src/items.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 // Formatting top-level items - functions, structs, enums, traits, impls.
  12
  13 use {Indent, Shape};
  14 use codemap::SpanUtils;
  15 use utils::{format_mutability, format_visibility, contains_skip, end_typaram, wrap_str,
  16             last_line_width, format_unsafety, trim_newlines, stmt_expr, semicolon_for_expr,
  17             trimmed_last_line_width};
  18 use lists::{write_list, itemize_list, ListItem, ListFormatting, SeparatorTactic, list_helper,
  19             DefinitiveListTactic, ListTactic, definitive_tactic, format_item_list};
  20 use expr::{is_empty_block, is_simple_block_stmt, rewrite_assign_rhs, type_annotation_separator};
  21 use comment::{FindUncommented, contains_comment};
  22 use visitor::FmtVisitor;
  23 use rewrite::{Rewrite, RewriteContext};
  24 use config::{Config, IndentStyle, Density, ReturnIndent, BraceStyle, Style, TypeDensity};
  25 use itertools::Itertools;
  26
  27 use syntax::{ast, abi, codemap, ptr, symbol};
  28 use syntax::codemap::{Span, BytePos, mk_sp};
  29 use syntax::ast::ImplItem;
  30
  31 // Statements of the form
  32 // let pat: ty = init;
  33 impl Rewrite for ast::Local {
  34     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
  35         debug!("Local::rewrite {:?} {} {:?}",
  36                self,
  37                shape.width,
  38                shape.indent);
  39         let mut result = "let ".to_owned();
  40
  41         // 4 = "let ".len()
  42         let pat_shape = try_opt!(shape.offset_left(4));
  43         // 1 = ;
  44         let pat_shape = try_opt!(pat_shape.sub_width(1));
  45         let pat_str = try_opt!(self.pat.rewrite(&context, pat_shape));
  46         result.push_str(&pat_str);
  47
  48         // String that is placed within the assignment pattern and expression.
  49         let infix = {
  50             let mut infix = String::new();
  51
  52             if let Some(ref ty) = self.ty {
  53                 let separator = type_annotation_separator(context.config);
  54                 let indent = shape.indent + last_line_width(&result) + separator.len();
  55                 // 1 = ;
  56                 let budget = try_opt!(shape.width.checked_sub(indent.width() + 1));
  57                 let rewrite = try_opt!(ty.rewrite(context, Shape::legacy(budget, indent)));
  58
  59                 infix.push_str(separator);
  60                 infix.push_str(&rewrite);
  61             }
  62
  63             if self.init.is_some() {
  64                 infix.push_str(" =");
  65             }
  66
  67             infix
  68         };
  69
  70         result.push_str(&infix);
  71
  72         if let Some(ref ex) = self.init {
  73             // 1 = trailing semicolon;
  74             let nested_shape = try_opt!(shape.sub_width(1));
  75
  76             result = try_opt!(rewrite_assign_rhs(&context, result, ex, nested_shape));
  77         }
  78
  79         result.push(';');
  80         Some(result)
  81     }
  82 }
  83
  84 // TODO convert to using rewrite style rather than visitor
  85 // TODO format modules in this style
  86 #[allow(dead_code)]
  87 struct Item<'a> {
  88     keyword: &'static str,
  89     abi: String,
  90     vis: Option<&'a ast::Visibility>,
  91     body: Vec<BodyElement<'a>>,
  92     span: Span,
  93 }
  94
  95 impl<'a> Item<'a> {
  96     fn from_foreign_mod(fm: &'a ast::ForeignMod, span: Span, config: &Config) -> Item<'a> {
  97         let abi = if fm.abi == abi::Abi::C && !config.force_explicit_abi() {
  98             "extern".into()
  99         } else {
 100             format!("extern {}", fm.abi)
 101         };
 102         Item {
 103             keyword: "",
 104             abi: abi,
 105             vis: None,
 106             body: fm.items
 107                 .iter()
 108                 .map(|i| BodyElement::ForeignItem(i))
 109                 .collect(),
 110             span: span,
 111         }
 112     }
 113 }
 114
 115 enum BodyElement<'a> {
 116     // Stmt(&'a ast::Stmt),
 117     // Field(&'a ast::Field),
 118     // Variant(&'a ast::Variant),
 119     // Item(&'a ast::Item),
 120     ForeignItem(&'a ast::ForeignItem),
 121 }
 122
 123 impl<'a> FmtVisitor<'a> {
 124     fn format_item(&mut self, item: Item) {
 125         self.buffer.push_str(&item.abi);
 126         self.buffer.push_str(" ");
 127
 128         let snippet = self.snippet(item.span);
 129         let brace_pos = snippet.find_uncommented("{").unwrap();
 130
 131         self.buffer.push_str("{");
 132         if !item.body.is_empty() || contains_comment(&snippet[brace_pos..]) {
 133             // FIXME: this skips comments between the extern keyword and the opening
 134             // brace.
 135             self.last_pos = item.span.lo + BytePos(brace_pos as u32 + 1);
 136             self.block_indent = self.block_indent.block_indent(self.config);
 137
 138             if item.body.is_empty() {
 139                 self.format_missing_no_indent(item.span.hi - BytePos(1));
 140                 self.block_indent = self.block_indent.block_unindent(self.config);
 141
 142                 self.buffer
 143                     .push_str(&self.block_indent.to_string(self.config));
 144             } else {
 145                 for item in &item.body {
 146                     self.format_body_element(item);
 147                 }
 148
 149                 self.block_indent = self.block_indent.block_unindent(self.config);
 150                 self.format_missing_with_indent(item.span.hi - BytePos(1));
 151             }
 152         }
 153
 154         self.buffer.push_str("}");
 155         self.last_pos = item.span.hi;
 156     }
 157
 158     fn format_body_element(&mut self, element: &BodyElement) {
 159         match *element {
 160             BodyElement::ForeignItem(ref item) => self.format_foreign_item(item),
 161         }
 162     }
 163
 164     pub fn format_foreign_mod(&mut self, fm: &ast::ForeignMod, span: Span) {
 165         let item = Item::from_foreign_mod(fm, span, self.config);
 166         self.format_item(item);
 167     }
 168
 169     fn format_foreign_item(&mut self, item: &ast::ForeignItem) {
 170         self.format_missing_with_indent(item.span.lo);
 171         // Drop semicolon or it will be interpreted as comment.
 172         // FIXME: this may be a faulty span from libsyntax.
 173         let span = mk_sp(item.span.lo, item.span.hi - BytePos(1));
 174
 175         match item.node {
 176             ast::ForeignItemKind::Fn(ref fn_decl, ref generics) => {
 177                 let indent = self.block_indent;
 178                 let rewrite = rewrite_fn_base(&self.get_context(),
 179                                               indent,
 180                                               item.ident,
 181                                               fn_decl,
 182                                               generics,
 183                                               ast::Unsafety::Normal,
 184                                               ast::Constness::NotConst,
 185                                               ast::Defaultness::Final,
 186                                               // These are not actually rust functions,
 187                                               // but we format them as such.
 188                                               abi::Abi::Rust,
 189                                               &item.vis,
 190                                               span,
 191                                               false,
 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 shape = Shape::indented(offset, self.config).sub_width(1).unwrap();
 212                 let rewrite = ty.rewrite(&self.get_context(), shape);
 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                                                                          true));
 262
 263         if self.config.fn_brace_style() != BraceStyle::AlwaysNextLine && !result.contains('\n') {
 264             newline_brace = false;
 265         } else if force_newline_brace {
 266             newline_brace = true;
 267         }
 268
 269         // Prepare for the function body by possibly adding a newline and
 270         // indent.
 271         // FIXME we'll miss anything between the end of the signature and the
 272         // start of the body, but we need more spans from the compiler to solve
 273         // this.
 274         if newline_brace {
 275             result.push('\n');
 276             result.push_str(&indent.to_string(self.config));
 277         } else {
 278             result.push(' ');
 279         }
 280
 281         self.single_line_fn(&result, block).or_else(|| Some(result))
 282     }
 283
 284     pub fn rewrite_required_fn(&mut self,
 285                                indent: Indent,
 286                                ident: ast::Ident,
 287                                sig: &ast::MethodSig,
 288                                span: Span)
 289                                -> Option<String> {
 290         // Drop semicolon or it will be interpreted as comment.
