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 spanned::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, FnSig};
  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 shape::{Indent, Shape};
  34 use utils::{self, contains_skip, inner_attributes, mk_sp, ptr_vec_to_ref_vec};
  35
  36 fn is_use_item(item: &ast::Item) -> bool {
  37     match item.node {
  38         ast::ItemKind::Use(_) => true,
  39         _ => false,
  40     }
  41 }
  42
  43 fn is_extern_crate(item: &ast::Item) -> bool {
  44     match item.node {
  45         ast::ItemKind::ExternCrate(..) => true,
  46         _ => false,
  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 is_if_else_block: bool,
  59 }
  60
  61 impl<'a> FmtVisitor<'a> {
  62     pub fn shape(&self) -> Shape {
  63         Shape::indented(self.block_indent, self.config)
  64     }
  65
  66     fn visit_stmt(&mut self, stmt: &ast::Stmt) {
  67         debug!(
  68             "visit_stmt: {:?} {:?}",
  69             self.codemap.lookup_char_pos(stmt.span.lo()),
  70             self.codemap.lookup_char_pos(stmt.span.hi())
  71         );
  72
  73         match stmt.node {
  74             ast::StmtKind::Item(ref item) => {
  75                 self.visit_item(item);
  76             }
  77             ast::StmtKind::Local(..) | ast::StmtKind::Expr(..) | ast::StmtKind::Semi(..) => {
  78                 let rewrite = stmt.rewrite(&self.get_context(), self.shape());
  79                 self.push_rewrite(stmt.span(), rewrite)
  80             }
  81             ast::StmtKind::Mac(ref mac) => {
  82                 let (ref mac, _macro_style, ref attrs) = **mac;
  83                 if self.visit_attrs(attrs, ast::AttrStyle::Outer) {
  84                     self.push_rewrite(stmt.span(), None);
  85                 } else {
  86                     self.visit_mac(mac, None, MacroPosition::Statement);
  87                 }
  88                 self.format_missing(stmt.span.hi());
  89             }
  90         }
  91     }
  92
  93     pub fn visit_block(&mut self, b: &ast::Block, inner_attrs: Option<&[ast::Attribute]>) {
  94         debug!(
  95             "visit_block: {:?} {:?}",
  96             self.codemap.lookup_char_pos(b.span.lo()),
  97             self.codemap.lookup_char_pos(b.span.hi())
  98         );
  99
 100         // Check if this block has braces.
 101         let snippet = self.snippet(b.span);
 102         let has_braces = snippet.starts_with('{') || snippet.starts_with("unsafe");
 103         let brace_compensation = if has_braces { BytePos(1) } else { BytePos(0) };
 104
 105         self.last_pos = self.last_pos + brace_compensation;
 106         self.block_indent = self.block_indent.block_indent(self.config);
 107         self.buffer.push_str("{");
 108
 109         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 110             if let Some(first_stmt) = b.stmts.first() {
 111                 let attr_lo = inner_attrs
 112                     .and_then(|attrs| {
 113                         inner_attributes(attrs).first().map(|attr| attr.span.lo())
 114                     })
 115                     .or_else(|| {
 116                         // Attributes for an item in a statement position
 117                         // do not belong to the statement. (rust-lang/rust#34459)
 118                         if let ast::StmtKind::Item(ref item) = first_stmt.node {
 119                             item.attrs.first()
 120                         } else {
 121                             first_stmt.attrs().first()
 122                         }.and_then(|attr| {
 123                             // Some stmts can have embedded attributes.
 124                             // e.g. `match { #![attr] ... }`
 125                             let attr_lo = attr.span.lo();
 126                             if attr_lo < first_stmt.span.lo() {
 127                                 Some(attr_lo)
 128                             } else {
 129                                 None
 130                             }
 131                         })
 132                     });
 133
 134                 let snippet = self.snippet(mk_sp(
 135                     self.last_pos,
 136                     attr_lo.unwrap_or(first_stmt.span.lo()),
 137                 ));
 138                 let len = CommentCodeSlices::new(&snippet).nth(0).and_then(
 139                     |(kind, _, s)| if kind == CodeCharKind::Normal {
 140                         s.rfind('\n')
 141                     } else {
 142                         None
 143                     },
 144                 );
 145                 if let Some(len) = len {
 146                     self.last_pos = self.last_pos + BytePos::from_usize(len);
 147                 }
 148             }
 149         }
 150
 151         // Format inner attributes if available.
