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 use lists::{write_list, itemize_list, ListItem, ListFormatting, SeparatorTactic,
  18             DefinitiveListTactic, ListTactic, definitive_tactic, format_item_list};
  19 use expr::{is_empty_block, is_simple_block_stmt, rewrite_assign_rhs, type_annotation_separator};
  20 use comment::{FindUncommented, contains_comment};
  21 use visitor::FmtVisitor;
  22 use rewrite::{Rewrite, RewriteContext};
  23 use config::{Config, BlockIndentStyle, Density, ReturnIndent, BraceStyle, FnArgLayoutStyle, Style};
  24 use itertools::Itertools;
  25
  26 use syntax::{ast, abi, codemap, ptr, symbol};
  27 use syntax::codemap::{Span, BytePos, mk_sp};
  28 use syntax::ast::ImplItem;
  29
  30 // Statements of the form
  31 // let pat: ty = init;
  32 impl Rewrite for ast::Local {
  33     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
  34         debug!("Local::rewrite {:?} {} {:?}",
  35                self,
  36                shape.width,
  37                shape.indent);
  38         let mut result = "let ".to_owned();
  39         let pattern_offset = shape.indent + result.len();
  40         // 1 = ;
  41         let pattern_width = try_opt!(shape.width.checked_sub(pattern_offset.width() + 1));
  42
  43         let pat_str = try_opt!(self.pat.rewrite(&context,
  44                                                 Shape::legacy(pattern_width, pattern_offset)));
  45         result.push_str(&pat_str);
  46
  47         // String that is placed within the assignment pattern and expression.
  48         let infix = {
  49             let mut infix = String::new();
  50
  51             if let Some(ref ty) = self.ty {
  52                 let separator = type_annotation_separator(context.config);
  53                 let indent = shape.indent + last_line_width(&result) + separator.len();
  54                 // 1 = ;
  55                 let budget = try_opt!(shape.width.checked_sub(indent.width() + 1));
  56                 let rewrite = try_opt!(ty.rewrite(context, Shape::legacy(budget, indent)));
  57
  58                 infix.push_str(separator);
  59                 infix.push_str(&rewrite);
  60             }
  61
  62             if self.init.is_some() {
  63                 infix.push_str(" =");
  64             }
  65
  66             infix
  67         };
  68
  69         result.push_str(&infix);
  70
  71         if let Some(ref ex) = self.init {
  72             // 1 = trailing semicolon;
  73             let budget = try_opt!(shape.width.checked_sub(shape.indent.block_only().width() + 1));
  74
  75             result = try_opt!(rewrite_assign_rhs(&context,
  76                                                  result,
  77                                                  ex,
  78                                                  Shape::legacy(budget, shape.indent.block_only())));
  79         }
  80
  81         result.push(';');
  82         Some(result)
  83     }
  84 }
  85
  86 // TODO convert to using rewrite style rather than visitor
  87 // TODO format modules in this style
  88 #[allow(dead_code)]
  89 struct Item<'a> {
  90     keyword: &'static str,
  91     abi: String,
  92     vis: Option<&'a ast::Visibility>,
  93     body: Vec<BodyElement<'a>>,
  94     span: Span,
  95 }
  96
  97 impl<'a> Item<'a> {
  98     fn from_foreign_mod(fm: &'a ast::ForeignMod, span: Span, config: &Config) -> Item<'a> {
  99         let abi = if fm.abi == abi::Abi::C && !config.force_explicit_abi {
 100             "extern".into()
 101         } else {
 102             format!("extern {}", fm.abi)
 103         };
 104         Item {
 105             keyword: "",
 106             abi: abi,
 107             vis: None,
 108             body: fm.items
 109                 .iter()
 110                 .map(|i| BodyElement::ForeignItem(i))
 111                 .collect(),
 112             span: span,
 113         }
 114     }
 115 }
 116
 117 enum BodyElement<'a> {
 118     // Stmt(&'a ast::Stmt),
 119     // Field(&'a ast::Field),
 120     // Variant(&'a ast::Variant),
 121     // Item(&'a ast::Item),
 122     ForeignItem(&'a ast::ForeignItem),
 123 }
 124
 125 impl<'a> FmtVisitor<'a> {
 126     fn format_item(&mut self, item: Item) {
 127         self.buffer.push_str(&item.abi);
 128         self.buffer.push_str(" ");
 129
 130         let snippet = self.snippet(item.span);
 131         let brace_pos = snippet.find_uncommented("{").unwrap();
 132
 133         self.buffer.push_str("{");
 134         if !item.body.is_empty() || contains_comment(&snippet[brace_pos..]) {
 135             // FIXME: this skips comments between the extern keyword and the opening
 136             // brace.
 137             self.last_pos = item.span.lo + BytePos(brace_pos as u32 + 1);
 138             self.block_indent = self.block_indent.block_indent(self.config);
 139
 140             if item.body.is_empty() {
 141                 self.format_missing_no_indent(item.span.hi - BytePos(1));
 142                 self.block_indent = self.block_indent.block_unindent(self.config);
 143
 144                 self.buffer.push_str(&self.block_indent.to_string(self.config));
 145             } else {
 146                 for item in &item.body {
 147                     self.format_body_element(item);
 148                 }
 149
 150                 self.block_indent = self.block_indent.block_unindent(self.config);
 151                 self.format_missing_with_indent(item.span.hi - BytePos(1));
 152             }
 153         }
 154
 155         self.buffer.push_str("}");
 156         self.last_pos = item.span.hi;
 157     }
 158
 159     fn format_body_element(&mut self, element: &BodyElement) {
 160         match *element {
 161             BodyElement::ForeignItem(ref item) => self.format_foreign_item(item),
 162         }
 163     }
 164
 165     pub fn format_foreign_mod(&mut self, fm: &ast::ForeignMod, span: Span) {
 166         let item = Item::from_foreign_mod(fm, span, self.config);
 167         self.format_item(item);
 168     }
 169
 170     fn format_foreign_item(&mut self, item: &ast::ForeignItem) {
 171         self.format_missing_with_indent(item.span.lo);
 172         // Drop semicolon or it will be interpreted as comment.
 173         // FIXME: this may be a faulty span from libsyntax.
 174         let span = mk_sp(item.span.lo, item.span.hi - BytePos(1));
 175
 176         match item.node {
 177             ast::ForeignItemKind::Fn(ref fn_decl, ref generics) => {
 178                 let indent = self.block_indent;
 179                 let rewrite = rewrite_fn_base(&self.get_context(),
 180                                               indent,
 181                                               item.ident,
 182                                               fn_decl,
 183                                               generics,
 184                                               ast::Unsafety::Normal,
 185                                               ast::Constness::NotConst,
 186                                               ast::Defaultness::Final,
 187                                               // These are not actually rust functions,
 188                                               // but we format them as such.
 189                                               abi::Abi::Rust,
 190                                               &item.vis,
 191                                               span,
 192                                               false,
 193                                               false);
 194
 195                 match rewrite {
 196                     Some((new_fn, _)) => {
 197                         self.buffer.push_str(&new_fn);
 198                         self.buffer.push_str(";");
 199                     }
 200                     None => self.format_missing(item.span.hi),
 201                 }
 202             }
 203             ast::ForeignItemKind::Static(ref ty, is_mutable) => {
 204                 // FIXME(#21): we're dropping potential comments in between the
 205                 // function keywords here.
 206                 let vis = format_visibility(&item.vis);
 207                 let mut_str = if is_mutable { "mut " } else { "" };
 208                 let prefix = format!("{}static {}{}: ", vis, mut_str, item.ident);
 209                 let offset = self.block_indent + prefix.len();
 210                 // 1 = ;
 211                 let width = self.config.max_width - offset.width() - 1;
 212                 let rewrite = ty.rewrite(&self.get_context(), Shape::legacy(width, offset));
 213
 214                 match rewrite {
 215                     Some(result) => {
 216                         self.buffer.push_str(&prefix);
 217                         self.buffer.push_str(&result);
 218                         self.buffer.push_str(";");
 219                     }
 220                     None => self.format_missing(item.span.hi),
 221                 }
 222             }
 223         }
 224
 225         self.last_pos = item.span.hi;
 226     }
 227
 228     pub fn rewrite_fn(&mut self,
 229                       indent: Indent,
 230                       ident: ast::Ident,
 231                       fd: &ast::FnDecl,
 232                       generics: &ast::Generics,
 233                       unsafety: ast::Unsafety,
 234                       constness: ast::Constness,
 235                       defaultness: ast::Defaultness,
 236                       abi: abi::Abi,
 237                       vis: &ast::Visibility,
 238                       span: Span,
 239                       block: &ast::Block)
 240                       -> Option<String> {
 241         let mut newline_brace = newline_for_brace(self.config, &generics.where_clause);
 242         let context = self.get_context();
 243
 244         let block_snippet = self.snippet(codemap::mk_sp(block.span.lo, block.span.hi));
 245         let has_body = !block_snippet[1..block_snippet.len() - 1].trim().is_empty() ||
 246                        !context.config.fn_empty_single_line;
 247
 248         let (mut result, force_newline_brace) = try_opt!(rewrite_fn_base(&context,
 249                                                                          indent,
 250                                                                          ident,
 251                                                                          fd,
 252                                                                          generics,
 253                                                                          unsafety,
 254                                                                          constness,
 255                                                                          defaultness,
 256                                                                          abi,
 257                                                                          vis,
 258                                                                          span,
 259                                                                          newline_brace,
 260                                                                          has_body));
 261
 262         if self.config.fn_brace_style != BraceStyle::AlwaysNextLine && !result.contains('\n') {
 263             newline_brace = false;
 264         } else if force_newline_brace {
 265             newline_brace = true;
 266         }
 267
 268         // Prepare for the function body by possibly adding a newline and
 269         // indent.
 270         // FIXME we'll miss anything between the end of the signature and the
 271         // start of the body, but we need more spans from the compiler to solve
 272         // this.
 273         if newline_brace {
 274             result.push('\n');
 275             result.push_str(&indent.to_string(self.config));
 276         } else {
 277             result.push(' ');
 278         }
 279
 280         self.single_line_fn(&result, block).or_else(|| Some(result))
 281     }
 282
 283     pub fn rewrite_required_fn(&mut self,
 284                                indent: Indent,
 285                                ident: ast::Ident,
 286                                sig: &ast::MethodSig,
 287                                span: Span)
 288                                -> Option<String> {
 289         // Drop semicolon or it will be interpreted as comment.
