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 syntax::{ast, visit};
  14 use syntax::attr::HasAttrs;
  15 use syntax::codemap::{self, BytePos, CodeMap, Pos, Span};
  16 use syntax::parse::ParseSess;
  17
  18 use codemap::{LineRangeUtils, SpanUtils};
  19 use comment::{combine_strs_with_missing_comments, contains_comment, CodeCharKind,
  20               CommentCodeSlices, FindUncommented};
  21 use comment::rewrite_comment;
  22 use config::{BraceStyle, Config};
  23 use expr::rewrite_literal;
  24 use items::{format_impl, format_trait, format_trait_alias, rewrite_associated_impl_type,
  25             rewrite_associated_type, rewrite_type_alias, FnSig, StaticParts, StructParts};
  26 use lists::{itemize_list, write_list, DefinitiveListTactic, ListFormatting, SeparatorPlace,
  27             SeparatorTactic};
  28 use macros::{rewrite_macro, rewrite_macro_def, MacroPosition};
  29 use regex::Regex;
  30 use rewrite::{Rewrite, RewriteContext};
  31 use shape::{Indent, Shape};
  32 use spanned::Spanned;
  33 use utils::{self, contains_skip, count_newlines, inner_attributes, mk_sp, ptr_vec_to_ref_vec};
  34
  35 /// Returns attributes that are within `outer_span`.
  36 pub fn filter_inline_attrs(attrs: &[ast::Attribute], outer_span: Span) -> Vec<ast::Attribute> {
  37     attrs
  38         .iter()
  39         .filter(|a| outer_span.lo() <= a.span.lo() && a.span.hi() <= outer_span.hi())
  40         .cloned()
  41         .collect()
  42 }
  43
  44 /// Returns true for `mod foo;`, false for `mod foo { .. }`.
  45 fn is_mod_decl(item: &ast::Item) -> bool {
  46     match item.node {
  47         ast::ItemKind::Mod(ref m) => {
  48             !(m.inner.lo() == BytePos(0) && m.inner.hi() == BytePos(0))
  49                 && m.inner.hi() != item.span.hi()
  50         }
  51         _ => false,
  52     }
  53 }
  54
  55 /// Returns true for `mod foo;` without any inline attributes.
  56 /// We cannot reorder modules with attributes because doing so can break the code.
  57 /// e.g. `#[macro_use]`.
  58 fn is_mod_decl_without_attr(item: &ast::Item) -> bool {
  59     is_mod_decl(item) && filter_inline_attrs(&item.attrs, item.span()).is_empty()
  60 }
  61
  62 fn is_use_item(item: &ast::Item) -> bool {
  63     match item.node {
  64         ast::ItemKind::Use(_) => true,
  65         _ => false,
  66     }
  67 }
  68
  69 fn is_extern_crate(item: &ast::Item) -> bool {
  70     match item.node {
  71         ast::ItemKind::ExternCrate(..) => true,
  72         _ => false,
  73     }
  74 }
  75
  76 /// Creates a string slice corresponding to the specified span.
  77 pub struct SnippetProvider<'a> {
  78     /// A pointer to the content of the file we are formatting.
  79     big_snippet: &'a str,
  80     /// A position of the start of `big_snippet`, used as an offset.
  81     start_pos: usize,
  82 }
  83
  84 impl<'a> SnippetProvider<'a> {
  85     pub fn span_to_snippet(&self, span: Span) -> Option<&str> {
  86         let start_index = span.lo().to_usize().checked_sub(self.start_pos)?;
  87         let end_index = span.hi().to_usize().checked_sub(self.start_pos)?;
  88         Some(&self.big_snippet[start_index..end_index])
  89     }
  90
  91     pub fn new(start_pos: BytePos, big_snippet: &'a str) -> Self {
  92         let start_pos = start_pos.to_usize();
  93         SnippetProvider {
  94             big_snippet,
  95             start_pos,
  96         }
  97     }
  98 }
  99
 100 pub struct FmtVisitor<'a> {
 101     pub parse_session: &'a ParseSess,
 102     pub codemap: &'a CodeMap,
 103     pub buffer: String,
 104     pub last_pos: BytePos,
 105     // FIXME: use an RAII util or closure for indenting
 106     pub block_indent: Indent,
 107     pub config: &'a Config,
 108     pub is_if_else_block: bool,
 109     pub snippet_provider: &'a SnippetProvider<'a>,
 110     pub line_number: usize,
 111     pub skipped_range: Vec<(usize, usize)>,
 112 }
 113
 114 impl<'b, 'a: 'b> FmtVisitor<'a> {
 115     pub fn shape(&self) -> Shape {
 116         Shape::indented(self.block_indent, self.config)
 117     }
 118
 119     fn visit_stmt(&mut self, stmt: &ast::Stmt) {
 120         debug!(
 121             "visit_stmt: {:?} {:?}",
 122             self.codemap.lookup_char_pos(stmt.span.lo()),
 123             self.codemap.lookup_char_pos(stmt.span.hi())
 124         );
 125
 126         match stmt.node {
 127             ast::StmtKind::Item(ref item) => {
 128                 self.visit_item(item);
 129             }
 130             ast::StmtKind::Local(..) | ast::StmtKind::Expr(..) | ast::StmtKind::Semi(..) => {
 131                 if contains_skip(get_attrs_from_stmt(stmt)) {
 132                     self.push_skipped_with_span(stmt.span());
 133                 } else {
 134                     let rewrite = stmt.rewrite(&self.get_context(), self.shape());
 135                     self.push_rewrite(stmt.span(), rewrite)
 136                 }
 137             }
 138             ast::StmtKind::Mac(ref mac) => {
 139                 let (ref mac, _macro_style, ref attrs) = **mac;
 140                 if self.visit_attrs(attrs, ast::AttrStyle::Outer) {
 141                     self.push_skipped_with_span(stmt.span());
 142                 } else {
 143                     self.visit_mac(mac, None, MacroPosition::Statement);
 144                 }
 145                 self.format_missing(stmt.span.hi());
 146             }
 147         }
 148     }
 149
 150     pub fn visit_block(
 151         &mut self,
 152         b: &ast::Block,
 153         inner_attrs: Option<&[ast::Attribute]>,
 154         has_braces: bool,
 155     ) {
 156         debug!(
 157             "visit_block: {:?} {:?}",
 158             self.codemap.lookup_char_pos(b.span.lo()),
 159             self.codemap.lookup_char_pos(b.span.hi())
 160         );
 161
 162         // Check if this block has braces.
