6 use rustc_ast::tokenstream::TokenStream;
7 use rustc_ast::visit::{self, Visitor};
8 use rustc_ast::{token, BlockCheckMode, UnsafeSource};
9 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
10 use rustc_errors::{pluralize, Applicability, MultiSpan, PResult};
11 use rustc_expand::base::{self, *};
12 use rustc_parse_format as parse;
13 use rustc_span::symbol::{sym, Ident, Symbol};
14 use rustc_span::{InnerSpan, Span};
15 use smallvec::SmallVec;
18 use std::collections::hash_map::Entry;
22 Placeholder(&'static str),
29 Named(Symbol, InnerSpan),
32 struct Context<'a, 'b> {
33 ecx: &'a mut ExtCtxt<'b>,
34 /// The macro's call site. References to unstable formatting internals must
35 /// use this span to pass the stability checker.
37 /// The span of the format string literal.
40 /// List of parsed argument expressions.
41 /// Named expressions are resolved early, and are appended to the end of
42 /// argument expressions.
44 /// Example showing the various data structures in motion:
46 /// * Original: `"{foo:o} {:o} {foo:x} {0:x} {1:o} {:x} {1:x} {0:o}"`
47 /// * Implicit argument resolution: `"{foo:o} {0:o} {foo:x} {0:x} {1:o} {1:x} {1:x} {0:o}"`
48 /// * Name resolution: `"{2:o} {0:o} {2:x} {0:x} {1:o} {1:x} {1:x} {0:o}"`
49 /// * `arg_types` (in JSON): `[[0, 1, 0], [0, 1, 1], [0, 1]]`
50 /// * `arg_unique_types` (in simplified JSON): `[["o", "x"], ["o", "x"], ["o", "x"]]`
51 /// * `names` (in JSON): `{"foo": 2}`
52 args: Vec<P<ast::Expr>>,
53 /// The number of arguments that were added by implicit capturing.
54 num_captured_args: usize,
55 /// Placeholder slot numbers indexed by argument.
56 arg_types: Vec<Vec<usize>>,
57 /// Unique format specs seen for each argument.
58 arg_unique_types: Vec<Vec<ArgumentType>>,
59 /// Map from named arguments to their resolved indices.
60 names: FxHashMap<Symbol, usize>,
62 /// The latest consecutive literal strings, or empty if there weren't any.
65 /// Collection of the compiled `rt::Argument` structures
66 pieces: Vec<P<ast::Expr>>,
67 /// Collection of string literals
68 str_pieces: Vec<P<ast::Expr>>,
69 /// Stays `true` if all formatting parameters are default (as in "{}{}").
70 all_pieces_simple: bool,
72 /// Mapping between positional argument references and indices into the
73 /// final generated static argument array. We record the starting indices
74 /// corresponding to each positional argument, and number of references
75 /// consumed so far for each argument, to facilitate correct `Position`
76 /// mapping in `build_piece`. In effect this can be seen as a "flattened"
77 /// version of `arg_unique_types`.
79 /// Again with the example described above in docstring for `args`:
81 /// * `arg_index_map` (in JSON): `[[0, 1, 0], [2, 3, 3], [4, 5]]`
82 arg_index_map: Vec<Vec<usize>>,
84 /// Starting offset of count argument slots.
85 count_args_index_offset: usize,
87 /// Count argument slots and tracking data structures.
88 /// Count arguments are separately tracked for de-duplication in case
89 /// multiple references are made to one argument. For example, in this
92 /// * Original: `"{:.*} {:.foo$} {1:.*} {:.0$}"`
93 /// * Implicit argument resolution: `"{1:.0$} {2:.foo$} {1:.3$} {4:.0$}"`
94 /// * Name resolution: `"{1:.0$} {2:.5$} {1:.3$} {4:.0$}"`
95 /// * `count_positions` (in JSON): `{0: 0, 5: 1, 3: 2}`
96 /// * `count_args`: `vec![0, 5, 3]`
97 count_args: Vec<usize>,
98 /// Relative slot numbers for count arguments.
99 count_positions: FxHashMap<usize, usize>,
100 /// Number of count slots assigned.
101 count_positions_count: usize,
103 /// Current position of the implicit positional arg pointer, as if it
104 /// still existed in this phase of processing.
105 /// Used only for `all_pieces_simple` tracking in `build_piece`.
107 /// Current piece being evaluated, used for error reporting.
109 /// Keep track of invalid references to positional arguments.
110 invalid_refs: Vec<(usize, usize)>,
111 /// Spans of all the formatting arguments, in order.
112 arg_spans: Vec<Span>,
113 /// All the formatting arguments that have formatting flags set, in order for diagnostics.
114 arg_with_formatting: Vec<parse::FormatSpec<'a>>,
116 /// Whether this format string came from a string literal, as opposed to a macro.
120 /// Parses the arguments from the given list of tokens, returning the diagnostic
121 /// if there's a parse error so we can continue parsing other format!