 290         let span = mk_sp(span.lo, span.hi - BytePos(1));
 291         let context = self.get_context();
 292
 293         let (mut result, _) = try_opt!(rewrite_fn_base(&context,
 294                                                        indent,
 295                                                        ident,
 296                                                        &sig.decl,
 297                                                        &sig.generics,
 298                                                        sig.unsafety,
 299                                                        sig.constness.node,
 300                                                        ast::Defaultness::Final,
 301                                                        sig.abi,
 302                                                        &ast::Visibility::Inherited,
 303                                                        span,
 304                                                        false,
 305                                                        false));
 306
 307         // Re-attach semicolon
 308         result.push(';');
 309
 310         Some(result)
 311     }
 312
 313     fn single_line_fn(&self, fn_str: &str, block: &ast::Block) -> Option<String> {
 314         if fn_str.contains('\n') {
 315             return None;
 316         }
 317
 318         let codemap = self.get_context().codemap;
 319
 320         if self.config.fn_empty_single_line && is_empty_block(block, codemap) &&
 321            self.block_indent.width() + fn_str.len() + 2 <= self.config.max_width {
 322             return Some(format!("{}{{}}", fn_str));
 323         }
 324
 325         if self.config.fn_single_line && is_simple_block_stmt(block, codemap) {
 326             let rewrite = {
 327                 if let Some(ref stmt) = block.stmts.first() {
 328                     match stmt_expr(stmt) {
 329                         Some(e) => {
 330                             let suffix = if semicolon_for_expr(e) { ";" } else { "" };
 331
 332                             e.rewrite(&self.get_context(),
 333                                          Shape::legacy(self.config.max_width -
 334                                                        self.block_indent.width(),
 335                                                        self.block_indent))
 336                                 .map(|s| s + suffix)
 337                                 .or_else(|| Some(self.snippet(e.span)))
 338                         }
 339                         None => {
 340                             stmt.rewrite(&self.get_context(),
 341                                          Shape::legacy(self.config.max_width -
 342                                                        self.block_indent.width(),
 343                                                        self.block_indent))
 344                         }
 345                     }
 346                 } else {
 347                     None
 348                 }
 349             };
 350
 351             if let Some(res) = rewrite {
 352                 let width = self.block_indent.width() + fn_str.len() + res.len() + 4;
 353                 if !res.contains('\n') && width <= self.config.max_width {
 354                     return Some(format!("{}{{ {} }}", fn_str, res));
 355                 }
 356             }
 357         }
 358
 359         None
 360     }
 361
 362     pub fn visit_enum(&mut self,
 363                       ident: ast::Ident,
 364                       vis: &ast::Visibility,
 365                       enum_def: &ast::EnumDef,
 366                       generics: &ast::Generics,
 367                       span: Span) {
 368         self.buffer.push_str(&format_header("enum ", ident, vis));
 369
 370         let enum_snippet = self.snippet(span);
 371         let brace_pos = enum_snippet.find_uncommented("{").unwrap();
 372         let body_start = span.lo + BytePos(brace_pos as u32 + 1);
 373         let generics_str = format_generics(&self.get_context(),
 374                                            generics,
 375                                            "{",
 376                                            "{",
 377                                            self.config.item_brace_style,
 378                                            enum_def.variants.is_empty(),
 379                                            self.block_indent,
 380                                            self.block_indent.block_indent(self.config),
 381                                            mk_sp(span.lo, body_start))
 382                 .unwrap();
 383         self.buffer.push_str(&generics_str);
 384
 385         self.last_pos = body_start;
 386
 387         self.block_indent = self.block_indent.block_indent(self.config);
 388         let variant_list = self.format_variant_list(enum_def, body_start, span.hi - BytePos(1));
 389         match variant_list {
 390             Some(ref body_str) => self.buffer.push_str(body_str),
 391             None => {
 392                 if contains_comment(&enum_snippet[brace_pos..]) {
 393                     self.format_missing_no_indent(span.hi - BytePos(1))
 394                 } else {
 395                     self.format_missing(span.hi - BytePos(1))
 396                 }
 397             }
 398         }
 399         self.block_indent = self.block_indent.block_unindent(self.config);
 400
 401         if variant_list.is_some() || contains_comment(&enum_snippet[brace_pos..]) {
 402             self.buffer.push_str(&self.block_indent.to_string(self.config));
 403         }
 404         self.buffer.push_str("}");
 405         self.last_pos = span.hi;
 406     }
 407
 408     // Format the body of an enum definition
 409     fn format_variant_list(&self,
 410                            enum_def: &ast::EnumDef,
 411                            body_lo: BytePos,
 412                            body_hi: BytePos)
 413                            -> Option<String> {
 414         if enum_def.variants.is_empty() {
 415             return None;
 416         }
 417         let mut result = String::with_capacity(1024);
 418         result.push('\n');
 419         let indentation = self.block_indent.to_string(self.config);
 420         result.push_str(&indentation);
 421
 422         let items = itemize_list(self.codemap,
 423                                  enum_def.variants.iter(),
 424                                  "}",
 425                                  |f| if !f.node.attrs.is_empty() {
 426                                      f.node.attrs[0].span.lo
 427                                  } else {
 428                                      f.span.lo
 429                                  },
 430                                  |f| f.span.hi,
 431                                  |f| self.format_variant(f),
 432                                  body_lo,
 433                                  body_hi);
 434
 435         let budget = self.config.max_width - self.block_indent.width() - 2;
 436         let fmt = ListFormatting {
 437             tactic: DefinitiveListTactic::Vertical,
 438             separator: ",",
 439             trailing_separator: self.config.trailing_comma,
 440             shape: Shape::legacy(budget, self.block_indent),
 441             ends_with_newline: true,
 442             config: self.config,
 443         };
 444
 445         let list = try_opt!(write_list(items, &fmt));
 446         result.push_str(&list);
 447         result.push('\n');
 448         Some(result)
 449     }
 450
 451     // Variant of an enum.
 452     fn format_variant(&self, field: &ast::Variant) -> Option<String> {
 453         if contains_skip(&field.node.attrs) {
 454             let lo = field.node.attrs[0].span.lo;
 455             let span = mk_sp(lo, field.span.hi);
 456             return Some(self.snippet(span));
 457         }
 458
 459         let indent = self.block_indent;
 460         let mut result = try_opt!(field.node.attrs.rewrite(&self.get_context(),
 461                                                            Shape::legacy(self.config.max_width -
 462                                                                          indent.width(),
 463                                                                          indent)));
 464         if !result.is_empty() {
 465             result.push('\n');
 466             result.push_str(&indent.to_string(self.config));
 467         }
 468
 469         let context = self.get_context();
 470         let variant_body = match field.node.data {
 471             ast::VariantData::Tuple(..) |
 472             ast::VariantData::Struct(..) => {
 473                 // FIXME: Should limit the width, as we have a trailing comma
 474                 format_struct(&context,
 475                               "",
 476                               field.node.name,
 477                               &ast::Visibility::Inherited,
 478                               &field.node.data,
 479                               None,
 480                               field.span,
 481                               indent,
 482                               Some(self.config.struct_variant_width))
 483             }
 484             ast::VariantData::Unit(..) => {
 485                 let tag = if let Some(ref expr) = field.node.disr_expr {
 486                     format!("{} = {}", field.node.name, self.snippet(expr.span))
 487                 } else {
 488                     field.node.name.to_string()
 489                 };
 490
 491                 wrap_str(tag,
 492                          self.config.max_width,
 493                          Shape::legacy(self.config.max_width - indent.width(), indent))
 494             }
 495         };
 496
 497         if let Some(variant_str) = variant_body {
 498             result.push_str(&variant_str);
 499             Some(result)
 500         } else {
 501             None
 502         }
 503     }
 504 }
 505
 506 pub fn format_impl(context: &RewriteContext, item: &ast::Item, offset: Indent) -> Option<String> {
 507     if let ast::ItemKind::Impl(_, _, ref generics, ref trait_ref, _, ref items) = item.node {
 508         let mut result = String::new();
 509         // First try to format the ref and type without a split at the 'for'.
 510         let mut ref_and_type = try_opt!(format_impl_ref_and_type(context, item, offset, false));
 511
 512         // If there is a line break present in the first result format it again
 513         // with a split at the 'for'. Skip this if there is no trait ref and
 514         // therefore no 'for'.
