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, CodeCharKind, CommentCodeSlices, FindUncommented};
  22 use comment::rewrite_comment;
  23 use config::{BraceStyle, Config};
  24 use expr::{format_expr, ExprType};
  25 use items::{format_impl, format_trait, rewrite_associated_impl_type, rewrite_associated_type,
  26             rewrite_static, rewrite_type_alias};
  27 use lists::{itemize_list, write_list, DefinitiveListTactic, ListFormatting, SeparatorPlace,
  28             SeparatorTactic};
  29 use macros::{rewrite_macro, MacroPosition};
  30 use regex::Regex;
  31 use rewrite::{Rewrite, RewriteContext};
  32 use utils::{self, contains_skip, mk_sp};
  33
  34 fn is_use_item(item: &ast::Item) -> bool {
  35     match item.node {
  36         ast::ItemKind::Use(_) => true,
  37         _ => false,
  38     }
  39 }
  40
  41 fn is_extern_crate(item: &ast::Item) -> bool {
  42     match item.node {
  43         ast::ItemKind::ExternCrate(..) => true,
  44         _ => false,
  45     }
  46 }
  47
  48 pub struct FmtVisitor<'a> {
  49     pub parse_session: &'a ParseSess,
  50     pub codemap: &'a CodeMap,
  51     pub buffer: StringBuffer,
  52     pub last_pos: BytePos,
  53     // FIXME: use an RAII util or closure for indenting
  54     pub block_indent: Indent,
  55     pub config: &'a Config,
  56     pub is_if_else_block: bool,
  57 }
  58
  59 impl<'a> FmtVisitor<'a> {
  60     fn visit_stmt(&mut self, stmt: &ast::Stmt) {
  61         debug!(
  62             "visit_stmt: {:?} {:?}",
  63             self.codemap.lookup_char_pos(stmt.span.lo),
  64             self.codemap.lookup_char_pos(stmt.span.hi)
  65         );
  66
  67         match stmt.node {
  68             ast::StmtKind::Item(ref item) => {
  69                 self.visit_item(item);
  70             }
  71             ast::StmtKind::Local(ref local) => {
  72                 let rewrite = if contains_skip(&local.attrs) {
  73                     None
  74                 } else {
  75                     stmt.rewrite(
  76                         &self.get_context(),
  77                         Shape::indented(self.block_indent, self.config),
  78                     )
  79                 };
  80                 self.push_rewrite(stmt.span, rewrite);
  81             }
  82             ast::StmtKind::Expr(ref expr) => {
  83                 let rewrite = format_expr(
  84                     expr,
  85                     ExprType::Statement,
  86                     &self.get_context(),
  87                     Shape::indented(self.block_indent, self.config),
  88                 );
  89                 let span = if expr.attrs.is_empty() {
  90                     stmt.span
  91                 } else {
  92                     mk_sp(expr.span().lo, stmt.span.hi)
  93                 };
  94                 self.push_rewrite(span, rewrite)
  95             }
  96             ast::StmtKind::Semi(ref expr) => {
  97                 let rewrite = stmt.rewrite(
  98                     &self.get_context(),
  99                     Shape::indented(self.block_indent, self.config),
 100                 );
 101                 let span = if expr.attrs.is_empty() {
 102                     stmt.span
 103                 } else {
 104                     mk_sp(expr.span().lo, stmt.span.hi)
 105                 };
 106                 self.push_rewrite(span, rewrite)
 107             }
 108             ast::StmtKind::Mac(ref mac) => {
 109                 let (ref mac, _macro_style, ref attrs) = **mac;
 110                 if contains_skip(attrs) {
 111                     self.push_rewrite(mac.span, None);
 112                 } else {
 113                     self.visit_mac(mac, None, MacroPosition::Statement);
 114                 }
 115                 self.format_missing(stmt.span.hi);
 116             }
 117         }
 118     }
 119
 120     pub fn visit_block(&mut self, b: &ast::Block, inner_attrs: Option<&[ast::Attribute]>) {
 121         debug!(
 122             "visit_block: {:?} {:?}",
 123             self.codemap.lookup_char_pos(b.span.lo),
 124             self.codemap.lookup_char_pos(b.span.hi)
 125         );
 126
 127         // Check if this block has braces.