124 /// If parsing succeeds, the return value is:
127 /// Some((fmtstr, parsed arguments, index map for named arguments))
130 ecx: &mut ExtCtxt<'a>,
133 ) -> PResult<'a, (P<ast::Expr>, Vec<P<ast::Expr>>, FxHashMap<Symbol, usize>)> {
134 let mut args = Vec::<P<ast::Expr>>::new();
135 let mut names = FxHashMap::<Symbol, usize>::default();
137 let mut p = ecx.new_parser_from_tts(tts);
139 if p.token == token::Eof {
140 return Err(ecx.struct_span_err(sp, "requires at least a format string argument"));
143 let first_token = &p.token;
144 let fmtstr = match first_token.kind {
145 token::TokenKind::Literal(token::Lit {
146 kind: token::LitKind::Str | token::LitKind::StrRaw(_),
149 // If the first token is a string literal, then a format expression
150 // is constructed from it.
152 // This allows us to properly handle cases when the first comma
153 // after the format string is mistakenly replaced with any operator,
154 // which cause the expression parser to eat too much tokens.
155 p.parse_literal_maybe_minus()?
158 // Otherwise, we fall back to the expression parser.
163 let mut first = true;
164 let mut named = false;
166 while p.token != token::Eof {
167 if !p.eat(&token::Comma) {
169 p.clear_expected_tokens();
172 match p.expect(&token::Comma) {
174 match token::TokenKind::Comma.similar_tokens() {
175 Some(tks) if tks.contains(&p.token.kind) => {
176 // If a similar token is found, then it may be a typo. We
177 // consider it as a comma, and continue parsing.
181 // Otherwise stop the parsing and return the error.
182 _ => return Err(err),
191 if p.token == token::Eof {
193 } // accept trailing commas
194 match p.token.ident() {
195 Some((ident, _)) if p.look_ahead(1, |t| *t == token::Eq) => {
198 p.expect(&token::Eq)?;
199 let e = p.parse_expr()?;
200 if let Some(prev) = names.get(&ident.name) {
201 ecx.struct_span_err(e.span, &format!("duplicate argument named `{}`", ident))
202 .span_label(args[*prev].span, "previously here")
203 .span_label(e.span, "duplicate argument")
208 // Resolve names into slots early.
209 // Since all the positional args are already seen at this point
210 // if the input is valid, we can simply append to the positional
211 // args. And remember the names.
212 let slot = args.len();
213 names.insert(ident.name, slot);
217 let e = p.parse_expr()?;
219 let mut err = ecx.struct_span_err(
221 "positional arguments cannot follow named arguments",
223 err.span_label(e.span, "positional arguments must be before named arguments");
224 for pos in names.values() {
225 err.span_label(args[*pos].span, "named argument");
233 Ok((fmtstr, args, names))
236 impl<'a, 'b> Context<'a, 'b> {
237 /// The number of arguments that were explicitly given.
238 fn num_args(&self) -> usize {
239 self.args.len() - self.num_captured_args
242 fn resolve_name_inplace(&self, p: &mut parse::Piece<'_>) {
243 // NOTE: the `unwrap_or` branch is needed in case of invalid format
244 // arguments, e.g., `format_args!("{foo}")`.
245 let lookup = |s: &str| *self.names.get(&Symbol::intern(s)).unwrap_or(&0);
248 parse::String(_) => {}
249 parse::NextArgument(ref mut arg) => {
250 if let parse::ArgumentNamed(s, _) = arg.position {
251 arg.position = parse::ArgumentIs(lookup(s));
253 if let parse::CountIsName(s, _) = arg.format.width {
254 arg.format.width = parse::CountIsParam(lookup(s));
256 if let parse::CountIsName(s, _) = arg.format.precision {
257 arg.format.precision = parse::CountIsParam(lookup(s));
263 /// Verifies one piece of a parse string, and remembers it if valid.
264 /// All errors are not emitted as fatal so we can continue giving errors
265 /// about this and possibly other format strings.
266 fn verify_piece(&mut self, p: &parse::Piece<'_>) {
268 parse::String(..) => {}
269 parse::NextArgument(ref arg) => {
270 // width/precision first, if they have implicit positional
271 // parameters it makes more sense to consume them first.
272 self.verify_count(arg.format.width);
273 self.verify_count(arg.format.precision);
275 // argument second, if it's an implicit positional parameter
276 // it's written second, so it should come after width/precision.