 515         if ref_and_type.contains('\n') && trait_ref.is_some() {
 516             ref_and_type = try_opt!(format_impl_ref_and_type(context, item, offset, true));
 517         }
 518         result.push_str(&ref_and_type);
 519
 520         let where_budget = try_opt!(context.config.max_width.checked_sub(last_line_width(&result)));
 521         let where_clause_str = try_opt!(rewrite_where_clause(context,
 522                                                              &generics.where_clause,
 523                                                              context.config.item_brace_style,
 524                                                              Shape::legacy(where_budget,
 525                                                                            offset.block_only()),
 526                                                              context.config.where_density,
 527                                                              "{",
 528                                                              false,
 529                                                              false,
 530                                                              None));
 531
 532         if try_opt!(is_impl_single_line(context, &items, &result, &where_clause_str, &item)) {
 533             result.push_str(&where_clause_str);
 534             if where_clause_str.contains('\n') {
 535                 let white_space = offset.to_string(context.config);
 536                 result.push_str(&format!("\n{}{{\n{}}}", &white_space, &white_space));
 537             } else {
 538                 result.push_str(" {}");
 539             }
 540             return Some(result);
 541         }
 542
 543         if !where_clause_str.is_empty() && !where_clause_str.contains('\n') {
 544             result.push('\n');
 545             let width = offset.block_indent + context.config.tab_spaces - 1;
 546             let where_indent = Indent::new(0, width);
 547             result.push_str(&where_indent.to_string(context.config));
 548         }
 549         result.push_str(&where_clause_str);
 550
 551         match context.config.item_brace_style {
 552             BraceStyle::AlwaysNextLine => {
 553                 result.push('\n');
 554                 result.push_str(&offset.to_string(context.config));
 555             }
 556             BraceStyle::PreferSameLine => result.push(' '),
 557             BraceStyle::SameLineWhere => {
 558                 if !where_clause_str.is_empty() {
 559                     result.push('\n');
 560                     result.push_str(&offset.to_string(context.config));
 561                 } else {
 562                     result.push(' ');
 563                 }
 564             }
 565         }
 566
 567         result.push('{');
 568
 569         let snippet = context.snippet(item.span);
 570         let open_pos = try_opt!(snippet.find_uncommented("{")) + 1;
 571
 572         if !items.is_empty() || contains_comment(&snippet[open_pos..]) {
 573             let mut visitor = FmtVisitor::from_codemap(context.parse_session, context.config);
 574             visitor.block_indent = offset.block_only().block_indent(context.config);
 575             visitor.last_pos = item.span.lo + BytePos(open_pos as u32);
 576
 577             for item in items {
 578                 visitor.visit_impl_item(item);
 579             }
 580
 581             visitor.format_missing(item.span.hi - BytePos(1));
 582
 583             let inner_indent_str = visitor.block_indent.to_string(context.config);
 584             let outer_indent_str = offset.block_only().to_string(context.config);
 585
 586             result.push('\n');
 587             result.push_str(&inner_indent_str);
 588             result.push_str(trim_newlines(visitor.buffer.to_string().trim()));
 589             result.push('\n');
 590             result.push_str(&outer_indent_str);
 591         }
 592
 593         if result.chars().last().unwrap() == '{' {
 594             result.push('\n');
 595             result.push_str(&offset.to_string(context.config));
 596         }
 597         result.push('}');
 598
 599         Some(result)
 600     } else {
 601         unreachable!();
 602     }
 603 }
 604
 605 fn is_impl_single_line(context: &RewriteContext,
 606                        items: &[ImplItem],
 607                        result: &str,
 608                        where_clause_str: &str,
 609                        item: &ast::Item)
 610                        -> Option<bool> {
 611     let snippet = context.snippet(item.span);
 612     let open_pos = try_opt!(snippet.find_uncommented("{")) + 1;
 613
 614     Some(context.config.impl_empty_single_line && items.is_empty() &&
 615          result.len() + where_clause_str.len() <= context.config.max_width &&
 616          !contains_comment(&snippet[open_pos..]))
 617 }
 618
 619 fn format_impl_ref_and_type(context: &RewriteContext,
 620                             item: &ast::Item,
 621                             offset: Indent,
 622                             split_at_for: bool)
 623                             -> Option<String> {
 624     if let ast::ItemKind::Impl(unsafety, polarity, ref generics, ref trait_ref, ref self_ty, _) =
 625         item.node {
 626         let mut result = String::new();
 627
 628         result.push_str(&*format_visibility(&item.vis));
 629         result.push_str(format_unsafety(unsafety));
 630         result.push_str("impl");
 631
 632         let lo = context.codemap.span_after(item.span, "impl");
 633         let hi = match *trait_ref {
 634             Some(ref tr) => tr.path.span.lo,
 635             None => self_ty.span.lo,
 636         };
 637         let generics_str = try_opt!(rewrite_generics(context,
 638                                                      generics,
 639                                                      Shape::legacy(context.config.max_width,
 640                                                                    offset),
 641                                                      offset + result.len(),
 642                                                      mk_sp(lo, hi)));
 643         result.push_str(&generics_str);
 644
 645         if polarity == ast::ImplPolarity::Negative {
 646             result.push_str(" !");
 647         }
 648         if let Some(ref trait_ref) = *trait_ref {
 649             if polarity != ast::ImplPolarity::Negative {
 650                 result.push_str(" ");
 651             }
 652             let budget = try_opt!(context.config.max_width.checked_sub(result.len()));
 653             let indent = offset + result.len();
 654             result.push_str(&*try_opt!(trait_ref.rewrite(context, Shape::legacy(budget, indent))));
 655
 656             if split_at_for {
 657                 result.push('\n');
 658
 659                 // Add indentation of one additional tab.
 660                 let width = offset.block_indent + context.config.tab_spaces;
 661                 let for_indent = Indent::new(0, width);
 662                 result.push_str(&for_indent.to_string(context.config));
 663
 664                 result.push_str("for");
 665             } else {
 666                 result.push_str(" for");
 667             }
 668         }
 669
 670         let mut used_space = last_line_width(&result);
 671         if generics.where_clause.predicates.is_empty() {
 672             // If there is no where clause adapt budget for type formatting to take space and curly
 673             // brace into account.
 674             match context.config.item_brace_style {
 675                 BraceStyle::AlwaysNextLine => {}
 676                 BraceStyle::PreferSameLine => used_space += 2,
 677                 BraceStyle::SameLineWhere => used_space += 2,
 678             }
 679         }
 680
 681         // 1 = space before the type.
 682         let budget = try_opt!(context.config.max_width.checked_sub(used_space + 1));
 683         let indent = offset + result.len() + 1;
 684         let self_ty_str = self_ty.rewrite(context, Shape::legacy(budget, indent));
 685         if let Some(self_ty_str) = self_ty_str {
 686             result.push_str(" ");
 687             result.push_str(&self_ty_str);
 688             return Some(result);
 689         }
 690
 691         // Can't fit the self type on what's left of the line, so start a new one.
 692         let indent = offset.block_indent(context.config);
 693         result.push_str(&format!("\n{}", indent.to_string(context.config)));
 694         let budget = try_opt!(context.config.max_width.checked_sub(indent.width()));
 695         result.push_str(&*try_opt!(self_ty.rewrite(context, Shape::legacy(budget, indent))));
 696         Some(result)
 697     } else {
 698         unreachable!();
 699     }
 700 }
 701
 702 pub fn format_struct(context: &RewriteContext,
 703                      item_name: &str,
 704                      ident: ast::Ident,
 705                      vis: &ast::Visibility,
 706                      struct_def: &ast::VariantData,
 707                      generics: Option<&ast::Generics>,
 708                      span: Span,
 709                      offset: Indent,
 710                      one_line_width: Option<usize>)
 711                      -> Option<String> {
 712     match *struct_def {
 713         ast::VariantData::Unit(..) => Some(format_unit_struct(item_name, ident, vis)),
 714         ast::VariantData::Tuple(ref fields, _) => {
 715             format_tuple_struct(context,
 716                                 item_name,
 717                                 ident,
 718                                 vis,
 719                                 fields,
 720                                 generics,
 721                                 span,
 722                                 offset)
 723         }
 724         ast::VariantData::Struct(ref fields, _) => {
 725             format_struct_struct(context,
 726                                  item_name,
 727                                  ident,
 728                                  vis,
 729                                  fields,
 730                                  generics,
 731                                  span,
 732                                  offset,
 733                                  one_line_width)
 734         }
 735     }
 736 }
 737
 738 pub fn format_trait(context: &RewriteContext, item: &ast::Item, offset: Indent) -> Option<String> {
 739     if let ast::ItemKind::Trait(unsafety, ref generics, ref type_param_bounds, ref trait_items) =
 740         item.node {
 741         let mut result = String::new();
 742         let header = format!("{}{}trait {}",
 743                              format_visibility(&item.vis),
 744                              format_unsafety(unsafety),
 745                              item.ident);
 746
 747         result.push_str(&header);
 748
 749         let body_lo = context.codemap.span_after(item.span, "{");
 750
 751         let generics_str = try_opt!(rewrite_generics(context,
 752                                                      generics,
 753                                                      Shape::legacy(context.config.max_width,
 754                                                                    offset),
 755                                                      offset + result.len(),
 756                                                      mk_sp(item.span.lo, body_lo)));
 757         result.push_str(&generics_str);
 758
 759         let trait_bound_str =
 760             try_opt!(rewrite_trait_bounds(context,
 761                                           type_param_bounds,
 762                                           Shape::legacy(context.config.max_width, offset)));
 763         // If the trait, generics, and trait bound cannot fit on the same line,
 764         // put the trait bounds on an indented new line
 765         if offset.width() + last_line_width(&result) + trait_bound_str.len() >
 766            context.config.ideal_width {
 767             result.push('\n');
 768             let trait_indent = offset.block_only().block_indent(context.config);
 769             result.push_str(&trait_indent.to_string(context.config));
 770         }
 771         result.push_str(&trait_bound_str);
 772
 773         let has_body = !trait_items.is_empty();
 774
 775         let where_density =
 776             if (context.config.where_density == Density::Compressed &&
 777                 (!result.contains('\n') ||
 778                  context.config.fn_args_layout == FnArgLayoutStyle::Block)) ||
 779                (context.config.fn_args_layout == FnArgLayoutStyle::Block && result.is_empty()) ||
 780                (context.config.where_density == Density::CompressedIfEmpty && !has_body &&
 781                 !result.contains('\n')) {
 782                 Density::Compressed
 783             } else {
 784                 Density::Tall
 785             };
 786
 787         let where_budget = try_opt!(context.config.max_width.checked_sub(last_line_width(&result)));
 788         let where_clause_str = try_opt!(rewrite_where_clause(context,
 789                                                              &generics.where_clause,
 790                                                              context.config.item_brace_style,
 791                                                              Shape::legacy(where_budget,
 792                                                                            offset.block_only()),
 793                                                              where_density,
 794                                                              "{",
 795                                                              !has_body,
 796                                                              false,
 797                                                              None));
 798         // If the where clause cannot fit on the same line,
 799         // put the where clause on a new line
 800         if !where_clause_str.contains('\n') &&
 801            last_line_width(&result) + where_clause_str.len() + offset.width() >
 802            context.config.ideal_width {
 803             result.push('\n');
 804             let width = offset.block_indent + context.config.tab_spaces - 1;
 805             let where_indent = Indent::new(0, width);
 806             result.push_str(&where_indent.to_string(context.config));
 807         }
 808         result.push_str(&where_clause_str);
 809
 810         match context.config.item_brace_style {
 811             BraceStyle::AlwaysNextLine => {
 812                 result.push('\n');
 813                 result.push_str(&offset.to_string(context.config));
 814             }
 815             BraceStyle::PreferSameLine => result.push(' '),
 816             BraceStyle::SameLineWhere => {
 817                 if !where_clause_str.is_empty() &&
 818                    (!trait_items.is_empty() || result.contains('\n')) {
 819                     result.push('\n');
 820                     result.push_str(&offset.to_string(context.config));
 821                 } else {
 822                     result.push(' ');
 823                 }
 824             }
 825         }
 826         result.push('{');
 827
 828         let snippet = context.snippet(item.span);
 829         let open_pos = try_opt!(snippet.find_uncommented("{")) + 1;
 830
 831         if !trait_items.is_empty() || contains_comment(&snippet[open_pos..]) {
 832             let mut visitor = FmtVisitor::from_codemap(context.parse_session, context.config);
 833             visitor.block_indent = offset.block_only().block_indent(context.config);
 834             visitor.last_pos = item.span.lo + BytePos(open_pos as u32);
 835
 836             for item in trait_items {
 837                 visitor.visit_trait_item(item);
 838             }
 839
 840             visitor.format_missing(item.span.hi - BytePos(1));
 841
 842             let inner_indent_str = visitor.block_indent.to_string(context.config);
 843             let outer_indent_str = offset.block_only().to_string(context.config);
 844
 845             result.push('\n');
 846             result.push_str(&inner_indent_str);
 847             result.push_str(trim_newlines(visitor.buffer.to_string().trim()));
 848             result.push('\n');
 849             result.push_str(&outer_indent_str);
 850         } else if result.contains('\n') {
 851             result.push('\n');
 852         }
 853
 854         result.push('}');
 855         Some(result)
 856     } else {
 857         unreachable!();
 858     }
 859 }
 860
 861 fn format_unit_struct(item_name: &str, ident: ast::Ident, vis: &ast::Visibility) -> String {
 862     format!("{};", format_header(item_name, ident, vis))
 863 }
 864
 865 fn format_struct_struct(context: &RewriteContext,
 866                         item_name: &str,
 867                         ident: ast::Ident,
 868                         vis: &ast::Visibility,
 869                         fields: &[ast::StructField],
 870                         generics: Option<&ast::Generics>,
 871                         span: Span,
 872                         offset: Indent,
 873                         one_line_width: Option<usize>)
 874                         -> Option<String> {
 875     let mut result = String::with_capacity(1024);
 876
 877     let header_str = format_header(item_name, ident, vis);
 878     result.push_str(&header_str);
 879
 880     let body_lo = context.codemap.span_after(span, "{");
 881
 882     let generics_str = match generics {
 883         Some(g) => {
 884             try_opt!(format_generics(context,
 885                                      g,
 886                                      "{",
 887                                      "{",
 888                                      context.config.item_brace_style,
 889                                      fields.is_empty(),
 890                                      offset,
 891                                      offset + header_str.len(),
 892                                      mk_sp(span.lo, body_lo)))
 893         }
 894         None => {
 895             if context.config.item_brace_style == BraceStyle::AlwaysNextLine && !fields.is_empty() {
 896                 format!("\n{}{{", offset.block_only().to_string(context.config))
 897             } else {
 898                 " {".to_owned()
 899             }
 900         }
 901     };
 902     result.push_str(&generics_str);
 903
 904     // FIXME(#919): properly format empty structs and their comments.
