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};
  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, generics, unsafety, constness, abi, vis, b) => {
 241                 block = b;
 242                 self.rewrite_fn(
 243                     indent,
 244                     ident,
 245                     fd,
 246                     generics,
 247                     unsafety,
 248                     constness.node,
 249                     defaultness,
 250                     abi,
 251                     vis,
 252                     mk_sp(s.lo(), b.span.lo()),
 253                     b,
 254                 )
 255             }
 256             visit::FnKind::Method(ident, sig, vis, b) => {
 257                 block = b;
 258                 self.rewrite_fn(
 259                     indent,
 260                     ident,
 261                     fd,
 262                     &sig.generics,
 263                     sig.unsafety,
 264                     sig.constness.node,
 265                     defaultness,
 266                     sig.abi,
 267                     vis.unwrap_or(&ast::Visibility::Inherited),
 268                     mk_sp(s.lo(), b.span.lo()),
 269                     b,
 270                 )
 271             }
 272             visit::FnKind::Closure(_) => unreachable!(),
 273         };
 274
 275         if let Some(fn_str) = rewrite {
 276             self.format_missing_with_indent(source!(self, s).lo());
 277             self.buffer.push_str(&fn_str);
 278             if let Some(c) = fn_str.chars().last() {
 279                 if c == '}' {
 280                     self.last_pos = source!(self, block.span).hi();
 281                     return;
 282                 }
 283             }
 284         } else {
 285             self.format_missing(source!(self, block.span).lo());
 286         }
 287
 288         self.last_pos = source!(self, block.span).lo();
 289         self.visit_block(block, inner_attrs)
 290     }
 291
 292     pub fn visit_item(&mut self, item: &ast::Item) {
 293         skip_out_of_file_lines_range_visitor!(self, item.span);
 294
 295         // This is where we bail out if there is a skip attribute. This is only
 296         // complex in the module case. It is complex because the module could be
 297         // in a separate file and there might be attributes in both files, but
 298         // the AST lumps them all together.
 299         let filterd_attrs;
 300         let mut attrs = &item.attrs;
 301         match item.node {
 302             ast::ItemKind::Mod(ref m) => {
 303                 let outer_file = self.codemap.lookup_char_pos(item.span.lo()).file;
 304                 let inner_file = self.codemap.lookup_char_pos(m.inner.lo()).file;
 305                 if outer_file.name == inner_file.name {
 306                     // Module is inline, in this case we treat modules like any
 307                     // other item.
 308                     if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 309                         self.push_rewrite(item.span, None);
 310                         return;
 311                     }
 312                 } else if contains_skip(&item.attrs) {
 313                     // Module is not inline, but should be skipped.
 314                     return;
 315                 } else {
 316                     // Module is not inline and should not be skipped. We want
 317                     // to process only the attributes in the current file.
 318                     filterd_attrs = item.attrs
 319                         .iter()
 320                         .filter_map(|a| {
 321                             let attr_file = self.codemap.lookup_char_pos(a.span.lo()).file;
 322                             if attr_file.name == outer_file.name {
 323                                 Some(a.clone())
 324                             } else {
 325                                 None
 326                             }
 327                         })
 328                         .collect::<Vec<_>>();
 329                     // Assert because if we should skip it should be caught by
 330                     // the above case.
