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, visit};
  15 use syntax::attr::HasAttrs;
  16 use syntax::codemap::{self, BytePos, CodeMap, Pos, Span};
  17 use syntax::parse::ParseSess;
  18
  19 use expr::rewrite_literal;
  20 use spanned::Spanned;
  21 use codemap::{LineRangeUtils, SpanUtils};
  22 use comment::{combine_strs_with_missing_comments, contains_comment, remove_trailing_white_spaces,
  23               CodeCharKind, CommentCodeSlices, FindUncommented};
  24 use comment::rewrite_comment;
  25 use config::{BraceStyle, Config};
  26 use items::{format_impl, format_trait, rewrite_associated_impl_type, rewrite_associated_type,
  27             rewrite_type_alias, FnSig, StaticParts, StructParts};
  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 shape::{Indent, Shape};
  34 use utils::{self, contains_skip, inner_attributes, mk_sp, ptr_vec_to_ref_vec};
  35
  36 fn is_use_item(item: &ast::Item) -> bool {
  37     match item.node {
  38         ast::ItemKind::Use(_) => true,
  39         _ => false,
  40     }
  41 }
  42
  43 fn is_extern_crate(item: &ast::Item) -> bool {
  44     match item.node {
  45         ast::ItemKind::ExternCrate(..) => true,
  46         _ => false,
  47     }
  48 }
  49
  50 pub struct FmtVisitor<'a> {
  51     pub parse_session: &'a ParseSess,
  52     pub codemap: &'a CodeMap,
  53     pub buffer: StringBuffer,
  54     pub last_pos: BytePos,
  55     // FIXME: use an RAII util or closure for indenting
  56     pub block_indent: Indent,
  57     pub config: &'a Config,
  58     pub is_if_else_block: bool,
  59 }
  60
  61 impl<'a> FmtVisitor<'a> {
  62     pub fn shape(&self) -> Shape {
  63         Shape::indented(self.block_indent, self.config)
  64     }
  65
  66     fn visit_stmt(&mut self, stmt: &ast::Stmt) {
  67         debug!(
  68             "visit_stmt: {:?} {:?}",
  69             self.codemap.lookup_char_pos(stmt.span.lo()),
  70             self.codemap.lookup_char_pos(stmt.span.hi())
  71         );
  72
  73         match stmt.node {
  74             ast::StmtKind::Item(ref item) => {
  75                 self.visit_item(item);
  76             }
  77             ast::StmtKind::Local(..) | ast::StmtKind::Expr(..) | ast::StmtKind::Semi(..) => {
  78                 let rewrite = stmt.rewrite(&self.get_context(), self.shape());
  79                 self.push_rewrite(stmt.span(), rewrite)
  80             }
  81             ast::StmtKind::Mac(ref mac) => {
  82                 let (ref mac, _macro_style, ref attrs) = **mac;
  83                 if self.visit_attrs(attrs, ast::AttrStyle::Outer) {
  84                     self.push_rewrite(stmt.span(), None);
  85                 } else {
  86                     self.visit_mac(mac, None, MacroPosition::Statement);
  87                 }
  88                 self.format_missing(stmt.span.hi());
  89             }
  90         }
  91     }
  92
  93     pub fn visit_block(
  94         &mut self,
  95         b: &ast::Block,
  96         inner_attrs: Option<&[ast::Attribute]>,
  97         has_braces: bool,
  98     ) {
  99         debug!(
 100             "visit_block: {:?} {:?}",
 101             self.codemap.lookup_char_pos(b.span.lo()),
 102             self.codemap.lookup_char_pos(b.span.hi())
 103         );
 104
 105         // Check if this block has braces.
 106         let brace_compensation = BytePos(if has_braces { 1 } else { 0 });
 107
 108         self.last_pos = self.last_pos + brace_compensation;
 109         self.block_indent = self.block_indent.block_indent(self.config);
 110         self.buffer.push_str("{");
 111
 112         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 113             if let Some(first_stmt) = b.stmts.first() {
 114                 let attr_lo = inner_attrs
 115                     .and_then(|attrs| inner_attributes(attrs).first().map(|attr| attr.span.lo()))
 116                     .or_else(|| {
 117                         // Attributes for an item in a statement position
 118                         // do not belong to the statement. (rust-lang/rust#34459)
 119                         if let ast::StmtKind::Item(ref item) = first_stmt.node {
 120                             item.attrs.first()
 121                         } else {
 122                             first_stmt.attrs().first()
 123                         }.and_then(|attr| {
 124                             // Some stmts can have embedded attributes.
