src/visitor.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use std::cmp;
  12
  13 use syntax::{ast, ptr, visit};
  14 use syntax::codemap::{self, CodeMap, Span, BytePos};
  15 use syntax::parse::ParseSess;
  16
  17 use strings::string_buffer::StringBuffer;
  18
  19 use {Indent, Shape};
  20 use utils;
  21 use codemap::{LineRangeUtils, SpanUtils};
  22 use comment::FindUncommented;
  23 use config::Config;
  24 use rewrite::{Rewrite, RewriteContext};
  25 use comment::rewrite_comment;
  26 use macros::{rewrite_macro, MacroPosition};
  27 use items::{rewrite_static, rewrite_associated_type, rewrite_associated_impl_type,
  28             rewrite_type_alias, format_impl, format_trait};
  29
  30 fn is_use_item(item: &ast::Item) -> bool {
  31     match item.node {
  32         ast::ItemKind::Use(_) => true,
  33         _ => false,
  34     }
  35 }
  36
  37 fn item_bound(item: &ast::Item) -> Span {
  38     item.attrs
  39         .iter()
  40         .map(|attr| attr.span)
  41         .fold(item.span, |bound, span| {
  42             Span {
  43                 lo: cmp::min(bound.lo, span.lo),
  44                 hi: cmp::max(bound.hi, span.hi),
  45                 expn_id: span.expn_id,
  46             }
  47         })
  48 }
  49
  50 pub struct FmtVisitor<'a> {
  51     pub parse_session: &'a ParseSess,
  52     pub codemap: &'a CodeMap,
  53     pub buffer: StringBuffer,
  54     pub last_pos: BytePos,
  55     // FIXME: use an RAII util or closure for indenting
  56     pub block_indent: Indent,
  57     pub config: &'a Config,
  58     pub failed: bool,
  59 }
  60
  61 impl<'a> FmtVisitor<'a> {
  62     fn visit_stmt(&mut self, stmt: &ast::Stmt) {
  63         debug!("visit_stmt: {:?} {:?}",
  64                self.codemap.lookup_char_pos(stmt.span.lo),
  65                self.codemap.lookup_char_pos(stmt.span.hi));
  66
  67         // FIXME(#434): Move this check to somewhere more central, eg Rewrite.
  68         if !self.config
  69                .file_lines()
  70                .intersects(&self.codemap.lookup_line_range(stmt.span)) {
  71             return;
  72         }
  73
  74         match stmt.node {
  75             ast::StmtKind::Item(ref item) => {
  76                 self.visit_item(item);
  77             }
  78             ast::StmtKind::Local(..) |
  79             ast::StmtKind::Expr(..) |
  80             ast::StmtKind::Semi(..) => {
  81                 let rewrite =
  82                     stmt.rewrite(&self.get_context(),
  83                                  Shape::indented(self.block_indent, self.config));
  84                 self.push_rewrite(stmt.span, rewrite);
  85             }
  86             ast::StmtKind::Mac(ref mac) => {
  87                 let (ref mac, _macro_style, _) = **mac;
  88                 self.visit_mac(mac, None, MacroPosition::Statement);
  89                 self.format_missing(stmt.span.hi);
  90             }
  91         }
  92     }
  93
  94     pub fn visit_block(&mut self, b: &ast::Block) {
  95         debug!("visit_block: {:?} {:?}",
  96                self.codemap.lookup_char_pos(b.span.lo),
  97                self.codemap.lookup_char_pos(b.span.hi));
  98
  99         // Check if this block has braces.
 100         let snippet = self.snippet(b.span);
 101         let has_braces = snippet.starts_with('{') || snippet.starts_with("unsafe");
 102         let brace_compensation = if has_braces { BytePos(1) } else { BytePos(0) };
 103
 104         self.last_pos = self.last_pos + brace_compensation;
 105         self.block_indent = self.block_indent.block_indent(self.config);
 106         self.buffer.push_str("{");
 107
 108         for stmt in &b.stmts {
 109             self.visit_stmt(stmt)
 110         }
 111
 112         if !b.stmts.is_empty() {
 113             if let Some(expr) = utils::stmt_expr(&b.stmts[b.stmts.len() - 1]) {
 114                 if utils::semicolon_for_expr(expr) {
 115                     self.buffer.push_str(";");
 116                 }
 117             }
 118         }
 119
 120         // FIXME: we should compress any newlines here to just one
 121         self.format_missing_with_indent(source!(self, b.span).hi - brace_compensation);
 122         self.close_block();
 123         self.last_pos = source!(self, b.span).hi;
 124     }
 125
 126     // FIXME: this is a terrible hack to indent the comments between the last
 127     // item in the block and the closing brace to the block's level.
