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};
  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(..) |
 521             ast::VariantData::Struct(..) => {
 522                 // FIXME: Should limit the width, as we have a trailing comma
 523                 format_struct(
 524                     &context,
 525                     "",
 526                     field.node.name,
 527                     &ast::Visibility::Inherited,
 528                     &field.node.data,
 529                     None,
 530                     field.span,
 531                     indent,
 532                     Some(self.config.struct_variant_width()),
 533                 )
 534             }
 535             ast::VariantData::Unit(..) => {
 536                 let tag = if let Some(ref expr) = field.node.disr_expr {
 537                     format!("{} = {}", field.node.name, self.snippet(expr.span))
 538                 } else {
 539                     field.node.name.to_string()
 540                 };
 541
 542                 wrap_str(
 543                     tag,
 544                     self.config.max_width(),
 545                     Shape::indented(indent, self.config),
 546                 )
 547             }
 548         };
 549
 550         if let Some(variant_str) = variant_body {
 551             result.push_str(&variant_str);
 552             Some(result)
 553         } else {
 554             None
 555         }
 556     }
 557 }
 558
 559 pub fn format_impl(
 560     context: &RewriteContext,
 561     item: &ast::Item,
 562     offset: Indent,
 563     where_span_end: Option<BytePos>,
 564 ) -> Option<String> {
 565     if let ast::ItemKind::Impl(_, _, _, ref generics, _, _, ref items) = item.node {
 566         let mut result = String::new();
 567         let ref_and_type = try_opt!(format_impl_ref_and_type(context, item, offset));
 568         result.push_str(&ref_and_type);
 569
 570         let where_budget = if result.contains('\n') {
 571             context.config.max_width()
 572         } else {
 573             context
 574                 .config
 575                 .max_width()
 576                 .checked_sub(last_line_width(&result))
 577                 .unwrap_or(0)
 578         };
 579         let where_clause_str = try_opt!(rewrite_where_clause(
 580             context,
 581             &generics.where_clause,
 582             context.config.item_brace_style(),
 583             Shape::legacy(where_budget, offset.block_only()),
 584             context.config.where_density(),
 585             "{",
 586             false,
 587             last_line_width(&ref_and_type) == 1,
 588             where_span_end,
 589         ));
 590
 591         if try_opt!(is_impl_single_line(
 592             context,
 593             &items,
 594             &result,
 595             &where_clause_str,
 596             &item,
 597         )) {
 598             result.push_str(&where_clause_str);
 599             if where_clause_str.contains('\n') {
 600                 let white_space = offset.to_string(context.config);
 601                 result.push_str(&format!("\n{}{{\n{}}}", &white_space, &white_space));
 602             } else {
 603                 result.push_str(" {}");
 604             }
 605             return Some(result);
 606         }
 607
 608         if !where_clause_str.is_empty() && !where_clause_str.contains('\n') {
 609             result.push('\n');
 610             let width = offset.block_indent + context.config.tab_spaces() - 1;
 611             let where_indent = Indent::new(0, width);
 612             result.push_str(&where_indent.to_string(context.config));
 613         }
 614         result.push_str(&where_clause_str);
 615
 616         match context.config.item_brace_style() {
 617             BraceStyle::AlwaysNextLine => {
 618                 result.push('\n');
 619                 result.push_str(&offset.to_string(context.config));
 620             }
 621             BraceStyle::PreferSameLine => result.push(' '),
 622             BraceStyle::SameLineWhere => {
 623                 if !where_clause_str.is_empty() {
 624                     result.push('\n');
 625                     result.push_str(&offset.to_string(context.config));
 626                 } else {
 627                     result.push(' ');
 628                 }
 629             }
 630         }
 631
 632         result.push('{');
 633
 634         let snippet = context.snippet(item.span);
 635         let open_pos = try_opt!(snippet.find_uncommented("{")) + 1;
 636
 637         if !items.is_empty() || contains_comment(&snippet[open_pos..]) {
 638             let mut visitor = FmtVisitor::from_codemap(context.parse_session, context.config);
 639             visitor.block_indent = offset.block_only().block_indent(context.config);
 640             visitor.last_pos = item.span.lo + BytePos(open_pos as u32);
 641
 642             for item in items {
 643                 visitor.visit_impl_item(item);
 644             }
 645
 646             visitor.format_missing(item.span.hi - BytePos(1));
 647
 648             let inner_indent_str = visitor.block_indent.to_string(context.config);
 649             let outer_indent_str = offset.block_only().to_string(context.config);
 650
 651             result.push('\n');
 652             result.push_str(&inner_indent_str);
 653             result.push_str(trim_newlines(visitor.buffer.to_string().trim()));
 654             result.push('\n');
 655             result.push_str(&outer_indent_str);
 656         }
 657
 658         if result.chars().last().unwrap() == '{' {
 659             result.push('\n');
 660             result.push_str(&offset.to_string(context.config));
 661         }
 662         result.push('}');
 663
 664         Some(result)
 665     } else {
 666         unreachable!();
 667     }
 668 }
 669
 670 fn is_impl_single_line(
 671     context: &RewriteContext,
 672     items: &[ImplItem],
 673     result: &str,
 674     where_clause_str: &str,
 675     item: &ast::Item,
 676 ) -> Option<bool> {
 677     let snippet = context.snippet(item.span);
 678     let open_pos = try_opt!(snippet.find_uncommented("{")) + 1;
 679
 680     Some(
 681         context.config.impl_empty_single_line() && items.is_empty() &&
 682             result.len() + where_clause_str.len() <= context.config.max_width() &&
 683             !contains_comment(&snippet[open_pos..]),
 684     )
 685 }
 686
 687 fn format_impl_ref_and_type(
 688     context: &RewriteContext,
 689     item: &ast::Item,
 690     offset: Indent,
 691 ) -> Option<String> {
 692     if let ast::ItemKind::Impl(
 693         unsafety,
 694         polarity,
 695         _,
 696         ref generics,
 697         ref trait_ref,
 698         ref self_ty,
 699         _,
 700     ) = item.node
 701     {
 702         let mut result = String::new();
 703
 704         result.push_str(&format_visibility(&item.vis));
 705         result.push_str(format_unsafety(unsafety));
 706         result.push_str("impl");
 707
 708         let lo = context.codemap.span_after(item.span, "impl");
 709         let hi = match *trait_ref {
 710             Some(ref tr) => tr.path.span.lo,
 711             None => self_ty.span.lo,
 712         };
 713         let shape = try_opt!(generics_shape_from_config(
 714             context.config,
 715             Shape::indented(offset + last_line_width(&result), context.config),
 716             0,
 717         ));
 718         let one_line_budget = try_opt!(shape.width.checked_sub(last_line_width(&result) + 2));
 719         let generics_str = try_opt!(rewrite_generics_inner(
 720             context,
 721             generics,
 722             shape,
 723             one_line_budget,
 724             mk_sp(lo, hi),
 725         ));
 726
 727         let polarity_str = if polarity == ast::ImplPolarity::Negative {
 728             "!"
