, which uses the `Display` trait\n\
 262                                 - `?`, which uses the `Debug` trait\n\
 263                                 - `e`, which uses the `LowerExp` trait\n\
 264                                 - `E`, which uses the `UpperExp` trait\n\
 265                                 - `o`, which uses the `Octal` trait\n\
 266                                 - `p`, which uses the `Pointer` trait\n\
 267                                 - `b`, which uses the `Binary` trait\n\
 268                                 - `x`, which uses the `LowerHex` trait\n\
 269                                 - `X`, which uses the `UpperHex` trait",
 270                         );
 271                         if let Some(sp) = sp {
 272                             for (fmt, name) in &[
 273                                 ("", "Display"),
 274                                 ("?", "Debug"),
 275                                 ("e", "LowerExp"),
 276                                 ("E", "UpperExp"),
 277                                 ("o", "Octal"),
 278                                 ("p", "Pointer"),
 279                                 ("b", "Binary"),
 280                                 ("x", "LowerHex"),
 281                                 ("X", "UpperHex"),
 282                             ] {
 283                                 // FIXME: rustfix (`run-rustfix`) fails to apply suggestions.
 284                                 // > "Cannot replace slice of data that was already replaced"
 285                                 err.tool_only_span_suggestion(
 286                                     sp,
 287                                     &format!("use the `{}` trait", name),
 288                                     (*fmt).to_string(),
 289                                     Applicability::MaybeIncorrect,
 290                                 );
 291                             }
 292                         }
 293                         err.emit();
 294                         "<invalid>"
 295                     }
 296                 });
 297                 self.verify_arg_type(pos, ty);
 298                 self.curpiece += 1;
 299             }
 300         }
 301     }
 302
 303     fn verify_count(&mut self, c: parse::Count) {
 304         match c {
 305             parse::CountImplied | parse::CountIs(..) => {}
 306             parse::CountIsParam(i) => {
 307                 self.verify_arg_type(Exact(i), Count);
 308             }
 309             parse::CountIsName(s) => {
 310                 self.verify_arg_type(Named(s), Count);
 311             }
 312         }
 313     }
 314
 315     fn describe_num_args(&self) -> Cow<'_, str> {
 316         match self.args.len() {
 317             0 => "no arguments were given".into(),
 318             1 => "there is 1 argument".into(),
 319             x => format!("there are {} arguments", x).into(),
 320         }
 321     }
 322
 323     /// Handle invalid references to positional arguments. Output different
 324     /// errors for the case where all arguments are positional and for when
 325     /// there are named arguments or numbered positional arguments in the
 326     /// format string.
 327     fn report_invalid_references(&self, numbered_position_args: bool) {
 328         let mut e;
 329         let sp = if !self.arg_spans.is_empty() {
 330             // Point at the formatting arguments.
 331             MultiSpan::from_spans(self.arg_spans.clone())
 332         } else {
 333             MultiSpan::from_span(self.fmtsp)
 334         };
 335         let refs =
 336             self.invalid_refs.iter().map(|(r, pos)| (r.to_string(), self.arg_spans.get(*pos)));
 337
 338         let mut zero_based_note = false;
 339
 340         let count = self.pieces.len()
 341             + self.arg_with_formatting.iter().filter(|fmt| fmt.precision_span.is_some()).count();
 342         if self.names.is_empty() && !numbered_position_args && count != self.args.len() {
 343             e = self.ecx.struct_span_err(
 344                 sp,
 345                 &format!(
 346                     "{} positional argument{} in format string, but {}",
 347                     count,
 348                     pluralize!(count),
 349                     self.describe_num_args(),
 350                 ),
 351             );
 352             for arg in &self.args {
 353                 // Point at the arguments that will be formatted.