 128         let snippet = self.snippet(b.span);
 129         let has_braces = snippet.starts_with('{') || snippet.starts_with("unsafe");
 130         let brace_compensation = if has_braces { BytePos(1) } else { BytePos(0) };
 131
 132         self.last_pos = self.last_pos + brace_compensation;
 133         self.block_indent = self.block_indent.block_indent(self.config);
 134         self.buffer.push_str("{");
 135
 136         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 137             if let Some(first_stmt) = b.stmts.first() {
 138                 let attr_lo = inner_attrs
 139                     .and_then(|attrs| {
 140                         utils::inner_attributes(attrs)
 141                             .first()
 142                             .map(|attr| attr.span.lo)
 143                     })
 144                     .or_else(|| {
 145                         // Attributes for an item in a statement position
 146                         // do not belong to the statement. (rust-lang/rust#34459)
 147                         if let ast::StmtKind::Item(ref item) = first_stmt.node {
 148                             item.attrs.first()
 149                         } else {
 150                             first_stmt.attrs().first()
 151                         }.and_then(|attr| {
 152                             // Some stmts can have embedded attributes.
 153                             // e.g. `match { #![attr] ... }`
 154                             let attr_lo = attr.span.lo;
 155                             if attr_lo < first_stmt.span.lo {
 156                                 Some(attr_lo)
 157                             } else {
 158                                 None
 159                             }
 160                         })
 161                     });
 162
 163                 let snippet =
 164                     self.snippet(mk_sp(self.last_pos, attr_lo.unwrap_or(first_stmt.span.lo)));
 165                 let len = CommentCodeSlices::new(&snippet).nth(0).and_then(
 166                     |(kind, _, s)| if kind == CodeCharKind::Normal {
 167                         s.rfind('\n')
 168                     } else {
 169                         None
 170                     },
 171                 );
 172                 if let Some(len) = len {
 173                     self.last_pos = self.last_pos + BytePos::from_usize(len);
 174                 }
 175             }
 176         }
 177
 178         // Format inner attributes if available.
 179         if let Some(attrs) = inner_attrs {
 180             self.visit_attrs(attrs, ast::AttrStyle::Inner);
 181         }
 182
 183         for stmt in &b.stmts {
 184             self.visit_stmt(stmt)
 185         }
 186
 187         if !b.stmts.is_empty() {
 188             if let Some(expr) = utils::stmt_expr(&b.stmts[b.stmts.len() - 1]) {
 189                 if utils::semicolon_for_expr(&self.get_context(), expr) {
 190                     self.buffer.push_str(";");
 191                 }
 192             }
 193         }
 194
 195         let mut remove_len = BytePos(0);
 196         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 197             if let Some(stmt) = b.stmts.last() {
 198                 let snippet = self.snippet(mk_sp(
 199                     stmt.span.hi,
 200                     source!(self, b.span).hi - brace_compensation,
 201                 ));
 202                 let len = CommentCodeSlices::new(&snippet)
 203                     .last()
 204                     .and_then(|(kind, _, s)| {
 205                         if kind == CodeCharKind::Normal && s.trim().is_empty() {
 206                             Some(s.len())
 207                         } else {
 208                             None
 209                         }
 210                     });
 211                 if let Some(len) = len {
 212                     remove_len = BytePos::from_usize(len);
 213                 }
 214             }
 215         }
 216
 217         let mut unindent_comment = self.is_if_else_block && !b.stmts.is_empty();
 218         if unindent_comment {
 219             let end_pos = source!(self, b.span).hi - brace_compensation - remove_len;
 220             let snippet = self.get_context().snippet(mk_sp(self.last_pos, end_pos));
 221             unindent_comment = snippet.contains("//") || snippet.contains("/*");
 222         }
 223         // FIXME: we should compress any newlines here to just one
 224         if unindent_comment {
 225             self.block_indent = self.block_indent.block_unindent(self.config);
 226         }
 227         self.format_missing_with_indent(source!(self, b.span).hi - brace_compensation - remove_len);
 228         if unindent_comment {
 229             self.block_indent = self.block_indent.block_indent(self.config);
 230         }
 231         self.close_block(unindent_comment);
 232         self.last_pos = source!(self, b.span).hi;
 233     }
 234
 235     // FIXME: this is a terrible hack to indent the comments between the last
 236     // item in the block and the closing brace to the block's level.
 237     // The closing brace itself, however, should be indented at a shallower
 238     // level.
 239     fn close_block(&mut self, unindent_comment: bool) {
 240         let total_len = self.buffer.len;
 241         let chars_too_many = if unindent_comment {
 242             0
 243         } else if self.config.hard_tabs() {
 244             1
 245         } else {
 246             self.config.tab_spaces()
 247         };
 248         self.buffer.truncate(total_len - chars_too_many);
 249         self.buffer.push_str("}");
 250         self.block_indent = self.block_indent.block_unindent(self.config);
 251     }
 252
 253     // Note that this only gets called for function definitions. Required methods
 254     // on traits do not get handled here.