 125                             // e.g. `match { #![attr] ... }`
 126                             let attr_lo = attr.span.lo();
 127                             if attr_lo < first_stmt.span.lo() {
 128                                 Some(attr_lo)
 129                             } else {
 130                                 None
 131                             }
 132                         })
 133                     });
 134
 135                 let snippet = self.snippet(mk_sp(
 136                     self.last_pos,
 137                     attr_lo.unwrap_or(first_stmt.span.lo()),
 138                 ));
 139                 let len = CommentCodeSlices::new(&snippet)
 140                     .nth(0)
 141                     .and_then(|(kind, _, s)| {
 142                         if kind == CodeCharKind::Normal {
 143                             s.rfind('\n')
 144                         } else {
 145                             None
 146                         }
 147                     });
 148                 if let Some(len) = len {
 149                     self.last_pos = self.last_pos + BytePos::from_usize(len);
 150                 }
 151             }
 152         }
 153
 154         // Format inner attributes if available.
 155         let skip_rewrite = if let Some(attrs) = inner_attrs {
 156             self.visit_attrs(attrs, ast::AttrStyle::Inner)
 157         } else {
 158             false
 159         };
 160
 161         if skip_rewrite {
 162             self.push_rewrite(b.span, None);
 163             self.close_block(false);
 164             self.last_pos = source!(self, b.span).hi();
 165             return;
 166         }
 167
 168         self.walk_block_stmts(b);
 169
 170         if !b.stmts.is_empty() {
 171             if let Some(expr) = utils::stmt_expr(&b.stmts[b.stmts.len() - 1]) {
 172                 if utils::semicolon_for_expr(&self.get_context(), expr) {
 173                     self.buffer.push_str(";");
 174                 }
 175             }
 176         }
 177
 178         let mut remove_len = BytePos(0);
 179         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 180             if let Some(stmt) = b.stmts.last() {
 181                 let snippet = self.snippet(mk_sp(
 182                     stmt.span.hi(),
 183                     source!(self, b.span).hi() - brace_compensation,
 184                 ));
 185                 let len = CommentCodeSlices::new(&snippet)
 186                     .last()
 187                     .and_then(|(kind, _, s)| {
 188                         if kind == CodeCharKind::Normal && s.trim().is_empty() {
 189                             Some(s.len())
 190                         } else {
 191                             None
 192                         }
 193                     });
 194                 if let Some(len) = len {
 195                     remove_len = BytePos::from_usize(len);
 196                 }
 197             }
 198         }
 199
 200         let unindent_comment = (self.is_if_else_block && !b.stmts.is_empty()) && {
 201             let end_pos = source!(self, b.span).hi() - brace_compensation - remove_len;
 202             let snippet = self.snippet(mk_sp(self.last_pos, end_pos));
 203             snippet.contains("//") || snippet.contains("/*")
 204         };
 205         // FIXME: we should compress any newlines here to just one
 206         if unindent_comment {
 207             self.block_indent = self.block_indent.block_unindent(self.config);
 208         }
 209         self.format_missing_with_indent(
 210             source!(self, b.span).hi() - brace_compensation - remove_len,
 211         );
 212         if unindent_comment {
 213             self.block_indent = self.block_indent.block_indent(self.config);
 214         }
 215         self.close_block(unindent_comment);
 216         self.last_pos = source!(self, b.span).hi();
 217     }
 218
 219     // FIXME: this is a terrible hack to indent the comments between the last
 220     // item in the block and the closing brace to the block's level.
 221     // The closing brace itself, however, should be indented at a shallower
 222     // level.
 223     fn close_block(&mut self, unindent_comment: bool) {
 224         let total_len = self.buffer.len;
 225         let chars_too_many = if unindent_comment {
 226             0
 227         } else if self.config.hard_tabs() {
 228             1
 229         } else {
 230             self.config.tab_spaces()
 231         };
 232         self.buffer.truncate(total_len - chars_too_many);
 233         self.buffer.push_str("}");
 234         self.block_indent = self.block_indent.block_unindent(self.config);
 235     }
 236
 237     // Note that this only gets called for function definitions. Required methods
 238     // on traits do not get handled here.
 239     fn visit_fn(
 240         &mut self,
 241         fk: visit::FnKind,
 242         generics: &ast::Generics,
 243         fd: &ast::FnDecl,
 244         s: Span,
 245         defaultness: ast::Defaultness,
 246         inner_attrs: Option<&[ast::Attribute]>,
 247     ) {
 248         let indent = self.block_indent;
 249         let block;
 250         let rewrite = match fk {
 251             visit::FnKind::ItemFn(ident, _, _, _, _, b) | visit::FnKind::Method(ident, _, _, b) => {
 252                 block = b;
 253                 self.rewrite_fn(
 254                     indent,
 255                     ident,
 256                     &FnSig::from_fn_kind(&fk, generics, fd, defaultness),
 257                     mk_sp(s.lo(), b.span.lo()),
 258                     b,
 259                 )
 260             }
 261             visit::FnKind::Closure(_) => unreachable!(),
 262         };
 263
 264         if let Some(fn_str) = rewrite {
 265             self.format_missing_with_indent(source!(self, s).lo());
 266             self.buffer.push_str(&fn_str);
 267             if let Some(c) = fn_str.chars().last() {
 268                 if c == '}' {
 269                     self.last_pos = source!(self, block.span).hi();
 270                     return;
 271                 }
 272             }
 273         } else {
 274             self.format_missing(source!(self, block.span).lo());
 275         }
 276
 277         self.last_pos = source!(self, block.span).lo();
 278         self.visit_block(block, inner_attrs, true)
 279     }
 280
 281     pub fn visit_item(&mut self, item: &ast::Item) {
 282         skip_out_of_file_lines_range_visitor!(self, item.span);
 283
 284         // This is where we bail out if there is a skip attribute. This is only
 285         // complex in the module case. It is complex because the module could be
 286         // in a separate file and there might be attributes in both files, but
 287         // the AST lumps them all together.
