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
  26 use syntax::{ast, abi, codemap, ptr, symbol};
  27 use syntax::codemap::{Span, BytePos, mk_sp};
  28 use syntax::ast::ImplItem;
  29
  30 // Statements of the form
  31 // let pat: ty = init;
  32 impl Rewrite for ast::Local {
  33     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
  34         debug!("Local::rewrite {:?} {} {:?}",
  35                self,
  36                shape.width,
  37                shape.indent);
  38         let mut result = "let ".to_owned();
  39
  40         // 4 = "let ".len()
  41         let pat_shape = try_opt!(shape.offset_left(4));
  42         // 1 = ;
  43         let pat_shape = try_opt!(pat_shape.sub_width(1));
  44         let pat_str = try_opt!(self.pat.rewrite(&context, pat_shape));
  45         result.push_str(&pat_str);
  46
  47         // String that is placed within the assignment pattern and expression.
  48         let infix = {
  49             let mut infix = String::new();
  50
  51             if let Some(ref ty) = self.ty {
  52                 let separator = type_annotation_separator(context.config);
  53                 let indent = shape.indent + last_line_width(&result) + separator.len();
  54                 // 1 = ;
  55                 let budget = try_opt!(shape.width.checked_sub(indent.width() + 1));
  56                 let rewrite = try_opt!(ty.rewrite(context, Shape::legacy(budget, indent)));
  57
  58                 infix.push_str(separator);
  59                 infix.push_str(&rewrite);
  60             }
  61
  62             if self.init.is_some() {
  63                 infix.push_str(" =");
  64             }
  65
  66             infix
  67         };
  68
  69         result.push_str(&infix);
  70
  71         if let Some(ref ex) = self.init {
  72             // 1 = trailing semicolon;
  73             let nested_shape = try_opt!(shape.sub_width(1));
  74
  75             result = try_opt!(rewrite_assign_rhs(&context, result, ex, nested_shape));
  76         }
  77
  78         result.push(';');
  79         Some(result)
  80     }
  81 }
  82
  83 // TODO convert to using rewrite style rather than visitor
  84 // TODO format modules in this style
  85 #[allow(dead_code)]
  86 struct Item<'a> {
  87     keyword: &'static str,
  88     abi: String,
  89     vis: Option<&'a ast::Visibility>,
  90     body: Vec<BodyElement<'a>>,
  91     span: Span,
  92 }
  93
  94 impl<'a> Item<'a> {
  95     fn from_foreign_mod(fm: &'a ast::ForeignMod, span: Span, config: &Config) -> Item<'a> {
  96         let abi = if fm.abi == abi::Abi::C && !config.force_explicit_abi() {
  97             "extern".into()
  98         } else {
  99             format!("extern {}", fm.abi)
 100         };
 101         Item {
 102             keyword: "",
 103             abi: abi,
 104             vis: None,
 105             body: fm.items
 106                 .iter()
 107                 .map(|i| BodyElement::ForeignItem(i))
 108                 .collect(),
 109             span: span,
 110         }
 111     }
 112 }
 113
 114 enum BodyElement<'a> {
 115     // Stmt(&'a ast::Stmt),
 116     // Field(&'a ast::Field),
 117     // Variant(&'a ast::Variant),
 118     // Item(&'a ast::Item),
 119     ForeignItem(&'a ast::ForeignItem),
 120 }
 121
 122 impl<'a> FmtVisitor<'a> {
 123     fn format_item(&mut self, item: Item) {
 124         self.buffer.push_str(&item.abi);
 125         self.buffer.push_str(" ");
 126
 127         let snippet = self.snippet(item.span);
 128         let brace_pos = snippet.find_uncommented("{").unwrap();
 129
 130         self.buffer.push_str("{");
 131         if !item.body.is_empty() || contains_comment(&snippet[brace_pos..]) {
 132             // FIXME: this skips comments between the extern keyword and the opening
 133             // brace.
 134             self.last_pos = item.span.lo + BytePos(brace_pos as u32 + 1);
 135             self.block_indent = self.block_indent.block_indent(self.config);
 136
 137             if item.body.is_empty() {
 138                 self.format_missing_no_indent(item.span.hi - BytePos(1));
 139                 self.block_indent = self.block_indent.block_unindent(self.config);
 140
 141                 self.buffer
 142                     .push_str(&self.block_indent.to_string(self.config));
 143             } else {
 144                 for item in &item.body {
 145                     self.format_body_element(item);
 146                 }
 147
 148                 self.block_indent = self.block_indent.block_unindent(self.config);
 149                 self.format_missing_with_indent(item.span.hi - BytePos(1));
 150             }
 151         }
 152
 153         self.buffer.push_str("}");
 154         self.last_pos = item.span.hi;
 155     }
 156
 157     fn format_body_element(&mut self, element: &BodyElement) {
 158         match *element {
 159             BodyElement::ForeignItem(ref item) => self.format_foreign_item(item),
 160         }
 161     }
 162
 163     pub fn format_foreign_mod(&mut self, fm: &ast::ForeignMod, span: Span) {
 164         let item = Item::from_foreign_mod(fm, span, self.config);
 165         self.format_item(item);
 166     }
 167
 168     fn format_foreign_item(&mut self, item: &ast::ForeignItem) {
 169         self.format_missing_with_indent(item.span.lo);
 170         // Drop semicolon or it will be interpreted as comment.
 171         // FIXME: this may be a faulty span from libsyntax.
 172         let span = mk_sp(item.span.lo, item.span.hi - BytePos(1));
 173
 174         match item.node {
 175             ast::ForeignItemKind::Fn(ref fn_decl, ref generics) => {
 176                 let indent = self.block_indent;
 177                 let rewrite = rewrite_fn_base(&self.get_context(),
 178                                               indent,
 179                                               item.ident,
 180                                               fn_decl,
 181                                               generics,
 182                                               ast::Unsafety::Normal,
 183                                               ast::Constness::NotConst,
 184                                               ast::Defaultness::Final,
 185                                               // These are not actually rust functions,
 186                                               // but we format them as such.
 187                                               abi::Abi::Rust,
 188                                               &item.vis,
 189                                               span,
 190                                               false,
 191                                               false,
 192                                               false);
 193
 194                 match rewrite {
 195                     Some((new_fn, _)) => {
 196                         self.buffer.push_str(&new_fn);
 197                         self.buffer.push_str(";");
 198                     }
 199                     None => self.format_missing(item.span.hi),
 200                 }
 201             }
 202             ast::ForeignItemKind::Static(ref ty, is_mutable) => {
 203                 // FIXME(#21): we're dropping potential comments in between the
 204                 // function keywords here.
 205                 let vis = format_visibility(&item.vis);
 206                 let mut_str = if is_mutable { "mut " } else { "" };
 207                 let prefix = format!("{}static {}{}: ", vis, mut_str, item.ident);
 208                 let offset = self.block_indent + prefix.len();
 209                 // 1 = ;
 210                 let shape = Shape::indented(offset, self.config).sub_width(1).unwrap();
 211                 let rewrite = ty.rewrite(&self.get_context(), shape);
 212
 213                 match rewrite {
 214                     Some(result) => {
 215                         self.buffer.push_str(&prefix);
 216                         self.buffer.push_str(&result);
 217                         self.buffer.push_str(";");
 218                     }
 219                     None => self.format_missing(item.span.hi),
 220                 }
 221             }
 222         }
 223
 224         self.last_pos = item.span.hi;
 225     }
 226
 227     pub fn rewrite_fn(&mut self,
 228                       indent: Indent,
 229                       ident: ast::Ident,
 230                       fd: &ast::FnDecl,
 231                       generics: &ast::Generics,
 232                       unsafety: ast::Unsafety,
 233                       constness: ast::Constness,
 234                       defaultness: ast::Defaultness,
 235                       abi: abi::Abi,
 236                       vis: &ast::Visibility,
 237                       span: Span,
 238                       block: &ast::Block)
 239                       -> Option<String> {
 240         let mut newline_brace = newline_for_brace(self.config, &generics.where_clause);
 241         let context = self.get_context();
 242
 243         let block_snippet = self.snippet(codemap::mk_sp(block.span.lo, block.span.hi));
 244         let has_body = !block_snippet[1..block_snippet.len() - 1].trim().is_empty() ||
 245                        !context.config.fn_empty_single_line();
 246
 247         let (mut result, force_newline_brace) = try_opt!(rewrite_fn_base(&context,
 248                                                                          indent,
 249                                                                          ident,
 250                                                                          fd,
 251                                                                          generics,
 252                                                                          unsafety,
 253                                                                          constness,
 254                                                                          defaultness,
 255                                                                          abi,
 256                                                                          vis,
 257                                                                          span,
 258                                                                          newline_brace,
 259                                                                          has_body,
 260                                                                          true));
 261
 262         if self.config.fn_brace_style() != BraceStyle::AlwaysNextLine && !result.contains('\n') {
 263             newline_brace = false;
 264         } else if force_newline_brace {
 265             newline_brace = true;
 266         }
 267
 268         // Prepare for the function body by possibly adding a newline and
 269         // indent.
 270         // FIXME we'll miss anything between the end of the signature and the
 271         // start of the body, but we need more spans from the compiler to solve
 272         // this.
 273         if newline_brace {
 274             result.push('\n');
 275             result.push_str(&indent.to_string(self.config));
 276         } else {
 277             result.push(' ');
 278         }
 279
 280         self.single_line_fn(&result, block).or_else(|| Some(result))
 281     }
 282
 283     pub fn rewrite_required_fn(&mut self,
 284                                indent: Indent,
 285                                ident: ast::Ident,
 286                                sig: &ast::MethodSig,
 287                                span: Span)
 288                                -> Option<String> {
 289         // Drop semicolon or it will be interpreted as comment.