 255     fn visit_fn(
 256         &mut self,
 257         fk: visit::FnKind,
 258         fd: &ast::FnDecl,
 259         s: Span,
 260         _: ast::NodeId,
 261         defaultness: ast::Defaultness,
 262         inner_attrs: Option<&[ast::Attribute]>,
 263     ) {
 264         let indent = self.block_indent;
 265         let block;
 266         let rewrite = match fk {
 267             visit::FnKind::ItemFn(ident, generics, unsafety, constness, abi, vis, b) => {
 268                 block = b;
 269                 self.rewrite_fn(
 270                     indent,
 271                     ident,
 272                     fd,
 273                     generics,
 274                     unsafety,
 275                     constness.node,
 276                     defaultness,
 277                     abi,
 278                     vis,
 279                     mk_sp(s.lo, b.span.lo),
 280                     &b,
 281                 )
 282             }
 283             visit::FnKind::Method(ident, sig, vis, b) => {
 284                 block = b;
 285                 self.rewrite_fn(
 286                     indent,
 287                     ident,
 288                     fd,
 289                     &sig.generics,
 290                     sig.unsafety,
 291                     sig.constness.node,
 292                     defaultness,
 293                     sig.abi,
 294                     vis.unwrap_or(&ast::Visibility::Inherited),
 295                     mk_sp(s.lo, b.span.lo),
 296                     &b,
 297                 )
 298             }
 299             visit::FnKind::Closure(_) => unreachable!(),
 300         };
 301
 302         if let Some(fn_str) = rewrite {
 303             self.format_missing_with_indent(source!(self, s).lo);
 304             self.buffer.push_str(&fn_str);
 305             if let Some(c) = fn_str.chars().last() {
 306                 if c == '}' {
 307                     self.last_pos = source!(self, block.span).hi;
 308                     return;
 309                 }
 310             }
 311         } else {
 312             self.format_missing(source!(self, block.span).lo);
 313         }
 314
 315         self.last_pos = source!(self, block.span).lo;
 316         self.visit_block(block, inner_attrs)
 317     }
 318
 319     pub fn visit_item(&mut self, item: &ast::Item) {
 320         skip_out_of_file_lines_range_visitor!(self, item.span);
 321
 322         // This is where we bail out if there is a skip attribute. This is only
 323         // complex in the module case. It is complex because the module could be
 324         // in a separate file and there might be attributes in both files, but
 325         // the AST lumps them all together.
 326         let mut attrs = item.attrs.clone();
 327         match item.node {
 328             ast::ItemKind::Mod(ref m) => {
 329                 let outer_file = self.codemap.lookup_char_pos(item.span.lo).file;
 330                 let inner_file = self.codemap.lookup_char_pos(m.inner.lo).file;
 331                 if outer_file.name == inner_file.name {
 332                     // Module is inline, in this case we treat modules like any
 333                     // other item.
 334                     if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 335                         self.push_rewrite(item.span, None);
 336                         return;
 337                     }
 338                 } else if utils::contains_skip(&item.attrs) {
 339                     // Module is not inline, but should be skipped.
 340                     return;
 341                 } else {
 342                     // Module is not inline and should not be skipped. We want
 343                     // to process only the attributes in the current file.
 344                     let filterd_attrs = item.attrs
 345                         .iter()
 346                         .filter_map(|a| {
 347                             let attr_file = self.codemap.lookup_char_pos(a.span.lo).file;
 348                             if attr_file.name == outer_file.name {
 349                                 Some(a.clone())
 350                             } else {
 351                                 None
 352                             }
 353                         })
 354                         .collect::<Vec<_>>();
 355                     // Assert because if we should skip it should be caught by
 356                     // the above case.