277 let pos = match arg.position {
278 parse::ArgumentIs(i) | parse::ArgumentImplicitlyIs(i) => Exact(i),
279 parse::ArgumentNamed(s, span) => {
280 Named(Symbol::intern(s), InnerSpan::new(span.start, span.end))
284 let ty = Placeholder(match arg.format.ty {
295 let fmtsp = self.fmtsp;
299 .map(|sp| fmtsp.from_inner(InnerSpan::new(sp.start, sp.end)));
300 let mut err = self.ecx.struct_span_err(
302 &format!("unknown format trait `{}`", arg.format.ty),
305 "the only appropriate formatting traits are:\n\
306 - ``, which uses the `Display` trait\n\
307 - `?`, which uses the `Debug` trait\n\
308 - `e`, which uses the `LowerExp` trait\n\
309 - `E`, which uses the `UpperExp` trait\n\
310 - `o`, which uses the `Octal` trait\n\
311 - `p`, which uses the `Pointer` trait\n\
312 - `b`, which uses the `Binary` trait\n\
313 - `x`, which uses the `LowerHex` trait\n\
314 - `X`, which uses the `UpperHex` trait",
316 if let Some(sp) = sp {
317 for (fmt, name) in &[
328 // FIXME: rustfix (`run-rustfix`) fails to apply suggestions.
329 // > "Cannot replace slice of data that was already replaced"
330 err.tool_only_span_suggestion(
332 &format!("use the `{}` trait", name),
334 Applicability::MaybeIncorrect,
342 self.verify_arg_type(pos, ty);
348 fn verify_count(&mut self, c: parse::Count<'_>) {
350 parse::CountImplied | parse::CountIs(..) => {}
351 parse::CountIsParam(i) => {
352 self.verify_arg_type(Exact(i), Count);
354 parse::CountIsName(s, span) => {
355 self.verify_arg_type(
356 Named(Symbol::intern(s), InnerSpan::new(span.start, span.end)),
363 fn describe_num_args(&self) -> Cow<'_, str> {
364 match self.num_args() {
365 0 => "no arguments were given".into(),
366 1 => "there is 1 argument".into(),
367 x => format!("there are {} arguments", x).into(),
371 /// Handle invalid references to positional arguments. Output different
372 /// errors for the case where all arguments are positional and for when
373 /// there are named arguments or numbered positional arguments in the
375 fn report_invalid_references(&self, numbered_position_args: bool) {
377 let sp = if !self.arg_spans.is_empty() {
378 // Point at the formatting arguments.
379 MultiSpan::from_spans(self.arg_spans.clone())
381 MultiSpan::from_span(self.fmtsp)
384 self.invalid_refs.iter().map(|(r, pos)| (r.to_string(), self.arg_spans.get(*pos)));
386 let mut zero_based_note = false;
388 let count = self.pieces.len()
389 + self.arg_with_formatting.iter().filter(|fmt| fmt.precision_span.is_some()).count();
390 if self.names.is_empty() && !numbered_position_args && count != self.num_args() {
391 e = self.ecx.struct_span_err(
394 "{} positional argument{} in format string, but {}",
397 self.describe_num_args(),
400 for arg in &self.args {
401 // Point at the arguments that will be formatted.
402 e.span_label(arg.span, "");
405 let (mut refs, spans): (Vec<_>, Vec<_>) = refs.unzip();
406 // Avoid `invalid reference to positional arguments 7 and 7 (there is 1 argument)`
407 // for `println!("{7:7$}", 1);`
410 let spans: Vec<_> = spans.into_iter().filter_map(|sp| sp.copied()).collect();
411 let sp = if self.arg_spans.is_empty() || spans.is_empty() {
412 MultiSpan::from_span(self.fmtsp)
414 MultiSpan::from_spans(spans)
416 let arg_list = if refs.len() == 1 {
417 format!("argument {}", refs[0])
419 let reg = refs.pop().unwrap();
420 format!("arguments {head} and {tail}", head = refs.join(", "), tail = reg)
423 e = self.ecx.struct_span_err(
426 "invalid reference to positional {} ({})",
428 self.describe_num_args()
431 zero_based_note = true;
434 for fmt in &self.arg_with_formatting {
435 if let Some(span) = fmt.precision_span {
436 let span = self.fmtsp.from_inner(InnerSpan::new(span.start, span.end));
437 match fmt.precision {
438 parse::CountIsParam(pos) if pos > self.num_args() => {
442 "this precision flag expects an `usize` argument at position {}, \
445 self.describe_num_args(),
448 zero_based_note = true;
450 parse::CountIsParam(pos) => {
451 let count = self.pieces.len()
455 .filter(|fmt| fmt.precision_span.is_some())
460 "this precision flag adds an extra required argument at position {}, \
461 which is why there {} expected",
464 "is 1 argument".to_string()
466 format!("are {} arguments", count)
470 if let Some(arg) = self.args.get(pos) {
473 "this parameter corresponds to the precision flag",
476 zero_based_note = true;
481 if let Some(span) = fmt.width_span {
482 let span = self.fmtsp.from_inner(InnerSpan::new(span.start, span.end));
484 parse::CountIsParam(pos) if pos > self.num_args() => {
488 "this width flag expects an `usize` argument at position {}, \
491 self.describe_num_args(),
494 zero_based_note = true;
501 e.note("positional arguments are zero-based");
503 if !self.arg_with_formatting.is_empty() {
505 "for information about formatting flags, visit \
506 https://doc.rust-lang.org/std/fmt/index.html",
513 /// Actually verifies and tracks a given format placeholder
514 /// (a.k.a. argument).