 290         let span = mk_sp(span.lo, span.hi - BytePos(1));
 291         let context = self.get_context();
 292
 293         let (mut result, _) = try_opt!(rewrite_fn_base(&context,
 294                                                        indent,
 295                                                        ident,
 296                                                        &sig.decl,
 297                                                        &sig.generics,
 298                                                        sig.unsafety,
 299                                                        sig.constness.node,
 300                                                        ast::Defaultness::Final,
 301                                                        sig.abi,
 302                                                        &ast::Visibility::Inherited,
 303                                                        span,
 304                                                        false,
 305                                                        false,
 306                                                        false));
 307
 308         // Re-attach semicolon
 309         result.push(';');
 310
 311         Some(result)
 312     }
 313
 314     fn single_line_fn(&self, fn_str: &str, block: &ast::Block) -> Option<String> {
 315         if fn_str.contains('\n') {
 316             return None;
 317         }
 318
 319         let codemap = self.get_context().codemap;
 320
 321         if self.config.fn_empty_single_line() && is_empty_block(block, codemap) &&
 322            self.block_indent.width() + fn_str.len() + 2 <= self.config.max_width() {
 323             return Some(format!("{}{{}}", fn_str));
 324         }
 325
 326         if self.config.fn_single_line() && is_simple_block_stmt(block, codemap) {
 327             let rewrite = {
 328                 if let Some(ref stmt) = block.stmts.first() {
 329                     match stmt_expr(stmt) {
 330                         Some(e) => {
 331                             let suffix = if semicolon_for_expr(e) { ";" } else { "" };
 332
 333                             e.rewrite(&self.get_context(),
 334                                       Shape::indented(self.block_indent, self.config))
 335                                 .map(|s| s + suffix)
 336                                 .or_else(|| Some(self.snippet(e.span)))
 337                         }
 338                         None => {
 339                             stmt.rewrite(&self.get_context(),
 340                                          Shape::indented(self.block_indent, self.config))
 341                         }
 342                     }
 343                 } else {
 344                     None
 345                 }
 346             };
 347
 348             if let Some(res) = rewrite {
 349                 let width = self.block_indent.width() + fn_str.len() + res.len() + 4;
 350                 if !res.contains('\n') && width <= self.config.max_width() {
 351                     return Some(format!("{}{{ {} }}", fn_str, res));
 352                 }
 353             }
 354         }
 355
 356         None
 357     }
 358
 359     pub fn visit_enum(&mut self,
 360                       ident: ast::Ident,
 361                       vis: &ast::Visibility,
 362                       enum_def: &ast::EnumDef,
 363                       generics: &ast::Generics,
 364                       span: Span) {
 365         self.buffer.push_str(&format_header("enum ", ident, vis));
 366
 367         let enum_snippet = self.snippet(span);
 368         let brace_pos = enum_snippet.find_uncommented("{").unwrap();
 369         let body_start = span.lo + BytePos(brace_pos as u32 + 1);
 370         let generics_str = format_generics(&self.get_context(),
 371                                            generics,
 372                                            "{",
 373                                            "{",
 374                                            self.config.item_brace_style(),
 375                                            enum_def.variants.is_empty(),
 376                                            self.block_indent,
 377                                            mk_sp(span.lo, body_start))
 378             .unwrap();
 379         self.buffer.push_str(&generics_str);
 380
 381         self.last_pos = body_start;
 382
 383         self.block_indent = self.block_indent.block_indent(self.config);
 384         let variant_list = self.format_variant_list(enum_def, body_start, span.hi - BytePos(1));
 385         match variant_list {
 386             Some(ref body_str) => self.buffer.push_str(body_str),
 387             None => {
 388                 if contains_comment(&enum_snippet[brace_pos..]) {
 389                     self.format_missing_no_indent(span.hi - BytePos(1))
 390                 } else {
 391                     self.format_missing(span.hi - BytePos(1))
 392                 }
 393             }
 394         }
 395         self.block_indent = self.block_indent.block_unindent(self.config);
 396
 397         if variant_list.is_some() || contains_comment(&enum_snippet[brace_pos..]) {
 398             self.buffer
 399                 .push_str(&self.block_indent.to_string(self.config));
 400         }
 401         self.buffer.push_str("}");
 402         self.last_pos = span.hi;
 403     }
 404
 405     // Format the body of an enum definition
 406     fn format_variant_list(&self,
 407                            enum_def: &ast::EnumDef,
 408                            body_lo: BytePos,
 409                            body_hi: BytePos)
 410                            -> Option<String> {
 411         if enum_def.variants.is_empty() {
 412             return None;
 413         }
 414         let mut result = String::with_capacity(1024);
 415         result.push('\n');
 416         let indentation = self.block_indent.to_string(self.config);
 417         result.push_str(&indentation);
 418
 419         let items = itemize_list(self.codemap,
 420                                  enum_def.variants.iter(),
 421                                  "}",
 422                                  |f| if !f.node.attrs.is_empty() {
 423                                      f.node.attrs[0].span.lo
 424                                  } else {
 425                                      f.span.lo
 426                                  },
 427                                  |f| f.span.hi,
 428                                  |f| self.format_variant(f),
 429                                  body_lo,
 430                                  body_hi);
 431
 432         let shape = Shape::indented(self.block_indent, self.config)
 433             .sub_width(2)
 434             .unwrap();
 435         let fmt = ListFormatting {
 436             tactic: DefinitiveListTactic::Vertical,
 437             separator: ",",
 438             trailing_separator: self.config.trailing_comma(),
 439             shape: shape,
 440             ends_with_newline: true,
 441             config: self.config,
 442         };
 443
 444         let list = try_opt!(write_list(items, &fmt));
 445         result.push_str(&list);
 446         result.push('\n');
 447         Some(result)
 448     }
 449
 450     // Variant of an enum.
 451     fn format_variant(&self, field: &ast::Variant) -> Option<String> {
 452         if contains_skip(&field.node.attrs) {
 453             let lo = field.node.attrs[0].span.lo;
 454             let span = mk_sp(lo, field.span.hi);
 455             return Some(self.snippet(span));
 456         }
 457
 458         let indent = self.block_indent;
 459         let mut result = try_opt!(field.node.attrs.rewrite(&self.get_context(),
 460                                                            Shape::indented(indent, self.config)));
 461         if !result.is_empty() {
 462             result.push('\n');
 463             result.push_str(&indent.to_string(self.config));
 464         }
 465
 466         let context = self.get_context();
 467         let variant_body = match field.node.data {
 468             ast::VariantData::Tuple(..) |
 469             ast::VariantData::Struct(..) => {
 470                 // FIXME: Should limit the width, as we have a trailing comma
 471                 format_struct(&context,
 472                               "",
 473                               field.node.name,
 474                               &ast::Visibility::Inherited,
 475                               &field.node.data,
 476                               None,
 477                               field.span,
 478                               indent,
 479                               Some(self.config.struct_variant_width()))
 480             }
 481             ast::VariantData::Unit(..) => {
 482                 let tag = if let Some(ref expr) = field.node.disr_expr {
 483                     format!("{} = {}", field.node.name, self.snippet(expr.span))
 484                 } else {
 485                     field.node.name.to_string()
 486                 };
 487
 488                 wrap_str(tag,
 489                          self.config.max_width(),
 490                          Shape::indented(indent, self.config))
 491             }
 492         };
 493
 494         if let Some(variant_str) = variant_body {
 495             result.push_str(&variant_str);
 496             Some(result)
 497         } else {
 498             None
 499         }
 500     }
 501 }
 502
 503 pub fn format_impl(context: &RewriteContext, item: &ast::Item, offset: Indent) -> Option<String> {
 504     if let ast::ItemKind::Impl(_, _, ref generics, ref trait_ref, _, ref items) = item.node {
 505         let mut result = String::new();
 506         // First try to format the ref and type without a split at the 'for'.
 507         let mut ref_and_type = try_opt!(format_impl_ref_and_type(context, item, offset, false));
 508
 509         // If there is a line break present in the first result format it again
 510         // with a split at the 'for'. Skip this if there is no trait ref and
 511         // therefore no 'for'.
 512         if ref_and_type.contains('\n') && trait_ref.is_some() {
 513             ref_and_type = try_opt!(format_impl_ref_and_type(context, item, offset, true));
 514         }
 515         result.push_str(&ref_and_type);
 516
 517         let where_budget = try_opt!(context
 518                                         .config
 519                                         .max_width()
 520                                         .checked_sub(last_line_width(&result)));
 521         let where_clause_str = try_opt!(rewrite_where_clause(context,
 522                                                              &generics.where_clause,
 523                                                              context.config.item_brace_style(),
 524                                                              Shape::legacy(where_budget,
 525                                                                            offset.block_only()),
 526                                                              context.config.where_density(),
 527                                                              "{",
 528                                                              false,
 529                                                              last_line_width(&ref_and_type) == 1,
 530                                                              None));
 531
 532         if try_opt!(is_impl_single_line(context, &items, &result, &where_clause_str, &item)) {
 533             result.push_str(&where_clause_str);
 534             if where_clause_str.contains('\n') {
 535                 let white_space = offset.to_string(context.config);
 536                 result.push_str(&format!("\n{}{{\n{}}}", &white_space, &white_space));
 537             } else {
 538                 result.push_str(" {}");
 539             }
 540             return Some(result);
 541         }
 542
 543         if !where_clause_str.is_empty() && !where_clause_str.contains('\n') {
 544             result.push('\n');
 545             let width = offset.block_indent + context.config.tab_spaces() - 1;
 546             let where_indent = Indent::new(0, width);
 547             result.push_str(&where_indent.to_string(context.config));
 548         }
 549         result.push_str(&where_clause_str);
 550
 551         match context.config.item_brace_style() {
 552             BraceStyle::AlwaysNextLine => {
 553                 result.push('\n');
 554                 result.push_str(&offset.to_string(context.config));
 555             }
 556             BraceStyle::PreferSameLine => result.push(' '),
 557             BraceStyle::SameLineWhere => {
 558                 if !where_clause_str.is_empty() {
 559                     result.push('\n');
 560                     result.push_str(&offset.to_string(context.config));
 561                 } else {
 562                     result.push(' ');
 563                 }
 564             }
 565         }
 566
 567         result.push('{');
 568
 569         let snippet = context.snippet(item.span);
 570         let open_pos = try_opt!(snippet.find_uncommented("{")) + 1;
 571
 572         if !items.is_empty() || contains_comment(&snippet[open_pos..]) {
 573             let mut visitor = FmtVisitor::from_codemap(context.parse_session, context.config);
 574             visitor.block_indent = offset.block_only().block_indent(context.config);
 575             visitor.last_pos = item.span.lo + BytePos(open_pos as u32);
 576
 577             for item in items {
 578                 visitor.visit_impl_item(item);
 579             }
 580
 581             visitor.format_missing(item.span.hi - BytePos(1));
 582
 583             let inner_indent_str = visitor.block_indent.to_string(context.config);
 584             let outer_indent_str = offset.block_only().to_string(context.config);
 585
 586             result.push('\n');
 587             result.push_str(&inner_indent_str);
 588             result.push_str(trim_newlines(visitor.buffer.to_string().trim()));
 589             result.push('\n');
 590             result.push_str(&outer_indent_str);
 591         }
 592
 593         if result.chars().last().unwrap() == '{' {
 594             result.push('\n');
 595             result.push_str(&offset.to_string(context.config));
 596         }
 597         result.push('}');
 598
 599         Some(result)
 600     } else {
 601         unreachable!();
 602     }
 603 }
 604
 605 fn is_impl_single_line(context: &RewriteContext,
 606                        items: &[ImplItem],
 607                        result: &str,
 608                        where_clause_str: &str,
 609                        item: &ast::Item)
 610                        -> Option<bool> {
 611     let snippet = context.snippet(item.span);
 612     let open_pos = try_opt!(snippet.find_uncommented("{")) + 1;
 613
 614     Some(context.config.impl_empty_single_line() && items.is_empty() &&
 615          result.len() + where_clause_str.len() <= context.config.max_width() &&
 616          !contains_comment(&snippet[open_pos..]))