 729         } else {
 730             ""
 731         };
 732
 733         if let Some(ref trait_ref) = *trait_ref {
 734             let result_len = result.len();
 735             if let Some(trait_ref_str) =
 736                 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 where_clause_str = try_opt!(rewrite_where_clause(
 969             context,
 970             &generics.where_clause,
 971             context.config.item_brace_style(),
 972             Shape::legacy(where_budget, offset.block_only()),
 973             where_density,
 974             "{",
 975             !has_body,
 976             trait_bound_str.is_empty() && last_line_width(&generics_str) == 1,
 977             None,
 978         ));
 979         // If the where clause cannot fit on the same line,
 980         // put the where clause on a new line
 981         if !where_clause_str.contains('\n') &&
 982             last_line_width(&result) + where_clause_str.len() + offset.width() >
 983                 context.config.comment_width()
 984         {
 985             result.push('\n');
 986             let width = offset.block_indent + context.config.tab_spaces() - 1;
 987             let where_indent = Indent::new(0, width);
 988             result.push_str(&where_indent.to_string(context.config));
 989         }
 990         result.push_str(&where_clause_str);
 991
 992         match context.config.item_brace_style() {
 993             BraceStyle::AlwaysNextLine => {
 994                 result.push('\n');
 995                 result.push_str(&offset.to_string(context.config));
 996             }
 997             BraceStyle::PreferSameLine => result.push(' '),
 998             BraceStyle::SameLineWhere => {
 999                 if !where_clause_str.is_empty() &&
1000                     (!trait_items.is_empty() || result.contains('\n'))
1001                 {
1002                     result.push('\n');
1003                     result.push_str(&offset.to_string(context.config));
1004                 } else {
1005                     result.push(' ');
1006                 }
1007             }
1008         }
1009         result.push('{');
1010
1011         let snippet = context.snippet(item.span);
1012         let open_pos = try_opt!(snippet.find_uncommented("{")) + 1;
1013
1014         if !trait_items.is_empty() || contains_comment(&snippet[open_pos..]) {
1015             let mut visitor = FmtVisitor::from_codemap(context.parse_session, context.config);
1016             visitor.block_indent = offset.block_only().block_indent(context.config);
1017             visitor.last_pos = item.span.lo + BytePos(open_pos as u32);
1018
1019             for item in trait_items {
1020                 visitor.visit_trait_item(item);
1021             }
1022
1023             visitor.format_missing(item.span.hi - BytePos(1));
1024
1025             let inner_indent_str = visitor.block_indent.to_string(context.config);
1026             let outer_indent_str = offset.block_only().to_string(context.config);
1027
1028             result.push('\n');
1029             result.push_str(&inner_indent_str);
1030             result.push_str(trim_newlines(visitor.buffer.to_string().trim()));
1031             result.push('\n');
1032             result.push_str(&outer_indent_str);
1033         } else if result.contains('\n') {
1034             result.push('\n');
1035         }
1036
1037         result.push('}');
1038         Some(result)
1039     } else {
1040         unreachable!();
1041     }
1042 }
1043
1044 fn format_unit_struct(item_name: &str, ident: ast::Ident, vis: &ast::Visibility) -> String {
1045     format!("{};", format_header(item_name, ident, vis))
1046 }
1047
1048 fn format_struct_struct(
1049     context: &RewriteContext,
1050     item_name: &str,
1051     ident: ast::Ident,
1052     vis: &ast::Visibility,
1053     fields: &[ast::StructField],
1054     generics: Option<&ast::Generics>,
1055     span: Span,
1056     offset: Indent,
1057     one_line_width: Option<usize>,
1058 ) -> Option<String> {
1059     let mut result = String::with_capacity(1024);
1060
1061     let header_str = format_header(item_name, ident, vis);
1062     result.push_str(&header_str);
1063
1064     let body_lo = context.codemap.span_after(span, "{");
1065
1066     let generics_str = match generics {
1067         Some(g) => {
1068             try_opt!(format_generics(
1069                 context,
1070                 g,
1071                 "{",
1072                 "{",
1073                 context.config.item_brace_style(),
1074                 fields.is_empty(),
1075                 offset,
1076                 mk_sp(span.lo, body_lo),
1077                 last_line_width(&result),
1078             ))
1079         }
1080         None => {
1081             // 3 = ` {}`, 2 = ` {`.
1082             let overhead = if fields.is_empty() { 3 } else { 2 };
1083             if (context.config.item_brace_style() == BraceStyle::AlwaysNextLine &&
1084                     !fields.is_empty()) ||
1085                 context
1086                     .config
1087                     .max_width()
1088                     .checked_sub(result.len())
1089                     .unwrap_or(0) < overhead
1090             {
1091                 format!("\n{}{{", offset.block_only().to_string(context.config))
1092             } else {
1093                 " {".to_owned()
1094             }
1095         }
1096     };
1097     // 1 = `}`
1098     let overhead = if fields.is_empty() { 1 } else { 0 };
1099     let max_len = context.config.max_width() - offset.width();
1100     if !generics_str.contains('\n') && result.len() + generics_str.len() + overhead > max_len {
1101         result.push('\n');
1102         result.push_str(&offset
1103             .block_indent(context.config)
1104             .to_string(context.config));
1105         result.push_str(&generics_str.trim_left());
1106     } else {
1107         result.push_str(&generics_str);
1108     }
1109
1110     if fields.is_empty() {
1111         let snippet = context.snippet(mk_sp(body_lo, span.hi - BytePos(1)));
1112         if snippet.trim().is_empty() {
1113             // `struct S {}`
1114         } else if snippet.trim_right_matches(&[' ', '\t'][..]).ends_with('\n') {
1115             // fix indent
1116             result.push_str(&snippet.trim_right());
1117             result.push('\n');
1118             result.push_str(&offset.to_string(context.config));
1119         } else {
1120             result.push_str(&snippet);
1121         }
1122         result.push('}');
1123         return Some(result);
1124     }
1125
1126     let items_str = try_opt!(rewrite_with_alignment(
1127         fields,
1128         context,
1129         Shape::indented(offset, context.config),
1130         mk_sp(body_lo, span.hi),
1131         one_line_width.unwrap_or(0),
1132     ));
1133
1134     if one_line_width.is_some() && !items_str.contains('\n') {
1135         Some(format!("{} {} }}", result, items_str))
1136     } else {
1137         Some(format!(
1138             "{}\n{}{}\n{}}}",
1139             result,
1140             offset
1141                 .block_indent(context.config)
1142                 .to_string(context.config),
1143             items_str,
1144             offset.to_string(context.config)
1145         ))
1146     }
1147 }
1148
1149 fn format_tuple_struct(
1150     context: &RewriteContext,
1151     item_name: &str,
1152     ident: ast::Ident,
1153     vis: &ast::Visibility,
1154     fields: &[ast::StructField],
1155     generics: Option<&ast::Generics>,
1156     span: Span,
1157     offset: Indent,
1158 ) -> Option<String> {
1159     let mut result = String::with_capacity(1024);
1160
1161     let header_str = format_header(item_name, ident, vis);
1162     result.push_str(&header_str);
1163
1164     let body_lo = if fields.is_empty() {
1165         context.codemap.span_after(span, "(")
1166     } else {
1167         fields[0].span.lo
1168     };
1169
1170     let where_clause_str = match generics {
1171         Some(generics) => {
1172             let budget = context.budget(last_line_width(&header_str));
1173             let shape = Shape::legacy(budget, offset);
1174             let g_span = mk_sp(span.lo, body_lo);
1175             let generics_str = try_opt!(rewrite_generics(context, generics, shape, g_span));
1176             result.push_str(&generics_str);
1177
1178             let where_budget = context.budget(last_line_width(&result));
1179             try_opt!(rewrite_where_clause(
1180                 context,
1181                 &generics.where_clause,
1182                 context.config.item_brace_style(),
1183                 Shape::legacy(where_budget, offset.block_only()),
1184                 Density::Compressed,
1185                 ";",
1186                 true,
1187                 false,
1188                 None,
1189             ))
1190         }
1191         None => "".to_owned(),
1192     };
1193
1194     if fields.is_empty() {
1195         // 3 = `();`
1196         let used_width = if result.contains('\n') {
1197             last_line_width(&result) + 3
1198         } else {
1199             offset.width() + result.len() + 3
1200         };
1201         if used_width > context.config.max_width() {
1202             result.push('\n');
1203             result.push_str(&offset
1204                 .block_indent(context.config)
1205                 .to_string(context.config))
1206         }
1207         result.push('(');
1208         let snippet = context.snippet(mk_sp(body_lo, context.codemap.span_before(span, ")")));
1209         if snippet.is_empty() {
1210             // `struct S ()`
1211         } else if snippet.trim_right_matches(&[' ', '\t'][..]).ends_with('\n') {
1212             result.push_str(&snippet.trim_right());
1213             result.push('\n');
1214             result.push_str(&offset.to_string(context.config));
1215         } else {
1216             result.push_str(&snippet);
1217         }
1218         result.push(')');
1219     } else {
1220         // 3 = `();`
1221         let body = try_opt!(
1222             rewrite_call_inner(
1223                 context,
1224                 "",
1225                 &fields.iter().map(|field| field).collect::<Vec<_>>()[..],
1226                 span,
1227                 Shape::legacy(context.budget(last_line_width(&result) + 3), offset),
1228                 context.config.fn_call_width(),
1229                 false,
1230             ).ok()
1231         );
1232         result.push_str(&body);
1233     }
1234
1235     if !where_clause_str.is_empty() && !where_clause_str.contains('\n') &&
1236         (result.contains('\n') ||
1237              offset.block_indent + result.len() + where_clause_str.len() + 1 >
1238                  context.config.max_width())
1239     {
1240         // We need to put the where clause on a new line, but we didn't
1241         // know that earlier, so the where clause will not be indented properly.