 331                     assert!(!self.visit_attrs(&filterd_attrs, ast::AttrStyle::Outer));
 332                     attrs = &filterd_attrs;
 333                 }
 334             }
 335             _ => if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 336                 self.push_rewrite(item.span, None);
 337                 return;
 338             },
 339         }
 340
 341         match item.node {
 342             ast::ItemKind::Use(ref vp) => self.format_import(item, vp),
 343             ast::ItemKind::Impl(..) => {
 344                 let snippet = self.snippet(item.span);
 345                 let where_span_end = snippet
 346                     .find_uncommented("{")
 347                     .map(|x| (BytePos(x as u32)) + source!(self, item.span).lo());
 348                 let rw = format_impl(&self.get_context(), item, self.block_indent, where_span_end);
 349                 self.push_rewrite(item.span, rw);
 350             }
 351             ast::ItemKind::Trait(..) => {
 352                 let rw = format_trait(&self.get_context(), item, self.block_indent);
 353                 self.push_rewrite(item.span, rw);
 354             }
 355             ast::ItemKind::ExternCrate(_) => {
 356                 let rw = rewrite_extern_crate(&self.get_context(), item);
 357                 self.push_rewrite(item.span, rw);
 358             }
 359             ast::ItemKind::Struct(ref def, ref generics) => {
 360                 let rewrite = format_struct(
 361                     &self.get_context(),
 362                     "struct ",
 363                     item.ident,
 364                     &item.vis,
 365                     def,
 366                     Some(generics),
 367                     item.span,
 368                     self.block_indent,
 369                     None,
 370                 ).map(|s| match *def {
 371                     ast::VariantData::Tuple(..) => s + ";",
 372                     _ => s,
 373                 });
 374                 self.push_rewrite(item.span, rewrite);
 375             }
 376             ast::ItemKind::Enum(ref def, ref generics) => {
 377                 self.format_missing_with_indent(source!(self, item.span).lo());
 378                 self.visit_enum(item.ident, &item.vis, def, generics, item.span);
 379                 self.last_pos = source!(self, item.span).hi();
 380             }
 381             ast::ItemKind::Mod(ref module) => {
 382                 self.format_missing_with_indent(source!(self, item.span).lo());
 383                 self.format_mod(module, &item.vis, item.span, item.ident, attrs);
 384             }
 385             ast::ItemKind::Mac(ref mac) => {
 386                 self.visit_mac(mac, Some(item.ident), MacroPosition::Item);
 387             }
 388             ast::ItemKind::ForeignMod(ref foreign_mod) => {
 389                 self.format_missing_with_indent(source!(self, item.span).lo());
 390                 self.format_foreign_mod(foreign_mod, item.span);
 391             }
 392             ast::ItemKind::Static(ref ty, mutability, ref expr) => {
 393                 let rewrite = rewrite_static(
 394                     "static",
 395                     &item.vis,
 396                     item.ident,
 397                     ty,
 398                     mutability,
 399                     Some(expr),
 400                     self.block_indent,
 401                     item.span,
 402                     &self.get_context(),
 403                 );
 404                 self.push_rewrite(item.span, rewrite);
 405             }
 406             ast::ItemKind::Const(ref ty, ref expr) => {
 407                 let rewrite = rewrite_static(
 408                     "const",
 409                     &item.vis,
 410                     item.ident,
 411                     ty,
 412                     ast::Mutability::Immutable,
 413                     Some(expr),
 414                     self.block_indent,
 415                     item.span,
 416                     &self.get_context(),
 417                 );
 418                 self.push_rewrite(item.span, rewrite);
 419             }
 420             ast::ItemKind::DefaultImpl(..) => {
 421                 // FIXME(#78): format impl definitions.
