use ArgumentType::*; use Position::*; use rustc_ast as ast; use rustc_ast::ptr::P; use rustc_ast::tokenstream::TokenStream; use rustc_ast::visit::{self, Visitor}; use rustc_ast::{token, BlockCheckMode, UnsafeSource}; use rustc_data_structures::fx::{FxHashMap, FxHashSet}; use rustc_errors::{pluralize, Applicability, MultiSpan, PResult}; use rustc_expand::base::{self, *}; use rustc_parse_format as parse; use rustc_span::symbol::{sym, Ident, Symbol}; use rustc_span::{BytePos, InnerSpan, Span}; use smallvec::SmallVec; use rustc_lint_defs::builtin::NAMED_ARGUMENTS_USED_POSITIONALLY; use rustc_lint_defs::{BufferedEarlyLint, BuiltinLintDiagnostics, LintId}; use rustc_parse_format::Count; use std::borrow::Cow; use std::collections::hash_map::Entry; #[derive(PartialEq)] enum ArgumentType { Placeholder(&'static str), Count, } enum Position { Exact(usize), Capture(usize), Named(Symbol, InnerSpan), } /// Indicates how positional named argument (i.e. an named argument which is used by position /// instead of by name) is used in format string /// * `Arg` is the actual argument to print /// * `Width` is width format argument /// * `Precision` is precion format argument /// Example: `{Arg:Width$.Precision$} #[derive(Debug, Eq, PartialEq)] enum PositionalNamedArgType { Arg, Width, Precision, } /// Contains information necessary to create a lint for a positional named argument #[derive(Debug)] struct PositionalNamedArg { ty: PositionalNamedArgType, /// The piece of the using this argument (multiple pieces can use the same argument) cur_piece: usize, /// The InnerSpan for in the string to be replaced with the named argument /// This will be None when the position is implicit inner_span_to_replace: Option, /// The name to use instead of the position replacement: Symbol, /// The span for the positional named argument (so the lint can point a message to it) positional_named_arg_span: Span, has_formatting: bool, } impl PositionalNamedArg { /// Determines: /// 1) span to be replaced with the name of the named argument and /// 2) span to be underlined for error messages fn get_positional_arg_spans(&self, cx: &Context<'_, '_>) -> (Option, Option) { if let Some(inner_span) = &self.inner_span_to_replace { let span = cx.fmtsp.from_inner(InnerSpan { start: inner_span.start, end: inner_span.end }); (Some(span), Some(span)) } else if self.ty == PositionalNamedArgType::Arg { // In the case of a named argument whose position is implicit, if the argument *has* // formatting, there will not be a span to replace. Instead, we insert the name after // the `{`, which will be the first character of arg_span. If the argument does *not* // have formatting, there may or may not be a span to replace. This is because // whitespace is allowed in arguments without formatting (such as `format!("{ }", 1);`) // but is not allowed in arguments with formatting (an error will be generated in cases // like `format!("{ :1.1}", 1.0f32);`. // For the message span, if there is formatting, we want to use the opening `{` and the // next character, which will the `:` indicating the start of formatting. If there is // not any formatting, we want to underline the entire span. cx.arg_spans.get(self.cur_piece).map_or((None, None), |arg_span| { if self.has_formatting { ( Some(arg_span.with_lo(arg_span.lo() + BytePos(1)).shrink_to_lo()), Some(arg_span.with_hi(arg_span.lo() + BytePos(2))), ) } else { let replace_start = arg_span.lo() + BytePos(1); let replace_end = arg_span.hi() - BytePos(1); let to_replace = arg_span.with_lo(replace_start).with_hi(replace_end); (Some(to_replace), Some(*arg_span)) } }) } else { (None, None) } } } /// Encapsulates all the named arguments that have been used positionally #[derive(Debug)] struct PositionalNamedArgsLint { positional_named_args: Vec, } impl PositionalNamedArgsLint { /// For a given positional argument, check if the index is for a named argument. /// /// Since positional arguments are required to come before named arguments, if the positional /// index is greater than or equal to the start of named arguments, we know it's a named /// argument used positionally. /// /// Example: /// println!("{} {} {2}", 0, a=1, b=2); /// /// In this case, the first piece (`{}`) would be ArgumentImplicitlyIs with an index of 0. The /// total number of arguments is 3 and the number of named arguments is 2, so the start of named /// arguments is index 1. Therefore, the index of 0 is okay. /// /// The second piece (`{}`) would be ArgumentImplicitlyIs with an index of 1, which is the start /// of named arguments, and so we should add a lint to use the named argument `a`. /// /// The third piece (`{2}`) would be ArgumentIs with an index of 2, which is greater than the /// start of named arguments, and so we should add a lint to use the named argument `b`. /// /// This same check also works for width and precision formatting when either or both are /// CountIsParam, which contains an index into the arguments. fn maybe_add_positional_named_arg( &mut self, arg: Option<&FormatArg>, ty: PositionalNamedArgType, cur_piece: usize, inner_span_to_replace: Option, has_formatting: bool, ) { if let Some(arg) = arg { if let Some(name) = arg.name { self.push(name, ty, cur_piece, inner_span_to_replace, has_formatting) } } } /// Construct a PositionalNamedArg struct and push it into the vec of positional /// named arguments. fn push( &mut self, arg_name: Ident, ty: PositionalNamedArgType, cur_piece: usize, inner_span_to_replace: Option, has_formatting: bool, ) { // In FormatSpec, `precision_span` starts at the leading `.