 288         let filtered_attrs;
 289         let mut attrs = &item.attrs;
 290         match item.node {
 291             ast::ItemKind::Mod(ref m) => {
 292                 let outer_file = self.codemap.lookup_char_pos(item.span.lo()).file;
 293                 let inner_file = self.codemap.lookup_char_pos(m.inner.lo()).file;
 294                 if outer_file.name == inner_file.name {
 295                     // Module is inline, in this case we treat modules like any
 296                     // other item.
 297                     if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 298                         self.push_rewrite(item.span, None);
 299                         return;
 300                     }
 301                 } else if contains_skip(&item.attrs) {
 302                     // Module is not inline, but should be skipped.
 303                     return;
 304                 } else {
 305                     // Module is not inline and should not be skipped. We want
 306                     // to process only the attributes in the current file.
 307                     filtered_attrs = item.attrs
 308                         .iter()
 309                         .filter_map(|a| {
 310                             let attr_file = self.codemap.lookup_char_pos(a.span.lo()).file;
 311                             if attr_file.name == outer_file.name {
 312                                 Some(a.clone())
 313                             } else {
 314                                 None
 315                             }
 316                         })
 317                         .collect::<Vec<_>>();
 318                     // Assert because if we should skip it should be caught by
 319                     // the above case.
 320                     assert!(!self.visit_attrs(&filtered_attrs, ast::AttrStyle::Outer));
 321                     attrs = &filtered_attrs;
 322                 }
 323             }
 324             _ => {
 325                 if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 326                     self.push_rewrite(item.span, None);
 327                     return;
 328                 }
 329             }
 330         }
 331
 332         match item.node {
 333             ast::ItemKind::Use(ref vp) => self.format_import(item, vp),
 334             ast::ItemKind::Impl(..) => {
 335                 let snippet = self.snippet(item.span);
 336                 let where_span_end = snippet
 337                     .find_uncommented("{")
 338                     .map(|x| (BytePos(x as u32)) + source!(self, item.span).lo());
 339                 let rw = format_impl(&self.get_context(), item, self.block_indent, where_span_end);
 340                 self.push_rewrite(item.span, rw);
 341             }
 342             ast::ItemKind::Trait(..) => {
 343                 let rw = format_trait(&self.get_context(), item, self.block_indent);
 344                 self.push_rewrite(item.span, rw);
 345             }
 346             ast::ItemKind::ExternCrate(_) => {
 347                 let rw = rewrite_extern_crate(&self.get_context(), item);
 348                 self.push_rewrite(item.span, rw);
 349             }
 350             ast::ItemKind::Struct(..) | ast::ItemKind::Union(..) => {
 351                 self.visit_struct(&StructParts::from_item(item));
 352             }
 353             ast::ItemKind::Enum(ref def, ref generics) => {
 354                 self.format_missing_with_indent(source!(self, item.span).lo());
 355                 self.visit_enum(item.ident, &item.vis, def, generics, item.span);
 356                 self.last_pos = source!(self, item.span).hi();
 357             }
 358             ast::ItemKind::Mod(ref module) => {
 359                 self.format_missing_with_indent(source!(self, item.span).lo());
 360                 self.format_mod(module, &item.vis, item.span, item.ident, attrs);
 361             }
 362             ast::ItemKind::Mac(ref mac) => {
 363                 self.visit_mac(mac, Some(item.ident), MacroPosition::Item);
 364             }
 365             ast::ItemKind::ForeignMod(ref foreign_mod) => {
 366                 self.format_missing_with_indent(source!(self, item.span).lo());
 367                 self.format_foreign_mod(foreign_mod, item.span);
 368             }
 369             ast::ItemKind::Static(..) | ast::ItemKind::Const(..) => {
 370                 self.visit_static(&StaticParts::from_item(item));
 371             }
 372             ast::ItemKind::AutoImpl(..) => {
 373                 // FIXME(#78): format impl definitions.