 617 }
 618
 619 fn format_impl_ref_and_type(context: &RewriteContext,
 620                             item: &ast::Item,
 621                             offset: Indent,
 622                             split_at_for: bool)
 623                             -> Option<String> {
 624     if let ast::ItemKind::Impl(unsafety, polarity, ref generics, ref trait_ref, ref self_ty, _) =
 625         item.node {
 626         let mut result = String::new();
 627
 628         result.push_str(&format_visibility(&item.vis));
 629         result.push_str(format_unsafety(unsafety));
 630         result.push_str("impl");
 631
 632         let lo = context.codemap.span_after(item.span, "impl");
 633         let hi = match *trait_ref {
 634             Some(ref tr) => tr.path.span.lo,
 635             None => self_ty.span.lo,
 636         };
 637         let generics_indent = offset + last_line_width(&result);
 638         let shape = Shape::indented(generics_indent, context.config);
 639         let generics_str = try_opt!(rewrite_generics(context, generics, shape, mk_sp(lo, hi)));
 640         result.push_str(&generics_str);
 641
 642         if polarity == ast::ImplPolarity::Negative {
 643             result.push_str(" !");
 644         }
 645         if let Some(ref trait_ref) = *trait_ref {
 646             if polarity != ast::ImplPolarity::Negative {
 647                 result.push_str(" ");
 648             }
 649             let used_space = last_line_width(&result);
 650             let budget = try_opt!(context.config.max_width().checked_sub(used_space));
 651             let indent = offset + used_space;
 652             result.push_str(&*try_opt!(trait_ref.rewrite(context, Shape::legacy(budget, indent))));
 653
 654             if split_at_for {
 655                 result.push('\n');
 656
 657                 // Add indentation of one additional tab.
 658                 let width = offset.block_indent + context.config.tab_spaces();
 659                 let for_indent = Indent::new(0, width);
 660                 result.push_str(&for_indent.to_string(context.config));
 661
 662                 result.push_str("for");
 663             } else {
 664                 result.push_str(" for");
 665             }
 666         }
 667
 668         let mut used_space = last_line_width(&result);
 669         if generics.where_clause.predicates.is_empty() {
 670             // If there is no where clause adapt budget for type formatting to take space and curly
 671             // brace into account.
 672             match context.config.item_brace_style() {
 673                 BraceStyle::AlwaysNextLine => {}
 674                 BraceStyle::PreferSameLine => used_space += 2,
 675                 BraceStyle::SameLineWhere => used_space += 2,
 676             }
 677         }
 678
 679         // 1 = space before the type.
 680         let budget = try_opt!(context.config.max_width().checked_sub(used_space + 1));
 681         let indent = offset + result.len() + 1;
 682         let self_ty_str = self_ty.rewrite(context, Shape::legacy(budget, indent));
 683         if let Some(self_ty_str) = self_ty_str {
 684             result.push_str(" ");
 685             result.push_str(&self_ty_str);
 686             return Some(result);
 687         }
 688
 689         // Can't fit the self type on what's left of the line, so start a new one.
 690         let indent = offset.block_indent(context.config);
 691         result.push_str(&format!("\n{}", indent.to_string(context.config)));
 692         result.push_str(&*try_opt!(self_ty.rewrite(context,
 693                                                    Shape::indented(indent, context.config))));
 694         Some(result)
 695     } else {
 696         unreachable!();
 697     }
 698 }
 699
 700 pub fn format_struct(context: &RewriteContext,
 701                      item_name: &str,
 702                      ident: ast::Ident,
 703                      vis: &ast::Visibility,
 704                      struct_def: &ast::VariantData,
 705                      generics: Option<&ast::Generics>,
 706                      span: Span,
 707                      offset: Indent,
 708                      one_line_width: Option<usize>)
 709                      -> Option<String> {
 710     match *struct_def {
 711         ast::VariantData::Unit(..) => Some(format_unit_struct(item_name, ident, vis)),
 712         ast::VariantData::Tuple(ref fields, _) => {
 713             format_tuple_struct(context,
 714                                 item_name,
 715                                 ident,
 716                                 vis,
 717                                 fields,
 718                                 generics,
 719                                 span,
 720                                 offset)
 721         }
 722         ast::VariantData::Struct(ref fields, _) => {
 723             format_struct_struct(context,
 724                                  item_name,
 725                                  ident,
 726                                  vis,
 727                                  fields,
 728                                  generics,
 729                                  span,
 730                                  offset,
 731                                  one_line_width)
 732         }
 733     }
 734 }
 735
 736 pub fn format_trait(context: &RewriteContext, item: &ast::Item, offset: Indent) -> Option<String> {
 737     if let ast::ItemKind::Trait(unsafety, ref generics, ref type_param_bounds, ref trait_items) =
 738         item.node {
 739         let mut result = String::new();
 740         let header = format!("{}{}trait {}",
 741                              format_visibility(&item.vis),
 742                              format_unsafety(unsafety),
 743                              item.ident);
 744
 745         result.push_str(&header);
 746
 747         let body_lo = context.codemap.span_after(item.span, "{");
 748
 749         let generics_indent = offset + last_line_width(&result);
 750         let shape = Shape::indented(generics_indent, context.config);
 751         let generics_str =
 752             try_opt!(rewrite_generics(context, generics, shape, mk_sp(item.span.lo, body_lo)));
 753         result.push_str(&generics_str);
 754
 755         let trait_bound_str =
 756             try_opt!(rewrite_trait_bounds(context,
 757                                           type_param_bounds,
 758                                           Shape::legacy(context.config.max_width(), offset)));
 759         // If the trait, generics, and trait bound cannot fit on the same line,
 760         // put the trait bounds on an indented new line
 761         if offset.width() + last_line_width(&result) + trait_bound_str.len() >
 762            context.config.comment_width() {
 763             result.push('\n');
 764             let trait_indent = offset.block_only().block_indent(context.config);
 765             result.push_str(&trait_indent.to_string(context.config));
 766         }
 767         result.push_str(&trait_bound_str);
 768
 769         let has_body = !trait_items.is_empty();
 770
 771         let where_density =
 772             if (context.config.where_density() == Density::Compressed &&
 773                 (!result.contains('\n') ||
 774                  context.config.fn_args_layout() == IndentStyle::Block)) ||
 775                (context.config.fn_args_layout() == IndentStyle::Block && result.is_empty()) ||
 776                (context.config.where_density() == Density::CompressedIfEmpty && !has_body &&
 777                 !result.contains('\n')) {
 778                 Density::Compressed
 779             } else {
 780                 Density::Tall
 781             };
 782
 783         let where_budget = try_opt!(context
 784                                         .config
 785                                         .max_width()
 786                                         .checked_sub(last_line_width(&result)));
 787         let where_clause_str = try_opt!(rewrite_where_clause(context,
 788                                                              &generics.where_clause,
 789                                                              context.config.item_brace_style(),
 790                                                              Shape::legacy(where_budget,
 791                                                                            offset.block_only()),
 792                                                              where_density,
 793                                                              "{",
 794                                                              !has_body,
 795                                                              trait_bound_str.is_empty() &&
 796                                                              last_line_width(&generics_str) == 1,
 797                                                              None));
 798         // If the where clause cannot fit on the same line,
 799         // put the where clause on a new line
 800         if !where_clause_str.contains('\n') &&
 801            last_line_width(&result) + where_clause_str.len() + offset.width() >
 802            context.config.comment_width() {
 803             result.push('\n');
 804             let width = offset.block_indent + context.config.tab_spaces() - 1;
 805             let where_indent = Indent::new(0, width);
 806             result.push_str(&where_indent.to_string(context.config));
 807         }
 808         result.push_str(&where_clause_str);
 809
 810         match context.config.item_brace_style() {
 811             BraceStyle::AlwaysNextLine => {
 812                 result.push('\n');
 813                 result.push_str(&offset.to_string(context.config));
 814             }
 815             BraceStyle::PreferSameLine => result.push(' '),
 816             BraceStyle::SameLineWhere => {
 817                 if !where_clause_str.is_empty() &&
 818                    (!trait_items.is_empty() || result.contains('\n')) {
 819                     result.push('\n');
 820                     result.push_str(&offset.to_string(context.config));
 821                 } else {
 822                     result.push(' ');
 823                 }
 824             }
 825         }
 826         result.push('{');
 827
 828         let snippet = context.snippet(item.span);
 829         let open_pos = try_opt!(snippet.find_uncommented("{")) + 1;
 830
 831         if !trait_items.is_empty() || contains_comment(&snippet[open_pos..]) {
 832             let mut visitor = FmtVisitor::from_codemap(context.parse_session, context.config);
 833             visitor.block_indent = offset.block_only().block_indent(context.config);
 834             visitor.last_pos = item.span.lo + BytePos(open_pos as u32);
 835
 836             for item in trait_items {
 837                 visitor.visit_trait_item(item);
 838             }
 839
 840             visitor.format_missing(item.span.hi - BytePos(1));
 841
 842             let inner_indent_str = visitor.block_indent.to_string(context.config);
 843             let outer_indent_str = offset.block_only().to_string(context.config);
 844
 845             result.push('\n');
 846             result.push_str(&inner_indent_str);