 422             }
 423             ast::ItemKind::Fn(ref decl, unsafety, constness, abi, ref generics, ref body) => {
 424                 self.visit_fn(
 425                     visit::FnKind::ItemFn(
 426                         item.ident,
 427                         generics,
 428                         unsafety,
 429                         constness,
 430                         abi,
 431                         &item.vis,
 432                         body,
 433                     ),
 434                     decl,
 435                     item.span,
 436                     item.id,
 437                     ast::Defaultness::Final,
 438                     Some(&item.attrs),
 439                 )
 440             }
 441             ast::ItemKind::Ty(ref ty, ref generics) => {
 442                 let rewrite = rewrite_type_alias(
 443                     &self.get_context(),
 444                     self.block_indent,
 445                     item.ident,
 446                     ty,
 447                     generics,
 448                     &item.vis,
 449                     item.span,
 450                 );
 451                 self.push_rewrite(item.span, rewrite);
 452             }
 453             ast::ItemKind::Union(ref def, ref generics) => {
 454                 let rewrite = format_struct_struct(
 455                     &self.get_context(),
 456                     "union ",
 457                     item.ident,
 458                     &item.vis,
 459                     def.fields(),
 460                     Some(generics),
 461                     item.span,
 462                     self.block_indent,
 463                     None,
 464                 );
 465                 self.push_rewrite(item.span, rewrite);
 466             }
 467             ast::ItemKind::GlobalAsm(..) => {
 468                 let snippet = Some(self.snippet(item.span));
 469                 self.push_rewrite(item.span, snippet);
 470             }
 471             ast::ItemKind::MacroDef(..) => {
 472                 // FIXME(#1539): macros 2.0
 473                 let mac_snippet = Some(self.snippet(item.span));
 474                 self.push_rewrite(item.span, mac_snippet);
 475             }
 476         }
 477     }
 478
 479     pub fn visit_trait_item(&mut self, ti: &ast::TraitItem) {
 480         skip_out_of_file_lines_range_visitor!(self, ti.span);
 481
 482         if self.visit_attrs(&ti.attrs, ast::AttrStyle::Outer) {
 483             self.push_rewrite(ti.span, None);
 484             return;
 485         }
 486
 487         match ti.node {
 488             ast::TraitItemKind::Const(ref ty, ref expr_opt) => {
 489                 let rewrite = rewrite_static(
 490                     "const",
 491                     &ast::Visibility::Inherited,
 492                     ti.ident,
 493                     ty,
 494                     ast::Mutability::Immutable,
 495                     expr_opt.as_ref(),
 496                     self.block_indent,
 497                     ti.span,
 498                     &self.get_context(),
 499                 );
 500                 self.push_rewrite(ti.span, rewrite);
 501             }
 502             ast::TraitItemKind::Method(ref sig, None) => {
 503                 let indent = self.block_indent;
 504                 let rewrite = self.rewrite_required_fn(indent, ti.ident, sig, ti.span);
 505                 self.push_rewrite(ti.span, rewrite);
 506             }
 507             ast::TraitItemKind::Method(ref sig, Some(ref body)) => {
 508                 self.visit_fn(
 509                     visit::FnKind::Method(ti.ident, sig, None, body),
 510                     &sig.decl,
 511                     ti.span,
 512                     ti.id,
 513                     ast::Defaultness::Final,
 514                     Some(&ti.attrs),
 515                 );
 516             }
 517             ast::TraitItemKind::Type(ref type_param_bounds, ref type_default) => {
 518                 let rewrite = rewrite_associated_type(
 519                     ti.ident,
 520                     type_default.as_ref(),
 521                     Some(type_param_bounds),
 522                     &self.get_context(),
 523                     self.block_indent,
 524                 );
 525                 self.push_rewrite(ti.span, rewrite);
 526             }
 527             ast::TraitItemKind::Macro(ref mac) => {
 528                 self.visit_mac(mac, Some(ti.ident), MacroPosition::Item);
 529             }
 530         }
 531     }
 532
 533     pub fn visit_impl_item(&mut self, ii: &ast::ImplItem) {
 534         skip_out_of_file_lines_range_visitor!(self, ii.span);
 535
 536         if self.visit_attrs(&ii.attrs, ast::AttrStyle::Outer) {
 537             self.push_rewrite(ii.span, None);
 538             return;
 539         }
 540
 541         match ii.node {
 542             ast::ImplItemKind::Method(ref sig, ref body) => {
 543                 self.visit_fn(
 544                     visit::FnKind::Method(ii.ident, sig, Some(&ii.vis), body),
 545                     &sig.decl,
 546                     ii.span,
 547                     ii.id,
 548                     ii.defaultness,
