src/tools/rustfmt/src/macros.rs

   1 // Format list-like macro invocations. These are invocations whose token trees
   2 // can be interpreted as expressions and separated by commas.
   3 // Note that these token trees do not actually have to be interpreted as
   4 // expressions by the compiler. An example of an invocation we would reformat is
   5 // foo!( x, y, z ). The token x may represent an identifier in the code, but we
   6 // interpreted as an expression.
   7 // Macro uses which are not-list like, such as bar!(key => val), will not be
   8 // reformatted.
   9 // List-like invocations with parentheses will be formatted as function calls,
  10 // and those with brackets will be formatted as array literals.
  11
  12 use std::collections::HashMap;
  13 use std::panic::{catch_unwind, AssertUnwindSafe};
  14
  15 use rustc_ast::token::{BinOpToken, Delimiter, Token, TokenKind};
  16 use rustc_ast::tokenstream::{Cursor, Spacing, TokenStream, TokenTree};
  17 use rustc_ast::{ast, ptr};
  18 use rustc_ast_pretty::pprust;
  19 use rustc_span::{
  20     symbol::{self, kw},
  21     BytePos, Span, Symbol, DUMMY_SP,
  22 };
  23
  24 use crate::comment::{
  25     contains_comment, CharClasses, FindUncommented, FullCodeCharKind, LineClasses,
  26 };
  27 use crate::config::lists::*;
  28 use crate::expr::{rewrite_array, rewrite_assign_rhs, RhsAssignKind};
  29 use crate::lists::{itemize_list, write_list, ListFormatting};
  30 use crate::overflow;
  31 use crate::parse::macros::lazy_static::parse_lazy_static;
  32 use crate::parse::macros::{parse_expr, parse_macro_args, ParsedMacroArgs};
  33 use crate::rewrite::{Rewrite, RewriteContext};
  34 use crate::shape::{Indent, Shape};
  35 use crate::source_map::SpanUtils;
  36 use crate::spanned::Spanned;
  37 use crate::utils::{
  38     format_visibility, indent_next_line, is_empty_line, mk_sp, remove_trailing_white_spaces,
  39     rewrite_ident, trim_left_preserve_layout, wrap_str, NodeIdExt,
  40 };
  41 use crate::visitor::FmtVisitor;
  42
  43 const FORCED_BRACKET_MACROS: &[&str] = &["vec!"];
  44
  45 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
  46 pub(crate) enum MacroPosition {
  47     Item,
  48     Statement,
  49     Expression,
  50     Pat,
  51 }
  52
  53 #[derive(Debug)]
  54 pub(crate) enum MacroArg {
  55     Expr(ptr::P<ast::Expr>),
  56     Ty(ptr::P<ast::Ty>),
  57     Pat(ptr::P<ast::Pat>),
  58     Item(ptr::P<ast::Item>),
  59     Keyword(symbol::Ident, Span),
  60 }
  61
  62 impl MacroArg {
  63     pub(crate) fn is_item(&self) -> bool {
  64         match self {
  65             MacroArg::Item(..) => true,
  66             _ => false,
  67         }
  68     }
  69 }
  70
  71 impl Rewrite for ast::Item {
  72     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
  73         let mut visitor = crate::visitor::FmtVisitor::from_context(context);
  74         visitor.block_indent = shape.indent;
  75         visitor.last_pos = self.span().lo();
  76         visitor.visit_item(self);
  77         Some(visitor.buffer.to_owned())
  78     }
  79 }
  80
  81 impl Rewrite for MacroArg {
  82     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
  83         match *self {
  84             MacroArg::Expr(ref expr) => expr.rewrite(context, shape),
  85             MacroArg::Ty(ref ty) => ty.rewrite(context, shape),
  86             MacroArg::Pat(ref pat) => pat.rewrite(context, shape),
  87             MacroArg::Item(ref item) => item.rewrite(context, shape),
  88             MacroArg::Keyword(ident, _) => Some(ident.name.to_string()),
  89         }
  90     }
  91 }
  92
  93 /// Rewrite macro name without using pretty-printer if possible.
  94 fn rewrite_macro_name(
  95     context: &RewriteContext<'_>,
  96     path: &ast::Path,
  97     extra_ident: Option<symbol::Ident>,
  98 ) -> String {
  99     let name = if path.segments.len() == 1 {
 100         // Avoid using pretty-printer in the common case.
 101         format!("{}!", rewrite_ident(context, path.segments[0].ident))
 102     } else {
 103         format!("{}!", pprust::path_to_string(path))
 104     };
 105     match extra_ident {
 106         Some(ident) if ident.name != kw::Empty => format!("{} {}", name, ident),
 107         _ => name,
 108     }
 109 }
 110
 111 // Use this on failing to format the macro call.
 112 fn return_macro_parse_failure_fallback(
 113     context: &RewriteContext<'_>,
 114     indent: Indent,
 115     position: MacroPosition,
 116     span: Span,
 117 ) -> Option<String> {
 118     // Mark this as a failure however we format it
 119     context.macro_rewrite_failure.replace(true);
 120
 121     // Heuristically determine whether the last line of the macro uses "Block" style
 122     // rather than using "Visual" style, or another indentation style.
