src/items.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 // Formatting top-level items - functions, structs, enums, traits, impls.
  12
  13 use {Indent, Shape, Spanned};
  14 use codemap::SpanUtils;
  15 use utils::{format_mutability, format_visibility, contains_skip, end_typaram, wrap_str,
  16             last_line_width, format_unsafety, trim_newlines, stmt_expr, semicolon_for_expr,
  17             trimmed_last_line_width, colon_spaces, mk_sp};
  18 use lists::{write_list, itemize_list, ListItem, ListFormatting, SeparatorTactic,
  19             DefinitiveListTactic, ListTactic, definitive_tactic};
  20 use expr::{format_expr, is_empty_block, is_simple_block_stmt, rewrite_assign_rhs,
  21            rewrite_call_inner, ExprType};
  22 use comment::{FindUncommented, contains_comment, rewrite_comment, recover_comment_removed};
  23 use visitor::FmtVisitor;
  24 use rewrite::{Rewrite, RewriteContext};
  25 use config::{Config, IndentStyle, Density, ReturnIndent, BraceStyle, Style};
  26 use types::join_bounds;
  27 use vertical::rewrite_with_alignment;
  28
  29 use syntax::{ast, abi, ptr, symbol};
  30 use syntax::codemap::{Span, BytePos};
  31 use syntax::ast::ImplItem;
  32
  33 fn type_annotation_separator(config: &Config) -> &str {
  34     colon_spaces(
  35         config.space_before_type_annotation(),
  36         config.space_after_type_annotation_colon(),
  37     )
  38 }
  39
  40
  41 // Statements of the form
  42 // let pat: ty = init;
  43 impl Rewrite for ast::Local {
  44     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
  45         debug!(
  46             "Local::rewrite {:?} {} {:?}",
  47             self,
  48             shape.width,
  49             shape.indent
  50         );
  51         let mut result = "let ".to_owned();
  52
  53         // 4 = "let ".len()
  54         let pat_shape = try_opt!(shape.offset_left(4));
  55         // 1 = ;
  56         let pat_shape = try_opt!(pat_shape.sub_width(1));
  57         let pat_str = try_opt!(self.pat.rewrite(&context, pat_shape));
  58         result.push_str(&pat_str);
  59
  60         // String that is placed within the assignment pattern and expression.
  61         let infix = {
  62             let mut infix = String::new();
  63
  64             if let Some(ref ty) = self.ty {
  65                 let separator = type_annotation_separator(context.config);
  66                 let indent = shape.indent + last_line_width(&result) + separator.len();
  67                 // 1 = ;
  68                 let budget = try_opt!(shape.width.checked_sub(indent.width() + 1));
  69                 let rewrite = try_opt!(ty.rewrite(context, Shape::legacy(budget, indent)));
  70
  71                 infix.push_str(separator);
  72                 infix.push_str(&rewrite);
  73             }
  74
  75             if self.init.is_some() {
  76                 infix.push_str(" =");
  77             }
  78
  79             infix
  80         };
  81
  82         result.push_str(&infix);
  83
  84         if let Some(ref ex) = self.init {
  85             // 1 = trailing semicolon;
  86             let nested_shape = try_opt!(shape.sub_width(1));
  87
  88             result = try_opt!(rewrite_assign_rhs(&context, result, ex, nested_shape));
  89         }
  90
  91         result.push(';');
  92         Some(result)
  93     }
  94 }
  95
  96 // TODO convert to using rewrite style rather than visitor
  97 // TODO format modules in this style
  98 #[allow(dead_code)]
  99 struct Item<'a> {
 100     keyword: &'static str,
 101     abi: String,
 102     vis: Option<&'a ast::Visibility>,
 103     body: Vec<BodyElement<'a>>,
 104     span: Span,
 105 }
 106
 107 impl<'a> Item<'a> {
 108     fn from_foreign_mod(fm: &'a ast::ForeignMod, span: Span, config: &Config) -> Item<'a> {
 109         let abi = if fm.abi == abi::Abi::C && !config.force_explicit_abi() {
 110             "extern".into()
 111         } else {
 112             format!("extern {}", fm.abi)
 113         };
 114         Item {
 115             keyword: "",
 116             abi: abi,
 117             vis: None,
 118             body: fm.items
 119                 .iter()
 120                 .map(|i| BodyElement::ForeignItem(i))
 121                 .collect(),
 122             span: span,
 123         }
 124     }
 125 }
 126
 127 enum BodyElement<'a> {
 128     // Stmt(&'a ast::Stmt),
 129     // Field(&'a ast::Field),
 130     // Variant(&'a ast::Variant),
 131     // Item(&'a ast::Item),
 132     ForeignItem(&'a ast::ForeignItem),
 133 }
 134
 135 impl<'a> FmtVisitor<'a> {
 136     fn format_item(&mut self, item: Item) {
 137         self.buffer.push_str(&item.abi);
 138         self.buffer.push_str(" ");
 139
 140         let snippet = self.snippet(item.span);
 141         let brace_pos = snippet.find_uncommented("{").unwrap();
 142
 143         self.buffer.push_str("{");
 144         if !item.body.is_empty() || contains_comment(&snippet[brace_pos..]) {
 145             // FIXME: this skips comments between the extern keyword and the opening
 146             // brace.
 147             self.last_pos = item.span.lo + BytePos(brace_pos as u32 + 1);
 148             self.block_indent = self.block_indent.block_indent(self.config);
 149
 150             if item.body.is_empty() {
 151                 self.format_missing_no_indent(item.span.hi - BytePos(1));
 152                 self.block_indent = self.block_indent.block_unindent(self.config);
 153
 154                 self.buffer
 155                     .push_str(&self.block_indent.to_string(self.config));
 156             } else {
 157                 for item in &item.body {
 158                     self.format_body_element(item);
 159                 }
 160
 161                 self.block_indent = self.block_indent.block_unindent(self.config);
 162                 self.format_missing_with_indent(item.span.hi - BytePos(1));
 163             }
 164         }
 165
 166         self.buffer.push_str("}");
 167         self.last_pos = item.span.hi;
 168     }
 169
 170     fn format_body_element(&mut self, element: &BodyElement) {
 171         match *element {
 172             BodyElement::ForeignItem(ref item) => self.format_foreign_item(item),
 173         }
 174     }
 175
 176     pub fn format_foreign_mod(&mut self, fm: &ast::ForeignMod, span: Span) {
 177         let item = Item::from_foreign_mod(fm, span, self.config);
 178         self.format_item(item);
 179     }
 180
 181     fn format_foreign_item(&mut self, item: &ast::ForeignItem) {
 182         self.format_missing_with_indent(item.span.lo);
 183         // Drop semicolon or it will be interpreted as comment.
 184         // FIXME: this may be a faulty span from libsyntax.
 185         let span = mk_sp(item.span.lo, item.span.hi - BytePos(1));
 186
 187         match item.node {
 188             ast::ForeignItemKind::Fn(ref fn_decl, ref generics) => {
 189                 let indent = self.block_indent;
 190                 let rewrite = rewrite_fn_base(
 191                     &self.get_context(),
 192                     indent,
 193                     item.ident,
 194                     fn_decl,
 195                     generics,
 196                     ast::Unsafety::Normal,
 197                     ast::Constness::NotConst,
 198                     ast::Defaultness::Final,
 199                     // These are not actually rust functions,
 200                     // but we format them as such.
 201                     abi::Abi::Rust,
 202                     &item.vis,
 203                     span,
 204                     false,
 205                     false,
 206                     false,
 207                 );
 208
 209                 match rewrite {
 210                     Some((new_fn, _)) => {
 211                         self.buffer.push_str(&new_fn);
 212                         self.buffer.push_str(";");
 213                     }
 214                     None => self.format_missing(item.span.hi),
 215                 }
 216             }
 217             ast::ForeignItemKind::Static(ref ty, is_mutable) => {
 218                 // FIXME(#21): we're dropping potential comments in between the
 219                 // function keywords here.
 220                 let vis = format_visibility(&item.vis);
 221                 let mut_str = if is_mutable { "mut " } else { "" };
 222                 let prefix = format!("{}static {}{}: ", vis, mut_str, item.ident);
 223                 let offset = self.block_indent + prefix.len();
 224                 // 1 = ;
 225                 let shape = Shape::indented(offset, self.config).sub_width(1).unwrap();
 226                 let rewrite = ty.rewrite(&self.get_context(), shape);
 227
 228                 match rewrite {
 229                     Some(result) => {
 230                         self.buffer.push_str(&prefix);
 231                         self.buffer.push_str(&result);
 232                         self.buffer.push_str(";");
 233                     }
 234                     None => self.format_missing(item.span.hi),
 235                 }
 236             }
 237         }
 238
 239         self.last_pos = item.span.hi;
 240     }
 241
 242     pub fn rewrite_fn(
 243         &mut self,
 244         indent: Indent,
 245         ident: ast::Ident,
 246         fd: &ast::FnDecl,
 247         generics: &ast::Generics,
 248         unsafety: ast::Unsafety,
 249         constness: ast::Constness,
 250         defaultness: ast::Defaultness,
 251         abi: abi::Abi,
 252         vis: &ast::Visibility,
 253         span: Span,
 254         block: &ast::Block,
 255     ) -> Option<String> {
 256         let mut newline_brace = newline_for_brace(self.config, &generics.where_clause);
 257         let context = self.get_context();
 258
 259         let block_snippet = self.snippet(mk_sp(block.span.lo, block.span.hi));
 260         let has_body = !block_snippet[1..block_snippet.len() - 1].trim().is_empty() ||
 261             !context.config.fn_empty_single_line();
 262
 263         let (mut result, force_newline_brace) = try_opt!(rewrite_fn_base(
 264             &context,
 265             indent,
 266             ident,
 267             fd,
 268             generics,
 269             unsafety,
 270             constness,
 271             defaultness,
 272             abi,
 273             vis,
 274             span,
 275             newline_brace,
 276             has_body,
 277             true,
 278         ));
 279
 280         if force_newline_brace {
 281             newline_brace = true;
 282         } else if self.config.fn_brace_style() != BraceStyle::AlwaysNextLine &&
 283                    !result.contains('\n')
 284         {
 285             newline_brace = false;
 286         }
 287
 288         // Prepare for the function body by possibly adding a newline and
 289         // indent.
 290         // FIXME we'll miss anything between the end of the signature and the
 291         // start of the body, but we need more spans from the compiler to solve
 292         // this.
 293         if newline_brace {
 294             result.push('\n');
 295             result.push_str(&indent.to_string(self.config));
 296         } else {
 297             result.push(' ');
 298         }
 299
 300         self.single_line_fn(&result, block).or_else(|| Some(result))
 301     }
 302
 303     pub fn rewrite_required_fn(
 304         &mut self,
 305         indent: Indent,
 306         ident: ast::Ident,
 307         sig: &ast::MethodSig,
 308         span: Span,
 309     ) -> Option<String> {
 310         // Drop semicolon or it will be interpreted as comment.