 549                     Some(&ii.attrs),
 550                 );
 551             }
 552             ast::ImplItemKind::Const(ref ty, ref expr) => {
 553                 let rewrite = rewrite_static(
 554                     "const",
 555                     &ii.vis,
 556                     ii.ident,
 557                     ty,
 558                     ast::Mutability::Immutable,
 559                     Some(expr),
 560                     self.block_indent,
 561                     ii.span,
 562                     &self.get_context(),
 563                 );
 564                 self.push_rewrite(ii.span, rewrite);
 565             }
 566             ast::ImplItemKind::Type(ref ty) => {
 567                 let rewrite = rewrite_associated_impl_type(
 568                     ii.ident,
 569                     ii.defaultness,
 570                     Some(ty),
 571                     None,
 572                     &self.get_context(),
 573                     self.block_indent,
 574                 );
 575                 self.push_rewrite(ii.span, rewrite);
 576             }
 577             ast::ImplItemKind::Macro(ref mac) => {
 578                 self.visit_mac(mac, Some(ii.ident), MacroPosition::Item);
 579             }
 580         }
 581     }
 582
 583     fn visit_mac(&mut self, mac: &ast::Mac, ident: Option<ast::Ident>, pos: MacroPosition) {
 584         skip_out_of_file_lines_range_visitor!(self, mac.span);
 585
 586         // 1 = ;
 587         let shape = self.shape().sub_width(1).unwrap();
 588         let rewrite = rewrite_macro(mac, ident, &self.get_context(), shape, pos);
 589         self.push_rewrite(mac.span, rewrite);
 590     }
 591
 592     pub fn push_rewrite(&mut self, span: Span, rewrite: Option<String>) {
 593         self.format_missing_with_indent(source!(self, span).lo());
 594         let result = rewrite.unwrap_or_else(|| self.snippet(span));
 595         self.buffer.push_str(&result);
 596         self.last_pos = source!(self, span).hi();
 597     }
 598
 599     pub fn from_codemap(parse_session: &'a ParseSess, config: &'a Config) -> FmtVisitor<'a> {
 600         FmtVisitor {
 601             parse_session: parse_session,
 602             codemap: parse_session.codemap(),
 603             buffer: StringBuffer::new(),
 604             last_pos: BytePos(0),
 605             block_indent: Indent::empty(),
 606             config: config,
 607             is_if_else_block: false,
 608         }
 609     }
 610
 611     pub fn snippet(&self, span: Span) -> String {
 612         match self.codemap.span_to_snippet(span) {
 613             Ok(s) => s,
 614             Err(_) => {
 615                 println!(
 616                     "Couldn't make snippet for span {:?}->{:?}",
 617                     self.codemap.lookup_char_pos(span.lo()),
 618                     self.codemap.lookup_char_pos(span.hi())
 619                 );
 620                 "".to_owned()
 621             }
 622         }
 623     }
 624
 625     // Returns true if we should skip the following item.
 626     pub fn visit_attrs(&mut self, attrs: &[ast::Attribute], style: ast::AttrStyle) -> bool {
 627         if contains_skip(attrs) {
 628             return true;
 629         }
 630
 631         let attrs: Vec<_> = attrs.iter().filter(|a| a.style == style).cloned().collect();
 632         if attrs.is_empty() {
 633             return false;
 634         }
 635
 636         let rewrite = attrs.rewrite(&self.get_context(), self.shape());
 637         let span = mk_sp(attrs[0].span.lo(), attrs[attrs.len() - 1].span.hi());
 638         self.push_rewrite(span, rewrite);
 639
 640         false
 641     }
 642
 643     fn reorder_items<F>(&mut self, items_left: &[&ast::Item], is_item: &F, in_group: bool) -> usize
 644     where
 645         F: Fn(&ast::Item) -> bool,
 646     {
 647         let mut last = self.codemap.lookup_line_range(items_left[0].span());
 648         let item_length = items_left
 649             .iter()
 650             .take_while(|ppi| {
 651                 is_item(&***ppi) && (!in_group || {
 652                     let current = self.codemap.lookup_line_range(ppi.span());
 653                     let in_same_group = current.lo < last.hi + 2;
 654                     last = current;
 655                     in_same_group
 656                 })
 657             })
 658             .count();
 659         let items = &items_left[..item_length];
 660
 661         let at_least_one_in_file_lines = items
 662             .iter()
 663             .any(|item| !out_of_file_lines_range!(self, item.span));
 664
 665         if at_least_one_in_file_lines {
 666             self.format_imports(items);
 667         } else {
 668             for item in items {
 669                 self.push_rewrite(item.span, None);
 670             }
 671         }
 672
 673         item_length
 674     }
 675
 676     fn walk_items(&mut self, mut items_left: &[&ast::Item]) {
 677         while !items_left.is_empty() {
 678             // If the next item is a `use` declaration, then extract it and any subsequent `use`s
 679             // to be potentially reordered within `format_imports`. Otherwise, just format the
 680             // next item for output.