 152         if let Some(attrs) = inner_attrs {
 153             self.visit_attrs(attrs, ast::AttrStyle::Inner);
 154         }
 155
 156         self.walk_block_stmts(b);
 157
 158         if !b.stmts.is_empty() {
 159             if let Some(expr) = utils::stmt_expr(&b.stmts[b.stmts.len() - 1]) {
 160                 if utils::semicolon_for_expr(&self.get_context(), expr) {
 161                     self.buffer.push_str(";");
 162                 }
 163             }
 164         }
 165
 166         let mut remove_len = BytePos(0);
 167         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 168             if let Some(stmt) = b.stmts.last() {
 169                 let snippet = self.snippet(mk_sp(
 170                     stmt.span.hi(),
 171                     source!(self, b.span).hi() - brace_compensation,
 172                 ));
 173                 let len = CommentCodeSlices::new(&snippet)
 174                     .last()
 175                     .and_then(|(kind, _, s)| {
 176                         if kind == CodeCharKind::Normal && s.trim().is_empty() {
 177                             Some(s.len())
 178                         } else {
 179                             None
 180                         }
 181                     });
 182                 if let Some(len) = len {
 183                     remove_len = BytePos::from_usize(len);
 184                 }
 185             }
 186         }
 187
 188         let mut unindent_comment = self.is_if_else_block && !b.stmts.is_empty();
 189         if unindent_comment {
 190             let end_pos = source!(self, b.span).hi() - brace_compensation - remove_len;
 191             let snippet = self.snippet(mk_sp(self.last_pos, end_pos));
 192             unindent_comment = snippet.contains("//") || snippet.contains("/*");
 193         }
 194         // FIXME: we should compress any newlines here to just one
 195         if unindent_comment {
 196             self.block_indent = self.block_indent.block_unindent(self.config);
 197         }
 198         self.format_missing_with_indent(
 199             source!(self, b.span).hi() - brace_compensation - remove_len,
 200         );
 201         if unindent_comment {
 202             self.block_indent = self.block_indent.block_indent(self.config);
 203         }
 204         self.close_block(unindent_comment);
 205         self.last_pos = source!(self, b.span).hi();
 206     }
 207
 208     // FIXME: this is a terrible hack to indent the comments between the last
 209     // item in the block and the closing brace to the block's level.
 210     // The closing brace itself, however, should be indented at a shallower
 211     // level.
 212     fn close_block(&mut self, unindent_comment: bool) {
 213         let total_len = self.buffer.len;
 214         let chars_too_many = if unindent_comment {
 215             0
 216         } else if self.config.hard_tabs() {
 217             1
 218         } else {
 219             self.config.tab_spaces()
 220         };
 221         self.buffer.truncate(total_len - chars_too_many);
 222         self.buffer.push_str("}");
 223         self.block_indent = self.block_indent.block_unindent(self.config);
 224     }
 225
 226     // Note that this only gets called for function definitions. Required methods
 227     // on traits do not get handled here.
 228     fn visit_fn(
 229         &mut self,
 230         fk: visit::FnKind,
 231         fd: &ast::FnDecl,
 232         s: Span,
 233         _: ast::NodeId,
 234         defaultness: ast::Defaultness,
 235         inner_attrs: Option<&[ast::Attribute]>,
 236     ) {
 237         let indent = self.block_indent;
 238         let block;
 239         let rewrite = match fk {
 240             visit::FnKind::ItemFn(ident, _, _, _, _, _, b) => {
 241                 block = b;
 242                 self.rewrite_fn(
 243                     indent,
 244                     ident,
 245                     &FnSig::from_fn_kind(&fk, fd, defaultness),
 246                     mk_sp(s.lo(), b.span.lo()),
 247                     b,
 248                 )
 249             }
 250             visit::FnKind::Method(ident, _, _, b) => {
 251                 block = b;
 252                 self.rewrite_fn(
 253                     indent,
 254                     ident,
 255                     &FnSig::from_fn_kind(&fk, fd, defaultness),
 256                     mk_sp(s.lo(), b.span.lo()),
 257                     b,
 258                 )
 259             }
 260             visit::FnKind::Closure(_) => unreachable!(),
 261         };
 262
 263         if let Some(fn_str) = rewrite {
 264             self.format_missing_with_indent(source!(self, s).lo());
 265             self.buffer.push_str(&fn_str);
 266             if let Some(c) = fn_str.chars().last() {
 267                 if c == '}' {
 268                     self.last_pos = source!(self, block.span).hi();
 269                     return;
 270                 }
 271             }
 272         } else {
 273             self.format_missing(source!(self, block.span).lo());
 274         }
 275
 276         self.last_pos = source!(self, block.span).lo();
 277         self.visit_block(block, inner_attrs)
 278     }
 279
 280     pub fn visit_item(&mut self, item: &ast::Item) {
 281         skip_out_of_file_lines_range_visitor!(self, item.span);
 282
 283         // This is where we bail out if there is a skip attribute. This is only
 284         // complex in the module case. It is complex because the module could be
 285         // in a separate file and there might be attributes in both files, but
 286         // the AST lumps them all together.