 847             result.push_str(trim_newlines(visitor.buffer.to_string().trim()));
 848             result.push('\n');
 849             result.push_str(&outer_indent_str);
 850         } else if result.contains('\n') {
 851             result.push('\n');
 852         }
 853
 854         result.push('}');
 855         Some(result)
 856     } else {
 857         unreachable!();
 858     }
 859 }
 860
 861 fn format_unit_struct(item_name: &str, ident: ast::Ident, vis: &ast::Visibility) -> String {
 862     format!("{};", format_header(item_name, ident, vis))
 863 }
 864
 865 fn format_struct_struct(context: &RewriteContext,
 866                         item_name: &str,
 867                         ident: ast::Ident,
 868                         vis: &ast::Visibility,
 869                         fields: &[ast::StructField],
 870                         generics: Option<&ast::Generics>,
 871                         span: Span,
 872                         offset: Indent,
 873                         one_line_width: Option<usize>)
 874                         -> Option<String> {
 875     let mut result = String::with_capacity(1024);
 876
 877     let header_str = format_header(item_name, ident, vis);
 878     result.push_str(&header_str);
 879
 880     let body_lo = context.codemap.span_after(span, "{");
 881
 882     let generics_str = match generics {
 883         Some(g) => {
 884             try_opt!(format_generics(context,
 885                                      g,
 886                                      "{",
 887                                      "{",
 888                                      context.config.item_brace_style(),
 889                                      fields.is_empty(),
 890                                      offset,
 891                                      mk_sp(span.lo, body_lo)))
 892         }
 893         None => {
 894             if context.config.item_brace_style() == BraceStyle::AlwaysNextLine &&
 895                !fields.is_empty() {
 896                 format!("\n{}{{", offset.block_only().to_string(context.config))
 897             } else {
 898                 " {".to_owned()
 899             }
 900         }
 901     };
 902     result.push_str(&generics_str);
 903
 904     if fields.is_empty() {
 905         let snippet = context.snippet(mk_sp(body_lo, span.hi - BytePos(1)));
 906         if snippet.trim().is_empty() {
 907             // `struct S {}`
 908         } else if snippet.trim_right_matches(&[' ', '\t'][..]).ends_with('\n') {
 909             // fix indent
 910             result.push_str(&snippet.trim_right());
 911             result.push('\n');
 912             result.push_str(&offset.to_string(context.config));
 913         } else {
 914             result.push_str(&snippet);
 915         }
 916         result.push('}');
 917         return Some(result);
 918     }
 919
 920     let item_indent = offset.block_indent(context.config);
 921     // 1 = ","
 922     let item_budget = try_opt!(context
 923                                    .config
 924                                    .max_width()
 925                                    .checked_sub(item_indent.width() + 1));
 926
 927     let items =
 928         itemize_list(context.codemap,
 929                      fields.iter(),
 930                      "}",
 931                      |field| {
 932                          // Include attributes and doc comments, if present
 933                          if !field.attrs.is_empty() {
 934                              field.attrs[0].span.lo
 935                          } else {
 936                              field.span.lo
 937                          }
 938                      },
 939                      |field| field.ty.span.hi,
 940                      |field| field.rewrite(context, Shape::legacy(item_budget, item_indent)),
 941                      context.codemap.span_after(span, "{"),
 942                      span.hi)
 943             .collect::<Vec<_>>();
 944     // 1 = ,
 945     let budget = context.config.max_width() - offset.width() + context.config.tab_spaces() - 1;
 946
 947     let tactic = match one_line_width {
 948         Some(w) => definitive_tactic(&items, ListTactic::LimitedHorizontalVertical(w), budget),
 949         None => DefinitiveListTactic::Vertical,
 950     };
 951
 952     let fmt = ListFormatting {
 953         tactic: tactic,
 954         separator: ",",
 955         trailing_separator: context.config.trailing_comma(),
 956         shape: Shape::legacy(budget, item_indent),
 957         ends_with_newline: true,
 958         config: context.config,
 959     };
 960     let items_str = try_opt!(write_list(&items, &fmt));
 961     if one_line_width.is_some() && !items_str.contains('\n') {
 962         Some(format!("{} {} }}", result, items_str))
 963     } else {
 964         Some(format!("{}\n{}{}\n{}}}",
 965                      result,
 966                      offset
 967                          .block_indent(context.config)
 968                          .to_string(context.config),
 969                      items_str,
 970                      offset.to_string(context.config)))
 971     }
 972 }
 973
 974 fn format_tuple_struct(context: &RewriteContext,
 975                        item_name: &str,
 976                        ident: ast::Ident,
 977                        vis: &ast::Visibility,
 978                        fields: &[ast::StructField],
 979                        generics: Option<&ast::Generics>,
 980                        span: Span,
 981                        offset: Indent)
 982                        -> Option<String> {
 983     let mut result = String::with_capacity(1024);
 984
 985     let header_str = format_header(item_name, ident, vis);
 986     result.push_str(&header_str);
 987
 988     let body_lo = if fields.is_empty() {
 989         context.codemap.span_after(span, "(")
 990     } else {
 991         fields[0].span.lo
 992     };
 993
 994     let where_clause_str = match generics {
 995         Some(generics) => {
 996             let generics_indent = offset + last_line_width(&header_str);
 997             let shape = Shape::indented(generics_indent, context.config);
 998             let generics_str =
 999                 try_opt!(rewrite_generics(context, generics, shape, mk_sp(span.lo, body_lo)));
1000             result.push_str(&generics_str);
1001
1002             let where_budget = try_opt!(context
1003                                             .config
1004                                             .max_width()
1005                                             .checked_sub(last_line_width(&result)));
1006             try_opt!(rewrite_where_clause(context,
1007                                           &generics.where_clause,
1008                                           context.config.item_brace_style(),
1009                                           Shape::legacy(where_budget, offset.block_only()),
1010                                           Density::Compressed,
1011                                           ";",
1012                                           true,
1013                                           false,
1014                                           None))
1015         }
1016         None => "".to_owned(),
1017     };
1018
1019     if fields.is_empty() {
1020         result.push('(');
1021         let snippet = context.snippet(mk_sp(body_lo, context.codemap.span_before(span, ")")));
1022         if snippet.is_empty() {
1023             // `struct S ()`
1024         } else if snippet.trim_right_matches(&[' ', '\t'][..]).ends_with('\n') {
1025             result.push_str(&snippet.trim_right());
1026             result.push('\n');
1027             result.push_str(&offset.to_string(context.config));
1028         } else {
1029             result.push_str(&snippet);
1030         }
1031         result.push(')');
1032     } else {
1033         let (tactic, item_indent) = match context.config.fn_args_layout() {
1034             IndentStyle::Visual => {
1035                 // 1 = `(`
1036                 (ListTactic::HorizontalVertical, offset.block_only() + result.len() + 1)
1037             }
1038             IndentStyle::Block => {
1039                 (ListTactic::HorizontalVertical, offset.block_only().block_indent(&context.config))
1040             }
1041         };
1042         // 3 = `();`
1043         let item_budget = try_opt!(context
1044                                        .config
1045                                        .max_width()
1046                                        .checked_sub(item_indent.width() + 3));
1047
1048         let items =
1049             itemize_list(context.codemap,
1050                          fields.iter(),
1051                          ")",
1052                          |field| {
1053                              // Include attributes and doc comments, if present
1054                              if !field.attrs.is_empty() {
1055                                  field.attrs[0].span.lo
1056                              } else {
1057                                  field.span.lo
1058                              }
1059                          },
1060                          |field| field.ty.span.hi,
1061                          |field| field.rewrite(context, Shape::legacy(item_budget, item_indent)),
1062                          context.codemap.span_after(span, "("),
1063                          span.hi);
1064         let body_budget =
1065             try_opt!(context
1066                          .config
1067                          .max_width()
1068                          .checked_sub(offset.block_only().width() + result.len() + 3));
1069         let body = try_opt!(list_helper(items,
1070                                         // TODO budget is wrong in block case
1071                                         Shape::legacy(body_budget, item_indent),
1072                                         context.config,
1073                                         tactic));
1074
1075         if context.config.fn_args_layout() == IndentStyle::Visual || !body.contains('\n') {
1076             result.push('(');
1077             if context.config.spaces_within_parens() && body.len() > 0 {
1078                 result.push(' ');
1079             }
1080
1081             result.push_str(&body);
1082
1083             if context.config.spaces_within_parens() && body.len() > 0 {
1084                 result.push(' ');
1085             }
1086             result.push(')');
1087         } else {
1088             result.push_str("(\n");
1089             result.push_str(&item_indent.to_string(&context.config));
1090             result.push_str(&body);
1091             result.push('\n');
1092             result.push_str(&offset.block_only().to_string(&context.config));
1093             result.push(')');
1094         }
1095     }
1096
1097     if !where_clause_str.is_empty() && !where_clause_str.contains('\n') &&
1098        (result.contains('\n') ||
1099         offset.block_indent + result.len() + where_clause_str.len() + 1 >
1100         context.config.max_width()) {
1101         // We need to put the where clause on a new line, but we didn't
1102         // know that earlier, so the where clause will not be indented properly.