`, which we want to keep in // the lint suggestion, so increment `start` by 1 when `PositionalArgumentType` is // `Precision`. let inner_span_to_replace = if ty == PositionalNamedArgType::Precision { inner_span_to_replace .map(|is| rustc_parse_format::InnerSpan { start: is.start + 1, end: is.end }) } else { inner_span_to_replace }; self.positional_named_args.push(PositionalNamedArg { ty, cur_piece, inner_span_to_replace, replacement: arg_name.name, positional_named_arg_span: arg_name.span, has_formatting, }); } } struct Context<'a, 'b> { ecx: &'a mut ExtCtxt<'b>, /// The macro's call site. References to unstable formatting internals must /// use this span to pass the stability checker. macsp: Span, /// The span of the format string literal. fmtsp: Span, /// List of parsed argument expressions. /// Named expressions are resolved early, and are appended to the end of /// argument expressions. /// /// Example showing the various data structures in motion: /// /// * Original: `"{foo:o} {:o} {foo:x} {0:x} {1:o} {:x} {1:x} {0:o}"` /// * Implicit argument resolution: `"{foo:o} {0:o} {foo:x} {0:x} {1:o} {1:x} {1:x} {0:o}"` /// * Name resolution: `"{2:o} {0:o} {2:x} {0:x} {1:o} {1:x} {1:x} {0:o}"` /// * `arg_types` (in JSON): `[[0, 1, 0], [0, 1, 1], [0, 1]]` /// * `arg_unique_types` (in simplified JSON): `[["o", "x"], ["o", "x"], ["o", "x"]]` /// * `names` (in JSON): `{"foo": 2}` args: Vec, /// The number of arguments that were added by implicit capturing. num_captured_args: usize, /// Placeholder slot numbers indexed by argument. arg_types: Vec>, /// Unique format specs seen for each argument. arg_unique_types: Vec>, /// Map from named arguments to their resolved indices. names: FxHashMap, /// The latest consecutive literal strings, or empty if there weren't any. literal: String, /// Collection of the compiled `rt::Argument` structures pieces: Vec>, /// Collection of string literals str_pieces: Vec>, /// Stays `true` if all formatting parameters are default (as in "{}{}"). all_pieces_simple: bool, /// Mapping between positional argument references and indices into the /// final generated static argument array. We record the starting indices /// corresponding to each positional argument, and number of references /// consumed so far for each argument, to facilitate correct `Position` /// mapping in `build_piece`. In effect this can be seen as a "flattened" /// version of `arg_unique_types`. /// /// Again with the example described above in docstring for `args`: /// /// * `arg_index_map` (in JSON): `[[0, 1, 0], [2, 3, 3], [4, 5]]` arg_index_map: Vec>, /// Starting offset of count argument slots. count_args_index_offset: usize, /// Count argument slots and tracking data structures. /// Count arguments are separately tracked for de-duplication in case /// multiple references are made to one argument. For example, in this /// format string: /// /// * Original: `"{:.*} {:.foo$} {1:.*} {:.0$}"` /// * Implicit argument resolution: `"{1:.0$} {2:.foo$} {1:.3$} {4:.0$}"` /// * Name resolution: `"{1:.0$} {2:.5$} {1:.3$} {4:.0$}"` /// * `count_positions` (in JSON): `{0: 0, 5: 1, 3: 2}` /// * `count_args`: `vec![0, 5, 3]` count_args: Vec, /// Relative slot numbers for count arguments. count_positions: FxHashMap, /// Number of count slots assigned. count_positions_count: usize, /// Current position of the implicit positional arg pointer, as if it /// still existed in this phase of processing. /// Used only for `all_pieces_simple` tracking in `build_piece`. curarg: usize, /// Current piece being evaluated, used for error reporting. curpiece: usize, /// Keep track of invalid references to positional arguments. invalid_refs: Vec<(usize, usize)>, /// Spans of all the formatting arguments, in order. arg_spans: Vec, /// All the formatting arguments that have formatting flags set, in order for diagnostics. arg_with_formatting: Vec>, /// Whether this format string came from a string literal, as opposed to a macro. is_literal: bool, unused_names_lint: PositionalNamedArgsLint, } pub struct FormatArg { expr: P, name: Option, } /// Parses the arguments from the given list of tokens, returning the diagnostic /// if there's a parse error so we can continue parsing other format! /// expressions. /// /// If parsing succeeds, the return value is: /// /// ```text /// Some((fmtstr, parsed arguments, index map for named arguments)) /// ``` fn parse_args<'a>( ecx: &mut ExtCtxt<'a>, sp: Span, tts: TokenStream, ) -> PResult<'a, (P, Vec, FxHashMap)> { let mut args = Vec::::new(); let mut names = FxHashMap::::default(); let mut p = ecx.new_parser_from_tts(tts); if p.token == token::Eof { return Err(ecx.struct_span_err(sp, "requires at least a format string argument")); } let first_token = &p.token; let fmtstr = match first_token.kind { token::TokenKind::Literal(token::Lit { kind: token::LitKind::Str | token::LitKind::StrRaw(_), .. }) => { // If the first token is a string literal, then a format expression // is constructed from it. // // This allows us to properly handle cases when the first comma // after the format string is mistakenly replaced with any operator, // which cause the expression parser to eat too much tokens. p.parse_literal_maybe_minus()? } _ => { // Otherwise, we fall back to the expression parser. p.parse_expr()? } }; let mut first = true; let mut named = false; while p.token != token::Eof { if !p.eat(&token::Comma) { if first { p.clear_expected_tokens(); } match p.expect(&token::Comma) { Err(mut err) => { match token::TokenKind::Comma.similar_tokens() { Some(tks) if tks.contains(&p.token.kind) => { // If a similar token is found, then it may be a typo. We // consider it as a comma, and continue parsing. err.emit(); p.bump(); } // Otherwise stop the parsing and return the error. _ => return Err(err), } } Ok(recovered) => { assert!