 311         let span = mk_sp(span.lo, span.hi - BytePos(1));
 312         let context = self.get_context();
 313
 314         let (mut result, _) = try_opt!(rewrite_fn_base(
 315             &context,
 316             indent,
 317             ident,
 318             &sig.decl,
 319             &sig.generics,
 320             sig.unsafety,
 321             sig.constness.node,
 322             ast::Defaultness::Final,
 323             sig.abi,
 324             &ast::Visibility::Inherited,
 325             span,
 326             false,
 327             false,
 328             false,
 329         ));
 330
 331         // Re-attach semicolon
 332         result.push(';');
 333
 334         Some(result)
 335     }
 336
 337     fn single_line_fn(&self, fn_str: &str, block: &ast::Block) -> Option<String> {
 338         if fn_str.contains('\n') {
 339             return None;
 340         }
 341
 342         let codemap = self.get_context().codemap;
 343
 344         if self.config.fn_empty_single_line() && is_empty_block(block, codemap) &&
 345             self.block_indent.width() + fn_str.len() + 2 <= self.config.max_width()
 346         {
 347             return Some(format!("{}{{}}", fn_str));
 348         }
 349
 350         if self.config.fn_single_line() && is_simple_block_stmt(block, codemap) {
 351             let rewrite = {
 352                 if let Some(ref stmt) = block.stmts.first() {
 353                     match stmt_expr(stmt) {
 354                         Some(e) => {
 355                             let suffix = if semicolon_for_expr(e) { ";" } else { "" };
 356
 357                             format_expr(
 358                                 &e,
 359                                 ExprType::Statement,
 360                                 &self.get_context(),
 361                                 Shape::indented(self.block_indent, self.config),
 362                             ).map(|s| s + suffix)
 363                                 .or_else(|| Some(self.snippet(e.span)))
 364                         }
 365                         None => {
 366                             stmt.rewrite(
 367                                 &self.get_context(),
 368                                 Shape::indented(self.block_indent, self.config),
 369                             )
 370                         }
 371                     }
 372                 } else {
 373                     None
 374                 }
 375             };
 376
 377             if let Some(res) = rewrite {
 378                 let width = self.block_indent.width() + fn_str.len() + res.len() + 4;
 379                 if !res.contains('\n') && width <= self.config.max_width() {
 380                     return Some(format!("{}{{ {} }}", fn_str, res));
 381                 }
 382             }
 383         }
 384
 385         None
 386     }
 387
 388     pub fn visit_enum(
 389         &mut self,
 390         ident: ast::Ident,
 391         vis: &ast::Visibility,
 392         enum_def: &ast::EnumDef,
 393         generics: &ast::Generics,
 394         span: Span,
 395     ) {
 396         let enum_header = format_header("enum ", ident, vis);
 397         self.buffer.push_str(&enum_header);
 398
 399         let enum_snippet = self.snippet(span);
 400         let brace_pos = enum_snippet.find_uncommented("{").unwrap();
 401         let body_start = span.lo + BytePos(brace_pos as u32 + 1);
 402         let generics_str = format_generics(
 403             &self.get_context(),
 404             generics,
 405             "{",
 406             "{",
 407             self.config.item_brace_style(),
 408             enum_def.variants.is_empty(),
 409             self.block_indent,
 410             mk_sp(span.lo, body_start),
 411             last_line_width(&enum_header),
 412         ).unwrap();
 413         self.buffer.push_str(&generics_str);
 414
 415         self.last_pos = body_start;
 416
 417         self.block_indent = self.block_indent.block_indent(self.config);
 418         let variant_list = self.format_variant_list(enum_def, body_start, span.hi - BytePos(1));
 419         match variant_list {
 420             Some(ref body_str) => self.buffer.push_str(body_str),
 421             None => {
 422                 if contains_comment(&enum_snippet[brace_pos..]) {
 423                     self.format_missing_no_indent(span.hi - BytePos(1))
 424                 } else {
 425                     self.format_missing(span.hi - BytePos(1))
 426                 }
 427             }
 428         }
 429         self.block_indent = self.block_indent.block_unindent(self.config);
 430
 431         if variant_list.is_some() || contains_comment(&enum_snippet[brace_pos..]) {
 432             self.buffer
 433                 .push_str(&self.block_indent.to_string(self.config));
 434         }
 435         self.buffer.push_str("}");
 436         self.last_pos = span.hi;
 437     }
 438
 439     // Format the body of an enum definition
 440     fn format_variant_list(
 441         &self,
 442         enum_def: &ast::EnumDef,
 443         body_lo: BytePos,
 444         body_hi: BytePos,
 445     ) -> Option<String> {
 446         if enum_def.variants.is_empty() {
 447             return None;
 448         }
 449         let mut result = String::with_capacity(1024);
 450         result.push('\n');
 451         let indentation = self.block_indent.to_string(self.config);
 452         result.push_str(&indentation);
 453
 454         let items = itemize_list(
 455             self.codemap,
 456             enum_def.variants.iter(),
 457             "}",
 458             |f| if !f.node.attrs.is_empty() {
 459                 f.node.attrs[0].span.lo
 460             } else {
 461                 f.span.lo
 462             },
 463             |f| f.span.hi,
 464             |f| self.format_variant(f),
 465             body_lo,
 466             body_hi,
 467         );
 468
 469         let shape = Shape::indented(self.block_indent, self.config)
 470             .sub_width(2)
 471             .unwrap();
 472         let fmt = ListFormatting {
 473             tactic: DefinitiveListTactic::Vertical,
 474             separator: ",",
 475             trailing_separator: self.config.trailing_comma(),
 476             shape: shape,
 477             ends_with_newline: true,
 478             config: self.config,
 479         };
 480
 481         let list = try_opt!(write_list(&items.collect::<Vec<_>>(), &fmt));
 482         result.push_str(&list);
 483         result.push('\n');
 484         Some(result)
 485     }
 486
 487     // Variant of an enum.
 488     fn format_variant(&self, field: &ast::Variant) -> Option<String> {
 489         if contains_skip(&field.node.attrs) {
 490             let lo = field.node.attrs[0].span.lo;
 491             let span = mk_sp(lo, field.span.hi);
 492             return Some(self.snippet(span));
 493         }
 494
 495         let context = self.get_context();
 496         let indent = self.block_indent;
 497         let mut result = try_opt!(
 498             field
 499                 .node
 500                 .attrs
 501                 .rewrite(&context, Shape::indented(indent, self.config))
 502         );
 503         if !result.is_empty() {
 504             let shape = Shape {
 505                 width: context.config.max_width(),
 506                 indent: self.block_indent,
 507                 offset: self.block_indent.alignment,
 508             };
 509             let missing_comment = rewrite_missing_comment_on_field(
 510                 &context,
 511                 shape,
 512                 field.node.attrs[field.node.attrs.len() - 1].span.hi,
 513                 field.span.lo,
 514                 &mut result,
 515             ).unwrap_or(String::new());
 516             result.push_str(&missing_comment);
 517         }
 518
 519         let variant_body = match field.node.data {
 520             ast::VariantData::Tuple(..) | ast::VariantData::Struct(..) => {
 521                 // FIXME: Should limit the width, as we have a trailing comma
 522                 format_struct(
 523                     &context,
 524                     "",
 525                     field.node.name,
 526                     &ast::Visibility::Inherited,
 527                     &field.node.data,
 528                     None,
 529                     field.span,
 530                     indent,
 531                     Some(self.config.struct_variant_width()),
 532                 )
 533             }
 534             ast::VariantData::Unit(..) => {
 535                 let tag = if let Some(ref expr) = field.node.disr_expr {
 536                     format!("{} = {}", field.node.name, self.snippet(expr.span))
 537                 } else {
 538                     field.node.name.to_string()
 539                 };
 540
 541                 wrap_str(
 542                     tag,
 543                     self.config.max_width(),
 544                     Shape::indented(indent, self.config),
 545                 )
 546             }
 547         };
 548
 549         if let Some(variant_str) = variant_body {
 550             result.push_str(&variant_str);
 551             Some(result)
 552         } else {
 553             None
 554         }
 555     }
 556 }
 557
 558 pub fn format_impl(
 559     context: &RewriteContext,
 560     item: &ast::Item,
 561     offset: Indent,
 562     where_span_end: Option<BytePos>,
 563 ) -> Option<String> {
 564     if let ast::ItemKind::Impl(_, _, _, ref generics, _, ref self_ty, ref items) = item.node {
 565         let mut result = String::new();
 566         let ref_and_type = try_opt!(format_impl_ref_and_type(context, item, offset));
 567         result.push_str(&ref_and_type);
 568
 569         let where_budget = if result.contains('\n') {
 570             context.config.max_width()
 571         } else {
 572             context
 573                 .config
 574                 .max_width()
 575                 .checked_sub(last_line_width(&result))
 576                 .unwrap_or(0)
 577         };
 578         let where_clause_str = try_opt!(rewrite_where_clause(
 579             context,
 580             &generics.where_clause,
 581             context.config.item_brace_style(),
 582             Shape::legacy(where_budget, offset.block_only()),
 583             context.config.where_density(),
 584             "{",
 585             false,
 586             last_line_width(&ref_and_type) == 1,
 587             where_span_end,
 588             item.span,
 589             self_ty.span.hi,
 590         ));
 591
 592         if try_opt!(is_impl_single_line(
 593             context,
 594             &items,
 595             &result,
 596             &where_clause_str,
 597             &item,
 598         )) {
 599             result.push_str(&where_clause_str);
 600             if where_clause_str.contains('\n') {
 601                 let white_space = offset.to_string(context.config);
 602                 result.push_str(&format!("\n{}{{\n{}}}", &white_space, &white_space));
 603             } else {
 604                 result.push_str(" {}");
 605             }
 606             return Some(result);
 607         }
 608
 609         if !where_clause_str.is_empty() && !where_clause_str.contains('\n') {
 610             result.push('\n');
 611             let width = offset.block_indent + context.config.tab_spaces() - 1;
 612             let where_indent = Indent::new(0, width);
 613             result.push_str(&where_indent.to_string(context.config));
 614         }
 615         result.push_str(&where_clause_str);
 616
 617         match context.config.item_brace_style() {
 618             BraceStyle::AlwaysNextLine => {
 619                 result.push('\n');
 620                 result.push_str(&offset.to_string(context.config));
 621             }
 622             BraceStyle::PreferSameLine => result.push(' '),
 623             BraceStyle::SameLineWhere => {
 624                 if !where_clause_str.is_empty() {
 625                     result.push('\n');
 626                     result.push_str(&offset.to_string(context.config));
 627                 } else {
 628                     result.push(' ');
 629                 }
 630             }
 631         }
 632
 633         result.push('{');
 634
 635         let snippet = context.snippet(item.span);
 636         let open_pos = try_opt!(snippet.find_uncommented("{")) + 1;
 637
 638         if !items.is_empty() || contains_comment(&snippet[open_pos..]) {
 639             let mut visitor = FmtVisitor::from_codemap(context.parse_session, context.config);
 640             visitor.block_indent = offset.block_only().block_indent(context.config);
 641             visitor.last_pos = item.span.lo + BytePos(open_pos as u32);
 642
 643             for item in items {
 644                 visitor.visit_impl_item(item);
 645             }
 646
 647             visitor.format_missing(item.span.hi - BytePos(1));
 648
 649             let inner_indent_str = visitor.block_indent.to_string(context.config);
 650             let outer_indent_str = offset.block_only().to_string(context.config);
 651
 652             result.push('\n');
 653             result.push_str(&inner_indent_str);
 654             result.push_str(trim_newlines(visitor.buffer.to_string().trim()));
 655             result.push('\n');
 656             result.push_str(&outer_indent_str);
 657         }
 658
 659         if result.chars().last().unwrap() == '{' {
 660             result.push('\n');
 661             result.push_str(&offset.to_string(context.config));
 662         }
 663         result.push('}');
 664
 665         Some(result)
 666     } else {
 667         unreachable!();
 668     }
 669 }
 670
 671 fn is_impl_single_line(
 672     context: &RewriteContext,
 673     items: &[ImplItem],
 674     result: &str,
 675     where_clause_str: &str,
 676     item: &ast::Item,
 677 ) -> Option<bool> {
 678     let snippet = context.snippet(item.span);
 679     let open_pos = try_opt!(snippet.find_uncommented("{")) + 1;
 680
 681     Some(
 682         context.config.impl_empty_single_line() && items.is_empty() &&
 683             result.len() + where_clause_str.len() <= context.config.max_width() &&
 684             !contains_comment(&snippet[open_pos..]),
 685     )
 686 }
 687
 688 fn format_impl_ref_and_type(
 689     context: &RewriteContext,
 690     item: &ast::Item,
 691     offset: Indent,
 692 ) -> Option<String> {
 693     if let ast::ItemKind::Impl(
 694         unsafety,
 695         polarity,
 696         _,
 697         ref generics,
 698         ref trait_ref,
 699         ref self_ty,
 700         _,
 701     ) = item.node
 702     {
 703         let mut result = String::new();
 704
 705         result.push_str(&format_visibility(&item.vis));
 706         result.push_str(format_unsafety(unsafety));
 707         result.push_str("impl");
 708
 709         let lo = context.codemap.span_after(item.span, "impl");
 710         let hi = match *trait_ref {
 711             Some(ref tr) => tr.path.span.lo,
 712             None => self_ty.span.lo,
 713         };
 714         let shape = try_opt!(generics_shape_from_config(
 715             context.config,
 716             Shape::indented(offset + last_line_width(&result), context.config),
 717             0,
 718         ));
 719         let one_line_budget = try_opt!(shape.width.checked_sub(last_line_width(&result) + 2));
 720         let generics_str = try_opt!(rewrite_generics_inner(
 721             context,
 722             generics,
 723             shape,
 724             one_line_budget,
 725             mk_sp(lo, hi),
 726         ));
 727
 728         let polarity_str = if polarity == ast::ImplPolarity::Negative {
 729             "!"