 287         let filterd_attrs;
 288         let mut attrs = &item.attrs;
 289         match item.node {
 290             ast::ItemKind::Mod(ref m) => {
 291                 let outer_file = self.codemap.lookup_char_pos(item.span.lo()).file;
 292                 let inner_file = self.codemap.lookup_char_pos(m.inner.lo()).file;
 293                 if outer_file.name == inner_file.name {
 294                     // Module is inline, in this case we treat modules like any
 295                     // other item.
 296                     if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 297                         self.push_rewrite(item.span, None);
 298                         return;
 299                     }
 300                 } else if contains_skip(&item.attrs) {
 301                     // Module is not inline, but should be skipped.
 302                     return;
 303                 } else {
 304                     // Module is not inline and should not be skipped. We want
 305                     // to process only the attributes in the current file.
 306                     filterd_attrs = item.attrs
 307                         .iter()
 308                         .filter_map(|a| {
 309                             let attr_file = self.codemap.lookup_char_pos(a.span.lo()).file;
 310                             if attr_file.name == outer_file.name {
 311                                 Some(a.clone())
 312                             } else {
 313                                 None
 314                             }
 315                         })
 316                         .collect::<Vec<_>>();
 317                     // Assert because if we should skip it should be caught by
 318                     // the above case.
 319                     assert!(!self.visit_attrs(&filterd_attrs, ast::AttrStyle::Outer));
 320                     attrs = &filterd_attrs;
 321                 }
 322             }
 323             _ => if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 324                 self.push_rewrite(item.span, None);
 325                 return;
 326             },
 327         }
 328
 329         match item.node {
 330             ast::ItemKind::Use(ref vp) => self.format_import(item, vp),
 331             ast::ItemKind::Impl(..) => {
 332                 let snippet = self.snippet(item.span);
 333                 let where_span_end = snippet
 334                     .find_uncommented("{")
 335                     .map(|x| (BytePos(x as u32)) + source!(self, item.span).lo());
 336                 let rw = format_impl(&self.get_context(), item, self.block_indent, where_span_end);
 337                 self.push_rewrite(item.span, rw);
 338             }
 339             ast::ItemKind::Trait(..) => {
 340                 let rw = format_trait(&self.get_context(), item, self.block_indent);
 341                 self.push_rewrite(item.span, rw);
 342             }
 343             ast::ItemKind::ExternCrate(_) => {
 344                 let rw = rewrite_extern_crate(&self.get_context(), item);
 345                 self.push_rewrite(item.span, rw);
 346             }
 347             ast::ItemKind::Struct(ref def, ref generics) => {
 348                 let rewrite = format_struct(
 349                     &self.get_context(),
 350                     "struct ",
 351                     item.ident,
 352                     &item.vis,
 353                     def,
 354                     Some(generics),
 355                     item.span,
 356                     self.block_indent,
 357                     None,
 358                 ).map(|s| match *def {
 359                     ast::VariantData::Tuple(..) => s + ";",
 360                     _ => s,
 361                 });
 362                 self.push_rewrite(item.span, rewrite);
 363             }
 364             ast::ItemKind::Enum(ref def, ref generics) => {
 365                 self.format_missing_with_indent(source!(self, item.span).lo());
 366                 self.visit_enum(item.ident, &item.vis, def, generics, item.span);
 367                 self.last_pos = source!(self, item.span).hi();
 368             }
 369             ast::ItemKind::Mod(ref module) => {
 370                 self.format_missing_with_indent(source!(self, item.span).lo());
 371                 self.format_mod(module, &item.vis, item.span, item.ident, attrs);
 372             }
 373             ast::ItemKind::Mac(ref mac) => {
 374                 self.visit_mac(mac, Some(item.ident), MacroPosition::Item);
 375             }
 376             ast::ItemKind::ForeignMod(ref foreign_mod) => {
 377                 self.format_missing_with_indent(source!(self, item.span).lo());
 378                 self.format_foreign_mod(foreign_mod, item.span);
 379             }
 380             ast::ItemKind::Static(ref ty, mutability, ref expr) => {
 381                 let rewrite = rewrite_static(
 382                     "static",
 383                     &item.vis,
 384                     item.ident,
 385                     ty,
 386                     mutability,
 387                     Some(expr),
 388                     self.block_indent,
 389                     item.span,
 390                     &self.get_context(),
 391                 );
 392                 self.push_rewrite(item.span, rewrite);
 393             }
 394             ast::ItemKind::Const(ref ty, ref expr) => {
 395                 let rewrite = rewrite_static(
 396                     "const",
 397                     &item.vis,
 398                     item.ident,
 399                     ty,
 400                     ast::Mutability::Immutable,
 401                     Some(expr),
 402                     self.block_indent,
 403                     item.span,
 404                     &self.get_context(),
 405                 );
 406                 self.push_rewrite(item.span, rewrite);
 407             }
 408             ast::ItemKind::DefaultImpl(..) => {
 409                 // FIXME(#78): format impl definitions.