 163         let brace_compensation = BytePos(if has_braces { 1 } else { 0 });
 164
 165         self.last_pos = self.last_pos + brace_compensation;
 166         self.block_indent = self.block_indent.block_indent(self.config);
 167         self.push_str("{");
 168
 169         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 170             if let Some(first_stmt) = b.stmts.first() {
 171                 let attr_lo = inner_attrs
 172                     .and_then(|attrs| inner_attributes(attrs).first().map(|attr| attr.span.lo()))
 173                     .or_else(|| {
 174                         // Attributes for an item in a statement position
 175                         // do not belong to the statement. (rust-lang/rust#34459)
 176                         if let ast::StmtKind::Item(ref item) = first_stmt.node {
 177                             item.attrs.first()
 178                         } else {
 179                             first_stmt.attrs().first()
 180                         }.and_then(|attr| {
 181                             // Some stmts can have embedded attributes.
 182                             // e.g. `match { #![attr] ... }`
 183                             let attr_lo = attr.span.lo();
 184                             if attr_lo < first_stmt.span.lo() {
 185                                 Some(attr_lo)
 186                             } else {
 187                                 None
 188                             }
 189                         })
 190                     });
 191
 192                 let snippet = self.snippet(mk_sp(
 193                     self.last_pos,
 194                     attr_lo.unwrap_or(first_stmt.span.lo()),
 195                 ));
 196                 let len = CommentCodeSlices::new(snippet)
 197                     .nth(0)
 198                     .and_then(|(kind, _, s)| {
 199                         if kind == CodeCharKind::Normal {
 200                             s.rfind('\n')
 201                         } else {
 202                             None
 203                         }
 204                     });
 205                 if let Some(len) = len {
 206                     self.last_pos = self.last_pos + BytePos::from_usize(len);
 207                 }
 208             }
 209         }
 210
 211         // Format inner attributes if available.
 212         let skip_rewrite = if let Some(attrs) = inner_attrs {
 213             self.visit_attrs(attrs, ast::AttrStyle::Inner)
 214         } else {
 215             false
 216         };
 217
 218         if skip_rewrite {
 219             self.push_rewrite(b.span, None);
 220             self.close_block(false);
 221             self.last_pos = source!(self, b.span).hi();
 222             return;
 223         }
 224
 225         self.walk_block_stmts(b);
 226
 227         if !b.stmts.is_empty() {
 228             if let Some(expr) = utils::stmt_expr(&b.stmts[b.stmts.len() - 1]) {
 229                 if utils::semicolon_for_expr(&self.get_context(), expr) {
 230                     self.push_str(";");
 231                 }
 232             }
 233         }
 234
 235         let mut remove_len = BytePos(0);
 236         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 237             if let Some(stmt) = b.stmts.last() {
 238                 let snippet = self.snippet(mk_sp(
 239                     stmt.span.hi(),
 240                     source!(self, b.span).hi() - brace_compensation,
 241                 ));
 242                 let len = CommentCodeSlices::new(snippet)
 243                     .last()
 244                     .and_then(|(kind, _, s)| {
 245                         if kind == CodeCharKind::Normal && s.trim().is_empty() {
 246                             Some(s.len())
 247                         } else {
 248                             None
 249                         }
 250                     });
 251                 if let Some(len) = len {
 252                     remove_len = BytePos::from_usize(len);
 253                 }
 254             }
 255         }
 256
 257         let unindent_comment = (self.is_if_else_block && !b.stmts.is_empty()) && {
 258             let end_pos = source!(self, b.span).hi() - brace_compensation - remove_len;
 259             let snippet = self.snippet(mk_sp(self.last_pos, end_pos));
 260             snippet.contains("//") || snippet.contains("/*")
 261         };
 262         // FIXME: we should compress any newlines here to just one
 263         if unindent_comment {
 264             self.block_indent = self.block_indent.block_unindent(self.config);
 265         }
 266         self.format_missing_with_indent(
 267             source!(self, b.span).hi() - brace_compensation - remove_len,
 268         );
 269         if unindent_comment {
 270             self.block_indent = self.block_indent.block_indent(self.config);
 271         }
 272         self.close_block(unindent_comment);
 273         self.last_pos = source!(self, b.span).hi();
 274     }
 275
 276     // FIXME: this is a terrible hack to indent the comments between the last
 277     // item in the block and the closing brace to the block's level.