 123     let is_like_block_indent_style = context
 124         .snippet(span)
 125         .lines()
 126         .last()
 127         .map(|closing_line| {
 128             closing_line
 129                 .trim()
 130                 .chars()
 131                 .all(|ch| matches!(ch, '}' | ')' | ']'))
 132         })
 133         .unwrap_or(false);
 134     if is_like_block_indent_style {
 135         return trim_left_preserve_layout(context.snippet(span), indent, context.config);
 136     }
 137
 138     context.skipped_range.borrow_mut().push((
 139         context.parse_sess.line_of_byte_pos(span.lo()),
 140         context.parse_sess.line_of_byte_pos(span.hi()),
 141     ));
 142
 143     // Return the snippet unmodified if the macro is not block-like
 144     let mut snippet = context.snippet(span).to_owned();
 145     if position == MacroPosition::Item {
 146         snippet.push(';');
 147     }
 148     Some(snippet)
 149 }
 150
 151 pub(crate) fn rewrite_macro(
 152     mac: &ast::MacCall,
 153     extra_ident: Option<symbol::Ident>,
 154     context: &RewriteContext<'_>,
 155     shape: Shape,
 156     position: MacroPosition,
 157 ) -> Option<String> {
 158     let should_skip = context
 159         .skip_context
 160         .skip_macro(context.snippet(mac.path.span));
 161     if should_skip {
 162         None
 163     } else {
 164         let guard = context.enter_macro();
 165         let result = catch_unwind(AssertUnwindSafe(|| {
 166             rewrite_macro_inner(
 167                 mac,
 168                 extra_ident,
 169                 context,
 170                 shape,
 171                 position,
 172                 guard.is_nested(),
 173             )
 174         }));
 175         match result {
 176             Err(..) | Ok(None) => {
 177                 context.macro_rewrite_failure.replace(true);
 178                 None
 179             }
 180             Ok(rw) => rw,
 181         }
 182     }
 183 }
 184
 185 fn rewrite_macro_inner(
 186     mac: &ast::MacCall,
 187     extra_ident: Option<symbol::Ident>,
 188     context: &RewriteContext<'_>,
 189     shape: Shape,
 190     position: MacroPosition,
 191     is_nested_macro: bool,
 192 ) -> Option<String> {
 193     if context.config.use_try_shorthand() {
 194         if let Some(expr) = convert_try_mac(mac, context) {
 195             context.leave_macro();
 196             return expr.rewrite(context, shape);
 197         }
 198     }
 199
 200     let original_style = macro_style(mac, context);
 201
 202     let macro_name = rewrite_macro_name(context, &mac.path, extra_ident);
 203     let is_forced_bracket = FORCED_BRACKET_MACROS.contains(&&macro_name[..]);
 204
 205     let style = if is_forced_bracket && !is_nested_macro {
 206         Delimiter::Bracket
 207     } else {
 208         original_style
 209     };
 210
 211     let ts = mac.args.inner_tokens();
 212     let has_comment = contains_comment(context.snippet(mac.span()));
 213     if ts.is_empty() && !has_comment {
 214         return match style {
 215             Delimiter::Parenthesis if position == MacroPosition::Item => {
 216                 Some(format!("{}();", macro_name))
 217             }
 218             Delimiter::Bracket if position == MacroPosition::Item => {
 219                 Some(format!("{}[];", macro_name))
 220             }
 221             Delimiter::Parenthesis => Some(format!("{}()", macro_name)),
 222             Delimiter::Bracket => Some(format!("{}[]", macro_name)),
 223             Delimiter::Brace => Some(format!("{} {{}}", macro_name)),
 224             _ => unreachable!(),
 225         };
 226     }
 227     // Format well-known macros which cannot be parsed as a valid AST.
 228     if macro_name == "lazy_static!" && !has_comment {
 229         if let success @ Some(..) = format_lazy_static(context, shape, ts.clone()) {
 230             return success;
 231         }
 232     }
 233
 234     let ParsedMacroArgs {
 235         args: arg_vec,
 236         vec_with_semi,
 237         trailing_comma,
 238     } = match parse_macro_args(context, ts, style, is_forced_bracket) {
 239         Some(args) => args,
 240         None => {
 241             return return_macro_parse_failure_fallback(
 242                 context,
 243                 shape.indent,
 244                 position,
 245                 mac.span(),
 246             );
 247         }
 248     };
 249
 250     if !arg_vec.is_empty() && arg_vec.iter().all(MacroArg::is_item) {
 251         return rewrite_macro_with_items(
 252             context,
 253             &arg_vec,
 254             &macro_name,
 255             shape,
 256             style,
 257             position,
 258             mac.span(),
 259         );
 260     }
 261
 262     match style {
 263         Delimiter::Parenthesis => {
 264             // Handle special case: `vec!(expr; expr)`
 265             if vec_with_semi {
 266                 handle_vec_semi(context, shape, arg_vec, macro_name, style)
 267             } else {
 268                 // Format macro invocation as function call, preserve the trailing
 269                 // comma because not all macros support them.
 270                 overflow::rewrite_with_parens(
 271                     context,
 272                     &macro_name,
 273                     arg_vec.iter(),
 274                     shape,
 275                     mac.span(),
 276                     context.config.fn_call_width(),
 277                     if trailing_comma {
 278                         Some(SeparatorTactic::Always)
 279                     } else {
 280                         Some(SeparatorTactic::Never)
 281                     },
 282                 )
 283                 .map(|rw| match position {
 284                     MacroPosition::Item => format!("{};", rw),
 285                     _ => rw,
 286                 })
 287             }
 288         }
 289         Delimiter::Bracket => {
 290             // Handle special case: `vec![expr; expr]`
 291             if vec_with_semi {
 292                 handle_vec_semi(context, shape, arg_vec, macro_name, style)
 293             } else {
 294                 // If we are rewriting `vec!` macro or other special macros,
 295                 // then we can rewrite this as a usual array literal.
 296                 // Otherwise, we must preserve the original existence of trailing comma.
 297                 let macro_name = &macro_name.as_str();
 298                 let mut force_trailing_comma = if trailing_comma {
 299                     Some(SeparatorTactic::Always)
 300                 } else {
 301                     Some(SeparatorTactic::Never)
 302                 };
 303                 if FORCED_BRACKET_MACROS.contains(macro_name) && !is_nested_macro {
 304                     context.leave_macro();
 305                     if context.use_block_indent() {
 306                         force_trailing_comma = Some(SeparatorTactic::Vertical);
 307                     };
 308                 }
 309                 let rewrite = rewrite_array(
 310                     macro_name,
 311                     arg_vec.iter(),
 312                     mac.span(),
 313                     context,
 314                     shape,
 315                     force_trailing_comma,
 316                     Some(original_style),
 317                 )?;
 318                 let comma = match position {
 319                     MacroPosition::Item => ";",
 320                     _ => "",
 321                 };
 322
 323                 Some(format!("{}{}", rewrite, comma))
 324             }
 325         }
 326         Delimiter::Brace => {
 327             // For macro invocations with braces, always put a space between
 328             // the `macro_name!` and `{ /* macro_body */ }` but skip modifying
 329             // anything in between the braces (for now).