515 fn verify_arg_type(&mut self, arg: Position, ty: ArgumentType) {
516 if let Exact(arg) = arg {
517 if arg >= self.num_args() {
518 self.invalid_refs.push((arg, self.curpiece));
524 Exact(arg) | Capture(arg) => {
527 // record every (position, type) combination only once
528 let seen_ty = &mut self.arg_unique_types[arg];
529 let i = seen_ty.iter().position(|x| *x == ty).unwrap_or_else(|| {
530 let i = seen_ty.len();
534 self.arg_types[arg].push(i);
537 if let Entry::Vacant(e) = self.count_positions.entry(arg) {
538 let i = self.count_positions_count;
540 self.count_args.push(arg);
541 self.count_positions_count += 1;
547 Named(name, span) => {
548 match self.names.get(&name) {
550 // Treat as positional arg.
551 self.verify_arg_type(Capture(idx), ty)
554 // For the moment capturing variables from format strings expanded from macros is
555 // disabled (see RFC #2795)
557 // Treat this name as a variable to capture from the surrounding scope
558 let idx = self.args.len();
559 self.arg_types.push(Vec::new());
560 self.arg_unique_types.push(Vec::new());
561 let span = if self.is_literal {
562 self.fmtsp.from_inner(span)
566 self.num_captured_args += 1;
567 self.args.push(self.ecx.expr_ident(span, Ident::new(name, span)));
568 self.names.insert(name, idx);
569 self.verify_arg_type(Capture(idx), ty)
571 let msg = format!("there is no argument named `{}`", name);
572 let sp = if self.is_literal {
573 self.fmtsp.from_inner(span)
577 let mut err = self.ecx.struct_span_err(sp, &msg);
580 "did you intend to capture a variable `{}` from \
581 the surrounding scope?",
585 "to avoid ambiguity, `format_args!` cannot capture variables \
586 when the format string is expanded from a macro",
597 /// Builds the mapping between format placeholders and argument objects.
598 fn build_index_map(&mut self) {
599 // NOTE: Keep the ordering the same as `into_expr`'s expansion would do!
600 let args_len = self.args.len();
601 self.arg_index_map.reserve(args_len);
603 let mut sofar = 0usize;
606 for i in 0..args_len {
607 let arg_types = &self.arg_types[i];
608 let arg_offsets = arg_types.iter().map(|offset| sofar + *offset).collect::<Vec<_>>();
609 self.arg_index_map.push(arg_offsets);
610 sofar += self.arg_unique_types[i].len();
613 // Record starting index for counts, which appear just after arguments
614 self.count_args_index_offset = sofar;
617 fn rtpath(ecx: &ExtCtxt<'_>, s: Symbol) -> Vec<Ident> {
618 ecx.std_path(&[sym::fmt, sym::rt, sym::v1, s])
621 fn build_count(&self, c: parse::Count<'_>) -> P<ast::Expr> {
623 let count = |c, arg| {
624 let mut path = Context::rtpath(self.ecx, sym::Count);
625 path.push(Ident::new(c, sp));
627 Some(arg) => self.ecx.expr_call_global(sp, path, vec![arg]),
628 None => self.ecx.expr_path(self.ecx.path_global(sp, path)),
632 parse::CountIs(i) => count(sym::Is, Some(self.ecx.expr_usize(sp, i))),
633 parse::CountIsParam(i) => {
634 // This needs mapping too, as `i` is referring to a macro
635 // argument. If `i` is not found in `count_positions` then
636 // the error had already been emitted elsewhere.
637 let i = self.count_positions.get(&i).cloned().unwrap_or(0)
638 + self.count_args_index_offset;
639 count(sym::Param, Some(self.ecx.expr_usize(sp, i)))
641 parse::CountImplied => count(sym::Implied, None),
642 // should never be the case, names are already resolved
643 parse::CountIsName(..) => panic!("should never happen"),
647 /// Build a literal expression from the accumulated string literals
648 fn build_literal_string(&mut self) -> P<ast::Expr> {
650 let s = Symbol::intern(&self.literal);
651 self.literal.clear();
652 self.ecx.expr_str(sp, s)
655 /// Builds a static `rt::Argument` from a `parse::Piece` or append
656 /// to the `literal` string.
659 piece: &parse::Piece<'a>,
660 arg_index_consumed: &mut Vec<usize>,
661 ) -> Option<P<ast::Expr>> {
664 parse::String(s) => {
665 self.literal.push_str(s);
668 parse::NextArgument(ref arg) => {
669 // Build the position
672 parse::ArgumentIs(i) | parse::ArgumentImplicitlyIs(i) => {
673 // Map to index in final generated argument array
674 // in case of multiple types specified
675 let arg_idx = match arg_index_consumed.get_mut(i) {
676 None => 0, // error already emitted elsewhere
678 let idx_map = &self.arg_index_map[i];
679 // unwrap_or branch: error already emitted elsewhere
680 let arg_idx = *idx_map.get(*offset).unwrap_or(&0);
685 self.ecx.expr_usize(sp, arg_idx)
688 // should never be the case, because names are already
690 parse::ArgumentNamed(..) => panic!("should never happen"),
694 let simple_arg = parse::Argument {
696 // We don't have ArgumentNext any more, so we have to
697 // track the current argument ourselves.
