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 strings::string_buffer::StringBuffer;
  14 use syntax::{ast, visit};
  15 use syntax::attr::HasAttrs;
  16 use syntax::codemap::{self, BytePos, CodeMap, Pos, Span};
  17 use syntax::parse::ParseSess;
  18
  19 use {Indent, Shape, Spanned};
  20 use codemap::{LineRangeUtils, SpanUtils};
  21 use comment::{contains_comment, recover_missing_comment_in_span, CodeCharKind, CommentCodeSlices,
  22               FindUncommented};
  23 use comment::rewrite_comment;
  24 use config::{BraceStyle, Config};
  25 use items::{format_impl, format_struct, format_struct_struct, format_trait,
  26             rewrite_associated_impl_type, rewrite_associated_type, rewrite_static,
  27             rewrite_type_alias};
  28 use lists::{itemize_list, write_list, DefinitiveListTactic, ListFormatting, SeparatorPlace,
  29             SeparatorTactic};
  30 use macros::{rewrite_macro, MacroPosition};
  31 use regex::Regex;
  32 use rewrite::{Rewrite, RewriteContext};
  33 use utils::{self, contains_skip, inner_attributes, mk_sp, ptr_vec_to_ref_vec};
  34
  35 fn is_use_item(item: &ast::Item) -> bool {
  36     match item.node {
  37         ast::ItemKind::Use(_) => true,
  38         _ => false,
  39     }
  40 }
  41
  42 fn is_extern_crate(item: &ast::Item) -> bool {
  43     match item.node {
  44         ast::ItemKind::ExternCrate(..) => true,
  45         _ => false,
  46     }
  47 }
  48
  49 pub struct FmtVisitor<'a> {
  50     pub parse_session: &'a ParseSess,
  51     pub codemap: &'a CodeMap,
  52     pub buffer: StringBuffer,
  53     pub last_pos: BytePos,
  54     // FIXME: use an RAII util or closure for indenting
  55     pub block_indent: Indent,
  56     pub config: &'a Config,
  57     pub is_if_else_block: bool,
  58 }
  59
  60 impl<'a> FmtVisitor<'a> {
  61     pub fn shape(&self) -> Shape {
  62         Shape::indented(self.block_indent, self.config)
  63     }
  64
  65     fn visit_stmt(&mut self, stmt: &ast::Stmt) {
  66         debug!(
  67             "visit_stmt: {:?} {:?}",
  68             self.codemap.lookup_char_pos(stmt.span.lo()),
  69             self.codemap.lookup_char_pos(stmt.span.hi())
  70         );
  71
  72         match stmt.node {
  73             ast::StmtKind::Item(ref item) => {
  74                 self.visit_item(item);
  75             }
  76             ast::StmtKind::Local(..) | ast::StmtKind::Expr(..) | ast::StmtKind::Semi(..) => {
  77                 let rewrite = stmt.rewrite(&self.get_context(), self.shape());
  78                 self.push_rewrite(stmt.span(), rewrite)
  79             }
  80             ast::StmtKind::Mac(ref mac) => {
  81                 let (ref mac, _macro_style, ref attrs) = **mac;
  82                 if self.visit_attrs(attrs, ast::AttrStyle::Outer) {
  83                     self.push_rewrite(stmt.span(), None);
  84                 } else {
  85                     self.visit_mac(mac, None, MacroPosition::Statement);
  86                 }
  87                 self.format_missing(stmt.span.hi());
  88             }
  89         }
  90     }
  91
  92     pub fn visit_block(&mut self, b: &ast::Block, inner_attrs: Option<&[ast::Attribute]>) {
  93         debug!(
  94             "visit_block: {:?} {:?}",
  95             self.codemap.lookup_char_pos(b.span.lo()),
  96             self.codemap.lookup_char_pos(b.span.hi())
  97         );
  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         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 109             if let Some(first_stmt) = b.stmts.first() {
 110                 let attr_lo = inner_attrs
 111                     .and_then(|attrs| {
 112                         inner_attributes(attrs).first().map(|attr| attr.span.lo())
 113                     })
 114                     .or_else(|| {
 115                         // Attributes for an item in a statement position
 116                         // do not belong to the statement. (rust-lang/rust#34459)
 117                         if let ast::StmtKind::Item(ref item) = first_stmt.node {
 118                             item.attrs.first()
 119                         } else {
 120                             first_stmt.attrs().first()
 121                         }.and_then(|attr| {
 122                             // Some stmts can have embedded attributes.
 123                             // e.g. `match { #![attr] ... }`
 124                             let attr_lo = attr.span.lo();
 125                             if attr_lo < first_stmt.span.lo() {
 126                                 Some(attr_lo)
 127                             } else {
 128                                 None
 129                             }
 130                         })
 131                     });
 132
 133                 let snippet = self.snippet(mk_sp(
 134                     self.last_pos,
 135                     attr_lo.unwrap_or(first_stmt.span.lo()),
 136                 ));
 137                 let len = CommentCodeSlices::new(&snippet).nth(0).and_then(
 138                     |(kind, _, s)| if kind == CodeCharKind::Normal {
 139                         s.rfind('\n')
 140                     } else {
 141                         None
 142                     },
 143                 );
 144                 if let Some(len) = len {
 145                     self.last_pos = self.last_pos + BytePos::from_usize(len);
 146                 }
 147             }
 148         }
 149
 150         // Format inner attributes if available.