1103         result.push('\n');
1104         result.push_str(&(offset.block_only() + (context.config.tab_spaces() - 1))
1105                             .to_string(context.config));
1106     }
1107     result.push_str(&where_clause_str);
1108
1109     Some(result)
1110 }
1111
1112 pub fn rewrite_type_alias(context: &RewriteContext,
1113                           indent: Indent,
1114                           ident: ast::Ident,
1115                           ty: &ast::Ty,
1116                           generics: &ast::Generics,
1117                           vis: &ast::Visibility,
1118                           span: Span)
1119                           -> Option<String> {
1120     let mut result = String::new();
1121
1122     result.push_str(&format_visibility(vis));
1123     result.push_str("type ");
1124     result.push_str(&ident.to_string());
1125
1126     let generics_indent = indent + result.len();
1127     let generics_span = mk_sp(context.codemap.span_after(span, "type"), ty.span.lo);
1128     let shape = try_opt!(Shape::indented(generics_indent, context.config).sub_width(" =".len()));
1129     let generics_str = try_opt!(rewrite_generics(context, generics, shape, generics_span));
1130
1131     result.push_str(&generics_str);
1132
1133     let where_budget = try_opt!(context
1134                                     .config
1135                                     .max_width()
1136                                     .checked_sub(last_line_width(&result)));
1137     let where_clause_str = try_opt!(rewrite_where_clause(context,
1138                                                          &generics.where_clause,
1139                                                          context.config.item_brace_style(),
1140                                                          Shape::legacy(where_budget, indent),
1141                                                          context.config.where_density(),
1142                                                          "=",
1143                                                          true,
1144                                                          true,
1145                                                          Some(span.hi)));
1146     result.push_str(&where_clause_str);
1147     result.push_str(" = ");
1148
1149     let line_width = last_line_width(&result);
1150     // This checked_sub may fail as the extra space after '=' is not taken into account
1151     // In that case the budget is set to 0 which will make ty.rewrite retry on a new line
1152     let budget = context
1153         .config
1154         .max_width()
1155         .checked_sub(indent.width() + line_width + ";".len())
1156         .unwrap_or(0);
1157     let type_indent = indent + line_width;
1158     // Try to fit the type on the same line
1159     let ty_str = try_opt!(ty.rewrite(context, Shape::legacy(budget, type_indent))
1160                               .or_else(|| {
1161         // The line was too short, try to put the type on the next line
1162
1163         // Remove the space after '='
1164         result.pop();
1165         let type_indent = indent.block_indent(context.config);
1166         result.push('\n');
1167         result.push_str(&type_indent.to_string(context.config));
1168         let budget = try_opt!(context
1169                                   .config
1170                                   .max_width()
1171                                   .checked_sub(type_indent.width() + ";".len()));
1172         ty.rewrite(context, Shape::legacy(budget, type_indent))
1173     }));
1174     result.push_str(&ty_str);
1175     result.push_str(";");
1176     Some(result)
1177 }
1178
1179 fn type_annotation_spacing(config: &Config) -> (&str, &str) {
1180     (if config.space_before_type_annotation() {
1181          " "
1182      } else {
1183          ""
1184      },
1185      if config.space_after_type_annotation_colon() {
1186          " "
1187      } else {
1188          ""
1189      })
1190 }
1191
1192 impl Rewrite for ast::StructField {
1193     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
1194         if contains_skip(&self.attrs) {
1195             let span = context.snippet(mk_sp(self.attrs[0].span.lo, self.span.hi));
1196             return wrap_str(span, context.config.max_width(), shape);
1197         }
1198
1199         let name = self.ident;
1200         let vis = format_visibility(&self.vis);
1201         let mut attr_str = try_opt!(self.attrs.rewrite(context,
1202                                                        Shape::indented(shape.indent,
1203                                                                        context.config)));
1204         if !attr_str.is_empty() {
1205             attr_str.push('\n');
1206             attr_str.push_str(&shape.indent.to_string(context.config));
1207         }
1208
1209         let type_annotation_spacing = type_annotation_spacing(context.config);
1210         let mut result = match name {
1211             Some(name) => format!("{}{}{}{}:", attr_str, vis, name, type_annotation_spacing.0),
1212             None => format!("{}{}", attr_str, vis),
1213         };
1214
1215         let type_offset = shape.indent.block_indent(context.config);
1216         let rewrite_type_in_next_line = || {
1217             self.ty
1218                 .rewrite(context, Shape::indented(type_offset, context.config))
1219         };
1220
1221         let last_line_width = last_line_width(&result) + type_annotation_spacing.1.len();
1222         let budget = try_opt!(shape.width.checked_sub(last_line_width));
1223         let ty_rewritten =
1224             self.ty.rewrite(context,
1225                             Shape::legacy(budget, shape.indent + last_line_width));
1226         match ty_rewritten {
1227             Some(ref ty) if ty.contains('\n') => {
1228                 let new_ty = rewrite_type_in_next_line();
1229                 match new_ty {
1230                     Some(ref new_ty) if !new_ty.contains('\n') &&
1231                                         new_ty.len() + type_offset.width() <=
1232                                         context.config.max_width() => {
1233                         Some(format!("{}\n{}{}",
1234                                      result,
1235                                      type_offset.to_string(&context.config),
1236                                      &new_ty))
1237                     }
1238                     _ => {
1239                         if name.is_some() {
1240                             result.push_str(type_annotation_spacing.1);
1241                         }
1242                         Some(result + &ty)
1243                     }
1244                 }
1245             }
1246             Some(ty) => {
1247                 if name.is_some() {
1248                     result.push_str(type_annotation_spacing.1);
1249                 }
1250                 Some(result + &ty)
1251             }
1252             None => {
1253                 let ty = try_opt!(rewrite_type_in_next_line());
1254                 Some(format!("{}\n{}{}",
1255                              result,
1256                              type_offset.to_string(&context.config),
1257                              &ty))
1258             }
1259         }
1260     }
1261 }
1262
1263 pub fn rewrite_static(prefix: &str,
1264                       vis: &ast::Visibility,
1265                       ident: ast::Ident,
1266                       ty: &ast::Ty,
1267                       mutability: ast::Mutability,
1268                       expr_opt: Option<&ptr::P<ast::Expr>>,
1269                       offset: Indent,
1270                       context: &RewriteContext)
1271                       -> Option<String> {
1272     let type_annotation_spacing = type_annotation_spacing(context.config);
1273     let prefix = format!("{}{} {}{}{}:{}",
1274                          format_visibility(vis),
1275                          prefix,
1276                          format_mutability(mutability),
1277                          ident,
1278                          type_annotation_spacing.0,
1279                          type_annotation_spacing.1);
1280     // 2 = " =".len()
1281     let ty_str = try_opt!(ty.rewrite(context,
1282                                      Shape::legacy(context.config.max_width() -
1283                                                    offset.block_indent -
1284                                                    prefix.len() -
1285                                                    2,
1286                                                    offset.block_only())));
1287
1288     if let Some(expr) = expr_opt {
1289         let lhs = format!("{}{} =", prefix, ty_str);
1290         // 1 = ;
1291         let remaining_width = context.config.max_width() - offset.block_indent - 1;
1292         rewrite_assign_rhs(context,
1293                            lhs,
1294                            expr,
1295                            Shape::legacy(remaining_width, offset.block_only()))
1296             .map(|s| s + ";")
1297     } else {
1298         let lhs = format!("{}{};", prefix, ty_str);
1299         Some(lhs)
1300     }
1301 }
1302
1303 pub fn rewrite_associated_type(ident: ast::Ident,
1304                                ty_opt: Option<&ptr::P<ast::Ty>>,
1305                                ty_param_bounds_opt: Option<&ast::TyParamBounds>,
1306                                context: &RewriteContext,
1307                                indent: Indent)
1308                                -> Option<String> {
1309     let prefix = format!("type {}", ident);
1310
1311     let type_bounds_str = if let Some(ty_param_bounds) = ty_param_bounds_opt {
1312         let joiner = match context.config.type_punctuation_density() {
1313             TypeDensity::Compressed => "+",
1314             TypeDensity::Wide => " + ",
1315         };
1316         let bounds: &[_] = ty_param_bounds;
1317         let bound_str =
1318             try_opt!(bounds
1319                          .iter()
1320                          .map(|ty_bound| {
1321                                   ty_bound.rewrite(context,
1322                                                    Shape::legacy(context.config.max_width(),
1323                                                                  indent))
1324                               })
1325                          .collect::<Option<Vec<_>>>())
1326                 .join(joiner);
1327         if bounds.len() > 0 {
1328             format!(": {}", bound_str)
1329         } else {
1330             String::new()
1331         }
1332     } else {
1333         String::new()
1334     };
1335
1336     if let Some(ty) = ty_opt {
1337         let ty_str = try_opt!(ty.rewrite(context,
1338                                          Shape::legacy(context.config.max_width() -
1339                                                        indent.block_indent -
1340                                                        prefix.len() -
1341                                                        2,
1342                                                        indent.block_only())));
1343         Some(format!("{} = {};", prefix, ty_str))