 291         let span = mk_sp(span.lo, span.hi - BytePos(1));
 292         let context = self.get_context();
 293
 294         let (mut result, _) = try_opt!(rewrite_fn_base(&context,
 295                                                        indent,
 296                                                        ident,
 297                                                        &sig.decl,
 298                                                        &sig.generics,
 299                                                        sig.unsafety,
 300                                                        sig.constness.node,
 301                                                        ast::Defaultness::Final,
 302                                                        sig.abi,
 303                                                        &ast::Visibility::Inherited,
 304                                                        span,
 305                                                        false,
 306                                                        false,
 307                                                        false));
 308
 309         // Re-attach semicolon
 310         result.push(';');
 311
 312         Some(result)
 313     }
 314
 315     fn single_line_fn(&self, fn_str: &str, block: &ast::Block) -> Option<String> {
 316         if fn_str.contains('\n') {
 317             return None;
 318         }
 319
 320         let codemap = self.get_context().codemap;
 321
 322         if self.config.fn_empty_single_line() && is_empty_block(block, codemap) &&
 323            self.block_indent.width() + fn_str.len() + 2 <= self.config.max_width() {
 324             return Some(format!("{}{{}}", fn_str));
 325         }
 326
 327         if self.config.fn_single_line() && is_simple_block_stmt(block, codemap) {
 328             let rewrite = {
 329                 if let Some(ref stmt) = block.stmts.first() {
 330                     match stmt_expr(stmt) {
 331                         Some(e) => {
 332                             let suffix = if semicolon_for_expr(e) { ";" } else { "" };
 333
 334                             e.rewrite(&self.get_context(),
 335                                          Shape::indented(self.block_indent, self.config))
 336                                 .map(|s| s + suffix)
 337                                 .or_else(|| Some(self.snippet(e.span)))
 338                         }
 339                         None => {
 340                             stmt.rewrite(&self.get_context(),
 341                                          Shape::indented(self.block_indent, self.config))
 342                         }
 343                     }
 344                 } else {
 345                     None
 346                 }
 347             };
 348
 349             if let Some(res) = rewrite {
 350                 let width = self.block_indent.width() + fn_str.len() + res.len() + 4;
 351                 if !res.contains('\n') && width <= self.config.max_width() {
 352                     return Some(format!("{}{{ {} }}", fn_str, res));
 353                 }
 354             }
 355         }
 356
 357         None
 358     }
 359
 360     pub fn visit_enum(&mut self,
 361                       ident: ast::Ident,
 362                       vis: &ast::Visibility,
 363                       enum_def: &ast::EnumDef,
 364                       generics: &ast::Generics,
 365                       span: Span) {
 366         self.buffer.push_str(&format_header("enum ", ident, vis));
 367
 368         let enum_snippet = self.snippet(span);
 369         let brace_pos = enum_snippet.find_uncommented("{").unwrap();
 370         let body_start = span.lo + BytePos(brace_pos as u32 + 1);
 371         let generics_str = format_generics(&self.get_context(),
 372                                            generics,
 373                                            "{",
 374                                            "{",
 375                                            self.config.item_brace_style(),
 376                                            enum_def.variants.is_empty(),
 377                                            self.block_indent,
 378                                            mk_sp(span.lo, body_start))
 379                 .unwrap();
 380         self.buffer.push_str(&generics_str);
 381
 382         self.last_pos = body_start;
 383
 384         self.block_indent = self.block_indent.block_indent(self.config);
 385         let variant_list = self.format_variant_list(enum_def, body_start, span.hi - BytePos(1));
 386         match variant_list {
 387             Some(ref body_str) => self.buffer.push_str(body_str),
 388             None => {
 389                 if contains_comment(&enum_snippet[brace_pos..]) {
 390                     self.format_missing_no_indent(span.hi - BytePos(1))
 391                 } else {
 392                     self.format_missing(span.hi - BytePos(1))
 393                 }
 394             }
 395         }
 396         self.block_indent = self.block_indent.block_unindent(self.config);
 397
 398         if variant_list.is_some() || contains_comment(&enum_snippet[brace_pos..]) {
 399             self.buffer
 400                 .push_str(&self.block_indent.to_string(self.config));
 401         }
 402         self.buffer.push_str("}");
 403         self.last_pos = span.hi;
 404     }
 405
 406     // Format the body of an enum definition
 407     fn format_variant_list(&self,
 408                            enum_def: &ast::EnumDef,
 409                            body_lo: BytePos,
 410                            body_hi: BytePos)
 411                            -> Option<String> {
 412         if enum_def.variants.is_empty() {
 413             return None;
 414         }
 415         let mut result = String::with_capacity(1024);
 416         result.push('\n');
 417         let indentation = self.block_indent.to_string(self.config);
 418         result.push_str(&indentation);
 419
 420         let items = itemize_list(self.codemap,
 421                                  enum_def.variants.iter(),
 422                                  "}",
 423                                  |f| if !f.node.attrs.is_empty() {
 424                                      f.node.attrs[0].span.lo
 425                                  } else {
 426                                      f.span.lo
 427                                  },
 428                                  |f| f.span.hi,
 429                                  |f| self.format_variant(f),
 430                                  body_lo,
 431                                  body_hi);
 432
 433         let shape = Shape::indented(self.block_indent, self.config)
 434             .sub_width(2)
 435             .unwrap();
 436         let fmt = ListFormatting {
 437             tactic: DefinitiveListTactic::Vertical,
 438             separator: ",",
 439             trailing_separator: self.config.trailing_comma(),
 440             shape: shape,
 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
 461                                       .node
 462                                       .attrs
 463                                       .rewrite(&self.get_context(),
 464                                                Shape::indented(indent, self.config)));
 465         if !result.is_empty() {
 466             result.push('\n');
 467             result.push_str(&indent.to_string(self.config));
 468         }
 469
 470         let context = self.get_context();
 471         let variant_body = match field.node.data {
 472             ast::VariantData::Tuple(..) |
 473             ast::VariantData::Struct(..) => {
 474                 // FIXME: Should limit the width, as we have a trailing comma
 475                 format_struct(&context,
 476                               "",
 477                               field.node.name,
 478                               &ast::Visibility::Inherited,
 479                               &field.node.data,
 480                               None,
 481                               field.span,
 482                               indent,
 483                               Some(self.config.struct_variant_width()))
 484             }
 485             ast::VariantData::Unit(..) => {
 486                 let tag = if let Some(ref expr) = field.node.disr_expr {
 487                     format!("{} = {}", field.node.name, self.snippet(expr.span))
 488                 } else {
 489                     field.node.name.to_string()
 490                 };
 491
 492                 wrap_str(tag,
 493                          self.config.max_width(),
 494                          Shape::indented(indent, self.config))
 495             }
 496         };
 497
 498         if let Some(variant_str) = variant_body {
 499             result.push_str(&variant_str);
 500             Some(result)
 501         } else {
 502             None
 503         }
 504     }
 505 }
 506
 507 pub fn format_impl(context: &RewriteContext, item: &ast::Item, offset: Indent) -> Option<String> {
 508     if let ast::ItemKind::Impl(_, _, ref generics, ref trait_ref, _, ref items) = item.node {
 509         let mut result = String::new();
 510         // First try to format the ref and type without a split at the 'for'.
 511         let mut ref_and_type = try_opt!(format_impl_ref_and_type(context, item, offset, false));
 512
 513         // If there is a line break present in the first result format it again
 514         // with a split at the 'for'. Skip this if there is no trait ref and
 515         // therefore no 'for'.
 516         if ref_and_type.contains('\n') && trait_ref.is_some() {
 517             ref_and_type = try_opt!(format_impl_ref_and_type(context, item, offset, true));
 518         }
 519         result.push_str(&ref_and_type);
 520
 521         let where_budget = try_opt!(context
 522                                         .config
 523                                         .max_width()
 524                                         .checked_sub(last_line_width(&result)));
 525         let where_clause_str = try_opt!(rewrite_where_clause(context,
 526                                                              &generics.where_clause,
 527                                                              context.config.item_brace_style(),
 528                                                              Shape::legacy(where_budget,
 529                                                                            offset.block_only()),
 530                                                              context.config.where_density(),
 531                                                              "{",
 532                                                              false,
 533                                                              last_line_width(&ref_and_type) == 1,
 534                                                              None));
 535
 536         if try_opt!(is_impl_single_line(context, &items, &result, &where_clause_str, &item)) {
 537             result.push_str(&where_clause_str);
 538             if where_clause_str.contains('\n') {
 539                 let white_space = offset.to_string(context.config);
 540                 result.push_str(&format!("\n{}{{\n{}}}", &white_space, &white_space));
 541             } else {
 542                 result.push_str(" {}");
 543             }
 544             return Some(result);
 545         }
 546
 547         if !where_clause_str.is_empty() && !where_clause_str.contains('\n') {
 548             result.push('\n');
 549             let width = offset.block_indent + context.config.tab_spaces() - 1;
 550             let where_indent = Indent::new(0, width);
 551             result.push_str(&where_indent.to_string(context.config));
 552         }
 553         result.push_str(&where_clause_str);
 554
 555         match context.config.item_brace_style() {
 556             BraceStyle::AlwaysNextLine => {
 557                 result.push('\n');
 558                 result.push_str(&offset.to_string(context.config));
 559             }
 560             BraceStyle::PreferSameLine => result.push(' '),
 561             BraceStyle::SameLineWhere => {
 562                 if !where_clause_str.is_empty() {
 563                     result.push('\n');
 564                     result.push_str(&offset.to_string(context.config));
 565                 } else {
 566                     result.push(' ');
 567                 }
 568             }
 569         }
 570
 571         result.push('{');
 572
 573         let snippet = context.snippet(item.span);
 574         let open_pos = try_opt!(snippet.find_uncommented("{")) + 1;
 575
 576         if !items.is_empty() || contains_comment(&snippet[open_pos..]) {
 577             let mut visitor = FmtVisitor::from_codemap(context.parse_session, context.config);
 578             visitor.block_indent = offset.block_only().block_indent(context.config);
 579             visitor.last_pos = item.span.lo + BytePos(open_pos as u32);
 580
 581             for item in items {
 582                 visitor.visit_impl_item(item);
 583             }
 584
 585             visitor.format_missing(item.span.hi - BytePos(1));
 586
 587             let inner_indent_str = visitor.block_indent.to_string(context.config);
 588             let outer_indent_str = offset.block_only().to_string(context.config);
 589
 590             result.push('\n');
 591             result.push_str(&inner_indent_str);
 592             result.push_str(trim_newlines(visitor.buffer.to_string().trim()));
 593             result.push('\n');
 594             result.push_str(&outer_indent_str);
 595         }
 596
 597         if result.chars().last().unwrap() == '{' {
 598             result.push('\n');
 599             result.push_str(&offset.to_string(context.config));
 600         }
 601         result.push('}');
 602
 603         Some(result)
 604     } else {
 605         unreachable!();
 606     }
 607 }
 608
 609 fn is_impl_single_line(context: &RewriteContext,
 610                        items: &[ImplItem],
 611                        result: &str,
 612                        where_clause_str: &str,
 613                        item: &ast::Item)
 614                        -> Option<bool> {
 615     let snippet = context.snippet(item.span);
 616     let open_pos = try_opt!(snippet.find_uncommented("{")) + 1;
 617
 618     Some(context.config.impl_empty_single_line() && items.is_empty() &&
 619          result.len() + where_clause_str.len() <= context.config.max_width() &&
 620          !contains_comment(&snippet[open_pos..]))