1242         result.push('\n');
1243         result.push_str(&(offset.block_only() + (context.config.tab_spaces() - 1))
1244             .to_string(context.config));
1245     }
1246     result.push_str(&where_clause_str);
1247
1248     Some(result)
1249 }
1250
1251 pub fn rewrite_type_alias(
1252     context: &RewriteContext,
1253     indent: Indent,
1254     ident: ast::Ident,
1255     ty: &ast::Ty,
1256     generics: &ast::Generics,
1257     vis: &ast::Visibility,
1258     span: Span,
1259 ) -> Option<String> {
1260     let mut result = String::new();
1261
1262     result.push_str(&format_visibility(vis));
1263     result.push_str("type ");
1264     result.push_str(&ident.to_string());
1265
1266     // 2 = `= `
1267     let shape = try_opt!(Shape::indented(indent + result.len(), context.config).sub_width(2));
1268     let g_span = mk_sp(context.codemap.span_after(span, "type"), ty.span.lo);
1269     let generics_str = try_opt!(rewrite_generics(context, generics, shape, g_span));
1270     result.push_str(&generics_str);
1271
1272     let where_budget = try_opt!(
1273         context
1274             .config
1275             .max_width()
1276             .checked_sub(last_line_width(&result))
1277     );
1278     let where_clause_str = try_opt!(rewrite_where_clause(
1279         context,
1280         &generics.where_clause,
1281         context.config.item_brace_style(),
1282         Shape::legacy(where_budget, indent),
1283         context.config.where_density(),
1284         "=",
1285         true,
1286         true,
1287         Some(span.hi),
1288     ));
1289     result.push_str(&where_clause_str);
1290     result.push_str(" = ");
1291
1292     let line_width = last_line_width(&result);
1293     // This checked_sub may fail as the extra space after '=' is not taken into account
1294     // In that case the budget is set to 0 which will make ty.rewrite retry on a new line
1295     let budget = context
1296         .config
1297         .max_width()
1298         .checked_sub(indent.width() + line_width + ";".len())
1299         .unwrap_or(0);
1300     let type_indent = indent + line_width;
1301     // Try to fit the type on the same line
1302     let ty_str = try_opt!(
1303         ty.rewrite(context, Shape::legacy(budget, type_indent))
1304             .or_else(|| {
1305                 // The line was too short, try to put the type on the next line
1306
1307                 // Remove the space after '='
1308                 result.pop();
1309                 let type_indent = indent.block_indent(context.config);
1310                 result.push('\n');
1311                 result.push_str(&type_indent.to_string(context.config));
1312                 let budget = try_opt!(
1313                     context
1314                         .config
1315                         .max_width()
1316                         .checked_sub(type_indent.width() + ";".len())
1317                 );
1318                 ty.rewrite(context, Shape::legacy(budget, type_indent))
1319             })
1320     );
1321     result.push_str(&ty_str);
1322     result.push_str(";");
1323     Some(result)
1324 }
1325
1326 fn type_annotation_spacing(config: &Config) -> (&str, &str) {
1327     (
1328         if config.space_before_type_annotation() {
1329             " "
1330         } else {
1331             ""
1332         },
1333         if config.space_after_type_annotation_colon() {
1334             " "
1335         } else {
1336             ""
1337         },
1338     )
1339 }
1340
1341 fn rewrite_missing_comment_on_field(
1342     context: &RewriteContext,
1343     shape: Shape,
1344     lo: BytePos,
1345     hi: BytePos,
1346     result: &mut String,
1347 ) -> Option<String> {
1348     let possibly_comment_snippet = context.snippet(mk_sp(lo, hi));
1349     let newline_index = possibly_comment_snippet.find('\n');
1350     let comment_index = possibly_comment_snippet.find('/');
1351     match (newline_index, comment_index) {
1352         (Some(i), Some(j)) if i > j => result.push(' '),
1353         _ => {
1354             result.push('\n');
1355             result.push_str(&shape.indent.to_string(context.config));
1356         }
1357     }
1358     let trimmed = possibly_comment_snippet.trim();
1359     if trimmed.is_empty() {
1360         None
1361     } else {
1362         rewrite_comment(trimmed, false, shape, context.config).map(|s| {
1363             format!("{}\n{}", s, shape.indent.to_string(context.config))
1364         })
1365     }
1366 }
1367
1368 pub fn rewrite_struct_field_prefix(
1369     context: &RewriteContext,
1370     field: &ast::StructField,
1371     shape: Shape,
1372 ) -> Option<String> {
1373     let vis = format_visibility(&field.vis);
1374     let mut attr_str = try_opt!(
1375         field
1376             .attrs
1377             .rewrite(context, Shape::indented(shape.indent, context.config))
1378     );
1379     // Try format missing comments after attributes
1380     let missing_comment = if !field.attrs.is_empty() {
1381         rewrite_missing_comment_on_field(
1382             context,
1383             shape,
1384             field.attrs[field.attrs.len() - 1].span.hi,
1385             field.span.lo,
1386             &mut attr_str,
1387         ).unwrap_or(String::new())
1388     } else {
1389         String::new()
1390     };
1391
1392     let type_annotation_spacing = type_annotation_spacing(context.config);
1393     Some(match field.ident {
1394         Some(name) => {
1395             format!(
1396                 "{}{}{}{}{}:",
1397                 attr_str,
1398                 missing_comment,
1399                 vis,
1400                 name,
1401                 type_annotation_spacing.0
1402             )
1403         }
1404         None => format!("{}{}{}", attr_str, missing_comment, vis),
1405     })
1406 }
1407
1408 fn rewrite_struct_field_type(
1409     context: &RewriteContext,
1410     last_line_width: usize,
1411     field: &ast::StructField,
1412     spacing: &str,
1413     shape: Shape,
1414 ) -> Option<String> {
1415     let ty_shape = try_opt!(shape.offset_left(last_line_width + spacing.len()));
1416     field
1417         .ty
1418         .rewrite(context, ty_shape)
1419         .map(|ty| format!("{}{}", spacing, ty))
1420 }
1421
1422 impl Rewrite for ast::StructField {
1423     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
1424         rewrite_struct_field(context, self, shape, 0)
1425     }
1426 }
1427
1428 pub fn rewrite_struct_field(
1429     context: &RewriteContext,
1430     field: &ast::StructField,
1431     shape: Shape,
1432     lhs_max_width: usize,
1433 ) -> Option<String> {
1434     if contains_skip(&field.attrs) {
1435         let span = context.snippet(mk_sp(field.attrs[0].span.lo, field.span.hi));
1436         return wrap_str(span, context.config.max_width(), shape);
1437     }
1438
1439     let type_annotation_spacing = type_annotation_spacing(context.config);
1440     let prefix = try_opt!(rewrite_struct_field_prefix(context, field, shape));
1441
1442     // Try to put everything on a single line.
1443     let last_line_width = last_line_width(&prefix);
1444     let mut spacing = String::from(if field.ident.is_some() {
1445         type_annotation_spacing.1
1446     } else {
1447         ""
1448     });
1449     let lhs_offset = lhs_max_width.checked_sub(last_line_width).unwrap_or(0);
1450     for _ in 0..lhs_offset {
1451         spacing.push(' ');
1452     }
1453     let ty_rewritten = rewrite_struct_field_type(context, last_line_width, field, &spacing, shape);
1454     if let Some(ref ty) = ty_rewritten {
1455         if !ty.contains('\n') {
1456             return Some(prefix + &ty);
1457         }
1458     }
1459
1460     // We must use multiline.
1461     let type_offset = shape.indent.block_indent(context.config);
1462     let rewrite_type_in_next_line = || {
1463         field
1464             .ty
1465             .rewrite(context, Shape::indented(type_offset, context.config))
1466     };
1467
1468     match ty_rewritten {
1469         // If we start from the next line and type fits in a single line, then do so.