 730         } else {
 731             ""
 732         };
 733
 734         if let Some(ref trait_ref) = *trait_ref {
 735             let result_len = result.len();
 736             if let Some(trait_ref_str) = rewrite_trait_ref(
 737                 context,
 738                 &trait_ref,
 739                 offset,
 740                 &generics_str,
 741                 true,
 742                 polarity_str,
 743                 result_len,
 744             ) {
 745                 result.push_str(&trait_ref_str);
 746             } else {
 747                 let generics_str = try_opt!(rewrite_generics_inner(
 748                     context,
 749                     generics,
 750                     shape,
 751                     0,
 752                     mk_sp(lo, hi),
 753                 ));
 754                 result.push_str(&try_opt!(rewrite_trait_ref(
 755                     context,
 756                     &trait_ref,
 757                     offset,
 758                     &generics_str,
 759                     false,
 760                     polarity_str,
 761                     result_len,
 762                 )));
 763             }
 764         } else {
 765             result.push_str(&generics_str);
 766         }
 767
 768         // Try to put the self type in a single line.
 769         // ` for`
 770         let trait_ref_overhead = if trait_ref.is_some() { 4 } else { 0 };
 771         let curly_brace_overhead = if generics.where_clause.predicates.is_empty() {
 772             // If there is no where clause adapt budget for type formatting to take space and curly
 773             // brace into account.
 774             match context.config.item_brace_style() {
 775                 BraceStyle::AlwaysNextLine => 0,
 776                 _ => 2,
 777             }
 778         } else {
 779             0
 780         };
 781         let used_space = last_line_width(&result) + trait_ref_overhead + curly_brace_overhead;
 782         // 1 = space before the type.
 783         let budget = context
 784             .config
 785             .max_width()
 786             .checked_sub(used_space + 1)
 787             .unwrap_or(0);
 788         if let Some(self_ty_str) = self_ty.rewrite(context, Shape::legacy(budget, offset)) {
 789             if !self_ty_str.contains('\n') {
 790                 if trait_ref.is_some() {
 791                     result.push_str(" for ");
 792                 } else {
 793                     result.push(' ');
 794                 }
 795                 result.push_str(&self_ty_str);
 796                 return Some(result);
 797             }
 798         }
 799
 800         // Couldn't fit the self type on a single line, put it on a new line.
 801         result.push('\n');
 802         // Add indentation of one additional tab.
 803         let new_line_offset = offset.block_indent(context.config);
 804         result.push_str(&new_line_offset.to_string(context.config));
 805         if trait_ref.is_some() {
 806             result.push_str("for ");
 807         }
 808         let budget = context.config.max_width() - last_line_width(&result);
 809         let type_offset = match context.config.where_style() {
 810             Style::Legacy => new_line_offset + trait_ref_overhead,
 811             Style::Rfc => new_line_offset,
 812         };
 813         result.push_str(&*try_opt!(
 814             self_ty.rewrite(context, Shape::legacy(budget, type_offset))
 815         ));
 816         Some(result)
 817     } else {
 818         unreachable!();
 819     }
 820 }
 821
 822 fn rewrite_trait_ref(
 823     context: &RewriteContext,
 824     trait_ref: &ast::TraitRef,
 825     offset: Indent,
 826     generics_str: &str,
 827     retry: bool,
 828     polarity_str: &str,
 829     result_len: usize,
 830 ) -> Option<String> {
 831     // 1 = space between generics and trait_ref
 832     let used_space = 1 + polarity_str.len() +
 833         if generics_str.contains('\n') {
 834             last_line_width(&generics_str)
 835         } else {
 836             result_len + generics_str.len()
 837         };
 838     let shape = Shape::indented(offset + used_space, context.config);
 839     if let Some(trait_ref_str) = trait_ref.rewrite(context, shape) {
 840         if !(retry && trait_ref_str.contains('\n')) {
 841             return Some(format!(
 842                 "{} {}{}",
 843                 generics_str,
 844                 polarity_str,
 845                 &trait_ref_str
 846             ));
 847         }
 848     }
 849     // We could not make enough space for trait_ref, so put it on new line.
 850     if !retry {
 851         let offset = offset.block_indent(context.config);
 852         let shape = Shape::indented(offset, context.config);
 853         let trait_ref_str = try_opt!(trait_ref.rewrite(context, shape));
 854         Some(format!(
 855             "{}\n{}{}{}",
 856             generics_str,
 857             &offset.to_string(context.config),
 858             polarity_str,
 859             &trait_ref_str
 860         ))
 861     } else {
 862         None
 863     }
 864 }
 865
 866 pub fn format_struct(
 867     context: &RewriteContext,
 868     item_name: &str,
 869     ident: ast::Ident,
 870     vis: &ast::Visibility,
 871     struct_def: &ast::VariantData,
 872     generics: Option<&ast::Generics>,
 873     span: Span,
 874     offset: Indent,
 875     one_line_width: Option<usize>,
 876 ) -> Option<String> {
 877     match *struct_def {
 878         ast::VariantData::Unit(..) => Some(format_unit_struct(item_name, ident, vis)),
 879         ast::VariantData::Tuple(ref fields, _) => {
 880             format_tuple_struct(
 881                 context,
 882                 item_name,
 883                 ident,
 884                 vis,
 885                 fields,
 886                 generics,
 887                 span,
 888                 offset,
 889             )
 890         }
 891         ast::VariantData::Struct(ref fields, _) => {
 892             format_struct_struct(
 893                 context,
 894                 item_name,
 895                 ident,
 896                 vis,
 897                 fields,
 898                 generics,
 899                 span,
 900                 offset,
 901                 one_line_width,
 902             )
 903         }
 904     }
 905 }
 906
 907 pub fn format_trait(context: &RewriteContext, item: &ast::Item, offset: Indent) -> Option<String> {
 908     if let ast::ItemKind::Trait(unsafety, ref generics, ref type_param_bounds, ref trait_items) =
 909         item.node
 910     {
 911         let mut result = String::new();
 912         let header = format!(
 913             "{}{}trait {}",
 914             format_visibility(&item.vis),
 915             format_unsafety(unsafety),
 916             item.ident
 917         );
 918
 919         result.push_str(&header);
 920
 921         let body_lo = context.codemap.span_after(item.span, "{");
 922
 923         let shape = Shape::indented(offset + last_line_width(&result), context.config);
 924         let generics_str = try_opt!(rewrite_generics(
 925             context,
 926             generics,
 927             shape,
 928             mk_sp(item.span.lo, body_lo),
 929         ));
 930         result.push_str(&generics_str);
 931
 932         let trait_bound_str = try_opt!(rewrite_trait_bounds(
 933             context,
 934             type_param_bounds,
 935             Shape::indented(offset, context.config),
 936         ));
 937         // If the trait, generics, and trait bound cannot fit on the same line,
 938         // put the trait bounds on an indented new line
 939         if offset.width() + last_line_width(&result) + trait_bound_str.len() >
 940             context.config.comment_width()
 941         {
 942             result.push('\n');
 943             let trait_indent = offset.block_only().block_indent(context.config);
 944             result.push_str(&trait_indent.to_string(context.config));
 945         }
 946         result.push_str(&trait_bound_str);
 947
 948         let has_body = !trait_items.is_empty();
 949
 950         let where_density = if (context.config.where_density() == Density::Compressed &&
 951                                     (!result.contains('\n') ||
 952                                          context.config.fn_args_layout() == IndentStyle::Block)) ||
 953             (context.config.fn_args_layout() == IndentStyle::Block && result.is_empty()) ||
 954             (context.config.where_density() == Density::CompressedIfEmpty && !has_body &&
 955                  !result.contains('\n'))
 956         {
 957             Density::Compressed
 958         } else {
 959             Density::Tall
 960         };
 961
 962         let where_budget = try_opt!(
 963             context
 964                 .config
 965                 .max_width()
 966                 .checked_sub(last_line_width(&result))
 967         );
 968         let pos_before_where = if type_param_bounds.is_empty() {
 969             // We do not use this, so it does not matter
 970             generics.span.hi
 971         } else {
 972             type_param_bounds[type_param_bounds.len() - 1].span().hi
 973         };
 974         let where_clause_str = try_opt!(rewrite_where_clause(
 975             context,
 976             &generics.where_clause,
 977             context.config.item_brace_style(),
 978             Shape::legacy(where_budget, offset.block_only()),
 979             where_density,
 980             "{",
 981             !has_body,
 982             trait_bound_str.is_empty() && last_line_width(&generics_str) == 1,
 983             None,
 984             item.span,
 985             pos_before_where,
 986         ));
 987         // If the where clause cannot fit on the same line,
 988         // put the where clause on a new line
 989         if !where_clause_str.contains('\n') &&
 990             last_line_width(&result) + where_clause_str.len() + offset.width() >
 991                 context.config.comment_width()
 992         {
 993             result.push('\n');
 994             let width = offset.block_indent + context.config.tab_spaces() - 1;
 995             let where_indent = Indent::new(0, width);
 996             result.push_str(&where_indent.to_string(context.config));
 997         }
 998         result.push_str(&where_clause_str);
 999
1000         match context.config.item_brace_style() {
1001             BraceStyle::AlwaysNextLine => {
1002                 result.push('\n');
1003                 result.push_str(&offset.to_string(context.config));
1004             }
1005             BraceStyle::PreferSameLine => result.push(' '),
1006             BraceStyle::SameLineWhere => {
1007                 if !where_clause_str.is_empty() &&
1008                     (!trait_items.is_empty() || result.contains('\n'))
1009                 {
1010                     result.push('\n');
1011                     result.push_str(&offset.to_string(context.config));
1012                 } else {
1013                     result.push(' ');
1014                 }
1015             }
1016         }
1017         result.push('{');
1018
1019         let snippet = context.snippet(item.span);
1020         let open_pos = try_opt!(snippet.find_uncommented("{")) + 1;
1021
1022         if !trait_items.is_empty() || contains_comment(&snippet[open_pos..]) {
1023             let mut visitor = FmtVisitor::from_codemap(context.parse_session, context.config);
1024             visitor.block_indent = offset.block_only().block_indent(context.config);
1025             visitor.last_pos = item.span.lo + BytePos(open_pos as u32);
1026
1027             for item in trait_items {
1028                 visitor.visit_trait_item(item);
1029             }
1030
1031             visitor.format_missing(item.span.hi - BytePos(1));
1032
1033             let inner_indent_str = visitor.block_indent.to_string(context.config);
1034             let outer_indent_str = offset.block_only().to_string(context.config);
1035
1036             result.push('\n');
1037             result.push_str(&inner_indent_str);
1038             result.push_str(trim_newlines(visitor.buffer.to_string().trim()));
1039             result.push('\n');
1040             result.push_str(&outer_indent_str);
1041         } else if result.contains('\n') {
1042             result.push('\n');
1043         }
1044
1045         result.push('}');
1046         Some(result)
1047     } else {
1048         unreachable!();
1049     }
1050 }
1051
1052 fn format_unit_struct(item_name: &str, ident: ast::Ident, vis: &ast::Visibility) -> String {
1053     format!("{};", format_header(item_name, ident, vis))
1054 }
1055
1056 pub fn format_struct_struct(
1057     context: &RewriteContext,
1058     item_name: &str,
1059     ident: ast::Ident,
1060     vis: &ast::Visibility,
1061     fields: &[ast::StructField],
1062     generics: Option<&ast::Generics>,
1063     span: Span,
1064     offset: Indent,
1065     one_line_width: Option<usize>,
1066 ) -> Option<String> {
1067     let mut result = String::with_capacity(1024);
1068
1069     let header_str = format_header(item_name, ident, vis);
1070     result.push_str(&header_str);
1071
1072     let body_lo = context.codemap.span_after(span, "{");
1073
1074     let generics_str = match generics {
1075         Some(g) => {
1076             try_opt!(format_generics(
1077                 context,
1078                 g,
1079                 "{",
1080                 "{",
1081                 context.config.item_brace_style(),
1082                 fields.is_empty(),
1083                 offset,
1084                 mk_sp(span.lo, body_lo),
1085                 last_line_width(&result),
1086             ))
1087         }
1088         None => {
1089             // 3 = ` {}`, 2 = ` {`.