 621 }
 622
 623 fn format_impl_ref_and_type(context: &RewriteContext,
 624                             item: &ast::Item,
 625                             offset: Indent,
 626                             split_at_for: bool)
 627                             -> Option<String> {
 628     if let ast::ItemKind::Impl(unsafety, polarity, ref generics, ref trait_ref, ref self_ty, _) =
 629         item.node {
 630         let mut result = String::new();
 631
 632         result.push_str(&format_visibility(&item.vis));
 633         result.push_str(format_unsafety(unsafety));
 634         result.push_str("impl");
 635
 636         let lo = context.codemap.span_after(item.span, "impl");
 637         let hi = match *trait_ref {
 638             Some(ref tr) => tr.path.span.lo,
 639             None => self_ty.span.lo,
 640         };
 641         let generics_indent = offset + last_line_width(&result);
 642         let shape = Shape::indented(generics_indent, context.config);
 643         let generics_str = try_opt!(rewrite_generics(context, generics, shape, mk_sp(lo, hi)));
 644         result.push_str(&generics_str);
 645
 646         if polarity == ast::ImplPolarity::Negative {
 647             result.push_str(" !");
 648         }
 649         if let Some(ref trait_ref) = *trait_ref {
 650             if polarity != ast::ImplPolarity::Negative {
 651                 result.push_str(" ");
 652             }
 653             let used_space = last_line_width(&result);
 654             let budget = try_opt!(context.config.max_width().checked_sub(used_space));
 655             let indent = offset + used_space;
 656             result.push_str(&*try_opt!(trait_ref.rewrite(context, Shape::legacy(budget, indent))));
 657
 658             if split_at_for {
 659                 result.push('\n');
 660
 661                 // Add indentation of one additional tab.
 662                 let width = offset.block_indent + context.config.tab_spaces();
 663                 let for_indent = Indent::new(0, width);
 664                 result.push_str(&for_indent.to_string(context.config));
 665
 666                 result.push_str("for");
 667             } else {
 668                 result.push_str(" for");
 669             }
 670         }
 671
 672         let mut used_space = last_line_width(&result);
 673         if generics.where_clause.predicates.is_empty() {
 674             // If there is no where clause adapt budget for type formatting to take space and curly
 675             // brace into account.
 676             match context.config.item_brace_style() {
 677                 BraceStyle::AlwaysNextLine => {}
 678                 BraceStyle::PreferSameLine => used_space += 2,
 679                 BraceStyle::SameLineWhere => used_space += 2,
 680             }
 681         }
 682
 683         // 1 = space before the type.
 684         let budget = try_opt!(context.config.max_width().checked_sub(used_space + 1));
 685         let indent = offset + result.len() + 1;
 686         let self_ty_str = self_ty.rewrite(context, Shape::legacy(budget, indent));
 687         if let Some(self_ty_str) = self_ty_str {
 688             result.push_str(" ");
 689             result.push_str(&self_ty_str);
 690             return Some(result);
 691         }
 692
 693         // Can't fit the self type on what's left of the line, so start a new one.
 694         let indent = offset.block_indent(context.config);
 695         result.push_str(&format!("\n{}", indent.to_string(context.config)));
 696         result.push_str(&*try_opt!(self_ty.rewrite(context,
 697                                                    Shape::indented(indent, context.config))));
 698         Some(result)
 699     } else {
 700         unreachable!();
 701     }
 702 }
 703
 704 pub fn format_struct(context: &RewriteContext,
 705                      item_name: &str,
 706                      ident: ast::Ident,
 707                      vis: &ast::Visibility,
 708                      struct_def: &ast::VariantData,
 709                      generics: Option<&ast::Generics>,
 710                      span: Span,
 711                      offset: Indent,
 712                      one_line_width: Option<usize>)
 713                      -> Option<String> {
 714     match *struct_def {
 715         ast::VariantData::Unit(..) => Some(format_unit_struct(item_name, ident, vis)),
 716         ast::VariantData::Tuple(ref fields, _) => {
 717             format_tuple_struct(context,
 718                                 item_name,
 719                                 ident,
 720                                 vis,
 721                                 fields,
 722                                 generics,
 723                                 span,
 724                                 offset)
 725         }
 726         ast::VariantData::Struct(ref fields, _) => {
 727             format_struct_struct(context,
 728                                  item_name,
 729                                  ident,
 730                                  vis,
 731                                  fields,
 732                                  generics,
 733                                  span,
 734                                  offset,
 735                                  one_line_width)
 736         }
 737     }
 738 }
 739
 740 pub fn format_trait(context: &RewriteContext, item: &ast::Item, offset: Indent) -> Option<String> {
 741     if let ast::ItemKind::Trait(unsafety, ref generics, ref type_param_bounds, ref trait_items) =
 742         item.node {
 743         let mut result = String::new();
 744         let header = format!("{}{}trait {}",
 745                              format_visibility(&item.vis),
 746                              format_unsafety(unsafety),
 747                              item.ident);
 748
 749         result.push_str(&header);
 750
 751         let body_lo = context.codemap.span_after(item.span, "{");
 752
 753         let generics_indent = offset + last_line_width(&result);
 754         let shape = Shape::indented(generics_indent, context.config);
 755         let generics_str =
 756             try_opt!(rewrite_generics(context, generics, shape, 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.comment_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() == IndentStyle::Block)) ||
 779                (context.config.fn_args_layout() == IndentStyle::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
 788                                         .config
 789                                         .max_width()
 790                                         .checked_sub(last_line_width(&result)));
 791         let where_clause_str = try_opt!(rewrite_where_clause(context,
 792                                                              &generics.where_clause,
 793                                                              context.config.item_brace_style(),
 794                                                              Shape::legacy(where_budget,
 795                                                                            offset.block_only()),
 796                                                              where_density,
 797                                                              "{",
 798                                                              !has_body,
 799                                                              trait_bound_str.is_empty() &&
 800                                                              last_line_width(&generics_str) == 1,
 801                                                              None));
 802         // If the where clause cannot fit on the same line,
 803         // put the where clause on a new line
 804         if !where_clause_str.contains('\n') &&
 805            last_line_width(&result) + where_clause_str.len() + offset.width() >
 806            context.config.comment_width() {
 807             result.push('\n');
 808             let width = offset.block_indent + context.config.tab_spaces() - 1;
 809             let where_indent = Indent::new(0, width);
 810             result.push_str(&where_indent.to_string(context.config));
 811         }
 812         result.push_str(&where_clause_str);
 813
 814         match context.config.item_brace_style() {
 815             BraceStyle::AlwaysNextLine => {
 816                 result.push('\n');
 817                 result.push_str(&offset.to_string(context.config));
 818             }
 819             BraceStyle::PreferSameLine => result.push(' '),
 820             BraceStyle::SameLineWhere => {
 821                 if !where_clause_str.is_empty() &&
 822                    (!trait_items.is_empty() || result.contains('\n')) {
 823                     result.push('\n');
 824                     result.push_str(&offset.to_string(context.config));
 825                 } else {
 826                     result.push(' ');
 827                 }
 828             }
 829         }
 830         result.push('{');
 831
 832         let snippet = context.snippet(item.span);
 833         let open_pos = try_opt!(snippet.find_uncommented("{")) + 1;
 834
 835         if !trait_items.is_empty() || contains_comment(&snippet[open_pos..]) {
 836             let mut visitor = FmtVisitor::from_codemap(context.parse_session, context.config);
 837             visitor.block_indent = offset.block_only().block_indent(context.config);
 838             visitor.last_pos = item.span.lo + BytePos(open_pos as u32);
 839
 840             for item in trait_items {
 841                 visitor.visit_trait_item(item);
 842             }
 843
 844             visitor.format_missing(item.span.hi - BytePos(1));
 845
 846             let inner_indent_str = visitor.block_indent.to_string(context.config);
 847             let outer_indent_str = offset.block_only().to_string(context.config);
 848
 849             result.push('\n');
 850             result.push_str(&inner_indent_str);
 851             result.push_str(trim_newlines(visitor.buffer.to_string().trim()));
 852             result.push('\n');
 853             result.push_str(&outer_indent_str);
 854         } else if result.contains('\n') {
 855             result.push('\n');
 856         }
 857
 858         result.push('}');
 859         Some(result)
 860     } else {
 861         unreachable!();
 862     }
 863 }
 864
 865 fn format_unit_struct(item_name: &str, ident: ast::Ident, vis: &ast::Visibility) -> String {
 866     format!("{};", format_header(item_name, ident, vis))
 867 }
 868
 869 fn format_struct_struct(context: &RewriteContext,
 870                         item_name: &str,
 871                         ident: ast::Ident,
 872                         vis: &ast::Visibility,
 873                         fields: &[ast::StructField],
 874                         generics: Option<&ast::Generics>,
 875                         span: Span,
 876                         offset: Indent,
 877                         one_line_width: Option<usize>)
 878                         -> Option<String> {
 879     let mut result = String::with_capacity(1024);
 880
 881     let header_str = format_header(item_name, ident, vis);
 882     result.push_str(&header_str);
 883
 884     let body_lo = context.codemap.span_after(span, "{");
 885
 886     let generics_str = match generics {
 887         Some(g) => {
 888             try_opt!(format_generics(context,
 889                                      g,
 890                                      "{",
 891                                      "{",
 892                                      context.config.item_brace_style(),
 893                                      fields.is_empty(),
 894                                      offset,
 895                                      mk_sp(span.lo, body_lo)))
 896         }
 897         None => {
 898             if context.config.item_brace_style() == BraceStyle::AlwaysNextLine &&
 899                !fields.is_empty() {
 900                 format!("\n{}{{", offset.block_only().to_string(context.config))
 901             } else {
 902                 " {".to_owned()
 903             }
 904         }
 905     };
 906     result.push_str(&generics_str);
 907
 908     if fields.is_empty() {
 909         let snippet = context.snippet(mk_sp(body_lo, span.hi - BytePos(1)));
 910         if snippet.trim().is_empty() {
 911             // `struct S {}`
 912         } else if snippet.trim_right_matches(&[' ', '\t'][..]).ends_with('\n') {
 913             // fix indent
 914             result.push_str(&snippet.trim_right());
 915             result.push('\n');
 916             result.push_str(&offset.to_string(context.config));
 917         } else {
 918             result.push_str(&snippet);
 919         }
