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 std::cmp::min;
  14
  15 use syntax::{abi, ast, ptr, symbol};
  16 use syntax::ast::ImplItem;
  17 use syntax::codemap::{BytePos, Span};
  18
  19 use {Indent, Shape, Spanned};
  20 use codemap::{LineRangeUtils, SpanUtils};
  21 use comment::{contains_comment, recover_comment_removed, rewrite_comment, FindUncommented};
  22 use config::{BraceStyle, Config, Density, IndentStyle, ReturnIndent, Style};
  23 use expr::{format_expr, is_empty_block, is_simple_block_stmt, rewrite_assign_rhs,
  24            rewrite_call_inner, ExprType};
  25 use lists::{definitive_tactic, itemize_list, write_list, DefinitiveListTactic, ListFormatting,
  26             ListItem, ListTactic, Separator, SeparatorTactic};
  27 use rewrite::{Rewrite, RewriteContext};
  28 use types::join_bounds;
  29 use utils::{colon_spaces, contains_skip, end_typaram, format_defaultness, format_mutability,
  30             format_unsafety, format_visibility, last_line_width, mk_sp, semicolon_for_expr,
  31             stmt_expr, trim_newlines, trimmed_last_line_width, wrap_str};
  32 use vertical::rewrite_with_alignment;
  33 use visitor::FmtVisitor;
  34
  35 fn type_annotation_separator(config: &Config) -> &str {
  36     colon_spaces(
  37         config.space_before_type_annotation(),
  38         config.space_after_type_annotation_colon(),
  39     )
  40 }
  41
  42
  43 // Statements of the form
  44 // let pat: ty = init;
  45 impl Rewrite for ast::Local {
  46     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
  47         debug!(
  48             "Local::rewrite {:?} {} {:?}",
  49             self,
  50             shape.width,
  51             shape.indent
  52         );
  53
  54         skip_out_of_file_lines_range!(context, self.span);
  55
  56         let mut result = "let ".to_owned();
  57
  58         // 4 = "let ".len()
  59         let pat_shape = try_opt!(shape.offset_left(4));
  60         // 1 = ;
  61         let pat_shape = try_opt!(pat_shape.sub_width(1));
  62         let pat_str = try_opt!(self.pat.rewrite(&context, pat_shape));
  63         result.push_str(&pat_str);
  64
  65         // String that is placed within the assignment pattern and expression.
  66         let infix = {
  67             let mut infix = String::new();
  68
  69             if let Some(ref ty) = self.ty {
  70                 let separator = type_annotation_separator(context.config);
  71                 let indent = shape.indent + last_line_width(&result) + separator.len();
  72                 // 1 = ;
  73                 let budget = try_opt!(shape.width.checked_sub(indent.width() + 1));
  74                 let rewrite = try_opt!(ty.rewrite(context, Shape::legacy(budget, indent)));
  75
  76                 infix.push_str(separator);
  77                 infix.push_str(&rewrite);
  78             }
  79
  80             if self.init.is_some() {
  81                 infix.push_str(" =");
  82             }
  83
  84             infix
  85         };
  86
  87         result.push_str(&infix);
  88
  89         if let Some(ref ex) = self.init {
  90             // 1 = trailing semicolon;
  91             let nested_shape = try_opt!(shape.sub_width(1));
  92
  93             result = try_opt!(rewrite_assign_rhs(&context, result, ex, nested_shape));
  94         }
  95
  96         result.push(';');
  97         Some(result)
  98     }
  99 }
 100
 101 // TODO convert to using rewrite style rather than visitor
 102 // TODO format modules in this style
 103 #[allow(dead_code)]
 104 struct Item<'a> {
 105     keyword: &'static str,
 106     abi: String,
 107     vis: Option<&'a ast::Visibility>,
 108     body: Vec<BodyElement<'a>>,
 109     span: Span,
 110 }
 111
 112 impl<'a> Item<'a> {
 113     fn from_foreign_mod(fm: &'a ast::ForeignMod, span: Span, config: &Config) -> Item<'a> {
 114         let abi = if fm.abi == abi::Abi::C && !config.force_explicit_abi() {
 115             "extern".into()
 116         } else {
 117             format!("extern {}", fm.abi)
 118         };
 119         Item {
 120             keyword: "",
 121             abi: abi,
 122             vis: None,
 123             body: fm.items
 124                 .iter()
 125                 .map(|i| BodyElement::ForeignItem(i))
 126                 .collect(),
 127             span: span,
 128         }
 129     }
 130 }
 131
 132 enum BodyElement<'a> {
 133     // Stmt(&'a ast::Stmt),
 134     // Field(&'a ast::Field),
 135     // Variant(&'a ast::Variant),
 136     // Item(&'a ast::Item),
 137     ForeignItem(&'a ast::ForeignItem),
 138 }
 139
 140 impl<'a> FmtVisitor<'a> {
 141     fn format_item(&mut self, item: Item) {
 142         self.buffer.push_str(&item.abi);
 143         self.buffer.push_str(" ");
 144
 145         let snippet = self.snippet(item.span);
 146         let brace_pos = snippet.find_uncommented("{").unwrap();
 147
 148         self.buffer.push_str("{");
 149         if !item.body.is_empty() || contains_comment(&snippet[brace_pos..]) {
 150             // FIXME: this skips comments between the extern keyword and the opening
 151             // brace.
 152             self.last_pos = item.span.lo + BytePos(brace_pos as u32 + 1);
 153             self.block_indent = self.block_indent.block_indent(self.config);
 154
 155             if item.body.is_empty() {
 156                 self.format_missing_no_indent(item.span.hi - BytePos(1));
 157                 self.block_indent = self.block_indent.block_unindent(self.config);
 158
 159                 self.buffer
 160                     .push_str(&self.block_indent.to_string(self.config));
 161             } else {
 162                 for item in &item.body {
 163                     self.format_body_element(item);
 164                 }
 165
 166                 self.block_indent = self.block_indent.block_unindent(self.config);
 167                 self.format_missing_with_indent(item.span.hi - BytePos(1));
 168             }
 169         }
 170
 171         self.buffer.push_str("}");
 172         self.last_pos = item.span.hi;
 173     }
 174
 175     fn format_body_element(&mut self, element: &BodyElement) {
 176         match *element {
 177             BodyElement::ForeignItem(ref item) => self.format_foreign_item(item),
 178         }
 179     }
 180
 181     pub fn format_foreign_mod(&mut self, fm: &ast::ForeignMod, span: Span) {
 182         let item = Item::from_foreign_mod(fm, span, self.config);
 183         self.format_item(item);
 184     }
 185
 186     fn format_foreign_item(&mut self, item: &ast::ForeignItem) {
 187         self.format_missing_with_indent(item.span.lo);
 188         // Drop semicolon or it will be interpreted as comment.
 189         // FIXME: this may be a faulty span from libsyntax.
 190         let span = mk_sp(item.span.lo, item.span.hi - BytePos(1));
 191
 192         match item.node {
 193             ast::ForeignItemKind::Fn(ref fn_decl, ref generics) => {
 194                 let indent = self.block_indent;
 195                 let rewrite = rewrite_fn_base(
 196                     &self.get_context(),
 197                     indent,
 198                     item.ident,
 199                     fn_decl,
 200                     generics,
 201                     ast::Unsafety::Normal,
 202                     ast::Constness::NotConst,
 203                     ast::Defaultness::Final,
 204                     // These are not actually rust functions,
 205                     // but we format them as such.
 206                     abi::Abi::Rust,
 207                     &item.vis,
 208                     span,
 209                     false,
 210                     false,
 211                     false,
 212                 );
 213
 214                 match rewrite {
 215                     Some((new_fn, _)) => {
 216                         self.buffer.push_str(&new_fn);
 217                         self.buffer.push_str(";");
 218                     }
 219                     None => self.format_missing(item.span.hi),
 220                 }
 221             }
 222             ast::ForeignItemKind::Static(ref ty, is_mutable) => {
 223                 // FIXME(#21): we're dropping potential comments in between the
 224                 // function keywords here.