1090             let overhead = if fields.is_empty() { 3 } else { 2 };
1091             if (context.config.item_brace_style() == BraceStyle::AlwaysNextLine &&
1092                     !fields.is_empty()) ||
1093                 context
1094                     .config
1095                     .max_width()
1096                     .checked_sub(result.len())
1097                     .unwrap_or(0) < overhead
1098             {
1099                 format!("\n{}{{", offset.block_only().to_string(context.config))
1100             } else {
1101                 " {".to_owned()
1102             }
1103         }
1104     };
1105     // 1 = `}`
1106     let overhead = if fields.is_empty() { 1 } else { 0 };
1107     let max_len = context.config.max_width() - offset.width();
1108     if !generics_str.contains('\n') && result.len() + generics_str.len() + overhead > max_len {
1109         result.push('\n');
1110         result.push_str(&offset
1111             .block_indent(context.config)
1112             .to_string(context.config));
1113         result.push_str(&generics_str.trim_left());
1114     } else {
1115         result.push_str(&generics_str);
1116     }
1117
1118     if fields.is_empty() {
1119         let snippet = context.snippet(mk_sp(body_lo, span.hi - BytePos(1)));
1120         if snippet.trim().is_empty() {
1121             // `struct S {}`
1122         } else if snippet.trim_right_matches(&[' ', '\t'][..]).ends_with('\n') {
1123             // fix indent
1124             result.push_str(&snippet.trim_right());
1125             result.push('\n');
1126             result.push_str(&offset.to_string(context.config));
1127         } else {
1128             result.push_str(&snippet);
1129         }
1130         result.push('}');
1131         return Some(result);
1132     }
1133
1134     let items_str = try_opt!(rewrite_with_alignment(
1135         fields,
1136         context,
1137         Shape::indented(offset, context.config),
1138         mk_sp(body_lo, span.hi),
1139         one_line_width.unwrap_or(0),
1140     ));
1141
1142     if one_line_width.is_some() && !items_str.contains('\n') {
1143         Some(format!("{} {} }}", result, items_str))
1144     } else {
1145         Some(format!(
1146             "{}\n{}{}\n{}}}",
1147             result,
1148             offset
1149                 .block_indent(context.config)
1150                 .to_string(context.config),
1151             items_str,
1152             offset.to_string(context.config)
1153         ))
1154     }
1155 }
1156
1157 fn format_tuple_struct(
1158     context: &RewriteContext,
1159     item_name: &str,
1160     ident: ast::Ident,
1161     vis: &ast::Visibility,
1162     fields: &[ast::StructField],
1163     generics: Option<&ast::Generics>,
1164     span: Span,
1165     offset: Indent,
1166 ) -> Option<String> {
1167     let mut result = String::with_capacity(1024);
1168
1169     let header_str = format_header(item_name, ident, vis);
1170     result.push_str(&header_str);
1171
1172     let body_lo = if fields.is_empty() {
1173         context.codemap.span_after(span, "(")
1174     } else {
1175         fields[0].span.lo
1176     };
1177     let body_hi = if fields.is_empty() {
1178         context.codemap.span_after(span, ")")
1179     } else {
1180         // This is a dirty hack to work around a missing `)` from the span of the last field.
1181         let last_arg_span = fields[fields.len() - 1].span;
1182         if context.snippet(last_arg_span).ends_with(")") {
1183             last_arg_span.hi
1184         } else {
1185             context
1186                 .codemap
1187                 .span_after(mk_sp(last_arg_span.hi, span.hi), ")")
1188         }
1189     };
1190
1191     let where_clause_str = match generics {
1192         Some(generics) => {
1193             let budget = context.budget(last_line_width(&header_str));
1194             let shape = Shape::legacy(budget, offset);
1195             let g_span = mk_sp(span.lo, body_lo);
1196             let generics_str = try_opt!(rewrite_generics(context, generics, shape, g_span));
1197             result.push_str(&generics_str);
1198
1199             let where_budget = context.budget(last_line_width(&result));
1200             try_opt!(rewrite_where_clause(
1201                 context,
1202                 &generics.where_clause,
1203                 context.config.item_brace_style(),
1204                 Shape::legacy(where_budget, offset.block_only()),
1205                 Density::Compressed,
1206                 ";",
1207                 true,
1208                 false,
1209                 None,
1210                 span,
1211                 body_hi,
1212             ))
1213         }
1214         None => "".to_owned(),
1215     };
1216
1217     if fields.is_empty() {
1218         // 3 = `();`
1219         let used_width = if result.contains('\n') {
1220             last_line_width(&result) + 3
1221         } else {
1222             offset.width() + result.len() + 3
1223         };
1224         if used_width > context.config.max_width() {
1225             result.push('\n');
1226             result.push_str(&offset
1227                 .block_indent(context.config)
1228                 .to_string(context.config))
1229         }
1230         result.push('(');
1231         let snippet = context.snippet(mk_sp(body_lo, context.codemap.span_before(span, ")")));
1232         if snippet.is_empty() {
1233             // `struct S ()`
1234         } else if snippet.trim_right_matches(&[' ', '\t'][..]).ends_with('\n') {
1235             result.push_str(&snippet.trim_right());
1236             result.push('\n');
1237             result.push_str(&offset.to_string(context.config));
1238         } else {
1239             result.push_str(&snippet);
1240         }
1241         result.push(')');
1242     } else {
1243         // 3 = `();`
1244         let body = try_opt!(
1245             rewrite_call_inner(
1246                 context,
1247                 "",
1248                 &fields.iter().map(|field| field).collect::<Vec<_>>()[..],
1249                 span,
1250                 Shape::legacy(context.budget(last_line_width(&result) + 3), offset),
1251                 context.config.fn_call_width(),
1252                 false,
1253             ).ok()
1254         );
1255         result.push_str(&body);
1256     }
1257
1258     if !where_clause_str.is_empty() && !where_clause_str.contains('\n') &&
1259         (result.contains('\n') ||
1260              offset.block_indent + result.len() + where_clause_str.len() + 1 >
1261                  context.config.max_width())
1262     {
1263         // We need to put the where clause on a new line, but we didn't
1264         // know that earlier, so the where clause will not be indented properly.
1265         result.push('\n');
1266         result.push_str(&(offset.block_only() + (context.config.tab_spaces() - 1))
1267             .to_string(context.config));
1268     }
1269     result.push_str(&where_clause_str);
1270
1271     Some(result)
1272 }
1273
1274 pub fn rewrite_type_alias(
1275     context: &RewriteContext,
1276     indent: Indent,
1277     ident: ast::Ident,
1278     ty: &ast::Ty,
1279     generics: &ast::Generics,
1280     vis: &ast::Visibility,
1281     span: Span,
1282 ) -> Option<String> {
1283     let mut result = String::new();
1284
1285     result.push_str(&format_visibility(vis));
1286     result.push_str("type ");
1287     result.push_str(&ident.to_string());
1288
1289     // 2 = `= `
1290     let shape = try_opt!(Shape::indented(indent + result.len(), context.config).sub_width(2));
1291     let g_span = mk_sp(context.codemap.span_after(span, "type"), ty.span.lo);
1292     let generics_str = try_opt!(rewrite_generics(context, generics, shape, g_span));
1293     result.push_str(&generics_str);
1294
1295     let where_budget = try_opt!(
1296         context
1297             .config
1298             .max_width()
1299             .checked_sub(last_line_width(&result))
1300     );
1301     let where_clause_str = try_opt!(rewrite_where_clause(
1302         context,
1303         &generics.where_clause,
1304         context.config.item_brace_style(),
1305         Shape::legacy(where_budget, indent),
1306         context.config.where_density(),
1307         "=",
1308         true,
1309         true,
1310         Some(span.hi),
1311         span,
1312         generics.span.hi,
1313     ));
1314     result.push_str(&where_clause_str);
1315     result.push_str(" = ");
1316
1317     let line_width = last_line_width(&result);
1318     // This checked_sub may fail as the extra space after '=' is not taken into account
1319     // In that case the budget is set to 0 which will make ty.rewrite retry on a new line
1320     let budget = context
1321         .config
1322         .max_width()
1323         .checked_sub(indent.width() + line_width + ";".len())
1324         .unwrap_or(0);
1325     let type_indent = indent + line_width;
1326     // Try to fit the type on the same line
1327     let ty_str = try_opt!(
1328         ty.rewrite(context, Shape::legacy(budget, type_indent))
1329             .or_else(|| {
1330                 // The line was too short, try to put the type on the next line
1331
1332                 // Remove the space after '='
1333                 result.pop();
1334                 let type_indent = indent.block_indent(context.config);
1335                 result.push('\n');
1336                 result.push_str(&type_indent.to_string(context.config));
1337                 let budget = try_opt!(
1338                     context
1339                         .config
1340                         .max_width()
1341                         .checked_sub(type_indent.width() + ";".len())
1342                 );
1343                 ty.rewrite(context, Shape::legacy(budget, type_indent))
1344             })
1345     );
1346     result.push_str(&ty_str);
1347     result.push_str(";");
1348     Some(result)
1349 }
1350
1351 fn type_annotation_spacing(config: &Config) -> (&str, &str) {
1352     (
1353         if config.space_before_type_annotation() {
1354             " "
1355         } else {
1356             ""
1357         },
1358         if config.space_after_type_annotation_colon() {
1359             " "
1360         } else {
1361             ""
1362         },
1363     )
1364 }
1365
1366 fn rewrite_missing_comment_on_field(
1367     context: &RewriteContext,
1368     shape: Shape,
1369     lo: BytePos,
1370     hi: BytePos,
1371     result: &mut String,
1372 ) -> Option<String> {
1373     let possibly_comment_snippet = context.snippet(mk_sp(lo, hi));
1374     let newline_index = possibly_comment_snippet.find('\n');
1375     let comment_index = possibly_comment_snippet.find('/');
1376     match (newline_index, comment_index) {
1377         (Some(i), Some(j)) if i > j => result.push(' '),
1378         _ => {
1379             result.push('\n');
1380             result.push_str(&shape.indent.to_string(context.config));
1381         }
1382     }
1383     let trimmed = possibly_comment_snippet.trim();
1384     if trimmed.is_empty() {
1385         None
1386     } else {
1387         rewrite_comment(trimmed, false, shape, context.config).map(|s| {
1388             format!("{}\n{}", s, shape.indent.to_string(context.config))
1389         })
1390     }
1391 }
1392
1393 pub fn rewrite_struct_field_prefix(
1394     context: &RewriteContext,
1395     field: &ast::StructField,
1396     shape: Shape,
1397 ) -> Option<String> {
1398     let vis = format_visibility(&field.vis);
1399     let mut attr_str = try_opt!(
1400         field
1401             .attrs
1402             .rewrite(context, Shape::indented(shape.indent, context.config))
1403     );
1404     // Try format missing comments after attributes
1405     let missing_comment = if !field.attrs.is_empty() {
1406         rewrite_missing_comment_on_field(
1407             context,
1408             shape,
1409             field.attrs[field.attrs.len() - 1].span.hi,
1410             field.span.lo,
1411             &mut attr_str,
1412         ).unwrap_or(String::new())
1413     } else {
1414         String::new()
1415     };
1416
1417     let type_annotation_spacing = type_annotation_spacing(context.config);
1418     Some(match field.ident {
1419         Some(name) => {
1420             format!(
1421                 "{}{}{}{}{}:",
1422                 attr_str,
1423                 missing_comment,
1424                 vis,
1425                 name,
1426                 type_annotation_spacing.0
1427             )
1428         }
1429         None => format!("{}{}{}", attr_str, missing_comment, vis),
1430     })
1431 }
1432
1433 fn rewrite_struct_field_type(
1434     context: &RewriteContext,
1435     last_line_width: usize,
1436     field: &ast::StructField,
1437     spacing: &str,
1438     shape: Shape,
1439 ) -> Option<String> {
1440     let ty_shape = try_opt!(shape.offset_left(last_line_width + spacing.len()));
1441     field
1442         .ty
1443         .rewrite(context, ty_shape)
1444         .map(|ty| format!("{}{}", spacing, ty))
1445 }
1446
1447 impl Rewrite for ast::StructField {
1448     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
1449         rewrite_struct_field(context, self, shape, 0)
1450     }
1451 }
1452
1453 pub fn rewrite_struct_field(
1454     context: &RewriteContext,
1455     field: &ast::StructField,
1456     shape: Shape,
1457     lhs_max_width: usize,
1458 ) -> Option<String> {
1459     if contains_skip(&field.attrs) {
1460         let span = context.snippet(mk_sp(field.attrs[0].span.lo, field.span.hi));
1461         return wrap_str(span, context.config.max_width(), shape);
1462     }
1463
1464     let type_annotation_spacing = type_annotation_spacing(context.config);
1465     let prefix = try_opt!(rewrite_struct_field_prefix(context, field, shape));
1466
1467     // Try to put everything on a single line.