 278     // The closing brace itself, however, should be indented at a shallower
 279     // level.
 280     fn close_block(&mut self, unindent_comment: bool) {
 281         let total_len = self.buffer.len();
 282         let chars_too_many = if unindent_comment {
 283             0
 284         } else if self.config.hard_tabs() {
 285             1
 286         } else {
 287             self.config.tab_spaces()
 288         };
 289         self.buffer.truncate(total_len - chars_too_many);
 290         self.push_str("}");
 291         self.block_indent = self.block_indent.block_unindent(self.config);
 292     }
 293
 294     // Note that this only gets called for function definitions. Required methods
 295     // on traits do not get handled here.
 296     fn visit_fn(
 297         &mut self,
 298         fk: visit::FnKind,
 299         generics: &ast::Generics,
 300         fd: &ast::FnDecl,
 301         s: Span,
 302         defaultness: ast::Defaultness,
 303         inner_attrs: Option<&[ast::Attribute]>,
 304     ) {
 305         let indent = self.block_indent;
 306         let block;
 307         let rewrite = match fk {
 308             visit::FnKind::ItemFn(ident, _, _, _, _, b) | visit::FnKind::Method(ident, _, _, b) => {
 309                 block = b;
 310                 self.rewrite_fn(
 311                     indent,
 312                     ident,
 313                     &FnSig::from_fn_kind(&fk, generics, fd, defaultness),
 314                     mk_sp(s.lo(), b.span.lo()),
 315                     b,
 316                 )
 317             }
 318             visit::FnKind::Closure(_) => unreachable!(),
 319         };
 320
 321         if let Some(fn_str) = rewrite {
 322             self.format_missing_with_indent(source!(self, s).lo());
 323             self.push_str(&fn_str);
 324             if let Some(c) = fn_str.chars().last() {
 325                 if c == '}' {
 326                     self.last_pos = source!(self, block.span).hi();
 327                     return;
 328                 }
 329             }
 330         } else {
 331             self.format_missing(source!(self, block.span).lo());
 332         }
 333
 334         self.last_pos = source!(self, block.span).lo();
 335         self.visit_block(block, inner_attrs, true)
 336     }
 337
 338     pub fn visit_item(&mut self, item: &ast::Item) {
 339         skip_out_of_file_lines_range_visitor!(self, item.span);
 340
 341         // This is where we bail out if there is a skip attribute. This is only
 342         // complex in the module case. It is complex because the module could be
 343         // in a separate file and there might be attributes in both files, but
 344         // the AST lumps them all together.
 345         let filtered_attrs;
 346         let mut attrs = &item.attrs;
 347         match item.node {
 348             // Module is inline, in this case we treat it like any other item.
 349             _ if !is_mod_decl(item) => {
 350                 if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 351                     self.push_skipped_with_span(item.span());
 352                     return;
 353                 }
 354             }
 355             // Module is not inline, but should be skipped.
 356             ast::ItemKind::Mod(..) if contains_skip(&item.attrs) => {
 357                 return;
 358             }
 359             // Module is not inline and should not be skipped. We want
 360             // to process only the attributes in the current file.
 361             ast::ItemKind::Mod(..) => {
 362                 filtered_attrs = filter_inline_attrs(&item.attrs, item.span());
 363                 // Assert because if we should skip it should be caught by
 364                 // the above case.
 365                 assert!(!self.visit_attrs(&filtered_attrs, ast::AttrStyle::Outer));
 366                 attrs = &filtered_attrs;
 367             }
 368             _ => {
 369                 if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 370                     self.push_skipped_with_span(item.span());
 371                     return;
 372                 }
 373             }
 374         }
 375
 376         match item.node {
 377             ast::ItemKind::Use(ref tree) => self.format_import(item, tree),
 378             ast::ItemKind::Impl(..) => {
 379                 let snippet = self.snippet(item.span);
 380                 let where_span_end = snippet
 381                     .find_uncommented("{")
 382                     .map(|x| (BytePos(x as u32)) + source!(self, item.span).lo());
 383                 let rw = format_impl(&self.get_context(), item, self.block_indent, where_span_end);
 384                 self.push_rewrite(item.span, rw);
 385             }
 386             ast::ItemKind::Trait(..) => {
 387                 let rw = format_trait(&self.get_context(), item, self.block_indent);
 388                 self.push_rewrite(item.span, rw);
 389             }
 390             ast::ItemKind::TraitAlias(ref generics, ref ty_param_bounds) => {
 391                 let shape = Shape::indented(self.block_indent, self.config);
 392                 let rw = format_trait_alias(
 393                     &self.get_context(),
 394                     item.ident,
 395                     generics,
 396                     ty_param_bounds,
 397                     shape,
 398                 );
 399                 self.push_rewrite(item.span, rw);
 400             }
 401             ast::ItemKind::ExternCrate(_) => {
 402                 let rw = rewrite_extern_crate(&self.get_context(), item);
 403                 self.push_rewrite(item.span, rw);
 404             }
 405             ast::ItemKind::Struct(..) | ast::ItemKind::Union(..) => {
 406                 self.visit_struct(&StructParts::from_item(item));