 128     // The closing brace itself, however, should be indented at a shallower
 129     // level.
 130     fn close_block(&mut self) {
 131         let total_len = self.buffer.len;
 132         let chars_too_many = if self.config.hard_tabs() {
 133             1
 134         } else {
 135             self.config.tab_spaces()
 136         };
 137         self.buffer.truncate(total_len - chars_too_many);
 138         self.buffer.push_str("}");
 139         self.block_indent = self.block_indent.block_unindent(self.config);
 140     }
 141
 142     // Note that this only gets called for function definitions. Required methods
 143     // on traits do not get handled here.
 144     fn visit_fn(&mut self,
 145                 fk: visit::FnKind,
 146                 fd: &ast::FnDecl,
 147                 s: Span,
 148                 _: ast::NodeId,
 149                 defaultness: ast::Defaultness) {
 150         let indent = self.block_indent;
 151         let block;
 152         let rewrite = match fk {
 153             visit::FnKind::ItemFn(ident, generics, unsafety, constness, abi, vis, b) => {
 154                 block = b;
 155                 self.rewrite_fn(indent,
 156                                 ident,
 157                                 fd,
 158                                 generics,
 159                                 unsafety,
 160                                 constness.node,
 161                                 defaultness,
 162                                 abi,
 163                                 vis,
 164                                 codemap::mk_sp(s.lo, b.span.lo),
 165                                 &b)
 166             }
 167             visit::FnKind::Method(ident, sig, vis, b) => {
 168                 block = b;
 169                 self.rewrite_fn(indent,
 170                                 ident,
 171                                 fd,
 172                                 &sig.generics,
 173                                 sig.unsafety,
 174                                 sig.constness.node,
 175                                 defaultness,
 176                                 sig.abi,
 177                                 vis.unwrap_or(&ast::Visibility::Inherited),
 178                                 codemap::mk_sp(s.lo, b.span.lo),
 179                                 &b)
 180             }
 181             visit::FnKind::Closure(_) => unreachable!(),
 182         };
 183
 184         if let Some(fn_str) = rewrite {
 185             self.format_missing_with_indent(source!(self, s).lo);
 186             self.buffer.push_str(&fn_str);
 187             if let Some(c) = fn_str.chars().last() {
 188                 if c == '}' {
 189                     self.last_pos = source!(self, block.span).hi;
 190                     return;
 191                 }
 192             }
 193         } else {
 194             self.format_missing(source!(self, block.span).lo);
 195         }
 196
 197         self.last_pos = source!(self, block.span).lo;
 198         self.visit_block(block)
 199     }
 200
 201     pub fn visit_item(&mut self, item: &ast::Item) {
 202         // This is where we bail out if there is a skip attribute. This is only
 203         // complex in the module case. It is complex because the module could be
 204         // in a separate file and there might be attributes in both files, but
 205         // the AST lumps them all together.
 206         match item.node {
 207             ast::ItemKind::Mod(ref m) => {
 208                 let outer_file = self.codemap.lookup_char_pos(item.span.lo).file;
 209                 let inner_file = self.codemap.lookup_char_pos(m.inner.lo).file;
 210                 if outer_file.name == inner_file.name {
 211                     // Module is inline, in this case we treat modules like any
 212                     // other item.
 213                     if self.visit_attrs(&item.attrs) {
 214                         self.push_rewrite(item.span, None);
 215                         return;
 216                     }
 217                 } else if utils::contains_skip(&item.attrs) {
 218                     // Module is not inline, but should be skipped.
 219                     return;
 220                 } else {
 221                     // Module is not inline and should not be skipped. We want
 222                     // to process only the attributes in the current file.
 223                     let attrs = item.attrs
 224                         .iter()
 225                         .filter_map(|a| {
 226                             let attr_file = self.codemap.lookup_char_pos(a.span.lo).file;
 227                             if attr_file.name == outer_file.name {
 228                                 Some(a.clone())
 229                             } else {
 230                                 None
 231                             }
 232                         })
 233                         .collect::<Vec<_>>();
 234                     // Assert because if we should skip it should be caught by
 235                     // the above case.