 905     if fields.is_empty() {
 906         let snippet = context.snippet(mk_sp(body_lo, span.hi - BytePos(1)));
 907         if snippet.trim().is_empty() {
 908             // `struct S {}`
 909         } else if snippet.trim_right_matches(&[' ', '\t'][..]).ends_with('\n') {
 910             // fix indent
 911             result.push_str(&snippet.trim_right());
 912             result.push('\n');
 913             result.push_str(&offset.to_string(context.config));
 914         } else {
 915             result.push_str(&snippet);
 916         }
 917         result.push('}');
 918         return Some(result);
 919     }
 920
 921     let item_indent = offset.block_indent(context.config);
 922     // 1 = ","
 923     let item_budget = try_opt!(context.config.max_width.checked_sub(item_indent.width() + 1));
 924
 925     let items =
 926         itemize_list(context.codemap,
 927                      fields.iter(),
 928                      "}",
 929                      |field| {
 930             // Include attributes and doc comments, if present
 931             if !field.attrs.is_empty() {
 932                 field.attrs[0].span.lo
 933             } else {
 934                 field.span.lo
 935             }
 936         },
 937                      |field| field.ty.span.hi,
 938                      |field| field.rewrite(context, Shape::legacy(item_budget, item_indent)),
 939                      context.codemap.span_after(span, "{"),
 940                      span.hi)
 941                 .collect::<Vec<_>>();
 942     // 1 = ,
 943     let budget = context.config.max_width - offset.width() + context.config.tab_spaces - 1;
 944
 945     let tactic = match one_line_width {
 946         Some(w) => definitive_tactic(&items, ListTactic::LimitedHorizontalVertical(w), budget),
 947         None => DefinitiveListTactic::Vertical,
 948     };
 949
 950     let fmt = ListFormatting {
 951         tactic: tactic,
 952         separator: ",",
 953         trailing_separator: context.config.trailing_comma,
 954         shape: Shape::legacy(budget, item_indent),
 955         ends_with_newline: true,
 956         config: context.config,
 957     };
 958     let items_str = try_opt!(write_list(&items, &fmt));
 959     if one_line_width.is_some() && !items_str.contains('\n') {
 960         Some(format!("{} {} }}", result, items_str))
 961     } else {
 962         Some(format!("{}\n{}{}\n{}}}",
 963                      result,
 964                      offset.block_indent(context.config).to_string(context.config),
 965                      items_str,
 966                      offset.to_string(context.config)))
 967     }
 968 }
 969
 970 fn format_tuple_struct(context: &RewriteContext,
 971                        item_name: &str,
 972                        ident: ast::Ident,
 973                        vis: &ast::Visibility,
 974                        fields: &[ast::StructField],
 975                        generics: Option<&ast::Generics>,
 976                        span: Span,
 977                        offset: Indent)
 978                        -> Option<String> {
 979     let mut result = String::with_capacity(1024);
 980
 981     let header_str = format_header(item_name, ident, vis);
 982     result.push_str(&header_str);
 983
 984     // FIXME(#919): don't lose comments on empty tuple structs.
 985     let body_lo = if fields.is_empty() {
 986         span.hi
 987     } else {
 988         fields[0].span.lo
 989     };
 990
 991     let where_clause_str = match generics {
 992         Some(generics) => {
 993             let generics_str = try_opt!(rewrite_generics(context,
 994                                                          generics,
 995                                                          Shape::legacy(context.config.max_width,
 996                                                                        offset),
 997                                                          offset + header_str.len(),
 998                                                          mk_sp(span.lo, body_lo)));
 999             result.push_str(&generics_str);
1000
1001             let where_budget =
1002                 try_opt!(context.config.max_width.checked_sub(last_line_width(&result)));
1003             try_opt!(rewrite_where_clause(context,
1004                                           &generics.where_clause,
1005                                           context.config.item_brace_style,
1006                                           Shape::legacy(where_budget, offset.block_only()),
1007                                           Density::Compressed,
1008                                           ";",
1009                                           true,
1010                                           false,
1011                                           None))
1012         }
1013         None => "".to_owned(),
1014     };
1015     result.push('(');
1016
1017     let item_indent = offset.block_only() + result.len();
1018     // 2 = ");"
1019     let item_budget = try_opt!(context.config.max_width.checked_sub(item_indent.width() + 2));
1020
1021     let items =
1022         itemize_list(context.codemap,
1023                      fields.iter(),
1024                      ")",
1025                      |field| {
1026             // Include attributes and doc comments, if present
1027             if !field.attrs.is_empty() {
1028                 field.attrs[0].span.lo
1029             } else {
1030                 field.span.lo
1031             }
1032         },
1033                      |field| field.ty.span.hi,
1034                      |field| field.rewrite(context, Shape::legacy(item_budget, item_indent)),
1035                      context.codemap.span_after(span, "("),
1036                      span.hi);
1037     let body = try_opt!(format_item_list(items,
1038                                          Shape::legacy(item_budget, item_indent),
1039                                          context.config));
1040
1041     if context.config.spaces_within_parens && body.len() > 0 {
1042         result.push(' ');
1043     }
1044
1045     result.push_str(&body);
1046
1047     if context.config.spaces_within_parens && body.len() > 0 {
1048         result.push(' ');
1049     }
1050
1051     result.push(')');
1052
1053     if !where_clause_str.is_empty() && !where_clause_str.contains('\n') &&
1054        (result.contains('\n') ||
1055         offset.block_indent + result.len() + where_clause_str.len() + 1 >
1056         context.config.max_width) {
1057         // We need to put the where clause on a new line, but we didn'to_string
1058         // know that earlier, so the where clause will not be indented properly.