1470         Some(ref ty) => {
1471             match rewrite_type_in_next_line() {
1472                 Some(ref new_ty) if !new_ty.contains('\n') => {
1473                     Some(format!(
1474                         "{}\n{}{}",
1475                         prefix,
1476                         type_offset.to_string(&context.config),
1477                         &new_ty
1478                     ))
1479                 }
1480                 _ => Some(prefix + &ty),
1481             }
1482         }
1483         _ => {
1484             let ty = try_opt!(rewrite_type_in_next_line());
1485             Some(format!(
1486                 "{}\n{}{}",
1487                 prefix,
1488                 type_offset.to_string(&context.config),
1489                 &ty
1490             ))
1491         }
1492     }
1493 }
1494
1495 pub fn rewrite_static(
1496     prefix: &str,
1497     vis: &ast::Visibility,
1498     ident: ast::Ident,
1499     ty: &ast::Ty,
1500     mutability: ast::Mutability,
1501     expr_opt: Option<&ptr::P<ast::Expr>>,
1502     offset: Indent,
1503     span: Span,
1504     context: &RewriteContext,
1505 ) -> Option<String> {
1506     let colon = colon_spaces(
1507         context.config.space_before_type_annotation(),
1508         context.config.space_after_type_annotation_colon(),
1509     );
1510     let prefix = format!(
1511         "{}{} {}{}{}",
1512         format_visibility(vis),
1513         prefix,
1514         format_mutability(mutability),
1515         ident,
1516         colon,
1517     );
1518     // 2 = " =".len()
1519     let ty_str = try_opt!(ty.rewrite(
1520         context,
1521         try_opt!(
1522             Shape::indented(offset.block_only(), context.config).offset_left(prefix.len() + 2)
1523         ),
1524     ));
1525
1526     if let Some(expr) = expr_opt {
1527         let lhs = format!("{}{} =", prefix, ty_str);
1528         // 1 = ;
1529         let remaining_width = context.config.max_width() - offset.block_indent - 1;
1530         rewrite_assign_rhs(
1531             context,
1532             lhs,
1533             expr,
1534             Shape::legacy(remaining_width, offset.block_only()),
1535         ).and_then(|res| {
1536             recover_comment_removed(res, span, context, Shape::indented(offset, context.config))
1537         })
1538             .map(|s| if s.ends_with(';') { s } else { s + ";" })
1539     } else {
1540         Some(format!("{}{};", prefix, ty_str))
1541     }
1542 }
1543
1544 pub fn rewrite_associated_type(
1545     ident: ast::Ident,
1546     ty_opt: Option<&ptr::P<ast::Ty>>,
1547     ty_param_bounds_opt: Option<&ast::TyParamBounds>,
1548     context: &RewriteContext,
1549     indent: Indent,
1550 ) -> Option<String> {
1551     let prefix = format!("type {}", ident);
1552
1553     let type_bounds_str = if let Some(ty_param_bounds) = ty_param_bounds_opt {
1554         let shape = Shape::indented(indent, context.config);
1555         let bounds: &[_] = ty_param_bounds;
1556         let bound_str = try_opt!(
1557             bounds
1558                 .iter()
1559                 .map(|ty_bound| ty_bound.rewrite(context, shape))
1560                 .collect::<Option<Vec<_>>>()
1561         );
1562         if bounds.len() > 0 {
1563             format!(": {}", join_bounds(context, shape, &bound_str))
1564         } else {
1565             String::new()
1566         }
1567     } else {
1568         String::new()
1569     };
1570
1571     if let Some(ty) = ty_opt {
1572         let ty_str = try_opt!(ty.rewrite(
1573             context,
1574             Shape::legacy(
1575                 context.config.max_width() - indent.block_indent - prefix.len() - 2,
1576                 indent.block_only(),
1577             ),
1578         ));
1579         Some(format!("{} = {};", prefix, ty_str))
1580     } else {
1581         Some(format!("{}{};", prefix, type_bounds_str))
1582     }
1583 }
1584
1585 pub fn rewrite_associated_impl_type(
1586     ident: ast::Ident,
1587     defaultness: ast::Defaultness,
1588     ty_opt: Option<&ptr::P<ast::Ty>>,
1589     ty_param_bounds_opt: Option<&ast::TyParamBounds>,
1590     context: &RewriteContext,
1591     indent: Indent,
1592 ) -> Option<String> {
1593     let result = try_opt!(rewrite_associated_type(
1594         ident,
1595         ty_opt,
1596         ty_param_bounds_opt,
1597         context,
1598         indent,
1599     ));
1600
1601     match defaultness {
1602         ast::Defaultness::Default => Some(format!("default {}", result)),
1603         _ => Some(result),
1604     }
1605 }
1606
1607 impl Rewrite for ast::FunctionRetTy {
1608     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
1609         match *self {
1610             ast::FunctionRetTy::Default(_) => Some(String::new()),
1611             ast::FunctionRetTy::Ty(ref ty) => {
1612                 let inner_width = try_opt!(shape.width.checked_sub(3));
1613                 ty.rewrite(context, Shape::legacy(inner_width, shape.indent + 3))
1614                     .map(|r| format!("-> {}", r))
1615             }
1616         }
1617     }
1618 }
1619
1620 fn is_empty_infer(context: &RewriteContext, ty: &ast::Ty) -> bool {
1621     match ty.node {
1622         ast::TyKind::Infer => {
1623             let original = context.snippet(ty.span);
1624             original != "_"
1625         }
1626         _ => false,
1627     }
1628 }
1629
1630 impl Rewrite for ast::Arg {
1631     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
1632         if is_named_arg(self) {
1633             let mut result = try_opt!(
1634                 self.pat
1635                     .rewrite(context, Shape::legacy(shape.width, shape.indent))
1636             );
1637
1638             if !is_empty_infer(context, &*self.ty) {
1639                 if context.config.space_before_type_annotation() {
1640                     result.push_str(" ");
1641                 }
1642                 result.push_str(":");
1643                 if context.config.space_after_type_annotation_colon() {
1644                     result.push_str(" ");
1645                 }
1646                 let max_width = try_opt!(shape.width.checked_sub(result.len()));
1647                 let ty_str = try_opt!(self.ty.rewrite(
1648                     context,
1649                     Shape::legacy(max_width, shape.indent + result.len()),
1650                 ));
1651                 result.push_str(&ty_str);
1652             }
1653
1654             Some(result)
1655         } else {
1656             self.ty.rewrite(context, shape)
1657         }
1658     }
1659 }
1660
1661 fn rewrite_explicit_self(
1662     explicit_self: &ast::ExplicitSelf,
1663     args: &[ast::Arg],
1664     context: &RewriteContext,
1665 ) -> Option<String> {
1666     match explicit_self.node {
1667         ast::SelfKind::Region(lt, m) => {
1668             let mut_str = format_mutability(m);
1669             match lt {
1670                 Some(ref l) => {
1671                     let lifetime_str = try_opt!(l.rewrite(
1672                         context,
1673                         Shape::legacy(context.config.max_width(), Indent::empty()),
1674                     ));
1675                     Some(format!("&{} {}self", lifetime_str, mut_str))
1676                 }
1677                 None => Some(format!("&{}self", mut_str)),
1678             }
1679         }
1680         ast::SelfKind::Explicit(ref ty, _) => {
1681             assert!(!args.is_empty(), "&[ast::Arg] shouldn't be empty.");
1682
1683             let mutability = explicit_self_mutability(&args[0]);
1684             let type_str = try_opt!(ty.rewrite(
1685                 context,
1686                 Shape::legacy(context.config.max_width(), Indent::empty()),
1687             ));
1688
1689             Some(format!(
1690                 "{}self: {}",
1691                 format_mutability(mutability),
1692                 type_str
1693             ))
1694         }
1695         ast::SelfKind::Value(_) => {
1696             assert!(!args.is_empty(), "&[ast::Arg] shouldn't be empty.");
1697
1698             let mutability = explicit_self_mutability(&args[0]);
1699
1700             Some(format!("{}self", format_mutability(mutability)))
1701         }
1702     }
1703 }
1704
1705 // Hacky solution caused by absence of `Mutability` in `SelfValue` and
1706 // `SelfExplicit` variants of `ast::ExplicitSelf_`.
1707 fn explicit_self_mutability(arg: &ast::Arg) -> ast::Mutability {
1708     if let ast::PatKind::Ident(ast::BindingMode::ByValue(mutability), _, _) = arg.pat.node {
1709         mutability
1710     } else {
1711         unreachable!()
1712     }
1713 }
1714
1715 pub fn span_lo_for_arg(arg: &ast::Arg) -> BytePos {
1716     if is_named_arg(arg) {
1717         arg.pat.span.lo
1718     } else {
1719         arg.ty.span.lo
1720     }
1721 }
1722
1723 pub fn span_hi_for_arg(context: &RewriteContext, arg: &ast::Arg) -> BytePos {
1724     match arg.ty.node {
1725         ast::TyKind::Infer if context.snippet(arg.ty.span) == "_" => arg.ty.span.hi,
1726         ast::TyKind::Infer if is_named_arg(arg) => arg.pat.span.hi,
1727         _ => arg.ty.span.hi,
1728     }
1729 }
1730
1731 pub fn is_named_arg(arg: &ast::Arg) -> bool {
1732     if let ast::PatKind::Ident(_, ident, _) = arg.pat.node {
1733         ident.node != symbol::keywords::Invalid.ident()
1734     } else {
1735         true
1736     }
1737 }
1738
1739 fn span_for_return(ret: &ast::FunctionRetTy) -> Span {
1740     match *ret {
1741         ast::FunctionRetTy::Default(ref span) => span.clone(),
1742         ast::FunctionRetTy::Ty(ref ty) => ty.span,
1743     }
1744 }
1745
1746 fn span_for_ty_param(ty: &ast::TyParam) -> Span {
1747     // Note that ty.span is the span for ty.ident, not the whole item.