 920         result.push('}');
 921         return Some(result);
 922     }
 923
 924     let item_indent = offset.block_indent(context.config);
 925     // 1 = ","
 926     let item_budget = try_opt!(context
 927                                    .config
 928                                    .max_width()
 929                                    .checked_sub(item_indent.width() + 1));
 930
 931     let items =
 932         itemize_list(context.codemap,
 933                      fields.iter(),
 934                      "}",
 935                      |field| {
 936                          // Include attributes and doc comments, if present
 937                          if !field.attrs.is_empty() {
 938                              field.attrs[0].span.lo
 939                          } else {
 940                              field.span.lo
 941                          }
 942                      },
 943                      |field| field.ty.span.hi,
 944                      |field| field.rewrite(context, Shape::legacy(item_budget, item_indent)),
 945                      context.codemap.span_after(span, "{"),
 946                      span.hi)
 947                 .collect::<Vec<_>>();
 948     // 1 = ,
 949     let budget = context.config.max_width() - offset.width() + context.config.tab_spaces() - 1;
 950
 951     let tactic = match one_line_width {
 952         Some(w) => definitive_tactic(&items, ListTactic::LimitedHorizontalVertical(w), budget),
 953         None => DefinitiveListTactic::Vertical,
 954     };
 955
 956     let fmt = ListFormatting {
 957         tactic: tactic,
 958         separator: ",",
 959         trailing_separator: context.config.trailing_comma(),
 960         shape: Shape::legacy(budget, item_indent),
 961         ends_with_newline: true,
 962         config: context.config,
 963     };
 964     let items_str = try_opt!(write_list(&items, &fmt));
 965     if one_line_width.is_some() && !items_str.contains('\n') {
 966         Some(format!("{} {} }}", result, items_str))
 967     } else {
 968         Some(format!("{}\n{}{}\n{}}}",
 969                      result,
 970                      offset
 971                          .block_indent(context.config)
 972                          .to_string(context.config),
 973                      items_str,
 974                      offset.to_string(context.config)))
 975     }
 976 }
 977
 978 fn format_tuple_struct(context: &RewriteContext,
 979                        item_name: &str,
 980                        ident: ast::Ident,
 981                        vis: &ast::Visibility,
 982                        fields: &[ast::StructField],
 983                        generics: Option<&ast::Generics>,
 984                        span: Span,
 985                        offset: Indent)
 986                        -> Option<String> {
 987     let mut result = String::with_capacity(1024);
 988
 989     let header_str = format_header(item_name, ident, vis);
 990     result.push_str(&header_str);
 991
 992     let body_lo = if fields.is_empty() {
 993         context.codemap.span_after(span, "(")
 994     } else {
 995         fields[0].span.lo
 996     };
 997
 998     let where_clause_str = match generics {
 999         Some(generics) => {
1000             let generics_indent = offset + last_line_width(&header_str);
1001             let shape = Shape::indented(generics_indent, context.config);
1002             let generics_str =
1003                 try_opt!(rewrite_generics(context, generics, shape, mk_sp(span.lo, body_lo)));
1004             result.push_str(&generics_str);
1005
1006             let where_budget = try_opt!(context
1007                                             .config
1008                                             .max_width()
1009                                             .checked_sub(last_line_width(&result)));
1010             try_opt!(rewrite_where_clause(context,
1011                                           &generics.where_clause,
1012                                           context.config.item_brace_style(),
1013                                           Shape::legacy(where_budget, offset.block_only()),
1014                                           Density::Compressed,
1015                                           ";",
1016                                           true,
1017                                           false,
1018                                           None))
1019         }
1020         None => "".to_owned(),
1021     };
1022
1023     if fields.is_empty() {
1024         result.push('(');
1025         let snippet = context.snippet(mk_sp(body_lo, context.codemap.span_before(span, ")")));
1026         if snippet.is_empty() {
1027             // `struct S ()`
1028         } else if snippet.trim_right_matches(&[' ', '\t'][..]).ends_with('\n') {
1029             result.push_str(&snippet.trim_right());
1030             result.push('\n');
1031             result.push_str(&offset.to_string(context.config));
1032         } else {
1033             result.push_str(&snippet);
1034         }
1035         result.push(')');
1036     } else {
1037         let (tactic, item_indent) = match context.config.fn_args_layout() {
1038             IndentStyle::Visual => {
1039                 // 1 = `(`
1040                 (ListTactic::HorizontalVertical, offset.block_only() + result.len() + 1)
1041             }
1042             IndentStyle::Block => {
1043                 (ListTactic::HorizontalVertical, offset.block_only().block_indent(&context.config))
1044             }
1045         };
1046         // 3 = `();`
1047         let item_budget = try_opt!(context
1048                                        .config
1049                                        .max_width()
1050                                        .checked_sub(item_indent.width() + 3));
1051
1052         let items =
1053             itemize_list(context.codemap,
1054                          fields.iter(),
1055                          ")",
1056                          |field| {
1057                              // Include attributes and doc comments, if present
1058                              if !field.attrs.is_empty() {
1059                                  field.attrs[0].span.lo
1060                              } else {
1061                                  field.span.lo
1062                              }
1063                          },
1064                          |field| field.ty.span.hi,
1065                          |field| field.rewrite(context, Shape::legacy(item_budget, item_indent)),
1066                          context.codemap.span_after(span, "("),
1067                          span.hi);
1068         let body_budget = try_opt!(context
1069                                        .config
1070                                        .max_width()
1071                                        .checked_sub(offset.block_only().width() + result.len() +
1072                                                     3));
1073         let body = try_opt!(list_helper(items,
1074                                         // TODO budget is wrong in block case
1075                                         Shape::legacy(body_budget, item_indent),
1076                                         context.config,
1077                                         tactic));
1078
1079         if context.config.fn_args_layout() == IndentStyle::Visual || !body.contains('\n') {
1080             result.push('(');
1081             if context.config.spaces_within_parens() && body.len() > 0 {
1082                 result.push(' ');
1083             }
1084
1085             result.push_str(&body);
1086
1087             if context.config.spaces_within_parens() && body.len() > 0 {
1088                 result.push(' ');
1089             }
1090             result.push(')');
1091         } else {
1092             result.push_str("(\n");
1093             result.push_str(&item_indent.to_string(&context.config));
1094             result.push_str(&body);
1095             result.push('\n');
1096             result.push_str(&offset.block_only().to_string(&context.config));
1097             result.push(')');
1098         }
1099     }
1100
1101     if !where_clause_str.is_empty() && !where_clause_str.contains('\n') &&
1102        (result.contains('\n') ||
1103         offset.block_indent + result.len() + where_clause_str.len() + 1 >
1104         context.config.max_width()) {
1105         // We need to put the where clause on a new line, but we didn't
1106         // know that earlier, so the where clause will not be indented properly.
1107         result.push('\n');
1108         result.push_str(&(offset.block_only() + (context.config.tab_spaces() - 1))
1109                             .to_string(context.config));
1110     }
1111     result.push_str(&where_clause_str);
1112
1113     Some(result)
1114 }
1115
1116 pub fn rewrite_type_alias(context: &RewriteContext,
1117                           indent: Indent,
1118                           ident: ast::Ident,
1119                           ty: &ast::Ty,
1120                           generics: &ast::Generics,
1121                           vis: &ast::Visibility,
1122                           span: Span)
1123                           -> Option<String> {
1124     let mut result = String::new();
1125
1126     result.push_str(&format_visibility(vis));
1127     result.push_str("type ");
1128     result.push_str(&ident.to_string());
1129
1130     let generics_indent = indent + result.len();
1131     let generics_span = mk_sp(context.codemap.span_after(span, "type"), ty.span.lo);
1132     let shape = try_opt!(Shape::indented(generics_indent, context.config)
1133                              .sub_width(" =".len()));
1134     let generics_str = try_opt!(rewrite_generics(context, generics, shape, generics_span));
1135
1136     result.push_str(&generics_str);
1137
1138     let where_budget = try_opt!(context
1139                                     .config
1140                                     .max_width()
1141                                     .checked_sub(last_line_width(&result)));
1142     let where_clause_str = try_opt!(rewrite_where_clause(context,
1143                                                          &generics.where_clause,
1144                                                          context.config.item_brace_style(),
1145                                                          Shape::legacy(where_budget, indent),
1146                                                          context.config.where_density(),
1147                                                          "=",
1148                                                          true,
1149                                                          true,
1150                                                          Some(span.hi)));
1151     result.push_str(&where_clause_str);
1152     result.push_str(" = ");
1153
1154     let line_width = last_line_width(&result);
1155     // This checked_sub may fail as the extra space after '=' is not taken into account
1156     // In that case the budget is set to 0 which will make ty.rewrite retry on a new line
1157     let budget = context
1158         .config
1159         .max_width()
1160         .checked_sub(indent.width() + line_width + ";".len())
1161         .unwrap_or(0);
1162     let type_indent = indent + line_width;
1163     // Try to fit the type on the same line
1164     let ty_str = try_opt!(ty.rewrite(context, Shape::legacy(budget, type_indent))
1165                               .or_else(|| {
1166         // The line was too short, try to put the type on the next line
1167
1168         // Remove the space after '='
1169         result.pop();
1170         let type_indent = indent.block_indent(context.config);
1171         result.push('\n');
1172         result.push_str(&type_indent.to_string(context.config));
1173         let budget = try_opt!(context
1174                                   .config
1175                                   .max_width()
1176                                   .checked_sub(type_indent.width() + ";".len()));
1177         ty.rewrite(context, Shape::legacy(budget, type_indent))
1178     }));
1179     result.push_str(&ty_str);
1180     result.push_str(";");
1181     Some(result)
1182 }
1183
1184 fn type_annotation_spacing(config: &Config) -> (&str, &str) {
1185     (if config.space_before_type_annotation() {
1186          " "
1187      } else {
1188          ""
1189      },
1190      if config.space_after_type_annotation_colon() {
1191          " "
1192      } else {
1193          ""
1194      })
1195 }
1196
1197 impl Rewrite for ast::StructField {
1198     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
1199         if contains_skip(&self.attrs) {