1059         result.push('\n');
1060         result.push_str(&(offset.block_only() + (context.config.tab_spaces - 1))
1061                              .to_string(context.config));
1062     }
1063     result.push_str(&where_clause_str);
1064
1065     Some(result)
1066 }
1067
1068 pub fn rewrite_type_alias(context: &RewriteContext,
1069                           indent: Indent,
1070                           ident: ast::Ident,
1071                           ty: &ast::Ty,
1072                           generics: &ast::Generics,
1073                           vis: &ast::Visibility,
1074                           span: Span)
1075                           -> Option<String> {
1076     let mut result = String::new();
1077
1078     result.push_str(&format_visibility(vis));
1079     result.push_str("type ");
1080     result.push_str(&ident.to_string());
1081
1082     let generics_indent = indent + result.len();
1083     let generics_span = mk_sp(context.codemap.span_after(span, "type"), ty.span.lo);
1084     let generics_width = context.config.max_width - " =".len();
1085     let generics_str = try_opt!(rewrite_generics(context,
1086                                                  generics,
1087                                                  Shape::legacy(generics_width, indent),
1088                                                  generics_indent,
1089                                                  generics_span));
1090
1091     result.push_str(&generics_str);
1092
1093     let where_budget = try_opt!(context.config.max_width.checked_sub(last_line_width(&result)));
1094     let where_clause_str = try_opt!(rewrite_where_clause(context,
1095                                                          &generics.where_clause,
1096                                                          context.config.item_brace_style,
1097                                                          Shape::legacy(where_budget, indent),
1098                                                          context.config.where_density,
1099                                                          "=",
1100                                                          true,
1101                                                          false,
1102                                                          Some(span.hi)));
1103     result.push_str(&where_clause_str);
1104     result.push_str(" = ");
1105
1106     let line_width = last_line_width(&result);
1107     // This checked_sub may fail as the extra space after '=' is not taken into account
1108     // In that case the budget is set to 0 which will make ty.rewrite retry on a new line
1109     let budget = context.config
1110         .max_width
1111         .checked_sub(indent.width() + line_width + ";".len())
1112         .unwrap_or(0);
1113     let type_indent = indent + line_width;
1114     // Try to fit the type on the same line
1115     let ty_str = try_opt!(ty.rewrite(context, Shape::legacy(budget, type_indent)).or_else(|| {
1116         // The line was too short, try to put the type on the next line
1117
1118         // Remove the space after '='
1119         result.pop();
1120         let type_indent = indent.block_indent(context.config);
1121         result.push('\n');
1122         result.push_str(&type_indent.to_string(context.config));
1123         let budget = try_opt!(context.config.max_width.checked_sub(type_indent.width() +
1124                                                                    ";".len()));
1125         ty.rewrite(context, Shape::legacy(budget, type_indent))
1126     }));
1127     result.push_str(&ty_str);
1128     result.push_str(";");
1129     Some(result)
1130 }
1131
1132 fn type_annotation_spacing(config: &Config) -> (&str, &str) {
1133     (if config.space_before_type_annotation {
1134          " "
1135      } else {
1136          ""
1137      },
1138      if config.space_after_type_annotation_colon {
1139          " "
1140      } else {
1141          ""
1142      })
1143 }
1144
1145 impl Rewrite for ast::StructField {
1146     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
1147         if contains_skip(&self.attrs) {
1148             let span = context.snippet(mk_sp(self.attrs[0].span.lo, self.span.hi));
1149             return wrap_str(span, context.config.max_width, shape);
1150         }
1151
1152         let name = self.ident;
1153         let vis = format_visibility(&self.vis);
1154         let mut attr_str = try_opt!(self.attrs.rewrite(context,
1155                                                        Shape::legacy(context.config.max_width -
1156                                                                      shape.indent.width(),
1157                                                                      shape.indent)));
1158         if !attr_str.is_empty() {
1159             attr_str.push('\n');
1160             attr_str.push_str(&shape.indent.to_string(context.config));
1161         }
1162
1163         let type_annotation_spacing = type_annotation_spacing(context.config);
1164         let result = match name {
1165             Some(name) => {
1166                 format!("{}{}{}{}:{}",
1167                         attr_str,
1168                         vis,
1169                         name,
1170                         type_annotation_spacing.0,
1171                         type_annotation_spacing.1)
1172             }
1173             None => format!("{}{}", attr_str, vis),
1174         };
1175
1176         let last_line_width = last_line_width(&result);
1177         let budget = try_opt!(shape.width.checked_sub(last_line_width));
1178         let rewrite = try_opt!(self.ty.rewrite(context,
1179                                                Shape::legacy(budget,
1180                                                              shape.indent + last_line_width)));
1181         Some(result + &rewrite)
1182     }
1183 }
1184
1185 pub fn rewrite_static(prefix: &str,
1186                       vis: &ast::Visibility,
1187                       ident: ast::Ident,
1188                       ty: &ast::Ty,
1189                       mutability: ast::Mutability,
1190                       expr_opt: Option<&ptr::P<ast::Expr>>,
1191                       offset: Indent,
1192                       context: &RewriteContext)
1193                       -> Option<String> {
1194     let type_annotation_spacing = type_annotation_spacing(context.config);
1195     let prefix = format!("{}{} {}{}{}:{}",
1196                          format_visibility(vis),
1197                          prefix,
1198                          format_mutability(mutability),
1199                          ident,
1200                          type_annotation_spacing.0,
1201                          type_annotation_spacing.1);
1202     // 2 = " =".len()
1203     let ty_str = try_opt!(ty.rewrite(context,
1204                                      Shape::legacy(context.config.max_width - offset.block_indent -
1205                                                    prefix.len() -
1206                                                    2,
1207                                                    offset.block_only())));
1208
1209     if let Some(expr) = expr_opt {
1210         let lhs = format!("{}{} =", prefix, ty_str);
1211         // 1 = ;
1212         let remaining_width = context.config.max_width - offset.block_indent - 1;
1213         rewrite_assign_rhs(context,
1214                            lhs,
1215                            expr,
1216                            Shape::legacy(remaining_width, offset.block_only()))
1217                 .map(|s| s + ";")
1218     } else {
1219         let lhs = format!("{}{};", prefix, ty_str);
1220         Some(lhs)
1221     }
1222 }
1223
1224 pub fn rewrite_associated_type(ident: ast::Ident,
1225                                ty_opt: Option<&ptr::P<ast::Ty>>,
1226                                ty_param_bounds_opt: Option<&ast::TyParamBounds>,
1227                                context: &RewriteContext,
1228                                indent: Indent)
1229                                -> Option<String> {
1230     let prefix = format!("type {}", ident);
1231
1232     let type_bounds_str = if let Some(ty_param_bounds) = ty_param_bounds_opt {
1233         let bounds: &[_] = ty_param_bounds;
1234         let bound_str = try_opt!(bounds.iter()
1235             .map(|ty_bound| {
1236                 ty_bound.rewrite(context, Shape::legacy(context.config.max_width, indent))
1237             })
1238             .intersperse(Some(" + ".to_string()))
1239             .collect::<Option<String>>());
1240         if bounds.len() > 0 {
1241             format!(": {}", bound_str)
1242         } else {
1243             String::new()
1244         }
1245     } else {
1246         String::new()
1247     };
1248
1249     if let Some(ty) = ty_opt {
1250         let ty_str = try_opt!(ty.rewrite(context,
1251                                          Shape::legacy(context.config.max_width -
1252                                                        indent.block_indent -
1253                                                        prefix.len() -
1254                                                        2,
1255                                                        indent.block_only())));
1256         Some(format!("{} = {};", prefix, ty_str))
1257     } else {
1258         Some(format!("{}{};", prefix, type_bounds_str))
1259     }
1260 }
1261
1262 pub fn rewrite_associated_impl_type(ident: ast::Ident,
1263                                     defaultness: ast::Defaultness,
1264                                     ty_opt: Option<&ptr::P<ast::Ty>>,
1265                                     ty_param_bounds_opt: Option<&ast::TyParamBounds>,
1266                                     context: &RewriteContext,
1267                                     indent: Indent)
1268                                     -> Option<String> {
1269     let result =
1270         try_opt!(rewrite_associated_type(ident, ty_opt, ty_param_bounds_opt, context, indent));
1271
1272     match defaultness {
1273         ast::Defaultness::Default => Some(format!("default {}", result)),
1274         _ => Some(result),
1275     }
1276 }
1277
1278 impl Rewrite for ast::FunctionRetTy {
1279     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
1280         match *self {
1281             ast::FunctionRetTy::Default(_) => Some(String::new()),
1282             ast::FunctionRetTy::Ty(ref ty) => {
1283                 let inner_width = try_opt!(shape.width.checked_sub(3));
1284                 ty.rewrite(context, Shape::legacy(inner_width, shape.indent + 3)).map(|r| {
1285                     format!("-> {}", r)
1286                 })
1287             }
1288         }
1289     }
1290 }
1291
1292 impl Rewrite for ast::Arg {
1293     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
1294         if is_named_arg(self) {
1295             let mut result = try_opt!(self.pat.rewrite(context,
1296                                                        Shape::legacy(shape.width, shape.indent)));
1297
1298             if self.ty.node != ast::TyKind::Infer {
1299                 if context.config.space_before_type_annotation {
1300                     result.push_str(" ");
1301                 }
1302                 result.push_str(":");
1303                 if context.config.space_after_type_annotation_colon {
1304                     result.push_str(" ");
1305                 }
1306                 let max_width = try_opt!(shape.width.checked_sub(result.len()));
1307                 let ty_str = try_opt!(self.ty.rewrite(context,
1308                                                       Shape::legacy(max_width,
1309                                                                     shape.indent + result.len())));
1310                 result.push_str(&ty_str);
1311             }
1312
1313             Some(result)
1314         } else {
1315             self.ty.rewrite(context, shape)
1316         }
1317     }
1318 }
1319
1320 fn rewrite_explicit_self(explicit_self: &ast::ExplicitSelf,
1321                          args: &[ast::Arg],
1322                          context: &RewriteContext)
1323                          -> Option<String> {
1324     match explicit_self.node {
1325         ast::SelfKind::Region(lt, m) => {
1326             let mut_str = format_mutability(m);
1327             match lt {
1328                 Some(ref l) => {
1329                     let lifetime_str = try_opt!(l.rewrite(context,
1330                                                           Shape::legacy(usize::max_value(),
1331                                                                         Indent::empty())));
1332                     Some(format!("&{} {}self", lifetime_str, mut_str))
1333                 }
1334                 None => Some(format!("&{}self", mut_str)),
1335             }
1336         }
1337         ast::SelfKind::Explicit(ref ty, _) => {
1338             assert!(!args.is_empty(), "&[ast::Arg] shouldn't be empty.");
1339
1340             let mutability = explicit_self_mutability(&args[0]);
1341             let type_str = try_opt!(ty.rewrite(context,
1342                                                Shape::legacy(usize::max_value(), Indent::empty())));
1343
1344             Some(format!("{}self: {}", format_mutability(mutability), type_str))
1345         }
1346         ast::SelfKind::Value(_) => {
1347             assert!(!args.is_empty(), "&[ast::Arg] shouldn't be empty.");
1348
1349             let mutability = explicit_self_mutability(&args[0]);
1350
1351             Some(format!("{}self", format_mutability(mutability)))
1352         }
1353     }
1354 }
1355
1356 // Hacky solution caused by absence of `Mutability` in `SelfValue` and
1357 // `SelfExplicit` variants of `ast::ExplicitSelf_`.