 225                 let vis = format_visibility(&item.vis);
 226                 let mut_str = if is_mutable { "mut " } else { "" };
 227                 let prefix = format!("{}static {}{}: ", vis, mut_str, item.ident);
 228                 let offset = self.block_indent + prefix.len();
 229                 // 1 = ;
 230                 let shape = Shape::indented(offset, self.config).sub_width(1).unwrap();
 231                 let rewrite = ty.rewrite(&self.get_context(), shape);
 232
 233                 match rewrite {
 234                     Some(result) => {
 235                         self.buffer.push_str(&prefix);
 236                         self.buffer.push_str(&result);
 237                         self.buffer.push_str(";");
 238                     }
 239                     None => self.format_missing(item.span.hi),
 240                 }
 241             }
 242         }
 243
 244         self.last_pos = item.span.hi;
 245     }
 246
 247     pub fn rewrite_fn(
 248         &mut self,
 249         indent: Indent,
 250         ident: ast::Ident,
 251         fd: &ast::FnDecl,
 252         generics: &ast::Generics,
 253         unsafety: ast::Unsafety,
 254         constness: ast::Constness,
 255         defaultness: ast::Defaultness,
 256         abi: abi::Abi,
 257         vis: &ast::Visibility,
 258         span: Span,
 259         block: &ast::Block,
 260     ) -> Option<String> {
 261         let mut newline_brace = newline_for_brace(self.config, &generics.where_clause);
 262         let context = self.get_context();
 263
 264         let block_snippet = self.snippet(mk_sp(block.span.lo, block.span.hi));
 265         let has_body = !block_snippet[1..block_snippet.len() - 1].trim().is_empty() ||
 266             !context.config.fn_empty_single_line();
 267
 268         let (mut result, force_newline_brace) = try_opt!(rewrite_fn_base(
 269             &context,
 270             indent,
 271             ident,
 272             fd,
 273             generics,
 274             unsafety,
 275             constness,
 276             defaultness,
 277             abi,
 278             vis,
 279             span,
 280             newline_brace,
 281             has_body,
 282             true,
 283         ));
 284
 285         if force_newline_brace {
 286             newline_brace = true;
 287         } else if self.config.fn_brace_style() != BraceStyle::AlwaysNextLine &&
 288             !result.contains('\n')
 289         {
 290             newline_brace = false;
 291         }
 292
 293         // Prepare for the function body by possibly adding a newline and
 294         // indent.
 295         // FIXME we'll miss anything between the end of the signature and the
 296         // start of the body, but we need more spans from the compiler to solve
 297         // this.
 298         if newline_brace {
 299             result.push('\n');
 300             result.push_str(&indent.to_string(self.config));
 301         } else {
 302             result.push(' ');
 303         }
 304
 305         self.single_line_fn(&result, block).or_else(|| Some(result))
 306     }
 307
 308     pub fn rewrite_required_fn(
 309         &mut self,
 310         indent: Indent,
 311         ident: ast::Ident,
 312         sig: &ast::MethodSig,
 313         span: Span,
 314     ) -> Option<String> {
 315         // Drop semicolon or it will be interpreted as comment.
 316         let span = mk_sp(span.lo, span.hi - BytePos(1));
 317         let context = self.get_context();
 318
 319         let (mut result, _) = try_opt!(rewrite_fn_base(
 320             &context,
 321             indent,
 322             ident,
 323             &sig.decl,
 324             &sig.generics,
 325             sig.unsafety,
 326             sig.constness.node,
 327             ast::Defaultness::Final,
 328             sig.abi,
 329             &ast::Visibility::Inherited,
 330             span,
 331             false,
 332             false,
 333             false,
 334         ));
 335
 336         // Re-attach semicolon
 337         result.push(';');
 338
 339         Some(result)
 340     }
 341
 342     fn single_line_fn(&self, fn_str: &str, block: &ast::Block) -> Option<String> {
 343         if fn_str.contains('\n') {
 344             return None;
 345         }
 346
 347         let codemap = self.get_context().codemap;
 348
 349         if self.config.fn_empty_single_line() && is_empty_block(block, codemap) &&
 350             self.block_indent.width() + fn_str.len() + 2 <= self.config.max_width()
 351         {
 352             return Some(format!("{}{{}}", fn_str));
 353         }
 354
 355         if self.config.fn_single_line() && is_simple_block_stmt(block, codemap) {
 356             let rewrite = {
 357                 if let Some(ref stmt) = block.stmts.first() {
 358                     match stmt_expr(stmt) {
 359                         Some(e) => {
 360                             let suffix = if semicolon_for_expr(&self.get_context(), e) {
 361                                 ";"
 362                             } else {
 363                                 ""
 364                             };
 365
 366                             format_expr(
 367                                 &e,
 368                                 ExprType::Statement,
 369                                 &self.get_context(),
 370                                 Shape::indented(self.block_indent, self.config),
 371                             ).map(|s| s + suffix)
 372                                 .or_else(|| Some(self.snippet(e.span)))
 373                         }
 374                         None => stmt.rewrite(
 375                             &self.get_context(),
 376                             Shape::indented(self.block_indent, self.config),
 377                         ),
 378                     }
 379                 } else {
 380                     None
 381                 }
 382             };
 383
 384             if let Some(res) = rewrite {
 385                 let width = self.block_indent.width() + fn_str.len() + res.len() + 4;
 386                 if !res.contains('\n') && width <= self.config.max_width() {
 387                     return Some(format!("{}{{ {} }}", fn_str, res));
 388                 }
 389             }
 390         }
 391
 392         None
 393     }
 394
 395     pub fn visit_enum(
 396         &mut self,
 397         ident: ast::Ident,
 398         vis: &ast::Visibility,
 399         enum_def: &ast::EnumDef,
 400         generics: &ast::Generics,
 401         span: Span,
 402     ) {
 403         let enum_header = format_header("enum ", ident, vis);
 404         self.buffer.push_str(&enum_header);
 405
 406         let enum_snippet = self.snippet(span);
 407         let brace_pos = enum_snippet.find_uncommented("{").unwrap();
 408         let body_start = span.lo + BytePos(brace_pos as u32 + 1);
 409         let generics_str = format_generics(
 410             &self.get_context(),
 411             generics,
 412             "{",
 413             "{",
 414             self.config.item_brace_style(),
 415             enum_def.variants.is_empty(),
 416             self.block_indent,
 417             mk_sp(span.lo, body_start),
 418             last_line_width(&enum_header),
 419         ).unwrap();
 420         self.buffer.push_str(&generics_str);
 421
 422         self.last_pos = body_start;
 423
 424         self.block_indent = self.block_indent.block_indent(self.config);
 425         let variant_list = self.format_variant_list(enum_def, body_start, span.hi - BytePos(1));
 426         match variant_list {
 427             Some(ref body_str) => self.buffer.push_str(body_str),
 428             None => if contains_comment(&enum_snippet[brace_pos..]) {
 429                 self.format_missing_no_indent(span.hi - BytePos(1))
 430             } else {
 431                 self.format_missing(span.hi - BytePos(1))
 432             },
 433         }
 434         self.block_indent = self.block_indent.block_unindent(self.config);
 435
 436         if variant_list.is_some() || contains_comment(&enum_snippet[brace_pos..]) {
 437             self.buffer
 438                 .push_str(&self.block_indent.to_string(self.config));
 439         }
 440         self.buffer.push_str("}");
 441         self.last_pos = span.hi;
 442     }
 443
 444     // Format the body of an enum definition
 445     fn format_variant_list(
 446         &self,
 447         enum_def: &ast::EnumDef,
 448         body_lo: BytePos,
 449         body_hi: BytePos,
 450     ) -> Option<String> {
 451         if enum_def.variants.is_empty() {
 452             return None;
 453         }
 454         let mut result = String::with_capacity(1024);
 455         result.push('\n');
 456         let indentation = self.block_indent.to_string(self.config);
 457         result.push_str(&indentation);
 458
 459         let items = itemize_list(
 460             self.codemap,
 461             enum_def.variants.iter(),
 462             "}",
 463             |f| if !f.node.attrs.is_empty() {
 464                 f.node.attrs[0].span.lo
 465             } else {
 466                 f.span.lo
 467             },
 468             |f| f.span.hi,
 469             |f| self.format_variant(f),
 470             body_lo,
 471             body_hi,
 472         );
 473
 474         let shape = Shape::indented(self.block_indent, self.config)
 475             .sub_width(2)
 476             .unwrap();
 477         let fmt = ListFormatting {
 478             tactic: DefinitiveListTactic::Vertical,
 479             separator: ",",
 480             trailing_separator: self.config.trailing_comma(),
 481             shape: shape,
 482             ends_with_newline: true,
 483             preserve_newline: true,
 484             config: self.config,
 485         };
 486
 487         let list = try_opt!(write_list(&items.collect::<Vec<_>>(), &fmt));
 488         result.push_str(&list);
 489         result.push('\n');
 490         Some(result)
 491     }
 492
 493     // Variant of an enum.