702 format: parse::FormatSpec {
703 fill: arg.format.fill,
704 align: parse::AlignUnknown,
706 precision: parse::CountImplied,
707 precision_span: None,
708 width: parse::CountImplied,
711 ty_span: arg.format.ty_span,
715 let fill = arg.format.fill.unwrap_or(' ');
717 let pos_simple = arg.position.index() == simple_arg.position.index();
719 if arg.format.precision_span.is_some() || arg.format.width_span.is_some() {
720 self.arg_with_formatting.push(arg.format);
722 if !pos_simple || arg.format != simple_arg.format || fill != ' ' {
723 self.all_pieces_simple = false;
727 let fill = self.ecx.expr_lit(sp, ast::LitKind::Char(fill));
729 let mut p = Context::rtpath(self.ecx, sym::Alignment);
730 p.push(Ident::new(name, sp));
731 self.ecx.path_global(sp, p)
733 let align = match arg.format.align {
734 parse::AlignLeft => align(sym::Left),
735 parse::AlignRight => align(sym::Right),
736 parse::AlignCenter => align(sym::Center),
737 parse::AlignUnknown => align(sym::Unknown),
739 let align = self.ecx.expr_path(align);
740 let flags = self.ecx.expr_u32(sp, arg.format.flags);
741 let prec = self.build_count(arg.format.precision);
742 let width = self.build_count(arg.format.width);
743 let path = self.ecx.path_global(sp, Context::rtpath(self.ecx, sym::FormatSpec));
744 let fmt = self.ecx.expr_struct(
748 self.ecx.field_imm(sp, Ident::new(sym::fill, sp), fill),
749 self.ecx.field_imm(sp, Ident::new(sym::align, sp), align),
750 self.ecx.field_imm(sp, Ident::new(sym::flags, sp), flags),
751 self.ecx.field_imm(sp, Ident::new(sym::precision, sp), prec),
752 self.ecx.field_imm(sp, Ident::new(sym::width, sp), width),
756 let path = self.ecx.path_global(sp, Context::rtpath(self.ecx, sym::Argument));
757 Some(self.ecx.expr_struct(
761 self.ecx.field_imm(sp, Ident::new(sym::position, sp), pos),
762 self.ecx.field_imm(sp, Ident::new(sym::format, sp), fmt),
769 /// Actually builds the expression which the format_args! block will be
771 fn into_expr(self) -> P<ast::Expr> {
772 let mut original_args = self.args;
773 let mut fmt_args = Vec::with_capacity(
774 self.arg_unique_types.iter().map(|v| v.len()).sum::<usize>() + self.count_args.len(),
777 // First, build up the static array which will become our precompiled
779 let pieces = self.ecx.expr_array_ref(self.fmtsp, self.str_pieces);
781 // We need to construct a &[ArgumentV1] to pass into the fmt::Arguments
782 // constructor. In general the expressions in this slice might be
783 // permuted from their order in original_args (such as in the case of
784 // "{1} {0}"), or may have multiple entries referring to the same
785 // element of original_args ("{0} {0}").
787 // The following vector has one item per element of our output slice,
788 // identifying the index of which element of original_args it's passing,
789 // and that argument's type.
790 let mut fmt_arg_index_and_ty = SmallVec::<[(usize, &ArgumentType); 8]>::new();
791 for (i, unique_types) in self.arg_unique_types.iter().enumerate() {
792 fmt_arg_index_and_ty.extend(unique_types.iter().map(|ty| (i, ty)));
794 fmt_arg_index_and_ty.extend(self.count_args.iter().map(|&i| (i, &Count)));
796 // Figure out whether there are permuted or repeated elements. If not,
797 // we can generate simpler code.
799 // The sequence has no indices out of order or repeated if: for every
800 // adjacent pair of elements, the first one's index is less than the
801 // second one's index.
803 fmt_arg_index_and_ty.array_windows().all(|[(i, _i_ty), (j, _j_ty)]| i < j);
807 // [ArgumentV1::new(&$arg0, …), ArgumentV1::new(&$arg1, …), …]
809 // However, it's only legal to do so if $arg0, $arg1, … were written in
810 // exactly that order by the programmer. When arguments are permuted, we
811 // want them evaluated in the order written by the programmer, not in
812 // the order provided to fmt::Arguments. When arguments are repeated, we
813 // want the expression evaluated only once.
815 // Further, if any arg _after the first one_ contains a yield point such
816 // as `await` or `yield`, the above short form is inconvenient for the
817 // caller because it would keep a temporary of type ArgumentV1 alive
818 // across the yield point. ArgumentV1 can't implement Send since it
819 // holds a type-erased arbitrary type.