1200             let span = context.snippet(mk_sp(self.attrs[0].span.lo, self.span.hi));
1201             return wrap_str(span, context.config.max_width(), shape);
1202         }
1203
1204         let name = self.ident;
1205         let vis = format_visibility(&self.vis);
1206         let mut attr_str =
1207             try_opt!(self.attrs
1208                          .rewrite(context, Shape::indented(shape.indent, context.config)));
1209         if !attr_str.is_empty() {
1210             attr_str.push('\n');
1211             attr_str.push_str(&shape.indent.to_string(context.config));
1212         }
1213
1214         let type_annotation_spacing = type_annotation_spacing(context.config);
1215         let mut result = match name {
1216             Some(name) => format!("{}{}{}{}:", attr_str, vis, name, type_annotation_spacing.0),
1217             None => format!("{}{}", attr_str, vis),
1218         };
1219
1220         let type_offset = shape.indent.block_indent(context.config);
1221         let rewrite_type_in_next_line = || {
1222             self.ty
1223                 .rewrite(context, Shape::indented(type_offset, context.config))
1224         };
1225
1226         let last_line_width = last_line_width(&result) + type_annotation_spacing.1.len();
1227         let budget = try_opt!(shape.width.checked_sub(last_line_width));
1228         let ty_rewritten = self.ty
1229             .rewrite(context,
1230                      Shape::legacy(budget, shape.indent + last_line_width));
1231         match ty_rewritten {
1232             Some(ref ty) if ty.contains('\n') => {
1233                 let new_ty = rewrite_type_in_next_line();
1234                 match new_ty {
1235                     Some(ref new_ty) if !new_ty.contains('\n') &&
1236                                         new_ty.len() + type_offset.width() <=
1237                                         context.config.max_width() => {
1238                         Some(format!("{}\n{}{}",
1239                                      result,
1240                                      type_offset.to_string(&context.config),
1241                                      &new_ty))
1242                     }
1243                     _ => {
1244                         if name.is_some() {
1245                             result.push_str(type_annotation_spacing.1);
1246                         }
1247                         Some(result + &ty)
1248                     }
1249                 }
1250             }
1251             Some(ty) => {
1252                 if name.is_some() {
1253                     result.push_str(type_annotation_spacing.1);
1254                 }
1255                 Some(result + &ty)
1256             }
1257             None => {
1258                 let ty = try_opt!(rewrite_type_in_next_line());
1259                 Some(format!("{}\n{}{}",
1260                              result,
1261                              type_offset.to_string(&context.config),
1262                              &ty))
1263             }
1264         }
1265     }
1266 }
1267
1268 pub fn rewrite_static(prefix: &str,
1269                       vis: &ast::Visibility,
1270                       ident: ast::Ident,
1271                       ty: &ast::Ty,
1272                       mutability: ast::Mutability,
1273                       expr_opt: Option<&ptr::P<ast::Expr>>,
1274                       offset: Indent,
1275                       context: &RewriteContext)
1276                       -> Option<String> {
1277     let type_annotation_spacing = type_annotation_spacing(context.config);
1278     let prefix = format!("{}{} {}{}{}:{}",
1279                          format_visibility(vis),
1280                          prefix,
1281                          format_mutability(mutability),
1282                          ident,
1283                          type_annotation_spacing.0,
1284                          type_annotation_spacing.1);
1285     // 2 = " =".len()
1286     let ty_str = try_opt!(ty.rewrite(context,
1287                                      Shape::legacy(context.config.max_width() -
1288                                                    offset.block_indent -
1289                                                    prefix.len() -
1290                                                    2,
1291                                                    offset.block_only())));
1292
1293     if let Some(expr) = expr_opt {
1294         let lhs = format!("{}{} =", prefix, ty_str);
1295         // 1 = ;
1296         let remaining_width = context.config.max_width() - offset.block_indent - 1;
1297         rewrite_assign_rhs(context,
1298                            lhs,
1299                            expr,
1300                            Shape::legacy(remaining_width, offset.block_only()))
1301                 .map(|s| s + ";")
1302     } else {
1303         let lhs = format!("{}{};", prefix, ty_str);
1304         Some(lhs)
1305     }
1306 }
1307
1308 pub fn rewrite_associated_type(ident: ast::Ident,
1309                                ty_opt: Option<&ptr::P<ast::Ty>>,
1310                                ty_param_bounds_opt: Option<&ast::TyParamBounds>,
1311                                context: &RewriteContext,
1312                                indent: Indent)
1313                                -> Option<String> {
1314     let prefix = format!("type {}", ident);
1315
1316     let type_bounds_str =
1317         if let Some(ty_param_bounds) = ty_param_bounds_opt {
1318             let joiner = match context.config.type_punctuation_density() {
1319                 TypeDensity::Compressed => "+",
1320                 TypeDensity::Wide => " + ",
1321             };
1322             let bounds: &[_] = ty_param_bounds;
1323             let bound_str = try_opt!(bounds
1324                                          .iter()
1325                                          .map(|ty_bound| {
1326                 ty_bound.rewrite(context, Shape::legacy(context.config.max_width(), indent))
1327             })
1328                                          .intersperse(Some(joiner.to_string()))
1329                                          .collect::<Option<String>>());
1330             if bounds.len() > 0 {
1331                 format!(": {}", bound_str)
1332             } else {
1333                 String::new()
1334             }
1335         } else {
1336             String::new()
1337         };
1338
1339     if let Some(ty) = ty_opt {
1340         let ty_str = try_opt!(ty.rewrite(context,
1341                                          Shape::legacy(context.config.max_width() -
1342                                                        indent.block_indent -
1343                                                        prefix.len() -
1344                                                        2,
1345                                                        indent.block_only())));
1346         Some(format!("{} = {};", prefix, ty_str))
1347     } else {
1348         Some(format!("{}{};", prefix, type_bounds_str))
1349     }
1350 }
1351
1352 pub fn rewrite_associated_impl_type(ident: ast::Ident,
1353                                     defaultness: ast::Defaultness,
1354                                     ty_opt: Option<&ptr::P<ast::Ty>>,
1355                                     ty_param_bounds_opt: Option<&ast::TyParamBounds>,
1356                                     context: &RewriteContext,
1357                                     indent: Indent)
1358                                     -> Option<String> {
1359     let result =
1360         try_opt!(rewrite_associated_type(ident, ty_opt, ty_param_bounds_opt, context, indent));
1361
1362     match defaultness {
1363         ast::Defaultness::Default => Some(format!("default {}", result)),
1364         _ => Some(result),
1365     }
1366 }
1367
1368 impl Rewrite for ast::FunctionRetTy {
1369     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
1370         match *self {
1371             ast::FunctionRetTy::Default(_) => Some(String::new()),
1372             ast::FunctionRetTy::Ty(ref ty) => {
1373                 let inner_width = try_opt!(shape.width.checked_sub(3));
1374                 ty.rewrite(context, Shape::legacy(inner_width, shape.indent + 3))
1375                     .map(|r| format!("-> {}", r))
1376             }
1377         }
1378     }
1379 }
1380
1381 impl Rewrite for ast::Arg {
1382     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
1383         if is_named_arg(self) {
1384             let mut result = try_opt!(self.pat
1385                                           .rewrite(context,
1386                                                    Shape::legacy(shape.width, shape.indent)));
1387
1388             if self.ty.node != ast::TyKind::Infer {
1389                 if context.config.space_before_type_annotation() {
1390                     result.push_str(" ");
1391                 }
1392                 result.push_str(":");
1393                 if context.config.space_after_type_annotation_colon() {
1394                     result.push_str(" ");
1395                 }
1396                 let max_width = try_opt!(shape.width.checked_sub(result.len()));
1397                 let ty_str = try_opt!(self.ty
1398                                           .rewrite(context,
1399                                                    Shape::legacy(max_width,
1400                                                                  shape.indent + result.len())));
1401                 result.push_str(&ty_str);
1402             }
1403
1404             Some(result)
1405         } else {
1406             self.ty.rewrite(context, shape)
1407         }
1408     }
1409 }
1410
1411 fn rewrite_explicit_self(explicit_self: &ast::ExplicitSelf,
1412                          args: &[ast::Arg],
1413                          context: &RewriteContext)
1414                          -> Option<String> {
1415     match explicit_self.node {
1416         ast::SelfKind::Region(lt, m) => {
1417             let mut_str = format_mutability(m);
1418             match lt {
1419                 Some(ref l) => {
1420                     let lifetime_str = try_opt!(l.rewrite(context,
1421                                                           Shape::legacy(usize::max_value(),
1422                                                                         Indent::empty())));
1423                     Some(format!("&{} {}self", lifetime_str, mut_str))
1424                 }
1425                 None => Some(format!("&{}self", mut_str)),
1426             }
1427         }
1428         ast::SelfKind::Explicit(ref ty, _) => {
1429             assert!(!args.is_empty(), "&[ast::Arg] shouldn't be empty.");
1430
1431             let mutability = explicit_self_mutability(&args[0]);
1432             let type_str = try_opt!(ty.rewrite(context,
1433                                                Shape::legacy(usize::max_value(), Indent::empty())));
1434
1435             Some(format!("{}self: {}", format_mutability(mutability), type_str))
1436         }
1437         ast::SelfKind::Value(_) => {
1438             assert!(!args.is_empty(), "&[ast::Arg] shouldn't be empty.");
1439
1440             let mutability = explicit_self_mutability(&args[0]);
1441
1442             Some(format!("{}self", format_mutability(mutability)))
1443         }
1444     }
1445 }
1446
1447 // Hacky solution caused by absence of `Mutability` in `SelfValue` and
1448 // `SelfExplicit` variants of `ast::ExplicitSelf_`.
1449 fn explicit_self_mutability(arg: &ast::Arg) -> ast::Mutability {
1450     if let ast::PatKind::Ident(ast::BindingMode::ByValue(mutability), _, _) = arg.pat.node {
1451         mutability
1452     } else {
1453         unreachable!()
1454     }
1455 }
1456
1457 pub fn span_lo_for_arg(arg: &ast::Arg) -> BytePos {
1458     if is_named_arg(arg) {
1459         arg.pat.span.lo
1460     } else {
1461         arg.ty.span.lo
1462     }
1463 }
1464
1465 pub fn span_hi_for_arg(arg: &ast::Arg) -> BytePos {
1466     match arg.ty.node {
1467         ast::TyKind::Infer if is_named_arg(arg) => arg.pat.span.hi,
1468         _ => arg.ty.span.hi,
1469     }
1470 }
1471
1472 pub fn is_named_arg(arg: &ast::Arg) -> bool {
1473     if let ast::PatKind::Ident(_, ident, _) = arg.pat.node {
1474         ident.node != symbol::keywords::Invalid.ident()
1475     } else {
1476         true
1477     }
1478 }
1479
1480 fn span_for_return(ret: &ast::FunctionRetTy) -> Span {
1481     match *ret {
1482         ast::FunctionRetTy::Default(ref span) => span.clone(),
1483         ast::FunctionRetTy::Ty(ref ty) => ty.span,
1484     }
1485 }
1486
1487 fn span_for_ty_param(ty: &ast::TyParam) -> Span {
1488     // Note that ty.span is the span for ty.ident, not the whole item.