 494     fn format_variant(&self, field: &ast::Variant) -> Option<String> {
 495         if contains_skip(&field.node.attrs) {
 496             let lo = field.node.attrs[0].span.lo;
 497             let span = mk_sp(lo, field.span.hi);
 498             return Some(self.snippet(span));
 499         }
 500
 501         let context = self.get_context();
 502         let indent = self.block_indent;
 503         let mut result = try_opt!(
 504             field
 505                 .node
 506                 .attrs
 507                 .rewrite(&context, Shape::indented(indent, self.config))
 508         );
 509         if !result.is_empty() {
 510             let shape = Shape {
 511                 width: context.config.max_width(),
 512                 indent: self.block_indent,
 513                 offset: self.block_indent.alignment,
 514             };
 515             let missing_comment = rewrite_missing_comment_on_field(
 516                 &context,
 517                 shape,
 518                 field.node.attrs[field.node.attrs.len() - 1].span.hi,
 519                 field.span.lo,
 520                 &mut result,
 521             ).unwrap_or(String::new());
 522             result.push_str(&missing_comment);
 523         }
 524
 525         let variant_body = match field.node.data {
 526             ast::VariantData::Tuple(..) | ast::VariantData::Struct(..) => {
 527                 // FIXME: Should limit the width, as we have a trailing comma
 528                 format_struct(
 529                     &context,
 530                     "",
 531                     field.node.name,
 532                     &ast::Visibility::Inherited,
 533                     &field.node.data,
 534                     None,
 535                     field.span,
 536                     indent,
 537                     Some(self.config.struct_variant_width()),
 538                 )
 539             }
 540             ast::VariantData::Unit(..) => {
 541                 let tag = if let Some(ref expr) = field.node.disr_expr {
 542                     format!("{} = {}", field.node.name, self.snippet(expr.span))
 543                 } else {
 544                     field.node.name.to_string()
 545                 };
 546
 547                 wrap_str(
 548                     tag,
 549                     self.config.max_width(),
 550                     Shape::indented(indent, self.config),
 551                 )
 552             }
 553         };
 554
 555         if let Some(variant_str) = variant_body {
 556             result.push_str(&variant_str);
 557             Some(result)
 558         } else {
 559             None
 560         }
 561     }
 562 }
 563
 564 pub fn format_impl(
 565     context: &RewriteContext,
 566     item: &ast::Item,
 567     offset: Indent,
 568     where_span_end: Option<BytePos>,
 569 ) -> Option<String> {
 570     if let ast::ItemKind::Impl(_, _, _, ref generics, _, ref self_ty, ref items) = item.node {
 571         let mut result = String::new();
 572         let ref_and_type = try_opt!(format_impl_ref_and_type(context, item, offset));
 573         result.push_str(&ref_and_type);
 574
 575         let where_budget = if result.contains('\n') {
 576             context.config.max_width()
 577         } else {
 578             context
 579                 .config
 580                 .max_width()
 581                 .checked_sub(last_line_width(&result))
 582                 .unwrap_or(0)
 583         };
 584         let where_clause_str = try_opt!(rewrite_where_clause(
 585             context,
 586             &generics.where_clause,
 587             context.config.item_brace_style(),
 588             Shape::legacy(where_budget, offset.block_only()),
 589             context.config.where_density(),
 590             "{",
 591             false,
 592             last_line_width(&ref_and_type) == 1,
 593             where_span_end,
 594             item.span,
 595             self_ty.span.hi,
 596         ));
 597
 598         if try_opt!(is_impl_single_line(
 599             context,
 600             &items,
 601             &result,
 602             &where_clause_str,
 603             &item,
 604         )) {
 605             result.push_str(&where_clause_str);
 606             if where_clause_str.contains('\n') {
 607                 let white_space = offset.to_string(context.config);
 608                 result.push_str(&format!("\n{}{{\n{}}}", &white_space, &white_space));
 609             } else {
 610                 result.push_str(" {}");
 611             }
 612             return Some(result);
 613         }
 614
 615         if !where_clause_str.is_empty() && !where_clause_str.contains('\n') {
 616             result.push('\n');
 617             let width = offset.block_indent + context.config.tab_spaces() - 1;
 618             let where_indent = Indent::new(0, width);
 619             result.push_str(&where_indent.to_string(context.config));
 620         }
 621         result.push_str(&where_clause_str);
 622
 623         match context.config.item_brace_style() {
 624             BraceStyle::AlwaysNextLine => {
 625                 result.push('\n');
 626                 result.push_str(&offset.to_string(context.config));
 627             }
 628             BraceStyle::PreferSameLine => result.push(' '),
 629             BraceStyle::SameLineWhere => if !where_clause_str.is_empty() {
 630                 result.push('\n');
 631                 result.push_str(&offset.to_string(context.config));
 632             } else {
 633                 result.push(' ');
 634             },
 635         }
 636
 637         result.push('{');
 638
 639         let snippet = context.snippet(item.span);
 640         let open_pos = try_opt!(snippet.find_uncommented("{")) + 1;
 641
 642         if !items.is_empty() || contains_comment(&snippet[open_pos..]) {
 643             let mut visitor = FmtVisitor::from_codemap(context.parse_session, context.config);
 644             visitor.block_indent = offset.block_only().block_indent(context.config);
 645             visitor.last_pos = item.span.lo + BytePos(open_pos as u32);
 646
 647             visitor.visit_attrs(&item.attrs, ast::AttrStyle::Inner);
 648             for item in items {
 649                 visitor.visit_impl_item(item);
 650             }
 651
 652             visitor.format_missing(item.span.hi - BytePos(1));
 653
 654             let inner_indent_str = visitor.block_indent.to_string(context.config);
 655             let outer_indent_str = offset.block_only().to_string(context.config);
 656
 657             result.push('\n');
 658             result.push_str(&inner_indent_str);
 659             result.push_str(trim_newlines(visitor.buffer.to_string().trim()));
 660             result.push('\n');
 661             result.push_str(&outer_indent_str);
 662         }
 663
 664         if result.chars().last().unwrap() == '{' {
 665             result.push('\n');
 666             result.push_str(&offset.to_string(context.config));
 667         }
 668         result.push('}');
 669
 670         Some(result)
 671     } else {
 672         unreachable!();
 673     }
 674 }
 675
 676 fn is_impl_single_line(
 677     context: &RewriteContext,
 678     items: &[ImplItem],
 679     result: &str,
 680     where_clause_str: &str,
 681     item: &ast::Item,
 682 ) -> Option<bool> {
 683     let snippet = context.snippet(item.span);
 684     let open_pos = try_opt!(snippet.find_uncommented("{")) + 1;
 685
 686     Some(
 687         context.config.impl_empty_single_line() && items.is_empty() &&
 688             result.len() + where_clause_str.len() <= context.config.max_width() &&
 689             !contains_comment(&snippet[open_pos..]),
 690     )
 691 }
 692
 693 fn format_impl_ref_and_type(
 694     context: &RewriteContext,
 695     item: &ast::Item,
 696     offset: Indent,
 697 ) -> Option<String> {
 698     if let ast::ItemKind::Impl(
 699         unsafety,
 700         polarity,
 701         defaultness,
 702         ref generics,
 703         ref trait_ref,
 704         ref self_ty,
 705         _,
 706     ) = item.node
 707     {
 708         let mut result = String::new();
 709
 710         result.push_str(&format_visibility(&item.vis));
 711         result.push_str(&format_defaultness(defaultness));
 712         result.push_str(format_unsafety(unsafety));
 713         result.push_str("impl");
 714
 715         let lo = context.codemap.span_after(item.span, "impl");
 716         let hi = match *trait_ref {
 717             Some(ref tr) => tr.path.span.lo,
 718             None => self_ty.span.lo,
 719         };
 720         let shape = try_opt!(generics_shape_from_config(
 721             context.config,
 722             Shape::indented(offset + last_line_width(&result), context.config),
 723             0,
 724         ));
 725         let one_line_budget = try_opt!(shape.width.checked_sub(last_line_width(&result) + 2));
 726         let generics_str = try_opt!(rewrite_generics_inner(
 727             context,
 728             generics,
 729             shape,
 730             one_line_budget,
 731             mk_sp(lo, hi),
 732         ));
 733
 734         let polarity_str = if polarity == ast::ImplPolarity::Negative {
 735             "!"