 236                     assert!(!self.visit_attrs(&attrs));
 237                 }
 238             }
 239             _ => {
 240                 if self.visit_attrs(&item.attrs) {
 241                     self.push_rewrite(item.span, None);
 242                     return;
 243                 }
 244             }
 245         }
 246
 247         match item.node {
 248             ast::ItemKind::Use(ref vp) => {
 249                 self.format_import(&item.vis, vp, item.span);
 250             }
 251             ast::ItemKind::Impl(..) => {
 252                 self.format_missing_with_indent(source!(self, item.span).lo);
 253                 let snippet = self.get_context().snippet(item.span);
 254                 let where_span_end =
 255                     snippet
 256                         .find_uncommented("{")
 257                         .map(|x| (BytePos(x as u32)) + source!(self, item.span).lo);
 258                 if let Some(impl_str) = format_impl(&self.get_context(),
 259                                                     item,
 260                                                     self.block_indent,
 261                                                     where_span_end) {
 262                     self.buffer.push_str(&impl_str);
 263                     self.last_pos = source!(self, item.span).hi;
 264                 }
 265             }
 266             ast::ItemKind::Trait(..) => {
 267                 self.format_missing_with_indent(item.span.lo);
 268                 if let Some(trait_str) = format_trait(&self.get_context(),
 269                                                       item,
 270                                                       self.block_indent) {
 271                     self.buffer.push_str(&trait_str);
 272                     self.last_pos = source!(self, item.span).hi;
 273                 }
 274             }
 275             ast::ItemKind::ExternCrate(_) => {
 276                 self.format_missing_with_indent(source!(self, item.span).lo);
 277                 let new_str = self.snippet(item.span);
 278                 self.buffer.push_str(&new_str);
 279                 self.last_pos = source!(self, item.span).hi;
 280             }
 281             ast::ItemKind::Struct(ref def, ref generics) => {
 282                 let rewrite = {
 283                     let indent = self.block_indent;
 284                     let context = self.get_context();
 285                     ::items::format_struct(&context,
 286                                            "struct ",
 287                                            item.ident,
 288                                            &item.vis,
 289                                            def,
 290                                            Some(generics),
 291                                            item.span,
 292                                            indent,
 293                                            None)
 294                         .map(|s| match *def {
 295                                  ast::VariantData::Tuple(..) => s + ";",
 296                                  _ => s,
 297                              })
 298                 };
 299                 self.push_rewrite(item.span, rewrite);
 300             }
 301             ast::ItemKind::Enum(ref def, ref generics) => {
 302                 self.format_missing_with_indent(source!(self, item.span).lo);
 303                 self.visit_enum(item.ident, &item.vis, def, generics, item.span);
 304                 self.last_pos = source!(self, item.span).hi;
 305             }
 306             ast::ItemKind::Mod(ref module) => {
 307                 self.format_missing_with_indent(source!(self, item.span).lo);
 308                 self.format_mod(module, &item.vis, item.span, item.ident);
 309             }
 310             ast::ItemKind::Mac(ref mac) => {
 311                 self.visit_mac(mac, Some(item.ident), MacroPosition::Item);
 312             }
 313             ast::ItemKind::ForeignMod(ref foreign_mod) => {
 314                 self.format_missing_with_indent(source!(self, item.span).lo);
 315                 self.format_foreign_mod(foreign_mod, item.span);
 316             }
 317             ast::ItemKind::Static(ref ty, mutability, ref expr) => {
 318                 let rewrite = rewrite_static("static",
 319                                              &item.vis,
 320                                              item.ident,
 321                                              ty,
 322                                              mutability,
 323                                              Some(expr),
 324                                              self.block_indent,
 325                                              &self.get_context());
 326                 self.push_rewrite(item.span, rewrite);
 327             }
 328             ast::ItemKind::Const(ref ty, ref expr) => {
 329                 let rewrite = rewrite_static("const",
 330                                              &item.vis,
 331                                              item.ident,
 332                                              ty,
 333                                              ast::Mutability::Immutable,
 334                                              Some(expr),
 335                                              self.block_indent,
 336                                              &self.get_context());
 337                 self.push_rewrite(item.span, rewrite);
 338             }
 339             ast::ItemKind::DefaultImpl(..) => {
 340                 // FIXME(#78): format impl definitions.