 357                     assert!(!self.visit_attrs(&filterd_attrs, ast::AttrStyle::Outer));
 358                     attrs = filterd_attrs;
 359                 }
 360             }
 361             _ => if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 362                 self.push_rewrite(item.span, None);
 363                 return;
 364             },
 365         }
 366
 367         match item.node {
 368             ast::ItemKind::Use(ref vp) => {
 369                 self.format_import(&item.vis, vp, item.span, &item.attrs);
 370             }
 371             ast::ItemKind::Impl(..) => {
 372                 self.format_missing_with_indent(source!(self, item.span).lo);
 373                 let snippet = self.get_context().snippet(item.span);
 374                 let where_span_end = snippet
 375                     .find_uncommented("{")
 376                     .map(|x| (BytePos(x as u32)) + source!(self, item.span).lo);
 377                 if let Some(impl_str) =
 378                     format_impl(&self.get_context(), item, self.block_indent, where_span_end)
 379                 {
 380                     self.buffer.push_str(&impl_str);
 381                     self.last_pos = source!(self, item.span).hi;
 382                 }
 383             }
 384             ast::ItemKind::Trait(..) => {
 385                 self.format_missing_with_indent(item.span.lo);
 386                 if let Some(trait_str) = format_trait(&self.get_context(), item, self.block_indent)
 387                 {
 388                     self.buffer.push_str(&trait_str);
 389                     self.last_pos = source!(self, item.span).hi;
 390                 }
 391             }
 392             ast::ItemKind::ExternCrate(_) => {
 393                 self.format_missing_with_indent(source!(self, item.span).lo);
 394                 let new_str = self.snippet(item.span);
 395                 if contains_comment(&new_str) {
 396                     self.buffer.push_str(&new_str)
 397                 } else {
 398                     let no_whitespace =
 399                         &new_str.split_whitespace().collect::<Vec<&str>>().join(" ");
 400                     self.buffer
 401                         .push_str(&Regex::new(r"\s;").unwrap().replace(no_whitespace, ";"));
 402                 }
 403                 self.last_pos = source!(self, item.span).hi;
 404             }
 405             ast::ItemKind::Struct(ref def, ref generics) => {
 406                 let rewrite = {
 407                     let indent = self.block_indent;
 408                     let context = self.get_context();
 409                     ::items::format_struct(
 410                         &context,
 411                         "struct ",
 412                         item.ident,
 413                         &item.vis,
 414                         def,
 415                         Some(generics),
 416                         item.span,
 417                         indent,
 418                         None,
 419                     ).map(|s| match *def {
 420                         ast::VariantData::Tuple(..) => s + ";",
 421                         _ => s,
 422                     })
 423                 };
 424                 self.push_rewrite(item.span, rewrite);
 425             }
 426             ast::ItemKind::Enum(ref def, ref generics) => {
 427                 self.format_missing_with_indent(source!(self, item.span).lo);
 428                 self.visit_enum(item.ident, &item.vis, def, generics, item.span);
 429                 self.last_pos = source!(self, item.span).hi;
 430             }
 431             ast::ItemKind::Mod(ref module) => {
 432                 self.format_missing_with_indent(source!(self, item.span).lo);
 433                 self.format_mod(module, &item.vis, item.span, item.ident, &attrs);
 434             }
 435             ast::ItemKind::Mac(ref mac) => {
 436                 self.visit_mac(mac, Some(item.ident), MacroPosition::Item);
 437             }
 438             ast::ItemKind::ForeignMod(ref foreign_mod) => {
 439                 self.format_missing_with_indent(source!(self, item.span).lo);
 440                 self.format_foreign_mod(foreign_mod, item.span);
 441             }
 442             ast::ItemKind::Static(ref ty, mutability, ref expr) => {
 443                 let rewrite = rewrite_static(
 444                     "static",
 445                     &item.vis,
 446                     item.ident,
 447                     ty,
 448                     mutability,
 449                     Some(expr),
 450                     self.block_indent,
 451                     item.span,
 452                     &self.get_context(),
 453                 );
 454                 self.push_rewrite(item.span, rewrite);
 455             }
 456             ast::ItemKind::Const(ref ty, ref expr) => {
 457                 let rewrite = rewrite_static(
 458                     "const",
 459                     &item.vis,
 460                     item.ident,
 461                     ty,
 462                     ast::Mutability::Immutable,
 463                     Some(expr),
 464                     self.block_indent,
 465                     item.span,
 466                     &self.get_context(),
 467                 );
 468                 self.push_rewrite(item.span, rewrite);
 469             }
 470             ast::ItemKind::DefaultImpl(..) => {
 471                 // FIXME(#78): format impl definitions.