1358 fn explicit_self_mutability(arg: &ast::Arg) -> ast::Mutability {
1359     if let ast::PatKind::Ident(ast::BindingMode::ByValue(mutability), _, _) = arg.pat.node {
1360         mutability
1361     } else {
1362         unreachable!()
1363     }
1364 }
1365
1366 pub fn span_lo_for_arg(arg: &ast::Arg) -> BytePos {
1367     if is_named_arg(arg) {
1368         arg.pat.span.lo
1369     } else {
1370         arg.ty.span.lo
1371     }
1372 }
1373
1374 pub fn span_hi_for_arg(arg: &ast::Arg) -> BytePos {
1375     match arg.ty.node {
1376         ast::TyKind::Infer if is_named_arg(arg) => arg.pat.span.hi,
1377         _ => arg.ty.span.hi,
1378     }
1379 }
1380
1381 pub fn is_named_arg(arg: &ast::Arg) -> bool {
1382     if let ast::PatKind::Ident(_, ident, _) = arg.pat.node {
1383         ident.node != symbol::keywords::Invalid.ident()
1384     } else {
1385         true
1386     }
1387 }
1388
1389 fn span_for_return(ret: &ast::FunctionRetTy) -> Span {
1390     match *ret {
1391         ast::FunctionRetTy::Default(ref span) => span.clone(),
1392         ast::FunctionRetTy::Ty(ref ty) => ty.span,
1393     }
1394 }
1395
1396 fn span_for_ty_param(ty: &ast::TyParam) -> Span {
1397     // Note that ty.span is the span for ty.ident, not the whole item.
1398     let lo = ty.span.lo;
1399     if let Some(ref def) = ty.default {
1400         return mk_sp(lo, def.span.hi);
1401     }
1402     if ty.bounds.is_empty() {
1403         return ty.span;
1404     }
1405     let hi = match ty.bounds[ty.bounds.len() - 1] {
1406         ast::TyParamBound::TraitTyParamBound(ref ptr, _) => ptr.span.hi,
1407         ast::TyParamBound::RegionTyParamBound(ref l) => l.span.hi,
1408     };
1409     mk_sp(lo, hi)
1410 }
1411
1412 fn span_for_where_pred(pred: &ast::WherePredicate) -> Span {
1413     match *pred {
1414         ast::WherePredicate::BoundPredicate(ref p) => p.span,
1415         ast::WherePredicate::RegionPredicate(ref p) => p.span,
1416         ast::WherePredicate::EqPredicate(ref p) => p.span,
1417     }
1418 }
1419
1420 // Return type is (result, force_new_line_for_brace)
1421 fn rewrite_fn_base(context: &RewriteContext,
1422                    indent: Indent,
1423                    ident: ast::Ident,
1424                    fd: &ast::FnDecl,
1425                    generics: &ast::Generics,
1426                    unsafety: ast::Unsafety,
1427                    constness: ast::Constness,
1428                    defaultness: ast::Defaultness,
1429                    abi: abi::Abi,
1430                    vis: &ast::Visibility,
1431                    span: Span,
1432                    newline_brace: bool,
1433                    has_body: bool)
1434                    -> Option<(String, bool)> {
1435     let mut force_new_line_for_brace = false;
1436
1437     let where_clause = &generics.where_clause;
1438
1439     let mut result = String::with_capacity(1024);
1440     // Vis unsafety abi.
1441     result.push_str(&*format_visibility(vis));
1442
1443     if let ast::Defaultness::Default = defaultness {
1444         result.push_str("default ");
1445     }
1446
1447     if let ast::Constness::Const = constness {
1448         result.push_str("const ");
1449     }
1450
1451     result.push_str(::utils::format_unsafety(unsafety));
1452
1453     if abi != abi::Abi::Rust {
1454         result.push_str(&::utils::format_abi(abi, context.config.force_explicit_abi));
1455     }
1456
1457     // fn foo
1458     result.push_str("fn ");
1459     result.push_str(&ident.to_string());
1460
1461     // Generics.
1462     let generics_indent = indent + result.len();
1463     let generics_span = mk_sp(span.lo, span_for_return(&fd.output).lo);
1464     let generics_str = try_opt!(rewrite_generics(context,
1465                                                  generics,
1466                                                  Shape::legacy(context.config.max_width, indent),
1467                                                  generics_indent,
1468                                                  generics_span));
1469     result.push_str(&generics_str);
1470
1471     // Note that if the width and indent really matter, we'll re-layout the
1472     // return type later anyway.
1473     let ret_str = try_opt!(fd.output.rewrite(&context,
1474                                              Shape::legacy(context.config.max_width -
1475                                                            indent.width(),
1476                                                            indent)));
1477
1478     let multi_line_ret_str = ret_str.contains('\n');
1479     let ret_str_len = if multi_line_ret_str { 0 } else { ret_str.len() };
1480
1481     // Args.
1482     let (mut one_line_budget, mut multi_line_budget, mut arg_indent) =
1483         try_opt!(compute_budgets_for_args(context, &result, indent, ret_str_len, newline_brace));
1484
1485     if context.config.fn_args_layout == FnArgLayoutStyle::Block ||
1486        context.config.fn_args_layout == FnArgLayoutStyle::BlockAlways {
1487         arg_indent = indent.block_indent(context.config);
1488         multi_line_budget = context.config.max_width - arg_indent.width();
1489     }
1490
1491     debug!("rewrite_fn_base: one_line_budget: {}, multi_line_budget: {}, arg_indent: {:?}",
1492            one_line_budget,
1493            multi_line_budget,
1494            arg_indent);
1495
1496     // Check if vertical layout was forced.
1497     if one_line_budget == 0 {
1498         if context.config.fn_args_paren_newline {
1499             result.push('\n');
1500             result.push_str(&arg_indent.to_string(context.config));
1501             arg_indent = arg_indent + 1; // extra space for `(`
1502             result.push('(');
1503             if context.config.spaces_within_parens && fd.inputs.len() > 0 {
1504                 result.push(' ')
1505             }
1506         } else {
1507             result.push_str("(\n");
1508             result.push_str(&arg_indent.to_string(context.config));
1509         }
1510     } else {
1511         result.push('(');
1512         if context.config.spaces_within_parens && fd.inputs.len() > 0 {
1513             result.push(' ')
1514         }
1515     }
1516
1517     if multi_line_ret_str {
1518         one_line_budget = 0;
1519     }
1520
1521     // A conservative estimation, to goal is to be over all parens in generics
1522     let args_start = generics.ty_params.last().map_or(span.lo, |tp| end_typaram(tp));
1523     let args_span = mk_sp(context.codemap.span_after(mk_sp(args_start, span.hi), "("),
1524                           span_for_return(&fd.output).lo);
1525     let arg_str = try_opt!(rewrite_args(context,
1526                                         &fd.inputs,
1527                                         fd.get_self().as_ref(),
1528                                         one_line_budget,
1529                                         multi_line_budget,
1530                                         indent,
1531                                         arg_indent,
1532                                         args_span,
1533                                         fd.variadic));
1534
1535     let multi_line_arg_str = arg_str.contains('\n');
1536
1537     let put_args_in_block = match context.config.fn_args_layout {
1538         FnArgLayoutStyle::Block => multi_line_arg_str,
1539         FnArgLayoutStyle::BlockAlways => true,
1540         _ => false,
1541     } && !fd.inputs.is_empty();
1542
1543     if put_args_in_block {
1544         arg_indent = indent.block_indent(context.config);
1545         result.push('\n');
1546         result.push_str(&arg_indent.to_string(context.config));
1547         result.push_str(&arg_str);
1548         result.push('\n');
1549         result.push_str(&indent.to_string(context.config));
1550         result.push(')');
1551     } else {
1552         result.push_str(&arg_str);
1553         if context.config.spaces_within_parens && fd.inputs.len() > 0 {
1554             result.push(' ')
1555         }
1556         result.push(')');
1557     }
1558
1559     // Return type.
1560     if !ret_str.is_empty() {
1561         let ret_should_indent = match context.config.fn_args_layout {
1562             // If our args are block layout then we surely must have space.
1563             FnArgLayoutStyle::Block if put_args_in_block => false,
1564             FnArgLayoutStyle::BlockAlways => false,
1565             _ => {
1566                 // If we've already gone multi-line, or the return type would push over the max
1567                 // width, then put the return type on a new line. With the +1 for the signature
1568                 // length an additional space between the closing parenthesis of the argument and
1569                 // the arrow '->' is considered.
1570                 let mut sig_length = result.len() + indent.width() + ret_str_len + 1;
1571
1572                 // If there is no where clause, take into account the space after the return type
1573                 // and the brace.
1574                 if where_clause.predicates.is_empty() {
1575                     sig_length += 2;
1576                 }
1577
1578                 let overlong_sig = sig_length > context.config.max_width;
1579
1580                 result.contains('\n') || multi_line_ret_str || overlong_sig
1581             }
1582         };
1583         let ret_indent = if ret_should_indent {
1584             let indent = match context.config.fn_return_indent {
1585                 ReturnIndent::WithWhereClause => indent + 4,
1586                 // Aligning with non-existent args looks silly.
1587                 _ if arg_str.is_empty() => {
1588                     force_new_line_for_brace = true;
1589                     indent + 4
1590                 }
1591                 // FIXME: we might want to check that using the arg indent
1592                 // doesn't blow our budget, and if it does, then fallback to
1593                 // the where clause indent.
1594                 _ => arg_indent,
1595             };
1596
1597             result.push('\n');
1598             result.push_str(&indent.to_string(context.config));
1599             indent
1600         } else {
1601             result.push(' ');
1602             Indent::new(indent.width(), result.len())
1603         };
1604
1605         if multi_line_ret_str {
1606             // Now that we know the proper indent and width, we need to
1607             // re-layout the return type.
1608             let budget = try_opt!(context.config.max_width.checked_sub(ret_indent.width()));
1609             let ret_str = try_opt!(fd.output.rewrite(context, Shape::legacy(budget, ret_indent)));
1610             result.push_str(&ret_str);
1611         } else {
1612             result.push_str(&ret_str);
1613         }
1614
1615         // Comment between return type and the end of the decl.
1616         let snippet_lo = fd.output.span().hi;
1617         if where_clause.predicates.is_empty() {
1618             let snippet_hi = span.hi;
1619             let snippet = context.snippet(mk_sp(snippet_lo, snippet_hi));
1620             let snippet = snippet.trim();
1621             if !snippet.is_empty() {
1622                 result.push(' ');
1623                 result.push_str(snippet);
1624             }
1625         } else {
1626             // FIXME it would be nice to catch comments between the return type
1627             // and the where clause, but we don't have a span for the where
1628             // clause.