1344     } else {
1345         Some(format!("{}{};", prefix, type_bounds_str))
1346     }
1347 }
1348
1349 pub fn rewrite_associated_impl_type(ident: ast::Ident,
1350                                     defaultness: ast::Defaultness,
1351                                     ty_opt: Option<&ptr::P<ast::Ty>>,
1352                                     ty_param_bounds_opt: Option<&ast::TyParamBounds>,
1353                                     context: &RewriteContext,
1354                                     indent: Indent)
1355                                     -> Option<String> {
1356     let result =
1357         try_opt!(rewrite_associated_type(ident, ty_opt, ty_param_bounds_opt, context, indent));
1358
1359     match defaultness {
1360         ast::Defaultness::Default => Some(format!("default {}", result)),
1361         _ => Some(result),
1362     }
1363 }
1364
1365 impl Rewrite for ast::FunctionRetTy {
1366     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
1367         match *self {
1368             ast::FunctionRetTy::Default(_) => Some(String::new()),
1369             ast::FunctionRetTy::Ty(ref ty) => {
1370                 let inner_width = try_opt!(shape.width.checked_sub(3));
1371                 ty.rewrite(context, Shape::legacy(inner_width, shape.indent + 3))
1372                     .map(|r| format!("-> {}", r))
1373             }
1374         }
1375     }
1376 }
1377
1378 impl Rewrite for ast::Arg {
1379     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
1380         if is_named_arg(self) {
1381             let mut result = try_opt!(self.pat.rewrite(context,
1382                                                        Shape::legacy(shape.width, shape.indent)));
1383
1384             if self.ty.node != ast::TyKind::Infer {
1385                 if context.config.space_before_type_annotation() {
1386                     result.push_str(" ");
1387                 }
1388                 result.push_str(":");
1389                 if context.config.space_after_type_annotation_colon() {
1390                     result.push_str(" ");
1391                 }
1392                 let max_width = try_opt!(shape.width.checked_sub(result.len()));
1393                 let ty_str = try_opt!(self.ty.rewrite(context,
1394                                                       Shape::legacy(max_width,
1395                                                                     shape.indent + result.len())));
1396                 result.push_str(&ty_str);
1397             }
1398
1399             Some(result)
1400         } else {
1401             self.ty.rewrite(context, shape)
1402         }
1403     }
1404 }
1405
1406 fn rewrite_explicit_self(explicit_self: &ast::ExplicitSelf,
1407                          args: &[ast::Arg],
1408                          context: &RewriteContext)
1409                          -> Option<String> {
1410     match explicit_self.node {
1411         ast::SelfKind::Region(lt, m) => {
1412             let mut_str = format_mutability(m);
1413             match lt {
1414                 Some(ref l) => {
1415                     let lifetime_str = try_opt!(l.rewrite(context,
1416                                                           Shape::legacy(usize::max_value(),
1417                                                                         Indent::empty())));
1418                     Some(format!("&{} {}self", lifetime_str, mut_str))
1419                 }
1420                 None => Some(format!("&{}self", mut_str)),
1421             }
1422         }
1423         ast::SelfKind::Explicit(ref ty, _) => {
1424             assert!(!args.is_empty(), "&[ast::Arg] shouldn't be empty.");
1425
1426             let mutability = explicit_self_mutability(&args[0]);
1427             let type_str = try_opt!(ty.rewrite(context,
1428                                                Shape::legacy(usize::max_value(), Indent::empty())));
1429
1430             Some(format!("{}self: {}", format_mutability(mutability), type_str))
1431         }
1432         ast::SelfKind::Value(_) => {
1433             assert!(!args.is_empty(), "&[ast::Arg] shouldn't be empty.");
1434
1435             let mutability = explicit_self_mutability(&args[0]);
1436
1437             Some(format!("{}self", format_mutability(mutability)))
1438         }
1439     }
1440 }
1441
1442 // Hacky solution caused by absence of `Mutability` in `SelfValue` and
1443 // `SelfExplicit` variants of `ast::ExplicitSelf_`.
1444 fn explicit_self_mutability(arg: &ast::Arg) -> ast::Mutability {
1445     if let ast::PatKind::Ident(ast::BindingMode::ByValue(mutability), _, _) = arg.pat.node {
1446         mutability
1447     } else {
1448         unreachable!()
1449     }
1450 }
1451
1452 pub fn span_lo_for_arg(arg: &ast::Arg) -> BytePos {
1453     if is_named_arg(arg) {
1454         arg.pat.span.lo
1455     } else {
1456         arg.ty.span.lo
1457     }
1458 }
1459
1460 pub fn span_hi_for_arg(arg: &ast::Arg) -> BytePos {
1461     match arg.ty.node {
1462         ast::TyKind::Infer if is_named_arg(arg) => arg.pat.span.hi,
1463         _ => arg.ty.span.hi,
1464     }
1465 }
1466
1467 pub fn is_named_arg(arg: &ast::Arg) -> bool {
1468     if let ast::PatKind::Ident(_, ident, _) = arg.pat.node {
1469         ident.node != symbol::keywords::Invalid.ident()
1470     } else {
1471         true
1472     }
1473 }
1474
1475 fn span_for_return(ret: &ast::FunctionRetTy) -> Span {
1476     match *ret {
1477         ast::FunctionRetTy::Default(ref span) => span.clone(),
1478         ast::FunctionRetTy::Ty(ref ty) => ty.span,
1479     }
1480 }
1481
1482 fn span_for_ty_param(ty: &ast::TyParam) -> Span {
1483     // Note that ty.span is the span for ty.ident, not the whole item.
1484     let lo = ty.span.lo;
1485     if let Some(ref def) = ty.default {
1486         return mk_sp(lo, def.span.hi);
1487     }
1488     if ty.bounds.is_empty() {
1489         return ty.span;
1490     }
1491     let hi = match ty.bounds[ty.bounds.len() - 1] {
1492         ast::TyParamBound::TraitTyParamBound(ref ptr, _) => ptr.span.hi,
1493         ast::TyParamBound::RegionTyParamBound(ref l) => l.span.hi,
1494     };
1495     mk_sp(lo, hi)
1496 }
1497
1498 fn span_for_where_pred(pred: &ast::WherePredicate) -> Span {
1499     match *pred {
1500         ast::WherePredicate::BoundPredicate(ref p) => p.span,
1501         ast::WherePredicate::RegionPredicate(ref p) => p.span,
1502         ast::WherePredicate::EqPredicate(ref p) => p.span,
1503     }
1504 }
1505
1506 // Return type is (result, force_new_line_for_brace)
1507 fn rewrite_fn_base(context: &RewriteContext,
1508                    indent: Indent,
1509                    ident: ast::Ident,
1510                    fd: &ast::FnDecl,
1511                    generics: &ast::Generics,
1512                    unsafety: ast::Unsafety,
1513                    constness: ast::Constness,
1514                    defaultness: ast::Defaultness,
1515                    abi: abi::Abi,
1516                    vis: &ast::Visibility,
1517                    span: Span,
1518                    newline_brace: bool,
1519                    has_body: bool,
1520                    has_braces: bool)
1521                    -> Option<(String, bool)> {
1522     let mut force_new_line_for_brace = false;
1523
1524     let where_clause = &generics.where_clause;
1525
1526     let mut result = String::with_capacity(1024);
1527     // Vis unsafety abi.
1528     result.push_str(&*format_visibility(vis));
1529
1530     if let ast::Defaultness::Default = defaultness {
1531         result.push_str("default ");
1532     }
1533
1534     if let ast::Constness::Const = constness {
1535         result.push_str("const ");
1536     }
1537
1538     result.push_str(::utils::format_unsafety(unsafety));
1539
1540     if abi != abi::Abi::Rust {
1541         result.push_str(&::utils::format_abi(abi, context.config.force_explicit_abi()));
1542     }
1543
1544     // fn foo
1545     result.push_str("fn ");
1546     result.push_str(&ident.to_string());
1547
1548     // Generics.
1549     let generics_indent = indent + last_line_width(&result);
1550     let generics_span = mk_sp(span.lo, span_for_return(&fd.output).lo);
1551     let shape = Shape::indented(generics_indent, context.config);
1552     let generics_str = try_opt!(rewrite_generics(context, generics, shape, generics_span));
1553     result.push_str(&generics_str);
1554
1555     let snuggle_angle_bracket = last_line_width(&generics_str) == 1;
1556
1557     // Note that the width and indent don't really matter, we'll re-layout the
1558     // return type later anyway.
1559     let ret_str = try_opt!(fd.output
1560                                .rewrite(&context, Shape::indented(indent, context.config)));
1561
1562     let multi_line_ret_str = ret_str.contains('\n');
1563     let ret_str_len = if multi_line_ret_str { 0 } else { ret_str.len() };
1564
1565     // Args.
1566     let (mut one_line_budget, mut multi_line_budget, mut arg_indent) =
1567         try_opt!(compute_budgets_for_args(context,
1568                                           &result,
1569                                           indent,
1570                                           ret_str_len,
1571                                           newline_brace,
1572                                           has_braces));
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                              arg_str.chars().last().map_or(false, |c| c == ',');
1631
1632     let put_args_in_block = match context.config.fn_args_layout() {
1633         IndentStyle::Block => multi_line_arg_str || generics_str.contains('\n'),
1634         _ => false,
1635     } && !fd.inputs.is_empty();
1636
1637     if put_args_in_block {
1638         arg_indent = indent.block_indent(context.config);
1639         result.push('\n');
1640         result.push_str(&arg_indent.to_string(context.config));
1641         result.push_str(&arg_str);
1642         result.push('\n');
1643         result.push_str(&indent.to_string(context.config));
1644         result.push(')');
1645     } else {
1646         result.push_str(&arg_str);
1647         if context.config.spaces_within_parens() && fd.inputs.len() > 0 {
1648             result.push(' ')
1649         }
1650         result.push(')');
1651     }
1652
1653     // Return type.
1654     if !ret_str.is_empty() {
1655         let ret_should_indent = match context.config.fn_args_layout() {
1656             // If our args are block layout then we surely must have space.
1657             IndentStyle::Block if put_args_in_block => false,
1658             _ => {
1659                 // If we've already gone multi-line, or the return type would push over the max
1660                 // width, then put the return type on a new line. With the +1 for the signature
1661                 // length an additional space between the closing parenthesis of the argument and
1662                 // the arrow '->' is considered.
1663                 let mut sig_length = result.len() + indent.width() + ret_str_len + 1;
1664
1665                 // If there is no where clause, take into account the space after the return type
1666                 // and the brace.