 374             }
 375             ast::ItemKind::Fn(ref decl, unsafety, constness, abi, ref generics, ref body) => {
 376                 self.visit_fn(
 377                     visit::FnKind::ItemFn(item.ident, unsafety, constness, abi, &item.vis, body),
 378                     generics,
 379                     decl,
 380                     item.span,
 381                     ast::Defaultness::Final,
 382                     Some(&item.attrs),
 383                 )
 384             }
 385             ast::ItemKind::Ty(ref ty, ref generics) => {
 386                 let rewrite = rewrite_type_alias(
 387                     &self.get_context(),
 388                     self.block_indent,
 389                     item.ident,
 390                     ty,
 391                     generics,
 392                     &item.vis,
 393                     item.span,
 394                 );
 395                 self.push_rewrite(item.span, rewrite);
 396             }
 397             ast::ItemKind::GlobalAsm(..) => {
 398                 let snippet = Some(self.snippet(item.span));
 399                 self.push_rewrite(item.span, snippet);
 400             }
 401             ast::ItemKind::MacroDef(..) => {
 402                 // FIXME(#1539): macros 2.0
 403                 let mac_snippet = Some(remove_trailing_white_spaces(&self.snippet(item.span)));
 404                 self.push_rewrite(item.span, mac_snippet);
 405             }
 406         }
 407     }
 408
 409     pub fn visit_trait_item(&mut self, ti: &ast::TraitItem) {
 410         skip_out_of_file_lines_range_visitor!(self, ti.span);
 411
 412         if self.visit_attrs(&ti.attrs, ast::AttrStyle::Outer) {
 413             self.push_rewrite(ti.span, None);
 414             return;
 415         }
 416
 417         match ti.node {
 418             ast::TraitItemKind::Const(..) => self.visit_static(&StaticParts::from_trait_item(ti)),
 419             ast::TraitItemKind::Method(ref sig, None) => {
 420                 let indent = self.block_indent;
 421                 let rewrite =
 422                     self.rewrite_required_fn(indent, ti.ident, sig, &ti.generics, ti.span);
 423                 self.push_rewrite(ti.span, rewrite);
 424             }
 425             ast::TraitItemKind::Method(ref sig, Some(ref body)) => {
 426                 self.visit_fn(
 427                     visit::FnKind::Method(ti.ident, sig, None, body),
 428                     &ti.generics,
 429                     &sig.decl,
 430                     ti.span,
 431                     ast::Defaultness::Final,
 432                     Some(&ti.attrs),
 433                 );
 434             }
 435             ast::TraitItemKind::Type(ref type_param_bounds, ref type_default) => {
 436                 let rewrite = rewrite_associated_type(
 437                     ti.ident,
 438                     type_default.as_ref(),
 439                     Some(type_param_bounds),
 440                     &self.get_context(),
 441                     self.block_indent,
 442                 );
 443                 self.push_rewrite(ti.span, rewrite);
 444             }
 445             ast::TraitItemKind::Macro(ref mac) => {
 446                 self.visit_mac(mac, Some(ti.ident), MacroPosition::Item);
 447             }
 448         }
 449     }
 450
 451     pub fn visit_impl_item(&mut self, ii: &ast::ImplItem) {
 452         skip_out_of_file_lines_range_visitor!(self, ii.span);
 453
 454         if self.visit_attrs(&ii.attrs, ast::AttrStyle::Outer) {
 455             self.push_rewrite(ii.span, None);
 456             return;
 457         }
 458
 459         match ii.node {
 460             ast::ImplItemKind::Method(ref sig, ref body) => {
 461                 self.visit_fn(
 462                     visit::FnKind::Method(ii.ident, sig, Some(&ii.vis), body),
 463                     &ii.generics,
 464                     &sig.decl,
 465                     ii.span,
 466                     ii.defaultness,
 467                     Some(&ii.attrs),
 468                 );
 469             }
 470             ast::ImplItemKind::Const(..) => self.visit_static(&StaticParts::from_impl_item(ii)),
 471             ast::ImplItemKind::Type(ref ty) => {
 472                 let rewrite = rewrite_associated_impl_type(
 473                     ii.ident,
 474                     ii.defaultness,
 475                     Some(ty),
 476                     None,
 477                     &self.get_context(),
 478                     self.block_indent,
 479                 );
 480                 self.push_rewrite(ii.span, rewrite);
 481             }
 482             ast::ImplItemKind::Macro(ref mac) => {
 483                 self.visit_mac(mac, Some(ii.ident), MacroPosition::Item);
 484             }
 485         }
 486     }
 487
 488     fn visit_mac(&mut self, mac: &ast::Mac, ident: Option<ast::Ident>, pos: MacroPosition) {
 489         skip_out_of_file_lines_range_visitor!(self, mac.span);
 490
 491         // 1 = ;
 492         let shape = self.shape().sub_width(1).unwrap();
 493         let rewrite = rewrite_macro(mac, ident, &self.get_context(), shape, pos);
 494         self.push_rewrite(mac.span, rewrite);
 495     }
 496
 497     pub fn push_rewrite(&mut self, span: Span, rewrite: Option<String>) {
 498         self.format_missing_with_indent(source!(self, span).lo());
 499         let result = rewrite.unwrap_or_else(|| self.snippet(span));
 500         self.buffer.push_str(&result);
 501         self.last_pos = source!(self, span).hi();
 502     }
 503
 504     pub fn from_codemap(parse_session: &'a ParseSess, config: &'a Config) -> FmtVisitor<'a> {
 505         FmtVisitor {
 506             parse_session: parse_session,
 507             codemap: parse_session.codemap(),
 508             buffer: StringBuffer::new(),
 509             last_pos: BytePos(0),
 510             block_indent: Indent::empty(),
 511             config: config,
 512             is_if_else_block: false,
 513         }
 514     }
 515
 516     pub fn opt_snippet(&self, span: Span) -> Option<String> {
 517         self.codemap.span_to_snippet(span).ok()
 518     }
 519
 520     pub fn snippet(&self, span: Span) -> String {
 521         match self.codemap.span_to_snippet(span) {
 522             Ok(s) => s,
 523             Err(_) => {
 524                 eprintln!(
 525                     "Couldn't make snippet for span {:?}->{:?}",
 526                     self.codemap.lookup_char_pos(span.lo()),
 527                     self.codemap.lookup_char_pos(span.hi())
 528                 );
 529                 "".to_owned()
 530             }
 531         }
 532     }
 533
 534     // Returns true if we should skip the following item.