 736         } else {
 737             ""
 738         };
 739
 740         if let Some(ref trait_ref) = *trait_ref {
 741             let result_len = result.len();
 742             if let Some(trait_ref_str) = rewrite_trait_ref(
 743                 context,
 744                 &trait_ref,
 745                 offset,
 746                 &generics_str,
 747                 true,
 748                 polarity_str,
 749                 result_len,
 750             ) {
 751                 result.push_str(&trait_ref_str);
 752             } else {
 753                 let generics_str = try_opt!(rewrite_generics_inner(
 754                     context,
 755                     generics,
 756                     shape,
 757                     0,
 758                     mk_sp(lo, hi),
 759                 ));
 760                 result.push_str(&try_opt!(rewrite_trait_ref(
 761                     context,
 762                     &trait_ref,
 763                     offset,
 764                     &generics_str,
 765                     false,
 766                     polarity_str,
 767                     result_len,
 768                 )));
 769             }
 770         } else {
 771             result.push_str(&generics_str);
 772         }
 773
 774         // Try to put the self type in a single line.
 775         // ` for`
 776         let trait_ref_overhead = if trait_ref.is_some() { 4 } else { 0 };
 777         let curly_brace_overhead = if generics.where_clause.predicates.is_empty() {
 778             // If there is no where clause adapt budget for type formatting to take space and curly
 779             // brace into account.
 780             match context.config.item_brace_style() {
 781                 BraceStyle::AlwaysNextLine => 0,
 782                 _ => 2,
 783             }
 784         } else {
 785             0
 786         };
 787         let used_space = last_line_width(&result) + trait_ref_overhead + curly_brace_overhead;
 788         // 1 = space before the type.
 789         let budget = context
 790             .config
 791             .max_width()
 792             .checked_sub(used_space + 1)
 793             .unwrap_or(0);
 794         if let Some(self_ty_str) = self_ty.rewrite(context, Shape::legacy(budget, offset)) {
 795             if !self_ty_str.contains('\n') {
 796                 if trait_ref.is_some() {
 797                     result.push_str(" for ");
 798                 } else {
 799                     result.push(' ');
 800                 }
 801                 result.push_str(&self_ty_str);
 802                 return Some(result);
 803             }
 804         }
 805
 806         // Couldn't fit the self type on a single line, put it on a new line.
 807         result.push('\n');
 808         // Add indentation of one additional tab.
 809         let new_line_offset = offset.block_indent(context.config);
 810         result.push_str(&new_line_offset.to_string(context.config));
 811         if trait_ref.is_some() {
 812             result.push_str("for ");
 813         }
 814         let budget = context.config.max_width() - last_line_width(&result);
 815         let type_offset = match context.config.where_style() {
 816             Style::Legacy => new_line_offset + trait_ref_overhead,
 817             Style::Rfc => new_line_offset,
 818         };
 819         result.push_str(&*try_opt!(
 820             self_ty.rewrite(context, Shape::legacy(budget, type_offset))
 821         ));
 822         Some(result)
 823     } else {
 824         unreachable!();
 825     }
 826 }
 827
 828 fn rewrite_trait_ref(
 829     context: &RewriteContext,
 830     trait_ref: &ast::TraitRef,
 831     offset: Indent,
 832     generics_str: &str,
 833     retry: bool,
 834     polarity_str: &str,
 835     result_len: usize,
 836 ) -> Option<String> {
 837     // 1 = space between generics and trait_ref
 838     let used_space = 1 + polarity_str.len() + if generics_str.contains('\n') {
 839         last_line_width(&generics_str)
 840     } else {
 841         result_len + generics_str.len()
 842     };
 843     let shape = Shape::indented(offset + used_space, context.config);
 844     if let Some(trait_ref_str) = trait_ref.rewrite(context, shape) {
 845         if !(retry && trait_ref_str.contains('\n')) {
 846             return Some(format!(
 847                 "{} {}{}",
 848                 generics_str,
 849                 polarity_str,
 850                 &trait_ref_str
 851             ));
 852         }
 853     }
 854     // We could not make enough space for trait_ref, so put it on new line.
 855     if !retry {
 856         let offset = offset.block_indent(context.config);
 857         let shape = Shape::indented(offset, context.config);
 858         let trait_ref_str = try_opt!(trait_ref.rewrite(context, shape));
 859         Some(format!(
 860             "{}\n{}{}{}",
 861             generics_str,
 862             &offset.to_string(context.config),
 863             polarity_str,
 864             &trait_ref_str
 865         ))
 866     } else {
 867         None
 868     }
 869 }
 870
 871 pub fn format_struct(
 872     context: &RewriteContext,
 873     item_name: &str,
 874     ident: ast::Ident,
 875     vis: &ast::Visibility,
 876     struct_def: &ast::VariantData,
 877     generics: Option<&ast::Generics>,
 878     span: Span,
 879     offset: Indent,
 880     one_line_width: Option<usize>,
 881 ) -> Option<String> {
 882     match *struct_def {
 883         ast::VariantData::Unit(..) => Some(format_unit_struct(item_name, ident, vis)),
 884         ast::VariantData::Tuple(ref fields, _) => format_tuple_struct(
 885             context,
 886             item_name,
 887             ident,
 888             vis,
 889             fields,
 890             generics,
 891             span,
 892             offset,
 893         ),
 894         ast::VariantData::Struct(ref fields, _) => format_struct_struct(
 895             context,
 896             item_name,
 897             ident,
 898             vis,
 899             fields,
 900             generics,
 901             span,
 902             offset,
 903             one_line_width,
 904         ),
 905     }
 906 }
 907
 908 pub fn format_trait(context: &RewriteContext, item: &ast::Item, offset: Indent) -> Option<String> {
 909     if let ast::ItemKind::Trait(unsafety, ref generics, ref type_param_bounds, ref trait_items) =
 910         item.node
 911     {
 912         let mut result = String::new();
 913         let header = format!(
 914             "{}{}trait {}",
 915             format_visibility(&item.vis),
 916             format_unsafety(unsafety),
 917             item.ident
 918         );
 919
 920         result.push_str(&header);
 921
 922         let body_lo = context.codemap.span_after(item.span, "{");
 923
 924         let shape = Shape::indented(offset + last_line_width(&result), context.config);
 925         let generics_str = try_opt!(rewrite_generics(
 926             context,
 927             generics,
 928             shape,
 929             mk_sp(item.span.lo, body_lo),
 930         ));
 931         result.push_str(&generics_str);
 932
 933         let trait_bound_str = try_opt!(rewrite_trait_bounds(
 934             context,
 935             type_param_bounds,
 936             Shape::indented(offset, context.config),
 937         ));
 938         // If the trait, generics, and trait bound cannot fit on the same line,
 939         // put the trait bounds on an indented new line
 940         if offset.width() + last_line_width(&result) + trait_bound_str.len() >
 941             context.config.comment_width()
 942         {
 943             result.push('\n');
 944             let trait_indent = offset.block_only().block_indent(context.config);
 945             result.push_str(&trait_indent.to_string(context.config));
 946         }
 947         result.push_str(&trait_bound_str);
 948
 949         let has_body = !trait_items.is_empty();
 950
 951         let where_density = if (context.config.where_density() == Density::Compressed &&
 952             (!result.contains('\n') || context.config.fn_args_layout() == IndentStyle::Block)) ||
 953             (context.config.fn_args_layout() == IndentStyle::Block && result.is_empty()) ||
 954             (context.config.where_density() == Density::CompressedIfEmpty && !has_body &&
 955                 !result.contains('\n'))
 956         {
 957             Density::Compressed
 958         } else {
 959             Density::Tall
 960         };
 961
 962         let where_budget = try_opt!(
 963             context
 964                 .config
 965                 .max_width()
 966                 .checked_sub(last_line_width(&result))
 967         );