 354                 e.span_label(arg.span, "");
 355             }
 356         } else {
 357             let (mut refs, spans): (Vec<_>, Vec<_>) = refs.unzip();
 358             // Avoid `invalid reference to positional arguments 7 and 7 (there is 1 argument)`
 359             // for `println!("{7:7$}", 1);`
 360             refs.sort();
 361             refs.dedup();
 362             let (arg_list, mut sp) = if refs.len() == 1 {
 363                 let spans: Vec<_> = spans.into_iter().filter_map(|sp| sp.copied()).collect();
 364                 (
 365                     format!("argument {}", refs[0]),
 366                     if spans.is_empty() {
 367                         MultiSpan::from_span(self.fmtsp)
 368                     } else {
 369                         MultiSpan::from_spans(spans)
 370                     },
 371                 )
 372             } else {
 373                 let pos = MultiSpan::from_spans(spans.into_iter().map(|s| *s.unwrap()).collect());
 374                 let reg = refs.pop().unwrap();
 375                 (format!("arguments {head} and {tail}", head = refs.join(", "), tail = reg,), pos)
 376             };
 377             if self.arg_spans.is_empty() {
 378                 sp = MultiSpan::from_span(self.fmtsp);
 379             }
 380
 381             e = self.ecx.struct_span_err(
 382                 sp,
 383                 &format!(
 384                     "invalid reference to positional {} ({})",
 385                     arg_list,
 386                     self.describe_num_args()
 387                 ),
 388             );
 389             zero_based_note = true;
 390         };
 391
 392         for fmt in &self.arg_with_formatting {
 393             if let Some(span) = fmt.precision_span {
 394                 let span = self.fmtsp.from_inner(span);
 395                 match fmt.precision {
 396                     parse::CountIsParam(pos) if pos > self.args.len() => {
 397                         e.span_label(
 398                             span,
 399                             &format!(
 400                                 "this precision flag expects an `usize` argument at position {}, \
 401                              but {}",
 402                                 pos,
 403                                 self.describe_num_args(),
 404                             ),
 405                         );
 406                         zero_based_note = true;
 407                     }
 408                     parse::CountIsParam(pos) => {
 409                         let count = self.pieces.len()
 410                             + self
 411                                 .arg_with_formatting
 412                                 .iter()
 413                                 .filter(|fmt| fmt.precision_span.is_some())
 414                                 .count();
 415                         e.span_label(span, &format!(
 416                             "this precision flag adds an extra required argument at position {}, \
 417                              which is why there {} expected",
 418                             pos,
 419                             if count == 1 {
 420                                 "is 1 argument".to_string()
 421                             } else {
 422                                 format!("are {} arguments", count)
 423                             },
 424                         ));
 425                         if let Some(arg) = self.args.get(pos) {
 426                             e.span_label(
 427                                 arg.span,
 428                                 "this parameter corresponds to the precision flag",
 429                             );
 430                         }
 431                         zero_based_note = true;
 432                     }
 433                     _ => {}
 434                 }
 435             }
 436             if let Some(span) = fmt.width_span {
 437                 let span = self.fmtsp.from_inner(span);
 438                 match fmt.width {
 439                     parse::CountIsParam(pos) if pos > self.args.len() => {
 440                         e.span_label(
 441                             span,
 442                             &format!(
 443                                 "this width flag expects an `usize` argument at position {}, \
 444                              but {}",
 445                                 pos,
 446                                 self.describe_num_args(),
 447                             ),
 448                         );
 449                         zero_based_note = true;
 450                     }
 451                     _ => {}
 452                 }
 453             }
 454         }
 455         if zero_based_note {
 456             e.note("positional arguments are zero-based");
 457         }
 458         if !self.arg_with_formatting.is_empty() {
 459             e.note(
 460                 "for information about formatting flags, visit \
 461                     https://doc.rust-lang.org/std/fmt/index.html",
 462             );
 463         }
 464
 465         e.emit();
 466     }
 467
 468     /// Actually verifies and tracks a given format placeholder
 469     /// (a.k.a. argument).
 470     fn verify_arg_type(&mut self, arg: Position, ty: ArgumentType) {
 471         match arg {
 472             Exact(arg) => {
 473                 if self.args.len() <= arg {
 474                     self.invalid_refs.push((arg, self.curpiece));
 475                     return;
 476                 }
 477                 match ty {
 478                     Placeholder(_) => {
 479                         // record every (position, type) combination only once
 480                         let seen_ty = &mut self.arg_unique_types[arg];
 481                         let i = seen_ty.iter().position(|x| *x == ty).unwrap_or_else(|| {
 482                             let i = seen_ty.len();
 483                             seen_ty.push(ty);
 484                             i
 485                         });
 486                         self.arg_types[arg].push(i);
 487                     }
 488                     Count => {
 489                         if let Entry::Vacant(e) = self.count_positions.entry(arg) {
 490                             let i = self.count_positions_count;
 491                             e.insert(i);
 492                             self.count_args.push(Exact(arg));
 493                             self.count_positions_count += 1;
 494                         }
 495                     }
 496                 }
 497             }
 498
 499             Named(name) => {
 500                 match self.names.get(&name) {
 501                     Some(&idx) => {
 502                         // Treat as positional arg.