 472             }
 473             ast::ItemKind::Fn(ref decl, unsafety, constness, abi, ref generics, ref body) => {
 474                 self.visit_fn(
 475                     visit::FnKind::ItemFn(
 476                         item.ident,
 477                         generics,
 478                         unsafety,
 479                         constness,
 480                         abi,
 481                         &item.vis,
 482                         body,
 483                     ),
 484                     decl,
 485                     item.span,
 486                     item.id,
 487                     ast::Defaultness::Final,
 488                     Some(&item.attrs),
 489                 )
 490             }
 491             ast::ItemKind::Ty(ref ty, ref generics) => {
 492                 let rewrite = rewrite_type_alias(
 493                     &self.get_context(),
 494                     self.block_indent,
 495                     item.ident,
 496                     ty,
 497                     generics,
 498                     &item.vis,
 499                     item.span,
 500                 );
 501                 self.push_rewrite(item.span, rewrite);
 502             }
 503             ast::ItemKind::Union(ref def, ref generics) => {
 504                 let rewrite = ::items::format_struct_struct(
 505                     &self.get_context(),
 506                     "union ",
 507                     item.ident,
 508                     &item.vis,
 509                     def.fields(),
 510                     Some(generics),
 511                     item.span,
 512                     self.block_indent,
 513                     None,
 514                 );
 515                 self.push_rewrite(item.span, rewrite);
 516             }
 517             ast::ItemKind::GlobalAsm(..) => {
 518                 let snippet = Some(self.snippet(item.span));
 519                 self.push_rewrite(item.span, snippet);
 520             }
 521             ast::ItemKind::MacroDef(..) => {
 522                 // FIXME(#1539): macros 2.0
 523                 let snippet = Some(self.snippet(item.span));
 524                 self.push_rewrite(item.span, snippet);
 525             }
 526         }
 527     }
 528
 529     pub fn visit_trait_item(&mut self, ti: &ast::TraitItem) {
 530         skip_out_of_file_lines_range_visitor!(self, ti.span);
 531
 532         if self.visit_attrs(&ti.attrs, ast::AttrStyle::Outer) {
 533             self.push_rewrite(ti.span, None);
 534             return;
 535         }
 536
 537         match ti.node {
 538             ast::TraitItemKind::Const(ref ty, ref expr_opt) => {
 539                 let rewrite = rewrite_static(
 540                     "const",
 541                     &ast::Visibility::Inherited,
 542                     ti.ident,
 543                     ty,
 544                     ast::Mutability::Immutable,
 545                     expr_opt.as_ref(),
 546                     self.block_indent,
 547                     ti.span,
 548                     &self.get_context(),
 549                 );
 550                 self.push_rewrite(ti.span, rewrite);
 551             }
 552             ast::TraitItemKind::Method(ref sig, None) => {
 553                 let indent = self.block_indent;
 554                 let rewrite = self.rewrite_required_fn(indent, ti.ident, sig, ti.span);
 555                 self.push_rewrite(ti.span, rewrite);
 556             }
 557             ast::TraitItemKind::Method(ref sig, Some(ref body)) => {
 558                 self.visit_fn(
 559                     visit::FnKind::Method(ti.ident, sig, None, body),
 560                     &sig.decl,
 561                     ti.span,
 562                     ti.id,
 563                     ast::Defaultness::Final,
 564                     Some(&ti.attrs),
 565                 );
 566             }
 567             ast::TraitItemKind::Type(ref type_param_bounds, ref type_default) => {
 568                 let rewrite = rewrite_associated_type(
 569                     ti.ident,
 570                     type_default.as_ref(),
 571                     Some(type_param_bounds),
 572                     &self.get_context(),
 573                     self.block_indent,
 574                 );
 575                 self.push_rewrite(ti.span, rewrite);
 576             }
 577             ast::TraitItemKind::Macro(ref mac) => {
 578                 self.visit_mac(mac, Some(ti.ident), MacroPosition::Item);
 579             }
 580         }
 581     }
 582
 583     pub fn visit_impl_item(&mut self, ii: &ast::ImplItem) {
 584         skip_out_of_file_lines_range_visitor!(self, ii.span);
 585
 586         if self.visit_attrs(&ii.attrs, ast::AttrStyle::Outer) {
 587             self.push_rewrite(ii.span, None);
 588             return;
 589         }
 590
 591         match ii.node {
 592             ast::ImplItemKind::Method(ref sig, ref body) => {
 593                 self.visit_fn(
 594                     visit::FnKind::Method(ii.ident, sig, Some(&ii.vis), body),
 595                     &sig.decl,
 596                     ii.span,
 597                     ii.id,
 598                     ii.defaultness,
 599                     Some(&ii.attrs),
 600                 );
 601             }
 602             ast::ImplItemKind::Const(ref ty, ref expr) => {