 410             }
 411             ast::ItemKind::Fn(ref decl, unsafety, constness, abi, ref generics, ref body) => {
 412                 self.visit_fn(
 413                     visit::FnKind::ItemFn(
 414                         item.ident,
 415                         generics,
 416                         unsafety,
 417                         constness,
 418                         abi,
 419                         &item.vis,
 420                         body,
 421                     ),
 422                     decl,
 423                     item.span,
 424                     item.id,
 425                     ast::Defaultness::Final,
 426                     Some(&item.attrs),
 427                 )
 428             }
 429             ast::ItemKind::Ty(ref ty, ref generics) => {
 430                 let rewrite = rewrite_type_alias(
 431                     &self.get_context(),
 432                     self.block_indent,
 433                     item.ident,
 434                     ty,
 435                     generics,
 436                     &item.vis,
 437                     item.span,
 438                 );
 439                 self.push_rewrite(item.span, rewrite);
 440             }
 441             ast::ItemKind::Union(ref def, ref generics) => {
 442                 let rewrite = format_struct_struct(
 443                     &self.get_context(),
 444                     "union ",
 445                     item.ident,
 446                     &item.vis,
 447                     def.fields(),
 448                     Some(generics),
 449                     item.span,
 450                     self.block_indent,
 451                     None,
 452                 );
 453                 self.push_rewrite(item.span, rewrite);
 454             }
 455             ast::ItemKind::GlobalAsm(..) => {
 456                 let snippet = Some(self.snippet(item.span));
 457                 self.push_rewrite(item.span, snippet);
 458             }
 459             ast::ItemKind::MacroDef(..) => {
 460                 // FIXME(#1539): macros 2.0
 461                 let mac_snippet = Some(self.snippet(item.span));
 462                 self.push_rewrite(item.span, mac_snippet);
 463             }
 464         }
 465     }
 466
 467     pub fn visit_trait_item(&mut self, ti: &ast::TraitItem) {
 468         skip_out_of_file_lines_range_visitor!(self, ti.span);
 469
 470         if self.visit_attrs(&ti.attrs, ast::AttrStyle::Outer) {
 471             self.push_rewrite(ti.span, None);
 472             return;
 473         }
 474
 475         match ti.node {
 476             ast::TraitItemKind::Const(ref ty, ref expr_opt) => {
 477                 let rewrite = rewrite_static(
 478                     "const",
 479                     &ast::Visibility::Inherited,
 480                     ti.ident,
 481                     ty,
 482                     ast::Mutability::Immutable,
 483                     expr_opt.as_ref(),
 484                     self.block_indent,
 485                     ti.span,
 486                     &self.get_context(),
 487                 );
 488                 self.push_rewrite(ti.span, rewrite);
 489             }
 490             ast::TraitItemKind::Method(ref sig, None) => {
 491                 let indent = self.block_indent;
 492                 let rewrite = self.rewrite_required_fn(indent, ti.ident, sig, ti.span);
 493                 self.push_rewrite(ti.span, rewrite);
 494             }
 495             ast::TraitItemKind::Method(ref sig, Some(ref body)) => {
 496                 self.visit_fn(
 497                     visit::FnKind::Method(ti.ident, sig, None, body),
 498                     &sig.decl,
 499                     ti.span,
 500                     ti.id,
 501                     ast::Defaultness::Final,
 502                     Some(&ti.attrs),
 503                 );
 504             }
 505             ast::TraitItemKind::Type(ref type_param_bounds, ref type_default) => {
 506                 let rewrite = rewrite_associated_type(
 507                     ti.ident,
 508                     type_default.as_ref(),
 509                     Some(type_param_bounds),
 510                     &self.get_context(),
 511                     self.block_indent,
 512                 );
 513                 self.push_rewrite(ti.span, rewrite);
 514             }
 515             ast::TraitItemKind::Macro(ref mac) => {
 516                 self.visit_mac(mac, Some(ti.ident), MacroPosition::Item);
 517             }
 518         }
 519     }
 520
 521     pub fn visit_impl_item(&mut self, ii: &ast::ImplItem) {
 522         skip_out_of_file_lines_range_visitor!(self, ii.span);
 523
 524         if self.visit_attrs(&ii.attrs, ast::AttrStyle::Outer) {
 525             self.push_rewrite(ii.span, None);
 526             return;
 527         }
 528
 529         match ii.node {
 530             ast::ImplItemKind::Method(ref sig, ref body) => {
 531                 self.visit_fn(
 532                     visit::FnKind::Method(ii.ident, sig, Some(&ii.vis), body),
 533                     &sig.decl,
 534                     ii.span,
 535                     ii.id,
 536                     ii.defaultness,