1748     let lo = if ty.attrs.is_empty() {
1749         ty.span.lo
1750     } else {
1751         ty.attrs[0].span.lo
1752     };
1753     if let Some(ref def) = ty.default {
1754         return mk_sp(lo, def.span.hi);
1755     }
1756     if ty.bounds.is_empty() {
1757         return mk_sp(lo, ty.span.hi);
1758     }
1759     let hi = match ty.bounds[ty.bounds.len() - 1] {
1760         ast::TyParamBound::TraitTyParamBound(ref ptr, _) => ptr.span.hi,
1761         ast::TyParamBound::RegionTyParamBound(ref l) => l.span.hi,
1762     };
1763     mk_sp(lo, hi)
1764 }
1765
1766 fn span_for_where_pred(pred: &ast::WherePredicate) -> Span {
1767     match *pred {
1768         ast::WherePredicate::BoundPredicate(ref p) => p.span,
1769         ast::WherePredicate::RegionPredicate(ref p) => p.span,
1770         ast::WherePredicate::EqPredicate(ref p) => p.span,
1771     }
1772 }
1773
1774 // Return type is (result, force_new_line_for_brace)
1775 fn rewrite_fn_base(
1776     context: &RewriteContext,
1777     indent: Indent,
1778     ident: ast::Ident,
1779     fd: &ast::FnDecl,
1780     generics: &ast::Generics,
1781     unsafety: ast::Unsafety,
1782     constness: ast::Constness,
1783     defaultness: ast::Defaultness,
1784     abi: abi::Abi,
1785     vis: &ast::Visibility,
1786     span: Span,
1787     newline_brace: bool,
1788     has_body: bool,
1789     has_braces: bool,
1790 ) -> Option<(String, bool)> {
1791     let mut force_new_line_for_brace = false;
1792
1793     let where_clause = &generics.where_clause;
1794
1795     let mut result = String::with_capacity(1024);
1796     // Vis unsafety abi.
1797     result.push_str(&*format_visibility(vis));
1798
1799     if let ast::Defaultness::Default = defaultness {
1800         result.push_str("default ");
1801     }
1802
1803     if let ast::Constness::Const = constness {
1804         result.push_str("const ");
1805     }
1806
1807     result.push_str(::utils::format_unsafety(unsafety));
1808
1809     if abi != abi::Abi::Rust {
1810         result.push_str(&::utils::format_abi(
1811             abi,
1812             context.config.force_explicit_abi(),
1813         ));
1814     }
1815
1816     // fn foo
1817     result.push_str("fn ");
1818     result.push_str(&ident.to_string());
1819
1820     // Generics.
1821     let overhead = if has_braces && !newline_brace {
1822         // 4 = `() {`
1823         4
1824     } else {
1825         // 2 = `()`
1826         2
1827     };
1828     let shape = try_opt!(
1829         Shape::indented(indent + last_line_width(&result), context.config).sub_width(overhead)
1830     );
1831     let g_span = mk_sp(span.lo, span_for_return(&fd.output).lo);
1832     let generics_str = try_opt!(rewrite_generics(context, generics, shape, g_span));
1833     result.push_str(&generics_str);
1834
1835     let snuggle_angle_bracket = generics_str
1836         .lines()
1837         .last()
1838         .map_or(false, |l| l.trim_left().len() == 1);
1839
1840     // Note that the width and indent don't really matter, we'll re-layout the
1841     // return type later anyway.
1842     let ret_str = try_opt!(
1843         fd.output
1844             .rewrite(&context, Shape::indented(indent, context.config))
1845     );
1846
1847     let multi_line_ret_str = ret_str.contains('\n');
1848     let ret_str_len = if multi_line_ret_str { 0 } else { ret_str.len() };
1849
1850     // Args.
1851     let (mut one_line_budget, mut multi_line_budget, mut arg_indent) =
1852         try_opt!(compute_budgets_for_args(
1853             context,
1854             &result,
1855             indent,
1856             ret_str_len,
1857             newline_brace,
1858             has_braces,
1859         ));
1860
1861     if context.config.fn_args_layout() == IndentStyle::Block {
1862         arg_indent = indent.block_indent(context.config);
1863         // 1 = ","
1864         multi_line_budget = context.config.max_width() - (arg_indent.width() + 1);
1865     }
1866
1867     debug!(
1868         "rewrite_fn_base: one_line_budget: {}, multi_line_budget: {}, arg_indent: {:?}",
1869         one_line_budget,
1870         multi_line_budget,
1871         arg_indent
1872     );
1873
1874     // Check if vertical layout was forced.
1875     if one_line_budget == 0 {
1876         if snuggle_angle_bracket {
1877             result.push('(');
1878         } else {
1879             if context.config.fn_args_paren_newline() {
1880                 result.push('\n');
1881                 result.push_str(&arg_indent.to_string(context.config));
1882                 if context.config.fn_args_layout() == IndentStyle::Visual {
1883                     arg_indent = arg_indent + 1; // extra space for `(`
1884                 }
1885                 result.push('(');
1886             } else {
1887                 result.push_str("(");
1888                 if context.config.fn_args_layout() == IndentStyle::Visual {
1889                     result.push('\n');
1890                     result.push_str(&arg_indent.to_string(context.config));
1891                 }
1892             }
1893         }
1894     } else {
1895         result.push('(');
1896     }
1897     if context.config.spaces_within_parens() && fd.inputs.len() > 0 && result.ends_with('(') {
1898         result.push(' ')
1899     }
1900
1901     if multi_line_ret_str {
1902         one_line_budget = 0;
1903     }
1904
1905     // A conservative estimation, to goal is to be over all parens in generics
1906     let args_start = generics
1907         .ty_params
1908         .last()
1909         .map_or(span.lo, |tp| end_typaram(tp));
1910     let args_span = mk_sp(
1911         context.codemap.span_after(mk_sp(args_start, span.hi), "("),
1912         span_for_return(&fd.output).lo,
1913     );
1914     let arg_str = try_opt!(rewrite_args(
1915         context,
1916         &fd.inputs,
1917         fd.get_self().as_ref(),
1918         one_line_budget,
1919         multi_line_budget,
1920         indent,
1921         arg_indent,
1922         args_span,
1923         fd.variadic,
1924         generics_str.contains('\n'),
1925     ));
1926
1927     let multi_line_arg_str =
1928         arg_str.contains('\n') || arg_str.chars().last().map_or(false, |c| c == ',');
1929
1930     let put_args_in_block = match context.config.fn_args_layout() {
1931         IndentStyle::Block => multi_line_arg_str || generics_str.contains('\n'),
1932         _ => false,
1933     } && !fd.inputs.is_empty();
1934
1935     let mut args_last_line_contains_comment = false;
1936     if put_args_in_block {
1937         arg_indent = indent.block_indent(context.config);
1938         result.push('\n');
1939         result.push_str(&arg_indent.to_string(context.config));
1940         result.push_str(&arg_str);
1941         result.push('\n');
1942         result.push_str(&indent.to_string(context.config));
1943         result.push(')');
1944     } else {
1945         result.push_str(&arg_str);
1946         if context.config.spaces_within_parens() && fd.inputs.len() > 0 {
1947             result.push(' ')
1948         }
1949         // If the last line of args contains comment, we cannot put the closing paren
1950         // on the same line.
1951         if arg_str
1952             .lines()
1953             .last()
1954             .map_or(false, |last_line| last_line.contains("//"))
1955         {
1956             args_last_line_contains_comment = true;
1957             result.push('\n');
1958             result.push_str(&arg_indent.to_string(context.config));
1959         }
1960         result.push(')');
1961     }
1962
1963     // Return type.
1964     if !ret_str.is_empty() {
1965         let ret_should_indent = match context.config.fn_args_layout() {
1966             // If our args are block layout then we surely must have space.
1967             IndentStyle::Block if put_args_in_block => false,
1968             _ => {
1969                 // If we've already gone multi-line, or the return type would push over the max
1970                 // width, then put the return type on a new line. With the +1 for the signature
1971                 // length an additional space between the closing parenthesis of the argument and
1972                 // the arrow '->' is considered.
1973                 let mut sig_length = result.len() + indent.width() + ret_str_len + 1;
1974
1975                 // If there is no where clause, take into account the space after the return type
1976                 // and the brace.
1977                 if where_clause.predicates.is_empty() {
1978                     sig_length += 2;
1979                 }
1980
1981                 let overlong_sig = sig_length > context.config.max_width();
1982
1983                 (!args_last_line_contains_comment) &&
1984                     (result.contains('\n') || multi_line_ret_str || overlong_sig)
1985             }
1986         };
1987         let ret_indent = if ret_should_indent {
1988             let indent = match context.config.fn_return_indent() {
1989                 ReturnIndent::WithWhereClause => indent + 4,
1990                 // Aligning with non-existent args looks silly.
