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