1629         }
1630     }
1631
1632     let should_compress_where = match context.config.where_density {
1633         Density::Compressed => !result.contains('\n') || put_args_in_block,
1634         Density::CompressedIfEmpty => !has_body && !result.contains('\n'),
1635         _ => false,
1636     } || (put_args_in_block && ret_str.is_empty());
1637
1638     let where_density = if should_compress_where {
1639         Density::Compressed
1640     } else {
1641         Density::Tall
1642     };
1643
1644     // Where clause.
1645     let where_budget = try_opt!(context.config.max_width.checked_sub(last_line_width(&result)));
1646     let where_clause_str = try_opt!(rewrite_where_clause(context,
1647                                                          where_clause,
1648                                                          context.config.fn_brace_style,
1649                                                          Shape::legacy(where_budget, indent),
1650                                                          where_density,
1651                                                          "{",
1652                                                          !has_body,
1653                                                          put_args_in_block && ret_str.is_empty(),
1654                                                          Some(span.hi)));
1655
1656     if last_line_width(&result) + where_clause_str.len() > context.config.max_width &&
1657        !where_clause_str.contains('\n') {
1658         result.push('\n');
1659     }
1660
1661     result.push_str(&where_clause_str);
1662
1663     Some((result, force_new_line_for_brace))
1664 }
1665
1666 fn rewrite_args(context: &RewriteContext,
1667                 args: &[ast::Arg],
1668                 explicit_self: Option<&ast::ExplicitSelf>,
1669                 one_line_budget: usize,
1670                 multi_line_budget: usize,
1671                 indent: Indent,
1672                 arg_indent: Indent,
1673                 span: Span,
1674                 variadic: bool)
1675                 -> Option<String> {
1676     let mut arg_item_strs =
1677         try_opt!(args.iter()
1678                      .map(|arg| {
1679                               arg.rewrite(&context, Shape::legacy(multi_line_budget, arg_indent))
1680                           })
1681                      .collect::<Option<Vec<_>>>());
1682
1683     // Account for sugary self.
1684     // FIXME: the comment for the self argument is dropped. This is blocked
1685     // on rust issue #27522.
1686     let min_args =
1687         explicit_self.and_then(|explicit_self| rewrite_explicit_self(explicit_self, args, context))
1688             .map_or(1, |self_str| {
1689                 arg_item_strs[0] = self_str;
1690                 2
1691             });
1692
1693     // Comments between args.
1694     let mut arg_items = Vec::new();
1695     if min_args == 2 {
1696         arg_items.push(ListItem::from_str(""));
1697     }
1698
1699     // FIXME(#21): if there are no args, there might still be a comment, but
1700     // without spans for the comment or parens, there is no chance of
1701     // getting it right. You also don't get to put a comment on self, unless
1702     // it is explicit.
1703     if args.len() >= min_args || variadic {
1704         let comment_span_start = if min_args == 2 {
1705             let second_arg_start = if arg_has_pattern(&args[1]) {
1706                 args[1].pat.span.lo
1707             } else {
1708                 args[1].ty.span.lo
1709             };
1710             let reduced_span = mk_sp(span.lo, second_arg_start);
1711
1712             context.codemap.span_after_last(reduced_span, ",")
1713         } else {
1714             span.lo
1715         };
1716
1717         enum ArgumentKind<'a> {
1718             Regular(&'a ast::Arg),
1719             Variadic(BytePos),
1720         }
1721
1722         let variadic_arg = if variadic {
1723             let variadic_span = mk_sp(args.last()
1724                                           .unwrap()
1725                                           .ty
1726                                           .span
1727                                           .hi,
1728                                       span.hi);
1729             let variadic_start = context.codemap.span_after(variadic_span, "...") - BytePos(3);
1730             Some(ArgumentKind::Variadic(variadic_start))
1731         } else {
1732             None
1733         };
1734
1735         let more_items = itemize_list(context.codemap,
1736                                       args[min_args - 1..]
1737                                           .iter()
1738                                           .map(ArgumentKind::Regular)
1739                                           .chain(variadic_arg),
1740                                       ")",
1741                                       |arg| match *arg {
1742                                           ArgumentKind::Regular(arg) => span_lo_for_arg(arg),
1743                                           ArgumentKind::Variadic(start) => start,
1744                                       },
1745                                       |arg| match *arg {
1746                                           ArgumentKind::Regular(arg) => arg.ty.span.hi,
1747                                           ArgumentKind::Variadic(start) => start + BytePos(3),
1748                                       },
1749                                       |arg| match *arg {
1750                                           ArgumentKind::Regular(..) => None,
1751                                           ArgumentKind::Variadic(..) => Some("...".to_owned()),
1752                                       },
1753                                       comment_span_start,
1754                                       span.hi);
1755
1756         arg_items.extend(more_items);
1757     }
1758
1759     for (item, arg) in arg_items.iter_mut().zip(arg_item_strs) {
1760         item.item = Some(arg);
1761     }
1762
1763     let indent = match context.config.fn_arg_indent {
1764         BlockIndentStyle::Inherit => indent,
1765         BlockIndentStyle::Tabbed => indent.block_indent(context.config),
1766         BlockIndentStyle::Visual => arg_indent,
1767     };
1768
1769     let tactic = definitive_tactic(&arg_items,
1770                                    context.config.fn_args_density.to_list_tactic(),
1771                                    one_line_budget);
1772     let budget = match tactic {
1773         DefinitiveListTactic::Horizontal => one_line_budget,
1774         _ => multi_line_budget,
1775     };
1776
1777     debug!("rewrite_args: budget: {}, tactic: {:?}", budget, tactic);
1778
1779     let (trailing_comma, end_with_newline) = match context.config.fn_args_layout {
1780         FnArgLayoutStyle::Block => (SeparatorTactic::Vertical, true),
1781         FnArgLayoutStyle::BlockAlways => (SeparatorTactic::Always, true),
1782         _ => (SeparatorTactic::Never, false),
1783     };
1784
1785     let fmt = ListFormatting {
1786         tactic: tactic,
1787         separator: ",",
1788         trailing_separator: trailing_comma,
1789         shape: Shape::legacy(budget, indent),
1790         ends_with_newline: end_with_newline,
1791         config: context.config,
1792     };
1793
1794     write_list(&arg_items, &fmt)
1795 }
1796
1797 fn arg_has_pattern(arg: &ast::Arg) -> bool {
1798     if let ast::PatKind::Ident(_, ident, _) = arg.pat.node {
1799         ident.node != symbol::keywords::Invalid.ident()
1800     } else {
1801         true
1802     }
1803 }
1804
1805 fn compute_budgets_for_args(context: &RewriteContext,
1806                             result: &str,
1807                             indent: Indent,
1808                             ret_str_len: usize,
1809                             newline_brace: bool)
1810                             -> Option<((usize, usize, Indent))> {
1811     debug!("compute_budgets_for_args {} {:?}, {}, {}",
1812            result.len(),
1813            indent,
1814            ret_str_len,
1815            newline_brace);
1816     // Try keeping everything on the same line.
1817     if !result.contains('\n') {
1818         // 3 = `() `, space is before ret_string.
1819         let mut used_space = indent.width() + result.len() + ret_str_len + 3;
1820         if !newline_brace {
1821             used_space += 2;
1822         }
1823         let one_line_budget = context.config
1824             .max_width
1825             .checked_sub(used_space)
1826             .unwrap_or(0);
1827
1828         if one_line_budget > 0 {
1829             // 4 = "() {".len()
1830             let multi_line_budget =
1831                 try_opt!(context.config.max_width.checked_sub(indent.width() + result.len() + 4));
1832
1833             return Some((one_line_budget, multi_line_budget, indent + result.len() + 1));
1834         }
1835     }
1836
1837     // Didn't work. we must force vertical layout and put args on a newline.
1838     let new_indent = indent.block_indent(context.config);
1839     let used_space = new_indent.width() + 4; // Account for `(` and `)` and possibly ` {`.
1840     let max_space = context.config.max_width;
1841     if used_space <= max_space {
1842         Some((0, max_space - used_space, new_indent))
1843     } else {
1844         // Whoops! bankrupt.
1845         None
1846     }
1847 }
1848
1849 fn newline_for_brace(config: &Config, where_clause: &ast::WhereClause) -> bool {
1850     match config.fn_brace_style {
1851         BraceStyle::AlwaysNextLine => true,
1852         BraceStyle::SameLineWhere if !where_clause.predicates.is_empty() => true,
1853         _ => false,
1854     }
1855 }
1856
1857 fn rewrite_generics(context: &RewriteContext,
1858                     generics: &ast::Generics,
1859                     shape: Shape,
1860                     // TODO shouldn't need this
1861                     generics_offset: Indent,
1862                     span: Span)
1863                     -> Option<String> {
1864     // FIXME: convert bounds to where clauses where they get too big or if
1865     // there is a where clause at all.
1866     let lifetimes: &[_] = &generics.lifetimes;
1867     let tys: &[_] = &generics.ty_params;
1868     if lifetimes.is_empty() && tys.is_empty() {
1869         return Some(String::new());
1870     }
1871
1872     let offset = match context.config.generics_indent {
1873         BlockIndentStyle::Inherit => shape.indent,
1874         BlockIndentStyle::Tabbed => shape.indent.block_indent(context.config),
1875         // 1 = <
1876         BlockIndentStyle::Visual => generics_offset + 1,
1877     };
1878
1879     let h_budget = try_opt!(shape.width.checked_sub(generics_offset.width() + 2));
1880     // FIXME: might need to insert a newline if the generics are really long.
1881
1882     // Strings for the generics.
1883     let lt_strs = lifetimes.iter().map(|lt| lt.rewrite(context, Shape::legacy(h_budget, offset)));
1884     let ty_strs =
1885         tys.iter().map(|ty_param| ty_param.rewrite(context, Shape::legacy(h_budget, offset)));
1886
1887     // Extract comments between generics.