 535     pub fn visit_attrs(&mut self, attrs: &[ast::Attribute], style: ast::AttrStyle) -> bool {
 536         if contains_skip(attrs) {
 537             return true;
 538         }
 539
 540         let attrs: Vec<_> = attrs.iter().filter(|a| a.style == style).cloned().collect();
 541         if attrs.is_empty() {
 542             return false;
 543         }
 544
 545         let rewrite = attrs.rewrite(&self.get_context(), self.shape());
 546         let span = mk_sp(attrs[0].span.lo(), attrs[attrs.len() - 1].span.hi());
 547         self.push_rewrite(span, rewrite);
 548
 549         false
 550     }
 551
 552     fn reorder_items<F>(&mut self, items_left: &[&ast::Item], is_item: &F, in_group: bool) -> usize
 553     where
 554         F: Fn(&ast::Item) -> bool,
 555     {
 556         let mut last = self.codemap.lookup_line_range(items_left[0].span());
 557         let item_length = items_left
 558             .iter()
 559             .take_while(|ppi| {
 560                 is_item(&***ppi) && (!in_group || {
 561                     let current = self.codemap.lookup_line_range(ppi.span());
 562                     let in_same_group = current.lo < last.hi + 2;
 563                     last = current;
 564                     in_same_group
 565                 })
 566             })
 567             .count();
 568         let items = &items_left[..item_length];
 569
 570         let at_least_one_in_file_lines = items
 571             .iter()
 572             .any(|item| !out_of_file_lines_range!(self, item.span));
 573
 574         if at_least_one_in_file_lines {
 575             self.format_imports(items);
 576         } else {
 577             for item in items {
 578                 self.push_rewrite(item.span, None);
 579             }
 580         }
 581
 582         item_length
 583     }
 584
 585     fn walk_items(&mut self, mut items_left: &[&ast::Item]) {
 586         while !items_left.is_empty() {
 587             // If the next item is a `use` declaration, then extract it and any subsequent `use`s
 588             // to be potentially reordered within `format_imports`. Otherwise, just format the
 589             // next item for output.
 590             if self.config.reorder_imports() && is_use_item(&*items_left[0]) {
 591                 let used_items_len = self.reorder_items(
 592                     items_left,
 593                     &is_use_item,
 594                     self.config.reorder_imports_in_group(),
 595                 );
 596                 let (_, rest) = items_left.split_at(used_items_len);
 597                 items_left = rest;
 598             } else if self.config.reorder_extern_crates() && is_extern_crate(&*items_left[0]) {
 599                 let used_items_len = self.reorder_items(
 600                     items_left,
 601                     &is_extern_crate,
 602                     self.config.reorder_extern_crates_in_group(),
 603                 );
 604                 let (_, rest) = items_left.split_at(used_items_len);
 605                 items_left = rest;
 606             } else {
 607                 // `unwrap()` is safe here because we know `items_left`
 608                 // has elements from the loop condition
 609                 let (item, rest) = items_left.split_first().unwrap();
 610                 self.visit_item(item);
 611                 items_left = rest;
 612             }
 613         }
 614     }
 615
 616     fn walk_mod_items(&mut self, m: &ast::Mod) {
 617         self.walk_items(&ptr_vec_to_ref_vec(&m.items));
 618     }
 619
 620     fn walk_stmts(&mut self, stmts: &[ast::Stmt]) {
 621         fn to_stmt_item(stmt: &ast::Stmt) -> Option<&ast::Item> {
 622             match stmt.node {
 623                 ast::StmtKind::Item(ref item) => Some(&**item),
 624                 _ => None,
 625             }
 626         }
 627
 628         if stmts.is_empty() {
 629             return;
 630         }
 631
 632         // Extract leading `use ...;`.