 968         let pos_before_where = if type_param_bounds.is_empty() {
 969             if generics.where_clause.predicates.is_empty() {
 970                 // We do not use this, so it does not matter
 971                 item.span.lo
 972             } else {
 973                 let snippet = context.snippet(item.span);
 974                 let where_pos = snippet.find_uncommented("where");
 975                 item.span.lo + where_pos.map_or(BytePos(0), |p| BytePos(p as u32))
 976             }
 977         } else {
 978             type_param_bounds[type_param_bounds.len() - 1].span().hi
 979         };
 980         let where_clause_str = try_opt!(rewrite_where_clause(
 981             context,
 982             &generics.where_clause,
 983             context.config.item_brace_style(),
 984             Shape::legacy(where_budget, offset.block_only()),
 985             where_density,
 986             "{",
 987             false,
 988             trait_bound_str.is_empty() && last_line_width(&generics_str) == 1,
 989             None,
 990             item.span,
 991             pos_before_where,
 992         ));
 993         // If the where clause cannot fit on the same line,
 994         // put the where clause on a new line
 995         if !where_clause_str.contains('\n') &&
 996             last_line_width(&result) + where_clause_str.len() + offset.width() >
 997                 context.config.comment_width()
 998         {
 999             result.push('\n');
1000             let width = offset.block_indent + context.config.tab_spaces() - 1;
1001             let where_indent = Indent::new(0, width);
1002             result.push_str(&where_indent.to_string(context.config));
1003         }
1004         result.push_str(&where_clause_str);
1005
1006         match context.config.item_brace_style() {
1007             BraceStyle::AlwaysNextLine => {
1008                 result.push('\n');
1009                 result.push_str(&offset.to_string(context.config));
1010             }
1011             BraceStyle::PreferSameLine => result.push(' '),
1012             BraceStyle::SameLineWhere => if !where_clause_str.is_empty() &&
1013                 (!trait_items.is_empty() || result.contains('\n'))
1014             {
1015                 result.push('\n');
1016                 result.push_str(&offset.to_string(context.config));
1017             } else {
1018                 result.push(' ');
1019             },
1020         }
1021         result.push('{');
1022
1023         let snippet = context.snippet(item.span);
1024         let open_pos = try_opt!(snippet.find_uncommented("{")) + 1;
1025
1026         if !trait_items.is_empty() || contains_comment(&snippet[open_pos..]) {
1027             let mut visitor = FmtVisitor::from_codemap(context.parse_session, context.config);
1028             visitor.block_indent = offset.block_only().block_indent(context.config);
1029             visitor.last_pos = item.span.lo + BytePos(open_pos as u32);
1030
1031             for item in trait_items {
1032                 visitor.visit_trait_item(item);
1033             }
1034
1035             visitor.format_missing(item.span.hi - BytePos(1));
1036
1037             let inner_indent_str = visitor.block_indent.to_string(context.config);
1038             let outer_indent_str = offset.block_only().to_string(context.config);
1039
1040             result.push('\n');
1041             result.push_str(&inner_indent_str);
1042             result.push_str(trim_newlines(visitor.buffer.to_string().trim()));
1043             result.push('\n');
1044             result.push_str(&outer_indent_str);
1045         } else if result.contains('\n') {
1046             result.push('\n');
1047         }
1048
1049         result.push('}');
1050         Some(result)
1051     } else {
1052         unreachable!();
1053     }
1054 }
1055
1056 fn format_unit_struct(item_name: &str, ident: ast::Ident, vis: &ast::Visibility) -> String {
1057     format!("{};", format_header(item_name, ident, vis))
1058 }
1059
1060 pub fn format_struct_struct(
1061     context: &RewriteContext,
1062     item_name: &str,
1063     ident: ast::Ident,
1064     vis: &ast::Visibility,
1065     fields: &[ast::StructField],
1066     generics: Option<&ast::Generics>,
1067     span: Span,
1068     offset: Indent,
1069     one_line_width: Option<usize>,
1070 ) -> Option<String> {
1071     let mut result = String::with_capacity(1024);
1072
1073     let header_str = format_header(item_name, ident, vis);
1074     result.push_str(&header_str);
1075
1076     let body_lo = context.codemap.span_after(span, "{");
1077
1078     let generics_str = match generics {
1079         Some(g) => try_opt!(format_generics(
1080             context,
1081             g,
1082             "{",
1083             "{",
1084             context.config.item_brace_style(),
1085             fields.is_empty(),
1086             offset,
1087             mk_sp(span.lo, body_lo),
1088             last_line_width(&result),
1089         )),
1090         None => {
1091             // 3 = ` {}`, 2 = ` {`.
1092             let overhead = if fields.is_empty() { 3 } else { 2 };
1093             if (context.config.item_brace_style() == BraceStyle::AlwaysNextLine &&
1094                 !fields.is_empty()) ||
1095                 context
1096                     .config
1097                     .max_width()
1098                     .checked_sub(result.len())
1099                     .unwrap_or(0) < overhead
1100             {
1101                 format!("\n{}{{", offset.block_only().to_string(context.config))
1102             } else {
1103                 " {".to_owned()
1104             }
1105         }
1106     };
1107     // 1 = `}`
1108     let overhead = if fields.is_empty() { 1 } else { 0 };
1109     let max_len = context
1110         .config
1111         .max_width()
1112         .checked_sub(offset.width())
1113         .unwrap_or(0);
1114     if !generics_str.contains('\n') && result.len() + generics_str.len() + overhead > max_len {
1115         result.push('\n');
1116         result.push_str(&offset.to_string(context.config));
1117         result.push_str(&generics_str.trim_left());
1118     } else {
1119         result.push_str(&generics_str);
1120     }
1121
1122     if fields.is_empty() {
1123         let snippet = context.snippet(mk_sp(body_lo, span.hi - BytePos(1)));
1124         if snippet.trim().is_empty() {
1125             // `struct S {}`
1126         } else if snippet.trim_right_matches(&[' ', '\t'][..]).ends_with('\n') {
1127             // fix indent
1128             result.push_str(&snippet.trim_right());
1129             result.push('\n');
1130             result.push_str(&offset.to_string(context.config));
1131         } else {
1132             result.push_str(&snippet);
1133         }
1134         result.push('}');
1135         return Some(result);
1136     }
1137
1138     // 3 = ` ` and ` }`
1139     let one_line_budget = context
1140         .config
1141         .max_width()
1142         .checked_sub(result.len() + 3 + offset.width())
1143         .unwrap_or(0);
1144     let one_line_budget =
1145         one_line_width.map_or(0, |one_line_width| min(one_line_width, one_line_budget));
1146
1147     let items_str = try_opt!(rewrite_with_alignment(
1148         fields,
1149         context,
1150         Shape::indented(offset, context.config),
1151         mk_sp(body_lo, span.hi),
1152         one_line_budget,
1153     ));
1154
1155     if !items_str.contains('\n') && !result.contains('\n') && items_str.len() <= one_line_budget {
1156         Some(format!("{} {} }}", result, items_str))
1157     } else {
1158         Some(format!(
1159             "{}\n{}{}\n{}}}",
1160             result,
1161             offset
1162                 .block_indent(context.config)
1163                 .to_string(context.config),
1164             items_str,
1165             offset.to_string(context.config)
1166         ))
1167     }
1168 }
1169
1170 fn format_tuple_struct(
1171     context: &RewriteContext,
1172     item_name: &str,
1173     ident: ast::Ident,
1174     vis: &ast::Visibility,
1175     fields: &[ast::StructField],
1176     generics: Option<&ast::Generics>,
1177     span: Span,
1178     offset: Indent,
1179 ) -> Option<String> {
1180     let mut result = String::with_capacity(1024);
1181
1182     let header_str = format_header(item_name, ident, vis);
1183     result.push_str(&header_str);
1184
1185     let body_lo = if fields.is_empty() {
1186         context.codemap.span_after(span, "(")
1187     } else {
1188         fields[0].span.lo
1189     };
1190     let body_hi = if fields.is_empty() {
1191         context.codemap.span_after(span, ")")
1192     } else {
1193         // This is a dirty hack to work around a missing `)` from the span of the last field.