 537                     Some(&ii.attrs),
 538                 );
 539             }
 540             ast::ImplItemKind::Const(ref ty, ref expr) => {
 541                 let rewrite = rewrite_static(
 542                     "const",
 543                     &ii.vis,
 544                     ii.ident,
 545                     ty,
 546                     ast::Mutability::Immutable,
 547                     Some(expr),
 548                     self.block_indent,
 549                     ii.span,
 550                     &self.get_context(),
 551                 );
 552                 self.push_rewrite(ii.span, rewrite);
 553             }
 554             ast::ImplItemKind::Type(ref ty) => {
 555                 let rewrite = rewrite_associated_impl_type(
 556                     ii.ident,
 557                     ii.defaultness,
 558                     Some(ty),
 559                     None,
 560                     &self.get_context(),
 561                     self.block_indent,
 562                 );
 563                 self.push_rewrite(ii.span, rewrite);
 564             }
 565             ast::ImplItemKind::Macro(ref mac) => {
 566                 self.visit_mac(mac, Some(ii.ident), MacroPosition::Item);
 567             }
 568         }
 569     }
 570
 571     fn visit_mac(&mut self, mac: &ast::Mac, ident: Option<ast::Ident>, pos: MacroPosition) {
 572         skip_out_of_file_lines_range_visitor!(self, mac.span);
 573
 574         // 1 = ;
 575         let shape = self.shape().sub_width(1).unwrap();
 576         let rewrite = rewrite_macro(mac, ident, &self.get_context(), shape, pos);
 577         self.push_rewrite(mac.span, rewrite);
 578     }
 579
 580     pub fn push_rewrite(&mut self, span: Span, rewrite: Option<String>) {
 581         self.format_missing_with_indent(source!(self, span).lo());
 582         let result = rewrite.unwrap_or_else(|| self.snippet(span));
 583         self.buffer.push_str(&result);
 584         self.last_pos = source!(self, span).hi();
 585     }
 586
 587     pub fn from_codemap(parse_session: &'a ParseSess, config: &'a Config) -> FmtVisitor<'a> {
 588         FmtVisitor {
 589             parse_session: parse_session,
 590             codemap: parse_session.codemap(),
 591             buffer: StringBuffer::new(),
 592             last_pos: BytePos(0),
 593             block_indent: Indent::empty(),
 594             config: config,
 595             is_if_else_block: false,
 596         }
 597     }
 598
 599     pub fn snippet(&self, span: Span) -> String {
 600         match self.codemap.span_to_snippet(span) {
 601             Ok(s) => s,
 602             Err(_) => {
 603                 println!(
 604                     "Couldn't make snippet for span {:?}->{:?}",
 605                     self.codemap.lookup_char_pos(span.lo()),
 606                     self.codemap.lookup_char_pos(span.hi())
 607                 );
 608                 "".to_owned()
 609             }
 610         }
 611     }
 612
 613     // Returns true if we should skip the following item.
 614     pub fn visit_attrs(&mut self, attrs: &[ast::Attribute], style: ast::AttrStyle) -> bool {
 615         if contains_skip(attrs) {
 616             return true;
 617         }
 618
 619         let attrs: Vec<_> = attrs.iter().filter(|a| a.style == style).cloned().collect();
 620         if attrs.is_empty() {
 621             return false;
 622         }
 623
 624         let rewrite = attrs.rewrite(&self.get_context(), self.shape());
 625         let span = mk_sp(attrs[0].span.lo(), attrs[attrs.len() - 1].span.hi());
 626         self.push_rewrite(span, rewrite);
 627
 628         false
 629     }
 630
 631     fn reorder_items<F>(&mut self, items_left: &[&ast::Item], is_item: &F, in_group: bool) -> usize
 632     where
 633         F: Fn(&ast::Item) -> bool,
 634     {
 635         let mut last = self.codemap.lookup_line_range(items_left[0].span());
 636         let item_length = items_left
 637             .iter()
 638             .take_while(|ppi| {
 639                 is_item(&***ppi) && (!in_group || {
 640                     let current = self.codemap.lookup_line_range(ppi.span());
 641                     let in_same_group = current.lo < last.hi + 2;
 642                     last = current;
 643                     in_same_group
 644                 })
 645             })
 646             .count();
 647         let items = &items_left[..item_length];
 648
 649         let at_least_one_in_file_lines = items
 650             .iter()
 651             .any(|item| !out_of_file_lines_range!(self, item.span));
 652
 653         if at_least_one_in_file_lines {
 654             self.format_imports(items);
 655         } else {
 656             for item in items {
 657                 self.push_rewrite(item.span, None);
 658             }
 659         }
 660
 661         item_length
 662     }
 663
 664     fn walk_items(&mut self, mut items_left: &[&ast::Item]) {
 665         while !items_left.is_empty() {
 666             // If the next item is a `use` declaration, then extract it and any subsequent `use`s
 667             // to be potentially reordered within `format_imports`. Otherwise, just format the
 668             // next item for output.