 330             let snippet = context.snippet(mac.span()).trim_start_matches(|c| c != '{');
 331             match trim_left_preserve_layout(snippet, shape.indent, context.config) {
 332                 Some(macro_body) => Some(format!("{} {}", macro_name, macro_body)),
 333                 None => Some(format!("{} {}", macro_name, snippet)),
 334             }
 335         }
 336         _ => unreachable!(),
 337     }
 338 }
 339
 340 fn handle_vec_semi(
 341     context: &RewriteContext<'_>,
 342     shape: Shape,
 343     arg_vec: Vec<MacroArg>,
 344     macro_name: String,
 345     delim_token: Delimiter,
 346 ) -> Option<String> {
 347     let (left, right) = match delim_token {
 348         Delimiter::Parenthesis => ("(", ")"),
 349         Delimiter::Bracket => ("[", "]"),
 350         _ => unreachable!(),
 351     };
 352
 353     let mac_shape = shape.offset_left(macro_name.len())?;
 354     // 8 = `vec![]` + `; ` or `vec!()` + `; `
 355     let total_overhead = 8;
 356     let nested_shape = mac_shape.block_indent(context.config.tab_spaces());
 357     let lhs = arg_vec[0].rewrite(context, nested_shape)?;
 358     let rhs = arg_vec[1].rewrite(context, nested_shape)?;
 359     if !lhs.contains('\n')
 360         && !rhs.contains('\n')
 361         && lhs.len() + rhs.len() + total_overhead <= shape.width
 362     {
 363         // macro_name(lhs; rhs) or macro_name[lhs; rhs]
 364         Some(format!("{}{}{}; {}{}", macro_name, left, lhs, rhs, right))
 365     } else {
 366         // macro_name(\nlhs;\nrhs\n) or macro_name[\nlhs;\nrhs\n]
 367         Some(format!(
 368             "{}{}{}{};{}{}{}{}",
 369             macro_name,
 370             left,
 371             nested_shape.indent.to_string_with_newline(context.config),
 372             lhs,
 373             nested_shape.indent.to_string_with_newline(context.config),
 374             rhs,
 375             shape.indent.to_string_with_newline(context.config),
 376             right
 377         ))
 378     }
 379 }
 380
 381 pub(crate) fn rewrite_macro_def(
 382     context: &RewriteContext<'_>,
 383     shape: Shape,
 384     indent: Indent,
 385     def: &ast::MacroDef,
 386     ident: symbol::Ident,
 387     vis: &ast::Visibility,
 388     span: Span,
 389 ) -> Option<String> {
 390     let snippet = Some(remove_trailing_white_spaces(context.snippet(span)));
 391     if snippet.as_ref().map_or(true, |s| s.ends_with(';')) {
 392         return snippet;
 393     }
 394
 395     let ts = def.body.inner_tokens();
 396     let mut parser = MacroParser::new(ts.into_trees());
 397     let parsed_def = match parser.parse() {
 398         Some(def) => def,
 399         None => return snippet,
 400     };
 401
 402     let mut result = if def.macro_rules {
 403         String::from("macro_rules!")
 404     } else {
 405         format!("{}macro", format_visibility(context, vis))
 406     };
 407
 408     result += " ";
 409     result += rewrite_ident(context, ident);
 410
 411     let multi_branch_style = def.macro_rules || parsed_def.branches.len() != 1;
 412
 413     let arm_shape = if multi_branch_style {
 414         shape
 415             .block_indent(context.config.tab_spaces())
 416             .with_max_width(context.config)
 417     } else {
 418         shape
 419     };
 420
 421     let branch_items = itemize_list(
 422         context.snippet_provider,
 423         parsed_def.branches.iter(),
 424         "}",
 425         ";",
 426         |branch| branch.span.lo(),
 427         |branch| branch.span.hi(),
 428         |branch| match branch.rewrite(context, arm_shape, multi_branch_style) {
 429             Some(v) => Some(v),
 430             // if the rewrite returned None because a macro could not be rewritten, then return the
 431             // original body
 432             None if context.macro_rewrite_failure.get() => {
 433                 Some(context.snippet(branch.body).trim().to_string())
 434             }
 435             None => None,
 436         },
 437         context.snippet_provider.span_after(span, "{"),
 438         span.hi(),
 439         false,
 440     )
 441     .collect::<Vec<_>>();
 442
 443     let fmt = ListFormatting::new(arm_shape, context.config)
 444         .separator(if def.macro_rules { ";" } else { "" })
 445         .trailing_separator(SeparatorTactic::Always)
 446         .preserve_newline(true);
 447
 448     if multi_branch_style {
 449         result += " {";
 450         result += &arm_shape.indent.to_string_with_newline(context.config);
 451     }
 452
 453     match write_list(&branch_items, &fmt) {
 454         Some(ref s) => result += s,
 455         None => return snippet,
 456     }
 457
 458     if multi_branch_style {
 459         result += &indent.to_string_with_newline(context.config);
 460         result += "}";
 461     }
 462
 463     Some(result)
 464 }
 465
 466 fn register_metavariable(
 467     map: &mut HashMap<String, String>,
 468     result: &mut String,
 469     name: &str,
 470     dollar_count: usize,
 471 ) {
 472     let mut new_name = "$".repeat(dollar_count - 1);
 473     let mut old_name = "$".repeat(dollar_count);
 474
 475     new_name.push('z');
 476     new_name.push_str(name);
 477     old_name.push_str(name);
 478
 479     result.push_str(&new_name);
 480     map.insert(old_name, new_name);
 481 }
 482
 483 // Replaces `$foo` with `zfoo`. We must check for name overlap to ensure we
 484 // aren't causing problems.
 485 // This should also work for escaped `$` variables, where we leave earlier `$`s.
 486 fn replace_names(input: &str) -> Option<(String, HashMap<String, String>)> {
 487     // Each substitution will require five or six extra bytes.
 488     let mut result = String::with_capacity(input.len() + 64);
 489     let mut substs = HashMap::new();
 490     let mut dollar_count = 0;
 491     let mut cur_name = String::new();
 492
 493     for (kind, c) in CharClasses::new(input.chars()) {
 494         if kind != FullCodeCharKind::Normal {
 495             result.push(c);
 496         } else if c == '$' {
 497             dollar_count += 1;
 498         } else if dollar_count == 0 {
 499             result.push(c);
 500         } else if !c.is_alphanumeric() && !cur_name.is_empty() {
 501             // Terminates a name following one or more dollars.
 502             register_metavariable(&mut substs, &mut result, &cur_name, dollar_count);
 503
 504             result.push(c);
 505             dollar_count = 0;
 506             cur_name.clear();
 507         } else if c == '(' && cur_name.is_empty() {
 508             // FIXME: Support macro def with repeat.