 407             }
 408             ast::ItemKind::Enum(ref def, ref generics) => {
 409                 self.format_missing_with_indent(source!(self, item.span).lo());
 410                 self.visit_enum(item.ident, &item.vis, def, generics, item.span);
 411                 self.last_pos = source!(self, item.span).hi();
 412             }
 413             ast::ItemKind::Mod(ref module) => {
 414                 let is_inline = !is_mod_decl(item);
 415                 self.format_missing_with_indent(source!(self, item.span).lo());
 416                 self.format_mod(module, &item.vis, item.span, item.ident, attrs, is_inline);
 417             }
 418             ast::ItemKind::Mac(ref mac) => {
 419                 self.visit_mac(mac, Some(item.ident), MacroPosition::Item);
 420             }
 421             ast::ItemKind::ForeignMod(ref foreign_mod) => {
 422                 self.format_missing_with_indent(source!(self, item.span).lo());
 423                 self.format_foreign_mod(foreign_mod, item.span);
 424             }
 425             ast::ItemKind::Static(..) | ast::ItemKind::Const(..) => {
 426                 self.visit_static(&StaticParts::from_item(item));
 427             }
 428             ast::ItemKind::Fn(ref decl, unsafety, constness, abi, ref generics, ref body) => {
 429                 self.visit_fn(
 430                     visit::FnKind::ItemFn(item.ident, unsafety, constness, abi, &item.vis, body),
 431                     generics,
 432                     decl,
 433                     item.span,
 434                     ast::Defaultness::Final,
 435                     Some(&item.attrs),
 436                 )
 437             }
 438             ast::ItemKind::Ty(ref ty, ref generics) => {
 439                 let rewrite = rewrite_type_alias(
 440                     &self.get_context(),
 441                     self.block_indent,
 442                     item.ident,
 443                     ty,
 444                     generics,
 445                     &item.vis,
 446                     item.span,
 447                 );
 448                 self.push_rewrite(item.span, rewrite);
 449             }
 450             ast::ItemKind::GlobalAsm(..) => {
 451                 let snippet = Some(self.snippet(item.span).to_owned());
 452                 self.push_rewrite(item.span, snippet);
 453             }
 454             ast::ItemKind::MacroDef(ref def) => {
 455                 let rewrite = rewrite_macro_def(
 456                     &self.get_context(),
 457                     self.block_indent,
 458                     def,
 459                     item.ident,
 460                     &item.vis,
 461                     item.span,
 462                 );
 463                 self.push_rewrite(item.span, rewrite);
 464             }
 465         }
 466     }
 467
 468     pub fn visit_trait_item(&mut self, ti: &ast::TraitItem) {
 469         skip_out_of_file_lines_range_visitor!(self, ti.span);
 470
 471         if self.visit_attrs(&ti.attrs, ast::AttrStyle::Outer) {
 472             self.push_skipped_with_span(ti.span());
 473             return;
 474         }
 475
 476         match ti.node {
 477             ast::TraitItemKind::Const(..) => self.visit_static(&StaticParts::from_trait_item(ti)),
 478             ast::TraitItemKind::Method(ref sig, None) => {
 479                 let indent = self.block_indent;
 480                 let rewrite =
 481                     self.rewrite_required_fn(indent, ti.ident, sig, &ti.generics, ti.span);
 482                 self.push_rewrite(ti.span, rewrite);
 483             }
 484             ast::TraitItemKind::Method(ref sig, Some(ref body)) => {
 485                 self.visit_fn(
 486                     visit::FnKind::Method(ti.ident, sig, None, body),
 487                     &ti.generics,
 488                     &sig.decl,
 489                     ti.span,
 490                     ast::Defaultness::Final,
 491                     Some(&ti.attrs),
 492                 );
 493             }
 494             ast::TraitItemKind::Type(ref type_param_bounds, ref type_default) => {
 495                 let rewrite = rewrite_associated_type(
 496                     ti.ident,
 497                     type_default.as_ref(),
 498                     Some(type_param_bounds),
 499                     &self.get_context(),
 500                     self.block_indent,
 501                 );
 502                 self.push_rewrite(ti.span, rewrite);
 503             }
 504             ast::TraitItemKind::Macro(ref mac) => {
 505                 self.visit_mac(mac, Some(ti.ident), MacroPosition::Item);
 506             }
 507         }
 508     }
 509
 510     pub fn visit_impl_item(&mut self, ii: &ast::ImplItem) {
 511         skip_out_of_file_lines_range_visitor!(self, ii.span);
 512
 513         if self.visit_attrs(&ii.attrs, ast::AttrStyle::Outer) {
 514             self.push_skipped_with_span(ii.span());
 515             return;
 516         }
 517
 518         match ii.node {
 519             ast::ImplItemKind::Method(ref sig, ref body) => {
 520                 self.visit_fn(
 521                     visit::FnKind::Method(ii.ident, sig, Some(&ii.vis), body),
 522                     &ii.generics,
 523                     &sig.decl,
 524                     ii.span,
 525                     ii.defaultness,
 526                     Some(&ii.attrs),
 527                 );
 528             }
 529             ast::ImplItemKind::Const(..) => self.visit_static(&StaticParts::from_impl_item(ii)),
 530             ast::ImplItemKind::Type(ref ty) => {
 531                 let rewrite = rewrite_associated_impl_type(
 532                     ii.ident,
 533                     ii.defaultness,
 534                     Some(ty),