1888     let lt_spans = lifetimes.iter().map(|l| {
1889         let hi = if l.bounds.is_empty() {
1890             l.lifetime.span.hi
1891         } else {
1892             l.bounds[l.bounds.len() - 1].span.hi
1893         };
1894         mk_sp(l.lifetime.span.lo, hi)
1895     });
1896     let ty_spans = tys.iter().map(span_for_ty_param);
1897
1898     let items = itemize_list(context.codemap,
1899                              lt_spans.chain(ty_spans).zip(lt_strs.chain(ty_strs)),
1900                              ">",
1901                              |&(sp, _)| sp.lo,
1902                              |&(sp, _)| sp.hi,
1903                              // FIXME: don't clone
1904                              |&(_, ref str)| str.clone(),
1905                              context.codemap.span_after(span, "<"),
1906                              span.hi);
1907     let list_str =
1908         try_opt!(format_item_list(items, Shape::legacy(h_budget, offset), context.config));
1909
1910     Some(if context.config.spaces_within_angle_brackets {
1911              format!("< {} >", list_str)
1912          } else {
1913              format!("<{}>", list_str)
1914          })
1915 }
1916
1917 fn rewrite_trait_bounds(context: &RewriteContext,
1918                         type_param_bounds: &ast::TyParamBounds,
1919                         shape: Shape)
1920                         -> Option<String> {
1921     let bounds: &[_] = type_param_bounds;
1922
1923     if bounds.is_empty() {
1924         return Some(String::new());
1925     }
1926
1927     let bound_str = try_opt!(bounds.iter()
1928                                  .map(|ty_bound| ty_bound.rewrite(&context, shape))
1929                                  .intersperse(Some(" + ".to_string()))
1930                                  .collect::<Option<String>>());
1931
1932     let mut result = String::new();
1933     result.push_str(": ");
1934     result.push_str(&bound_str);
1935     Some(result)
1936 }
1937
1938 //   fn reflow_list_node_with_rule(
1939 //        &self,
1940 //        node: &CompoundNode,
1941 //        rule: &Rule,
1942 //        args: &[Arg],
1943 //        shape: &Shape
1944 //    ) -> Result<String, ()>
1945 //    where
1946 //        T: Foo,
1947 //    {
1948
1949
1950 fn rewrite_where_clause_rfc_style(context: &RewriteContext,
1951                                   where_clause: &ast::WhereClause,
1952                                   shape: Shape,
1953                                   terminator: &str,
1954                                   suppress_comma: bool,
1955                                   // where clause can be kept on the current line.
1956                                   snuggle: bool,
1957                                   span_end: Option<BytePos>)
1958                                   -> Option<String> {
1959     let block_shape = shape.block();
1960
1961     let starting_newline = if snuggle {
1962         " ".to_owned()
1963     } else {
1964         "\n".to_owned() + &block_shape.indent.to_string(context.config)
1965     };
1966
1967     let clause_shape = block_shape.block_indent(context.config.tab_spaces);
1968     // each clause on one line, trailing comma (except if suppress_comma)
1969     let span_start = span_for_where_pred(&where_clause.predicates[0]).lo;
1970     // If we don't have the start of the next span, then use the end of the
1971     // predicates, but that means we miss comments.
1972     let len = where_clause.predicates.len();
1973     let end_of_preds = span_for_where_pred(&where_clause.predicates[len - 1]).hi;
1974     let span_end = span_end.unwrap_or(end_of_preds);
1975     let items = itemize_list(context.codemap,
1976                              where_clause.predicates.iter(),
1977                              terminator,
1978                              |pred| span_for_where_pred(pred).lo,
1979                              |pred| span_for_where_pred(pred).hi,
1980                              |pred| pred.rewrite(context, clause_shape),
1981                              span_start,
1982                              span_end);
1983     let comma_tactic = if suppress_comma {
1984         SeparatorTactic::Never
1985     } else {
1986         SeparatorTactic::Always
1987     };
1988
1989     let fmt = ListFormatting {
1990         tactic: DefinitiveListTactic::Vertical,
1991         separator: ",",
1992         trailing_separator: comma_tactic,
1993         shape: clause_shape,
1994         ends_with_newline: true,
1995         config: context.config,
1996     };
1997     let preds_str = try_opt!(write_list(items, &fmt));
1998
1999     Some(format!("{}where\n{}{}",
2000                  starting_newline,
2001                  clause_shape.indent.to_string(context.config),
2002                  preds_str))
2003 }
2004
2005 fn rewrite_where_clause(context: &RewriteContext,
2006                         where_clause: &ast::WhereClause,
2007                         brace_style: BraceStyle,
2008                         shape: Shape,
2009                         density: Density,
2010                         terminator: &str,
2011                         suppress_comma: bool,
2012                         snuggle: bool,
2013                         span_end: Option<BytePos>)
2014                         -> Option<String> {
2015     if where_clause.predicates.is_empty() {
2016         return Some(String::new());
2017     }
2018
2019     if context.config.where_style == Style::Rfc {
2020         return rewrite_where_clause_rfc_style(context,
2021                                               where_clause,
2022                                               shape,
2023                                               terminator,
2024                                               suppress_comma,
2025                                               snuggle,
2026                                               span_end);
2027     }
2028
2029     let extra_indent = match context.config.where_indent {
2030         BlockIndentStyle::Inherit => Indent::empty(),
2031         BlockIndentStyle::Tabbed | BlockIndentStyle::Visual => {
2032             Indent::new(context.config.tab_spaces, 0)
2033         }
2034     };
2035
2036     let offset = match context.config.where_pred_indent {
2037         BlockIndentStyle::Inherit => shape.indent + extra_indent,
2038         BlockIndentStyle::Tabbed => shape.indent + extra_indent.block_indent(context.config),
2039         // 6 = "where ".len()
2040         BlockIndentStyle::Visual => shape.indent + extra_indent + 6,
2041     };
2042     // FIXME: if where_pred_indent != Visual, then the budgets below might
2043     // be out by a char or two.
2044
2045     let budget = context.config.max_width - offset.width();
2046     let span_start = span_for_where_pred(&where_clause.predicates[0]).lo;
2047     // If we don't have the start of the next span, then use the end of the
2048     // predicates, but that means we miss comments.
2049     let len = where_clause.predicates.len();
2050     let end_of_preds = span_for_where_pred(&where_clause.predicates[len - 1]).hi;
2051     let span_end = span_end.unwrap_or(end_of_preds);
2052     let items = itemize_list(context.codemap,
2053                              where_clause.predicates.iter(),
2054                              terminator,
2055                              |pred| span_for_where_pred(pred).lo,
2056                              |pred| span_for_where_pred(pred).hi,
2057                              |pred| pred.rewrite(context, Shape::legacy(budget, offset)),
2058                              span_start,
2059                              span_end);
2060     let item_vec = items.collect::<Vec<_>>();
2061     // FIXME: we don't need to collect here if the where_layout isn't
2062     // HorizontalVertical.
2063     let tactic = definitive_tactic(&item_vec, context.config.where_layout, budget);
2064
2065     let mut comma_tactic = context.config.trailing_comma;
2066     // Kind of a hack because we don't usually have trailing commas in where clauses.
2067     if comma_tactic == SeparatorTactic::Vertical || suppress_comma {
2068         comma_tactic = SeparatorTactic::Never;
2069     }
2070
2071     let fmt = ListFormatting {
2072         tactic: tactic,
2073         separator: ",",
2074         trailing_separator: comma_tactic,
2075         shape: Shape::legacy(budget, offset),
2076         ends_with_newline: true,
2077         config: context.config,
2078     };
2079     let preds_str = try_opt!(write_list(&item_vec, &fmt));
2080
2081     let end_length = if terminator == "{" {
2082         // If the brace is on the next line we don't need to count it otherwise it needs two
2083         // characters " {"
2084         match brace_style {
2085             BraceStyle::AlwaysNextLine |
2086             BraceStyle::SameLineWhere => 0,
2087             BraceStyle::PreferSameLine => 2,
2088         }
2089     } else if terminator == "=" {
2090         2
2091     } else {
2092         terminator.len()
2093     };
2094     if density == Density::Tall || preds_str.contains('\n') ||
2095        shape.indent.width() + " where ".len() + preds_str.len() + end_length > shape.width {
2096         Some(format!("\n{}where {}",
2097                      (shape.indent + extra_indent).to_string(context.config),
2098                      preds_str))
2099     } else {
2100         Some(format!(" where {}", preds_str))
2101     }
2102 }
2103
2104 fn format_header(item_name: &str, ident: ast::Ident, vis: &ast::Visibility) -> String {
2105     format!("{}{}{}", format_visibility(vis), item_name, ident)
2106 }
2107
2108 fn format_generics(context: &RewriteContext,
2109                    generics: &ast::Generics,
2110                    opener: &str,
2111                    terminator: &str,
2112                    brace_style: BraceStyle,
2113                    force_same_line_brace: bool,
2114                    offset: Indent,
2115                    generics_offset: Indent,
2116                    span: Span)
2117                    -> Option<String> {
2118     let mut result = try_opt!(rewrite_generics(context,
2119                                                generics,
2120                                                Shape::legacy(context.config.max_width, offset),
2121                                                generics_offset,
2122                                                span));
2123
2124     if !generics.where_clause.predicates.is_empty() || result.contains('\n') {
2125         let budget = try_opt!(context.config.max_width.checked_sub(last_line_width(&result)));
2126         let where_clause_str = try_opt!(rewrite_where_clause(context,
2127                                                              &generics.where_clause,
2128                                                              brace_style,
2129                                                              Shape::legacy(budget,
2130                                                                            offset.block_only()),
2131                                                              Density::Tall,
2132                                                              terminator,
2133                                                              false,
2134                                                              false,
2135                                                              Some(span.hi)));
2136         result.push_str(&where_clause_str);
2137         if !force_same_line_brace &&
2138            (brace_style == BraceStyle::SameLineWhere || brace_style == BraceStyle::AlwaysNextLine) {
2139             result.push('\n');
2140             result.push_str(&offset.block_only().to_string(context.config));
2141         } else {
2142             result.push(' ');
2143         }
2144         result.push_str(opener);
2145     } else {
2146         if !force_same_line_brace && brace_style == BraceStyle::AlwaysNextLine {
2147             result.push('\n');
2148             result.push_str(&offset.block_only().to_string(context.config));
2149         } else {
2150             result.push(' ');
2151         }
2152         result.push_str(opener);
2153     }
2154
2155     Some(result)
2156 }