 603                 let rewrite = rewrite_static(
 604                     "const",
 605                     &ii.vis,
 606                     ii.ident,
 607                     ty,
 608                     ast::Mutability::Immutable,
 609                     Some(expr),
 610                     self.block_indent,
 611                     ii.span,
 612                     &self.get_context(),
 613                 );
 614                 self.push_rewrite(ii.span, rewrite);
 615             }
 616             ast::ImplItemKind::Type(ref ty) => {
 617                 let rewrite = rewrite_associated_impl_type(
 618                     ii.ident,
 619                     ii.defaultness,
 620                     Some(ty),
 621                     None,
 622                     &self.get_context(),
 623                     self.block_indent,
 624                 );
 625                 self.push_rewrite(ii.span, rewrite);
 626             }
 627             ast::ImplItemKind::Macro(ref mac) => {
 628                 self.visit_mac(mac, Some(ii.ident), MacroPosition::Item);
 629             }
 630         }
 631     }
 632
 633     fn visit_mac(&mut self, mac: &ast::Mac, ident: Option<ast::Ident>, pos: MacroPosition) {
 634         skip_out_of_file_lines_range_visitor!(self, mac.span);
 635
 636         // 1 = ;
 637         let shape = Shape::indented(self.block_indent, self.config)
 638             .sub_width(1)
 639             .unwrap();
 640         let rewrite = rewrite_macro(mac, ident, &self.get_context(), shape, pos);
 641         self.push_rewrite(mac.span, rewrite);
 642     }
 643
 644     fn push_rewrite(&mut self, span: Span, rewrite: Option<String>) {
 645         self.format_missing_with_indent(source!(self, span).lo);
 646         let result = rewrite.unwrap_or_else(|| self.snippet(span));
 647         self.buffer.push_str(&result);
 648         self.last_pos = source!(self, span).hi;
 649     }
 650
 651     pub fn from_codemap(parse_session: &'a ParseSess, config: &'a Config) -> FmtVisitor<'a> {
 652         FmtVisitor {
 653             parse_session: parse_session,
 654             codemap: parse_session.codemap(),
 655             buffer: StringBuffer::new(),
 656             last_pos: BytePos(0),
 657             block_indent: Indent::empty(),
 658             config: config,
 659             is_if_else_block: false,
 660         }
 661     }
 662
 663     pub fn snippet(&self, span: Span) -> String {
 664         match self.codemap.span_to_snippet(span) {
 665             Ok(s) => s,
 666             Err(_) => {
 667                 println!(
 668                     "Couldn't make snippet for span {:?}->{:?}",
 669                     self.codemap.lookup_char_pos(span.lo),
 670                     self.codemap.lookup_char_pos(span.hi)
 671                 );
 672                 "".to_owned()
 673             }
 674         }
 675     }
 676
 677     // Returns true if we should skip the following item.
 678     pub fn visit_attrs(&mut self, attrs: &[ast::Attribute], style: ast::AttrStyle) -> bool {
 679         if utils::contains_skip(attrs) {
 680             return true;
 681         }
 682
 683         let attrs: Vec<_> = attrs.iter().filter(|a| a.style == style).cloned().collect();
 684         if attrs.is_empty() {
 685             return false;
 686         }
 687
 688         let rewrite = attrs.rewrite(
 689             &self.get_context(),
 690             Shape::indented(self.block_indent, self.config),
 691         );
 692         let span = mk_sp(attrs[0].span.lo, attrs[attrs.len() - 1].span.hi);
 693         self.push_rewrite(span, rewrite);
 694
 695         false
 696     }
 697
 698     fn reorder_items<F>(
 699         &mut self,
 700         items_left: &[ptr::P<ast::Item>],
 701         is_item: &F,
 702         in_group: bool,
 703     ) -> usize
 704     where
 705         F: Fn(&ast::Item) -> bool,
 706     {
 707         let mut last = self.codemap.lookup_line_range(items_left[0].span());
 708         let item_length = items_left
 709             .iter()
 710             .take_while(|ppi| {
 711                 is_item(&***ppi) && (!in_group || {
 712                     let current = self.codemap.lookup_line_range(ppi.span());
 713                     let in_same_group = current.lo < last.hi + 2;
 714                     last = current;
 715                     in_same_group
 716                 })
 717             })
 718             .count();
 719         let items = &items_left[..item_length];
 720
 721         let at_least_one_in_file_lines = items
 722             .iter()
 723             .any(|item| !out_of_file_lines_range!(self, item.span));
 724
 725         if at_least_one_in_file_lines {
 726             self.format_imports(items);
 727         } else {
 728             for item in items {
 729                 self.push_rewrite(item.span, None);
 730             }
 731         }
 732
 733         item_length
 734     }
 735
 736     fn walk_mod_items(&mut self, m: &ast::Mod) {
 737         let mut items_left: &[ptr::P<ast::Item>] = &m.items;
 738         while !items_left.is_empty() {
 739             // If the next item is a `use` declaration, then extract it and any subsequent `use`s
 740             // to be potentially reordered within `format_imports`. Otherwise, just format the
 741             // next item for output.