1667                 if where_clause.predicates.is_empty() {
1668                     sig_length += 2;
1669                 }
1670
1671                 let overlong_sig = sig_length > context.config.max_width();
1672
1673                 result.contains('\n') || multi_line_ret_str || overlong_sig
1674             }
1675         };
1676         let ret_indent = if ret_should_indent {
1677             let indent = match context.config.fn_return_indent() {
1678                 ReturnIndent::WithWhereClause => indent + 4,
1679                 // Aligning with non-existent args looks silly.
1680                 _ if arg_str.is_empty() => {
1681                     force_new_line_for_brace = true;
1682                     indent + 4
1683                 }
1684                 // FIXME: we might want to check that using the arg indent
1685                 // doesn't blow our budget, and if it does, then fallback to
1686                 // the where clause indent.
1687                 _ => arg_indent,
1688             };
1689
1690             result.push('\n');
1691             result.push_str(&indent.to_string(context.config));
1692             indent
1693         } else {
1694             result.push(' ');
1695             Indent::new(indent.width(), result.len())
1696         };
1697
1698         if multi_line_ret_str || ret_should_indent {
1699             // Now that we know the proper indent and width, we need to
1700             // re-layout the return type.
1701             let ret_str = try_opt!(fd.output.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| arg.rewrite(&context, Shape::legacy(multi_line_budget, arg_indent)))
1787                      .collect::<Option<Vec<_>>>());
1788
1789     // Account for sugary self.
1790     // FIXME: the comment for the self argument is dropped. This is blocked
1791     // on rust issue #27522.
1792     let min_args = explicit_self
1793         .and_then(|explicit_self| rewrite_explicit_self(explicit_self, args, context))
1794         .map_or(1, |self_str| {
1795             arg_item_strs[0] = self_str;
1796             2
1797         });
1798
1799     // Comments between args.
1800     let mut arg_items = Vec::new();
1801     if min_args == 2 {
1802         arg_items.push(ListItem::from_str(""));
1803     }
1804
1805     // FIXME(#21): if there are no args, there might still be a comment, but
1806     // without spans for the comment or parens, there is no chance of
1807     // getting it right. You also don't get to put a comment on self, unless
1808     // it is explicit.
1809     if args.len() >= min_args || variadic {
1810         let comment_span_start = if min_args == 2 {
1811             let second_arg_start = if arg_has_pattern(&args[1]) {
1812                 args[1].pat.span.lo
1813             } else {
1814                 args[1].ty.span.lo
1815             };
1816             let reduced_span = mk_sp(span.lo, second_arg_start);
1817
1818             context.codemap.span_after_last(reduced_span, ",")
1819         } else {
1820             span.lo
1821         };
1822
1823         enum ArgumentKind<'a> {
1824             Regular(&'a ast::Arg),
1825             Variadic(BytePos),
1826         }
1827
1828         let variadic_arg = if variadic {
1829             let variadic_span = mk_sp(args.last().unwrap().ty.span.hi, span.hi);
1830             let variadic_start = context.codemap.span_after(variadic_span, "...") - BytePos(3);
1831             Some(ArgumentKind::Variadic(variadic_start))
1832         } else {
1833             None
1834         };
1835
1836         let more_items = itemize_list(context.codemap,
1837                                       args[min_args - 1..]
1838                                           .iter()
1839                                           .map(ArgumentKind::Regular)
1840                                           .chain(variadic_arg),
1841                                       ")",
1842                                       |arg| match *arg {
1843                                           ArgumentKind::Regular(arg) => span_lo_for_arg(arg),
1844                                           ArgumentKind::Variadic(start) => start,
1845                                       },
1846                                       |arg| match *arg {
1847                                           ArgumentKind::Regular(arg) => arg.ty.span.hi,
1848                                           ArgumentKind::Variadic(start) => start + BytePos(3),
1849                                       },
1850                                       |arg| match *arg {
1851                                           ArgumentKind::Regular(..) => None,
1852                                           ArgumentKind::Variadic(..) => Some("...".to_owned()),
1853                                       },
1854                                       comment_span_start,
1855                                       span.hi);
1856
1857         arg_items.extend(more_items);
1858     }
1859
1860     let fits_in_one_line = !generics_str_contains_newline &&
1861                            (arg_items.len() == 0 ||
1862                             arg_items.len() == 1 && arg_item_strs[0].len() <= one_line_budget);
1863
1864     for (item, arg) in arg_items.iter_mut().zip(arg_item_strs) {
1865         item.item = Some(arg);
1866     }
1867
1868     let (indent, trailing_comma, end_with_newline) = match context.config.fn_args_layout() {
1869         IndentStyle::Block if fits_in_one_line => {
1870             (indent.block_indent(context.config), SeparatorTactic::Never, true)
1871         }
1872         IndentStyle::Block => {
1873             (indent.block_indent(context.config), SeparatorTactic::Vertical, true)
1874         }
1875         IndentStyle::Visual => (arg_indent, SeparatorTactic::Never, false),
1876     };
1877
1878     let tactic = definitive_tactic(&arg_items,
1879                                    context.config.fn_args_density().to_list_tactic(),
1880                                    one_line_budget);
1881     let budget = match tactic {
1882         DefinitiveListTactic::Horizontal => one_line_budget,
1883         _ => multi_line_budget,
1884     };
1885
1886     debug!("rewrite_args: budget: {}, tactic: {:?}", budget, tactic);
1887
1888     let fmt = ListFormatting {
1889         tactic: tactic,
1890         separator: ",",
1891         trailing_separator: trailing_comma,
1892         shape: Shape::legacy(budget, indent),
1893         ends_with_newline: end_with_newline,
1894         config: context.config,
1895     };
1896
1897     write_list(&arg_items, &fmt)
1898 }
1899
1900 fn arg_has_pattern(arg: &ast::Arg) -> bool {
1901     if let ast::PatKind::Ident(_, ident, _) = arg.pat.node {
1902         ident.node != symbol::keywords::Invalid.ident()
1903     } else {
1904         true
1905     }
1906 }
1907
1908 fn compute_budgets_for_args(context: &RewriteContext,
1909                             result: &str,
1910                             indent: Indent,
1911                             ret_str_len: usize,
1912                             newline_brace: bool,
1913                             has_braces: bool)
1914                             -> Option<((usize, usize, Indent))> {
1915     debug!("compute_budgets_for_args {} {:?}, {}, {}",
1916            result.len(),
1917            indent,
1918            ret_str_len,
1919            newline_brace);
1920     // Try keeping everything on the same line.
1921     if !result.contains('\n') {
1922         // 2 = `()`, 3 = `() `, space is before ret_string.
1923         let overhead = if ret_str_len == 0 { 2 } else { 3 };
1924         let mut used_space = indent.width() + result.len() + ret_str_len + overhead;
1925         if has_braces {
1926             if !newline_brace {
1927                 // 2 = `{}`
1928                 used_space += 2;
1929             }
1930         } else {
1931             // 1 = `;`
1932             used_space += 1;
1933         }
1934         let one_line_budget = context
1935             .config
1936             .max_width()
1937             .checked_sub(used_space)
1938             .unwrap_or(0);
1939
1940         if one_line_budget > 0 {
1941             // 4 = "() {".len()
1942             let multi_line_budget = try_opt!(context
1943                                                  .config
1944                                                  .max_width()
1945                                                  .checked_sub(indent.width() + result.len() + 4));
1946
1947             return Some((one_line_budget, multi_line_budget, indent + result.len() + 1));
1948         }
1949     }
1950
1951     // Didn't work. we must force vertical layout and put args on a newline.
1952     let new_indent = indent.block_indent(context.config);
1953     let used_space = new_indent.width() + 4; // Account for `(` and `)` and possibly ` {`.
1954     let max_space = context.config.max_width();
1955     if used_space <= max_space {
1956         Some((0, max_space - used_space, new_indent))
1957     } else {
1958         // Whoops! bankrupt.
1959         None
1960     }
1961 }
1962
1963 fn newline_for_brace(config: &Config, where_clause: &ast::WhereClause) -> bool {
1964     match config.fn_brace_style() {
1965         BraceStyle::AlwaysNextLine => true,
1966         BraceStyle::SameLineWhere if !where_clause.predicates.is_empty() => true,
1967         _ => false,
1968     }
1969 }
1970
1971 fn rewrite_generics(context: &RewriteContext,
1972                     generics: &ast::Generics,
1973                     shape: Shape,
1974                     span: Span)
1975                     -> Option<String> {
1976     // FIXME: convert bounds to where clauses where they get too big or if
1977     // there is a where clause at all.
1978     let lifetimes: &[_] = &generics.lifetimes;
1979     let tys: &[_] = &generics.ty_params;
1980     if lifetimes.is_empty() && tys.is_empty() {
1981         return Some(String::new());
1982     }
1983
1984     let offset = match context.config.generics_indent() {
1985         IndentStyle::Block => shape.indent.block_only().block_indent(context.config),
1986         // 1 = <
1987         IndentStyle::Visual => shape.indent + 1,
1988     };
1989
1990     let h_budget = try_opt!(shape.width.checked_sub(2));
1991     // FIXME: might need to insert a newline if the generics are really long.
1992
1993     // Strings for the generics.
1994     let lt_strs = lifetimes
1995         .iter()
1996         .map(|lt| lt.rewrite(context, Shape::legacy(h_budget, offset)));
1997     let ty_strs = tys.iter()
1998         .map(|ty_param| ty_param.rewrite(context, Shape::legacy(h_budget, offset)));
1999
2000     // Extract comments between generics.