 509             return None;
 510         } else if c.is_alphanumeric() || c == '_' {
 511             cur_name.push(c);
 512         }
 513     }
 514
 515     if !cur_name.is_empty() {
 516         register_metavariable(&mut substs, &mut result, &cur_name, dollar_count);
 517     }
 518
 519     debug!("replace_names `{}` {:?}", result, substs);
 520
 521     Some((result, substs))
 522 }
 523
 524 #[derive(Debug, Clone)]
 525 enum MacroArgKind {
 526     /// e.g., `$x: expr`.
 527     MetaVariable(Symbol, String),
 528     /// e.g., `$($foo: expr),*`
 529     Repeat(
 530         /// `()`, `[]` or `{}`.
 531         Delimiter,
 532         /// Inner arguments inside delimiters.
 533         Vec<ParsedMacroArg>,
 534         /// Something after the closing delimiter and the repeat token, if available.
 535         Option<Box<ParsedMacroArg>>,
 536         /// The repeat token. This could be one of `*`, `+` or `?`.
 537         Token,
 538     ),
 539     /// e.g., `[derive(Debug)]`
 540     Delimited(Delimiter, Vec<ParsedMacroArg>),
 541     /// A possible separator. e.g., `,` or `;`.
 542     Separator(String, String),
 543     /// Other random stuff that does not fit to other kinds.
 544     /// e.g., `== foo` in `($x: expr == foo)`.
 545     Other(String, String),
 546 }
 547
 548 fn delim_token_to_str(
 549     context: &RewriteContext<'_>,
 550     delim_token: Delimiter,
 551     shape: Shape,
 552     use_multiple_lines: bool,
 553     inner_is_empty: bool,
 554 ) -> (String, String) {
 555     let (lhs, rhs) = match delim_token {
 556         Delimiter::Parenthesis => ("(", ")"),
 557         Delimiter::Bracket => ("[", "]"),
 558         Delimiter::Brace => {
 559             if inner_is_empty || use_multiple_lines {
 560                 ("{", "}")
 561             } else {
 562                 ("{ ", " }")
 563             }
 564         }
 565         Delimiter::Invisible => unreachable!(),
 566     };
 567     if use_multiple_lines {
 568         let indent_str = shape.indent.to_string_with_newline(context.config);
 569         let nested_indent_str = shape
 570             .indent
 571             .block_indent(context.config)
 572             .to_string_with_newline(context.config);
 573         (
 574             format!("{}{}", lhs, nested_indent_str),
 575             format!("{}{}", indent_str, rhs),
 576         )
 577     } else {
 578         (lhs.to_owned(), rhs.to_owned())
 579     }
 580 }
 581
 582 impl MacroArgKind {
 583     fn starts_with_brace(&self) -> bool {
 584         matches!(
 585             *self,
 586             MacroArgKind::Repeat(Delimiter::Brace, _, _, _)
 587                 | MacroArgKind::Delimited(Delimiter::Brace, _)
 588         )
 589     }
 590
 591     fn starts_with_dollar(&self) -> bool {
 592         matches!(
 593             *self,
 594             MacroArgKind::Repeat(..) | MacroArgKind::MetaVariable(..)
 595         )
 596     }
 597
 598     fn ends_with_space(&self) -> bool {
 599         matches!(*self, MacroArgKind::Separator(..))
 600     }
 601
 602     fn has_meta_var(&self) -> bool {
 603         match *self {
 604             MacroArgKind::MetaVariable(..) => true,
 605             MacroArgKind::Repeat(_, ref args, _, _) => args.iter().any(|a| a.kind.has_meta_var()),
 606             _ => false,
 607         }
 608     }
 609
 610     fn rewrite(
 611         &self,
 612         context: &RewriteContext<'_>,
 613         shape: Shape,
 614         use_multiple_lines: bool,
 615     ) -> Option<String> {
 616         let rewrite_delimited_inner = |delim_tok, args| -> Option<(String, String, String)> {
 617             let inner = wrap_macro_args(context, args, shape)?;
 618             let (lhs, rhs) = delim_token_to_str(context, delim_tok, shape, false, inner.is_empty());
 619             if lhs.len() + inner.len() + rhs.len() <= shape.width {
 620                 return Some((lhs, inner, rhs));
 621             }
 622
 623             let (lhs, rhs) = delim_token_to_str(context, delim_tok, shape, true, false);
 624             let nested_shape = shape
 625                 .block_indent(context.config.tab_spaces())
 626                 .with_max_width(context.config);
 627             let inner = wrap_macro_args(context, args, nested_shape)?;
 628             Some((lhs, inner, rhs))
 629         };
 630
 631         match *self {
 632             MacroArgKind::MetaVariable(ty, ref name) => Some(format!("${}:{}", name, ty)),
 633             MacroArgKind::Repeat(delim_tok, ref args, ref another, ref tok) => {
 634                 let (lhs, inner, rhs) = rewrite_delimited_inner(delim_tok, args)?;
 635                 let another = another
 636                     .as_ref()
 637                     .and_then(|a| a.rewrite(context, shape, use_multiple_lines))
 638                     .unwrap_or_else(|| "".to_owned());
 639                 let repeat_tok = pprust::token_to_string(tok);
 640
 641                 Some(format!("${}{}{}{}{}", lhs, inner, rhs, another, repeat_tok))
 642             }
 643             MacroArgKind::Delimited(delim_tok, ref args) => {
 644                 rewrite_delimited_inner(delim_tok, args)
 645                     .map(|(lhs, inner, rhs)| format!("{}{}{}", lhs, inner, rhs))
 646             }
 647             MacroArgKind::Separator(ref sep, ref prefix) => Some(format!("{}{} ", prefix, sep)),
 648             MacroArgKind::Other(ref inner, ref prefix) => Some(format!("{}{}", prefix, inner)),
 649         }
 650     }
 651 }
 652
 653 #[derive(Debug, Clone)]
 654 struct ParsedMacroArg {
 655     kind: MacroArgKind,
 656 }
 657
 658 impl ParsedMacroArg {
 659     fn rewrite(
 660         &self,
 661         context: &RewriteContext<'_>,
 662         shape: Shape,
 663         use_multiple_lines: bool,
 664     ) -> Option<String> {
 665         self.kind.rewrite(context, shape, use_multiple_lines)
 666     }
 667 }
 668
 669 /// Parses macro arguments on macro def.