 151         if let Some(attrs) = inner_attrs {
 152             self.visit_attrs(attrs, ast::AttrStyle::Inner);
 153         }
 154
 155         self.walk_block_stmts(b);
 156
 157         if !b.stmts.is_empty() {
 158             if let Some(expr) = utils::stmt_expr(&b.stmts[b.stmts.len() - 1]) {
 159                 if utils::semicolon_for_expr(&self.get_context(), expr) {
 160                     self.buffer.push_str(";");
 161                 }
 162             }
 163         }
 164
 165         let mut remove_len = BytePos(0);
 166         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 167             if let Some(stmt) = b.stmts.last() {
 168                 let snippet = self.snippet(mk_sp(
 169                     stmt.span.hi(),
 170                     source!(self, b.span).hi() - brace_compensation,
 171                 ));
 172                 let len = CommentCodeSlices::new(&snippet)
 173                     .last()
 174                     .and_then(|(kind, _, s)| {
 175                         if kind == CodeCharKind::Normal && s.trim().is_empty() {
 176                             Some(s.len())
 177                         } else {
 178                             None
 179                         }
 180                     });
 181                 if let Some(len) = len {
 182                     remove_len = BytePos::from_usize(len);
 183                 }
 184             }
 185         }
 186
 187         let mut unindent_comment = self.is_if_else_block && !b.stmts.is_empty();
 188         if unindent_comment {
 189             let end_pos = source!(self, b.span).hi() - brace_compensation - remove_len;
 190             let snippet = self.snippet(mk_sp(self.last_pos, end_pos));
 191             unindent_comment = snippet.contains("//") || snippet.contains("/*");
 192         }
 193         // FIXME: we should compress any newlines here to just one
 194         if unindent_comment {
 195             self.block_indent = self.block_indent.block_unindent(self.config);
 196         }
 197         self.format_missing_with_indent(
 198             source!(self, b.span).hi() - brace_compensation - remove_len,
 199         );
 200         if unindent_comment {
 201             self.block_indent = self.block_indent.block_indent(self.config);
 202         }
 203         self.close_block(unindent_comment);
 204         self.last_pos = source!(self, b.span).hi();
 205     }
 206
 207     // FIXME: this is a terrible hack to indent the comments between the last
 208     // item in the block and the closing brace to the block's level.
 209     // The closing brace itself, however, should be indented at a shallower
 210     // level.
 211     fn close_block(&mut self, unindent_comment: bool) {
 212         let total_len = self.buffer.len;
 213         let chars_too_many = if unindent_comment {
 214             0
 215         } else if self.config.hard_tabs() {
 216             1
 217         } else {
 218             self.config.tab_spaces()
 219         };
 220         self.buffer.truncate(total_len - chars_too_many);
 221         self.buffer.push_str("}");
 222         self.block_indent = self.block_indent.block_unindent(self.config);
 223     }
 224
 225     // Note that this only gets called for function definitions. Required methods
 226     // on traits do not get handled here.
 227     fn visit_fn(
 228         &mut self,
 229         fk: visit::FnKind,
 230         fd: &ast::FnDecl,
 231         s: Span,
 232         _: ast::NodeId,
 233         defaultness: ast::Defaultness,
 234         inner_attrs: Option<&[ast::Attribute]>,
 235     ) {
 236         let indent = self.block_indent;
 237         let block;
 238         let rewrite = match fk {
 239             visit::FnKind::ItemFn(ident, generics, unsafety, constness, abi, vis, b) => {
 240                 block = b;
 241                 self.rewrite_fn(
 242                     indent,
 243                     ident,
 244                     fd,
 245                     generics,
 246                     unsafety,
 247                     constness.node,
 248                     defaultness,
 249                     abi,
 250                     vis,
 251                     mk_sp(s.lo(), b.span.lo()),
 252                     b,
 253                 )
 254             }
 255             visit::FnKind::Method(ident, sig, vis, b) => {
 256                 block = b;
 257                 self.rewrite_fn(
 258                     indent,
 259                     ident,
 260                     fd,
 261                     &sig.generics,
 262                     sig.unsafety,
 263                     sig.constness.node,
 264                     defaultness,
 265                     sig.abi,
 266                     vis.unwrap_or(&ast::Visibility::Inherited),
 267                     mk_sp(s.lo(), b.span.lo()),
 268                     b,
 269                 )
 270             }
 271             visit::FnKind::Closure(_) => unreachable!(),
 272         };
 273
 274         if let Some(fn_str) = rewrite {
 275             self.format_missing_with_indent(source!(self, s).lo());
 276             self.buffer.push_str(&fn_str);
 277             if let Some(c) = fn_str.chars().last() {
 278                 if c == '}' {
 279                     self.last_pos = source!(self, block.span).hi();
 280                     return;
 281                 }
 282             }
 283         } else {
 284             self.format_missing(source!(self, block.span).lo());
 285         }
 286
 287         self.last_pos = source!(self, block.span).lo();
 288         self.visit_block(block, inner_attrs)
 289     }
 290
 291     pub fn visit_item(&mut self, item: &ast::Item) {
 292         skip_out_of_file_lines_range_visitor!(self, item.span);
 293
 294         // This is where we bail out if there is a skip attribute. This is only
 295         // complex in the module case. It is complex because the module could be
 296         // in a separate file and there might be attributes in both files, but
 297         // the AST lumps them all together.