 742             if self.config.reorder_imports() && is_use_item(&*items_left[0]) {
 743                 let used_items_len = self.reorder_items(
 744                     &items_left,
 745                     &is_use_item,
 746                     self.config.reorder_imports_in_group(),
 747                 );
 748                 let (_, rest) = items_left.split_at(used_items_len);
 749                 items_left = rest;
 750             } else if self.config.reorder_extern_crates() && is_extern_crate(&*items_left[0]) {
 751                 let used_items_len = self.reorder_items(
 752                     &items_left,
 753                     &is_extern_crate,
 754                     self.config.reorder_extern_crates_in_group(),
 755                 );
 756                 let (_, rest) = items_left.split_at(used_items_len);
 757                 items_left = rest;
 758             } else {
 759                 // `unwrap()` is safe here because we know `items_left`
 760                 // has elements from the loop condition
 761                 let (item, rest) = items_left.split_first().unwrap();
 762                 self.visit_item(item);
 763                 items_left = rest;
 764             }
 765         }
 766     }
 767
 768     fn format_mod(
 769         &mut self,
 770         m: &ast::Mod,
 771         vis: &ast::Visibility,
 772         s: Span,
 773         ident: ast::Ident,
 774         attrs: &[ast::Attribute],
 775     ) {
 776         // Decide whether this is an inline mod or an external mod.
 777         let local_file_name = self.codemap.span_to_filename(s);
 778         let inner_span = source!(self, m.inner);
 779         let is_internal = !(inner_span.lo.0 == 0 && inner_span.hi.0 == 0) &&
 780             local_file_name == self.codemap.span_to_filename(inner_span);
 781
 782         self.buffer.push_str(&*utils::format_visibility(vis));
 783         self.buffer.push_str("mod ");
 784         self.buffer.push_str(&ident.to_string());
 785
 786         if is_internal {
 787             match self.config.item_brace_style() {
 788                 BraceStyle::AlwaysNextLine => self.buffer
 789                     .push_str(&format!("\n{}{{", self.block_indent.to_string(self.config))),
 790                 _ => self.buffer.push_str(" {"),
 791             }
 792             // Hackery to account for the closing }.
 793             let mod_lo = self.codemap.span_after(source!(self, s), "{");
 794             let body_snippet = self.snippet(mk_sp(mod_lo, source!(self, m.inner).hi - BytePos(1)));
 795             let body_snippet = body_snippet.trim();
 796             if body_snippet.is_empty() {
 797                 self.buffer.push_str("}");
 798             } else {
 799                 self.last_pos = mod_lo;
 800                 self.block_indent = self.block_indent.block_indent(self.config);
 801                 self.visit_attrs(attrs, ast::AttrStyle::Inner);
 802                 self.walk_mod_items(m);
 803                 self.format_missing_with_indent(source!(self, m.inner).hi - BytePos(1));
 804                 self.close_block(false);
 805             }
 806             self.last_pos = source!(self, m.inner).hi;
 807         } else {
 808             self.buffer.push_str(";");
 809             self.last_pos = source!(self, s).hi;
 810         }
 811     }
 812
 813     pub fn format_separate_mod(&mut self, m: &ast::Mod, filemap: &codemap::FileMap) {
 814         self.block_indent = Indent::empty();
 815         self.walk_mod_items(m);
 816         self.format_missing_with_indent(filemap.end_pos);
 817     }
 818
 819     pub fn get_context(&self) -> RewriteContext {
 820         RewriteContext {
 821             parse_session: self.parse_session,
 822             codemap: self.codemap,
 823             config: self.config,
 824             inside_macro: false,
 825             use_block: false,
 826             is_if_else_block: false,
 827             force_one_line_chain: false,
 828         }
 829     }
 830 }
 831
 832 impl Rewrite for ast::NestedMetaItem {
 833     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 834         match self.node {
 835             ast::NestedMetaItemKind::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
 836             ast::NestedMetaItemKind::Literal(..) => Some(context.snippet(self.span)),
 837         }
 838     }
 839 }
 840
 841 impl Rewrite for ast::MetaItem {
 842     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 843         Some(match self.node {
 844             ast::MetaItemKind::Word => String::from(&*self.name.as_str()),
 845             ast::MetaItemKind::List(ref list) => {
 846                 let name = self.name.as_str();
 847                 // 3 = `#[` and `(`, 2 = `]` and `)`
 848                 let item_shape = try_opt!(
 849                     shape
 850                         .shrink_left(name.len() + 3)
 851                         .and_then(|s| s.sub_width(2))
 852                 );
 853                 let items = itemize_list(
 854                     context.codemap,
 855                     list.iter(),
 856                     ")",
 857                     |nested_meta_item| nested_meta_item.span.lo,
 858                     |nested_meta_item| nested_meta_item.span.hi,
 859                     |nested_meta_item| nested_meta_item.rewrite(context, item_shape),
 860                     self.span.lo,
 861                     self.span.hi,
 862                     false,
 863                 );
 864                 let item_vec = items.collect::<Vec<_>>();
 865                 let fmt = ListFormatting {
 866                     tactic: DefinitiveListTactic::Mixed,
 867                     separator: ",",
 868                     trailing_separator: SeparatorTactic::Never,