 341             }
 342             ast::ItemKind::Fn(ref decl, unsafety, constness, abi, ref generics, ref body) => {
 343                 self.visit_fn(visit::FnKind::ItemFn(item.ident,
 344                                                     generics,
 345                                                     unsafety,
 346                                                     constness,
 347                                                     abi,
 348                                                     &item.vis,
 349                                                     body),
 350                               decl,
 351                               item.span,
 352                               item.id,
 353                               ast::Defaultness::Final)
 354             }
 355             ast::ItemKind::Ty(ref ty, ref generics) => {
 356                 let rewrite = rewrite_type_alias(&self.get_context(),
 357                                                  self.block_indent,
 358                                                  item.ident,
 359                                                  ty,
 360                                                  generics,
 361                                                  &item.vis,
 362                                                  item.span);
 363                 self.push_rewrite(item.span, rewrite);
 364             }
 365             ast::ItemKind::Union(..) => {
 366                 // FIXME(#1157): format union definitions.
 367             }
 368         }
 369     }
 370
 371     pub fn visit_trait_item(&mut self, ti: &ast::TraitItem) {
 372         if self.visit_attrs(&ti.attrs) {
 373             self.push_rewrite(ti.span, None);
 374             return;
 375         }
 376
 377         match ti.node {
 378             ast::TraitItemKind::Const(ref ty, ref expr_opt) => {
 379                 let rewrite = rewrite_static("const",
 380                                              &ast::Visibility::Inherited,
 381                                              ti.ident,
 382                                              ty,
 383                                              ast::Mutability::Immutable,
 384                                              expr_opt.as_ref(),
 385                                              self.block_indent,
 386                                              &self.get_context());
 387                 self.push_rewrite(ti.span, rewrite);
 388             }
 389             ast::TraitItemKind::Method(ref sig, None) => {
 390                 let indent = self.block_indent;
 391                 let rewrite = self.rewrite_required_fn(indent, ti.ident, sig, ti.span);
 392                 self.push_rewrite(ti.span, rewrite);
 393             }
 394             ast::TraitItemKind::Method(ref sig, Some(ref body)) => {
 395                 self.visit_fn(visit::FnKind::Method(ti.ident, sig, None, body),
 396                               &sig.decl,
 397                               ti.span,
 398                               ti.id,
 399                               ast::Defaultness::Final);
 400             }
 401             ast::TraitItemKind::Type(ref type_param_bounds, ref type_default) => {
 402                 let rewrite = rewrite_associated_type(ti.ident,
 403                                                       type_default.as_ref(),
 404                                                       Some(type_param_bounds),
 405                                                       &self.get_context(),
 406                                                       self.block_indent);
 407                 self.push_rewrite(ti.span, rewrite);
 408             }
 409             ast::TraitItemKind::Macro(ref mac) => {
 410                 self.visit_mac(mac, Some(ti.ident), MacroPosition::Item);
 411             }
 412         }
 413     }
 414
 415     pub fn visit_impl_item(&mut self, ii: &ast::ImplItem) {
 416         if self.visit_attrs(&ii.attrs) {
 417             self.push_rewrite(ii.span, None);
 418             return;
 419         }
 420
 421         match ii.node {
 422             ast::ImplItemKind::Method(ref sig, ref body) => {
 423                 self.visit_fn(visit::FnKind::Method(ii.ident, sig, Some(&ii.vis), body),
 424                               &sig.decl,
 425                               ii.span,
 426                               ii.id,
 427                               ii.defaultness);
 428             }
 429             ast::ImplItemKind::Const(ref ty, ref expr) => {
 430                 let rewrite = rewrite_static("const",
 431                                              &ii.vis,
 432                                              ii.ident,
 433                                              ty,
 434                                              ast::Mutability::Immutable,
 435                                              Some(expr),
 436                                              self.block_indent,
 437                                              &self.get_context());
 438                 self.push_rewrite(ii.span, rewrite);
 439             }
 440             ast::ImplItemKind::Type(ref ty) => {
 441                 let rewrite = rewrite_associated_impl_type(ii.ident,
 442                                                            ii.defaultness,
 443                                                            Some(ty),
 444                                                            None,