1194         let last_arg_span = fields[fields.len() - 1].span;
1195         if context.snippet(last_arg_span).ends_with(")") {
1196             last_arg_span.hi
1197         } else {
1198             context
1199                 .codemap
1200                 .span_after(mk_sp(last_arg_span.hi, span.hi), ")")
1201         }
1202     };
1203
1204     let where_clause_str = match generics {
1205         Some(generics) => {
1206             let budget = context.budget(last_line_width(&header_str));
1207             let shape = Shape::legacy(budget, offset);
1208             let g_span = mk_sp(span.lo, body_lo);
1209             let generics_str = try_opt!(rewrite_generics(context, generics, shape, g_span));
1210             result.push_str(&generics_str);
1211
1212             let where_budget = context.budget(last_line_width(&result));
1213             try_opt!(rewrite_where_clause(
1214                 context,
1215                 &generics.where_clause,
1216                 context.config.item_brace_style(),
1217                 Shape::legacy(where_budget, offset.block_only()),
1218                 Density::Compressed,
1219                 ";",
1220                 true,
1221                 false,
1222                 None,
1223                 span,
1224                 body_hi,
1225             ))
1226         }
1227         None => "".to_owned(),
1228     };
1229
1230     if fields.is_empty() {
1231         // 3 = `();`
1232         let used_width = if result.contains('\n') {
1233             last_line_width(&result) + 3
1234         } else {
1235             offset.width() + result.len() + 3
1236         };
1237         if used_width > context.config.max_width() {
1238             result.push('\n');
1239             result.push_str(&offset
1240                 .block_indent(context.config)
1241                 .to_string(context.config))
1242         }
1243         result.push('(');
1244         let snippet = context.snippet(mk_sp(body_lo, context.codemap.span_before(span, ")")));
1245         if snippet.is_empty() {
1246             // `struct S ()`
1247         } else if snippet.trim_right_matches(&[' ', '\t'][..]).ends_with('\n') {
1248             result.push_str(&snippet.trim_right());
1249             result.push('\n');
1250             result.push_str(&offset.to_string(context.config));
1251         } else {
1252             result.push_str(&snippet);
1253         }
1254         result.push(')');
1255     } else {
1256         // 3 = `();`
1257         let body = try_opt!(
1258             rewrite_call_inner(
1259                 context,
1260                 "",
1261                 &fields.iter().map(|field| field).collect::<Vec<_>>()[..],
1262                 span,
1263                 Shape::legacy(context.budget(last_line_width(&result) + 3), offset),
1264                 context.config.fn_call_width(),
1265                 false,
1266             ).ok()
1267         );
1268         result.push_str(&body);
1269     }
1270
1271     if !where_clause_str.is_empty() && !where_clause_str.contains('\n') &&
1272         (result.contains('\n') ||
1273             offset.block_indent + result.len() + where_clause_str.len() + 1 >
1274                 context.config.max_width())
1275     {
1276         // We need to put the where clause on a new line, but we didn't
1277         // know that earlier, so the where clause will not be indented properly.
1278         result.push('\n');
1279         result.push_str(&(offset.block_only() + (context.config.tab_spaces() - 1))
1280             .to_string(context.config));
1281     }
1282     result.push_str(&where_clause_str);
1283
1284     Some(result)
1285 }
1286
1287 pub fn rewrite_type_alias(
1288     context: &RewriteContext,
1289     indent: Indent,
1290     ident: ast::Ident,
1291     ty: &ast::Ty,
1292     generics: &ast::Generics,
1293     vis: &ast::Visibility,
1294     span: Span,
1295 ) -> Option<String> {
1296     let mut result = String::new();
1297
1298     result.push_str(&format_visibility(vis));
1299     result.push_str("type ");
1300     result.push_str(&ident.to_string());
1301
1302     // 2 = `= `
1303     let shape = try_opt!(Shape::indented(indent + result.len(), context.config).sub_width(2));
1304     let g_span = mk_sp(context.codemap.span_after(span, "type"), ty.span.lo);
1305     let generics_str = try_opt!(rewrite_generics(context, generics, shape, g_span));
1306     result.push_str(&generics_str);
1307
1308     let where_budget = try_opt!(
1309         context
1310             .config
1311             .max_width()
1312             .checked_sub(last_line_width(&result))
1313     );
1314     let where_clause_str = try_opt!(rewrite_where_clause(
1315         context,
1316         &generics.where_clause,
1317         context.config.item_brace_style(),
1318         Shape::legacy(where_budget, indent),
1319         context.config.where_density(),
1320         "=",
1321         true,
1322         true,
1323         Some(span.hi),
1324         span,
1325         generics.span.hi,
1326     ));
1327     result.push_str(&where_clause_str);
1328     result.push_str(" = ");
1329
1330     let line_width = last_line_width(&result);
1331     // This checked_sub may fail as the extra space after '=' is not taken into account
1332     // In that case the budget is set to 0 which will make ty.rewrite retry on a new line
1333     let budget = context
1334         .config
1335         .max_width()
1336         .checked_sub(indent.width() + line_width + ";".len())
1337         .unwrap_or(0);
1338     let type_indent = indent + line_width;
1339     // Try to fit the type on the same line
1340     let ty_str = try_opt!(
1341         ty.rewrite(context, Shape::legacy(budget, type_indent))
1342             .or_else(|| {
1343                 // The line was too short, try to put the type on the next line
1344
1345                 // Remove the space after '='
1346                 result.pop();
1347                 let type_indent = indent.block_indent(context.config);
1348                 result.push('\n');
1349                 result.push_str(&type_indent.to_string(context.config));
1350                 let budget = try_opt!(
1351                     context
1352                         .config
1353                         .max_width()
1354                         .checked_sub(type_indent.width() + ";".len())
1355                 );
1356                 ty.rewrite(context, Shape::legacy(budget, type_indent))
1357             })
1358     );
1359     result.push_str(&ty_str);
1360     result.push_str(";");
1361     Some(result)
1362 }
1363
1364 fn type_annotation_spacing(config: &Config) -> (&str, &str) {
1365     (
1366         if config.space_before_type_annotation() {
1367             " "
1368         } else {
1369             ""
1370         },
1371         if config.space_after_type_annotation_colon() {
1372             " "
1373         } else {
1374             ""
1375         },
1376     )
1377 }
1378
1379 fn rewrite_missing_comment_on_field(
1380     context: &RewriteContext,
1381     shape: Shape,
1382     lo: BytePos,
1383     hi: BytePos,
1384     result: &mut String,
1385 ) -> Option<String> {
1386     let possibly_comment_snippet = context.snippet(mk_sp(lo, hi));
1387     let newline_index = possibly_comment_snippet.find('\n');
1388     let comment_index = possibly_comment_snippet.find('/');
1389     match (newline_index, comment_index) {
1390         (Some(i), Some(j)) if i > j => result.push(' '),
1391         _ => {
1392             result.push('\n');
1393             result.push_str(&shape.indent.to_string(context.config));
1394         }
1395     }
1396     let trimmed = possibly_comment_snippet.trim();
1397     if trimmed.is_empty() {
1398         None
1399     } else {
1400         rewrite_comment(trimmed, false, shape, context.config).map(|s| {
1401             format!("{}\n{}", s, shape.indent.to_string(context.config))
1402         })
1403     }
1404 }
1405
1406 pub fn rewrite_struct_field_prefix(
1407     context: &RewriteContext,
1408     field: &ast::StructField,
1409     shape: Shape,
1410 ) -> Option<String> {
1411     let vis = format_visibility(&field.vis);
1412     let mut attr_str = try_opt!(
1413         field
1414             .attrs
1415             .rewrite(context, Shape::indented(shape.indent, context.config))
1416     );
1417     // Try format missing comments after attributes
1418     let missing_comment = if !field.attrs.is_empty() {
1419         rewrite_missing_comment_on_field(
1420             context,
1421             shape,
1422             field.attrs[field.attrs.len() - 1].span.hi,
1423             field.span.lo,
1424             &mut attr_str,
1425         ).unwrap_or(String::new())
1426     } else {
1427         String::new()
1428     };
1429
1430     let type_annotation_spacing = type_annotation_spacing(context.config);
1431     Some(match field.ident {
1432         Some(name) => format!(
1433             "{}{}{}{}{}:",
1434             attr_str,
1435             missing_comment,
1436             vis,
1437             name,
1438             type_annotation_spacing.0
1439         ),
1440         None => format!("{}{}{}", attr_str, missing_comment, vis),
1441     })
1442 }
1443
1444 fn rewrite_struct_field_type(
1445     context: &RewriteContext,
1446     last_line_width: usize,
1447     field: &ast::StructField,
1448     spacing: &str,
1449     shape: Shape,
1450 ) -> Option<String> {
1451     let ty_shape = try_opt!(shape.offset_left(last_line_width + spacing.len()));
1452     field
1453         .ty
1454         .rewrite(context, ty_shape)
1455         .map(|ty| format!("{}{}", spacing, ty))
1456 }
1457
1458 impl Rewrite for ast::StructField {
1459     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
1460         rewrite_struct_field(context, self, shape, 0)
1461     }
1462 }
1463
1464 pub fn rewrite_struct_field(
1465     context: &RewriteContext,
1466     field: &ast::StructField,
1467     shape: Shape,
1468     lhs_max_width: usize,
1469 ) -> Option<String> {
1470     if contains_skip(&field.attrs) {
1471         let span = context.snippet(mk_sp(field.attrs[0].span.lo, field.span.hi));
1472         return wrap_str(span, context.config.max_width(), shape);
1473     }
1474
1475     let type_annotation_spacing = type_annotation_spacing(context.config);
1476     let prefix = try_opt!(rewrite_struct_field_prefix(context, field, shape));
1477
1478     // Try to put everything on a single line.