 535                     None,
 536                     &self.get_context(),
 537                     self.block_indent,
 538                 );
 539                 self.push_rewrite(ii.span, rewrite);
 540             }
 541             ast::ImplItemKind::Macro(ref mac) => {
 542                 self.visit_mac(mac, Some(ii.ident), MacroPosition::Item);
 543             }
 544         }
 545     }
 546
 547     fn visit_mac(&mut self, mac: &ast::Mac, ident: Option<ast::Ident>, pos: MacroPosition) {
 548         skip_out_of_file_lines_range_visitor!(self, mac.span);
 549
 550         // 1 = ;
 551         let shape = self.shape().sub_width(1).unwrap();
 552         let rewrite = rewrite_macro(mac, ident, &self.get_context(), shape, pos);
 553         self.push_rewrite(mac.span, rewrite);
 554     }
 555
 556     pub fn push_str(&mut self, s: &str) {
 557         self.line_number += count_newlines(s);
 558         self.buffer.push_str(s);
 559     }
 560
 561     fn push_rewrite_inner(&mut self, span: Span, rewrite: Option<String>) {
 562         if let Some(ref s) = rewrite {
 563             self.push_str(s);
 564         } else {
 565             let snippet = self.snippet(span);
 566             self.push_str(snippet);
 567         }
 568         self.last_pos = source!(self, span).hi();
 569     }
 570
 571     pub fn push_rewrite(&mut self, span: Span, rewrite: Option<String>) {
 572         self.format_missing_with_indent(source!(self, span).lo());
 573         self.push_rewrite_inner(span, rewrite);
 574     }
 575
 576     pub fn push_skipped_with_span(&mut self, span: Span) {
 577         self.format_missing_with_indent(source!(self, span).lo());
 578         let lo = self.line_number + 1;
 579         self.push_rewrite_inner(span, None);
 580         let hi = self.line_number + 1;
 581         self.skipped_range.push((lo, hi));
 582     }
 583
 584     pub fn from_context(ctx: &'a RewriteContext) -> FmtVisitor<'a> {
 585         FmtVisitor::from_codemap(ctx.parse_session, ctx.config, ctx.snippet_provider)
 586     }
 587
 588     pub fn from_codemap(
 589         parse_session: &'a ParseSess,
 590         config: &'a Config,
 591         snippet_provider: &'a SnippetProvider,
 592     ) -> FmtVisitor<'a> {
 593         FmtVisitor {
 594             parse_session: parse_session,
 595             codemap: parse_session.codemap(),
 596             buffer: String::with_capacity(snippet_provider.big_snippet.len() * 2),
 597             last_pos: BytePos(0),
 598             block_indent: Indent::empty(),
 599             config: config,
 600             is_if_else_block: false,
 601             snippet_provider: snippet_provider,
 602             line_number: 0,
 603             skipped_range: vec![],
 604         }
 605     }
 606
 607     pub fn opt_snippet(&'b self, span: Span) -> Option<&'a str> {
 608         self.snippet_provider.span_to_snippet(span)
 609     }
 610
 611     pub fn snippet(&'b self, span: Span) -> &'a str {
 612         self.opt_snippet(span).unwrap()
 613     }
 614
 615     // Returns true if we should skip the following item.
 616     pub fn visit_attrs(&mut self, attrs: &[ast::Attribute], style: ast::AttrStyle) -> bool {
 617         if contains_skip(attrs) {
 618             return true;
 619         }
 620
 621         let attrs: Vec<_> = attrs.iter().filter(|a| a.style == style).cloned().collect();
 622         if attrs.is_empty() {
 623             return false;
 624         }
 625
 626         let rewrite = attrs.rewrite(&self.get_context(), self.shape());
 627         let span = mk_sp(attrs[0].span.lo(), attrs[attrs.len() - 1].span.hi());
 628         self.push_rewrite(span, rewrite);
 629
 630         false
 631     }
 632
 633     fn reorder_items<F>(&mut self, items_left: &[&ast::Item], is_item: &F, in_group: bool) -> usize
 634     where
 635         F: Fn(&ast::Item) -> bool,
 636     {
 637         let mut last = self.codemap.lookup_line_range(items_left[0].span());
 638         let item_length = items_left
 639             .iter()
 640             .take_while(|ppi| {
 641                 is_item(&***ppi) && (!in_group || {
 642                     let current = self.codemap.lookup_line_range(ppi.span());
 643                     let in_same_group = current.lo < last.hi + 2;
 644                     last = current;
 645                     in_same_group
 646                 })
 647             })
 648             .count();
 649         let items = &items_left[..item_length];
 650
 651         let at_least_one_in_file_lines = items
 652             .iter()
 653             .any(|item| !out_of_file_lines_range!(self, item.span));
 654
 655         if at_least_one_in_file_lines {
 656             self.format_imports(items);
 657         } else {
 658             for item in items {
 659                 self.push_rewrite(item.span, None);
 660             }
 661         }
 662
 663         item_length
 664     }
 665
 666     fn walk_items(&mut self, mut items_left: &[&ast::Item]) {
 667         macro try_reorder_items_with($reorder: ident, $in_group: ident, $pred: ident) {
 668             if self.config.$reorder() && $pred(&*items_left[0]) {
 669                 let used_items_len =
 670                     self.reorder_items(items_left, &$pred, self.config.$in_group());
 671                 let (_, rest) = items_left.split_at(used_items_len);
 672                 items_left = rest;
 673                 continue;
 674             }
 675         }
 676
 677         while !items_left.is_empty() {
 678             // If the next item is a `use`, `extern crate` or `mod`, then extract it and any
 679             // subsequent items that have the same item kind to be reordered within
 680             // `format_imports`. Otherwise, just format the next item for output.