 503                         self.verify_arg_type(Exact(idx), ty)
 504                     }
 505                     None => {
 506                         let capture_feature_enabled = self
 507                             .ecx
 508                             .ecfg
 509                             .features
 510                             .map_or(false, |features| features.format_args_capture);
 511
 512                         // For the moment capturing variables from format strings expanded from macros is
 513                         // disabled (see RFC #2795)
 514                         let can_capture = capture_feature_enabled && self.is_literal;
 515
 516                         if can_capture {
 517                             // Treat this name as a variable to capture from the surrounding scope
 518                             let idx = self.args.len();
 519                             self.arg_types.push(Vec::new());
 520                             self.arg_unique_types.push(Vec::new());
 521                             self.args.push(
 522                                 self.ecx.expr_ident(self.fmtsp, Ident::new(name, self.fmtsp)),
 523                             );
 524                             self.names.insert(name, idx);
 525                             self.verify_arg_type(Exact(idx), ty)
 526                         } else {
 527                             let msg = format!("there is no argument named `{}`", name);
 528                             let sp = if self.is_literal {
 529                                 *self.arg_spans.get(self.curpiece).unwrap_or(&self.fmtsp)
 530                             } else {
 531                                 self.fmtsp
 532                             };
 533                             let mut err = self.ecx.struct_span_err(sp, &msg[..]);
 534
 535                             if capture_feature_enabled && !self.is_literal {
 536                                 err.note(&format!(
 537                                     "did you intend to capture a variable `{}` from \
 538                                      the surrounding scope?",
 539                                     name
 540                                 ));
 541                                 err.note(
 542                                     "to avoid ambiguity, `format_args!` cannot capture variables \
 543                                      when the format string is expanded from a macro",
 544                                 );
 545                             } else if self.ecx.parse_sess().unstable_features.is_nightly_build() {
 546                                 err.help(&format!(
 547                                     "if you intended to capture `{}` from the surrounding scope, add \
 548                                      `#![feature(format_args_capture)]` to the crate attributes",
 549                                     name
 550                                 ));
 551                             }
 552
 553                             err.emit();
 554                         }
 555                     }
 556                 }
 557             }
 558         }
 559     }
 560
 561     /// Builds the mapping between format placeholders and argument objects.
 562     fn build_index_map(&mut self) {
 563         // NOTE: Keep the ordering the same as `into_expr`'s expansion would do!
 564         let args_len = self.args.len();
 565         self.arg_index_map.reserve(args_len);
 566
 567         let mut sofar = 0usize;
 568
 569         // Map the arguments
 570         for i in 0..args_len {
 571             let arg_types = &self.arg_types[i];
 572             let arg_offsets = arg_types.iter().map(|offset| sofar + *offset).collect::<Vec<_>>();
 573             self.arg_index_map.push(arg_offsets);
 574             sofar += self.arg_unique_types[i].len();
 575         }
 576
 577         // Record starting index for counts, which appear just after arguments
 578         self.count_args_index_offset = sofar;
 579     }
 580
 581     fn rtpath(ecx: &ExtCtxt<'_>, s: &str) -> Vec<Ident> {
 582         ecx.std_path(&[sym::fmt, sym::rt, sym::v1, Symbol::intern(s)])
 583     }
 584
 585     fn build_count(&self, c: parse::Count) -> P<ast::Expr> {
 586         let sp = self.macsp;
 587         let count = |c, arg| {
 588             let mut path = Context::rtpath(self.ecx, "Count");
 589             path.push(self.ecx.ident_of(c, sp));
 590             match arg {
 591                 Some(arg) => self.ecx.expr_call_global(sp, path, vec![arg]),
 592                 None => self.ecx.expr_path(self.ecx.path_global(sp, path)),
 593             }
 594         };
 595         match c {
 596             parse::CountIs(i) => count("Is", Some(self.ecx.expr_usize(sp, i))),
 597             parse::CountIsParam(i) => {
 598                 // This needs mapping too, as `i` is referring to a macro
 599                 // argument. If `i` is not found in `count_positions` then
 600                 // the error had already been emitted elsewhere.