1468     let last_line_width = last_line_width(&prefix);
1469     let mut spacing = String::from(if field.ident.is_some() {
1470         type_annotation_spacing.1
1471     } else {
1472         ""
1473     });
1474     let lhs_offset = lhs_max_width.checked_sub(last_line_width).unwrap_or(0);
1475     for _ in 0..lhs_offset {
1476         spacing.push(' ');
1477     }
1478     let ty_rewritten = rewrite_struct_field_type(context, last_line_width, field, &spacing, shape);
1479     if let Some(ref ty) = ty_rewritten {
1480         if !ty.contains('\n') {
1481             return Some(prefix + &ty);
1482         }
1483     }
1484
1485     // We must use multiline.
1486     let type_offset = shape.indent.block_indent(context.config);
1487     let rewrite_type_in_next_line = || {
1488         field
1489             .ty
1490             .rewrite(context, Shape::indented(type_offset, context.config))
1491     };
1492
1493     match ty_rewritten {
1494         // If we start from the next line and type fits in a single line, then do so.
1495         Some(ref ty) => {
1496             match rewrite_type_in_next_line() {
1497                 Some(ref new_ty) if !new_ty.contains('\n') => {
1498                     Some(format!(
1499                         "{}\n{}{}",
1500                         prefix,
1501                         type_offset.to_string(&context.config),
1502                         &new_ty
1503                     ))
1504                 }
1505                 _ => Some(prefix + &ty),
1506             }
1507         }
1508         _ => {
1509             let ty = try_opt!(rewrite_type_in_next_line());
1510             Some(format!(
1511                 "{}\n{}{}",
1512                 prefix,
1513                 type_offset.to_string(&context.config),
1514                 &ty
1515             ))
1516         }
1517     }
1518 }
1519
1520 pub fn rewrite_static(
1521     prefix: &str,
1522     vis: &ast::Visibility,
1523     ident: ast::Ident,
1524     ty: &ast::Ty,
1525     mutability: ast::Mutability,
1526     expr_opt: Option<&ptr::P<ast::Expr>>,
1527     offset: Indent,
1528     span: Span,
1529     context: &RewriteContext,
1530 ) -> Option<String> {
1531     let colon = colon_spaces(
1532         context.config.space_before_type_annotation(),
1533         context.config.space_after_type_annotation_colon(),
1534     );
1535     let prefix = format!(
1536         "{}{} {}{}{}",
1537         format_visibility(vis),
1538         prefix,
1539         format_mutability(mutability),
1540         ident,
1541         colon,
1542     );
1543     // 2 = " =".len()
1544     let ty_str = try_opt!(ty.rewrite(
1545         context,
1546         try_opt!(
1547             Shape::indented(offset.block_only(), context.config).offset_left(prefix.len() + 2)
1548         ),
1549     ));
1550
1551     if let Some(expr) = expr_opt {
1552         let lhs = format!("{}{} =", prefix, ty_str);
1553         // 1 = ;
1554         let remaining_width = context.config.max_width() - offset.block_indent - 1;
1555         rewrite_assign_rhs(
1556             context,
1557             lhs,
1558             expr,
1559             Shape::legacy(remaining_width, offset.block_only()),
1560         ).and_then(|res| {
1561             recover_comment_removed(res, span, context, Shape::indented(offset, context.config))
1562         })
1563             .map(|s| if s.ends_with(';') { s } else { s + ";" })
1564     } else {
1565         Some(format!("{}{};", prefix, ty_str))
1566     }
1567 }
1568
1569 pub fn rewrite_associated_type(
1570     ident: ast::Ident,
1571     ty_opt: Option<&ptr::P<ast::Ty>>,
1572     ty_param_bounds_opt: Option<&ast::TyParamBounds>,
1573     context: &RewriteContext,
1574     indent: Indent,
1575 ) -> Option<String> {
1576     let prefix = format!("type {}", ident);
1577
1578     let type_bounds_str = if let Some(ty_param_bounds) = ty_param_bounds_opt {
1579         let shape = Shape::indented(indent, context.config);
1580         let bounds: &[_] = ty_param_bounds;
1581         let bound_str = try_opt!(
1582             bounds
1583                 .iter()
1584                 .map(|ty_bound| ty_bound.rewrite(context, shape))
1585                 .collect::<Option<Vec<_>>>()
1586         );
1587         if bounds.len() > 0 {
1588             format!(": {}", join_bounds(context, shape, &bound_str))
1589         } else {
1590             String::new()
1591         }
1592     } else {
1593         String::new()
1594     };
1595
1596     if let Some(ty) = ty_opt {
1597         let ty_str = try_opt!(ty.rewrite(
1598             context,
1599             Shape::legacy(
1600                 context.config.max_width() - indent.block_indent - prefix.len() - 2,
1601                 indent.block_only(),
1602             ),
1603         ));
1604         Some(format!("{} = {};", prefix, ty_str))
1605     } else {
1606         Some(format!("{}{};", prefix, type_bounds_str))
1607     }
1608 }
1609
1610 pub fn rewrite_associated_impl_type(
1611     ident: ast::Ident,
1612     defaultness: ast::Defaultness,
1613     ty_opt: Option<&ptr::P<ast::Ty>>,
1614     ty_param_bounds_opt: Option<&ast::TyParamBounds>,
1615     context: &RewriteContext,
1616     indent: Indent,
1617 ) -> Option<String> {
1618     let result = try_opt!(rewrite_associated_type(
1619         ident,
1620         ty_opt,
1621         ty_param_bounds_opt,
1622         context,
1623         indent,
1624     ));
1625
1626     match defaultness {
1627         ast::Defaultness::Default => Some(format!("default {}", result)),
1628         _ => Some(result),
1629     }
1630 }
1631
1632 impl Rewrite for ast::FunctionRetTy {
1633     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
1634         match *self {
1635             ast::FunctionRetTy::Default(_) => Some(String::new()),
1636             ast::FunctionRetTy::Ty(ref ty) => {
1637                 let inner_width = try_opt!(shape.width.checked_sub(3));
1638                 ty.rewrite(context, Shape::legacy(inner_width, shape.indent + 3))
1639                     .map(|r| format!("-> {}", r))
1640             }
1641         }
1642     }
1643 }
1644
1645 fn is_empty_infer(context: &RewriteContext, ty: &ast::Ty) -> bool {
1646     match ty.node {
1647         ast::TyKind::Infer => {
1648             let original = context.snippet(ty.span);
1649             original != "_"
1650         }
1651         _ => false,
1652     }
1653 }
1654
1655 impl Rewrite for ast::Arg {
1656     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
1657         if is_named_arg(self) {
1658             let mut result = try_opt!(
1659                 self.pat
1660                     .rewrite(context, Shape::legacy(shape.width, shape.indent))
1661             );
1662
1663             if !is_empty_infer(context, &*self.ty) {
1664                 if context.config.space_before_type_annotation() {
1665                     result.push_str(" ");
1666                 }
1667                 result.push_str(":");
1668                 if context.config.space_after_type_annotation_colon() {
1669                     result.push_str(" ");
1670                 }
1671                 let max_width = try_opt!(shape.width.checked_sub(result.len()));
1672                 let ty_str = try_opt!(self.ty.rewrite(
1673                     context,
1674                     Shape::legacy(max_width, shape.indent + result.len()),
1675                 ));
1676                 result.push_str(&ty_str);
1677             }
1678
1679             Some(result)
1680         } else {
1681             self.ty.rewrite(context, shape)
1682         }
1683     }
1684 }
1685
1686 fn rewrite_explicit_self(
1687     explicit_self: &ast::ExplicitSelf,
1688     args: &[ast::Arg],
1689     context: &RewriteContext,
1690 ) -> Option<String> {
1691     match explicit_self.node {
1692         ast::SelfKind::Region(lt, m) => {
1693             let mut_str = format_mutability(m);
1694             match lt {
1695                 Some(ref l) => {
1696                     let lifetime_str = try_opt!(l.rewrite(
1697                         context,
1698                         Shape::legacy(context.config.max_width(), Indent::empty()),
1699                     ));
1700                     Some(format!("&{} {}self", lifetime_str, mut_str))
1701                 }
1702                 None => Some(format!("&{}self", mut_str)),
1703             }
1704         }
1705         ast::SelfKind::Explicit(ref ty, _) => {
1706             assert!(!args.is_empty(), "&[ast::Arg] shouldn't be empty.");
1707
1708             let mutability = explicit_self_mutability(&args[0]);
1709             let type_str = try_opt!(ty.rewrite(
1710                 context,
1711                 Shape::legacy(context.config.max_width(), Indent::empty()),
1712             ));
1713
1714             Some(format!(
1715                 "{}self: {}",
1716                 format_mutability(mutability),
1717                 type_str
1718             ))
1719         }
1720         ast::SelfKind::Value(_) => {
1721             assert!(!args.is_empty(), "&[ast::Arg] shouldn't be empty.");
1722
1723             let mutability = explicit_self_mutability(&args[0]);
1724
1725             Some(format!("{}self", format_mutability(mutability)))
1726         }
1727     }
1728 }
1729
1730 // Hacky solution caused by absence of `Mutability` in `SelfValue` and
1731 // `SelfExplicit` variants of `ast::ExplicitSelf_`.
1732 fn explicit_self_mutability(arg: &ast::Arg) -> ast::Mutability {
1733     if let ast::PatKind::Ident(ast::BindingMode::ByValue(mutability), _, _) = arg.pat.node {
1734         mutability
1735     } else {
1736         unreachable!()
1737     }
1738 }
1739
1740 pub fn span_lo_for_arg(arg: &ast::Arg) -> BytePos {
1741     if is_named_arg(arg) {
1742         arg.pat.span.lo
1743     } else {
1744         arg.ty.span.lo
1745     }
1746 }
1747
1748 pub fn span_hi_for_arg(context: &RewriteContext, arg: &ast::Arg) -> BytePos {
1749     match arg.ty.node {
1750         ast::TyKind::Infer if context.snippet(arg.ty.span) == "_" => arg.ty.span.hi,
1751         ast::TyKind::Infer if is_named_arg(arg) => arg.pat.span.hi,
1752         _ => arg.ty.span.hi,
1753     }
1754 }
1755
1756 pub fn is_named_arg(arg: &ast::Arg) -> bool {
1757     if let ast::PatKind::Ident(_, ident, _) = arg.pat.node {
1758         ident.node != symbol::keywords::Invalid.ident()
1759     } else {
1760         true
1761     }
1762 }
1763
1764 // Return type is (result, force_new_line_for_brace)
1765 fn rewrite_fn_base(
1766     context: &RewriteContext,
1767     indent: Indent,
1768     ident: ast::Ident,
1769     fd: &ast::FnDecl,
1770     generics: &ast::Generics,
1771     unsafety: ast::Unsafety,
1772     constness: ast::Constness,
1773     defaultness: ast::Defaultness,
1774     abi: abi::Abi,
1775     vis: &ast::Visibility,
1776     span: Span,
1777     newline_brace: bool,
1778     has_body: bool,
1779     has_braces: bool,
1780 ) -> Option<(String, bool)> {
1781     let mut force_new_line_for_brace = false;
1782
1783     let where_clause = &generics.where_clause;
1784
1785     let mut result = String::with_capacity(1024);
1786     // Vis unsafety abi.