(recovered); } } } first = false; if p.token == token::Eof { break; } // accept trailing commas match p.token.ident() { Some((ident, _)) if p.look_ahead(1, |t| *t == token::Eq) => { named = true; p.bump(); p.expect(&token::Eq)?; let e = p.parse_expr()?; if let Some(&prev) = names.get(&ident.name) { ecx.struct_span_err(e.span, &format!("duplicate argument named `{}`", ident)) .span_label(args[prev].expr.span, "previously here") .span_label(e.span, "duplicate argument") .emit(); continue; } // Resolve names into slots early. // Since all the positional args are already seen at this point // if the input is valid, we can simply append to the positional // args. And remember the names. let slot = args.len(); names.insert(ident.name, slot); args.push(FormatArg { expr: e, name: Some(ident) }); } _ => { let e = p.parse_expr()?; if named { let mut err = ecx.struct_span_err( e.span, "positional arguments cannot follow named arguments", ); err.span_label(e.span, "positional arguments must be before named arguments"); for &pos in names.values() { err.span_label(args[pos].expr.span, "named argument"); } err.emit(); } args.push(FormatArg { expr: e, name: None }); } } } Ok((fmtstr, args, names)) } impl<'a, 'b> Context<'a, 'b> { /// The number of arguments that were explicitly given. fn num_args(&self) -> usize { self.args.len() - self.num_captured_args } fn resolve_name_inplace(&mut self, p: &mut parse::Piece<'_>) { // NOTE: the `unwrap_or` branch is needed in case of invalid format // arguments, e.g., `format_args!("{foo}")`. let lookup = |s: &str| self.names.get(&Symbol::intern(s)).copied().unwrap_or(0); match *p { parse::String(_) => {} parse::NextArgument(ref mut arg) => { if let parse::ArgumentNamed(s) = arg.position { arg.position = parse::ArgumentIs(lookup(s)); } if let parse::CountIsName(s, _) = arg.format.width { arg.format.width = parse::CountIsParam(lookup(s)); } if let parse::CountIsName(s, _) = arg.format.precision { arg.format.precision = parse::CountIsParam(lookup(s)); } } } } /// Verifies one piece of a parse string, and remembers it if valid. /// All errors are not emitted as fatal so we can continue giving errors /// about this and possibly other format strings. fn verify_piece(&mut self, p: &parse::Piece<'a>) { match *p { parse::String(..) => {} parse::NextArgument(ref arg) => { // width/precision first, if they have implicit positional // parameters it makes more sense to consume them first. self.verify_count( arg.format.width, &arg.format.width_span, PositionalNamedArgType::Width, ); self.verify_count( arg.format.precision, &arg.format.precision_span, PositionalNamedArgType::Precision, ); let has_precision = arg.format.precision != Count::CountImplied; let has_width = arg.format.width != Count::CountImplied; if has_precision || has_width { // push before named params are resolved to aid diagnostics self.arg_with_formatting.push(arg.format); } // argument second, if it's an implicit positional parameter // it's written second, so it should come after width/precision. let pos = match arg.position { parse::ArgumentIs(i) => { self.unused_names_lint.maybe_add_positional_named_arg( self.args.get(i), PositionalNamedArgType::Arg, self.curpiece, Some(arg.position_span), has_precision || has_width, ); Exact(i) } parse::ArgumentImplicitlyIs(i) => { self.unused_names_lint.maybe_add_positional_named_arg( self.args.get(i), PositionalNamedArgType::Arg, self.curpiece, None, has_precision || has_width, ); Exact(i) } parse::ArgumentNamed(s) => { let symbol = Symbol::intern(s); let span = arg.position_span; Named(symbol, InnerSpan::new(span.start, span.end)) } }; let ty = Placeholder(match arg.format.ty { "" => "Display", "?" => "Debug", "e" => "LowerExp", "E" => "UpperExp", "o" => "Octal", "p" => "Pointer", "b" => "Binary", "x" => "LowerHex", "X" => "UpperHex", _ => { let fmtsp = self.fmtsp; let sp = arg .format .ty_span .map(|sp| fmtsp.from_inner(InnerSpan::new(sp.start, sp.end))); let mut err = self.ecx.struct_span_err( sp.unwrap_or(fmtsp), &format!("unknown format trait `{}`", arg.format.ty), ); err.note( "the only appropriate formatting traits are:\n\ - ``, which uses the `Display` trait\n\ - `?`, which uses the `Debug` trait\n\ - `e`, which uses the `LowerExp` trait\n\ - `E`, which uses the `UpperExp` trait\n\ - `o`, which uses the `Octal` trait\n\ - `p`, which uses the `Pointer` trait\n\ - `b`, which uses the `Binary` trait\n\ - `x`, which uses the `LowerHex` trait\n\ - `X`, which uses the `UpperHex` trait", ); if let Some(sp) = sp { for (fmt, name) in &[ ("", "Display"), ("?", "Debug"), ("e", "LowerExp"), ("E", "UpperExp"), ("o", "Octal"), ("p", "Pointer"), ("b", "Binary"), ("x", "LowerHex"), ("X", "UpperHex"), ] { // FIXME: rustfix (`run-rustfix`) fails to apply suggestions. // > "Cannot replace slice of data that was already replaced" err.tool_only_span_suggestion( sp, &format!