2001     let lt_spans = lifetimes.iter().map(|l| {
2002                                             let hi = if l.bounds.is_empty() {
2003                                                 l.lifetime.span.hi
2004                                             } else {
2005                                                 l.bounds[l.bounds.len() - 1].span.hi
2006                                             };
2007                                             mk_sp(l.lifetime.span.lo, hi)
2008                                         });
2009     let ty_spans = tys.iter().map(span_for_ty_param);
2010
2011     let items = itemize_list(context.codemap,
2012                              lt_spans.chain(ty_spans).zip(lt_strs.chain(ty_strs)),
2013                              ">",
2014                              |&(sp, _)| sp.lo,
2015                              |&(sp, _)| sp.hi,
2016                              // FIXME: don't clone
2017                              |&(_, ref str)| str.clone(),
2018                              context.codemap.span_after(span, "<"),
2019                              span.hi);
2020     let list_str =
2021         try_opt!(format_item_list(items, Shape::legacy(h_budget, offset), context.config));
2022
2023     let result = if context.config.generics_indent() != IndentStyle::Visual &&
2024                     list_str.contains('\n') {
2025         format!("<\n{}{}\n{}>",
2026                 offset.to_string(context.config),
2027                 list_str,
2028                 shape.indent.block_only().to_string(context.config))
2029     } else if context.config.spaces_within_angle_brackets() {
2030         format!("< {} >", list_str)
2031     } else {
2032         format!("<{}>", list_str)
2033     };
2034     Some(result)
2035 }
2036
2037 fn rewrite_trait_bounds(context: &RewriteContext,
2038                         type_param_bounds: &ast::TyParamBounds,
2039                         shape: Shape)
2040                         -> Option<String> {
2041     let bounds: &[_] = type_param_bounds;
2042
2043     if bounds.is_empty() {
2044         return Some(String::new());
2045     }
2046     let joiner = match context.config.type_punctuation_density() {
2047         TypeDensity::Compressed => "+",
2048         TypeDensity::Wide => " + ",
2049     };
2050     let bound_str = try_opt!(bounds
2051                                  .iter()
2052                                  .map(|ty_bound| ty_bound.rewrite(&context, shape))
2053                                  .collect::<Option<Vec<_>>>())
2054         .join(joiner);
2055
2056     let mut result = String::new();
2057     result.push_str(": ");
2058     result.push_str(&bound_str);
2059     Some(result)
2060 }
2061
2062 fn rewrite_where_clause_rfc_style(context: &RewriteContext,
2063                                   where_clause: &ast::WhereClause,
2064                                   shape: Shape,
2065                                   terminator: &str,
2066                                   suppress_comma: bool,
2067                                   // where clause can be kept on the current line.
2068                                   snuggle: bool,
2069                                   span_end: Option<BytePos>)
2070                                   -> Option<String> {
2071     let block_shape = shape.block();
2072
2073     let starting_newline = if snuggle {
2074         " ".to_owned()
2075     } else {
2076         "\n".to_owned() + &block_shape.indent.to_string(context.config)
2077     };
2078
2079     let clause_shape = block_shape.block_indent(context.config.tab_spaces());
2080     // each clause on one line, trailing comma (except if suppress_comma)
2081     let span_start = span_for_where_pred(&where_clause.predicates[0]).lo;
2082     // If we don't have the start of the next span, then use the end of the
2083     // predicates, but that means we miss comments.
2084     let len = where_clause.predicates.len();
2085     let end_of_preds = span_for_where_pred(&where_clause.predicates[len - 1]).hi;
2086     let span_end = span_end.unwrap_or(end_of_preds);
2087     let items = itemize_list(context.codemap,
2088                              where_clause.predicates.iter(),
2089                              terminator,
2090                              |pred| span_for_where_pred(pred).lo,
2091                              |pred| span_for_where_pred(pred).hi,
2092                              |pred| pred.rewrite(context, clause_shape),
2093                              span_start,
2094                              span_end);
2095     let comma_tactic = if suppress_comma {
2096         SeparatorTactic::Never
2097     } else {
2098         SeparatorTactic::Always
2099     };
2100
2101     let fmt = ListFormatting {
2102         tactic: DefinitiveListTactic::Vertical,
2103         separator: ",",
2104         trailing_separator: comma_tactic,
2105         shape: clause_shape,
2106         ends_with_newline: true,
2107         config: context.config,
2108     };
2109     let preds_str = try_opt!(write_list(items, &fmt));
2110
2111     Some(format!("{}where\n{}{}",
2112                  starting_newline,
2113                  clause_shape.indent.to_string(context.config),
2114                  preds_str))
2115 }
2116
2117 fn rewrite_where_clause(context: &RewriteContext,
2118                         where_clause: &ast::WhereClause,
2119                         brace_style: BraceStyle,
2120                         shape: Shape,
2121                         density: Density,
2122                         terminator: &str,
2123                         suppress_comma: bool,
2124                         snuggle: bool,
2125                         span_end: Option<BytePos>)
2126                         -> Option<String> {
2127     if where_clause.predicates.is_empty() {
2128         return Some(String::new());
2129     }
2130
2131     if context.config.where_style() == Style::Rfc {
2132         return rewrite_where_clause_rfc_style(context,
2133                                               where_clause,
2134                                               shape,
2135                                               terminator,
2136                                               suppress_comma,
2137                                               snuggle,
2138                                               span_end);
2139     }
2140
2141     let extra_indent = Indent::new(context.config.tab_spaces(), 0);
2142
2143     let offset = match context.config.where_pred_indent() {
2144         IndentStyle::Block => shape.indent + extra_indent.block_indent(context.config),
2145         // 6 = "where ".len()
2146         IndentStyle::Visual => shape.indent + extra_indent + 6,
2147     };
2148     // FIXME: if where_pred_indent != Visual, then the budgets below might
2149     // be out by a char or two.
2150
2151     let budget = context.config.max_width() - offset.width();
2152     let span_start = span_for_where_pred(&where_clause.predicates[0]).lo;
2153     // If we don't have the start of the next span, then use the end of the
2154     // predicates, but that means we miss comments.
2155     let len = where_clause.predicates.len();
2156     let end_of_preds = span_for_where_pred(&where_clause.predicates[len - 1]).hi;
2157     let span_end = span_end.unwrap_or(end_of_preds);
2158     let items = itemize_list(context.codemap,
2159                              where_clause.predicates.iter(),
2160                              terminator,
2161                              |pred| span_for_where_pred(pred).lo,
2162                              |pred| span_for_where_pred(pred).hi,
2163                              |pred| pred.rewrite(context, Shape::legacy(budget, offset)),
2164                              span_start,
2165                              span_end);
2166     let item_vec = items.collect::<Vec<_>>();
2167     // FIXME: we don't need to collect here if the where_layout isn't
2168     // HorizontalVertical.
2169     let tactic = definitive_tactic(&item_vec, context.config.where_layout(), budget);
2170
2171     let mut comma_tactic = context.config.trailing_comma();
2172     // Kind of a hack because we don't usually have trailing commas in where clauses.
2173     if comma_tactic == SeparatorTactic::Vertical || suppress_comma {
2174         comma_tactic = SeparatorTactic::Never;
2175     }
2176
2177     let fmt = ListFormatting {
2178         tactic: tactic,
2179         separator: ",",
2180         trailing_separator: comma_tactic,
2181         shape: Shape::legacy(budget, offset),
2182         ends_with_newline: true,
2183         config: context.config,
2184     };
2185     let preds_str = try_opt!(write_list(&item_vec, &fmt));
2186
2187     let end_length = if terminator == "{" {
2188         // If the brace is on the next line we don't need to count it otherwise it needs two
2189         // characters " {"
2190         match brace_style {
2191             BraceStyle::AlwaysNextLine |
2192             BraceStyle::SameLineWhere => 0,
2193             BraceStyle::PreferSameLine => 2,
2194         }
2195     } else if terminator == "=" {
2196         2
2197     } else {
2198         terminator.len()
2199     };
2200     if density == Density::Tall || preds_str.contains('\n') ||
2201        shape.indent.width() + " where ".len() + preds_str.len() + end_length > shape.width {
2202         Some(format!("\n{}where {}",
2203                      (shape.indent + extra_indent).to_string(context.config),
2204                      preds_str))
2205     } else {
2206         Some(format!(" where {}", preds_str))
2207     }
2208 }
2209
2210 fn format_header(item_name: &str, ident: ast::Ident, vis: &ast::Visibility) -> String {
2211     format!("{}{}{}", format_visibility(vis), item_name, ident)
2212 }
2213
2214 fn format_generics(context: &RewriteContext,
2215                    generics: &ast::Generics,
2216                    opener: &str,
2217                    terminator: &str,
2218                    brace_style: BraceStyle,
2219                    force_same_line_brace: bool,
2220                    offset: Indent,
2221                    span: Span)
2222                    -> Option<String> {
2223     let shape = Shape::indented(offset, context.config);
2224     let mut result = try_opt!(rewrite_generics(context, generics, shape, span));
2225
2226     if !generics.where_clause.predicates.is_empty() || result.contains('\n') {
2227         let budget = try_opt!(context
2228                                   .config
2229                                   .max_width()
2230                                   .checked_sub(last_line_width(&result)));
2231         let where_clause_str =
2232             try_opt!(rewrite_where_clause(context,
2233                                           &generics.where_clause,
2234                                           brace_style,
2235                                           Shape::legacy(budget, offset.block_only()),
2236                                           Density::Tall,
2237                                           terminator,
2238                                           false,
2239                                           trimmed_last_line_width(&result) == 1,
2240                                           Some(span.hi)));
2241         result.push_str(&where_clause_str);
2242         let same_line_brace = force_same_line_brace ||
2243                               (generics.where_clause.predicates.is_empty() &&
2244                                trimmed_last_line_width(&result) == 1);
2245         if !same_line_brace &&
2246            (brace_style == BraceStyle::SameLineWhere || brace_style == BraceStyle::AlwaysNextLine) {
2247             result.push('\n');
2248             result.push_str(&offset.block_only().to_string(context.config));
2249         } else {
2250             result.push(' ');
2251         }
2252         result.push_str(opener);
2253     } else {
2254         if force_same_line_brace || trimmed_last_line_width(&result) == 1 ||
2255            brace_style != BraceStyle::AlwaysNextLine {
2256             result.push(' ');
2257         } else {
2258             result.push('\n');
2259             result.push_str(&offset.block_only().to_string(context.config));
2260         }
2261         result.push_str(opener);
2262     }
2263
2264     Some(result)
2265 }