 298         let filterd_attrs;
 299         let mut attrs = &item.attrs;
 300         match item.node {
 301             ast::ItemKind::Mod(ref m) => {
 302                 let outer_file = self.codemap.lookup_char_pos(item.span.lo()).file;
 303                 let inner_file = self.codemap.lookup_char_pos(m.inner.lo()).file;
 304                 if outer_file.name == inner_file.name {
 305                     // Module is inline, in this case we treat modules like any
 306                     // other item.
 307                     if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 308                         self.push_rewrite(item.span, None);
 309                         return;
 310                     }
 311                 } else if contains_skip(&item.attrs) {
 312                     // Module is not inline, but should be skipped.
 313                     return;
 314                 } else {
 315                     // Module is not inline and should not be skipped. We want
 316                     // to process only the attributes in the current file.
 317                     filterd_attrs = item.attrs
 318                         .iter()
 319                         .filter_map(|a| {
 320                             let attr_file = self.codemap.lookup_char_pos(a.span.lo()).file;
 321                             if attr_file.name == outer_file.name {
 322                                 Some(a.clone())
 323                             } else {
 324                                 None
 325                             }
 326                         })
 327                         .collect::<Vec<_>>();
 328                     // Assert because if we should skip it should be caught by
 329                     // the above case.
 330                     assert!(!self.visit_attrs(&filterd_attrs, ast::AttrStyle::Outer));
 331                     attrs = &filterd_attrs;
 332                 }
 333             }
 334             _ => if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 335                 self.push_rewrite(item.span, None);
 336                 return;
 337             },
 338         }
 339
 340         match item.node {
 341             ast::ItemKind::Use(ref vp) => self.format_import(item, vp),
 342             ast::ItemKind::Impl(..) => {
 343                 let snippet = self.snippet(item.span);
 344                 let where_span_end = snippet
 345                     .find_uncommented("{")
 346                     .map(|x| (BytePos(x as u32)) + source!(self, item.span).lo());
 347                 let rw = format_impl(&self.get_context(), item, self.block_indent, where_span_end);
 348                 self.push_rewrite(item.span, rw);
 349             }
 350             ast::ItemKind::Trait(..) => {
 351                 let rw = format_trait(&self.get_context(), item, self.block_indent);
 352                 self.push_rewrite(item.span, rw);
 353             }
 354             ast::ItemKind::ExternCrate(_) => {
 355                 let rw = rewrite_extern_crate(&self.get_context(), item);
 356                 self.push_rewrite(item.span, rw);
 357             }
 358             ast::ItemKind::Struct(ref def, ref generics) => {
 359                 let rewrite = format_struct(
 360                     &self.get_context(),
 361                     "struct ",
 362                     item.ident,
 363                     &item.vis,
 364                     def,
 365                     Some(generics),
 366                     item.span,
 367                     self.block_indent,
 368                     None,
 369                 ).map(|s| match *def {
 370                     ast::VariantData::Tuple(..) => s + ";",
 371                     _ => s,
 372                 });
 373                 self.push_rewrite(item.span, rewrite);
 374             }
 375             ast::ItemKind::Enum(ref def, ref generics) => {
 376                 self.format_missing_with_indent(source!(self, item.span).lo());
 377                 self.visit_enum(item.ident, &item.vis, def, generics, item.span);
 378                 self.last_pos = source!(self, item.span).hi();
 379             }
 380             ast::ItemKind::Mod(ref module) => {
 381                 self.format_missing_with_indent(source!(self, item.span).lo());
 382                 self.format_mod(module, &item.vis, item.span, item.ident, attrs);
 383             }
 384             ast::ItemKind::Mac(ref mac) => {
 385                 self.visit_mac(mac, Some(item.ident), MacroPosition::Item);
 386             }
 387             ast::ItemKind::ForeignMod(ref foreign_mod) => {
 388                 self.format_missing_with_indent(source!(self, item.span).lo());
 389                 self.format_foreign_mod(foreign_mod, item.span);
 390             }
 391             ast::ItemKind::Static(ref ty, mutability, ref expr) => {
 392                 let rewrite = rewrite_static(
 393                     "static",
 394                     &item.vis,
 395                     item.ident,
 396                     ty,
 397                     mutability,
 398                     Some(expr),
 399                     self.block_indent,
 400                     item.span,
 401                     &self.get_context(),
 402                 );
 403                 self.push_rewrite(item.span, rewrite);
 404             }
 405             ast::ItemKind::Const(ref ty, ref expr) => {
 406                 let rewrite = rewrite_static(
 407                     "const",
 408                     &item.vis,
 409                     item.ident,
 410                     ty,
 411                     ast::Mutability::Immutable,
 412                     Some(expr),
 413                     self.block_indent,
 414                     item.span,
 415                     &self.get_context(),
 416                 );
 417                 self.push_rewrite(item.span, rewrite);
 418             }
 419             ast::ItemKind::DefaultImpl(..) => {
 420                 // FIXME(#78): format impl definitions.