("use the `{}` trait", name), *fmt, Applicability::MaybeIncorrect, ); } } err.emit(); "" } }); self.verify_arg_type(pos, ty); self.curpiece += 1; } } } fn verify_count( &mut self, c: parse::Count<'_>, inner_span: &Option, named_arg_type: PositionalNamedArgType, ) { match c { parse::CountImplied | parse::CountIs(..) => {} parse::CountIsParam(i) | parse::CountIsStar(i) => { self.unused_names_lint.maybe_add_positional_named_arg( self.args.get(i), named_arg_type, self.curpiece, *inner_span, true, ); self.verify_arg_type(Exact(i), Count); } parse::CountIsName(s, span) => { self.verify_arg_type( Named(Symbol::intern(s), InnerSpan::new(span.start, span.end)), Count, ); } } } fn describe_num_args(&self) -> Cow<'_, str> { match self.num_args() { 0 => "no arguments were given".into(), 1 => "there is 1 argument".into(), x => format!("there are {} arguments", x).into(), } } /// Handle invalid references to positional arguments. Output different /// errors for the case where all arguments are positional and for when /// there are named arguments or numbered positional arguments in the /// format string. fn report_invalid_references(&self, numbered_position_args: bool) { let mut e; let sp = if !self.arg_spans.is_empty() { // Point at the formatting arguments. MultiSpan::from_spans(self.arg_spans.clone()) } else { MultiSpan::from_span(self.fmtsp) }; let refs = self.invalid_refs.iter().map(|(r, pos)| (r.to_string(), self.arg_spans.get(*pos))); let mut zero_based_note = false; let count = self.pieces.len() + self .arg_with_formatting .iter() .filter(|fmt| matches!(fmt.precision, parse::CountIsStar(_))) .count(); if self.names.is_empty() && !numbered_position_args && count != self.num_args() { e = self.ecx.struct_span_err( sp, &format!( "{} positional argument{} in format string, but {}", count, pluralize!(count), self.describe_num_args(), ), ); for arg in &self.args { // Point at the arguments that will be formatted. e.span_label(arg.expr.span, ""); } } else { let (mut refs, spans): (Vec<_>, Vec<_>) = refs.unzip(); // Avoid `invalid reference to positional arguments 7 and 7 (there is 1 argument)` // for `println!("{7:7$}", 1);` refs.sort(); refs.dedup(); let spans: Vec<_> = spans.into_iter().filter_map(|sp| sp.copied()).collect(); let sp = if self.arg_spans.is_empty() || spans.is_empty() { MultiSpan::from_span(self.fmtsp) } else { MultiSpan::from_spans(spans) }; let arg_list = if refs.len() == 1 { format!("argument {}", refs[0]) } else { let reg = refs.pop().unwrap(); format!("arguments {head} and {tail}", head = refs.join(", "), tail = reg) }; e = self.ecx.struct_span_err( sp, &format!( "invalid reference to positional {} ({})", arg_list, self.describe_num_args() ), ); zero_based_note = true; }; for fmt in &self.arg_with_formatting { if let Some(span) = fmt.precision_span { let span = self.fmtsp.from_inner(InnerSpan::new(span.start, span.end)); match fmt.precision { parse::CountIsParam(pos) if pos >= self.num_args() => { e.span_label( span, &format!( "this precision flag expects an `usize` argument at position {}, \ but {}", pos, self.describe_num_args(), ), ); zero_based_note = true; } parse::CountIsStar(pos) => { let count = self.pieces.len() + self .arg_with_formatting .iter() .filter(|fmt| matches!(fmt.precision, parse::CountIsStar(_))) .count(); e.span_label( span, &format!( "this precision flag adds an extra required argument at position {}, \ which is why there {} expected", pos, if count == 1 { "is 1 argument".to_string() } else { format!("are {} arguments", count) }, ), ); if let Some(arg) = self.args.get(pos) { e.span_label( arg.expr.span, "this parameter corresponds to the precision flag", ); } zero_based_note = true; } _ => {} } } if let Some(span) = fmt.width_span { let span = self.fmtsp.from_inner(InnerSpan::new(span.start, span.end)); match fmt.width { parse::CountIsParam(pos) if pos >= self.num_args() => { e.span_label( span, &format!( "this width flag expects an `usize` argument at position {}, \ but {}", pos, self.describe_num_args(), ), ); zero_based_note = true; } _ => {} } } } if zero_based_note { e.note("positional arguments are zero-based"); } if !self.arg_with_formatting.is_empty() { e.note( "for information about formatting flags, visit \ https://doc.rust-lang.org/std/fmt/index.html", ); } e.emit(); } /// Actually verifies and tracks a given format placeholder /// (a.k.a. argument). fn verify_arg_type(&mut self, arg: Position, ty: ArgumentType) { if let Exact(arg) = arg { if arg >= self.num_args() { self.invalid_refs.push((arg, self.curpiece)); return; } } match arg { Exact(arg) | Capture(arg) => { match ty { Placeholder(_) => { // record every (position, type) combination only once let seen_ty = &mut self.arg_unique_types[arg]; let i = seen_ty.iter().position(|x| *x == ty).unwrap_or_else(|| { let i = seen_ty.len(); seen_ty.push(ty); i }); self.arg_types[arg].push(i); } Count => { if let Entry::Vacant(e) = self.count_positions.entry(arg) { let i = self.count_positions_count; e.insert(i); self.count_args.push(arg); self.count_positions_count += 1; } } } } Named(name, span) => { match self.names.get(&name) { Some(&idx) => { // Treat as positional arg. self.verify_arg_type(Capture(idx), ty) } None => { // For the moment capturing variables from format strings expanded from macros is // disabled (see RFC #2795) if self.is_literal { // Treat this name as a variable to capture from the surrounding scope let idx = self.args.len(); self.arg_types.push(Vec::new()); self.arg_unique_types.push(Vec::new()); let span = if self.is_literal { self.fmtsp.from_inner(span) } else { self.fmtsp }; self.num_captured_args += 1; self.args.push(FormatArg { expr: self.ecx.expr_ident(span, Ident::new(name, span)), name: Some(Ident::new(name, span)), }); self.names.insert(name, idx); self.verify_arg_type(Capture(idx), ty) } else { let msg = format!