 681             {
 682                 try_reorder_items_with!(reorder_imports, reorder_imports_in_group, is_use_item);
 683                 try_reorder_items_with!(
 684                     reorder_extern_crates,
 685                     reorder_extern_crates_in_group,
 686                     is_extern_crate
 687                 );
 688                 try_reorder_items_with!(reorder_modules, reorder_modules, is_mod_decl_without_attr);
 689             }
 690             // Reaching here means items were not reordered. There must be at least
 691             // one item left in `items_left`, so calling `unwrap()` here is safe.
 692             let (item, rest) = items_left.split_first().unwrap();
 693             self.visit_item(item);
 694             items_left = rest;
 695         }
 696     }
 697
 698     fn walk_mod_items(&mut self, m: &ast::Mod) {
 699         self.walk_items(&ptr_vec_to_ref_vec(&m.items));
 700     }
 701
 702     fn walk_stmts(&mut self, stmts: &[ast::Stmt]) {
 703         fn to_stmt_item(stmt: &ast::Stmt) -> Option<&ast::Item> {
 704             match stmt.node {
 705                 ast::StmtKind::Item(ref item) => Some(&**item),
 706                 _ => None,
 707             }
 708         }
 709
 710         if stmts.is_empty() {
 711             return;
 712         }
 713
 714         // Extract leading `use ...;`.
 715         let items: Vec<_> = stmts
 716             .iter()
 717             .take_while(|stmt| to_stmt_item(stmt).map_or(false, is_use_item))
 718             .filter_map(|stmt| to_stmt_item(stmt))
 719             .collect();
 720
 721         if items.is_empty() {
 722             self.visit_stmt(&stmts[0]);
 723             self.walk_stmts(&stmts[1..]);
 724         } else {
 725             self.walk_items(&items);
 726             self.walk_stmts(&stmts[items.len()..]);
 727         }
 728     }
 729
 730     fn walk_block_stmts(&mut self, b: &ast::Block) {
 731         self.walk_stmts(&b.stmts)
 732     }
 733
 734     fn format_mod(
 735         &mut self,
 736         m: &ast::Mod,
 737         vis: &ast::Visibility,
 738         s: Span,
 739         ident: ast::Ident,
 740         attrs: &[ast::Attribute],
 741         is_internal: bool,
 742     ) {
 743         self.push_str(&*utils::format_visibility(vis));
 744         self.push_str("mod ");
 745         self.push_str(&ident.to_string());
 746
 747         if is_internal {
 748             match self.config.brace_style() {
 749                 BraceStyle::AlwaysNextLine => {
 750                     let sep_str = format!("\n{}{{", self.block_indent.to_string(self.config));
 751                     self.push_str(&sep_str);
 752                 }
 753                 _ => self.push_str(" {"),
 754             }
 755             // Hackery to account for the closing }.
 756             let mod_lo = self.codemap.span_after(source!(self, s), "{");
 757             let body_snippet =
 758                 self.snippet(mk_sp(mod_lo, source!(self, m.inner).hi() - BytePos(1)));
 759             let body_snippet = body_snippet.trim();
 760             if body_snippet.is_empty() {
 761                 self.push_str("}");
 762             } else {
 763                 self.last_pos = mod_lo;
 764                 self.block_indent = self.block_indent.block_indent(self.config);
 765                 self.visit_attrs(attrs, ast::AttrStyle::Inner);
 766                 self.walk_mod_items(m);
 767                 self.format_missing_with_indent(source!(self, m.inner).hi() - BytePos(1));
 768                 self.close_block(false);
 769             }
 770             self.last_pos = source!(self, m.inner).hi();
 771         } else {
 772             self.push_str(";");
 773             self.last_pos = source!(self, s).hi();
 774         }
 775     }
 776
 777     pub fn format_separate_mod(&mut self, m: &ast::Mod, filemap: &codemap::FileMap) {
 778         self.block_indent = Indent::empty();
 779         self.walk_mod_items(m);
 780         self.format_missing_with_indent(filemap.end_pos);
 781     }
 782
 783     pub fn skip_empty_lines(&mut self, end_pos: BytePos) {
 784         while let Some(pos) = self.codemap
 785             .opt_span_after(mk_sp(self.last_pos, end_pos), "\n")
 786         {
 787             if let Some(snippet) = self.opt_snippet(mk_sp(self.last_pos, pos)) {
 788                 if snippet.trim().is_empty() {
 789                     self.last_pos = pos;
 790                 } else {
 791                     return;
 792                 }
 793             }
 794         }
 795     }
 796
 797     pub fn get_context(&self) -> RewriteContext {
 798         RewriteContext {
 799             parse_session: self.parse_session,
 800             codemap: self.codemap,
 801             config: self.config,
 802             inside_macro: false,
 803             use_block: false,
 804             is_if_else_block: false,
 805             force_one_line_chain: false,
 806             snippet_provider: self.snippet_provider,
 807         }
 808     }
 809 }
 810
 811 impl Rewrite for ast::NestedMetaItem {
 812     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 813         match self.node {
 814             ast::NestedMetaItemKind::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
 815             ast::NestedMetaItemKind::Literal(ref l) => rewrite_literal(context, l, shape),
 816         }
 817     }
 818 }
 819
 820 impl Rewrite for ast::MetaItem {
 821     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 822         Some(match self.node {
 823             ast::MetaItemKind::Word => String::from(&*self.name.as_str()),
 824             ast::MetaItemKind::List(ref list) => {
 825                 let name = self.name.as_str();
 826                 // 1 = `(`, 2 = `]` and `)`
 827                 let item_shape = shape
 828                     .visual_indent(0)
 829                     .shrink_left(name.len() + 1)
 830                     .and_then(|s| s.sub_width(2))?;
 831                 let items = itemize_list(
 832                     context.codemap,
 833                     list.iter(),
 834                     ")",
 835                     ",",
 836                     |nested_meta_item| nested_meta_item.span.lo(),
 837                     |nested_meta_item| nested_meta_item.span.hi(),
 838                     |nested_meta_item| nested_meta_item.rewrite(context, item_shape),
 839                     self.span.lo(),
 840                     self.span.hi(),
 841                     false,
 842                 );
 843                 let item_vec = items.collect::<Vec<_>>();
 844                 let fmt = ListFormatting {
 845                     tactic: DefinitiveListTactic::Mixed,
 846                     separator: ",",
 847                     trailing_separator: SeparatorTactic::Never,
 848                     separator_place: SeparatorPlace::Back,
 849                     shape: item_shape,
 850                     ends_with_newline: false,
 851                     preserve_newline: false,
 852                     config: context.config,
 853                 };
 854                 format!("{}({})", name, write_list(&item_vec, &fmt)?)