1787     result.push_str(&*format_visibility(vis));
1788
1789     if let ast::Defaultness::Default = defaultness {
1790         result.push_str("default ");
1791     }
1792
1793     if let ast::Constness::Const = constness {
1794         result.push_str("const ");
1795     }
1796
1797     result.push_str(::utils::format_unsafety(unsafety));
1798
1799     if abi != abi::Abi::Rust {
1800         result.push_str(&::utils::format_abi(
1801             abi,
1802             context.config.force_explicit_abi(),
1803         ));
1804     }
1805
1806     // fn foo
1807     result.push_str("fn ");
1808     result.push_str(&ident.to_string());
1809
1810     // Generics.
1811     let overhead = if has_braces && !newline_brace {
1812         // 4 = `() {`
1813         4
1814     } else {
1815         // 2 = `()`
1816         2
1817     };
1818     let shape = try_opt!(
1819         Shape::indented(indent + last_line_width(&result), context.config).sub_width(overhead)
1820     );
1821     let g_span = mk_sp(span.lo, fd.output.span().lo);
1822     let generics_str = try_opt!(rewrite_generics(context, generics, shape, g_span));
1823     result.push_str(&generics_str);
1824
1825     let snuggle_angle_bracket = generics_str
1826         .lines()
1827         .last()
1828         .map_or(false, |l| l.trim_left().len() == 1);
1829
1830     // Note that the width and indent don't really matter, we'll re-layout the
1831     // return type later anyway.
1832     let ret_str = try_opt!(
1833         fd.output
1834             .rewrite(&context, Shape::indented(indent, context.config))
1835     );
1836
1837     let multi_line_ret_str = ret_str.contains('\n');
1838     let ret_str_len = if multi_line_ret_str { 0 } else { ret_str.len() };
1839
1840     // Args.
1841     let (mut one_line_budget, mut multi_line_budget, mut arg_indent) =
1842         try_opt!(compute_budgets_for_args(
1843             context,
1844             &result,
1845             indent,
1846             ret_str_len,
1847             newline_brace,
1848             has_braces,
1849         ));
1850
1851     if context.config.fn_args_layout() == IndentStyle::Block {
1852         arg_indent = indent.block_indent(context.config);
1853         // 1 = ","
1854         multi_line_budget = context.config.max_width() - (arg_indent.width() + 1);
1855     }
1856
1857     debug!(
1858         "rewrite_fn_base: one_line_budget: {}, multi_line_budget: {}, arg_indent: {:?}",
1859         one_line_budget,
1860         multi_line_budget,
1861         arg_indent
1862     );
1863
1864     // Check if vertical layout was forced.
1865     if one_line_budget == 0 {
1866         if snuggle_angle_bracket {
1867             result.push('(');
1868         } else {
1869             if context.config.fn_args_paren_newline() {
1870                 result.push('\n');
1871                 result.push_str(&arg_indent.to_string(context.config));
1872                 if context.config.fn_args_layout() == IndentStyle::Visual {
1873                     arg_indent = arg_indent + 1; // extra space for `(`
1874                 }
1875                 result.push('(');
1876             } else {
1877                 result.push_str("(");
1878                 if context.config.fn_args_layout() == IndentStyle::Visual {
1879                     result.push('\n');
1880                     result.push_str(&arg_indent.to_string(context.config));
1881                 }
1882             }
1883         }
1884     } else {
1885         result.push('(');
1886     }
1887     if context.config.spaces_within_parens() && fd.inputs.len() > 0 && result.ends_with('(') {
1888         result.push(' ')
1889     }
1890
1891     if multi_line_ret_str {
1892         one_line_budget = 0;
1893     }
1894
1895     // A conservative estimation, to goal is to be over all parens in generics
1896     let args_start = generics
1897         .ty_params
1898         .last()
1899         .map_or(span.lo, |tp| end_typaram(tp));
1900     let args_end = if fd.inputs.is_empty() {
1901         context.codemap.span_after(mk_sp(args_start, span.hi), ")")
1902     } else {
1903         let last_span = mk_sp(fd.inputs[fd.inputs.len() - 1].span().hi, span.hi);
1904         context.codemap.span_after(last_span, ")")
1905     };
1906     let args_span = mk_sp(
1907         context.codemap.span_after(mk_sp(args_start, span.hi), "("),
1908         args_end,
1909     );
1910     let arg_str = try_opt!(rewrite_args(
1911         context,
1912         &fd.inputs,
1913         fd.get_self().as_ref(),
1914         one_line_budget,
1915         multi_line_budget,
1916         indent,
1917         arg_indent,
1918         args_span,
1919         fd.variadic,
1920         generics_str.contains('\n'),
1921     ));
1922
1923     let multi_line_arg_str =
1924         arg_str.contains('\n') || arg_str.chars().last().map_or(false, |c| c == ',');
1925
1926     let put_args_in_block = match context.config.fn_args_layout() {
1927         IndentStyle::Block => multi_line_arg_str || generics_str.contains('\n'),
1928         _ => false,
1929     } && !fd.inputs.is_empty();
1930
1931     let mut args_last_line_contains_comment = false;
1932     if put_args_in_block {
1933         arg_indent = indent.block_indent(context.config);
1934         result.push('\n');
1935         result.push_str(&arg_indent.to_string(context.config));
1936         result.push_str(&arg_str);
1937         result.push('\n');
1938         result.push_str(&indent.to_string(context.config));
1939         result.push(')');
1940     } else {
1941         result.push_str(&arg_str);
1942         if context.config.spaces_within_parens() && fd.inputs.len() > 0 {
1943             result.push(' ')
1944         }
1945         // If the last line of args contains comment, we cannot put the closing paren
1946         // on the same line.
1947         if arg_str
1948             .lines()
1949             .last()
1950             .map_or(false, |last_line| last_line.contains("//"))
1951         {
1952             args_last_line_contains_comment = true;
1953             result.push('\n');
1954             result.push_str(&arg_indent.to_string(context.config));
1955         }
1956         result.push(')');
1957     }
1958
1959     // Return type.
1960     if !ret_str.is_empty() {
1961         let ret_should_indent = match context.config.fn_args_layout() {
1962             // If our args are block layout then we surely must have space.
1963             IndentStyle::Block if put_args_in_block => false,
1964             _ => {
1965                 // If we've already gone multi-line, or the return type would push over the max
1966                 // width, then put the return type on a new line. With the +1 for the signature
1967                 // length an additional space between the closing parenthesis of the argument and
1968                 // the arrow '->' is considered.
1969                 let mut sig_length = result.len() + indent.width() + ret_str_len + 1;
1970
1971                 // If there is no where clause, take into account the space after the return type
1972                 // and the brace.
1973                 if where_clause.predicates.is_empty() {
1974                     sig_length += 2;
1975                 }
1976
1977                 let overlong_sig = sig_length > context.config.max_width();
1978
1979                 (!args_last_line_contains_comment) &&
1980                     (result.contains('\n') || multi_line_ret_str || overlong_sig)
1981             }
1982         };
1983         let ret_indent = if ret_should_indent {
1984             let indent = match context.config.fn_return_indent() {
1985                 ReturnIndent::WithWhereClause => indent + 4,
1986                 // Aligning with non-existent args looks silly.
1987                 _ if arg_str.is_empty() => {
1988                     force_new_line_for_brace = true;
1989                     indent + 4
1990                 }
1991                 // FIXME: we might want to check that using the arg indent
1992                 // doesn't blow our budget, and if it does, then fallback to
1993                 // the where clause indent.
1994                 _ => arg_indent,
1995             };
1996
1997             result.push('\n');
1998             result.push_str(&indent.to_string(context.config));
1999             indent
2000         } else {
2001             result.push(' ');
2002             Indent::new(indent.block_indent, last_line_width(&result))
2003         };
2004
2005         if multi_line_ret_str || ret_should_indent {
2006             // Now that we know the proper indent and width, we need to
2007             // re-layout the return type.
2008             let ret_str = try_opt!(
2009                 fd.output
2010                     .rewrite(context, Shape::indented(ret_indent, context.config))
2011             );
2012             result.push_str(&ret_str);
2013         } else {
2014             result.push_str(&ret_str);
2015         }
2016
2017         // Comment between return type and the end of the decl.
2018         let snippet_lo = fd.output.span().hi;
2019         if where_clause.predicates.is_empty() {
2020             let snippet_hi = span.hi;
2021             let snippet = context.snippet(mk_sp(snippet_lo, snippet_hi));
2022             // Try to preserve the layout of the original snippet.
2023             let original_starts_with_newline = snippet
2024                 .find(|c| c != ' ')
2025                 .map_or(false, |i| snippet[i..].starts_with('\n'));
2026             let original_ends_with_newline = snippet
2027                 .rfind(|c| c != ' ')
2028                 .map_or(false, |i| snippet[i..].ends_with('\n'));
2029             let snippet = snippet.trim();
2030             if !snippet.is_empty() {
2031                 result.push(if original_starts_with_newline {
2032                     '\n'
2033                 } else {
2034                     ' '
2035                 });
2036                 result.push_str(snippet);
2037                 if original_ends_with_newline {
2038                     force_new_line_for_brace = true;
2039                 }
2040             }
2041         } else {
2042             // FIXME it would be nice to catch comments between the return type
2043             // and the where clause, but we don't have a span for the where
2044             // clause.
2045         }
2046     }
2047
2048     let should_compress_where = match context.config.where_density() {
2049         Density::Compressed => !result.contains('\n') || put_args_in_block,
2050         Density::CompressedIfEmpty => !has_body && !result.contains('\n'),
2051         _ => false,
2052     } || (put_args_in_block && ret_str.is_empty());
2053
2054     let pos_before_where = match fd.output {
2055         ast::FunctionRetTy::Default(..) => args_span.hi,
2056         ast::FunctionRetTy::Ty(ref ty) => ty.span.hi,
2057     };
2058     if where_clause.predicates.len() == 1 && should_compress_where {
2059         let budget = try_opt!(
2060             context
2061                 .config
2062                 .max_width()
2063                 .checked_sub(last_line_width(&result))
2064         );
2065         if let Some(where_clause_str) = rewrite_where_clause(
2066             context,
2067             where_clause,
2068             context.config.fn_brace_style(),
2069             Shape::legacy(budget, indent),
2070             Density::Compressed,
2071             "{",
2072             !has_braces,
2073             put_args_in_block && ret_str.is_empty(),
2074             Some(span.hi),
2075             span,
2076             pos_before_where,
2077         ) {
2078             if !where_clause_str.contains('\n') {
2079                 if last_line_width(&result) + where_clause_str.len() > context.config.max_width() {
2080                     result.push('\n');
2081                 }
2082
2083                 result.push_str(&where_clause_str);
2084
2085                 force_new_line_for_brace |= last_line_contains_single_line_comment(&result);
2086                 return Some((result, force_new_line_for_brace));
2087             }
2088         }
2089     }
2090
2091     let where_clause_str = try_opt!(rewrite_where_clause(
2092         context,
2093         where_clause,
2094         context.config.fn_brace_style(),
2095         Shape::indented(indent, context.config),
2096         Density::Tall,
2097         "{",
2098         !has_braces,
2099         put_args_in_block && ret_str.is_empty(),
2100         Some(span.hi),
2101         span,
2102         pos_before_where,
2103     ));
2104
2105     result.push_str(&where_clause_str);
2106
2107     force_new_line_for_brace |= last_line_contains_single_line_comment(&result);
2108     return Some((result, force_new_line_for_brace));
2109 }
2110
2111 fn last_line_contains_single_line_comment(s: &str) -> bool {
2112     s.lines().last().map_or(false, |l| l.contains("//"))
2113 }
2114
2115 fn rewrite_args(
2116     context: &RewriteContext,
2117     args: &[ast::Arg],
2118     explicit_self: Option<&ast::ExplicitSelf>,
2119     one_line_budget: usize,
2120     multi_line_budget: usize,
2121     indent: Indent,
2122     arg_indent: Indent,
2123     span: Span,
2124     variadic: bool,
2125     generics_str_contains_newline: bool,
2126 ) -> Option<String> {
2127     let mut arg_item_strs = try_opt!(
2128         args.iter()
2129             .map(|arg| {
2130                 arg.rewrite(&context, Shape::legacy(multi_line_budget, arg_indent))
2131             })
2132             .collect::<Option<Vec<_>>>()
2133     );
2134
2135     // Account for sugary self.