 633         let items: Vec<_> = stmts
 634             .iter()
 635             .take_while(|stmt| to_stmt_item(stmt).is_some())
 636             .filter_map(|stmt| to_stmt_item(stmt))
 637             .take_while(|item| is_use_item(item))
 638             .collect();
 639
 640         if items.is_empty() {
 641             self.visit_stmt(&stmts[0]);
 642             self.walk_stmts(&stmts[1..]);
 643         } else {
 644             self.walk_items(&items);
 645             self.walk_stmts(&stmts[items.len()..]);
 646         }
 647     }
 648
 649     fn walk_block_stmts(&mut self, b: &ast::Block) {
 650         self.walk_stmts(&b.stmts)
 651     }
 652
 653     fn format_mod(
 654         &mut self,
 655         m: &ast::Mod,
 656         vis: &ast::Visibility,
 657         s: Span,
 658         ident: ast::Ident,
 659         attrs: &[ast::Attribute],
 660     ) {
 661         // Decide whether this is an inline mod or an external mod.
 662         let local_file_name = self.codemap.span_to_filename(s);
 663         let inner_span = source!(self, m.inner);
 664         let is_internal = !(inner_span.lo().0 == 0 && inner_span.hi().0 == 0)
 665             && local_file_name == self.codemap.span_to_filename(inner_span);
 666
 667         self.buffer.push_str(&*utils::format_visibility(vis));
 668         self.buffer.push_str("mod ");
 669         self.buffer.push_str(&ident.to_string());
 670
 671         if is_internal {
 672             match self.config.brace_style() {
 673                 BraceStyle::AlwaysNextLine => self.buffer
 674                     .push_str(&format!("\n{}{{", self.block_indent.to_string(self.config))),
 675                 _ => self.buffer.push_str(" {"),
 676             }
 677             // Hackery to account for the closing }.
 678             let mod_lo = self.codemap.span_after(source!(self, s), "{");
 679             let body_snippet =
 680                 self.snippet(mk_sp(mod_lo, source!(self, m.inner).hi() - BytePos(1)));
 681             let body_snippet = body_snippet.trim();
 682             if body_snippet.is_empty() {
 683                 self.buffer.push_str("}");
 684             } else {
 685                 self.last_pos = mod_lo;
 686                 self.block_indent = self.block_indent.block_indent(self.config);
 687                 self.visit_attrs(attrs, ast::AttrStyle::Inner);
 688                 self.walk_mod_items(m);
 689                 self.format_missing_with_indent(source!(self, m.inner).hi() - BytePos(1));
 690                 self.close_block(false);
 691             }
 692             self.last_pos = source!(self, m.inner).hi();
 693         } else {
 694             self.buffer.push_str(";");
 695             self.last_pos = source!(self, s).hi();
 696         }
 697     }
 698
 699     pub fn format_separate_mod(&mut self, m: &ast::Mod, filemap: &codemap::FileMap) {
 700         self.block_indent = Indent::empty();
 701         self.walk_mod_items(m);
 702         self.format_missing_with_indent(filemap.end_pos);
 703     }
 704
 705     pub fn skip_empty_lines(&mut self, end_pos: BytePos) {
 706         while let Some(pos) = self.codemap
 707             .opt_span_after(mk_sp(self.last_pos, end_pos), "\n")
 708         {
 709             if let Some(snippet) = self.opt_snippet(mk_sp(self.last_pos, pos)) {
 710                 if snippet.trim().is_empty() {
 711                     self.last_pos = pos;
 712                 } else {
 713                     return;
 714                 }
 715             }
 716         }
 717     }
 718
 719     pub fn get_context(&self) -> RewriteContext {
 720         RewriteContext {
 721             parse_session: self.parse_session,
 722             codemap: self.codemap,
 723             config: self.config,
 724             inside_macro: false,
 725             use_block: false,
 726             is_if_else_block: false,
 727             force_one_line_chain: false,
 728         }
 729     }
 730 }
 731
 732 impl Rewrite for ast::NestedMetaItem {
 733     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 734         match self.node {
 735             ast::NestedMetaItemKind::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
 736             ast::NestedMetaItemKind::Literal(ref l) => rewrite_literal(context, l, shape),
 737         }
 738     }
 739 }
 740
 741 impl Rewrite for ast::MetaItem {
 742     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 743         Some(match self.node {
 744             ast::MetaItemKind::Word => String::from(&*self.name.as_str()),
 745             ast::MetaItemKind::List(ref list) => {
 746                 let name = self.name.as_str();
 747                 // 1 = `(`, 2 = `]` and `)`
 748                 let item_shape = shape
 749                     .visual_indent(0)
 750                     .shrink_left(name.len() + 1)
 751                     .and_then(|s| s.sub_width(2))?;
 752                 let items = itemize_list(
 753                     context.codemap,
 754                     list.iter(),
 755                     ")",
 756                     ",",
 757                     |nested_meta_item| nested_meta_item.span.lo(),
 758                     |nested_meta_item| nested_meta_item.span.hi(),
 759                     |nested_meta_item| nested_meta_item.rewrite(context, item_shape),
 760                     self.span.lo(),
 761                     self.span.hi(),
 762                     false,
 763                 );
 764                 let item_vec = items.collect::<Vec<_>>();
 765                 let fmt = ListFormatting {
 766                     tactic: DefinitiveListTactic::Mixed,
 767                     separator: ",",
 768                     trailing_separator: SeparatorTactic::Never,
 769                     separator_place: SeparatorPlace::Back,
 770                     shape: item_shape,
 771                     ends_with_newline: false,
 772                     preserve_newline: false,
 773                     config: context.config,
 774                 };
 775                 format!("{}({})", name, write_list(&item_vec, &fmt)?)