 869                     separator_place: SeparatorPlace::Back,
 870                     shape: item_shape,
 871                     ends_with_newline: false,
 872                     preserve_newline: false,
 873                     config: context.config,
 874                 };
 875                 format!("{}({})", name, try_opt!(write_list(&item_vec, &fmt)))
 876             }
 877             ast::MetaItemKind::NameValue(ref literal) => {
 878                 let name = self.name.as_str();
 879                 let value = context.snippet(literal.span);
 880                 if &*name == "doc" && contains_comment(&value) {
 881                     let doc_shape = Shape {
 882                         width: cmp::min(shape.width, context.config.comment_width())
 883                             .checked_sub(shape.indent.width())
 884                             .unwrap_or(0),
 885                         ..shape
 886                     };
 887                     format!(
 888                         "{}",
 889                         try_opt!(rewrite_comment(&value, false, doc_shape, context.config))
 890                     )
 891                 } else {
 892                     format!("{} = {}", name, value)
 893                 }
 894             }
 895         })
 896     }
 897 }
 898
 899 impl Rewrite for ast::Attribute {
 900     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 901         try_opt!(self.meta())
 902             .rewrite(context, shape)
 903             .map(|rw| if self.is_sugared_doc {
 904                 rw
 905             } else {
 906                 let original = context.snippet(self.span);
 907                 let prefix = match self.style {
 908                     ast::AttrStyle::Inner => "#!",
 909                     ast::AttrStyle::Outer => "#",
 910                 };
 911                 if contains_comment(&original) {
 912                     original
 913                 } else {
 914                     format!("{}[{}]", prefix, rw)
 915                 }
 916             })
 917     }
 918 }
 919
 920 impl<'a> Rewrite for [ast::Attribute] {
 921     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 922         let mut result = String::new();
 923         if self.is_empty() {
 924             return Some(result);
 925         }
 926         let indent = shape.indent.to_string(context.config);
 927
 928         let mut derive_args = Vec::new();
 929
 930         let mut iter = self.iter().enumerate().peekable();
 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 = a_str.starts_with("//") && comment.matches('\n').count() > 1;
 941                 let comment = comment.trim();
 942                 if !comment.is_empty() {
 943                     let comment = try_opt!(rewrite_comment(
 944                         comment,
 945                         false,
 946                         Shape::legacy(
 947                             context.config.comment_width() - shape.indent.width(),
 948                             shape.indent,
 949                         ),
 950                         context.config,
 951                     ));
 952                     result.push_str(&indent);
 953                     result.push_str(&comment);
 954                     result.push('\n');
 955                 } else if multi_line {
 956                     result.push('\n');
 957                 }
 958                 if derive_args.is_empty() {
 959                     result.push_str(&indent);
 960                 }
 961             }
 962
 963             // Write the attribute itself.
 964             let mut insert_new_line = true;
 965             if context.config.merge_derives() {
 966                 // If the attribute is `#[derive(...)]`, take the arguments.
 967                 if let Some(mut args) = get_derive_args(context, a) {
 968                     derive_args.append(&mut args);
 969                     match iter.peek() {
 970                         // If the next attribute is `#[derive(...)]` as well, skip rewriting.
 971                         Some(&(_, next_attr)) if is_derive(next_attr) => insert_new_line = false,
 972                         // If not, rewrite the merged derives.
 973                         _ => {
 974                             result.push_str(&format!("#[derive({})]", derive_args.join(", ")));
 975                             derive_args.clear();
 976                         }
 977                     }
 978                 } else {
 979                     result.push_str(&a_str);
 980                 }
 981             } else {
 982                 result.push_str(&a_str);
 983             }
 984
 985             if insert_new_line && i < self.len() - 1 {
 986                 result.push('\n');
 987             }
 988         }
 989         Some(result)
 990     }
 991 }
 992
 993 fn is_derive(attr: &ast::Attribute) -> bool {
 994     match attr.meta() {
 995         Some(meta_item) => match meta_item.node {
 996             ast::MetaItemKind::List(..) => meta_item.name.as_str() == "derive",
 997             _ => false,
 998         },
 999         _ => false,
1000     }
1001 }
1002
1003 /// Returns the arguments of `#[derive(...)]`.
1004 fn get_derive_args(context: &RewriteContext, attr: &ast::Attribute) -> Option<Vec<String>> {
1005     attr.meta().and_then(|meta_item| match meta_item.node {
1006         ast::MetaItemKind::List(ref args) if meta_item.name.as_str() == "derive" => {
1007             // Every argument of `derive` should be `NestedMetaItemKind::Literal`.
1008             Some(
1009                 args.iter()
1010                     .map(|a| context.snippet(a.span))
1011                     .collect::<Vec<_>>(),
1012             )
1013         }
1014         _ => None,
1015     })
1016 }