 670 struct MacroArgParser {
 671     /// Either a name of the next metavariable, a separator, or junk.
 672     buf: String,
 673     /// The first token of the current buffer.
 674     start_tok: Token,
 675     /// `true` if we are parsing a metavariable or a repeat.
 676     is_meta_var: bool,
 677     /// The last token parsed.
 678     last_tok: Token,
 679     /// Holds the parsed arguments.
 680     result: Vec<ParsedMacroArg>,
 681 }
 682
 683 fn last_tok(tt: &TokenTree) -> Token {
 684     match *tt {
 685         TokenTree::Token(ref t) => t.clone(),
 686         TokenTree::Delimited(delim_span, delim, _) => Token {
 687             kind: TokenKind::CloseDelim(delim),
 688             span: delim_span.close,
 689         },
 690     }
 691 }
 692
 693 impl MacroArgParser {
 694     fn new() -> MacroArgParser {
 695         MacroArgParser {
 696             buf: String::new(),
 697             is_meta_var: false,
 698             last_tok: Token {
 699                 kind: TokenKind::Eof,
 700                 span: DUMMY_SP,
 701             },
 702             start_tok: Token {
 703                 kind: TokenKind::Eof,
 704                 span: DUMMY_SP,
 705             },
 706             result: vec![],
 707         }
 708     }
 709
 710     fn set_last_tok(&mut self, tok: &TokenTree) {
 711         self.last_tok = last_tok(tok);
 712     }
 713
 714     fn add_separator(&mut self) {
 715         let prefix = if self.need_space_prefix() {
 716             " ".to_owned()
 717         } else {
 718             "".to_owned()
 719         };
 720         self.result.push(ParsedMacroArg {
 721             kind: MacroArgKind::Separator(self.buf.clone(), prefix),
 722         });
 723         self.buf.clear();
 724     }
 725
 726     fn add_other(&mut self) {
 727         let prefix = if self.need_space_prefix() {
 728             " ".to_owned()
 729         } else {
 730             "".to_owned()
 731         };
 732         self.result.push(ParsedMacroArg {
 733             kind: MacroArgKind::Other(self.buf.clone(), prefix),
 734         });
 735         self.buf.clear();
 736     }
 737
 738     fn add_meta_variable(&mut self, iter: &mut Cursor) -> Option<()> {
 739         match iter.next() {
 740             Some(TokenTree::Token(Token {
 741                 kind: TokenKind::Ident(name, _),
 742                 ..
 743             })) => {
 744                 self.result.push(ParsedMacroArg {
 745                     kind: MacroArgKind::MetaVariable(name, self.buf.clone()),
 746                 });
 747
 748                 self.buf.clear();
 749                 self.is_meta_var = false;
 750                 Some(())
 751             }
 752             _ => None,
 753         }
 754     }
 755
 756     fn add_delimited(&mut self, inner: Vec<ParsedMacroArg>, delim: Delimiter) {
 757         self.result.push(ParsedMacroArg {
 758             kind: MacroArgKind::Delimited(delim, inner),
 759         });
 760     }
 761
 762     // $($foo: expr),?
 763     fn add_repeat(
 764         &mut self,
 765         inner: Vec<ParsedMacroArg>,
 766         delim: Delimiter,
 767         iter: &mut Cursor,
 768     ) -> Option<()> {
 769         let mut buffer = String::new();
 770         let mut first = true;
 771
 772         // Parse '*', '+' or '?.
 773         for tok in iter {
 774             self.set_last_tok(&tok);
 775             if first {
 776                 first = false;
 777             }
 778
 779             match tok {
 780                 TokenTree::Token(Token {
 781                     kind: TokenKind::BinOp(BinOpToken::Plus),
 782                     ..
 783                 })
 784                 | TokenTree::Token(Token {
 785                     kind: TokenKind::Question,
 786                     ..
 787                 })
 788                 | TokenTree::Token(Token {
 789                     kind: TokenKind::BinOp(BinOpToken::Star),
 790                     ..
 791                 }) => {
 792                     break;
 793                 }
 794                 TokenTree::Token(ref t) => {
 795                     buffer.push_str(&pprust::token_to_string(t));
 796                 }
 797                 _ => return None,
 798             }
 799         }
 800
 801         // There could be some random stuff between ')' and '*', '+' or '?'.
 802         let another = if buffer.trim().is_empty() {
 803             None
 804         } else {
 805             Some(Box::new(ParsedMacroArg {
 806                 kind: MacroArgKind::Other(buffer, "".to_owned()),
 807             }))
 808         };
 809
 810         self.result.push(ParsedMacroArg {
 811             kind: MacroArgKind::Repeat(delim, inner, another, self.last_tok.clone()),
 812         });
 813         Some(())
 814     }
 815
 816     fn update_buffer(&mut self, t: &Token) {
 817         if self.buf.is_empty() {
 818             self.start_tok = t.clone();
 819         } else {
 820             let needs_space = match next_space(&self.last_tok.kind) {
 821                 SpaceState::Ident => ident_like(t),
 822                 SpaceState::Punctuation => !ident_like(t),
 823                 SpaceState::Always => true,
 824                 SpaceState::Never => false,
 825             };
 826             if force_space_before(&t.kind) || needs_space {
 827                 self.buf.push(' ');
 828             }
 829         }
 830
 831         self.buf.push_str(&pprust::token_to_string(t));
 832     }
 833
 834     fn need_space_prefix(&self) -> bool {
 835         if self.result.is_empty() {
 836             return false;
 837         }
 838
 839         let last_arg = self.result.last().unwrap();
 840         if let MacroArgKind::MetaVariable(..) = last_arg.kind {
 841             if ident_like(&self.start_tok) {
 842                 return true;
 843             }
 844             if self.start_tok.kind == TokenKind::Colon {
 845                 return true;
 846             }
 847         }
 848
 849         if force_space_before(&self.start_tok.kind) {
 850             return true;
 851         }
 852
 853         false
 854     }
 855
 856     /// Returns a collection of parsed macro def's arguments.