 421             }
 422             ast::ItemKind::Fn(ref decl, unsafety, constness, abi, ref generics, ref body) => {
 423                 self.visit_fn(
 424                     visit::FnKind::ItemFn(
 425                         item.ident,
 426                         generics,
 427                         unsafety,
 428                         constness,
 429                         abi,
 430                         &item.vis,
 431                         body,
 432                     ),
 433                     decl,
 434                     item.span,
 435                     item.id,
 436                     ast::Defaultness::Final,
 437                     Some(&item.attrs),
 438                 )
 439             }
 440             ast::ItemKind::Ty(ref ty, ref generics) => {
 441                 let rewrite = rewrite_type_alias(
 442                     &self.get_context(),
 443                     self.block_indent,
 444                     item.ident,
 445                     ty,
 446                     generics,
 447                     &item.vis,
 448                     item.span,
 449                 );
 450                 self.push_rewrite(item.span, rewrite);
 451             }
 452             ast::ItemKind::Union(ref def, ref generics) => {
 453                 let rewrite = format_struct_struct(
 454                     &self.get_context(),
 455                     "union ",
 456                     item.ident,
 457                     &item.vis,
 458                     def.fields(),
 459                     Some(generics),
 460                     item.span,
 461                     self.block_indent,
 462                     None,
 463                 );
 464                 self.push_rewrite(item.span, rewrite);
 465             }
 466             ast::ItemKind::GlobalAsm(..) => {
 467                 let snippet = Some(self.snippet(item.span));
 468                 self.push_rewrite(item.span, snippet);
 469             }
 470             ast::ItemKind::MacroDef(..) => {
 471                 // FIXME(#1539): macros 2.0
 472                 let mac_snippet = Some(self.snippet(item.span));
 473                 self.push_rewrite(item.span, mac_snippet);
 474             }
 475         }
 476     }
 477
 478     pub fn visit_trait_item(&mut self, ti: &ast::TraitItem) {
 479         skip_out_of_file_lines_range_visitor!(self, ti.span);
 480
 481         if self.visit_attrs(&ti.attrs, ast::AttrStyle::Outer) {
 482             self.push_rewrite(ti.span, None);
 483             return;
 484         }
 485
 486         match ti.node {
 487             ast::TraitItemKind::Const(ref ty, ref expr_opt) => {
 488                 let rewrite = rewrite_static(
 489                     "const",
 490                     &ast::Visibility::Inherited,
 491                     ti.ident,
 492                     ty,
 493                     ast::Mutability::Immutable,
 494                     expr_opt.as_ref(),
 495                     self.block_indent,
 496                     ti.span,
 497                     &self.get_context(),
 498                 );
 499                 self.push_rewrite(ti.span, rewrite);
 500             }
 501             ast::TraitItemKind::Method(ref sig, None) => {
 502                 let indent = self.block_indent;
 503                 let rewrite = self.rewrite_required_fn(indent, ti.ident, sig, ti.span);
 504                 self.push_rewrite(ti.span, rewrite);
 505             }
 506             ast::TraitItemKind::Method(ref sig, Some(ref body)) => {
 507                 self.visit_fn(
 508                     visit::FnKind::Method(ti.ident, sig, None, body),
 509                     &sig.decl,
 510                     ti.span,
 511                     ti.id,
 512                     ast::Defaultness::Final,
 513                     Some(&ti.attrs),
 514                 );
 515             }
 516             ast::TraitItemKind::Type(ref type_param_bounds, ref type_default) => {
 517                 let rewrite = rewrite_associated_type(
 518                     ti.ident,
 519                     type_default.as_ref(),
 520                     Some(type_param_bounds),
 521                     &self.get_context(),
 522                     self.block_indent,
 523                 );
 524                 self.push_rewrite(ti.span, rewrite);
 525             }
 526             ast::TraitItemKind::Macro(ref mac) => {
 527                 self.visit_mac(mac, Some(ti.ident), MacroPosition::Item);
 528             }
 529         }
 530     }
 531
 532     pub fn visit_impl_item(&mut self, ii: &ast::ImplItem) {
 533         skip_out_of_file_lines_range_visitor!(self, ii.span);
 534
 535         if self.visit_attrs(&ii.attrs, ast::AttrStyle::Outer) {
 536             self.push_rewrite(ii.span, None);
 537             return;
 538         }
 539
 540         match ii.node {
 541             ast::ImplItemKind::Method(ref sig, ref body) => {
 542                 self.visit_fn(
 543                     visit::FnKind::Method(ii.ident, sig, Some(&ii.vis), body),
 544                     &sig.decl,
 545                     ii.span,
 546                     ii.id,
 547                     ii.defaultness,