1479     let last_line_width = last_line_width(&prefix);
1480     let mut spacing = String::from(if field.ident.is_some() {
1481         type_annotation_spacing.1
1482     } else {
1483         ""
1484     });
1485     let lhs_offset = lhs_max_width.checked_sub(last_line_width).unwrap_or(0);
1486     for _ in 0..lhs_offset {
1487         spacing.push(' ');
1488     }
1489     let ty_rewritten = rewrite_struct_field_type(context, last_line_width, field, &spacing, shape);
1490     if let Some(ref ty) = ty_rewritten {
1491         if !ty.contains('\n') {
1492             return Some(prefix + &ty);
1493         }
1494     }
1495
1496     // We must use multiline.
1497     let type_offset = shape.indent.block_indent(context.config);
1498     let rewrite_type_in_next_line = || {
1499         field
1500             .ty
1501             .rewrite(context, Shape::indented(type_offset, context.config))
1502     };
1503
1504     match ty_rewritten {
1505         // If we start from the next line and type fits in a single line, then do so.
1506         Some(ref ty) => match rewrite_type_in_next_line() {
1507             Some(ref new_ty) if !new_ty.contains('\n') => Some(format!(
1508                 "{}\n{}{}",
1509                 prefix,
1510                 type_offset.to_string(&context.config),
1511                 &new_ty
1512             )),
1513             _ => Some(prefix + &ty),
1514         },
1515         _ => {
1516             let ty = try_opt!(rewrite_type_in_next_line());
1517             Some(format!(
1518                 "{}\n{}{}",
1519                 prefix,
1520                 type_offset.to_string(&context.config),
1521                 &ty
1522             ))
1523         }
1524     }
1525 }
1526
1527 pub fn rewrite_static(
1528     prefix: &str,
1529     vis: &ast::Visibility,
1530     ident: ast::Ident,
1531     ty: &ast::Ty,
1532     mutability: ast::Mutability,
1533     expr_opt: Option<&ptr::P<ast::Expr>>,
1534     offset: Indent,
1535     span: Span,
1536     context: &RewriteContext,
1537 ) -> Option<String> {
1538     let colon = colon_spaces(
1539         context.config.space_before_type_annotation(),
1540         context.config.space_after_type_annotation_colon(),
1541     );
1542     let prefix = format!(
1543         "{}{} {}{}{}",
1544         format_visibility(vis),
1545         prefix,
1546         format_mutability(mutability),
1547         ident,
1548         colon,
1549     );
1550     // 2 = " =".len()
1551     let ty_str = try_opt!(ty.rewrite(
1552         context,
1553         try_opt!(
1554             Shape::indented(offset.block_only(), context.config).offset_left(prefix.len() + 2)
1555         ),
1556     ));
1557
1558     if let Some(expr) = expr_opt {
1559         let lhs = format!("{}{} =", prefix, ty_str);
1560         // 1 = ;
1561         let remaining_width = context.config.max_width() - offset.block_indent - 1;
1562         rewrite_assign_rhs(
1563             context,
1564             lhs,
1565             expr,
1566             Shape::legacy(remaining_width, offset.block_only()),
1567         ).and_then(|res| {
1568             recover_comment_removed(res, span, context, Shape::indented(offset, context.config))
1569         })
1570             .map(|s| if s.ends_with(';') { s } else { s + ";" })
1571     } else {
1572         Some(format!("{}{};", prefix, ty_str))
1573     }
1574 }
1575
1576 pub fn rewrite_associated_type(
1577     ident: ast::Ident,
1578     ty_opt: Option<&ptr::P<ast::Ty>>,
1579     ty_param_bounds_opt: Option<&ast::TyParamBounds>,
1580     context: &RewriteContext,
1581     indent: Indent,
1582 ) -> Option<String> {
1583     let prefix = format!("type {}", ident);
1584
1585     let type_bounds_str = if let Some(ty_param_bounds) = ty_param_bounds_opt {
1586         let shape = Shape::indented(indent, context.config);
1587         let bounds: &[_] = ty_param_bounds;
1588         let bound_str = try_opt!(
1589             bounds
1590                 .iter()
1591                 .map(|ty_bound| ty_bound.rewrite(context, shape))
1592                 .collect::<Option<Vec<_>>>()
1593         );
1594         if bounds.len() > 0 {
1595             format!(": {}", join_bounds(context, shape, &bound_str))
1596         } else {
1597             String::new()
1598         }
1599     } else {
1600         String::new()
1601     };
1602
1603     if let Some(ty) = ty_opt {
1604         let ty_str = try_opt!(ty.rewrite(
1605             context,
1606             Shape::legacy(
1607                 context.config.max_width() - indent.block_indent - prefix.len() - 2,
1608                 indent.block_only(),
1609             ),
1610         ));
1611         Some(format!("{}{} = {};", prefix, type_bounds_str, ty_str))
1612     } else {
1613         Some(format!("{}{};", prefix, type_bounds_str))
1614     }
1615 }
1616
1617 pub fn rewrite_associated_impl_type(
1618     ident: ast::Ident,
1619     defaultness: ast::Defaultness,
1620     ty_opt: Option<&ptr::P<ast::Ty>>,
1621     ty_param_bounds_opt: Option<&ast::TyParamBounds>,
1622     context: &RewriteContext,
1623     indent: Indent,
1624 ) -> Option<String> {
1625     let result = try_opt!(rewrite_associated_type(
1626         ident,
1627         ty_opt,
1628         ty_param_bounds_opt,
1629         context,
1630         indent,
1631     ));
1632
1633     match defaultness {
1634         ast::Defaultness::Default => Some(format!("default {}", result)),
1635         _ => Some(result),
1636     }
1637 }
1638
1639 impl Rewrite for ast::FunctionRetTy {
1640     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
1641         match *self {
1642             ast::FunctionRetTy::Default(_) => Some(String::new()),
1643             ast::FunctionRetTy::Ty(ref ty) => {
1644                 let inner_width = try_opt!(shape.width.checked_sub(3));
1645                 ty.rewrite(context, Shape::legacy(inner_width, shape.indent + 3))
1646                     .map(|r| format!("-> {}", r))
1647             }
1648         }
1649     }
1650 }
1651
1652 fn is_empty_infer(context: &RewriteContext, ty: &ast::Ty) -> bool {
1653     match ty.node {
1654         ast::TyKind::Infer => {
1655             let original = context.snippet(ty.span);
1656             original != "_"
1657         }
1658         _ => false,
1659     }
1660 }
1661
1662 impl Rewrite for ast::Arg {
1663     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
1664         if is_named_arg(self) {
1665             let mut result = try_opt!(
1666                 self.pat
1667                     .rewrite(context, Shape::legacy(shape.width, shape.indent))
1668             );
1669
1670             if !is_empty_infer(context, &*self.ty) {
1671                 if context.config.space_before_type_annotation() {
1672                     result.push_str(" ");
1673                 }
1674                 result.push_str(":");
1675                 if context.config.space_after_type_annotation_colon() {
1676                     result.push_str(" ");
1677                 }
1678                 let max_width = try_opt!(shape.width.checked_sub(result.len()));
1679                 let ty_str = try_opt!(self.ty.rewrite(
1680                     context,
1681                     Shape::legacy(max_width, shape.indent + result.len()),
1682                 ));
1683                 result.push_str(&ty_str);
1684             }
1685
1686             Some(result)
1687         } else {
1688             self.ty.rewrite(context, shape)
1689         }
1690     }
1691 }
1692
1693 fn rewrite_explicit_self(
1694     explicit_self: &ast::ExplicitSelf,
1695     args: &[ast::Arg],
1696     context: &RewriteContext,
1697 ) -> Option<String> {
1698     match explicit_self.node {
1699         ast::SelfKind::Region(lt, m) => {
1700             let mut_str = format_mutability(m);
1701             match lt {
1702                 Some(ref l) => {
1703                     let lifetime_str = try_opt!(l.rewrite(
1704                         context,
1705                         Shape::legacy(context.config.max_width(), Indent::empty()),
1706                     ));
1707                     Some(format!("&{} {}self", lifetime_str, mut_str))
1708                 }
1709                 None => Some(format!("&{}self", mut_str)),
1710             }
1711         }
1712         ast::SelfKind::Explicit(ref ty, _) => {
1713             assert!(!args.is_empty(), "&[ast::Arg] shouldn't be empty.");
1714
1715             let mutability = explicit_self_mutability(&args[0]);
1716             let type_str = try_opt!(ty.rewrite(
1717                 context,
1718                 Shape::legacy(context.config.max_width(), Indent::empty()),
1719             ));
1720
1721             Some(format!(
1722                 "{}self: {}",
1723                 format_mutability(mutability),
1724                 type_str
1725             ))
1726         }
1727         ast::SelfKind::Value(_) => {
1728             assert!(!args.is_empty(), "&[ast::Arg] shouldn't be empty.");
1729
1730             let mutability = explicit_self_mutability(&args[0]);
1731
1732             Some(format!("{}self", format_mutability(mutability)))
1733         }
1734     }
1735 }
1736
1737 // Hacky solution caused by absence of `Mutability` in `SelfValue` and
1738 // `SelfExplicit` variants of `ast::ExplicitSelf_`.