2136     // FIXME: the comment for the self argument is dropped. This is blocked
2137     // on rust issue #27522.
2138     let min_args = explicit_self
2139         .and_then(|explicit_self| {
2140             rewrite_explicit_self(explicit_self, args, context)
2141         })
2142         .map_or(1, |self_str| {
2143             arg_item_strs[0] = self_str;
2144             2
2145         });
2146
2147     // Comments between args.
2148     let mut arg_items = Vec::new();
2149     if min_args == 2 {
2150         arg_items.push(ListItem::from_str(""));
2151     }
2152
2153     // FIXME(#21): if there are no args, there might still be a comment, but
2154     // without spans for the comment or parens, there is no chance of
2155     // getting it right. You also don't get to put a comment on self, unless
2156     // it is explicit.
2157     if args.len() >= min_args || variadic {
2158         let comment_span_start = if min_args == 2 {
2159             let second_arg_start = if arg_has_pattern(&args[1]) {
2160                 args[1].pat.span.lo
2161             } else {
2162                 args[1].ty.span.lo
2163             };
2164             let reduced_span = mk_sp(span.lo, second_arg_start);
2165
2166             context.codemap.span_after_last(reduced_span, ",")
2167         } else {
2168             span.lo
2169         };
2170
2171         enum ArgumentKind<'a> {
2172             Regular(&'a ast::Arg),
2173             Variadic(BytePos),
2174         }
2175
2176         let variadic_arg = if variadic {
2177             let variadic_span = mk_sp(args.last().unwrap().ty.span.hi, span.hi);
2178             let variadic_start = context.codemap.span_after(variadic_span, "...") - BytePos(3);
2179             Some(ArgumentKind::Variadic(variadic_start))
2180         } else {
2181             None
2182         };
2183
2184         let more_items = itemize_list(
2185             context.codemap,
2186             args[min_args - 1..]
2187                 .iter()
2188                 .map(ArgumentKind::Regular)
2189                 .chain(variadic_arg),
2190             ")",
2191             |arg| match *arg {
2192                 ArgumentKind::Regular(arg) => span_lo_for_arg(arg),
2193                 ArgumentKind::Variadic(start) => start,
2194             },
2195             |arg| match *arg {
2196                 ArgumentKind::Regular(arg) => arg.ty.span.hi,
2197                 ArgumentKind::Variadic(start) => start + BytePos(3),
2198             },
2199             |arg| match *arg {
2200                 ArgumentKind::Regular(..) => None,
2201                 ArgumentKind::Variadic(..) => Some("...".to_owned()),
2202             },
2203             comment_span_start,
2204             span.hi,
2205         );
2206
2207         arg_items.extend(more_items);
2208     }
2209
2210     let fits_in_one_line = !generics_str_contains_newline &&
2211         (arg_items.len() == 0 || arg_items.len() == 1 && arg_item_strs[0].len() <= one_line_budget);
2212
2213     for (item, arg) in arg_items.iter_mut().zip(arg_item_strs) {
2214         item.item = Some(arg);
2215     }
2216
2217     let last_line_ends_with_comment = arg_items
2218         .iter()
2219         .last()
2220         .and_then(|item| item.post_comment.as_ref())
2221         .map_or(false, |s| s.trim().starts_with("//"));
2222
2223     let (indent, trailing_comma, end_with_newline) = match context.config.fn_args_layout() {
2224         IndentStyle::Block if fits_in_one_line => {
2225             (
2226                 indent.block_indent(context.config),
2227                 SeparatorTactic::Never,
2228                 true,
2229             )
2230         }
2231         IndentStyle::Block => {
2232             (
2233                 indent.block_indent(context.config),
2234                 context.config.trailing_comma(),
2235                 true,
2236             )
2237         }
2238         IndentStyle::Visual if last_line_ends_with_comment => {
2239             (arg_indent, context.config.trailing_comma(), true)
2240         }
2241         IndentStyle::Visual => (arg_indent, SeparatorTactic::Never, false),
2242     };
2243
2244     let tactic = definitive_tactic(
2245         &arg_items,
2246         context.config.fn_args_density().to_list_tactic(),
2247         one_line_budget,
2248     );
2249     let budget = match tactic {
2250         DefinitiveListTactic::Horizontal => one_line_budget,
2251         _ => multi_line_budget,
2252     };
2253
2254     debug!("rewrite_args: budget: {}, tactic: {:?}", budget, tactic);
2255
2256     let fmt = ListFormatting {
2257         tactic: tactic,
2258         separator: ",",
2259         trailing_separator: if variadic {
2260             SeparatorTactic::Never
2261         } else {
2262             trailing_comma
2263         },
2264         shape: Shape::legacy(budget, indent),
2265         ends_with_newline: end_with_newline,
2266         config: context.config,
2267     };
2268
2269     write_list(&arg_items, &fmt)
2270 }
2271
2272 fn arg_has_pattern(arg: &ast::Arg) -> bool {
2273     if let ast::PatKind::Ident(_, ident, _) = arg.pat.node {
2274         ident.node != symbol::keywords::Invalid.ident()
2275     } else {
2276         true
2277     }
2278 }
2279
2280 fn compute_budgets_for_args(
2281     context: &RewriteContext,
2282     result: &str,
2283     indent: Indent,
2284     ret_str_len: usize,
2285     newline_brace: bool,
2286     has_braces: bool,
2287 ) -> Option<((usize, usize, Indent))> {
2288     debug!(
2289         "compute_budgets_for_args {} {:?}, {}, {}",
2290         result.len(),
2291         indent,
2292         ret_str_len,
2293         newline_brace
2294     );
2295     // Try keeping everything on the same line.
2296     if !result.contains('\n') {
2297         // 2 = `()`, 3 = `() `, space is before ret_string.
2298         let overhead = if ret_str_len == 0 { 2 } else { 3 };
2299         let mut used_space = indent.width() + result.len() + ret_str_len + overhead;
2300         if has_braces {
2301             if !newline_brace {
2302                 // 2 = `{}`
2303                 used_space += 2;
2304             }
2305         } else {
2306             // 1 = `;`
2307             used_space += 1;
2308         }
2309         let one_line_budget = context
2310             .config
2311             .max_width()
2312             .checked_sub(used_space)
2313             .unwrap_or(0);
2314
2315         if one_line_budget > 0 {
2316             // 4 = "() {".len()
2317             let multi_line_overhead =
2318                 indent.width() + result.len() + if newline_brace { 2 } else { 4 };
2319             let multi_line_budget =
2320                 try_opt!(context.config.max_width().checked_sub(multi_line_overhead));
2321
2322             return Some((
2323                 one_line_budget,
2324                 multi_line_budget,
2325                 indent + result.len() + 1,
2326             ));
2327         }
2328     }
2329
2330     // Didn't work. we must force vertical layout and put args on a newline.
2331     let new_indent = indent.block_indent(context.config);
2332     // Account for `)` and possibly ` {`.
2333     let used_space = new_indent.width() + if ret_str_len == 0 { 1 } else { 3 };
2334     let max_space = try_opt!(context.config.max_width().checked_sub(used_space));
2335     Some((0, max_space, new_indent))
2336 }
2337
2338 fn newline_for_brace(config: &Config, where_clause: &ast::WhereClause) -> bool {
2339     match config.fn_brace_style() {
2340         BraceStyle::AlwaysNextLine => true,
2341         BraceStyle::SameLineWhere if !where_clause.predicates.is_empty() => true,
2342         _ => false,
2343     }
2344 }
2345
2346 fn rewrite_generics(
2347     context: &RewriteContext,
2348     generics: &ast::Generics,
2349     shape: Shape,
2350     span: Span,
2351 ) -> Option<String> {
2352     let g_shape = try_opt!(generics_shape_from_config(context.config, shape, 0));
2353     let one_line_width = shape.width.checked_sub(2).unwrap_or(0);
2354     rewrite_generics_inner(context, generics, g_shape, one_line_width, span).or_else(|| {
2355         rewrite_generics_inner(context, generics, g_shape, 0, span)
2356     })
2357 }
2358
2359 fn rewrite_generics_inner(
2360     context: &RewriteContext,
2361     generics: &ast::Generics,
2362     shape: Shape,
2363     one_line_width: usize,
2364     span: Span,
2365 ) -> Option<String> {
2366     // FIXME: convert bounds to where clauses where they get too big or if
2367     // there is a where clause at all.
2368     let lifetimes: &[_] = &generics.lifetimes;
2369     let tys: &[_] = &generics.ty_params;
2370     if lifetimes.is_empty() && tys.is_empty() {
2371         return Some(String::new());
2372     }
2373
2374     // Strings for the generics.
2375     let lt_strs = lifetimes.iter().map(|lt| lt.rewrite(context, shape));
2376     let ty_strs = tys.iter().map(|ty_param| ty_param.rewrite(context, shape));
2377
2378     // Extract comments between generics.
2379     let lt_spans = lifetimes.iter().map(|l| {
2380         let hi = if l.bounds.is_empty() {
2381             l.lifetime.span.hi
2382         } else {
2383             l.bounds[l.bounds.len() - 1].span.hi
2384         };
2385         mk_sp(l.lifetime.span.lo, hi)
2386     });
2387     let ty_spans = tys.iter().map(|ty| ty.span());
2388
2389     let items = itemize_list(
2390         context.codemap,
2391         lt_spans.chain(ty_spans).zip(lt_strs.chain(ty_strs)),
2392         ">",
2393         |&(sp, _)| sp.lo,
2394         |&(sp, _)| sp.hi,
2395         // FIXME: don't clone
2396         |&(_, ref str)| str.clone(),
2397         context.codemap.span_after(span, "<"),
2398         span.hi,
2399     );
2400     format_generics_item_list(context, items, shape, one_line_width)
2401 }
2402
2403 pub fn generics_shape_from_config(config: &Config, shape: Shape, offset: usize) -> Option<Shape> {
2404     match config.generics_indent() {
2405         IndentStyle::Visual => shape.visual_indent(1 + offset).sub_width(offset + 2),
2406         IndentStyle::Block => {
2407             // 1 = ","
2408             shape
2409                 .block()
2410                 .block_indent(config.tab_spaces())
2411                 .with_max_width(config)
2412                 .sub_width(1)
2413         }
2414     }
2415 }
2416
2417 pub fn format_generics_item_list<I>(
2418     context: &RewriteContext,
2419     items: I,
2420     shape: Shape,
2421     one_line_budget: usize,
2422 ) -> Option<String>
2423 where
2424     I: Iterator<Item = ListItem>,
2425 {
2426     let item_vec = items.collect::<Vec<_>>();
2427
2428     let tactic = definitive_tactic(&item_vec, ListTactic::HorizontalVertical, one_line_budget);
2429     let ends_with_newline = context.config.generics_indent() == IndentStyle::Block &&
2430         tactic == DefinitiveListTactic::Vertical;
2431     let fmt = ListFormatting {
2432         tactic: tactic,
2433         separator: ",",
2434         trailing_separator: if context.config.generics_indent() == IndentStyle::Visual {
2435             SeparatorTactic::Never
2436         } else {
2437             context.config.trailing_comma()
2438         },
2439         shape: shape,
2440         ends_with_newline: ends_with_newline,
2441         config: context.config,
2442     };
2443
2444     let list_str = try_opt!(write_list(&item_vec, &fmt));
2445
2446     Some(wrap_generics_with_angle_brackets(
2447         context,
2448         &list_str,
2449         shape.indent,
2450     ))
2451 }
2452
2453 pub fn wrap_generics_with_angle_brackets(
2454     context: &RewriteContext,
2455     list_str: &str,
2456     list_offset: Indent,
2457 ) -> String {
2458     if context.config.generics_indent() == IndentStyle::Block &&
2459         (list_str.contains('\n') || list_str.ends_with(','))
2460     {
2461         format!(
2462             "<\n{}{}\n{}>",
2463             list_offset.to_string(context.config),
2464             list_str,
2465             list_offset
2466                 .block_unindent(context.config)
2467                 .to_string(context.config)
2468         )
2469     } else if context.config.spaces_within_angle_brackets() {
2470         format!("< {} >", list_str)
2471     } else {
2472         format!("<{}>", list_str)
2473     }
2474 }
2475
2476 fn rewrite_trait_bounds(
2477     context: &RewriteContext,
2478     type_param_bounds: &ast::TyParamBounds,
2479     shape: Shape,
2480 ) -> Option<String> {
2481     let bounds: &[_] = type_param_bounds;
2482
2483     if bounds.is_empty() {
2484         return Some(String::new());
2485     }
2486     let bound_str = try_opt!(
2487         bounds
2488             .iter()
2489             .map(|ty_bound| ty_bound.rewrite(&context, shape))
2490             .collect::<Option<Vec<_>>>()
2491     );
2492     Some(format!(": {}", join_bounds(context, shape, &bound_str)))
2493 }
2494
2495 fn rewrite_where_clause_rfc_style(
2496     context: &RewriteContext,
2497     where_clause: &ast::WhereClause,
2498     shape: Shape,
2499     terminator: &str,
2500     suppress_comma: bool,
2501     // where clause can be kept on the current line.