1991                 _ if arg_str.is_empty() => {
1992                     force_new_line_for_brace = true;
1993                     indent + 4
1994                 }
1995                 // FIXME: we might want to check that using the arg indent
1996                 // doesn't blow our budget, and if it does, then fallback to
1997                 // the where clause indent.
1998                 _ => arg_indent,
1999             };
2000
2001             result.push('\n');
2002             result.push_str(&indent.to_string(context.config));
2003             indent
2004         } else {
2005             result.push(' ');
2006             Indent::new(indent.block_indent, last_line_width(&result))
2007         };
2008
2009         if multi_line_ret_str || ret_should_indent {
2010             // Now that we know the proper indent and width, we need to
2011             // re-layout the return type.
2012             let ret_str = try_opt!(
2013                 fd.output
2014                     .rewrite(context, Shape::indented(ret_indent, context.config))
2015             );
2016             result.push_str(&ret_str);
2017         } else {
2018             result.push_str(&ret_str);
2019         }
2020
2021         // Comment between return type and the end of the decl.
2022         let snippet_lo = fd.output.span().hi;
2023         if where_clause.predicates.is_empty() {
2024             let snippet_hi = span.hi;
2025             let snippet = context.snippet(mk_sp(snippet_lo, snippet_hi));
2026             // Try to preserve the layout of the original snippet.
2027             let original_starts_with_newline = snippet
2028                 .find(|c| c != ' ')
2029                 .map_or(false, |i| snippet[i..].starts_with('\n'));
2030             let original_ends_with_newline = snippet
2031                 .rfind(|c| c != ' ')
2032                 .map_or(false, |i| snippet[i..].ends_with('\n'));
2033             let snippet = snippet.trim();
2034             if !snippet.is_empty() {
2035                 result.push(if original_starts_with_newline {
2036                     '\n'
2037                 } else {
2038                     ' '
2039                 });
2040                 result.push_str(snippet);
2041                 if original_ends_with_newline {
2042                     force_new_line_for_brace = true;
2043                 }
2044             }
2045         } else {
2046             // FIXME it would be nice to catch comments between the return type
2047             // and the where clause, but we don't have a span for the where
2048             // clause.
2049         }
2050     }
2051
2052     let should_compress_where = match context.config.where_density() {
2053         Density::Compressed => !result.contains('\n') || put_args_in_block,
2054         Density::CompressedIfEmpty => !has_body && !result.contains('\n'),
2055         _ => false,
2056     } || (put_args_in_block && ret_str.is_empty());
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) =
2066             rewrite_where_clause(
2067                 context,
2068                 where_clause,
2069                 context.config.fn_brace_style(),
2070                 Shape::legacy(budget, indent),
2071                 Density::Compressed,
2072                 "{",
2073                 !has_braces,
2074                 put_args_in_block && ret_str.is_empty(),
2075                 Some(span.hi),
2076             ) {
2077             if !where_clause_str.contains('\n') {
2078                 if last_line_width(&result) + where_clause_str.len() > context.config.max_width() {
2079                     result.push('\n');
2080                 }
2081
2082                 result.push_str(&where_clause_str);
2083
2084                 force_new_line_for_brace |= last_line_contains_single_line_comment(&result);
2085                 return Some((result, force_new_line_for_brace));
2086             }
2087         }
2088     }
2089
2090     let where_clause_str = try_opt!(rewrite_where_clause(
2091         context,
2092         where_clause,
2093         context.config.fn_brace_style(),
2094         Shape::indented(indent, context.config),
2095         Density::Tall,
2096         "{",
2097         !has_braces,
2098         put_args_in_block && ret_str.is_empty(),
2099         Some(span.hi),
2100     ));
2101
2102     result.push_str(&where_clause_str);
2103
2104     force_new_line_for_brace |= last_line_contains_single_line_comment(&result);
2105     return Some((result, force_new_line_for_brace));
2106 }
2107
2108 fn last_line_contains_single_line_comment(s: &str) -> bool {
2109     s.lines().last().map_or(false, |l| l.contains("//"))
2110 }
2111
2112 fn rewrite_args(
2113     context: &RewriteContext,
2114     args: &[ast::Arg],
2115     explicit_self: Option<&ast::ExplicitSelf>,
2116     one_line_budget: usize,
2117     multi_line_budget: usize,
2118     indent: Indent,
2119     arg_indent: Indent,
2120     span: Span,
2121     variadic: bool,
2122     generics_str_contains_newline: bool,
2123 ) -> Option<String> {
2124     let mut arg_item_strs = try_opt!(
2125         args.iter()
2126             .map(|arg| {
2127                 arg.rewrite(&context, Shape::legacy(multi_line_budget, arg_indent))
2128             })
2129             .collect::<Option<Vec<_>>>()
2130     );
2131
2132     // Account for sugary self.
2133     // FIXME: the comment for the self argument is dropped. This is blocked
2134     // on rust issue #27522.
2135     let min_args = explicit_self
2136         .and_then(|explicit_self| {
2137             rewrite_explicit_self(explicit_self, args, context)
2138         })
2139         .map_or(1, |self_str| {
2140             arg_item_strs[0] = self_str;
2141             2
2142         });
2143
2144     // Comments between args.
2145     let mut arg_items = Vec::new();
2146     if min_args == 2 {
2147         arg_items.push(ListItem::from_str(""));
2148     }
2149
2150     // FIXME(#21): if there are no args, there might still be a comment, but
2151     // without spans for the comment or parens, there is no chance of
2152     // getting it right. You also don't get to put a comment on self, unless
2153     // it is explicit.
2154     if args.len() >= min_args || variadic {
2155         let comment_span_start = if min_args == 2 {
2156             let second_arg_start = if arg_has_pattern(&args[1]) {
2157                 args[1].pat.span.lo
2158             } else {
2159                 args[1].ty.span.lo
2160             };
2161             let reduced_span = mk_sp(span.lo, second_arg_start);
2162
2163             context.codemap.span_after_last(reduced_span, ",")
2164         } else {
2165             span.lo
2166         };
2167
2168         enum ArgumentKind<'a> {
2169             Regular(&'a ast::Arg),
2170             Variadic(BytePos),
2171         }
2172
2173         let variadic_arg = if variadic {
2174             let variadic_span = mk_sp(args.last().unwrap().ty.span.hi, span.hi);
2175             let variadic_start = context.codemap.span_after(variadic_span, "...") - BytePos(3);
2176             Some(ArgumentKind::Variadic(variadic_start))
2177         } else {
2178             None
2179         };
2180
2181         let more_items = itemize_list(
2182             context.codemap,
2183             args[min_args - 1..]
2184                 .iter()
2185                 .map(ArgumentKind::Regular)
2186                 .chain(variadic_arg),
2187             ")",
2188             |arg| match *arg {
2189                 ArgumentKind::Regular(arg) => span_lo_for_arg(arg),
2190                 ArgumentKind::Variadic(start) => start,
2191             },
2192             |arg| match *arg {
2193                 ArgumentKind::Regular(arg) => arg.ty.span.hi,
2194                 ArgumentKind::Variadic(start) => start + BytePos(3),
2195             },
2196             |arg| match *arg {
2197                 ArgumentKind::Regular(..) => None,
2198                 ArgumentKind::Variadic(..) => Some("...".to_owned()),
2199             },
2200             comment_span_start,
2201             span.hi,
2202         );
2203
2204         arg_items.extend(more_items);
2205     }
2206
2207     let fits_in_one_line = !generics_str_contains_newline &&
2208         (arg_items.len() == 0 || arg_items.len() == 1 && arg_item_strs[0].len() <= one_line_budget);
2209
2210     for (item, arg) in arg_items.iter_mut().zip(arg_item_strs) {
2211         item.item = Some(arg);
2212     }
2213
2214     let last_line_ends_with_comment = arg_items
2215         .iter()
2216         .last()
2217         .and_then(|item| item.post_comment.as_ref())
2218         .map_or(false, |s| s.trim().starts_with("//"));
2219
2220     let (indent, trailing_comma, end_with_newline) = match context.config.fn_args_layout() {
2221         IndentStyle::Block if fits_in_one_line => {
2222             (
2223                 indent.block_indent(context.config),
2224                 SeparatorTactic::Never,
2225                 true,
2226             )
2227         }
2228         IndentStyle::Block => {
2229             (
2230                 indent.block_indent(context.config),
2231                 context.config.trailing_comma(),
2232                 true,
2233             )
2234         }
2235         IndentStyle::Visual if last_line_ends_with_comment => {
2236             (arg_indent, context.config.trailing_comma(), true)
2237         }
2238         IndentStyle::Visual => (arg_indent, SeparatorTactic::Never, false),
2239     };
2240
2241     let tactic = definitive_tactic(
2242         &arg_items,
2243         context.config.fn_args_density().to_list_tactic(),
2244         one_line_budget,
2245     );
2246     let budget = match tactic {
2247         DefinitiveListTactic::Horizontal => one_line_budget,
2248         _ => multi_line_budget,
2249     };
2250
2251     debug!("rewrite_args: budget: {}, tactic: {:?}", budget, tactic);
2252
2253     let fmt = ListFormatting {
2254         tactic: tactic,
2255         separator: ",",
2256         trailing_separator: if variadic {
2257             SeparatorTactic::Never
2258         } else {
2259             trailing_comma
2260         },
2261         shape: Shape::legacy(budget, indent),
2262         ends_with_newline: end_with_newline,
2263         config: context.config,
2264     };
2265
2266     write_list(&arg_items, &fmt)
2267 }
2268
2269 fn arg_has_pattern(arg: &ast::Arg) -> bool {
2270     if let ast::PatKind::Ident(_, ident, _) = arg.pat.node {
2271         ident.node != symbol::keywords::Invalid.ident()
2272     } else {
2273         true
2274     }
2275 }
2276
2277 fn compute_budgets_for_args(
2278     context: &RewriteContext,
2279     result: &str,
2280     indent: Indent,
2281     ret_str_len: usize,
2282     newline_brace: bool,
2283     has_braces: bool,
2284 ) -> Option<((usize, usize, Indent))> {
2285     debug!(
2286         "compute_budgets_for_args {} {:?}, {}, {}",
2287         result.len(),
2288         indent,
2289         ret_str_len,
2290         newline_brace
2291     );
2292     // Try keeping everything on the same line.