1489     let lo = ty.span.lo;
1490     if let Some(ref def) = ty.default {
1491         return mk_sp(lo, def.span.hi);
1492     }
1493     if ty.bounds.is_empty() {
1494         return ty.span;
1495     }
1496     let hi = match ty.bounds[ty.bounds.len() - 1] {
1497         ast::TyParamBound::TraitTyParamBound(ref ptr, _) => ptr.span.hi,
1498         ast::TyParamBound::RegionTyParamBound(ref l) => l.span.hi,
1499     };
1500     mk_sp(lo, hi)
1501 }
1502
1503 fn span_for_where_pred(pred: &ast::WherePredicate) -> Span {
1504     match *pred {
1505         ast::WherePredicate::BoundPredicate(ref p) => p.span,
1506         ast::WherePredicate::RegionPredicate(ref p) => p.span,
1507         ast::WherePredicate::EqPredicate(ref p) => p.span,
1508     }
1509 }
1510
1511 // Return type is (result, force_new_line_for_brace)
1512 fn rewrite_fn_base(context: &RewriteContext,
1513                    indent: Indent,
1514                    ident: ast::Ident,
1515                    fd: &ast::FnDecl,
1516                    generics: &ast::Generics,
1517                    unsafety: ast::Unsafety,
1518                    constness: ast::Constness,
1519                    defaultness: ast::Defaultness,
1520                    abi: abi::Abi,
1521                    vis: &ast::Visibility,
1522                    span: Span,
1523                    newline_brace: bool,
1524                    has_body: bool,
1525                    has_braces: bool)
1526                    -> Option<(String, bool)> {
1527     let mut force_new_line_for_brace = false;
1528
1529     let where_clause = &generics.where_clause;
1530
1531     let mut result = String::with_capacity(1024);
1532     // Vis unsafety abi.
1533     result.push_str(&*format_visibility(vis));
1534
1535     if let ast::Defaultness::Default = defaultness {
1536         result.push_str("default ");
1537     }
1538
1539     if let ast::Constness::Const = constness {
1540         result.push_str("const ");
1541     }
1542
1543     result.push_str(::utils::format_unsafety(unsafety));
1544
1545     if abi != abi::Abi::Rust {
1546         result.push_str(&::utils::format_abi(abi, context.config.force_explicit_abi()));
1547     }
1548
1549     // fn foo
1550     result.push_str("fn ");
1551     result.push_str(&ident.to_string());
1552
1553     // Generics.
1554     let generics_indent = indent + last_line_width(&result);
1555     let generics_span = mk_sp(span.lo, span_for_return(&fd.output).lo);
1556     let shape = Shape::indented(generics_indent, context.config);
1557     let generics_str = try_opt!(rewrite_generics(context, generics, shape, generics_span));
1558     result.push_str(&generics_str);
1559
1560     let snuggle_angle_bracket = last_line_width(&generics_str) == 1;
1561
1562     // Note that the width and indent don't really matter, we'll re-layout the
1563     // return type later anyway.
1564     let ret_str = try_opt!(fd.output
1565                                .rewrite(&context, Shape::indented(indent, context.config)));
1566
1567     let multi_line_ret_str = ret_str.contains('\n');
1568     let ret_str_len = if multi_line_ret_str { 0 } else { ret_str.len() };
1569
1570     // Args.
1571     let (mut one_line_budget, mut multi_line_budget, mut arg_indent) =
1572         try_opt!(compute_budgets_for_args(context, &result, indent, ret_str_len, newline_brace));
1573
1574     if context.config.fn_args_layout() == IndentStyle::Block {
1575         arg_indent = indent.block_indent(context.config);
1576         multi_line_budget = context.config.max_width() - arg_indent.width();
1577     }
1578
1579     debug!("rewrite_fn_base: one_line_budget: {}, multi_line_budget: {}, arg_indent: {:?}",
1580            one_line_budget,
1581            multi_line_budget,
1582            arg_indent);
1583
1584     // Check if vertical layout was forced.
1585     if one_line_budget == 0 {
1586         if snuggle_angle_bracket {
1587             result.push_str("(");
1588         } else if context.config.fn_args_paren_newline() {
1589             result.push('\n');
1590             result.push_str(&arg_indent.to_string(context.config));
1591             arg_indent = arg_indent + 1; // extra space for `(`
1592             result.push('(');
1593             if context.config.spaces_within_parens() && fd.inputs.len() > 0 {
1594                 result.push(' ')
1595             }
1596         } else {
1597             result.push_str("(\n");
1598             result.push_str(&arg_indent.to_string(context.config));
1599         }
1600     } else {
1601         result.push('(');
1602         if context.config.spaces_within_parens() && fd.inputs.len() > 0 {
1603             result.push(' ')
1604         }
1605     }
1606
1607     if multi_line_ret_str {
1608         one_line_budget = 0;
1609     }
1610
1611     // A conservative estimation, to goal is to be over all parens in generics
1612     let args_start = generics
1613         .ty_params
1614         .last()
1615         .map_or(span.lo, |tp| end_typaram(tp));
1616     let args_span = mk_sp(context.codemap.span_after(mk_sp(args_start, span.hi), "("),
1617                           span_for_return(&fd.output).lo);
1618     let arg_str = try_opt!(rewrite_args(context,
1619                                         &fd.inputs,
1620                                         fd.get_self().as_ref(),
1621                                         one_line_budget,
1622                                         multi_line_budget,
1623                                         indent,
1624                                         arg_indent,
1625                                         args_span,
1626                                         fd.variadic,
1627                                         generics_str.contains('\n')));
1628
1629     let multi_line_arg_str = arg_str.contains('\n');
1630
1631     let put_args_in_block = match context.config.fn_args_layout() {
1632         IndentStyle::Block => multi_line_arg_str || generics_str.contains('\n'),
1633         _ => false,
1634     } && !fd.inputs.is_empty();
1635
1636     if put_args_in_block {
1637         arg_indent = indent.block_indent(context.config);
1638         result.push('\n');
1639         result.push_str(&arg_indent.to_string(context.config));
1640         result.push_str(&arg_str);
1641         result.push('\n');
1642         result.push_str(&indent.to_string(context.config));
1643         result.push(')');
1644     } else {
1645         result.push_str(&arg_str);
1646         if context.config.spaces_within_parens() && fd.inputs.len() > 0 {
1647             result.push(' ')
1648         }
1649         result.push(')');
1650     }
1651
1652     // Return type.
1653     if !ret_str.is_empty() {
1654         let ret_should_indent = match context.config.fn_args_layout() {
1655             // If our args are block layout then we surely must have space.
1656             IndentStyle::Block if put_args_in_block => false,
1657             _ => {
1658                 // If we've already gone multi-line, or the return type would push over the max
1659                 // width, then put the return type on a new line. With the +1 for the signature
1660                 // length an additional space between the closing parenthesis of the argument and
1661                 // the arrow '->' is considered.
1662                 let mut sig_length = result.len() + indent.width() + ret_str_len + 1;
1663
1664                 // If there is no where clause, take into account the space after the return type
1665                 // and the brace.
1666                 if where_clause.predicates.is_empty() {
1667                     sig_length += 2;
1668                 }
1669
1670                 let overlong_sig = sig_length > context.config.max_width();
1671
1672                 result.contains('\n') || multi_line_ret_str || overlong_sig
1673             }
1674         };
1675         let ret_indent = if ret_should_indent {
1676             let indent = match context.config.fn_return_indent() {
1677                 ReturnIndent::WithWhereClause => indent + 4,
1678                 // Aligning with non-existent args looks silly.
1679                 _ if arg_str.is_empty() => {
1680                     force_new_line_for_brace = true;
1681                     indent + 4
1682                 }
1683                 // FIXME: we might want to check that using the arg indent
1684                 // doesn't blow our budget, and if it does, then fallback to
1685                 // the where clause indent.
1686                 _ => arg_indent,
1687             };
1688
1689             result.push('\n');
1690             result.push_str(&indent.to_string(context.config));
1691             indent
1692         } else {
1693             result.push(' ');
1694             Indent::new(indent.width(), result.len())
1695         };
1696
1697         if multi_line_ret_str || ret_should_indent {
1698             // Now that we know the proper indent and width, we need to
1699             // re-layout the return type.
1700             let ret_str = try_opt!(fd.output
1701                                        .rewrite(context,
1702                                                 Shape::indented(ret_indent, context.config)));
1703             result.push_str(&ret_str);
1704         } else {
1705             result.push_str(&ret_str);
1706         }
1707
1708         // Comment between return type and the end of the decl.
1709         let snippet_lo = fd.output.span().hi;
1710         if where_clause.predicates.is_empty() {
1711             let snippet_hi = span.hi;
1712             let snippet = context.snippet(mk_sp(snippet_lo, snippet_hi));
1713             let snippet = snippet.trim();
1714             if !snippet.is_empty() {
1715                 result.push(' ');
1716                 result.push_str(snippet);
1717             }
1718         } else {
1719             // FIXME it would be nice to catch comments between the return type
1720             // and the where clause, but we don't have a span for the where
1721             // clause.