("there is no argument named `{}`", name); let sp = if self.is_literal { self.fmtsp.from_inner(span) } else { self.fmtsp }; let mut err = self.ecx.struct_span_err(sp, &msg); err.note(&format!( "did you intend to capture a variable `{}` from \ the surrounding scope?", name )); err.note( "to avoid ambiguity, `format_args!` cannot capture variables \ when the format string is expanded from a macro", ); err.emit(); } } } } } } /// Builds the mapping between format placeholders and argument objects. fn build_index_map(&mut self) { // NOTE: Keep the ordering the same as `into_expr`'s expansion would do! let args_len = self.args.len(); self.arg_index_map.reserve(args_len); let mut sofar = 0usize; // Map the arguments for i in 0..args_len { let arg_types = &self.arg_types[i]; let arg_offsets = arg_types.iter().map(|offset| sofar + *offset).collect::>(); self.arg_index_map.push(arg_offsets); sofar += self.arg_unique_types[i].len(); } // Record starting index for counts, which appear just after arguments self.count_args_index_offset = sofar; } fn rtpath(ecx: &ExtCtxt<'_>, s: Symbol) -> Vec { ecx.std_path(&[sym::fmt, sym::rt, sym::v1, s]) } fn build_count(&self, c: parse::Count<'_>) -> P { let sp = self.macsp; let count = |c, arg| { let mut path = Context::rtpath(self.ecx, sym::Count); path.push(Ident::new(c, sp)); match arg { Some(arg) => self.ecx.expr_call_global(sp, path, vec![arg]), None => self.ecx.expr_path(self.ecx.path_global(sp, path)), } }; match c { parse::CountIs(i) => count(sym::Is, Some(self.ecx.expr_usize(sp, i))), parse::CountIsParam(i) | parse::CountIsStar(i) => { // This needs mapping too, as `i` is referring to a macro // argument. If `i` is not found in `count_positions` then // the error had already been emitted elsewhere. let i = self.count_positions.get(&i).cloned().unwrap_or(0) + self.count_args_index_offset; count(sym::Param, Some(self.ecx.expr_usize(sp, i))) } parse::CountImplied => count(sym::Implied, None), // should never be the case, names are already resolved parse::CountIsName(..) => panic!("should never happen"), } } /// Build a literal expression from the accumulated string literals fn build_literal_string(&mut self) -> P { let sp = self.fmtsp; let s = Symbol::intern(&self.literal); self.literal.clear(); self.ecx.expr_str(sp, s) } /// Builds a static `rt::Argument` from a `parse::Piece` or append /// to the `literal` string. fn build_piece( &mut self, piece: &parse::Piece<'a>, arg_index_consumed: &mut Vec, ) -> Option> { let sp = self.macsp; match *piece { parse::String(s) => { self.literal.push_str(s); None } parse::NextArgument(ref arg) => { // Build the position let pos = { match arg.position { parse::ArgumentIs(i, ..) | parse::ArgumentImplicitlyIs(i) => { // Map to index in final generated argument array // in case of multiple types specified let arg_idx = match arg_index_consumed.get_mut(i) { None => 0, // error already emitted elsewhere Some(offset) => { let idx_map = &self.arg_index_map[i]; // unwrap_or branch: error already emitted elsewhere let arg_idx = *idx_map.get(*offset).unwrap_or(&0); *offset += 1; arg_idx } }; self.ecx.expr_usize(sp, arg_idx) } // should never be the case, because names are already // resolved. parse::ArgumentNamed(..) => panic!("should never happen"), } }; let simple_arg = parse::Argument { position: { // We don't have ArgumentNext any more, so we have to // track the current argument ourselves. let i = self.curarg; self.curarg += 1; parse::ArgumentIs(i) }, position_span: arg.position_span, format: parse::FormatSpec { fill: None, align: parse::AlignUnknown, flags: 0, precision: parse::CountImplied, precision_span: arg.format.precision_span, width: parse::CountImplied, width_span: arg.format.width_span, ty: arg.format.ty, ty_span: arg.format.ty_span, }, }; let fill = arg.format.fill.unwrap_or(' '); let pos_simple = arg.position.index() == simple_arg.position.index(); if !pos_simple || arg.format != simple_arg.format { self.all_pieces_simple = false; } // Build the format let fill = self.ecx.expr_char(sp, fill); let align = |name| { let mut p = Context::rtpath(self.ecx, sym::Alignment); p.push(Ident::new(name, sp)); self.ecx.path_global(sp, p) }; let align = match arg.format.align { parse::AlignLeft => align(sym::Left), parse::AlignRight => align(sym::Right), parse::AlignCenter => align(sym::Center), parse::AlignUnknown => align(sym::Unknown), }; let align = self.ecx.expr_path(align); let flags = self.ecx.expr_u32(sp, arg.format.flags); let prec = self.build_count(arg.format.precision); let width = self.build_count(arg.format.width); let path = self.ecx.path_global(sp, Context::rtpath(self.ecx, sym::FormatSpec)); let fmt = self.ecx.expr_struct( sp, path, vec![ self.ecx.field_imm(sp, Ident::new(sym::fill, sp), fill), self.ecx.field_imm(sp, Ident::new(sym::align, sp), align), self.ecx.field_imm(sp, Ident::new(sym::flags, sp), flags), self.ecx.field_imm(sp, Ident::new(sym::precision, sp), prec), self.ecx.field_imm(sp, Ident::new(sym::width, sp), width), ], ); let path = self.ecx.path_global(sp, Context::rtpath(self.ecx, sym::Argument)); Some(self.ecx.expr_struct( sp, path, vec![ self.ecx.field_imm(sp, Ident::new(sym::position, sp), pos), self.ecx.field_imm(sp, Ident::new(sym::format, sp), fmt), ], )) } } } /// Actually builds the expression which the format_args! block will be /// expanded to. fn into_expr(self) -> P { let mut original_args = self.args; let mut fmt_args = Vec::with_capacity( self.arg_unique_types.iter().map(|v| v.len()).sum::() + self.count_args.len(), ); // First, build up the static array which will become our precompiled // format "string" let pieces = self.ecx.expr_array_ref(self.fmtsp, self.str_pieces); // We need to construct a &[ArgumentV1] to pass into the fmt::Arguments // constructor. In general the expressions in this slice might be // permuted from their order in original_args (such as in the case of // "{1} {0}"), or may have multiple entries referring to the same // element of original_args ("{0} {0}"). // // The following vector has one item per element of our output slice, // identifying the index of which element of original_args it's passing, // and that argument's type. let mut fmt_arg_index_and_ty = SmallVec::<[(usize, &ArgumentType); 8]>::new(); for (i, unique_types) in self.arg_unique_types.iter().enumerate() { fmt_arg_index_and_ty.extend(unique_types.iter().map(|ty| (i, ty))); } fmt_arg_index_and_ty.extend(self.count_args.iter().map(|&i| (i, &Count))); // Figure out whether there are permuted or repeated elements. If not, // we can generate simpler code. // // The sequence has no indices out of order or repeated if: for every // adjacent pair of elements, the first one's index is less than the // second one's index. let nicely_ordered = fmt_arg_index_and_ty.array_windows().all(|[(i, _i_ty), (j, _j_ty)]| i < j); // We want to emit: // // [ArgumentV1::new(&$arg0, …), ArgumentV1::new(&$arg1, …), …] // // However, it's only legal to do so if $arg0, $arg1, … were written in // exactly that order by the programmer. When arguments are permuted, we // want them evaluated in the order written by the programmer, not in // the order provided to fmt::Arguments. When arguments are repeated, we // want the expression evaluated only once. // // Further, if any arg _after the first one_ contains a yield point such // as `await` or `yield`, the above short form is inconvenient for the // caller because it would keep a temporary of type ArgumentV1 alive // across the yield point. ArgumentV1 can't implement Send since it // holds a type-erased arbitrary type. // // Thus in the not nicely ordered case, and in the yielding case, we // emit the following instead: // // match (&$arg0, &$arg1, …) { // args => [ArgumentV1::new(args.$i, …), ArgumentV1::new(args.$j, …), …] // } // // for the sequence of indices $i, $j, … governed by fmt_arg_index_and_ty. // This more verbose representation ensures that all arguments are // evaluated a single time each, in the order written by the programmer, // and that the surrounding future/generator (if any) is Send whenever // possible. let no_need_for_match = nicely_ordered && !original_args.iter().skip(1).any(|arg| may_contain_yield_point(&arg.expr)); for (arg_index, arg_ty) in fmt_arg_index_and_ty { let e = &mut original_args[arg_index].expr; let span = e.span; let arg = if no_need_for_match { let expansion_span = e.span.with_ctxt(self.macsp.ctxt()); // The indices are strictly ordered so e has not been taken yet. self.ecx.expr_addr_of(expansion_span, P(e.take())) } else { let def_site = self.ecx.with_def_site_ctxt(span); let args_tuple = self.ecx.expr_ident(def_site, Ident::new(sym::args, def_site)); let member = Ident::new(sym::integer(arg_index), def_site); self.ecx.expr(def_site, ast::ExprKind::Field(args_tuple, member)) }; fmt_args.push(Context::format_arg(self.ecx, self.macsp, span, arg_ty, arg)); } let args_array = self.ecx.expr_array(self.macsp, fmt_args); let args_slice = self.ecx.expr_addr_of( self.macsp, if no_need_for_match { args_array } else { // In the !no_need_for_match case, none of the exprs were moved // away in the previous loop. // // This uses the arg span for `&arg` so that borrowck errors // point to the specific expression passed to the macro (the // span is otherwise unavailable in the MIR used by borrowck). let heads = original_args .into_iter() .map(|arg| { self.ecx.expr_addr_of(arg.expr.span.with_ctxt(self.macsp.ctxt()), arg.expr) }) .collect(); let pat = self.ecx.pat_ident(self.macsp, Ident::new(sym::args, self.macsp)); let arm = self.ecx.arm(self.macsp, pat, args_array); let head = self.ecx.expr(self.macsp, ast::ExprKind::Tup(heads)); self.ecx.expr_match(self.macsp, head, vec![arm]) }, ); // Now create the fmt::Arguments struct with all our locals we created. let (fn_name, fn_args) = if self.all_pieces_simple { ("new_v1", vec![pieces, args_slice]) } else { // Build up the static array which will store our precompiled // nonstandard placeholders, if there are any. let fmt = self.ecx.expr_array_ref(self.macsp, self.pieces); let path = self.ecx.std_path(&[sym::fmt, sym::UnsafeArg, sym::new]); let unsafe_arg = self.ecx.expr_call_global(self.macsp, path, Vec::new()); let unsafe_expr = self.ecx.expr_block(P(ast::Block { stmts: vec![self.ecx.stmt_expr(unsafe_arg)], id: ast::DUMMY_NODE_ID, rules: BlockCheckMode::Unsafe(UnsafeSource::CompilerGenerated), span: self.macsp, tokens: None, could_be_bare_literal: false, })); ("new_v1_formatted", vec![pieces, args_slice, fmt, unsafe_expr]) }; let path = self.ecx.std_path(&[sym::fmt, sym::Arguments, Symbol::intern(fn_name)]); self.ecx.expr_call_global(self.macsp, path, fn_args) } fn format_arg( ecx: &ExtCtxt<'_>, macsp: Span, mut sp: Span, ty: &ArgumentType, arg: P, ) -> P { sp = ecx.with_def_site_ctxt(sp); let trait_ = match *ty { Placeholder(trait_) if trait_ == "" => return DummyResult::raw_expr(sp, true), Placeholder(trait_) => trait_, Count => { let path = ecx.std_path(&[sym::fmt, sym::ArgumentV1, sym::from_usize]); return ecx.expr_call_global(macsp, path, vec![arg]); } }; let new_fn_name = match trait_ { "Display" => "new_display", "Debug" => "new_debug", "LowerExp" => "new_lower_exp", "UpperExp" => "new_upper_exp", "Octal" => "new_octal", "Pointer" => "new_pointer", "Binary" => "new_binary", "LowerHex" => "new_lower_hex", "UpperHex" => "new_upper_hex", _ => unreachable!