 669             if self.config.reorder_imports() && is_use_item(&*items_left[0]) {
 670                 let used_items_len = self.reorder_items(
 671                     items_left,
 672                     &is_use_item,
 673                     self.config.reorder_imports_in_group(),
 674                 );
 675                 let (_, rest) = items_left.split_at(used_items_len);
 676                 items_left = rest;
 677             } else if self.config.reorder_extern_crates() && is_extern_crate(&*items_left[0]) {
 678                 let used_items_len = self.reorder_items(
 679                     items_left,
 680                     &is_extern_crate,
 681                     self.config.reorder_extern_crates_in_group(),
 682                 );
 683                 let (_, rest) = items_left.split_at(used_items_len);
 684                 items_left = rest;
 685             } else {
 686                 // `unwrap()` is safe here because we know `items_left`
 687                 // has elements from the loop condition
 688                 let (item, rest) = items_left.split_first().unwrap();
 689                 self.visit_item(item);
 690                 items_left = rest;
 691             }
 692         }
 693     }
 694
 695     fn walk_mod_items(&mut self, m: &ast::Mod) {
 696         self.walk_items(&ptr_vec_to_ref_vec(&m.items));
 697     }
 698
 699     fn walk_stmts(&mut self, stmts: &[ast::Stmt]) {
 700         fn to_stmt_item(stmt: &ast::Stmt) -> Option<&ast::Item> {
 701             match stmt.node {
 702                 ast::StmtKind::Item(ref item) => Some(&**item),
 703                 _ => None,
 704             }
 705         }
 706
 707         if stmts.is_empty() {
 708             return;
 709         }
 710
 711         // Extract leading `use ...;`.
 712         let items: Vec<_> = stmts
 713             .iter()
 714             .take_while(|stmt| to_stmt_item(stmt).is_some())
 715             .filter_map(|stmt| to_stmt_item(stmt))
 716             .take_while(|item| is_use_item(item))
 717             .collect();
 718
 719         if items.is_empty() {
 720             self.visit_stmt(&stmts[0]);
 721             self.walk_stmts(&stmts[1..]);
 722         } else {
 723             self.walk_items(&items);
 724             self.walk_stmts(&stmts[items.len()..]);
 725         }
 726     }
 727
 728     fn walk_block_stmts(&mut self, b: &ast::Block) {
 729         self.walk_stmts(&b.stmts)
 730     }
 731
 732     fn format_mod(
 733         &mut self,
 734         m: &ast::Mod,
 735         vis: &ast::Visibility,
 736         s: Span,
 737         ident: ast::Ident,
 738         attrs: &[ast::Attribute],
 739     ) {
 740         // Decide whether this is an inline mod or an external mod.
 741         let local_file_name = self.codemap.span_to_filename(s);
 742         let inner_span = source!(self, m.inner);
 743         let is_internal = !(inner_span.lo().0 == 0 && inner_span.hi().0 == 0)
 744             && local_file_name == self.codemap.span_to_filename(inner_span);
 745
 746         self.buffer.push_str(&*utils::format_visibility(vis));
 747         self.buffer.push_str("mod ");
 748         self.buffer.push_str(&ident.to_string());
 749
 750         if is_internal {
 751             match self.config.item_brace_style() {
 752                 BraceStyle::AlwaysNextLine => self.buffer
 753                     .push_str(&format!("\n{}{{", self.block_indent.to_string(self.config))),
 754                 _ => self.buffer.push_str(" {"),
 755             }
 756             // Hackery to account for the closing }.
 757             let mod_lo = self.codemap.span_after(source!(self, s), "{");
 758             let body_snippet =
 759                 self.snippet(mk_sp(mod_lo, source!(self, m.inner).hi() - BytePos(1)));
 760             let body_snippet = body_snippet.trim();
 761             if body_snippet.is_empty() {
 762                 self.buffer.push_str("}");
 763             } else {
 764                 self.last_pos = mod_lo;
 765                 self.block_indent = self.block_indent.block_indent(self.config);
 766                 self.visit_attrs(attrs, ast::AttrStyle::Inner);
 767                 self.walk_mod_items(m);
 768                 self.format_missing_with_indent(source!(self, m.inner).hi() - BytePos(1));
 769                 self.close_block(false);
 770             }
 771             self.last_pos = source!(self, m.inner).hi();
 772         } else {
 773             self.buffer.push_str(";");
 774             self.last_pos = source!(self, s).hi();
 775         }
 776     }
 777
 778     pub fn format_separate_mod(&mut self, m: &ast::Mod, filemap: &codemap::FileMap) {
 779         self.block_indent = Indent::empty();
 780         self.walk_mod_items(m);
 781         self.format_missing_with_indent(filemap.end_pos);
 782     }
 783
 784     pub fn get_context(&self) -> RewriteContext {
 785         RewriteContext {
 786             parse_session: self.parse_session,
 787             codemap: self.codemap,
 788             config: self.config,
 789             inside_macro: false,
 790             use_block: false,
 791             is_if_else_block: false,
