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