 681             if self.config.reorder_imports() && is_use_item(&*items_left[0]) {
 682                 let used_items_len = self.reorder_items(
 683                     items_left,
 684                     &is_use_item,
 685                     self.config.reorder_imports_in_group(),
 686                 );
 687                 let (_, rest) = items_left.split_at(used_items_len);
 688                 items_left = rest;
 689             } else if self.config.reorder_extern_crates() && is_extern_crate(&*items_left[0]) {
 690                 let used_items_len = self.reorder_items(
 691                     items_left,
 692                     &is_extern_crate,
 693                     self.config.reorder_extern_crates_in_group(),
 694                 );
 695                 let (_, rest) = items_left.split_at(used_items_len);
 696                 items_left = rest;
 697             } else {
 698                 // `unwrap()` is safe here because we know `items_left`
 699                 // has elements from the loop condition
 700                 let (item, rest) = items_left.split_first().unwrap();
 701                 self.visit_item(item);
 702                 items_left = rest;
 703             }
 704         }
 705     }
 706
 707     fn walk_mod_items(&mut self, m: &ast::Mod) {
 708         self.walk_items(&ptr_vec_to_ref_vec(&m.items));
 709     }
 710
 711     fn walk_stmts(&mut self, stmts: &[ast::Stmt]) {
 712         fn to_stmt_item(stmt: &ast::Stmt) -> Option<&ast::Item> {
 713             match stmt.node {
 714                 ast::StmtKind::Item(ref item) => Some(&**item),
 715                 _ => None,
 716             }
 717         }
 718
 719         if stmts.is_empty() {
 720             return;
 721         }
 722
 723         // Extract leading `use ...;`.
 724         let items: Vec<_> = stmts
 725             .iter()
 726             .take_while(|stmt| to_stmt_item(stmt).is_some())
 727             .filter_map(|stmt| to_stmt_item(stmt))
 728             .take_while(|item| is_use_item(item))
 729             .collect();
 730
 731         if items.is_empty() {
 732             self.visit_stmt(&stmts[0]);
 733             self.walk_stmts(&stmts[1..]);
 734         } else {
 735             self.walk_items(&items);
 736             self.walk_stmts(&stmts[items.len()..]);
 737         }
 738     }
 739
 740     fn walk_block_stmts(&mut self, b: &ast::Block) {
 741         self.walk_stmts(&b.stmts)
 742     }
 743
 744     fn format_mod(
 745         &mut self,
 746         m: &ast::Mod,
 747         vis: &ast::Visibility,
 748         s: Span,
 749         ident: ast::Ident,
 750         attrs: &[ast::Attribute],
 751     ) {
 752         // Decide whether this is an inline mod or an external mod.