 855             }
 856             ast::MetaItemKind::NameValue(ref literal) => {
 857                 let name = self.name.as_str();
 858                 // 3 = ` = `
 859                 let lit_shape = shape.shrink_left(name.len() + 3)?;
 860                 let value = rewrite_literal(context, literal, lit_shape)?;
 861                 format!("{} = {}", name, value)
 862             }
 863         })
 864     }
 865 }
 866
 867 impl Rewrite for ast::Attribute {
 868     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 869         let prefix = match self.style {
 870             ast::AttrStyle::Inner => "#!",
 871             ast::AttrStyle::Outer => "#",
 872         };
 873         let snippet = context.snippet(self.span);
 874         if self.is_sugared_doc {
 875             let doc_shape = Shape {
 876                 width: cmp::min(shape.width, context.config.comment_width())
 877                     .checked_sub(shape.indent.width())
 878                     .unwrap_or(0),
 879                 ..shape
 880             };
 881             rewrite_comment(snippet, false, doc_shape, context.config)
 882         } else {
 883             if contains_comment(snippet) {
 884                 return Some(snippet.to_owned());
 885             }
 886             // 1 = `[`
 887             let shape = shape.offset_left(prefix.len() + 1)?;
 888             self.meta()?
 889                 .rewrite(context, shape)
 890                 .map(|rw| format!("{}[{}]", prefix, rw))
 891         }
 892     }
 893 }
 894
 895 /// Returns the first group of attributes that fills the given predicate.
 896 /// We consider two doc comments are in different group if they are separated by normal comments.
 897 fn take_while_with_pred<'a, P>(
 898     context: &RewriteContext,
 899     attrs: &'a [ast::Attribute],
 900     pred: P,
 901 ) -> &'a [ast::Attribute]
 902 where
 903     P: Fn(&ast::Attribute) -> bool,
 904 {
 905     let mut last_index = 0;
 906     let mut iter = attrs.iter().enumerate().peekable();
 907     while let Some((i, attr)) = iter.next() {
 908         if !pred(attr) {
 909             break;
 910         }
 911         if let Some(&(_, next_attr)) = iter.peek() {
 912             // Extract comments between two attributes.
 913             let span_between_attr = mk_sp(attr.span.hi(), next_attr.span.lo());
 914             let snippet = context.snippet(span_between_attr);
 915             if count_newlines(snippet) >= 2 || snippet.contains('/') {
 916                 break;
 917             }
 918         }
 919         last_index = i;
 920     }
 921     if last_index == 0 {
 922         &[]
 923     } else {
 924         &attrs[..last_index + 1]
 925     }
 926 }
 927
 928 fn rewrite_first_group_attrs(
 929     context: &RewriteContext,
 930     attrs: &[ast::Attribute],
 931     shape: Shape,
 932 ) -> Option<(usize, String)> {
 933     if attrs.is_empty() {
 934         return Some((0, String::new()));
 935     }
 936     // Rewrite doc comments
 937     let sugared_docs = take_while_with_pred(context, attrs, |a| a.is_sugared_doc);
 938     if !sugared_docs.is_empty() {
 939         let snippet = sugared_docs
 940             .iter()
 941             .map(|a| context.snippet(a.span))
 942             .collect::<Vec<_>>()
 943             .join("\n");
 944         return Some((
 945             sugared_docs.len(),
 946             rewrite_comment(&snippet, false, shape, context.config)?,
 947         ));
 948     }
 949     // Rewrite `#[derive(..)]`s.
 950     if context.config.merge_derives() {
 951         let derives = take_while_with_pred(context, attrs, is_derive);
 952         if !derives.is_empty() {
 953             let mut derive_args = vec![];
 954             for derive in derives {
 955                 derive_args.append(&mut get_derive_args(context, derive)?);
 956             }
 957             return Some((derives.len(), format_derive(context, &derive_args, shape)?));
 958         }
 959     }
 960     // Rewrite the first attribute.
 961     Some((1, attrs[0].rewrite(context, shape)?))
 962 }
 963
 964 fn has_newlines_before_after_comment(comment: &str) -> (&str, &str) {
 965     // Look at before and after comment and see if there are any empty lines.