 857     fn parse(mut self, tokens: TokenStream) -> Option<Vec<ParsedMacroArg>> {
 858         let mut iter = tokens.into_trees();
 859
 860         while let Some(tok) = iter.next() {
 861             match tok {
 862                 TokenTree::Token(Token {
 863                     kind: TokenKind::Dollar,
 864                     span,
 865                 }) => {
 866                     // We always want to add a separator before meta variables.
 867                     if !self.buf.is_empty() {
 868                         self.add_separator();
 869                     }
 870
 871                     // Start keeping the name of this metavariable in the buffer.
 872                     self.is_meta_var = true;
 873                     self.start_tok = Token {
 874                         kind: TokenKind::Dollar,
 875                         span,
 876                     };
 877                 }
 878                 TokenTree::Token(Token {
 879                     kind: TokenKind::Colon,
 880                     ..
 881                 }) if self.is_meta_var => {
 882                     self.add_meta_variable(&mut iter)?;
 883                 }
 884                 TokenTree::Token(ref t) => self.update_buffer(t),
 885                 TokenTree::Delimited(_delimited_span, delimited, ref tts) => {
 886                     if !self.buf.is_empty() {
 887                         if next_space(&self.last_tok.kind) == SpaceState::Always {
 888                             self.add_separator();
 889                         } else {
 890                             self.add_other();
 891                         }
 892                     }
 893
 894                     // Parse the stuff inside delimiters.
 895                     let parser = MacroArgParser::new();
 896                     let delimited_arg = parser.parse(tts.clone())?;
 897
 898                     if self.is_meta_var {
 899                         self.add_repeat(delimited_arg, delimited, &mut iter)?;
 900                         self.is_meta_var = false;
 901                     } else {
 902                         self.add_delimited(delimited_arg, delimited);
 903                     }
 904                 }
 905             }
 906
 907             self.set_last_tok(&tok);
 908         }
 909
 910         // We are left with some stuff in the buffer. Since there is nothing
 911         // left to separate, add this as `Other`.
 912         if !self.buf.is_empty() {
 913             self.add_other();
 914         }
 915
 916         Some(self.result)
 917     }
 918 }
 919
 920 fn wrap_macro_args(
 921     context: &RewriteContext<'_>,
 922     args: &[ParsedMacroArg],
 923     shape: Shape,
 924 ) -> Option<String> {
 925     wrap_macro_args_inner(context, args, shape, false)
 926         .or_else(|| wrap_macro_args_inner(context, args, shape, true))
 927 }
 928
 929 fn wrap_macro_args_inner(
 930     context: &RewriteContext<'_>,
 931     args: &[ParsedMacroArg],
 932     shape: Shape,
 933     use_multiple_lines: bool,
 934 ) -> Option<String> {
 935     let mut result = String::with_capacity(128);
 936     let mut iter = args.iter().peekable();
 937     let indent_str = shape.indent.to_string_with_newline(context.config);
 938
 939     while let Some(arg) = iter.next() {
 940         result.push_str(&arg.rewrite(context, shape, use_multiple_lines)?);
 941
 942         if use_multiple_lines
 943             && (arg.kind.ends_with_space() || iter.peek().map_or(false, |a| a.kind.has_meta_var()))
 944         {
 945             if arg.kind.ends_with_space() {
 946                 result.pop();
 947             }
 948             result.push_str(&indent_str);
 949         } else if let Some(next_arg) = iter.peek() {
 950             let space_before_dollar =
 951                 !arg.kind.ends_with_space() && next_arg.kind.starts_with_dollar();
 952             let space_before_brace = next_arg.kind.starts_with_brace();
 953             if space_before_dollar || space_before_brace {
 954                 result.push(' ');
 955             }
 956         }
 957     }
 958
 959     if !use_multiple_lines && result.len() >= shape.width {
 960         None
 961     } else {
 962         Some(result)
 963     }
 964 }
 965
 966 // This is a bit sketchy. The token rules probably need tweaking, but it works
 967 // for some common cases. I hope the basic logic is sufficient. Note that the
 968 // meaning of some tokens is a bit different here from usual Rust, e.g., `*`
 969 // and `(`/`)` have special meaning.
 970 //
 971 // We always try and format on one line.
 972 // FIXME: Use multi-line when every thing does not fit on one line.
 973 fn format_macro_args(
 974     context: &RewriteContext<'_>,
 975     token_stream: TokenStream,
 976     shape: Shape,
 977 ) -> Option<String> {
 978     if !context.config.format_macro_matchers() {
 979         let span = span_for_token_stream(&token_stream);
 980         return Some(match span {
 981             Some(span) => context.snippet(span).to_owned(),
 982             None => String::new(),
 983         });
 984     }
 985     let parsed_args = MacroArgParser::new().parse(token_stream)?;
 986     wrap_macro_args(context, &parsed_args, shape)
 987 }
 988
 989 fn span_for_token_stream(token_stream: &TokenStream) -> Option<Span> {
 990     token_stream.trees().next().map(|tt| tt.span())
 991 }
 992
 993 // We should insert a space if the next token is a:
 994 #[derive(Copy, Clone, PartialEq)]
 995 enum SpaceState {
 996     Never,
 997     Punctuation,
 998     Ident, // Or ident/literal-like thing.
 999     Always,
1000 }
1001
1002 fn force_space_before(tok: &TokenKind) -> bool {
1003     debug!("tok: force_space_before {:?}", tok);
1004
1005     match tok {
1006         TokenKind::Eq
1007         | TokenKind::Lt
1008         | TokenKind::Le
1009         | TokenKind::EqEq
1010         | TokenKind::Ne
1011         | TokenKind::Ge
1012         | TokenKind::Gt
1013         | TokenKind::AndAnd
1014         | TokenKind::OrOr
1015         | TokenKind::Not
1016         | TokenKind::Tilde
1017         | TokenKind::BinOpEq(_)
1018         | TokenKind::At
1019         | TokenKind::RArrow
1020         | TokenKind::LArrow
1021         | TokenKind::FatArrow
1022         | TokenKind::BinOp(_)
1023         | TokenKind::Pound
1024         | TokenKind::Dollar => true,
1025         _ => false,
1026     }
1027 }
1028
1029 fn ident_like(tok: &Token) -> bool {
1030     matches!(
1031         tok.kind,
1032         TokenKind::Ident(..) | TokenKind::Literal(..) | TokenKind::Lifetime(_)
1033     )
1034 }
1035
1036 fn next_space(tok: &TokenKind) -> SpaceState {
1037     debug!("next_space: {:?}", tok);
1038
1039     match tok {
1040         TokenKind::Not
1041         | TokenKind::BinOp(BinOpToken::And)
1042         | TokenKind::Tilde
1043         | TokenKind::At
1044         | TokenKind::Comma
1045         | TokenKind::Dot
1046         | TokenKind::DotDot
1047         | TokenKind::DotDotDot
1048         | TokenKind::DotDotEq
1049         | TokenKind::Question => SpaceState::Punctuation,
1050
1051         TokenKind::ModSep
1052         | TokenKind::Pound
1053         | TokenKind::Dollar
1054         | TokenKind::OpenDelim(_)
1055         | TokenKind::CloseDelim(_) => SpaceState::Never,
1056
1057         TokenKind::Literal(..) | TokenKind::Ident(..) | TokenKind::Lifetime(_) => SpaceState::Ident,
1058
1059         _ => SpaceState::Always,
1060     }
1061 }
1062
1063 /// Tries to convert a macro use into a short hand try expression. Returns `None`
1064 /// when the macro is not an instance of `try!` (or parsing the inner expression
1065 /// failed).