 753         let local_file_name = self.codemap.span_to_filename(s);
 754         let inner_span = source!(self, m.inner);
 755         let is_internal = !(inner_span.lo().0 == 0 && inner_span.hi().0 == 0)
 756             && local_file_name == self.codemap.span_to_filename(inner_span);
 757
 758         self.buffer.push_str(&*utils::format_visibility(vis));
 759         self.buffer.push_str("mod ");
 760         self.buffer.push_str(&ident.to_string());
 761
 762         if is_internal {
 763             match self.config.item_brace_style() {
 764                 BraceStyle::AlwaysNextLine => self.buffer
 765                     .push_str(&format!("\n{}{{", self.block_indent.to_string(self.config))),
 766                 _ => self.buffer.push_str(" {"),
 767             }
 768             // Hackery to account for the closing }.
 769             let mod_lo = self.codemap.span_after(source!(self, s), "{");
 770             let body_snippet =
 771                 self.snippet(mk_sp(mod_lo, source!(self, m.inner).hi() - BytePos(1)));
 772             let body_snippet = body_snippet.trim();
 773             if body_snippet.is_empty() {
 774                 self.buffer.push_str("}");
 775             } else {
 776                 self.last_pos = mod_lo;
 777                 self.block_indent = self.block_indent.block_indent(self.config);
 778                 self.visit_attrs(attrs, ast::AttrStyle::Inner);
 779                 self.walk_mod_items(m);
 780                 self.format_missing_with_indent(source!(self, m.inner).hi() - BytePos(1));
 781                 self.close_block(false);
 782             }
 783             self.last_pos = source!(self, m.inner).hi();
 784         } else {
 785             self.buffer.push_str(";");
 786             self.last_pos = source!(self, s).hi();
 787         }
 788     }
 789
 790     pub fn format_separate_mod(&mut self, m: &ast::Mod, filemap: &codemap::FileMap) {
 791         self.block_indent = Indent::empty();
 792         self.walk_mod_items(m);
 793         self.format_missing_with_indent(filemap.end_pos);
 794     }
 795
 796     pub fn get_context(&self) -> RewriteContext {
 797         RewriteContext {
 798             parse_session: self.parse_session,
 799             codemap: self.codemap,
 800             config: self.config,
 801             inside_macro: false,
 802             use_block: false,
 803             is_if_else_block: false,
 804             force_one_line_chain: false,
 805         }
 806     }
 807 }
 808
 809 impl Rewrite for ast::NestedMetaItem {
 810     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 811         match self.node {
 812             ast::NestedMetaItemKind::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
 813             ast::NestedMetaItemKind::Literal(..) => Some(context.snippet(self.span)),
 814         }
 815     }
 816 }
 817
 818 impl Rewrite for ast::MetaItem {
 819     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 820         Some(match self.node {
 821             ast::MetaItemKind::Word => String::from(&*self.name.as_str()),
 822             ast::MetaItemKind::List(ref list) => {
 823                 let name = self.name.as_str();
 824                 // 3 = `#[` and `(`, 2 = `]` and `)`
 825                 let item_shape = try_opt!(
 826                     shape
 827                         .shrink_left(name.len() + 3)
 828                         .and_then(|s| s.sub_width(2))
 829                 );
 830                 let items = itemize_list(
 831                     context.codemap,
 832                     list.iter(),
 833                     ")",
 834                     |nested_meta_item| nested_meta_item.span.lo(),
 835                     |nested_meta_item| nested_meta_item.span.hi(),
 836                     |nested_meta_item| nested_meta_item.rewrite(context, item_shape),
 837                     self.span.lo(),
 838                     self.span.hi(),
 839                     false,
 840                 );
 841                 let item_vec = items.collect::<Vec<_>>();
 842                 let fmt = ListFormatting {
 843                     tactic: DefinitiveListTactic::Mixed,
 844                     separator: ",",
 845                     trailing_separator: SeparatorTactic::Never,
 846                     separator_place: SeparatorPlace::Back,
 847                     shape: item_shape,
 848                     ends_with_newline: false,
 849                     preserve_newline: false,
 850                     config: context.config,
 851                 };
 852                 format!("{}({})", name, try_opt!(write_list(&item_vec, &fmt)))
 853             }
 854             ast::MetaItemKind::NameValue(ref literal) => {
 855                 let name = self.name.as_str();
 856                 let value = context.snippet(literal.span);
 857                 if &*name == "doc" && contains_comment(&value) {