1722         }
1723     }
1724
1725     let should_compress_where = match context.config.where_density() {
1726         Density::Compressed => !result.contains('\n') || put_args_in_block,
1727         Density::CompressedIfEmpty => !has_body && !result.contains('\n'),
1728         _ => false,
1729     } || (put_args_in_block && ret_str.is_empty());
1730
1731     if where_clause.predicates.len() == 1 && should_compress_where {
1732         let budget = try_opt!(context
1733                                   .config
1734                                   .max_width()
1735                                   .checked_sub(last_line_width(&result)));
1736         if let Some(where_clause_str) =
1737             rewrite_where_clause(context,
1738                                  where_clause,
1739                                  context.config.fn_brace_style(),
1740                                  Shape::legacy(budget, indent),
1741                                  Density::Compressed,
1742                                  "{",
1743                                  !has_braces,
1744                                  put_args_in_block && ret_str.is_empty(),
1745                                  Some(span.hi)) {
1746             if !where_clause_str.contains('\n') {
1747                 if last_line_width(&result) + where_clause_str.len() > context.config.max_width() {
1748                     result.push('\n');
1749                 }
1750
1751                 result.push_str(&where_clause_str);
1752
1753                 return Some((result, force_new_line_for_brace));
1754             }
1755         }
1756     }
1757
1758     let where_clause_str = try_opt!(rewrite_where_clause(context,
1759                                                          where_clause,
1760                                                          context.config.fn_brace_style(),
1761                                                          Shape::indented(indent, context.config),
1762                                                          Density::Tall,
1763                                                          "{",
1764                                                          !has_braces,
1765                                                          put_args_in_block && ret_str.is_empty(),
1766                                                          Some(span.hi)));
1767
1768     result.push_str(&where_clause_str);
1769
1770     Some((result, force_new_line_for_brace))
1771 }
1772
1773 fn rewrite_args(context: &RewriteContext,
1774                 args: &[ast::Arg],
1775                 explicit_self: Option<&ast::ExplicitSelf>,
1776                 one_line_budget: usize,
1777                 multi_line_budget: usize,
1778                 indent: Indent,
1779                 arg_indent: Indent,
1780                 span: Span,
1781                 variadic: bool,
1782                 generics_str_contains_newline: bool)
1783                 -> Option<String> {
1784     let mut arg_item_strs =
1785         try_opt!(args.iter()
1786                      .map(|arg| {
1787                               arg.rewrite(&context, Shape::legacy(multi_line_budget, arg_indent))
1788                           })
1789                      .collect::<Option<Vec<_>>>());
1790
1791     // Account for sugary self.
1792     // FIXME: the comment for the self argument is dropped. This is blocked
1793     // on rust issue #27522.
1794     let min_args = explicit_self
1795         .and_then(|explicit_self| rewrite_explicit_self(explicit_self, args, context))
1796         .map_or(1, |self_str| {
1797             arg_item_strs[0] = self_str;
1798             2
1799         });
1800
1801     // Comments between args.
1802     let mut arg_items = Vec::new();
1803     if min_args == 2 {
1804         arg_items.push(ListItem::from_str(""));
1805     }
1806
1807     // FIXME(#21): if there are no args, there might still be a comment, but
1808     // without spans for the comment or parens, there is no chance of
1809     // getting it right. You also don't get to put a comment on self, unless
1810     // it is explicit.
1811     if args.len() >= min_args || variadic {
1812         let comment_span_start = if min_args == 2 {
1813             let second_arg_start = if arg_has_pattern(&args[1]) {
1814                 args[1].pat.span.lo
1815             } else {
1816                 args[1].ty.span.lo
1817             };
1818             let reduced_span = mk_sp(span.lo, second_arg_start);
1819
1820             context.codemap.span_after_last(reduced_span, ",")
1821         } else {
1822             span.lo
1823         };
1824
1825         enum ArgumentKind<'a> {
1826             Regular(&'a ast::Arg),
1827             Variadic(BytePos),
1828         }
1829
1830         let variadic_arg = if variadic {
1831             let variadic_span = mk_sp(args.last().unwrap().ty.span.hi, span.hi);
1832             let variadic_start = context.codemap.span_after(variadic_span, "...") - BytePos(3);
1833             Some(ArgumentKind::Variadic(variadic_start))
1834         } else {
1835             None
1836         };
1837
1838         let more_items = itemize_list(context.codemap,
1839                                       args[min_args - 1..]
1840                                           .iter()
1841                                           .map(ArgumentKind::Regular)
1842                                           .chain(variadic_arg),
1843                                       ")",
1844                                       |arg| match *arg {
1845                                           ArgumentKind::Regular(arg) => span_lo_for_arg(arg),
1846                                           ArgumentKind::Variadic(start) => start,
1847                                       },
1848                                       |arg| match *arg {
1849                                           ArgumentKind::Regular(arg) => arg.ty.span.hi,
1850                                           ArgumentKind::Variadic(start) => start + BytePos(3),
1851                                       },
1852                                       |arg| match *arg {
1853                                           ArgumentKind::Regular(..) => None,
1854                                           ArgumentKind::Variadic(..) => Some("...".to_owned()),
1855                                       },
1856                                       comment_span_start,
1857                                       span.hi);
1858
1859         arg_items.extend(more_items);
1860     }
1861
1862     for (item, arg) in arg_items.iter_mut().zip(arg_item_strs) {
1863         item.item = Some(arg);
1864     }
1865
1866     let (indent, trailing_comma, end_with_newline) = match context.config.fn_args_layout() {
1867         IndentStyle::Block if !generics_str_contains_newline && arg_items.len() <= 1 => {
1868             (indent.block_indent(context.config), SeparatorTactic::Never, true)
1869         }
1870         IndentStyle::Block => {
1871             (indent.block_indent(context.config), SeparatorTactic::Vertical, true)
1872         }
1873         IndentStyle::Visual => (arg_indent, SeparatorTactic::Never, false),
1874     };
1875
1876     let tactic = definitive_tactic(&arg_items,
1877                                    context.config.fn_args_density().to_list_tactic(),
1878                                    one_line_budget);
1879     let budget = match tactic {
1880         DefinitiveListTactic::Horizontal => one_line_budget,
1881         _ => multi_line_budget,
1882     };
1883
1884     debug!("rewrite_args: budget: {}, tactic: {:?}", budget, tactic);
1885
1886     let fmt = ListFormatting {
1887         tactic: tactic,
1888         separator: ",",
1889         trailing_separator: trailing_comma,
1890         shape: Shape::legacy(budget, indent),
1891         ends_with_newline: end_with_newline,
1892         config: context.config,
1893     };
1894
1895     write_list(&arg_items, &fmt)
1896 }
1897
1898 fn arg_has_pattern(arg: &ast::Arg) -> bool {
1899     if let ast::PatKind::Ident(_, ident, _) = arg.pat.node {
1900         ident.node != symbol::keywords::Invalid.ident()
1901     } else {
1902         true
1903     }
1904 }
1905
1906 fn compute_budgets_for_args(context: &RewriteContext,
1907                             result: &str,
1908                             indent: Indent,
1909                             ret_str_len: usize,
1910                             newline_brace: bool)
1911                             -> Option<((usize, usize, Indent))> {
1912     debug!("compute_budgets_for_args {} {:?}, {}, {}",
1913            result.len(),
1914            indent,
1915            ret_str_len,
1916            newline_brace);
1917     // Try keeping everything on the same line.
1918     if !result.contains('\n') {
1919         // 3 = `() `, space is before ret_string.
1920         let mut used_space = indent.width() + result.len() + ret_str_len + 3;
1921         if !newline_brace {
1922             used_space += 2;
1923         }
1924         let one_line_budget = context
1925             .config
1926             .max_width()
1927             .checked_sub(used_space)
1928             .unwrap_or(0);
1929
1930         if one_line_budget > 0 {
1931             // 4 = "() {".len()
1932             let multi_line_budget = try_opt!(context
1933                                                  .config
1934                                                  .max_width()
1935                                                  .checked_sub(indent.width() + result.len() +
1936                                                               4));
1937
1938             return Some((one_line_budget, multi_line_budget, indent + result.len() + 1));
1939         }
1940     }
1941
1942     // Didn't work. we must force vertical layout and put args on a newline.
1943     let new_indent = indent.block_indent(context.config);
1944     let used_space = new_indent.width() + 4; // Account for `(` and `)` and possibly ` {`.
1945     let max_space = context.config.max_width();
1946     if used_space <= max_space {
1947         Some((0, max_space - used_space, new_indent))
1948     } else {
1949         // Whoops! bankrupt.
1950         None
1951     }
1952 }
1953
1954 fn newline_for_brace(config: &Config, where_clause: &ast::WhereClause) -> bool {
1955     match config.fn_brace_style() {
1956         BraceStyle::AlwaysNextLine => true,
1957         BraceStyle::SameLineWhere if !where_clause.predicates.is_empty() => true,
1958         _ => false,
1959     }
1960 }
1961
1962 fn rewrite_generics(context: &RewriteContext,
1963                     generics: &ast::Generics,
1964                     shape: Shape,
1965                     span: Span)
1966                     -> Option<String> {
1967     // FIXME: convert bounds to where clauses where they get too big or if
1968     // there is a where clause at all.
1969     let lifetimes: &[_] = &generics.lifetimes;
1970     let tys: &[_] = &generics.ty_params;
1971     if lifetimes.is_empty() && tys.is_empty() {
1972         return Some(String::new());
1973     }
1974
1975     let offset = match context.config.generics_indent() {
1976         IndentStyle::Block => shape.indent.block_only().block_indent(context.config),
1977         // 1 = <
1978         IndentStyle::Visual => shape.indent + 1,
1979     };
1980
1981     let h_budget = try_opt!(shape.width.checked_sub(2));
1982     // FIXME: might need to insert a newline if the generics are really long.
1983
1984     // Strings for the generics.
1985     let lt_strs = lifetimes
1986         .iter()
1987         .map(|lt| lt.rewrite(context, Shape::legacy(h_budget, offset)));
1988     let ty_strs = tys.iter()
1989         .map(|ty_param| ty_param.rewrite(context, Shape::legacy(h_budget, offset)));
1990
1991     // Extract comments between generics.