1066 pub(crate) fn convert_try_mac(
1067     mac: &ast::MacCall,
1068     context: &RewriteContext<'_>,
1069 ) -> Option<ast::Expr> {
1070     let path = &pprust::path_to_string(&mac.path);
1071     if path == "try" || path == "r#try" {
1072         let ts = mac.args.inner_tokens();
1073
1074         Some(ast::Expr {
1075             id: ast::NodeId::root(), // dummy value
1076             kind: ast::ExprKind::Try(parse_expr(context, ts)?),
1077             span: mac.span(), // incorrect span, but shouldn't matter too much
1078             attrs: ast::AttrVec::new(),
1079             tokens: None,
1080         })
1081     } else {
1082         None
1083     }
1084 }
1085
1086 pub(crate) fn macro_style(mac: &ast::MacCall, context: &RewriteContext<'_>) -> Delimiter {
1087     let snippet = context.snippet(mac.span());
1088     let paren_pos = snippet.find_uncommented("(").unwrap_or(usize::max_value());
1089     let bracket_pos = snippet.find_uncommented("[").unwrap_or(usize::max_value());
1090     let brace_pos = snippet.find_uncommented("{").unwrap_or(usize::max_value());
1091
1092     if paren_pos < bracket_pos && paren_pos < brace_pos {
1093         Delimiter::Parenthesis
1094     } else if bracket_pos < brace_pos {
1095         Delimiter::Bracket
1096     } else {
1097         Delimiter::Brace
1098     }
1099 }
1100
1101 // A very simple parser that just parses a macros 2.0 definition into its branches.
1102 // Currently we do not attempt to parse any further than that.
1103 #[derive(new)]
1104 struct MacroParser {
1105     toks: Cursor,
1106 }
1107
1108 impl MacroParser {
1109     // (`(` ... `)` `=>` `{` ... `}`)*
1110     fn parse(&mut self) -> Option<Macro> {
1111         let mut branches = vec![];
1112         while self.toks.look_ahead(1).is_some() {
1113             branches.push(self.parse_branch()?);
1114         }
1115
1116         Some(Macro { branches })
1117     }
1118
1119     // `(` ... `)` `=>` `{` ... `}`
1120     fn parse_branch(&mut self) -> Option<MacroBranch> {
1121         let tok = self.toks.next()?;
1122         let (lo, args_paren_kind) = match tok {
1123             TokenTree::Token(..) => return None,
1124             TokenTree::Delimited(delimited_span, d, _) => (delimited_span.open.lo(), d),
1125         };
1126         let args = TokenStream::new(vec![(tok, Spacing::Joint)]);
1127         match self.toks.next()? {
1128             TokenTree::Token(Token {
1129                 kind: TokenKind::FatArrow,
1130                 ..
1131             }) => {}
1132             _ => return None,
1133         }
1134         let (mut hi, body, whole_body) = match self.toks.next()? {
1135             TokenTree::Token(..) => return None,
1136             TokenTree::Delimited(delimited_span, ..) => {
1137                 let data = delimited_span.entire().data();
1138                 (
1139                     data.hi,
1140                     Span::new(
1141                         data.lo + BytePos(1),
1142                         data.hi - BytePos(1),
1143                         data.ctxt,
1144                         data.parent,
1145                     ),
1146                     delimited_span.entire(),
1147                 )
1148             }
1149         };
1150         if let Some(TokenTree::Token(Token {
1151             kind: TokenKind::Semi,
1152             span,
1153         })) = self.toks.look_ahead(0)
1154         {
1155             hi = span.hi();
1156             self.toks.next();
1157         }
1158         Some(MacroBranch {
1159             span: mk_sp(lo, hi),
1160             args_paren_kind,
1161             args,
1162             body,
1163             whole_body,
1164         })
1165     }
1166 }
1167
1168 // A parsed macros 2.0 macro definition.
1169 struct Macro {
1170     branches: Vec<MacroBranch>,
1171 }
1172
1173 // FIXME: it would be more efficient to use references to the token streams
1174 // rather than clone them, if we can make the borrowing work out.
1175 struct MacroBranch {
1176     span: Span,
1177     args_paren_kind: Delimiter,
1178     args: TokenStream,
1179     body: Span,
1180     whole_body: Span,
1181 }
1182
1183 impl MacroBranch {
1184     fn rewrite(
1185         &self,
1186         context: &RewriteContext<'_>,
1187         shape: Shape,
1188         multi_branch_style: bool,
1189     ) -> Option<String> {
1190         // Only attempt to format function-like macros.
1191         if self.args_paren_kind != Delimiter::Parenthesis {
1192             // FIXME(#1539): implement for non-sugared macros.
1193             return None;
1194         }
1195
1196         // 5 = " => {"
1197         let mut result = format_macro_args(context, self.args.clone(), shape.sub_width(5)?)?;
1198
1199         if multi_branch_style {
1200             result += " =>";
1201         }
1202
1203         if !context.config.format_macro_bodies() {
1204             result += " ";
1205             result += context.snippet(self.whole_body);
1206             return Some(result);
1207         }
1208
1209         // The macro body is the most interesting part. It might end up as various
1210         // AST nodes, but also has special variables (e.g, `$foo`) which can't be
1211         // parsed as regular Rust code (and note that these can be escaped using
1212         // `$$`). We'll try and format like an AST node, but we'll substitute
1213         // variables for new names with the same length first.