 858                     let doc_shape = Shape {
 859                         width: cmp::min(shape.width, context.config.comment_width())
 860                             .checked_sub(shape.indent.width())
 861                             .unwrap_or(0),
 862                         ..shape
 863                     };
 864                     try_opt!(rewrite_comment(&value, false, doc_shape, context.config))
 865                 } else {
 866                     format!("{} = {}", name, value)
 867                 }
 868             }
 869         })
 870     }
 871 }
 872
 873 impl Rewrite for ast::Attribute {
 874     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 875         try_opt!(self.meta())
 876             .rewrite(context, shape)
 877             .map(|rw| if self.is_sugared_doc {
 878                 rw
 879             } else {
 880                 let original = context.snippet(self.span);
 881                 let prefix = match self.style {
 882                     ast::AttrStyle::Inner => "#!",
 883                     ast::AttrStyle::Outer => "#",
 884                 };
 885                 if contains_comment(&original) {
 886                     original
 887                 } else {
 888                     format!("{}[{}]", prefix, rw)
 889                 }
 890             })
 891     }
 892 }
 893
 894 impl<'a> Rewrite for [ast::Attribute] {
 895     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 896         if self.is_empty() {
 897             return Some(String::new());
 898         }
 899         let mut result = String::with_capacity(128);
 900         let indent = shape.indent.to_string(context.config);
 901
 902         let mut derive_args = Vec::new();
 903
 904         let mut iter = self.iter().enumerate().peekable();
 905         let mut insert_new_line = true;
 906         let mut is_prev_sugared_doc = false;
 907         while let Some((i, a)) = iter.next() {
 908             let a_str = try_opt!(a.rewrite(context, shape));
 909
 910             // Write comments and blank lines between attributes.
 911             if i > 0 {
 912                 let comment = context.snippet(mk_sp(self[i - 1].span.hi(), a.span.lo()));
 913                 // This particular horror show is to preserve line breaks in between doc
 914                 // comments. An alternative would be to force such line breaks to start
 915                 // with the usual doc comment token.
 916                 let (multi_line_before, multi_line_after) = if a.is_sugared_doc
 917                     || is_prev_sugared_doc
 918                 {
 919                     // Look at before and after comment and see if there are any empty lines.
 920                     let comment_begin = comment.chars().position(|c| c == '/');
 921                     let len = comment_begin.unwrap_or_else(|| comment.len());
 922                     let mlb = comment.chars().take(len).filter(|c| *c == '\n').count() > 1;
 923                     let mla = if comment_begin.is_none() {
 924                         mlb
 925                     } else {
 926                         let comment_end = comment.chars().rev().position(|c| !c.is_whitespace());
 927                         let len = comment_end.unwrap();
 928                         comment
 929                             .chars()
 930                             .rev()
 931                             .take(len)
 932                             .filter(|c| *c == '\n')
 933                             .count() > 1
 934                     };
 935                     (mlb, mla)
 936                 } else {
 937                     (false, false)
 938                 };
 939
 940                 let comment = try_opt!(recover_missing_comment_in_span(
 941                     mk_sp(self[i - 1].span.hi(), a.span.lo()),
 942                     shape.with_max_width(context.config),
 943                     context,
 944                     0,
 945                 ));
 946
 947                 if !comment.is_empty() {
 948                     if multi_line_before {
 949                         result.push('\n');
 950                     }
 951                     result.push_str(&comment);
 952                     result.push('\n');
 953                     if multi_line_after {
 954                         result.push('\n')
 955                     }
 956                 } else if insert_new_line {
 957                     result.push('\n');
 958                     if multi_line_after {
 959                         result.push('\n')
 960                     }
 961                 }
 962
 963                 if derive_args.is_empty() {
 964                     result.push_str(&indent);
 965                 }
 966
 967                 insert_new_line = true;
 968             }
 969
 970             // Write the attribute itself.