821 // Thus in the not nicely ordered case, and in the yielding case, we
822 // emit the following instead:
824 // match (&$arg0, &$arg1, …) {
825 // args => [ArgumentV1::new(args.$i, …), ArgumentV1::new(args.$j, …), …]
828 // for the sequence of indices $i, $j, … governed by fmt_arg_index_and_ty.
829 // This more verbose representation ensures that all arguments are
830 // evaluated a single time each, in the order written by the programmer,
831 // and that the surrounding future/generator (if any) is Send whenever
833 let no_need_for_match =
834 nicely_ordered && !original_args.iter().skip(1).any(|e| may_contain_yield_point(e));
836 for (arg_index, arg_ty) in fmt_arg_index_and_ty {
837 let e = &mut original_args[arg_index];
839 let arg = if no_need_for_match {
840 let expansion_span = e.span.with_ctxt(self.macsp.ctxt());
841 // The indices are strictly ordered so e has not been taken yet.
842 self.ecx.expr_addr_of(expansion_span, P(e.take()))
844 let def_site = self.ecx.with_def_site_ctxt(span);
845 let args_tuple = self.ecx.expr_ident(def_site, Ident::new(sym::args, def_site));
846 let member = Ident::new(sym::integer(arg_index), def_site);
847 self.ecx.expr(def_site, ast::ExprKind::Field(args_tuple, member))
849 fmt_args.push(Context::format_arg(self.ecx, self.macsp, span, arg_ty, arg));
852 let args_array = self.ecx.expr_array(self.macsp, fmt_args);
853 let args_slice = self.ecx.expr_addr_of(
855 if no_need_for_match {
858 // In the !no_need_for_match case, none of the exprs were moved
859 // away in the previous loop.
861 // This uses the arg span for `&arg` so that borrowck errors
862 // point to the specific expression passed to the macro (the
863 // span is otherwise unavailable in the MIR used by borrowck).
864 let heads = original_args
866 .map(|e| self.ecx.expr_addr_of(e.span.with_ctxt(self.macsp.ctxt()), e))
869 let pat = self.ecx.pat_ident(self.macsp, Ident::new(sym::args, self.macsp));
870 let arm = self.ecx.arm(self.macsp, pat, args_array);
871 let head = self.ecx.expr(self.macsp, ast::ExprKind::Tup(heads));
872 self.ecx.expr_match(self.macsp, head, vec![arm])
876 // Now create the fmt::Arguments struct with all our locals we created.
877 let (fn_name, fn_args) = if self.all_pieces_simple {
878 ("new_v1", vec![pieces, args_slice])
880 // Build up the static array which will store our precompiled
881 // nonstandard placeholders, if there are any.
882 let fmt = self.ecx.expr_array_ref(self.macsp, self.pieces);
884 let path = self.ecx.std_path(&[sym::fmt, sym::UnsafeArg, sym::new]);
885 let unsafe_arg = self.ecx.expr_call_global(self.macsp, path, Vec::new());
886 let unsafe_expr = self.ecx.expr_block(P(ast::Block {
887 stmts: vec![self.ecx.stmt_expr(unsafe_arg)],
888 id: ast::DUMMY_NODE_ID,
889 rules: BlockCheckMode::Unsafe(UnsafeSource::CompilerGenerated),
892 could_be_bare_literal: false,
895 ("new_v1_formatted", vec![pieces, args_slice, fmt, unsafe_expr])
898 let path = self.ecx.std_path(&[sym::fmt, sym::Arguments, Symbol::intern(fn_name)]);
899 self.ecx.expr_call_global(self.macsp, path, fn_args)
909 sp = ecx.with_def_site_ctxt(sp);
910 let trait_ = match *ty {
911 Placeholder(trait_) if trait_ == "<invalid>" => return DummyResult::raw_expr(sp, true),
912 Placeholder(trait_) => trait_,
914 let path = ecx.std_path(&[sym::fmt, sym::ArgumentV1, sym::from_usize]);
915 return ecx.expr_call_global(macsp, path, vec![arg]);
918 let new_fn_name = match trait_ {
919 "Display" => "new_display",
920 "Debug" => "new_debug",
921 "LowerExp" => "new_lower_exp",
922 "UpperExp" => "new_upper_exp",
923 "Octal" => "new_octal",
924 "Pointer" => "new_pointer",
925 "Binary" => "new_binary",
926 "LowerHex" => "new_lower_hex",
927 "UpperHex" => "new_upper_hex",
931 let path = ecx.std_path(&[sym::fmt, sym::ArgumentV1, Symbol::intern(new_fn_name)]);
932 ecx.expr_call_global(sp, path, vec![arg])
936 fn expand_format_args_impl<'cx>(
937 ecx: &'cx mut ExtCtxt<'_>,
941 ) -> Box<dyn base::MacResult + 'cx> {
942 sp = ecx.with_def_site_ctxt(sp);
943 match parse_args(ecx, sp, tts) {
944 Ok((efmt, args, names)) => {
945 MacEager::expr(expand_preparsed_format_args(ecx, sp, efmt, args, names, nl))
954 pub fn expand_format_args<'cx>(
955 ecx: &'cx mut ExtCtxt<'_>,
958 ) -> Box<dyn base::MacResult + 'cx> {
959 expand_format_args_impl(ecx, sp, tts, false)
962 pub fn expand_format_args_nl<'cx>(
963 ecx: &'cx mut ExtCtxt<'_>,
966 ) -> Box<dyn base::MacResult + 'cx> {
967 expand_format_args_impl(ecx, sp, tts, true)
970 /// Take the various parts of `format_args!(efmt, args..., name=names...)`
971 /// and construct the appropriate formatting expression.