(), }; let path = ecx.std_path(&[sym::fmt, sym::ArgumentV1, Symbol::intern(new_fn_name)]); ecx.expr_call_global(sp, path, vec![arg]) } } fn expand_format_args_impl<'cx>( ecx: &'cx mut ExtCtxt<'_>, mut sp: Span, tts: TokenStream, nl: bool, ) -> Box { sp = ecx.with_def_site_ctxt(sp); match parse_args(ecx, sp, tts) { Ok((efmt, args, names)) => { MacEager::expr(expand_preparsed_format_args(ecx, sp, efmt, args, names, nl)) } Err(mut err) => { err.emit(); DummyResult::any(sp) } } } pub fn expand_format_args<'cx>( ecx: &'cx mut ExtCtxt<'_>, sp: Span, tts: TokenStream, ) -> Box { expand_format_args_impl(ecx, sp, tts, false) } pub fn expand_format_args_nl<'cx>( ecx: &'cx mut ExtCtxt<'_>, sp: Span, tts: TokenStream, ) -> Box { expand_format_args_impl(ecx, sp, tts, true) } fn create_lints_for_named_arguments_used_positionally(cx: &mut Context<'_, '_>) { for named_arg in &cx.unused_names_lint.positional_named_args { let (position_sp_to_replace, position_sp_for_msg) = named_arg.get_positional_arg_spans(cx); let msg = format!("named argument `{}` is not used by name", named_arg.replacement); cx.ecx.buffered_early_lint.push(BufferedEarlyLint { span: MultiSpan::from_span(named_arg.positional_named_arg_span), msg: msg.into(), node_id: ast::CRATE_NODE_ID, lint_id: LintId::of(&NAMED_ARGUMENTS_USED_POSITIONALLY), diagnostic: BuiltinLintDiagnostics::NamedArgumentUsedPositionally { position_sp_to_replace, position_sp_for_msg, named_arg_sp: named_arg.positional_named_arg_span, named_arg_name: named_arg.replacement.to_string(), is_formatting_arg: named_arg.ty != PositionalNamedArgType::Arg, }, }); } } /// Take the various parts of `format_args!(efmt, args..., name=names...)` /// and construct the appropriate formatting expression. pub fn expand_preparsed_format_args( ecx: &mut ExtCtxt<'_>, sp: Span, efmt: P, args: Vec, names: FxHashMap, append_newline: bool, ) -> P { // NOTE: this verbose way of initializing `Vec>` is because // `ArgumentType` does not derive `Clone`. let arg_types: Vec<_> = (0..args.len()).map(|_| Vec::new()).collect(); let arg_unique_types: Vec<_> = (0..args.len()).map(|_| Vec::new()).collect(); let mut macsp = ecx.call_site(); macsp = ecx.with_def_site_ctxt(macsp); let msg = "format argument must be a string literal"; let fmt_sp = efmt.span; let efmt_kind_is_lit: bool = matches!(efmt.kind, ast::ExprKind::Lit(_)); let (fmt_str, fmt_style, fmt_span) = match expr_to_spanned_string(ecx, efmt, msg) { Ok(mut fmt) if append_newline => { fmt.0 = Symbol::intern(&format!("{}\n", fmt.0)); fmt } Ok(fmt) => fmt, Err(err) => { if let Some((mut err, suggested)) = err { let sugg_fmt = match args.len() { 0 => "{}".to_string(), _ => format!("{}{{}}", "{} ".repeat(args.len())), }; if !suggested { err.span_suggestion( fmt_sp.shrink_to_lo(), "you might be missing a string literal to format with", format!("\"{}\", ", sugg_fmt), Applicability::MaybeIncorrect, ); } err.emit(); } return DummyResult::raw_expr(sp, true); } }; let str_style = match fmt_style { ast::StrStyle::Cooked => None, ast::StrStyle::Raw(raw) => Some(raw as usize), }; let fmt_str = fmt_str.as_str(); // for the suggestions below let fmt_snippet = ecx.source_map().span_to_snippet(fmt_sp).ok(); let mut parser = parse::Parser::new( fmt_str, str_style, fmt_snippet, append_newline, parse::ParseMode::Format, ); let mut unverified_pieces = Vec::new(); while let Some(piece) = parser.next() { if !parser.errors.is_empty() { break; } else { unverified_pieces.push(piece); } } if !parser.errors.is_empty() { let err = parser.errors.remove(0); let sp = if efmt_kind_is_lit { fmt_span.from_inner(InnerSpan::new(err.span.start, err.span.end)) } else { // The format string could be another macro invocation, e.g.: // format!(concat!("abc", "{}"), 4); // However, `err.span` is an inner span relative to the *result* of // the macro invocation, which is why we would get a nonsensical // result calling `fmt_span.from_inner(err.span)` as above, and // might even end up inside a multibyte character (issue #86085). // Therefore, we conservatively report the error for the entire // argument span here. fmt_span }; let mut e = ecx.struct_span_err(sp, &format!("invalid format string: {}", err.description)); e.span_label(sp, err.label + " in format string"); if let Some(note) = err.note { e.note(¬e); } if let Some((label, span)) = err.secondary_label { if efmt_kind_is_lit { e.span_label(fmt_span.from_inner(InnerSpan::new(span.start, span.end)), label); } } if err.should_be_replaced_with_positional_argument { let captured_arg_span = fmt_span.from_inner(InnerSpan::new(err.span.start, err.span.end)); let n_positional_args = args.iter().rposition(|arg| arg.name.is_none()).map_or(0, |i| i + 1); if let Ok(arg) = ecx.source_map().span_to_snippet(captured_arg_span) { let span = match args[..n_positional_args].last() { Some(arg) => arg.expr.span, None => fmt_sp, }; e.multipart_suggestion_verbose( "consider using a positional formatting argument instead", vec![ (captured_arg_span, n_positional_args.to_string()), (span.shrink_to_hi(), format!