2293     if !result.contains('\n') {
2294         // 2 = `()`, 3 = `() `, space is before ret_string.
2295         let overhead = if ret_str_len == 0 { 2 } else { 3 };
2296         let mut used_space = indent.width() + result.len() + ret_str_len + overhead;
2297         if has_braces {
2298             if !newline_brace {
2299                 // 2 = `{}`
2300                 used_space += 2;
2301             }
2302         } else {
2303             // 1 = `;`
2304             used_space += 1;
2305         }
2306         let one_line_budget = context
2307             .config
2308             .max_width()
2309             .checked_sub(used_space)
2310             .unwrap_or(0);
2311
2312         if one_line_budget > 0 {
2313             // 4 = "() {".len()
2314             let multi_line_overhead =
2315                 indent.width() + result.len() + if newline_brace { 2 } else { 4 };
2316             let multi_line_budget =
2317                 try_opt!(context.config.max_width().checked_sub(multi_line_overhead));
2318
2319             return Some((
2320                 one_line_budget,
2321                 multi_line_budget,
2322                 indent + result.len() + 1,
2323             ));
2324         }
2325     }
2326
2327     // Didn't work. we must force vertical layout and put args on a newline.
2328     let new_indent = indent.block_indent(context.config);
2329     // Account for `)` and possibly ` {`.
2330     let used_space = new_indent.width() + if ret_str_len == 0 { 1 } else { 3 };
2331     let max_space = try_opt!(context.config.max_width().checked_sub(used_space));
2332     Some((0, max_space, new_indent))
2333 }
2334
2335 fn newline_for_brace(config: &Config, where_clause: &ast::WhereClause) -> bool {
2336     match config.fn_brace_style() {
2337         BraceStyle::AlwaysNextLine => true,
2338         BraceStyle::SameLineWhere if !where_clause.predicates.is_empty() => true,
2339         _ => false,
2340     }
2341 }
2342
2343 fn rewrite_generics(
2344     context: &RewriteContext,
2345     generics: &ast::Generics,
2346     shape: Shape,
2347     span: Span,
2348 ) -> Option<String> {
2349     let g_shape = try_opt!(generics_shape_from_config(context.config, shape, 0));
2350     let one_line_width = shape.width.checked_sub(2).unwrap_or(0);
2351     rewrite_generics_inner(context, generics, g_shape, one_line_width, span).or_else(|| {
2352         rewrite_generics_inner(context, generics, g_shape, 0, span)
2353     })
2354 }
2355
2356 fn rewrite_generics_inner(
2357     context: &RewriteContext,
2358     generics: &ast::Generics,
2359     shape: Shape,
2360     one_line_width: usize,
2361     span: Span,
2362 ) -> Option<String> {
2363     // FIXME: convert bounds to where clauses where they get too big or if
2364     // there is a where clause at all.
2365     let lifetimes: &[_] = &generics.lifetimes;
2366     let tys: &[_] = &generics.ty_params;
2367     if lifetimes.is_empty() && tys.is_empty() {
2368         return Some(String::new());
2369     }
2370
2371     // Strings for the generics.
2372     let lt_strs = lifetimes.iter().map(|lt| lt.rewrite(context, shape));
2373     let ty_strs = tys.iter().map(|ty_param| ty_param.rewrite(context, shape));
2374
2375     // Extract comments between generics.
2376     let lt_spans = lifetimes.iter().map(|l| {
2377         let hi = if l.bounds.is_empty() {
2378             l.lifetime.span.hi
2379         } else {
2380             l.bounds[l.bounds.len() - 1].span.hi
2381         };
2382         mk_sp(l.lifetime.span.lo, hi)
2383     });
2384     let ty_spans = tys.iter().map(span_for_ty_param);
2385
2386     let items = itemize_list(
2387         context.codemap,
2388         lt_spans.chain(ty_spans).zip(lt_strs.chain(ty_strs)),
2389         ">",
2390         |&(sp, _)| sp.lo,
2391         |&(sp, _)| sp.hi,
2392         // FIXME: don't clone
2393         |&(_, ref str)| str.clone(),
2394         context.codemap.span_after(span, "<"),
2395         span.hi,
2396     );
2397     format_generics_item_list(context, items, shape, one_line_width)
2398 }
2399
2400 pub fn generics_shape_from_config(config: &Config, shape: Shape, offset: usize) -> Option<Shape> {
2401     match config.generics_indent() {
2402         IndentStyle::Visual => shape.visual_indent(1 + offset).sub_width(offset + 2),
2403         IndentStyle::Block => {
2404             // 1 = ","
2405             shape
2406                 .block()
2407                 .block_indent(config.tab_spaces())
2408                 .with_max_width(config)
2409                 .sub_width(1)
2410         }
2411     }
2412 }
2413
2414 pub fn format_generics_item_list<I>(
2415     context: &RewriteContext,
2416     items: I,
2417     shape: Shape,
2418     one_line_budget: usize,
2419 ) -> Option<String>
2420 where
2421     I: Iterator<Item = ListItem>,
2422 {
2423     let item_vec = items.collect::<Vec<_>>();
2424
2425     let tactic = definitive_tactic(&item_vec, ListTactic::HorizontalVertical, one_line_budget);
2426     let ends_with_newline = context.config.generics_indent() == IndentStyle::Block &&
2427         tactic == DefinitiveListTactic::Vertical;
2428     let fmt = ListFormatting {
2429         tactic: tactic,
2430         separator: ",",
2431         trailing_separator: if context.config.generics_indent() == IndentStyle::Visual {
2432             SeparatorTactic::Never
2433         } else {
2434             context.config.trailing_comma()
2435         },
2436         shape: shape,
2437         ends_with_newline: ends_with_newline,
2438         config: context.config,
2439     };
2440
2441     let list_str = try_opt!(write_list(&item_vec, &fmt));
2442
2443     Some(wrap_generics_with_angle_brackets(
2444         context,
2445         &list_str,
2446         shape.indent,
2447     ))
2448 }
2449
2450 pub fn wrap_generics_with_angle_brackets(
2451     context: &RewriteContext,
2452     list_str: &str,
2453     list_offset: Indent,
2454 ) -> String {
2455     if context.config.generics_indent() == IndentStyle::Block &&
2456         (list_str.contains('\n') || list_str.ends_with(','))
2457     {
2458         format!(
2459             "<\n{}{}\n{}>",
2460             list_offset.to_string(context.config),
2461             list_str,
2462             list_offset
2463                 .block_unindent(context.config)
2464                 .to_string(context.config)
2465         )
2466     } else if context.config.spaces_within_angle_brackets() {
2467         format!("< {} >", list_str)
2468     } else {
2469         format!("<{}>", list_str)
2470     }
2471 }
2472
2473 fn rewrite_trait_bounds(
2474     context: &RewriteContext,
2475     type_param_bounds: &ast::TyParamBounds,
2476     shape: Shape,
2477 ) -> Option<String> {
2478     let bounds: &[_] = type_param_bounds;
2479
2480     if bounds.is_empty() {
2481         return Some(String::new());
2482     }
2483     let bound_str = try_opt!(
2484         bounds
2485             .iter()
2486             .map(|ty_bound| ty_bound.rewrite(&context, shape))
2487             .collect::<Option<Vec<_>>>()
2488     );
2489     Some(format!(": {}", join_bounds(context, shape, &bound_str)))
2490 }
2491
2492 fn rewrite_where_clause_rfc_style(
2493     context: &RewriteContext,
2494     where_clause: &ast::WhereClause,
2495     shape: Shape,
2496     terminator: &str,
2497     suppress_comma: bool,
2498     // where clause can be kept on the current line.