972 pub fn expand_preparsed_format_args(
973 ecx: &mut ExtCtxt<'_>,
976 args: Vec<P<ast::Expr>>,
977 names: FxHashMap<Symbol, usize>,
978 append_newline: bool,
980 // NOTE: this verbose way of initializing `Vec<Vec<ArgumentType>>` is because
981 // `ArgumentType` does not derive `Clone`.
982 let arg_types: Vec<_> = (0..args.len()).map(|_| Vec::new()).collect();
983 let arg_unique_types: Vec<_> = (0..args.len()).map(|_| Vec::new()).collect();
985 let mut macsp = ecx.call_site();
986 macsp = ecx.with_def_site_ctxt(macsp);
988 let msg = "format argument must be a string literal";
989 let fmt_sp = efmt.span;
990 let efmt_kind_is_lit: bool = matches!(efmt.kind, ast::ExprKind::Lit(_));
991 let (fmt_str, fmt_style, fmt_span) = match expr_to_spanned_string(ecx, efmt, msg) {
992 Ok(mut fmt) if append_newline => {
993 fmt.0 = Symbol::intern(&format!("{}\n", fmt.0));
998 if let Some((mut err, suggested)) = err {
999 let sugg_fmt = match args.len() {
1000 0 => "{}".to_string(),
1001 _ => format!("{}{{}}", "{} ".repeat(args.len())),
1004 err.span_suggestion(
1005 fmt_sp.shrink_to_lo(),
1006 "you might be missing a string literal to format with",
1007 format!("\"{}\", ", sugg_fmt),
1008 Applicability::MaybeIncorrect,
1013 return DummyResult::raw_expr(sp, true);
1017 let str_style = match fmt_style {
1018 ast::StrStyle::Cooked => None,
1019 ast::StrStyle::Raw(raw) => Some(raw as usize),
1022 let fmt_str = fmt_str.as_str(); // for the suggestions below
1023 let fmt_snippet = ecx.source_map().span_to_snippet(fmt_sp).ok();
1024 let mut parser = parse::Parser::new(
1029 parse::ParseMode::Format,
1032 let mut unverified_pieces = Vec::new();
1033 while let Some(piece) = parser.next() {
1034 if !parser.errors.is_empty() {
1037 unverified_pieces.push(piece);
1041 if !parser.errors.is_empty() {
1042 let err = parser.errors.remove(0);
1043 let sp = if efmt_kind_is_lit {
1044 fmt_span.from_inner(InnerSpan::new(err.span.start, err.span.end))
1046 // The format string could be another macro invocation, e.g.:
1047 // format!(concat!("abc", "{}"), 4);
1048 // However, `err.span` is an inner span relative to the *result* of
1049 // the macro invocation, which is why we would get a nonsensical
1050 // result calling `fmt_span.from_inner(err.span)` as above, and
1051 // might even end up inside a multibyte character (issue #86085).
1052 // Therefore, we conservatively report the error for the entire
1053 // argument span here.
1056 let mut e = ecx.struct_span_err(sp, &format!("invalid format string: {}", err.description));
1057 e.span_label(sp, err.label + " in format string");
1058 if let Some(note) = err.note {
1061 if let Some((label, span)) = err.secondary_label {
1062 if efmt_kind_is_lit {
1063 e.span_label(fmt_span.from_inner(InnerSpan::new(span.start, span.end)), label);
1067 return DummyResult::raw_expr(sp, true);
1070 let arg_spans = parser
1073 .map(|span| fmt_span.from_inner(InnerSpan::new(span.start, span.end)))
1076 let named_pos: FxHashSet<usize> = names.values().cloned().collect();
1078 let mut cx = Context {
1081 num_captured_args: 0,
1087 arg_index_map: Vec::new(),
1088 count_args: Vec::new(),
1089 count_positions: FxHashMap::default(),
1090 count_positions_count: 0,
1091 count_args_index_offset: 0,
1092 literal: String::new(),
1093 pieces: Vec::with_capacity(unverified_pieces.len()),
1094 str_pieces: Vec::with_capacity(unverified_pieces.len()),
1095 all_pieces_simple: true,
1098 invalid_refs: Vec::new(),
1100 arg_with_formatting: Vec::new(),
1101 is_literal: parser.is_literal,
1104 // This needs to happen *after* the Parser has consumed all pieces to create all the spans
1105 let pieces = unverified_pieces
1108 cx.verify_piece(&piece);
1109 cx.resolve_name_inplace(&mut piece);
1112 .collect::<Vec<_>>();
1114 let numbered_position_args = pieces.iter().any(|arg: &parse::Piece<'_>| match *arg {
1115 parse::String(_) => false,
1116 parse::NextArgument(arg) => matches!(arg.position, parse::Position::ArgumentIs(_)),
1119 cx.build_index_map();
1121 let mut arg_index_consumed = vec![0usize; cx.arg_index_map.len()];
1123 for piece in pieces {
1124 if let Some(piece) = cx.build_piece(&piece, &mut arg_index_consumed) {
1125 let s = cx.build_literal_string();
1126 cx.str_pieces.push(s);
1127 cx.pieces.push(piece);
1131 if !cx.literal.is_empty() {
1132 let s = cx.build_literal_string();
1133 cx.str_pieces.push(s);
1136 if !cx.invalid_refs.is_empty() {
1137 cx.report_invalid_references(numbered_position_args);
1140 // Make sure that all arguments were used and all arguments have types.