1992     let lt_spans = lifetimes
1993         .iter()
1994         .map(|l| {
1995                  let hi = if l.bounds.is_empty() {
1996                      l.lifetime.span.hi
1997                  } else {
1998                      l.bounds[l.bounds.len() - 1].span.hi
1999                  };
2000                  mk_sp(l.lifetime.span.lo, hi)
2001              });
2002     let ty_spans = tys.iter().map(span_for_ty_param);
2003
2004     let items = itemize_list(context.codemap,
2005                              lt_spans.chain(ty_spans).zip(lt_strs.chain(ty_strs)),
2006                              ">",
2007                              |&(sp, _)| sp.lo,
2008                              |&(sp, _)| sp.hi,
2009                              // FIXME: don't clone
2010                              |&(_, ref str)| str.clone(),
2011                              context.codemap.span_after(span, "<"),
2012                              span.hi);
2013     let list_str =
2014         try_opt!(format_item_list(items, Shape::legacy(h_budget, offset), context.config));
2015
2016     let result = if context.config.generics_indent() != IndentStyle::Visual &&
2017                     list_str.contains('\n') {
2018         format!("<\n{}{}\n{}>",
2019                 offset.to_string(context.config),
2020                 list_str,
2021                 shape.indent.block_only().to_string(context.config))
2022     } else if context.config.spaces_within_angle_brackets() {
2023         format!("< {} >", list_str)
2024     } else {
2025         format!("<{}>", list_str)
2026     };
2027     Some(result)
2028 }
2029
2030 fn rewrite_trait_bounds(context: &RewriteContext,
2031                         type_param_bounds: &ast::TyParamBounds,
2032                         shape: Shape)
2033                         -> Option<String> {
2034     let bounds: &[_] = type_param_bounds;
2035
2036     if bounds.is_empty() {
2037         return Some(String::new());
2038     }
2039     let joiner = match context.config.type_punctuation_density() {
2040         TypeDensity::Compressed => "+",
2041         TypeDensity::Wide => " + ",
2042     };
2043     let bound_str = try_opt!(bounds
2044                                  .iter()
2045                                  .map(|ty_bound| ty_bound.rewrite(&context, shape))
2046                                  .intersperse(Some(joiner.to_string()))
2047                                  .collect::<Option<String>>());
2048
2049     let mut result = String::new();
2050     result.push_str(": ");
2051     result.push_str(&bound_str);
2052     Some(result)
2053 }
2054
2055 //   fn reflow_list_node_with_rule(
2056 //        &self,
2057 //        node: &CompoundNode,
2058 //        rule: &Rule,
2059 //        args: &[Arg],
2060 //        shape: &Shape
2061 //    ) -> Result<String, ()>
2062 //    where
2063 //        T: Foo,
2064 //    {
2065
2066
2067 fn rewrite_where_clause_rfc_style(context: &RewriteContext,
2068                                   where_clause: &ast::WhereClause,
2069                                   shape: Shape,
2070                                   terminator: &str,
2071                                   suppress_comma: bool,
2072                                   // where clause can be kept on the current line.
2073                                   snuggle: bool,
2074                                   span_end: Option<BytePos>)
2075                                   -> Option<String> {
2076     let block_shape = shape.block();
2077
2078     let starting_newline = if snuggle {
2079         " ".to_owned()
2080     } else {
2081         "\n".to_owned() + &block_shape.indent.to_string(context.config)
2082     };
2083
2084     let clause_shape = block_shape.block_indent(context.config.tab_spaces());
2085     // each clause on one line, trailing comma (except if suppress_comma)
2086     let span_start = span_for_where_pred(&where_clause.predicates[0]).lo;
2087     // If we don't have the start of the next span, then use the end of the
2088     // predicates, but that means we miss comments.
2089     let len = where_clause.predicates.len();
2090     let end_of_preds = span_for_where_pred(&where_clause.predicates[len - 1]).hi;
2091     let span_end = span_end.unwrap_or(end_of_preds);
2092     let items = itemize_list(context.codemap,
2093                              where_clause.predicates.iter(),
2094                              terminator,
2095                              |pred| span_for_where_pred(pred).lo,
2096                              |pred| span_for_where_pred(pred).hi,
2097                              |pred| pred.rewrite(context, clause_shape),
2098                              span_start,
2099                              span_end);
2100     let comma_tactic = if suppress_comma {
2101         SeparatorTactic::Never
2102     } else {
2103         SeparatorTactic::Always
2104     };
2105
2106     let fmt = ListFormatting {
2107         tactic: DefinitiveListTactic::Vertical,
2108         separator: ",",
2109         trailing_separator: comma_tactic,
2110         shape: clause_shape,
2111         ends_with_newline: true,
2112         config: context.config,
2113     };
2114     let preds_str = try_opt!(write_list(items, &fmt));
2115
2116     Some(format!("{}where\n{}{}",
2117                  starting_newline,
2118                  clause_shape.indent.to_string(context.config),
2119                  preds_str))
2120 }
2121
2122 fn rewrite_where_clause(context: &RewriteContext,
2123                         where_clause: &ast::WhereClause,
2124                         brace_style: BraceStyle,
2125                         shape: Shape,
2126                         density: Density,
2127                         terminator: &str,
2128                         suppress_comma: bool,
2129                         snuggle: bool,
2130                         span_end: Option<BytePos>)
2131                         -> Option<String> {
2132     if where_clause.predicates.is_empty() {
2133         return Some(String::new());
2134     }
2135
2136     if context.config.where_style() == Style::Rfc {
2137         return rewrite_where_clause_rfc_style(context,
2138                                               where_clause,
2139                                               shape,
2140                                               terminator,
2141                                               suppress_comma,
2142                                               snuggle,
2143                                               span_end);
2144     }
2145
2146     let extra_indent = Indent::new(context.config.tab_spaces(), 0);
2147
2148     let offset = match context.config.where_pred_indent() {
2149         IndentStyle::Block => shape.indent + extra_indent.block_indent(context.config),
2150         // 6 = "where ".len()
2151         IndentStyle::Visual => shape.indent + extra_indent + 6,
2152     };
2153     // FIXME: if where_pred_indent != Visual, then the budgets below might
2154     // be out by a char or two.
2155
2156     let budget = context.config.max_width() - offset.width();
2157     let span_start = span_for_where_pred(&where_clause.predicates[0]).lo;
2158     // If we don't have the start of the next span, then use the end of the
2159     // predicates, but that means we miss comments.
2160     let len = where_clause.predicates.len();
2161     let end_of_preds = span_for_where_pred(&where_clause.predicates[len - 1]).hi;
2162     let span_end = span_end.unwrap_or(end_of_preds);
2163     let items = itemize_list(context.codemap,
2164                              where_clause.predicates.iter(),
2165                              terminator,
2166                              |pred| span_for_where_pred(pred).lo,
2167                              |pred| span_for_where_pred(pred).hi,
2168                              |pred| pred.rewrite(context, Shape::legacy(budget, offset)),
2169                              span_start,
2170                              span_end);
2171     let item_vec = items.collect::<Vec<_>>();
2172     // FIXME: we don't need to collect here if the where_layout isn't
2173     // HorizontalVertical.
2174     let tactic = definitive_tactic(&item_vec, context.config.where_layout(), budget);
2175
2176     let mut comma_tactic = context.config.trailing_comma();
2177     // Kind of a hack because we don't usually have trailing commas in where clauses.
2178     if comma_tactic == SeparatorTactic::Vertical || suppress_comma {
2179         comma_tactic = SeparatorTactic::Never;
2180     }
2181
2182     let fmt = ListFormatting {
2183         tactic: tactic,
2184         separator: ",",
2185         trailing_separator: comma_tactic,
2186         shape: Shape::legacy(budget, offset),
2187         ends_with_newline: true,
2188         config: context.config,
2189     };
2190     let preds_str = try_opt!(write_list(&item_vec, &fmt));
2191
2192     let end_length = if terminator == "{" {
2193         // If the brace is on the next line we don't need to count it otherwise it needs two
2194         // characters " {"
2195         match brace_style {
2196             BraceStyle::AlwaysNextLine |
2197             BraceStyle::SameLineWhere => 0,
2198             BraceStyle::PreferSameLine => 2,
2199         }
2200     } else if terminator == "=" {
2201         2
2202     } else {
2203         terminator.len()
2204     };
2205     if density == Density::Tall || preds_str.contains('\n') ||
2206        shape.indent.width() + " where ".len() + preds_str.len() + end_length > shape.width {
2207         Some(format!("\n{}where {}",
2208                      (shape.indent + extra_indent).to_string(context.config),
2209                      preds_str))
2210     } else {
2211         Some(format!(" where {}", preds_str))
2212     }
2213 }
2214
2215 fn format_header(item_name: &str, ident: ast::Ident, vis: &ast::Visibility) -> String {
2216     format!("{}{}{}", format_visibility(vis), item_name, ident)
2217 }
2218
2219 fn format_generics(context: &RewriteContext,
2220                    generics: &ast::Generics,
2221                    opener: &str,
2222                    terminator: &str,
2223                    brace_style: BraceStyle,
2224                    force_same_line_brace: bool,
2225                    offset: Indent,
2226                    span: Span)
2227                    -> Option<String> {
2228     let shape = Shape::indented(offset, context.config);
2229     let mut result = try_opt!(rewrite_generics(context, generics, shape, span));
2230
2231     if !generics.where_clause.predicates.is_empty() || result.contains('\n') {
2232         let budget = try_opt!(context
2233                                   .config
2234                                   .max_width()
2235                                   .checked_sub(last_line_width(&result)));
2236         let where_clause_str =
2237             try_opt!(rewrite_where_clause(context,
2238                                           &generics.where_clause,
2239                                           brace_style,
2240                                           Shape::legacy(budget, offset.block_only()),
2241                                           Density::Tall,
2242                                           terminator,
2243                                           false,
2244                                           trimmed_last_line_width(&result) == 1,
2245                                           Some(span.hi)));
2246         result.push_str(&where_clause_str);
2247         let same_line_brace = force_same_line_brace ||
2248                               (generics.where_clause.predicates.is_empty() &&
2249                                trimmed_last_line_width(&result) == 1);
2250         if !same_line_brace &&
2251            (brace_style == BraceStyle::SameLineWhere || brace_style == BraceStyle::AlwaysNextLine) {
2252             result.push('\n');
2253             result.push_str(&offset.block_only().to_string(context.config));
2254         } else {
2255             result.push(' ');
2256         }
2257         result.push_str(opener);
2258     } else {
2259         if force_same_line_brace || trimmed_last_line_width(&result) == 1 ||
2260            brace_style != BraceStyle::AlwaysNextLine {
2261             result.push(' ');
2262         } else {
2263             result.push('\n');
2264             result.push_str(&offset.block_only().to_string(context.config));
2265         }
2266         result.push_str(opener);
2267     }
2268
2269     Some(result)
2270 }