 971             if context.config.merge_derives() {
 972                 // If the attribute is `#[derive(...)]`, take the arguments.
 973                 if let Some(mut args) = get_derive_args(context, a) {
 974                     derive_args.append(&mut args);
 975                     match iter.peek() {
 976                         // If the next attribute is `#[derive(...)]` as well, skip rewriting.
 977                         Some(&(_, next_attr)) if is_derive(next_attr) => insert_new_line = false,
 978                         // If not, rewrite the merged derives.
 979                         _ => {
 980                             result.push_str(&try_opt!(format_derive(context, &derive_args, shape)));
 981                             derive_args.clear();
 982                         }
 983                     }
 984                 } else {
 985                     result.push_str(&a_str);
 986                 }
 987             } else {
 988                 result.push_str(&a_str);
 989             }
 990
 991             is_prev_sugared_doc = a.is_sugared_doc;
 992         }
 993         Some(result)
 994     }
 995 }
 996
 997 // Format `#[derive(..)]`, using visual indent & mixed style when we need to go multiline.
 998 fn format_derive(context: &RewriteContext, derive_args: &[String], shape: Shape) -> Option<String> {
 999     let mut result = String::with_capacity(128);
1000     result.push_str("#[derive(");
1001     // 11 = `#[derive()]`
1002     let initial_budget = try_opt!(shape.width.checked_sub(11));
1003     let mut budget = initial_budget;
1004     let num = derive_args.len();
1005     for (i, a) in derive_args.iter().enumerate() {
1006         // 2 = `, ` or `)]`
1007         let width = a.len() + 2;
1008         if width > budget {
1009             if i > 0 {
1010                 // Remove trailing whitespace.
1011                 result.pop();
1012             }
1013             result.push('\n');
1014             // 9 = `#[derive(`
1015             result.push_str(&(shape.indent + 9).to_string(context.config));
1016             budget = initial_budget;
1017         } else {
1018             budget = budget.checked_sub(width).unwrap_or(0);
1019         }
1020         result.push_str(a);
1021         if i != num - 1 {
1022             result.push_str(", ")
1023         }
1024     }
1025     result.push_str(")]");
1026     Some(result)
1027 }
1028
1029 fn is_derive(attr: &ast::Attribute) -> bool {
1030     match attr.meta() {
1031         Some(meta_item) => match meta_item.node {
1032             ast::MetaItemKind::List(..) => meta_item.name.as_str() == "derive",
1033             _ => false,
1034         },
1035         _ => false,
1036     }
1037 }
1038
1039 /// Returns the arguments of `#[derive(...)]`.
1040 fn get_derive_args(context: &RewriteContext, attr: &ast::Attribute) -> Option<Vec<String>> {
1041     attr.meta().and_then(|meta_item| match meta_item.node {
1042         ast::MetaItemKind::List(ref args) if meta_item.name.as_str() == "derive" => {
1043             // Every argument of `derive` should be `NestedMetaItemKind::Literal`.
1044             Some(
1045                 args.iter()
1046                     .map(|a| context.snippet(a.span))
1047                     .collect::<Vec<_>>(),
1048             )
1049         }
1050         _ => None,
1051     })
1052 }
1053
1054 // Rewrite `extern crate foo;` WITHOUT attributes.
1055 pub fn rewrite_extern_crate(context: &RewriteContext, item: &ast::Item) -> Option<String> {
1056     assert!(is_extern_crate(item));
1057     let new_str = context.snippet(item.span);
1058     Some(if contains_comment(&new_str) {
1059         new_str
1060     } else {
1061         let no_whitespace = &new_str.split_whitespace().collect::<Vec<&str>>().join(" ");
1062         String::from(&*Regex::new(r"\s;").unwrap().replace(no_whitespace, ";"))
1063     })
1064 }