2499     snuggle: bool,
2500     span_end: Option<BytePos>,
2501 ) -> Option<String> {
2502     let block_shape = shape.block().with_max_width(context.config);
2503
2504     let starting_newline = if snuggle {
2505         " ".to_owned()
2506     } else {
2507         "\n".to_owned() + &block_shape.indent.to_string(context.config)
2508     };
2509
2510     let clause_shape = block_shape.block_indent(context.config.tab_spaces());
2511     // each clause on one line, trailing comma (except if suppress_comma)
2512     let span_start = span_for_where_pred(&where_clause.predicates[0]).lo;
2513     // If we don't have the start of the next span, then use the end of the
2514     // predicates, but that means we miss comments.
2515     let len = where_clause.predicates.len();
2516     let end_of_preds = span_for_where_pred(&where_clause.predicates[len - 1]).hi;
2517     let span_end = span_end.unwrap_or(end_of_preds);
2518     let items = itemize_list(
2519         context.codemap,
2520         where_clause.predicates.iter(),
2521         terminator,
2522         |pred| span_for_where_pred(pred).lo,
2523         |pred| span_for_where_pred(pred).hi,
2524         |pred| pred.rewrite(context, block_shape),
2525         span_start,
2526         span_end,
2527     );
2528     let comma_tactic = if suppress_comma {
2529         SeparatorTactic::Never
2530     } else {
2531         context.config.trailing_comma()
2532     };
2533
2534     let fmt = ListFormatting {
2535         tactic: DefinitiveListTactic::Vertical,
2536         separator: ",",
2537         trailing_separator: comma_tactic,
2538         shape: clause_shape,
2539         ends_with_newline: true,
2540         config: context.config,
2541     };
2542     let preds_str = try_opt!(write_list(&items.collect::<Vec<_>>(), &fmt));
2543
2544     Some(format!(
2545         "{}where\n{}{}",
2546         starting_newline,
2547         clause_shape.indent.to_string(context.config),
2548         preds_str
2549     ))
2550 }
2551
2552 fn rewrite_where_clause(
2553     context: &RewriteContext,
2554     where_clause: &ast::WhereClause,
2555     brace_style: BraceStyle,
2556     shape: Shape,
2557     density: Density,
2558     terminator: &str,
2559     suppress_comma: bool,
2560     snuggle: bool,
2561     span_end: Option<BytePos>,
2562 ) -> Option<String> {
2563     if where_clause.predicates.is_empty() {
2564         return Some(String::new());
2565     }
2566
2567     if context.config.where_style() == Style::Rfc {
2568         return rewrite_where_clause_rfc_style(
2569             context,
2570             where_clause,
2571             shape,
2572             terminator,
2573             suppress_comma,
2574             snuggle,
2575             span_end,
2576         );
2577     }
2578
2579     let extra_indent = Indent::new(context.config.tab_spaces(), 0);
2580
2581     let offset = match context.config.where_pred_indent() {
2582         IndentStyle::Block => shape.indent + extra_indent.block_indent(context.config),
2583         // 6 = "where ".len()
2584         IndentStyle::Visual => shape.indent + extra_indent + 6,
2585     };
2586     // FIXME: if where_pred_indent != Visual, then the budgets below might
2587     // be out by a char or two.
2588
2589     let budget = context.config.max_width() - offset.width();
2590     let span_start = span_for_where_pred(&where_clause.predicates[0]).lo;
2591     // If we don't have the start of the next span, then use the end of the
2592     // predicates, but that means we miss comments.
2593     let len = where_clause.predicates.len();
2594     let end_of_preds = span_for_where_pred(&where_clause.predicates[len - 1]).hi;
2595     let span_end = span_end.unwrap_or(end_of_preds);
2596     let items = itemize_list(
2597         context.codemap,
2598         where_clause.predicates.iter(),
2599         terminator,
2600         |pred| span_for_where_pred(pred).lo,
2601         |pred| span_for_where_pred(pred).hi,
2602         |pred| pred.rewrite(context, Shape::legacy(budget, offset)),
2603         span_start,
2604         span_end,
2605     );
2606     let item_vec = items.collect::<Vec<_>>();
2607     // FIXME: we don't need to collect here if the where_layout isn't
2608     // HorizontalVertical.
2609     let tactic = definitive_tactic(&item_vec, context.config.where_layout(), budget);
2610
2611     let mut comma_tactic = context.config.trailing_comma();
2612     // Kind of a hack because we don't usually have trailing commas in where clauses.
2613     if comma_tactic == SeparatorTactic::Vertical || suppress_comma {
2614         comma_tactic = SeparatorTactic::Never;
2615     }
2616
2617     let fmt = ListFormatting {
2618         tactic: tactic,
2619         separator: ",",
2620         trailing_separator: comma_tactic,
2621         shape: Shape::legacy(budget, offset),
2622         ends_with_newline: true,
2623         config: context.config,
2624     };
2625     let preds_str = try_opt!(write_list(&item_vec, &fmt));
2626
2627     let end_length = if terminator == "{" {
2628         // If the brace is on the next line we don't need to count it otherwise it needs two
2629         // characters " {"
2630         match brace_style {
2631             BraceStyle::AlwaysNextLine |
2632             BraceStyle::SameLineWhere => 0,
2633             BraceStyle::PreferSameLine => 2,
2634         }
2635     } else if terminator == "=" {
2636         2
2637     } else {
2638         terminator.len()
2639     };
2640     if density == Density::Tall || preds_str.contains('\n') ||
2641         shape.indent.width() + " where ".len() + preds_str.len() + end_length > shape.width
2642     {
2643         Some(format!(
2644             "\n{}where {}",
2645             (shape.indent + extra_indent).to_string(context.config),
2646             preds_str
2647         ))
2648     } else {
2649         Some(format!(" where {}", preds_str))
2650     }
2651 }
2652
2653 fn format_header(item_name: &str, ident: ast::Ident, vis: &ast::Visibility) -> String {
2654     format!("{}{}{}", format_visibility(vis), item_name, ident)
2655 }
2656
2657 fn format_generics(
2658     context: &RewriteContext,
2659     generics: &ast::Generics,
2660     opener: &str,
2661     terminator: &str,
2662     brace_style: BraceStyle,
2663     force_same_line_brace: bool,
2664     offset: Indent,
2665     span: Span,
2666     used_width: usize,
2667 ) -> Option<String> {
2668     let shape = Shape::legacy(context.budget(used_width + offset.width()), offset);
2669     let mut result = try_opt!(rewrite_generics(context, generics, shape, span));
2670
2671     if !generics.where_clause.predicates.is_empty() || result.contains('\n') {
2672         let budget = try_opt!(
2673             context
2674                 .config
2675                 .max_width()
2676                 .checked_sub(last_line_width(&result))
2677         );
2678         let where_clause_str = try_opt!(rewrite_where_clause(
2679             context,
2680             &generics.where_clause,
2681             brace_style,
2682             Shape::legacy(budget, offset.block_only()),
2683             Density::Tall,
2684             terminator,
2685             false,
2686             trimmed_last_line_width(&result) == 1,
2687             Some(span.hi),
2688         ));
2689         result.push_str(&where_clause_str);
2690         let same_line_brace = force_same_line_brace ||
2691             (generics.where_clause.predicates.is_empty() && trimmed_last_line_width(&result) == 1);
2692         if !same_line_brace &&
2693             (brace_style == BraceStyle::SameLineWhere ||
2694                 brace_style == BraceStyle::AlwaysNextLine)
2695         {
2696             result.push('\n');
2697             result.push_str(&offset.block_only().to_string(context.config));
2698         } else {
2699             result.push(' ');
2700         }
2701         result.push_str(opener);
2702     } else {
2703         if force_same_line_brace || trimmed_last_line_width(&result) == 1 ||
2704             brace_style != BraceStyle::AlwaysNextLine
2705         {
2706             result.push(' ');
2707         } else {
2708             result.push('\n');
2709             result.push_str(&offset.block_only().to_string(context.config));
2710         }
2711         result.push_str(opener);
2712     }
2713
2714     Some(result)
2715 }