 776             }
 777             ast::MetaItemKind::NameValue(ref literal) => {
 778                 let name = self.name.as_str();
 779                 // 3 = ` = `
 780                 let lit_shape = shape.shrink_left(name.len() + 3)?;
 781                 let value = rewrite_literal(context, literal, lit_shape)?;
 782                 format!("{} = {}", name, value)
 783             }
 784         })
 785     }
 786 }
 787
 788 impl Rewrite for ast::Attribute {
 789     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 790         let prefix = match self.style {
 791             ast::AttrStyle::Inner => "#!",
 792             ast::AttrStyle::Outer => "#",
 793         };
 794         let snippet = context.snippet(self.span);
 795         if self.is_sugared_doc {
 796             let doc_shape = Shape {
 797                 width: cmp::min(shape.width, context.config.comment_width())
 798                     .checked_sub(shape.indent.width())
 799                     .unwrap_or(0),
 800                 ..shape
 801             };
 802             rewrite_comment(&snippet, false, doc_shape, context.config)
 803         } else {
 804             if contains_comment(&snippet) {
 805                 return Some(snippet);
 806             }
 807             // 1 = `[`
 808             let shape = shape.offset_left(prefix.len() + 1)?;
 809             self.meta()?
 810                 .rewrite(context, shape)
 811                 .map(|rw| format!("{}[{}]", prefix, rw))
 812         }
 813     }
 814 }
 815
 816 /// Returns the first group of attributes that fills the given predicate.
 817 /// We consider two doc comments are in different group if they are separated by normal comments.
 818 fn take_while_with_pred<'a, P>(
 819     context: &RewriteContext,
 820     attrs: &'a [ast::Attribute],
 821     pred: P,
 822 ) -> &'a [ast::Attribute]
 823 where
 824     P: Fn(&ast::Attribute) -> bool,
 825 {
 826     let mut last_index = 0;
 827     let mut iter = attrs.iter().enumerate().peekable();
 828     while let Some((i, attr)) = iter.next() {
 829         if !pred(attr) {
 830             break;
 831         }
 832         if let Some(&(_, next_attr)) = iter.peek() {
 833             // Extract comments between two attributes.
 834             let span_between_attr = mk_sp(attr.span.hi(), next_attr.span.lo());
 835             let snippet = context.snippet(span_between_attr);
 836             if snippet.chars().filter(|c| *c == '\n').count() >= 2 || snippet.contains('/') {
 837                 break;
 838             }
 839         }
 840         last_index = i;
 841     }
 842     if last_index == 0 {
 843         &[]
 844     } else {
 845         &attrs[..last_index + 1]
 846     }
 847 }
 848
 849 fn rewrite_first_group_attrs(
 850     context: &RewriteContext,
 851     attrs: &[ast::Attribute],
 852     shape: Shape,
 853 ) -> Option<(usize, String)> {
 854     if attrs.is_empty() {
 855         return Some((0, String::new()));
 856     }
 857     // Rewrite doc comments
 858     let sugared_docs = take_while_with_pred(context, attrs, |a| a.is_sugared_doc);
 859     if !sugared_docs.is_empty() {
 860         let snippet = sugared_docs
 861             .iter()
 862             .map(|a| context.snippet(a.span))
 863             .collect::<Vec<_>>()
 864             .join("\n");
 865         return Some((
 866             sugared_docs.len(),
 867             rewrite_comment(&snippet, false, shape, context.config)?,
 868         ));
 869     }
 870     // Rewrite `#[derive(..)]`s.
 871     if context.config.merge_derives() {
 872         let derives = take_while_with_pred(context, attrs, is_derive);
 873         if !derives.is_empty() {
 874             let mut derive_args = vec![];
 875             for derive in derives {
 876                 derive_args.append(&mut get_derive_args(context, derive)?);
 877             }
 878             return Some((derives.len(), format_derive(context, &derive_args, shape)?));
 879         }
 880     }
 881     // Rewrite the first attribute.
 882     Some((1, attrs[0].rewrite(context, shape)?))
 883 }
 884
 885 fn has_newlines_before_after_comment(comment: &str) -> (&str, &str) {
 886     // Look at before and after comment and see if there are any empty lines.