 548                     Some(&ii.attrs),
 549                 );
 550             }
 551             ast::ImplItemKind::Const(ref ty, ref expr) => {
 552                 let rewrite = rewrite_static(
 553                     "const",
 554                     &ii.vis,
 555                     ii.ident,
 556                     ty,
 557                     ast::Mutability::Immutable,
 558                     Some(expr),
 559                     self.block_indent,
 560                     ii.span,
 561                     &self.get_context(),
 562                 );
 563                 self.push_rewrite(ii.span, rewrite);
 564             }
 565             ast::ImplItemKind::Type(ref ty) => {
 566                 let rewrite = rewrite_associated_impl_type(
 567                     ii.ident,
 568                     ii.defaultness,
 569                     Some(ty),
 570                     None,
 571                     &self.get_context(),
 572                     self.block_indent,
 573                 );
 574                 self.push_rewrite(ii.span, rewrite);
 575             }
 576             ast::ImplItemKind::Macro(ref mac) => {
 577                 self.visit_mac(mac, Some(ii.ident), MacroPosition::Item);
 578             }
 579         }
 580     }
 581
 582     fn visit_mac(&mut self, mac: &ast::Mac, ident: Option<ast::Ident>, pos: MacroPosition) {
 583         skip_out_of_file_lines_range_visitor!(self, mac.span);
 584
 585         // 1 = ;
 586         let shape = self.shape().sub_width(1).unwrap();
 587         let rewrite = rewrite_macro(mac, ident, &self.get_context(), shape, pos);
 588         self.push_rewrite(mac.span, rewrite);
 589     }
 590
 591     pub fn push_rewrite(&mut self, span: Span, rewrite: Option<String>) {
 592         self.format_missing_with_indent(source!(self, span).lo());
 593         let result = rewrite.unwrap_or_else(|| self.snippet(span));
 594         self.buffer.push_str(&result);
 595         self.last_pos = source!(self, span).hi();
 596     }
 597
 598     pub fn from_codemap(parse_session: &'a ParseSess, config: &'a Config) -> FmtVisitor<'a> {
 599         FmtVisitor {
 600             parse_session: parse_session,
 601             codemap: parse_session.codemap(),
 602             buffer: StringBuffer::new(),
 603             last_pos: BytePos(0),
 604             block_indent: Indent::empty(),
 605             config: config,
 606             is_if_else_block: false,
 607         }
 608     }
 609
 610     pub fn snippet(&self, span: Span) -> String {
 611         match self.codemap.span_to_snippet(span) {
 612             Ok(s) => s,
 613             Err(_) => {
 614                 println!(
 615                     "Couldn't make snippet for span {:?}->{:?}",
 616                     self.codemap.lookup_char_pos(span.lo()),
 617                     self.codemap.lookup_char_pos(span.hi())
 618                 );
 619                 "".to_owned()
 620             }
 621         }
 622     }
 623
 624     // Returns true if we should skip the following item.
 625     pub fn visit_attrs(&mut self, attrs: &[ast::Attribute], style: ast::AttrStyle) -> bool {
 626         if contains_skip(attrs) {
 627             return true;
 628         }
 629
 630         let attrs: Vec<_> = attrs.iter().filter(|a| a.style == style).cloned().collect();
 631         if attrs.is_empty() {
 632             return false;
 633         }
 634
 635         let rewrite = attrs.rewrite(&self.get_context(), self.shape());
 636         let span = mk_sp(attrs[0].span.lo(), attrs[attrs.len() - 1].span.hi());
 637         self.push_rewrite(span, rewrite);
 638
 639         false
 640     }
 641
 642     fn reorder_items<F>(&mut self, items_left: &[&ast::Item], is_item: &F, in_group: bool) -> usize
 643     where
 644         F: Fn(&ast::Item) -> bool,
 645     {
 646         let mut last = self.codemap.lookup_line_range(items_left[0].span());
 647         let item_length = items_left
 648             .iter()
 649             .take_while(|ppi| {
 650                 is_item(&***ppi) && (!in_group || {
 651                     let current = self.codemap.lookup_line_range(ppi.span());
 652                     let in_same_group = current.lo < last.hi + 2;
 653                     last = current;
 654                     in_same_group
 655                 })
 656             })
 657             .count();
 658         let items = &items_left[..item_length];
 659
 660         let at_least_one_in_file_lines = items
 661             .iter()
 662             .any(|item| !out_of_file_lines_range!(self, item.span));
 663
 664         if at_least_one_in_file_lines {
 665             self.format_imports(items);
 666         } else {
 667             for item in items {
 668                 self.push_rewrite(item.span, None);
 669             }
 670         }
 671
 672         item_length
 673     }
 674
 675     fn walk_items(&mut self, mut items_left: &[&ast::Item]) {
 676         while !items_left.is_empty() {
 677             // If the next item is a `use` declaration, then extract it and any subsequent `use`s
 678             // to be potentially reordered within `format_imports`. Otherwise, just format the
 679             // next item for output.
