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