1145 .filter(|(i, ty)| ty.is_empty() && !cx.count_positions.contains_key(&i))
1147 let msg = if named_pos.contains(&i) {
1149 "named argument never used"
1151 // positional argument
1152 "argument never used"
1154 (cx.args[i].span, msg)
1156 .collect::<Vec<_>>();
1158 let errs_len = errs.len();
1159 if !errs.is_empty() {
1160 let args_used = cx.arg_types.len() - errs_len;
1161 let args_unused = errs_len;
1164 if let [(sp, msg)] = &errs[..] {
1165 let mut diag = cx.ecx.struct_span_err(*sp, *msg);
1166 diag.span_label(*sp, *msg);
1169 let mut diag = cx.ecx.struct_span_err(
1170 errs.iter().map(|&(sp, _)| sp).collect::<Vec<Span>>(),
1171 "multiple unused formatting arguments",
1173 diag.span_label(cx.fmtsp, "multiple missing formatting specifiers");
1174 for (sp, msg) in errs {
1175 diag.span_label(sp, msg);
1181 // Used to ensure we only report translations for *one* kind of foreign format.
1182 let mut found_foreign = false;
1183 // Decide if we want to look for foreign formatting directives.
1184 if args_used < args_unused {
1185 use super::format_foreign as foreign;
1187 // The set of foreign substitutions we've explained. This prevents spamming the user
1188 // with `%d should be written as {}` over and over again.
1189 let mut explained = FxHashSet::default();
1191 macro_rules! check_foreign {
1193 let mut show_doc_note = false;
1195 let mut suggestions = vec![];
1196 // account for `"` and account for raw strings `r#`
1197 let padding = str_style.map(|i| i + 2).unwrap_or(1);
1198 for sub in foreign::$kind::iter_subs(fmt_str, padding) {
1199 let (trn, success) = match sub.translate() {
1200 Ok(trn) => (trn, true),
1201 Err(Some(msg)) => (msg, false),
1203 // If it has no translation, don't call it out specifically.
1207 let pos = sub.position();
1208 let sub = String::from(sub.as_str());
1209 if explained.contains(&sub) {
1212 explained.insert(sub.clone());
1215 found_foreign = true;
1216 show_doc_note = true;
1219 if let Some(inner_sp) = pos {
1220 let sp = fmt_sp.from_inner(inner_sp);
1223 suggestions.push((sp, trn));
1227 &format!("format specifiers use curly braces, and {}", trn),
1232 diag.help(&format!("`{}` should be written as `{}`", sub, trn));
1235 "`{}` should use curly braces, and {}",
1245 " formatting not supported; see the documentation for `std::fmt`",
1248 if suggestions.len() > 0 {
1249 diag.multipart_suggestion(
1250 "format specifiers use curly braces",
1252 Applicability::MachineApplicable,
1258 check_foreign!(printf);
1260 check_foreign!(shell);
1263 if !found_foreign && errs_len == 1 {
1264 diag.span_label(cx.fmtsp, "formatting specifier missing");
1273 fn may_contain_yield_point(e: &ast::Expr) -> bool {
1274 struct MayContainYieldPoint(bool);
1276 impl Visitor<'_> for MayContainYieldPoint {
1277 fn visit_expr(&mut self, e: &ast::Expr) {
1278 if let ast::ExprKind::Await(_) | ast::ExprKind::Yield(_) = e.kind {
1281 visit::walk_expr(self, e);
1285 fn visit_mac_call(&mut self, _: &ast::MacCall) {
1289 fn visit_attribute(&mut self, _: &ast::Attribute) {
1290 // Conservatively assume this may be a proc macro attribute in
1291 // expression position.
1295 fn visit_item(&mut self, _: &ast::Item) {
1296 // Do not recurse into nested items.
1300 let mut visitor = MayContainYieldPoint(false);
1301 visitor.visit_expr(e);