 680             if self.config.reorder_imports() && is_use_item(&*items_left[0]) {
 681                 let used_items_len = self.reorder_items(
 682                     items_left,
 683                     &is_use_item,
 684                     self.config.reorder_imports_in_group(),
 685                 );
 686                 let (_, rest) = items_left.split_at(used_items_len);
 687                 items_left = rest;
 688             } else if self.config.reorder_extern_crates() && is_extern_crate(&*items_left[0]) {
 689                 let used_items_len = self.reorder_items(
 690                     items_left,
 691                     &is_extern_crate,
 692                     self.config.reorder_extern_crates_in_group(),
 693                 );
 694                 let (_, rest) = items_left.split_at(used_items_len);
 695                 items_left = rest;
 696             } else {
 697                 // `unwrap()` is safe here because we know `items_left`
 698                 // has elements from the loop condition
 699                 let (item, rest) = items_left.split_first().unwrap();
 700                 self.visit_item(item);
 701                 items_left = rest;
 702             }
 703         }
 704     }
 705
 706     fn walk_mod_items(&mut self, m: &ast::Mod) {
 707         self.walk_items(&ptr_vec_to_ref_vec(&m.items));
 708     }
 709
 710     fn walk_stmts(&mut self, stmts: &[ast::Stmt]) {
 711         fn to_stmt_item(stmt: &ast::Stmt) -> Option<&ast::Item> {
 712             match stmt.node {
 713                 ast::StmtKind::Item(ref item) => Some(&**item),
 714                 _ => None,
 715             }
 716         }
 717
 718         if stmts.is_empty() {
 719             return;
 720         }
 721
 722         // Extract leading `use ...;`.
 723         let items: Vec<_> = stmts
 724             .iter()
 725             .take_while(|stmt| to_stmt_item(stmt).is_some())
 726             .filter_map(|stmt| to_stmt_item(stmt))
 727             .take_while(|item| is_use_item(item))
 728             .collect();
 729
 730         if items.is_empty() {
 731             self.visit_stmt(&stmts[0]);
 732             self.walk_stmts(&stmts[1..]);
 733         } else {
 734             self.walk_items(&items);
 735             self.walk_stmts(&stmts[items.len()..]);
 736         }
 737     }
 738
 739     fn walk_block_stmts(&mut self, b: &ast::Block) {
 740         self.walk_stmts(&b.stmts)
 741     }
 742
 743     fn format_mod(
 744         &mut self,
 745         m: &ast::Mod,
 746         vis: &ast::Visibility,
 747         s: Span,
 748         ident: ast::Ident,
 749         attrs: &[ast::Attribute],
 750     ) {
 751         // Decide whether this is an inline mod or an external mod.
 752         let local_file_name = self.codemap.span_to_filename(s);
 753         let inner_span = source!(self, m.inner);
 754         let is_internal = !(inner_span.lo().0 == 0 && inner_span.hi().0 == 0)
 755             && local_file_name == self.codemap.span_to_filename(inner_span);
 756
 757         self.buffer.push_str(&*utils::format_visibility(vis));
 758         self.buffer.push_str("mod ");
 759         self.buffer.push_str(&ident.to_string());
 760
 761         if is_internal {
 762             match self.config.item_brace_style() {
 763                 BraceStyle::AlwaysNextLine => self.buffer
 764                     .push_str(&format!("\n{}{{", self.block_indent.to_string(self.config))),
 765                 _ => self.buffer.push_str(" {"),
 766             }
 767             // Hackery to account for the closing }.