1214
1215         let old_body = context.snippet(self.body).trim();
1216         let (body_str, substs) = replace_names(old_body)?;
1217         let has_block_body = old_body.starts_with('{');
1218
1219         let mut config = context.config.clone();
1220         config.set().hide_parse_errors(true);
1221
1222         result += " {";
1223
1224         let body_indent = if has_block_body {
1225             shape.indent
1226         } else {
1227             shape.indent.block_indent(&config)
1228         };
1229         let new_width = config.max_width() - body_indent.width();
1230         config.set().max_width(new_width);
1231
1232         // First try to format as items, then as statements.
1233         let new_body_snippet = match crate::format_snippet(&body_str, &config, true) {
1234             Some(new_body) => new_body,
1235             None => {
1236                 let new_width = new_width + config.tab_spaces();
1237                 config.set().max_width(new_width);
1238                 match crate::format_code_block(&body_str, &config, true) {
1239                     Some(new_body) => new_body,
1240                     None => return None,
1241                 }
1242             }
1243         };
1244         let new_body = wrap_str(
1245             new_body_snippet.snippet.to_string(),
1246             config.max_width(),
1247             shape,
1248         )?;
1249
1250         // Indent the body since it is in a block.
1251         let indent_str = body_indent.to_string(&config);
1252         let mut new_body = LineClasses::new(new_body.trim_end())
1253             .enumerate()
1254             .fold(
1255                 (String::new(), true),
1256                 |(mut s, need_indent), (i, (kind, ref l))| {
1257                     if !is_empty_line(l)
1258                         && need_indent
1259                         && !new_body_snippet.is_line_non_formatted(i + 1)
1260                     {
1261                         s += &indent_str;
1262                     }
1263                     (s + l + "\n", indent_next_line(kind, l, &config))
1264                 },
1265             )
1266             .0;
1267
1268         // Undo our replacement of macro variables.
1269         // FIXME: this could be *much* more efficient.
1270         for (old, new) in &substs {
1271             if old_body.contains(new) {
1272                 debug!("rewrite_macro_def: bailing matching variable: `{}`", new);
1273                 return None;
1274             }
1275             new_body = new_body.replace(new, old);
1276         }
1277
1278         if has_block_body {
1279             result += new_body.trim();
1280         } else if !new_body.is_empty() {
1281             result += "\n";
1282             result += &new_body;
1283             result += &shape.indent.to_string(&config);
1284         }
1285
1286         result += "}";
1287
1288         Some(result)
1289     }
1290 }
1291
1292 /// Format `lazy_static!` from <https://crates.io/crates/lazy_static>.
1293 ///
1294 /// # Expected syntax
1295 ///
1296 /// ```text
1297 /// lazy_static! {
1298 ///     [pub] static ref NAME_1: TYPE_1 = EXPR_1;
1299 ///     [pub] static ref NAME_2: TYPE_2 = EXPR_2;
1300 ///     ...
1301 ///     [pub] static ref NAME_N: TYPE_N = EXPR_N;
1302 /// }
1303 /// ```
1304 fn format_lazy_static(
1305     context: &RewriteContext<'_>,
1306     shape: Shape,
1307     ts: TokenStream,
1308 ) -> Option<String> {
1309     let mut result = String::with_capacity(1024);
1310     let nested_shape = shape
1311         .block_indent(context.config.tab_spaces())
1312         .with_max_width(context.config);
1313
1314     result.push_str("lazy_static! {");
1315     result.push_str(&nested_shape.indent.to_string_with_newline(context.config));
1316
1317     let parsed_elems = parse_lazy_static(context, ts)?;
1318     let last = parsed_elems.len() - 1;
1319     for (i, (vis, id, ty, expr)) in parsed_elems.iter().enumerate() {
1320         // Rewrite as a static item.
1321         let vis = crate::utils::format_visibility(context, vis);
1322         let mut stmt = String::with_capacity(128);
1323         stmt.push_str(&format!(
1324             "{}static ref {}: {} =",
1325             vis,
1326             id,
1327             ty.rewrite(context, nested_shape)?
1328         ));
1329         result.push_str(&rewrite_assign_rhs(
1330             context,
1331             stmt,
1332             &*expr,
1333             &RhsAssignKind::Expr(&expr.kind, expr.span),
1334             nested_shape.sub_width(1)?,
1335         )?);
1336         result.push(';');
1337         if i != last {
1338             result.push_str(&nested_shape.indent.to_string_with_newline(context.config));
1339         }
1340     }
1341
1342     result.push_str(&shape.indent.to_string_with_newline(context.config));
1343     result.push('}');
1344
1345     Some(result)
1346 }
1347
1348 fn rewrite_macro_with_items(
1349     context: &RewriteContext<'_>,
1350     items: &[MacroArg],
1351     macro_name: &str,
1352     shape: Shape,
1353     style: Delimiter,
1354     position: MacroPosition,
1355     span: Span,
1356 ) -> Option<String> {
1357     let (opener, closer) = match style {
1358         Delimiter::Parenthesis => ("(", ")"),
1359         Delimiter::Bracket => ("[", "]"),
1360         Delimiter::Brace => (" {", "}"),
1361         _ => return None,
1362     };
1363     let trailing_semicolon = match style {
1364         Delimiter::Parenthesis | Delimiter::Bracket if position == MacroPosition::Item => ";",
1365         _ => "",
1366     };
1367
1368     let mut visitor = FmtVisitor::from_context(context);
1369     visitor.block_indent = shape.indent.block_indent(context.config);
1370     visitor.last_pos = context.snippet_provider.span_after(span, opener.trim());
1371     for item in items {
1372         let item = match item {
1373             MacroArg::Item(item) => item,
1374             _ => return None,
1375         };
1376         visitor.visit_item(item);
1377     }
1378
1379     let mut result = String::with_capacity(256);
1380     result.push_str(macro_name);
1381     result.push_str(opener);
1382     result.push_str(&visitor.block_indent.to_string_with_newline(context.config));
1383     result.push_str(visitor.buffer.trim());
1384     result.push_str(&shape.indent.to_string_with_newline(context.config));
1385     result.push_str(closer);
1386     result.push_str(trailing_semicolon);
1387     Some(result)
1388 }