 601                 let i = self.count_positions.get(&i).cloned().unwrap_or(0)
 602                     + self.count_args_index_offset;
 603                 count("Param", Some(self.ecx.expr_usize(sp, i)))
 604             }
 605             parse::CountImplied => count("Implied", None),
 606             // should never be the case, names are already resolved
 607             parse::CountIsName(_) => panic!("should never happen"),
 608         }
 609     }
 610
 611     /// Build a literal expression from the accumulated string literals
 612     fn build_literal_string(&mut self) -> P<ast::Expr> {
 613         let sp = self.fmtsp;
 614         let s = Symbol::intern(&self.literal);
 615         self.literal.clear();
 616         self.ecx.expr_str(sp, s)
 617     }
 618
 619     /// Builds a static `rt::Argument` from a `parse::Piece` or append
 620     /// to the `literal` string.
 621     fn build_piece(
 622         &mut self,
 623         piece: &parse::Piece<'a>,
 624         arg_index_consumed: &mut Vec<usize>,
 625     ) -> Option<P<ast::Expr>> {
 626         let sp = self.macsp;
 627         match *piece {
 628             parse::String(s) => {
 629                 self.literal.push_str(s);
 630                 None
 631             }
 632             parse::NextArgument(ref arg) => {
 633                 // Build the position
 634                 let pos = {
 635                     match arg.position {
 636                         parse::ArgumentIs(i) | parse::ArgumentImplicitlyIs(i) => {
 637                             // Map to index in final generated argument array
 638                             // in case of multiple types specified
 639                             let arg_idx = match arg_index_consumed.get_mut(i) {
 640                                 None => 0, // error already emitted elsewhere
 641                                 Some(offset) => {
 642                                     let idx_map = &self.arg_index_map[i];
 643                                     // unwrap_or branch: error already emitted elsewhere
 644                                     let arg_idx = *idx_map.get(*offset).unwrap_or(&0);
 645                                     *offset += 1;
 646                                     arg_idx
 647                                 }
 648                             };
 649                             self.ecx.expr_usize(sp, arg_idx)
 650                         }
 651
 652                         // should never be the case, because names are already
 653                         // resolved.
 654                         parse::ArgumentNamed(_) => panic!("should never happen"),
 655                     }
 656                 };
 657
 658                 let simple_arg = parse::Argument {
 659                     position: {
 660                         // We don't have ArgumentNext any more, so we have to
 661                         // track the current argument ourselves.
 662                         let i = self.curarg;
 663                         self.curarg += 1;
 664                         parse::ArgumentIs(i)
 665                     },
 666                     format: parse::FormatSpec {
 667                         fill: arg.format.fill,
 668                         align: parse::AlignUnknown,
 669                         flags: 0,
 670                         precision: parse::CountImplied,
 671                         precision_span: None,
 672                         width: parse::CountImplied,
 673                         width_span: None,
 674                         ty: arg.format.ty,
 675                         ty_span: arg.format.ty_span,
 676                     },
 677                 };
 678
 679                 let fill = arg.format.fill.unwrap_or(' ');
 680
 681                 let pos_simple = arg.position.index() == simple_arg.position.index();
 682
 683                 if arg.format.precision_span.is_some() || arg.format.width_span.is_some() {
 684                     self.arg_with_formatting.push(arg.format);
 685                 }
 686                 if !pos_simple || arg.format != simple_arg.format || fill != ' ' {
 687                     self.all_pieces_simple = false;
 688                 }
 689
 690                 // Build the format
 691                 let fill = self.ecx.expr_lit(sp, ast::LitKind::Char(fill));
 692                 let align = |name| {
 693                     let mut p = Context::rtpath(self.ecx, "Alignment");
 694                     p.push(self.ecx.ident_of(name, sp));
 695                     self.ecx.path_global(sp, p)
 696                 };
 697                 let align = match arg.format.align {
 698                     parse::AlignLeft => align("Left"),
 699                     parse::AlignRight => align("Right"),
 700                     parse::AlignCenter => align("Center"),
 701                     parse::AlignUnknown => align("Unknown"),
 702                 };
 703                 let align = self.ecx.expr_path(align);
 704                 let flags = self.ecx.expr_u32(sp, arg.format.flags);
 705                 let prec = self.build_count(arg.format.precision);
 706                 let width = self.build_count(arg.format.width);
 707                 let path = self.ecx.path_global(sp, Context::rtpath(self.ecx, "FormatSpec"));
 708                 let fmt = self.ecx.expr_struct(
 709                     sp,
 710                     path,
 711                     vec![
 712                         self.ecx.field_imm(sp, self.ecx.ident_of("fill", sp), fill),
 713                         self.ecx.field_imm(sp, self.ecx.ident_of("align", sp), align),
 714                         self.ecx.field_imm(sp, self.ecx.ident_of("flags", sp), flags),
 715                         self.ecx.field_imm(sp, self.ecx.ident_of("precision", sp), prec),
 716                         self.ecx.field_imm(sp, self.ecx.ident_of("width", sp), width),
 717                     ],
 718                 );
 719
 720                 let path = self.ecx.path_global(sp, Context::rtpath(self.ecx, "Argument"));
 721                 Some(self.ecx.expr_struct(
 722                     sp,
 723                     path,
 724                     vec![
 725                         self.ecx.field_imm(sp, self.ecx.ident_of("position", sp), pos),
 726                         self.ecx.field_imm(sp, self.ecx.ident_of("format", sp), fmt),
 727                     ],
 728                 ))
 729             }
 730         }
 731     }
 732
 733     /// Actually builds the expression which the format_args! block will be
 734     /// expanded to.