 768             let mod_lo = self.codemap.span_after(source!(self, s), "{");
 769             let body_snippet =
 770                 self.snippet(mk_sp(mod_lo, source!(self, m.inner).hi() - BytePos(1)));
 771             let body_snippet = body_snippet.trim();
 772             if body_snippet.is_empty() {
 773                 self.buffer.push_str("}");
 774             } else {
 775                 self.last_pos = mod_lo;
 776                 self.block_indent = self.block_indent.block_indent(self.config);
 777                 self.visit_attrs(attrs, ast::AttrStyle::Inner);
 778                 self.walk_mod_items(m);
 779                 self.format_missing_with_indent(source!(self, m.inner).hi() - BytePos(1));
 780                 self.close_block(false);
 781             }
 782             self.last_pos = source!(self, m.inner).hi();
 783         } else {
 784             self.buffer.push_str(";");
 785             self.last_pos = source!(self, s).hi();
 786         }
 787     }
 788
 789     pub fn format_separate_mod(&mut self, m: &ast::Mod, filemap: &codemap::FileMap) {
 790         self.block_indent = Indent::empty();
 791         self.walk_mod_items(m);
 792         self.format_missing_with_indent(filemap.end_pos);
 793     }
 794
 795     pub fn get_context(&self) -> RewriteContext {
 796         RewriteContext {
 797             parse_session: self.parse_session,
 798             codemap: self.codemap,
 799             config: self.config,
 800             inside_macro: false,
 801             use_block: false,
 802             is_if_else_block: false,
 803             force_one_line_chain: false,
 804         }
 805     }
 806 }
 807
 808 impl Rewrite for ast::NestedMetaItem {
 809     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 810         match self.node {
 811             ast::NestedMetaItemKind::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
 812             ast::NestedMetaItemKind::Literal(..) => Some(context.snippet(self.span)),
 813         }
 814     }
 815 }
 816
 817 impl Rewrite for ast::MetaItem {
 818     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 819         Some(match self.node {
 820             ast::MetaItemKind::Word => String::from(&*self.name.as_str()),
 821             ast::MetaItemKind::List(ref list) => {
 822                 let name = self.name.as_str();
 823                 // 3 = `#[` and `(`, 2 = `]` and `)`
 824                 let item_shape = try_opt!(
 825                     shape
 826                         .shrink_left(name.len() + 3)
 827                         .and_then(|s| s.sub_width(2))
 828                 );
 829                 let items = itemize_list(
 830                     context.codemap,
 831                     list.iter(),
 832                     ")",
 833                     |nested_meta_item| nested_meta_item.span.lo(),
 834                     |nested_meta_item| nested_meta_item.span.hi(),
 835                     |nested_meta_item| nested_meta_item.rewrite(context, item_shape),
 836                     self.span.lo(),
 837                     self.span.hi(),
 838                     false,
 839                 );
 840                 let item_vec = items.collect::<Vec<_>>();
 841                 let fmt = ListFormatting {
 842                     tactic: DefinitiveListTactic::Mixed,
 843                     separator: ",",
 844                     trailing_separator: SeparatorTactic::Never,
 845                     separator_place: SeparatorPlace::Back,
 846                     shape: item_shape,
 847                     ends_with_newline: false,
 848                     preserve_newline: false,
 849                     config: context.config,
 850                 };
 851                 format!("{}({})", name, try_opt!(write_list(&item_vec, &fmt)))
 852             }
 853             ast::MetaItemKind::NameValue(ref literal) => {
 854                 let name = self.name.as_str();
 855                 let value = context.snippet(literal.span);
 856                 if &*name == "doc" && contains_comment(&value) {
 857                     let doc_shape = Shape {
 858                         width: cmp::min(shape.width, context.config.comment_width())
 859                             .checked_sub(shape.indent.width())
 860                             .unwrap_or(0),
 861                         ..shape
 862                     };
 863                     try_opt!(rewrite_comment(&value, false, doc_shape, context.config))
 864                 } else {
 865                     format!("{} = {}", name, value)
 866                 }
 867             }
 868         })
 869     }
 870 }
 871
 872 impl Rewrite for ast::Attribute {
 873     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 874         try_opt!(self.meta())
 875             .rewrite(context, shape)
 876             .map(|rw| if self.is_sugared_doc {
 877                 rw
 878             } else {
 879                 let original = context.snippet(self.span);
 880                 let prefix = match self.style {
 881                     ast::AttrStyle::Inner => "#!",
 882                     ast::AttrStyle::Outer => "#",
 883                 };
 884                 if contains_comment(&original) {
 885                     original
 886                 } else {
 887                     format!("{}[{}]", prefix, rw)
 888                 }
 889             })
 890     }
 891 }
 892
 893 impl<'a> Rewrite for [ast::Attribute] {
 894     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 895         if self.is_empty() {
 896             return Some(String::new());
 897         }
 898         let mut result = String::with_capacity(128);
 899         let indent = shape.indent.to_string(context.config);
 900
 901         let mut derive_args = Vec::new();
 902
 903         let mut iter = self.iter().enumerate().peekable();
 904         let mut insert_new_line = true;
 905         let mut is_prev_sugared_doc = false;
 906         while let Some((i, a)) = iter.next() {
 907             let a_str = try_opt!(a.rewrite(context, shape));
 908
 909             // Write comments and blank lines between attributes.
 910             if i > 0 {
 911                 let comment = context.snippet(mk_sp(self[i - 1].span.hi(), a.span.lo()));
 912                 // This particular horror show is to preserve line breaks in between doc
 913                 // comments. An alternative would be to force such line breaks to start
 914                 // with the usual doc comment token.
 915                 let (multi_line_before, multi_line_after) = if a.is_sugared_doc
 916                     || is_prev_sugared_doc
 917                 {
 918                     // Look at before and after comment and see if there are any empty lines.