(", {}", arg)), ], Applicability::MachineApplicable, ); } } e.emit(); return DummyResult::raw_expr(sp, true); } let arg_spans = parser .arg_places .iter() .map(|span| fmt_span.from_inner(InnerSpan::new(span.start, span.end))) .collect(); let mut cx = Context { ecx, args, num_captured_args: 0, arg_types, arg_unique_types, names, curarg: 0, curpiece: 0, arg_index_map: Vec::new(), count_args: Vec::new(), count_positions: FxHashMap::default(), count_positions_count: 0, count_args_index_offset: 0, literal: String::new(), pieces: Vec::with_capacity(unverified_pieces.len()), str_pieces: Vec::with_capacity(unverified_pieces.len()), all_pieces_simple: true, macsp, fmtsp: fmt_span, invalid_refs: Vec::new(), arg_spans, arg_with_formatting: Vec::new(), is_literal: parser.is_literal, unused_names_lint: PositionalNamedArgsLint { positional_named_args: vec![] }, }; // This needs to happen *after* the Parser has consumed all pieces to create all the spans let pieces = unverified_pieces .into_iter() .map(|mut piece| { cx.verify_piece(&piece); cx.resolve_name_inplace(&mut piece); piece }) .collect::>(); let numbered_position_args = pieces.iter().any(|arg: &parse::Piece<'_>| match *arg { parse::String(_) => false, parse::NextArgument(arg) => matches!(arg.position, parse::Position::ArgumentIs(..)), }); cx.build_index_map(); let mut arg_index_consumed = vec![0usize; cx.arg_index_map.len()]; for piece in pieces { if let Some(piece) = cx.build_piece(&piece, &mut arg_index_consumed) { let s = cx.build_literal_string(); cx.str_pieces.push(s); cx.pieces.push(piece); } } if !cx.literal.is_empty() { let s = cx.build_literal_string(); cx.str_pieces.push(s); } if !cx.invalid_refs.is_empty() { cx.report_invalid_references(numbered_position_args); } // Make sure that all arguments were used and all arguments have types. let errs = cx .arg_types .iter() .enumerate() .filter(|(i, ty)| ty.is_empty() && !cx.count_positions.contains_key(&i)) .map(|(i, _)| { let msg = if cx.args[i].name.is_some() { "named argument never used" } else { "argument never used" }; (cx.args[i].expr.span, msg) }) .collect::>(); let errs_len = errs.len(); if !errs.is_empty() { let args_used = cx.arg_types.len() - errs_len; let args_unused = errs_len; let mut diag = { if let [(sp, msg)] = &errs[..] { let mut diag = cx.ecx.struct_span_err(*sp, *msg); diag.span_label(*sp, *msg); diag } else { let mut diag = cx.ecx.struct_span_err( errs.iter().map(|&(sp, _)| sp).collect::>(), "multiple unused formatting arguments", ); diag.span_label(cx.fmtsp, "multiple missing formatting specifiers"); for (sp, msg) in errs { diag.span_label(sp, msg); } diag } }; // Used to ensure we only report translations for *one* kind of foreign format. let mut found_foreign = false; // Decide if we want to look for foreign formatting directives. if args_used < args_unused { use super::format_foreign as foreign; // The set of foreign substitutions we've explained. This prevents spamming the user // with `%d should be written as {}` over and over again. let mut explained = FxHashSet::default(); macro_rules! check_foreign { ($kind:ident) => {{ let mut show_doc_note = false; let mut suggestions = vec![]; // account for `"` and account for raw strings `r#` let padding = str_style.map(|i| i + 2).unwrap_or(1); for sub in foreign::$kind::iter_subs(fmt_str, padding) { let (trn, success) = match sub.translate() { Ok(trn) => (trn, true), Err(Some(msg)) => (msg, false), // If it has no translation, don't call it out specifically. _ => continue, }; let pos = sub.position(); let sub = String::from(sub.as_str()); if explained.contains(&sub) { continue; } explained.insert(sub.clone()); if !found_foreign { found_foreign = true; show_doc_note = true; } if let Some(inner_sp) = pos { let sp = fmt_sp.from_inner(inner_sp); if success { suggestions.push((sp, trn)); } else { diag.span_note( sp, &format!("format specifiers use curly braces, and {}", trn), ); } } else { if success { diag.help(&format!("`{}` should be written as `{}`", sub, trn)); } else { diag.note(&format!( "`{}` should use curly braces, and {}", sub, trn )); } } } if show_doc_note { diag.note(concat!( stringify!($kind), " formatting not supported; see the documentation for `std::fmt`", )); } if suggestions.len() > 0 { diag.multipart_suggestion( "format specifiers use curly braces", suggestions, Applicability::MachineApplicable, ); } }}; } check_foreign!(printf); if !found_foreign { check_foreign!(shell); } } if !found_foreign && errs_len == 1 { diag.span_label(cx.fmtsp, "formatting specifier missing"); } diag.emit(); } else if cx.invalid_refs.is_empty() && cx.ecx.sess.err_count() == 0 { // Only check for unused named argument names if there are no other errors to avoid causing // too much noise in output errors, such as when a named argument is entirely unused. create_lints_for_named_arguments_used_positionally(&mut cx); } cx.into_expr() } fn may_contain_yield_point(e: &ast::Expr) -> bool { struct MayContainYieldPoint(bool); impl Visitor<'_> for MayContainYieldPoint { fn visit_expr(&mut self, e: &ast::Expr) { if let ast::ExprKind::Await(_) | ast::ExprKind::Yield(_) = e.kind { self.0 = true; } else { visit::walk_expr(self, e); } } fn visit_mac_call(&mut self, _: &ast::MacCall) { self.0 = true; } fn visit_attribute(&mut self, _: &ast::Attribute) { // Conservatively assume this may be a proc macro attribute in // expression position. self.0 = true; } fn visit_item(&mut self, _: &ast::Item) { // Do not recurse into nested items. } } let mut visitor = MayContainYieldPoint(false); visitor.visit_expr(e); visitor.0 }