 792             force_one_line_chain: false,
 793         }
 794     }
 795 }
 796
 797 impl Rewrite for ast::NestedMetaItem {
 798     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 799         match self.node {
 800             ast::NestedMetaItemKind::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
 801             ast::NestedMetaItemKind::Literal(..) => Some(context.snippet(self.span)),
 802         }
 803     }
 804 }
 805
 806 impl Rewrite for ast::MetaItem {
 807     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 808         Some(match self.node {
 809             ast::MetaItemKind::Word => String::from(&*self.name.as_str()),
 810             ast::MetaItemKind::List(ref list) => {
 811                 let name = self.name.as_str();
 812                 // 3 = `#[` and `(`, 2 = `]` and `)`
 813                 let item_shape = try_opt!(
 814                     shape
 815                         .shrink_left(name.len() + 3)
 816                         .and_then(|s| s.sub_width(2))
 817                 );
 818                 let items = itemize_list(
 819                     context.codemap,
 820                     list.iter(),
 821                     ")",
 822                     |nested_meta_item| nested_meta_item.span.lo(),
 823                     |nested_meta_item| nested_meta_item.span.hi(),
 824                     |nested_meta_item| nested_meta_item.rewrite(context, item_shape),
 825                     self.span.lo(),
 826                     self.span.hi(),
 827                     false,
 828                 );
 829                 let item_vec = items.collect::<Vec<_>>();
 830                 let fmt = ListFormatting {
 831                     tactic: DefinitiveListTactic::Mixed,
 832                     separator: ",",
 833                     trailing_separator: SeparatorTactic::Never,
 834                     separator_place: SeparatorPlace::Back,
 835                     shape: item_shape,
 836                     ends_with_newline: false,
 837                     preserve_newline: false,
 838                     config: context.config,
 839                 };
 840                 format!("{}({})", name, try_opt!(write_list(&item_vec, &fmt)))
 841             }
 842             ast::MetaItemKind::NameValue(ref literal) => {
 843                 let name = self.name.as_str();
 844                 let value = context.snippet(literal.span);
 845                 if &*name == "doc" && contains_comment(&value) {
 846                     let doc_shape = Shape {
 847                         width: cmp::min(shape.width, context.config.comment_width())
 848                             .checked_sub(shape.indent.width())
 849                             .unwrap_or(0),
 850                         ..shape
 851                     };
 852                     try_opt!(rewrite_comment(&value, false, doc_shape, context.config))
 853                 } else {
 854                     format!("{} = {}", name, value)
 855                 }
 856             }
 857         })
 858     }
 859 }
 860
 861 impl Rewrite for ast::Attribute {
 862     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 863         try_opt!(self.meta())
 864             .rewrite(context, shape)
 865             .map(|rw| if self.is_sugared_doc {
 866                 rw
 867             } else {
 868                 let original = context.snippet(self.span);
 869                 let prefix = match self.style {
 870                     ast::AttrStyle::Inner => "#!",
 871                     ast::AttrStyle::Outer => "#",
 872                 };
 873                 if contains_comment(&original) {
 874                     original
 875                 } else {
 876                     format!("{}[{}]", prefix, rw)
 877                 }
 878             })
 879     }
 880 }
 881
 882 impl<'a> Rewrite for [ast::Attribute] {
 883     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 884         if self.is_empty() {
 885             return Some(String::new());
 886         }
 887         let mut result = String::with_capacity(128);
 888         let indent = shape.indent.to_string(context.config);
 889
 890         let mut derive_args = Vec::new();
 891
 892         let mut iter = self.iter().enumerate().peekable();
 893         let mut insert_new_line = true;
 894         let mut is_prev_sugared_doc = false;
 895         while let Some((i, a)) = iter.next() {
 896             let a_str = try_opt!(a.rewrite(context, shape));
 897
 898             // Write comments and blank lines between attributes.
 899             if i > 0 {
 900                 let comment = context.snippet(mk_sp(self[i - 1].span.hi(), a.span.lo()));
 901                 // This particular horror show is to preserve line breaks in between doc
 902                 // comments. An alternative would be to force such line breaks to start
 903                 // with the usual doc comment token.
 904                 let (multi_line_before, multi_line_after) = if a.is_sugared_doc
 905                     || is_prev_sugared_doc
 906                 {
 907                     // Look at before and after comment and see if there are any empty lines.