2502     snuggle: bool,
2503     span_end: Option<BytePos>,
2504     span: Span,
2505     span_end_before_where: BytePos,
2506 ) -> Option<String> {
2507     let block_shape = shape.block().with_max_width(context.config);
2508
2509     let (span_before, span_after) =
2510         missing_span_before_after_where(context, span.hi, span_end_before_where, where_clause);
2511     let (comment_before, comment_after) = try_opt!(rewrite_comments_before_after_where(
2512         context,
2513         span_before,
2514         span_after,
2515         shape,
2516     ));
2517
2518     let starting_newline = if snuggle && comment_before.is_empty() {
2519         " ".to_owned()
2520     } else {
2521         "\n".to_owned() + &block_shape.indent.to_string(context.config)
2522     };
2523
2524     let clause_shape = block_shape.block_indent(context.config.tab_spaces());
2525     // each clause on one line, trailing comma (except if suppress_comma)
2526     let span_start = where_clause.predicates[0].span().lo;
2527     // If we don't have the start of the next span, then use the end of the
2528     // predicates, but that means we miss comments.
2529     let len = where_clause.predicates.len();
2530     let end_of_preds = where_clause.predicates[len - 1].span().hi;
2531     let span_end = span_end.unwrap_or(end_of_preds);
2532     let items = itemize_list(
2533         context.codemap,
2534         where_clause.predicates.iter(),
2535         terminator,
2536         |pred| pred.span().lo,
2537         |pred| pred.span().hi,
2538         |pred| pred.rewrite(context, block_shape),
2539         span_start,
2540         span_end,
2541     );
2542     let comma_tactic = if suppress_comma {
2543         SeparatorTactic::Never
2544     } else {
2545         context.config.trailing_comma()
2546     };
2547
2548     let fmt = ListFormatting {
2549         tactic: DefinitiveListTactic::Vertical,
2550         separator: ",",
2551         trailing_separator: comma_tactic,
2552         shape: clause_shape,
2553         ends_with_newline: true,
2554         config: context.config,
2555     };
2556     let preds_str = try_opt!(write_list(&items.collect::<Vec<_>>(), &fmt));
2557
2558     let newline_before_where = if comment_before.is_empty() || comment_before.ends_with('\n') {
2559         String::new()
2560     } else {
2561         "\n".to_owned() + &shape.indent.to_string(context.config)
2562     };
2563     let newline_after_where = if comment_after.is_empty() {
2564         String::new()
2565     } else {
2566         "\n".to_owned() + &clause_shape.indent.to_string(context.config)
2567     };
2568     Some(format!(
2569         "{}{}{}where{}{}\n{}{}",
2570         starting_newline,
2571         comment_before,
2572         newline_before_where,
2573         newline_after_where,
2574         comment_after,
2575         clause_shape.indent.to_string(context.config),
2576         preds_str
2577     ))
2578 }
2579
2580 fn rewrite_where_clause(
2581     context: &RewriteContext,
2582     where_clause: &ast::WhereClause,
2583     brace_style: BraceStyle,
2584     shape: Shape,
2585     density: Density,
2586     terminator: &str,
2587     suppress_comma: bool,
2588     snuggle: bool,
2589     span_end: Option<BytePos>,
2590     span: Span,
2591     span_end_before_where: BytePos,
2592 ) -> Option<String> {
2593     if where_clause.predicates.is_empty() {
2594         return Some(String::new());
2595     }
2596
2597     if context.config.where_style() == Style::Rfc {
2598         return rewrite_where_clause_rfc_style(
2599             context,
2600             where_clause,
2601             shape,
2602             terminator,
2603             suppress_comma,
2604             snuggle,
2605             span_end,
2606             span,
2607             span_end_before_where,
2608         );
2609     }
2610
2611     let extra_indent = Indent::new(context.config.tab_spaces(), 0);
2612
2613     let offset = match context.config.where_pred_indent() {
2614         IndentStyle::Block => shape.indent + extra_indent.block_indent(context.config),
2615         // 6 = "where ".len()
2616         IndentStyle::Visual => shape.indent + extra_indent + 6,
2617     };
2618     // FIXME: if where_pred_indent != Visual, then the budgets below might
2619     // be out by a char or two.
2620
2621     let budget = context.config.max_width() - offset.width();
2622     let span_start = where_clause.predicates[0].span().lo;
2623     // If we don't have the start of the next span, then use the end of the
2624     // predicates, but that means we miss comments.
2625     let len = where_clause.predicates.len();
2626     let end_of_preds = where_clause.predicates[len - 1].span().hi;
2627     let span_end = span_end.unwrap_or(end_of_preds);
2628     let items = itemize_list(
2629         context.codemap,
2630         where_clause.predicates.iter(),
2631         terminator,
2632         |pred| pred.span().lo,
2633         |pred| pred.span().hi,
2634         |pred| pred.rewrite(context, Shape::legacy(budget, offset)),
2635         span_start,
2636         span_end,
2637     );
2638     let item_vec = items.collect::<Vec<_>>();
2639     // FIXME: we don't need to collect here if the where_layout isn't
2640     // HorizontalVertical.
2641     let tactic = definitive_tactic(&item_vec, context.config.where_layout(), budget);
2642
2643     let mut comma_tactic = context.config.trailing_comma();
2644     // Kind of a hack because we don't usually have trailing commas in where clauses.
2645     if comma_tactic == SeparatorTactic::Vertical || suppress_comma {
2646         comma_tactic = SeparatorTactic::Never;
2647     }
2648
2649     let fmt = ListFormatting {
2650         tactic: tactic,
2651         separator: ",",
2652         trailing_separator: comma_tactic,
2653         shape: Shape::legacy(budget, offset),
2654         ends_with_newline: true,
2655         config: context.config,
2656     };
2657     let preds_str = try_opt!(write_list(&item_vec, &fmt));
2658
2659     let end_length = if terminator == "{" {
2660         // If the brace is on the next line we don't need to count it otherwise it needs two
2661         // characters " {"
2662         match brace_style {
2663             BraceStyle::AlwaysNextLine | BraceStyle::SameLineWhere => 0,
2664             BraceStyle::PreferSameLine => 2,
2665         }
2666     } else if terminator == "=" {
2667         2
2668     } else {
2669         terminator.len()
2670     };
2671     if density == Density::Tall || preds_str.contains('\n') ||
2672         shape.indent.width() + " where ".len() + preds_str.len() + end_length > shape.width
2673     {
2674         Some(format!(
2675             "\n{}where {}",
2676             (shape.indent + extra_indent).to_string(context.config),
2677             preds_str
2678         ))
2679     } else {
2680         Some(format!(" where {}", preds_str))
2681     }
2682 }
2683
2684 fn missing_span_before_after_where(
2685     context: &RewriteContext,
2686     item_end: BytePos,
2687     before_item_span_end: BytePos,
2688     where_clause: &ast::WhereClause,
2689 ) -> (Span, Span) {
2690     let snippet = context.snippet(mk_sp(before_item_span_end, item_end));
2691     let pos_before_where =
2692         before_item_span_end + BytePos(snippet.find_uncommented("where").unwrap() as u32);
2693     let missing_span_before = mk_sp(before_item_span_end, pos_before_where);
2694     // 5 = `where`
2695     let pos_after_where = pos_before_where + BytePos(5);
2696     let missing_span_after = mk_sp(pos_after_where, where_clause.predicates[0].span().lo);
2697     (missing_span_before, missing_span_after)
2698 }
2699
2700 fn rewrite_missing_comment_in_where(
2701     context: &RewriteContext,
2702     comment: &str,
2703     shape: Shape,
2704 ) -> Option<String> {
2705     let comment = comment.trim();
2706     if comment.is_empty() {
2707         Some(String::new())
2708     } else {
2709         rewrite_comment(comment, false, shape, context.config)
2710     }
2711 }
2712
2713 fn rewrite_comments_before_after_where(
2714     context: &RewriteContext,
2715     span_before_where: Span,
2716     span_after_where: Span,
2717     shape: Shape,
2718 ) -> Option<(String, String)> {
2719     let before_comment = try_opt!(rewrite_missing_comment_in_where(
2720         context,
2721         &context.snippet(span_before_where),
2722         shape,
2723     ));
2724     let after_comment = try_opt!(rewrite_missing_comment_in_where(
2725         context,
2726         &context.snippet(span_after_where),
2727         shape.block_indent(context.config.tab_spaces()),
2728     ));
2729     Some((before_comment, after_comment))
2730 }
2731
2732 fn format_header(item_name: &str, ident: ast::Ident, vis: &ast::Visibility) -> String {
2733     format!("{}{}{}", format_visibility(vis), item_name, ident)
2734 }
2735
2736 fn format_generics(
2737     context: &RewriteContext,
2738     generics: &ast::Generics,
2739     opener: &str,
2740     terminator: &str,
2741     brace_style: BraceStyle,
2742     force_same_line_brace: bool,
2743     offset: Indent,
2744     span: Span,
2745     used_width: usize,
2746 ) -> Option<String> {
2747     let shape = Shape::legacy(context.budget(used_width + offset.width()), offset);
2748     let mut result = try_opt!(rewrite_generics(context, generics, shape, span));
2749
2750     if !generics.where_clause.predicates.is_empty() || result.contains('\n') {
2751         let budget = try_opt!(
2752             context
2753                 .config
2754                 .max_width()
2755                 .checked_sub(last_line_width(&result))
2756         );
2757         let where_clause_str = try_opt!(rewrite_where_clause(
2758             context,
2759             &generics.where_clause,
2760             brace_style,
2761             Shape::legacy(budget, offset.block_only()),
2762             Density::Tall,
2763             terminator,
2764             false,
2765             trimmed_last_line_width(&result) == 1,
2766             Some(span.hi),
2767             span,
2768             generics.span.hi,
2769         ));
2770         result.push_str(&where_clause_str);
2771         let same_line_brace = force_same_line_brace ||
2772             (generics.where_clause.predicates.is_empty() && trimmed_last_line_width(&result) == 1);
2773         if !same_line_brace &&
2774             (brace_style == BraceStyle::SameLineWhere ||
2775                 brace_style == BraceStyle::AlwaysNextLine)
2776         {
2777             result.push('\n');
2778             result.push_str(&offset.block_only().to_string(context.config));
2779         } else {
2780             result.push(' ');
2781         }
2782         result.push_str(opener);
2783     } else {
2784         if force_same_line_brace || trimmed_last_line_width(&result) == 1 ||
2785             brace_style != BraceStyle::AlwaysNextLine
2786         {
2787             result.push(' ');
2788         } else {
2789             result.push('\n');
2790             result.push_str(&offset.block_only().to_string(context.config));
2791         }
2792         result.push_str(opener);
2793     }
2794
2795     Some(result)
2796 }