 445                                                            &self.get_context(),
 446                                                            self.block_indent);
 447                 self.push_rewrite(ii.span, rewrite);
 448             }
 449             ast::ImplItemKind::Macro(ref mac) => {
 450                 self.visit_mac(mac, Some(ii.ident), MacroPosition::Item);
 451             }
 452         }
 453     }
 454
 455     fn visit_mac(&mut self, mac: &ast::Mac, ident: Option<ast::Ident>, pos: MacroPosition) {
 456         // 1 = ;
 457         let shape = Shape::indented(self.block_indent, self.config)
 458             .sub_width(1)
 459             .unwrap();
 460         let rewrite = rewrite_macro(mac, ident, &self.get_context(), shape, pos);
 461         self.push_rewrite(mac.span, rewrite);
 462     }
 463
 464     fn push_rewrite(&mut self, span: Span, rewrite: Option<String>) {
 465         self.format_missing_with_indent(source!(self, span).lo);
 466         self.failed = match rewrite {
 467             Some(ref s) if s.rewrite(&self.get_context(),
 468                                      Shape::indented(self.block_indent, self.config))
 469                                .is_none() => true,
 470             None => true,
 471             _ => self.failed,
 472         };
 473         let result = rewrite.unwrap_or_else(|| self.snippet(span));
 474         self.buffer.push_str(&result);
 475         self.last_pos = source!(self, span).hi;
 476     }
 477
 478     pub fn from_codemap(parse_session: &'a ParseSess, config: &'a Config) -> FmtVisitor<'a> {
 479         FmtVisitor {
 480             parse_session: parse_session,
 481             codemap: parse_session.codemap(),
 482             buffer: StringBuffer::new(),
 483             last_pos: BytePos(0),
 484             block_indent: Indent::empty(),
 485             config: config,
 486             failed: false,
 487         }
 488     }
 489
 490     pub fn snippet(&self, span: Span) -> String {
 491         match self.codemap.span_to_snippet(span) {
 492             Ok(s) => s,
 493             Err(_) => {
 494                 println!("Couldn't make snippet for span {:?}->{:?}",
 495                          self.codemap.lookup_char_pos(span.lo),
 496                          self.codemap.lookup_char_pos(span.hi));
 497                 "".to_owned()
 498             }
 499         }
 500     }
 501
 502     // Returns true if we should skip the following item.
 503     pub fn visit_attrs(&mut self, attrs: &[ast::Attribute]) -> bool {
 504         if utils::contains_skip(attrs) {
 505             return true;
 506         }
 507
 508         let outers: Vec<_> = attrs
 509             .iter()
 510             .filter(|a| a.style == ast::AttrStyle::Outer)
 511             .cloned()
 512             .collect();
 513         if outers.is_empty() {
 514             return false;
 515         }
 516
 517         let first = &outers[0];
 518         self.format_missing_with_indent(source!(self, first.span).lo);
 519
 520         let rewrite = outers
 521             .rewrite(&self.get_context(),
 522                      Shape::indented(self.block_indent, self.config))
 523             .unwrap();
 524         self.buffer.push_str(&rewrite);
 525         let last = outers.last().unwrap();
 526         self.last_pos = source!(self, last.span).hi;
 527         false
 528     }
 529
 530     fn walk_mod_items(&mut self, m: &ast::Mod) {
 531         let mut items_left: &[ptr::P<ast::Item>] = &m.items;
 532         while !items_left.is_empty() {
 533             // If the next item is a `use` declaration, then extract it and any subsequent `use`s
 534             // to be potentially reordered within `format_imports`. Otherwise, just format the
 535             // next item for output.
 536             if self.config.reorder_imports() && is_use_item(&*items_left[0]) {
 537                 let reorder_imports_in_group = self.config.reorder_imports_in_group();
 538                 let mut last = self.codemap.lookup_line_range(item_bound(&items_left[0]));
 539                 let use_item_length = items_left
 540                     .iter()
 541                     .take_while(|ppi| {
 542                         is_use_item(&***ppi) &&
 543                         (!reorder_imports_in_group ||
 544                          {
 545                              let current = self.codemap.lookup_line_range(item_bound(&ppi));
 546                              let in_same_group = current.lo < last.hi + 2;
 547                              last = current;
 548                              in_same_group
 549                          })
 550                     })
 551                     .count();
 552                 let (use_items, rest) = items_left.split_at(use_item_length);
 553                 self.format_imports(use_items);
 554                 items_left = rest;
 555             } else {
 556                 // `unwrap()` is safe here because we know `items_left`
 557                 // has elements from the loop condition
 558                 let (item, rest) = items_left.split_first().unwrap();
 559                 self.visit_item(item);
 560                 items_left = rest;
 561             }
 562         }
 563     }
 564
 565     fn format_mod(&mut self, m: &ast::Mod, vis: &ast::Visibility, s: Span, ident: ast::Ident) {
 566         // Decide whether this is an inline mod or an external mod.