 919                     let comment_begin = comment.chars().position(|c| c == '/');
 920                     let len = comment_begin.unwrap_or_else(|| comment.len());
 921                     let mlb = comment.chars().take(len).filter(|c| *c == '\n').count() > 1;
 922                     let mla = if comment_begin.is_none() {
 923                         mlb
 924                     } else {
 925                         let comment_end = comment.chars().rev().position(|c| !c.is_whitespace());
 926                         let len = comment_end.unwrap();
 927                         comment
 928                             .chars()
 929                             .rev()
 930                             .take(len)
 931                             .filter(|c| *c == '\n')
 932                             .count() > 1
 933                     };
 934                     (mlb, mla)
 935                 } else {
 936                     (false, false)
 937                 };
 938
 939                 let comment = try_opt!(recover_missing_comment_in_span(
 940                     mk_sp(self[i - 1].span.hi(), a.span.lo()),
 941                     shape.with_max_width(context.config),
 942                     context,
 943                     0,
 944                 ));
 945
 946                 if !comment.is_empty() {
 947                     if multi_line_before {
 948                         result.push('\n');
 949                     }
 950                     result.push_str(&comment);
 951                     result.push('\n');
 952                     if multi_line_after {
 953                         result.push('\n')
 954                     }
 955                 } else if insert_new_line {
 956                     result.push('\n');
 957                     if multi_line_after {
 958                         result.push('\n')
 959                     }
 960                 }
 961
 962                 if derive_args.is_empty() {
 963                     result.push_str(&indent);
 964                 }
 965
 966                 insert_new_line = true;
 967             }
 968
 969             // Write the attribute itself.
 970             if context.config.merge_derives() {
 971                 // If the attribute is `#[derive(...)]`, take the arguments.
 972                 if let Some(mut args) = get_derive_args(context, a) {
 973                     derive_args.append(&mut args);
 974                     match iter.peek() {
 975                         // If the next attribute is `#[derive(...)]` as well, skip rewriting.
 976                         Some(&(_, next_attr)) if is_derive(next_attr) => insert_new_line = false,
 977                         // If not, rewrite the merged derives.
 978                         _ => {
 979                             result.push_str(&try_opt!(format_derive(context, &derive_args, shape)));
 980                             derive_args.clear();
 981                         }
 982                     }
 983                 } else {
 984                     result.push_str(&a_str);
 985                 }
 986             } else {
 987                 result.push_str(&a_str);
 988             }
 989
 990             is_prev_sugared_doc = a.is_sugared_doc;
 991         }
 992         Some(result)
 993     }
 994 }
 995
 996 // Format `#[derive(..)]`, using visual indent & mixed style when we need to go multiline.
 997 fn format_derive(context: &RewriteContext, derive_args: &[String], shape: Shape) -> Option<String> {
 998     let mut result = String::with_capacity(128);
 999     result.push_str("#[derive(");
1000     // 11 = `#[derive()]`
1001     let initial_budget = try_opt!(shape.width.checked_sub(11));
1002     let mut budget = initial_budget;
1003     let num = derive_args.len();
1004     for (i, a) in derive_args.iter().enumerate() {
1005         // 2 = `, ` or `)]`
1006         let width = a.len() + 2;
1007         if width > budget {
1008             if i > 0 {
1009                 // Remove trailing whitespace.
1010                 result.pop();
1011             }
1012             result.push('\n');
1013             // 9 = `#[derive(`
1014             result.push_str(&(shape.indent + 9).to_string(context.config));
1015             budget = initial_budget;
1016         } else {
1017             budget = budget.checked_sub(width).unwrap_or(0);
1018         }
1019         result.push_str(a);
1020         if i != num - 1 {
1021             result.push_str(", ")
1022         }
1023     }
1024     result.push_str(")]");
1025     Some(result)
1026 }
1027
1028 fn is_derive(attr: &ast::Attribute) -> bool {
1029     match attr.meta() {
1030         Some(meta_item) => match meta_item.node {
1031             ast::MetaItemKind::List(..) => meta_item.name.as_str() == "derive",
1032             _ => false,
1033         },
1034         _ => false,
1035     }
1036 }
1037
1038 /// Returns the arguments of `#[derive(...)]`.
1039 fn get_derive_args(context: &RewriteContext, attr: &ast::Attribute) -> Option<Vec<String>> {
1040     attr.meta().and_then(|meta_item| match meta_item.node {
1041         ast::MetaItemKind::List(ref args) if meta_item.name.as_str() == "derive" => {
1042             // Every argument of `derive` should be `NestedMetaItemKind::Literal`.
1043             Some(
1044                 args.iter()
1045                     .map(|a| context.snippet(a.span))
1046                     .collect::<Vec<_>>(),
1047             )
1048         }
1049         _ => None,
1050     })
1051 }
1052
1053 // Rewrite `extern crate foo;` WITHOUT attributes.
1054 pub fn rewrite_extern_crate(context: &RewriteContext, item: &ast::Item) -> Option<String> {
1055     assert!(is_extern_crate(item));
1056     let new_str = context.snippet(item.span);
1057     Some(if contains_comment(&new_str) {
1058         new_str
1059     } else {
1060         let no_whitespace = &new_str.split_whitespace().collect::<Vec<&str>>().join(" ");
1061         String::from(&*Regex::new(r"\s;").unwrap().replace(no_whitespace, ";"))
1062     })
1063 }