 735     fn into_expr(self) -> P<ast::Expr> {
 736         let mut locals =
 737             Vec::with_capacity((0..self.args.len()).map(|i| self.arg_unique_types[i].len()).sum());
 738         let mut counts = Vec::with_capacity(self.count_args.len());
 739         let mut pats = Vec::with_capacity(self.args.len());
 740         let mut heads = Vec::with_capacity(self.args.len());
 741
 742         let names_pos: Vec<_> = (0..self.args.len())
 743             .map(|i| self.ecx.ident_of(&format!("arg{}", i), self.macsp))
 744             .collect();
 745
 746         // First, build up the static array which will become our precompiled
 747         // format "string"
 748         let pieces = self.ecx.expr_vec_slice(self.fmtsp, self.str_pieces);
 749
 750         // Before consuming the expressions, we have to remember spans for
 751         // count arguments as they are now generated separate from other
 752         // arguments, hence have no access to the `P<ast::Expr>`'s.
 753         let spans_pos: Vec<_> = self.args.iter().map(|e| e.span).collect();
 754
 755         // Right now there is a bug such that for the expression:
 756         //      foo(bar(&1))
 757         // the lifetime of `1` doesn't outlast the call to `bar`, so it's not
 758         // valid for the call to `foo`. To work around this all arguments to the
 759         // format! string are shoved into locals. Furthermore, we shove the address
 760         // of each variable because we don't want to move out of the arguments
 761         // passed to this function.
 762         for (i, e) in self.args.into_iter().enumerate() {
 763             let name = names_pos[i];
 764             let span = self.ecx.with_def_site_ctxt(e.span);
 765             pats.push(self.ecx.pat_ident(span, name));
 766             for arg_ty in self.arg_unique_types[i].iter() {
 767                 locals.push(Context::format_arg(self.ecx, self.macsp, e.span, arg_ty, name));
 768             }
 769             heads.push(self.ecx.expr_addr_of(e.span, e));
 770         }
 771         for pos in self.count_args {
 772             let index = match pos {
 773                 Exact(i) => i,
 774                 _ => panic!("should never happen"),
 775             };
 776             let name = names_pos[index];
 777             let span = spans_pos[index];
 778             counts.push(Context::format_arg(self.ecx, self.macsp, span, &Count, name));
 779         }
 780
 781         // Now create a vector containing all the arguments
 782         let args = locals.into_iter().chain(counts.into_iter());
 783
 784         let args_array = self.ecx.expr_vec(self.macsp, args.collect());
 785
 786         // Constructs an AST equivalent to:
 787         //
 788         //      match (&arg0, &arg1) {
 789         //          (tmp0, tmp1) => args_array
 790         //      }
 791         //
 792         // It was:
 793         //
 794         //      let tmp0 = &arg0;
 795         //      let tmp1 = &arg1;
 796         //      args_array
 797         //
 798         // Because of #11585 the new temporary lifetime rule, the enclosing
 799         // statements for these temporaries become the let's themselves.
 800         // If one or more of them are RefCell's, RefCell borrow() will also
 801         // end there; they don't last long enough for args_array to use them.
 802         // The match expression solves the scope problem.
 803         //
 804         // Note, it may also very well be transformed to:
 805         //
 806         //      match arg0 {
 807         //          ref tmp0 => {
 808         //              match arg1 => {
 809         //                  ref tmp1 => args_array } } }
 810         //
 811         // But the nested match expression is proved to perform not as well
 812         // as series of let's; the first approach does.
 813         let pat = self.ecx.pat_tuple(self.macsp, pats);
 814         let arm = self.ecx.arm(self.macsp, pat, args_array);
 815         let head = self.ecx.expr(self.macsp, ast::ExprKind::Tup(heads));
 816         let result = self.ecx.expr_match(self.macsp, head, vec![arm]);
 817
 818         let args_slice = self.ecx.expr_addr_of(self.macsp, result);
 819
 820         // Now create the fmt::Arguments struct with all our locals we created.