 887     let comment_begin = comment.chars().position(|c| c == '/');
 888     let len = comment_begin.unwrap_or_else(|| comment.len());
 889     let mlb = comment.chars().take(len).filter(|c| *c == '\n').count() > 1;
 890     let mla = if comment_begin.is_none() {
 891         mlb
 892     } else {
 893         let comment_end = comment.chars().rev().position(|c| !c.is_whitespace());
 894         let len = comment_end.unwrap();
 895         comment
 896             .chars()
 897             .rev()
 898             .take(len)
 899             .filter(|c| *c == '\n')
 900             .count() > 1
 901     };
 902     (if mlb { "\n" } else { "" }, if mla { "\n" } else { "" })
 903 }
 904
 905 impl<'a> Rewrite for [ast::Attribute] {
 906     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 907         if self.is_empty() {
 908             return Some(String::new());
 909         }
 910         let (first_group_len, first_group_str) = rewrite_first_group_attrs(context, self, shape)?;
 911         if self.len() == 1 || first_group_len == self.len() {
 912             Some(first_group_str)
 913         } else {
 914             let rest_str = self[first_group_len..].rewrite(context, shape)?;
 915             let missing_span = mk_sp(
 916                 self[first_group_len - 1].span.hi(),
 917                 self[first_group_len].span.lo(),
 918             );
 919             // Preserve an empty line before/after doc comments.
 920             if self[0].is_sugared_doc || self[first_group_len].is_sugared_doc {
 921                 let snippet = context.snippet(missing_span);
 922                 let (mla, mlb) = has_newlines_before_after_comment(&snippet);
 923                 let comment = ::comment::recover_missing_comment_in_span(
 924                     missing_span,
 925                     shape.with_max_width(context.config),
 926                     context,
 927                     0,
 928                 )?;
 929                 let comment = if comment.is_empty() {
 930                     format!("\n{}", mlb)
 931                 } else {
 932                     format!("{}{}\n{}", mla, comment, mlb)
 933                 };
 934                 Some(format!(
 935                     "{}{}{}{}",
 936                     first_group_str,
 937                     comment,
 938                     shape.indent.to_string(context.config),
 939                     rest_str
 940                 ))
 941             } else {
 942                 combine_strs_with_missing_comments(
 943                     context,
 944                     &first_group_str,
 945                     &rest_str,
 946                     missing_span,
 947                     shape,
 948                     false,
 949                 )
 950             }
 951         }
 952     }
 953 }
 954
 955 // Format `#[derive(..)]`, using visual indent & mixed style when we need to go multiline.
 956 fn format_derive(context: &RewriteContext, derive_args: &[String], shape: Shape) -> Option<String> {
 957     let mut result = String::with_capacity(128);
 958     result.push_str("#[derive(");
 959     // 11 = `#[derive()]`
 960     let initial_budget = shape.width.checked_sub(11)?;
 961     let mut budget = initial_budget;
 962     let num = derive_args.len();
 963     for (i, a) in derive_args.iter().enumerate() {
 964         // 2 = `, ` or `)]`
 965         let width = a.len() + 2;
 966         if width > budget {
 967             if i > 0 {
 968                 // Remove trailing whitespace.
 969                 result.pop();
 970             }
 971             result.push('\n');
 972             // 9 = `#[derive(`
 973             result.push_str(&(shape.indent + 9).to_string(context.config));
 974             budget = initial_budget;
 975         } else {
 976             budget = budget.checked_sub(width).unwrap_or(0);
 977         }
 978         result.push_str(a);
 979         if i != num - 1 {
 980             result.push_str(", ")
 981         }
 982     }
 983     result.push_str(")]");
 984     Some(result)
 985 }
 986
 987 fn is_derive(attr: &ast::Attribute) -> bool {
 988     match attr.meta() {
 989         Some(meta_item) => match meta_item.node {
 990             ast::MetaItemKind::List(..) => meta_item.name.as_str() == "derive",
 991             _ => false,
 992         },
 993         _ => false,
 994     }
 995 }
 996
 997 /// Returns the arguments of `#[derive(...)]`.
 998 fn get_derive_args(context: &RewriteContext, attr: &ast::Attribute) -> Option<Vec<String>> {
 999     attr.meta().and_then(|meta_item| match meta_item.node {
1000         ast::MetaItemKind::List(ref args) if meta_item.name.as_str() == "derive" => {
1001             // Every argument of `derive` should be `NestedMetaItemKind::Literal`.
1002             Some(
1003                 args.iter()
1004                     .map(|a| context.snippet(a.span))
1005                     .collect::<Vec<_>>(),
1006             )
1007         }
1008         _ => None,
1009     })
1010 }
1011
1012 // Rewrite `extern crate foo;` WITHOUT attributes.
1013 pub fn rewrite_extern_crate(context: &RewriteContext, item: &ast::Item) -> Option<String> {
1014     assert!(is_extern_crate(item));
1015     let new_str = context.snippet(item.span);
1016     Some(if contains_comment(&new_str) {
1017         new_str
1018     } else {
1019         let no_whitespace = &new_str.split_whitespace().collect::<Vec<&str>>().join(" ");
1020         String::from(&*Regex::new(r"\s;").unwrap().replace(no_whitespace, ";"))
1021     })
1022 }