 908                     let comment_begin = comment.chars().position(|c| c == '/');
 909                     let len = comment_begin.unwrap_or_else(|| comment.len());
 910                     let mlb = comment.chars().take(len).filter(|c| *c == '\n').count() > 1;
 911                     let mla = if comment_begin.is_none() {
 912                         mlb
 913                     } else {
 914                         let comment_end = comment.chars().rev().position(|c| !c.is_whitespace());
 915                         let len = comment_end.unwrap();
 916                         comment
 917                             .chars()
 918                             .rev()
 919                             .take(len)
 920                             .filter(|c| *c == '\n')
 921                             .count() > 1
 922                     };
 923                     (mlb, mla)
 924                 } else {
 925                     (false, false)
 926                 };
 927
 928                 let comment = try_opt!(recover_missing_comment_in_span(
 929                     mk_sp(self[i - 1].span.hi(), a.span.lo()),
 930                     shape.with_max_width(context.config),
 931                     context,
 932                     0,
 933                 ));
 934
 935                 if !comment.is_empty() {
 936                     if multi_line_before {
 937                         result.push('\n');
 938                     }
 939                     result.push_str(&comment);
 940                     result.push('\n');
 941                     if multi_line_after {
 942                         result.push('\n')
 943                     }
 944                 } else if insert_new_line {
 945                     result.push('\n');
 946                     if multi_line_after {
 947                         result.push('\n')
 948                     }
 949                 }
 950
 951                 if derive_args.is_empty() {
 952                     result.push_str(&indent);
 953                 }
 954
 955                 insert_new_line = true;
 956             }
 957
 958             // Write the attribute itself.
 959             if context.config.merge_derives() {
 960                 // If the attribute is `#[derive(...)]`, take the arguments.
 961                 if let Some(mut args) = get_derive_args(context, a) {
 962                     derive_args.append(&mut args);
 963                     match iter.peek() {
 964                         // If the next attribute is `#[derive(...)]` as well, skip rewriting.
 965                         Some(&(_, next_attr)) if is_derive(next_attr) => insert_new_line = false,
 966                         // If not, rewrite the merged derives.
 967                         _ => {
 968                             result.push_str(&try_opt!(format_derive(context, &derive_args, shape)));
 969                             derive_args.clear();
 970                         }
 971                     }
 972                 } else {
 973                     result.push_str(&a_str);
 974                 }
 975             } else {
 976                 result.push_str(&a_str);
 977             }
 978
 979             is_prev_sugared_doc = a.is_sugared_doc;
 980         }
 981         Some(result)
 982     }
 983 }
 984
 985 // Format `#[derive(..)]`, using visual indent & mixed style when we need to go multiline.
 986 fn format_derive(context: &RewriteContext, derive_args: &[String], shape: Shape) -> Option<String> {
 987     let mut result = String::with_capacity(128);
 988     result.push_str("#[derive(");
 989     // 11 = `#[derive()]`
 990     let initial_budget = try_opt!(shape.width.checked_sub(11));
 991     let mut budget = initial_budget;
 992     let num = derive_args.len();
 993     for (i, a) in derive_args.iter().enumerate() {
 994         // 2 = `, ` or `)]`
 995         let width = a.len() + 2;
 996         if width > budget {
 997             if i > 0 {
 998                 // Remove trailing whitespace.
 999                 result.pop();
1000             }
1001             result.push('\n');
1002             // 9 = `#[derive(`
1003             result.push_str(&(shape.indent + 9).to_string(context.config));
1004             budget = initial_budget;
1005         } else {
1006             budget = budget.checked_sub(width).unwrap_or(0);
1007         }
1008         result.push_str(a);
1009         if i != num - 1 {
1010             result.push_str(", ")
1011         }
1012     }
1013     result.push_str(")]");
1014     Some(result)
1015 }
1016
1017 fn is_derive(attr: &ast::Attribute) -> bool {
1018     match attr.meta() {
1019         Some(meta_item) => match meta_item.node {
1020             ast::MetaItemKind::List(..) => meta_item.name.as_str() == "derive",
1021             _ => false,
1022         },
1023         _ => false,
1024     }
1025 }
1026
1027 /// Returns the arguments of `#[derive(...)]`.
1028 fn get_derive_args(context: &RewriteContext, attr: &ast::Attribute) -> Option<Vec<String>> {
1029     attr.meta().and_then(|meta_item| match meta_item.node {
1030         ast::MetaItemKind::List(ref args) if meta_item.name.as_str() == "derive" => {
1031             // Every argument of `derive` should be `NestedMetaItemKind::Literal`.
1032             Some(
1033                 args.iter()
1034                     .map(|a| context.snippet(a.span))
1035                     .collect::<Vec<_>>(),
1036             )
1037         }
1038         _ => None,
1039     })
1040 }
1041
1042 // Rewrite `extern crate foo;` WITHOUT attributes.
1043 pub fn rewrite_extern_crate(context: &RewriteContext, item: &ast::Item) -> Option<String> {
1044     assert!(is_extern_crate(item));
1045     let new_str = context.snippet(item.span);
1046     Some(if contains_comment(&new_str) {
1047         new_str
1048     } else {
1049         let no_whitespace = &new_str.split_whitespace().collect::<Vec<&str>>().join(" ");
1050         String::from(&*Regex::new(r"\s;").unwrap().replace(no_whitespace, ";"))
1051     })
1052 }