 821         let (fn_name, fn_args) = if self.all_pieces_simple {
 822             ("new_v1", vec![pieces, args_slice])
 823         } else {
 824             // Build up the static array which will store our precompiled
 825             // nonstandard placeholders, if there are any.
 826             let fmt = self.ecx.expr_vec_slice(self.macsp, self.pieces);
 827
 828             ("new_v1_formatted", vec![pieces, args_slice, fmt])
 829         };
 830
 831         let path = self.ecx.std_path(&[sym::fmt, sym::Arguments, Symbol::intern(fn_name)]);
 832         self.ecx.expr_call_global(self.macsp, path, fn_args)
 833     }
 834
 835     fn format_arg(
 836         ecx: &ExtCtxt<'_>,
 837         macsp: Span,
 838         mut sp: Span,
 839         ty: &ArgumentType,
 840         arg: Ident,
 841     ) -> P<ast::Expr> {
 842         sp = ecx.with_def_site_ctxt(sp);
 843         let arg = ecx.expr_ident(sp, arg);
 844         let trait_ = match *ty {
 845             Placeholder(trait_) if trait_ == "<invalid>" => return DummyResult::raw_expr(sp, true),
 846             Placeholder(trait_) => trait_,
 847             Count => {
 848                 let path = ecx.std_path(&[sym::fmt, sym::ArgumentV1, sym::from_usize]);
 849                 return ecx.expr_call_global(macsp, path, vec![arg]);
 850             }
 851         };
 852
 853         let path = ecx.std_path(&[sym::fmt, Symbol::intern(trait_), sym::fmt]);
 854         let format_fn = ecx.path_global(sp, path);
 855         let path = ecx.std_path(&[sym::fmt, sym::ArgumentV1, sym::new]);
 856         ecx.expr_call_global(macsp, path, vec![arg, ecx.expr_path(format_fn)])
 857     }
 858 }
 859
 860 fn expand_format_args_impl<'cx>(
 861     ecx: &'cx mut ExtCtxt<'_>,
 862     mut sp: Span,
 863     tts: TokenStream,
 864     nl: bool,
 865 ) -> Box<dyn base::MacResult + 'cx> {
 866     sp = ecx.with_def_site_ctxt(sp);
 867     match parse_args(ecx, sp, tts) {
 868         Ok((efmt, args, names)) => {
 869             MacEager::expr(expand_preparsed_format_args(ecx, sp, efmt, args, names, nl))
 870         }
 871         Err(mut err) => {
 872             err.emit();
 873             DummyResult::any(sp)
 874         }
 875     }
 876 }
 877
 878 pub fn expand_format_args<'cx>(
 879     ecx: &'cx mut ExtCtxt<'_>,
 880     sp: Span,
 881     tts: TokenStream,
 882 ) -> Box<dyn base::MacResult + 'cx> {
 883     expand_format_args_impl(ecx, sp, tts, false)
 884 }
 885
 886 pub fn expand_format_args_nl<'cx>(
 887     ecx: &'cx mut ExtCtxt<'_>,
 888     sp: Span,
 889     tts: TokenStream,
 890 ) -> Box<dyn base::MacResult + 'cx> {
 891     expand_format_args_impl(ecx, sp, tts, true)
 892 }
 893
 894 /// Take the various parts of `format_args!(efmt, args..., name=names...)`
 895 /// and construct the appropriate formatting expression.
 896 pub fn expand_preparsed_format_args(
 897     ecx: &mut ExtCtxt<'_>,
 898     sp: Span,
 899     efmt: P<ast::Expr>,
 900     args: Vec<P<ast::Expr>>,
 901     names: FxHashMap<Symbol, usize>,
 902     append_newline: bool,
 903 ) -> P<ast::Expr> {
 904     // NOTE: this verbose way of initializing `Vec<Vec<ArgumentType>>` is because
 905     // `ArgumentType` does not derive `Clone`.