 966     let comment_begin = comment.chars().position(|c| c == '/');
 967     let len = comment_begin.unwrap_or_else(|| comment.len());
 968     let mlb = count_newlines(&comment[..len]) > 1;
 969     let mla = if comment_begin.is_none() {
 970         mlb
 971     } else {
 972         let comment_end = comment.chars().rev().position(|c| !c.is_whitespace());
 973         let len = comment_end.unwrap();
 974         comment
 975             .chars()
 976             .rev()
 977             .take(len)
 978             .filter(|c| *c == '\n')
 979             .count() > 1
 980     };
 981     (if mlb { "\n" } else { "" }, if mla { "\n" } else { "" })
 982 }
 983
 984 impl<'a> Rewrite for [ast::Attribute] {
 985     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 986         if self.is_empty() {
 987             return Some(String::new());
 988         }
 989         let (first_group_len, first_group_str) = rewrite_first_group_attrs(context, self, shape)?;
 990         if self.len() == 1 || first_group_len == self.len() {
 991             Some(first_group_str)
 992         } else {
 993             let rest_str = self[first_group_len..].rewrite(context, shape)?;
 994             let missing_span = mk_sp(
 995                 self[first_group_len - 1].span.hi(),
 996                 self[first_group_len].span.lo(),
 997             );
 998             // Preserve an empty line before/after doc comments.
 999             if self[0].is_sugared_doc || self[first_group_len].is_sugared_doc {
1000                 let snippet = context.snippet(missing_span);
1001                 let (mla, mlb) = has_newlines_before_after_comment(snippet);
1002                 let comment = ::comment::recover_missing_comment_in_span(
1003                     missing_span,
1004                     shape.with_max_width(context.config),
1005                     context,
1006                     0,
1007                 )?;
1008                 let comment = if comment.is_empty() {
1009                     format!("\n{}", mlb)
1010                 } else {
1011                     format!("{}{}\n{}", mla, comment, mlb)
1012                 };
1013                 Some(format!(
1014                     "{}{}{}{}",
1015                     first_group_str,
1016                     comment,
1017                     shape.indent.to_string(context.config),
1018                     rest_str
1019                 ))
1020             } else {
1021                 combine_strs_with_missing_comments(
1022                     context,
1023                     &first_group_str,
1024                     &rest_str,
1025                     missing_span,
1026                     shape,
1027                     false,
1028                 )
1029             }
1030         }
1031     }
1032 }
1033
1034 // Format `#[derive(..)]`, using visual indent & mixed style when we need to go multiline.
1035 fn format_derive(context: &RewriteContext, derive_args: &[&str], shape: Shape) -> Option<String> {
1036     let mut result = String::with_capacity(128);
1037     result.push_str("#[derive(");
1038     // 11 = `#[derive()]`
1039     let initial_budget = shape.width.checked_sub(11)?;
1040     let mut budget = initial_budget;
1041     let num = derive_args.len();
1042     for (i, a) in derive_args.iter().enumerate() {
1043         // 2 = `, ` or `)]`
1044         let width = a.len() + 2;
1045         if width > budget {
1046             if i > 0 {
1047                 // Remove trailing whitespace.
1048                 result.pop();
1049             }
1050             result.push('\n');
1051             // 9 = `#[derive(`
1052             result.push_str(&(shape.indent + 9).to_string(context.config));
1053             budget = initial_budget;
1054         } else {
1055             budget = budget.checked_sub(width).unwrap_or(0);
1056         }
1057         result.push_str(a);
1058         if i != num - 1 {
1059             result.push_str(", ")
1060         }
1061     }
1062     result.push_str(")]");
1063     Some(result)
1064 }
1065
1066 fn is_derive(attr: &ast::Attribute) -> bool {
1067     attr.check_name("derive")
1068 }
1069
1070 /// Returns the arguments of `#[derive(...)]`.
1071 fn get_derive_args<'a>(context: &'a RewriteContext, attr: &ast::Attribute) -> Option<Vec<&'a str>> {
1072     attr.meta_item_list().map(|meta_item_list| {
1073         meta_item_list
1074             .iter()
1075             .map(|nested_meta_item| context.snippet(nested_meta_item.span))
1076             .collect()
1077     })
1078 }
1079
1080 // Rewrite `extern crate foo;` WITHOUT attributes.
1081 pub fn rewrite_extern_crate(context: &RewriteContext, item: &ast::Item) -> Option<String> {
1082     assert!(is_extern_crate(item));
1083     let new_str = context.snippet(item.span);
1084     Some(if contains_comment(new_str) {
1085         new_str.to_owned()
1086     } else {
1087         let no_whitespace = &new_str.split_whitespace().collect::<Vec<&str>>().join(" ");
1088         String::from(&*Regex::new(r"\s;").unwrap().replace(no_whitespace, ";"))
1089     })
1090 }
1091
1092 fn get_attrs_from_stmt(stmt: &ast::Stmt) -> &[ast::Attribute] {
1093     match stmt.node {
1094         ast::StmtKind::Local(ref local) => &local.attrs,
1095         ast::StmtKind::Item(ref item) => &item.attrs,
1096         ast::StmtKind::Expr(ref expr) | ast::StmtKind::Semi(ref expr) => &expr.attrs,
1097         ast::StmtKind::Mac(ref mac) => &mac.2,
1098     }
1099 }