 567         let local_file_name = self.codemap.span_to_filename(s);
 568         let inner_span = source!(self, m.inner);
 569         let is_internal = !(inner_span.lo.0 == 0 && inner_span.hi.0 == 0) &&
 570                           local_file_name == self.codemap.span_to_filename(inner_span);
 571
 572         self.buffer.push_str(&*utils::format_visibility(vis));
 573         self.buffer.push_str("mod ");
 574         self.buffer.push_str(&ident.to_string());
 575
 576         if is_internal {
 577             self.buffer.push_str(" {");
 578             // Hackery to account for the closing }.
 579             let mod_lo = self.codemap.span_after(source!(self, s), "{");
 580             let body_snippet =
 581                 self.snippet(codemap::mk_sp(mod_lo, source!(self, m.inner).hi - BytePos(1)));
 582             let body_snippet = body_snippet.trim();
 583             if body_snippet.is_empty() {
 584                 self.buffer.push_str("}");
 585             } else {
 586                 self.last_pos = mod_lo;
 587                 self.block_indent = self.block_indent.block_indent(self.config);
 588                 self.walk_mod_items(m);
 589                 self.format_missing_with_indent(source!(self, m.inner).hi - BytePos(1));
 590                 self.close_block();
 591             }
 592             self.last_pos = source!(self, m.inner).hi;
 593         } else {
 594             self.buffer.push_str(";");
 595             self.last_pos = source!(self, s).hi;
 596         }
 597     }
 598
 599     pub fn format_separate_mod(&mut self, m: &ast::Mod) {
 600         let filemap = self.codemap.lookup_char_pos(m.inner.lo).file;
 601         self.last_pos = filemap.start_pos;
 602         self.block_indent = Indent::empty();
 603         self.walk_mod_items(m);
 604         self.format_missing_with_indent(filemap.end_pos);
 605     }
 606
 607     pub fn get_context(&self) -> RewriteContext {
 608         RewriteContext {
 609             parse_session: self.parse_session,
 610             codemap: self.codemap,
 611             config: self.config,
 612             inside_macro: false,
 613         }
 614     }
 615 }
 616
 617 impl<'a> Rewrite for [ast::Attribute] {
 618     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 619         let mut result = String::new();
 620         if self.is_empty() {
 621             return Some(result);
 622         }
 623         let indent = shape.indent.to_string(context.config);
 624
 625         for (i, a) in self.iter().enumerate() {
 626             let mut a_str = context.snippet(a.span);
 627
 628             // Write comments and blank lines between attributes.
 629             if i > 0 {
 630                 let comment = context.snippet(codemap::mk_sp(self[i - 1].span.hi, a.span.lo));
 631                 // This particular horror show is to preserve line breaks in between doc
 632                 // comments. An alternative would be to force such line breaks to start
 633                 // with the usual doc comment token.
 634                 let multi_line = a_str.starts_with("//") && comment.matches('\n').count() > 1;
 635                 let comment = comment.trim();
 636                 if !comment.is_empty() {
 637                     let comment =
 638                         try_opt!(rewrite_comment(comment,
 639                                                  false,
 640                                                  Shape::legacy(context.config.comment_width() -
 641                                                                shape.indent.width(),
 642                                                                shape.indent),
 643                                                  context.config));
 644                     result.push_str(&indent);
 645                     result.push_str(&comment);
 646                     result.push('\n');
 647                 } else if multi_line {
 648                     result.push('\n');
 649                 }
 650                 result.push_str(&indent);
 651             }
 652
 653             if a_str.starts_with("//") {
 654                 a_str = try_opt!(rewrite_comment(&a_str,
 655                                                  false,
 656                                                  Shape::legacy(context.config.comment_width() -
 657                                                                shape.indent.width(),
 658                                                                shape.indent),
 659                                                  context.config));
 660             }
 661
 662             // Write the attribute itself.
 663             result.push_str(&a_str);
 664
 665             if i < self.len() - 1 {
 666                 result.push('\n');
 667             }
 668         }
 669
 670         Some(result)
 671     }
 672 }