 906     let arg_types: Vec<_> = (0..args.len()).map(|_| Vec::new()).collect();
 907     let arg_unique_types: Vec<_> = (0..args.len()).map(|_| Vec::new()).collect();
 908
 909     let mut macsp = ecx.call_site();
 910     macsp = ecx.with_def_site_ctxt(macsp);
 911
 912     let msg = "format argument must be a string literal";
 913     let fmt_sp = efmt.span;
 914     let (fmt_str, fmt_style, fmt_span) = match expr_to_spanned_string(ecx, efmt, msg) {
 915         Ok(mut fmt) if append_newline => {
 916             fmt.0 = Symbol::intern(&format!("{}\n", fmt.0));
 917             fmt
 918         }
 919         Ok(fmt) => fmt,
 920         Err(err) => {
 921             if let Some(mut err) = err {
 922                 let sugg_fmt = match args.len() {
 923                     0 => "{}".to_string(),
 924                     _ => format!("{}{{}}", "{} ".repeat(args.len())),
 925                 };
 926                 err.span_suggestion(
 927                     fmt_sp.shrink_to_lo(),
 928                     "you might be missing a string literal to format with",
 929                     format!("\"{}\", ", sugg_fmt),
 930                     Applicability::MaybeIncorrect,
 931                 );
 932                 err.emit();
 933             }
 934             return DummyResult::raw_expr(sp, true);
 935         }
 936     };
 937
 938     let str_style = match fmt_style {
 939         ast::StrStyle::Cooked => None,
 940         ast::StrStyle::Raw(raw) => Some(raw as usize),
 941     };
 942
 943     let fmt_str = &fmt_str.as_str(); // for the suggestions below
 944     let fmt_snippet = ecx.source_map().span_to_snippet(fmt_sp).ok();
 945     let mut parser = parse::Parser::new(
 946         fmt_str,
 947         str_style,
 948         fmt_snippet,
 949         append_newline,
 950         parse::ParseMode::Format,
 951     );
 952
 953     let mut unverified_pieces = Vec::new();
 954     while let Some(piece) = parser.next() {
 955         if !parser.errors.is_empty() {
 956             break;
 957         } else {
 958             unverified_pieces.push(piece);
 959         }
 960     }
 961
 962     if !parser.errors.is_empty() {
 963         let err = parser.errors.remove(0);
 964         let sp = fmt_span.from_inner(err.span);
 965         let mut e = ecx.struct_span_err(sp, &format!("invalid format string: {}", err.description));
 966         e.span_label(sp, err.label + " in format string");
 967         if let Some(note) = err.note {
 968             e.note(&note);
 969         }
 970         if let Some((label, span)) = err.secondary_label {
 971             let sp = fmt_span.from_inner(span);
 972             e.span_label(sp, label);
 973         }
 974         e.emit();
 975         return DummyResult::raw_expr(sp, true);
 976     }
 977
 978     let arg_spans = parser.arg_places.iter().map(|span| fmt_span.from_inner(*span)).collect();
 979
 980     let named_pos: FxHashSet<usize> = names.values().cloned().collect();
 981
 982     let mut cx = Context {
 983         ecx,
 984         args,
 985         arg_types,
 986         arg_unique_types,
 987         names,
 988         curarg: 0,
 989         curpiece: 0,
 990         arg_index_map: Vec::new(),
 991         count_args: Vec::new(),
 992         count_positions: FxHashMap::default(),
 993         count_positions_count: 0,
 994         count_args_index_offset: 0,
 995         literal: String::new(),
 996         pieces: Vec::with_capacity(unverified_pieces.len()),
 997         str_pieces: Vec::with_capacity(unverified_pieces.len()),
 998         all_pieces_simple: true,
 999         macsp,
1000         fmtsp: fmt_span,
1001         invalid_refs: Vec::new(),
1002         arg_spans,
1003         arg_with_formatting: Vec::new(),
1004         is_literal: parser.is_literal,
1005     };
1006
1007     // This needs to happen *after* the Parser has consumed all pieces to create all the spans
1008     let pieces = unverified_pieces
1009         .into_iter()
1010         .map(|mut piece| {
1011             cx.verify_piece(&piece);
1012             cx.resolve_name_inplace(&mut piece);
1013             piece
1014         })
1015         .collect::<Vec<_>>();
1016
1017     let numbered_position_args = pieces.iter().any(|arg: &parse::Piece<'_>| match *arg {
1018         parse::String(_) => false,
1019         parse::NextArgument(arg) => match arg.position {
1020             parse::Position::ArgumentIs(_) => true,
1021             _ => false,
1022         },
1023     });
1024
1025     cx.build_index_map();
1026
1027     let mut arg_index_consumed = vec![0usize; cx.arg_index_map.len()];
1028
1029     for piece in pieces {
1030         if let Some(piece) = cx.build_piece(&piece, &mut arg_index_consumed) {
1031             let s = cx.build_literal_string();
1032             cx.str_pieces.push(s);
1033             cx.pieces.push(piece);
1034         }
1035     }
1036
1037     if !cx.literal.is_empty() {
1038         let s = cx.build_literal_string();
1039         cx.str_pieces.push(s);
1040     }
1041
1042     if !cx.invalid_refs.is_empty() {
1043         cx.report_invalid_references(numbered_position_args);
1044     }
1045
1046     // Make sure that all arguments were used and all arguments have types.
1047     let errs = cx
1048         .arg_types
1049         .iter()
1050         .enumerate()
1051         .filter(|(i, ty)| ty.is_empty() && !cx.count_positions.contains_key(&i))
1052         .map(|(i, _)| {
1053             let msg = if named_pos.contains(&i) {
1054                 // named argument
1055                 "named argument never used"
1056             } else {
1057                 // positional argument
1058                 "argument never used"
1059             };
1060             (cx.args[i].span, msg)
1061         })
1062         .collect::<Vec<_>>();
1063
1064     let errs_len = errs.len();
1065     if !errs.is_empty() {
1066         let args_used = cx.arg_types.len() - errs_len;
1067         let args_unused = errs_len;
1068
1069         let mut diag = {
1070             if errs_len == 1 {
1071                 let (sp, msg) = errs.into_iter().next().unwrap();
1072                 let mut diag = cx.ecx.struct_span_err(sp, msg);
1073                 diag.span_label(sp, msg);
1074                 diag
1075             } else {
1076                 let mut diag = cx.ecx.struct_span_err(
1077                     errs.iter().map(|&(sp, _)| sp).collect::<Vec<Span>>(),
1078                     "multiple unused formatting arguments",
1079                 );
1080                 diag.span_label(cx.fmtsp, "multiple missing formatting specifiers");
1081                 for (sp, msg) in errs {
1082                     diag.span_label(sp, msg);
1083                 }
1084                 diag
1085             }
1086         };
1087
1088         // Used to ensure we only report translations for *one* kind of foreign format.
1089         let mut found_foreign = false;
1090         // Decide if we want to look for foreign formatting directives.
1091         if args_used < args_unused {
1092             use super::format_foreign as foreign;
1093
1094             // The set of foreign substitutions we've explained.  This prevents spamming the user
1095             // with `%d should be written as {}` over and over again.
1096             let mut explained = FxHashSet::default();
1097
1098             macro_rules! check_foreign {
1099                 ($kind:ident) => {{
1100                     let mut show_doc_note = false;
1101
1102                     let mut suggestions = vec![];
1103                     // account for `"` and account for raw strings `r#`
1104                     let padding = str_style.map(|i| i + 2).unwrap_or(1);
1105                     for sub in foreign::$kind::iter_subs(fmt_str, padding) {
1106                         let trn = match sub.translate() {
1107                             Some(trn) => trn,
1108
1109                             // If it has no translation, don't call it out specifically.
1110                             None => continue,
1111                         };
1112
1113                         let pos = sub.position();
1114                         let sub = String::from(sub.as_str());
1115                         if explained.contains(&sub) {
1116                             continue;
1117                         }
1118                         explained.insert(sub.clone());
1119
1120                         if !found_foreign {
1121                             found_foreign = true;
1122                             show_doc_note = true;
1123                         }
1124
1125                         if let Some(inner_sp) = pos {
1126                             let sp = fmt_sp.from_inner(inner_sp);
1127                             suggestions.push((sp, trn));
1128                         } else {
1129                             diag.help(&format!("`{}` should be written as `{}`", sub, trn));
1130                         }
1131                     }
1132
1133                     if show_doc_note {
1134                         diag.note(concat!(
1135                             stringify!($kind),
1136                             " formatting not supported; see the documentation for `std::fmt`",
1137                         ));
1138                     }
1139                     if suggestions.len() > 0 {
1140                         diag.multipart_suggestion(
1141                             "format specifiers use curly braces",
1142                             suggestions,
1143                             Applicability::MachineApplicable,
1144                         );
1145                     }
1146                 }};
1147             }
1148
1149             check_foreign!(printf);
1150             if !found_foreign {
1151                 check_foreign!(shell);
1152             }
1153         }
1154         if !found_foreign && errs_len == 1 {
1155             diag.span_label(cx.fmtsp, "formatting specifier missing");
1156         }
1157
1158         diag.emit();
1159     }
1160
1161     cx.into_expr()
1162 }