1739 fn explicit_self_mutability(arg: &ast::Arg) -> ast::Mutability {
1740     if let ast::PatKind::Ident(ast::BindingMode::ByValue(mutability), _, _) = arg.pat.node {
1741         mutability
1742     } else {
1743         unreachable!()
1744     }
1745 }
1746
1747 pub fn span_lo_for_arg(arg: &ast::Arg) -> BytePos {
1748     if is_named_arg(arg) {
1749         arg.pat.span.lo
1750     } else {
1751         arg.ty.span.lo
1752     }
1753 }
1754
1755 pub fn span_hi_for_arg(context: &RewriteContext, arg: &ast::Arg) -> BytePos {
1756     match arg.ty.node {
1757         ast::TyKind::Infer if context.snippet(arg.ty.span) == "_" => arg.ty.span.hi,
1758         ast::TyKind::Infer if is_named_arg(arg) => arg.pat.span.hi,
1759         _ => arg.ty.span.hi,
1760     }
1761 }
1762
1763 pub fn is_named_arg(arg: &ast::Arg) -> bool {
1764     if let ast::PatKind::Ident(_, ident, _) = arg.pat.node {
1765         ident.node != symbol::keywords::Invalid.ident()
1766     } else {
1767         true
1768     }
1769 }
1770
1771 // Return type is (result, force_new_line_for_brace)
1772 fn rewrite_fn_base(
1773     context: &RewriteContext,
1774     indent: Indent,
1775     ident: ast::Ident,
1776     fd: &ast::FnDecl,
1777     generics: &ast::Generics,
1778     unsafety: ast::Unsafety,
1779     constness: ast::Constness,
1780     defaultness: ast::Defaultness,
1781     abi: abi::Abi,
1782     vis: &ast::Visibility,
1783     span: Span,
1784     newline_brace: bool,
1785     has_body: bool,
1786     has_braces: bool,
1787 ) -> Option<(String, bool)> {
1788     let mut force_new_line_for_brace = false;
1789
1790     let where_clause = &generics.where_clause;
1791
1792     let mut result = String::with_capacity(1024);
1793     // Vis unsafety abi.
1794     result.push_str(&*format_visibility(vis));
1795
1796     if let ast::Defaultness::Default = defaultness {
1797         result.push_str("default ");
1798     }
1799
1800     if let ast::Constness::Const = constness {
1801         result.push_str("const ");
1802     }
1803
1804     result.push_str(::utils::format_unsafety(unsafety));
1805
1806     if abi != abi::Abi::Rust {
1807         result.push_str(&::utils::format_abi(
1808             abi,
1809             context.config.force_explicit_abi(),
1810         ));
1811     }
1812
1813     // fn foo
1814     result.push_str("fn ");
1815     result.push_str(&ident.to_string());
1816
1817     // Generics.
1818     let overhead = if has_braces && !newline_brace {
1819         // 4 = `() {`
1820         4
1821     } else {
1822         // 2 = `()`
1823         2
1824     };
1825     let shape = try_opt!(
1826         Shape::indented(indent + last_line_width(&result), context.config).sub_width(overhead)
1827     );
1828     let g_span = mk_sp(span.lo, fd.output.span().lo);
1829     let generics_str = try_opt!(rewrite_generics(context, generics, shape, g_span));
1830     result.push_str(&generics_str);
1831
1832     let snuggle_angle_bracket = generics_str
1833         .lines()
1834         .last()
1835         .map_or(false, |l| l.trim_left().len() == 1);
1836
1837     // Note that the width and indent don't really matter, we'll re-layout the
1838     // return type later anyway.
1839     let ret_str = try_opt!(
1840         fd.output
1841             .rewrite(&context, Shape::indented(indent, context.config))
1842     );
1843
1844     let multi_line_ret_str = ret_str.contains('\n');
1845     let ret_str_len = if multi_line_ret_str { 0 } else { ret_str.len() };
1846
1847     // Args.
1848     let (mut one_line_budget, mut multi_line_budget, mut arg_indent) =
1849         try_opt!(compute_budgets_for_args(
1850             context,
1851             &result,
1852             indent,
1853             ret_str_len,
1854             newline_brace,
1855             has_braces,
1856         ));
1857
1858     if context.config.fn_args_layout() == IndentStyle::Block {
1859         arg_indent = indent.block_indent(context.config);
1860         // 1 = ","
1861         multi_line_budget = context.config.max_width() - (arg_indent.width() + 1);
1862     }
1863
1864     debug!(
1865         "rewrite_fn_base: one_line_budget: {}, multi_line_budget: {}, arg_indent: {:?}",
1866         one_line_budget,
1867         multi_line_budget,
1868         arg_indent
1869     );
1870
1871     // Check if vertical layout was forced.
1872     if one_line_budget == 0 {
1873         if snuggle_angle_bracket {
1874             result.push('(');
1875         } else {
1876             if context.config.fn_args_paren_newline() {
1877                 result.push('\n');
1878                 result.push_str(&arg_indent.to_string(context.config));
1879                 if context.config.fn_args_layout() == IndentStyle::Visual {
1880                     arg_indent = arg_indent + 1; // extra space for `(`
1881                 }
1882                 result.push('(');
1883             } else {
1884                 result.push_str("(");
1885                 if context.config.fn_args_layout() == IndentStyle::Visual {
1886                     result.push('\n');
1887                     result.push_str(&arg_indent.to_string(context.config));
1888                 }
1889             }
1890         }
1891     } else {
1892         result.push('(');
1893     }
1894     if context.config.spaces_within_parens() && fd.inputs.len() > 0 && result.ends_with('(') {
1895         result.push(' ')
1896     }
1897
1898     if multi_line_ret_str {
1899         one_line_budget = 0;
1900     }
1901
1902     // A conservative estimation, to goal is to be over all parens in generics
1903     let args_start = generics
1904         .ty_params
1905         .last()
1906         .map_or(span.lo, |tp| end_typaram(tp));
1907     let args_end = if fd.inputs.is_empty() {
1908         context.codemap.span_after(mk_sp(args_start, span.hi), ")")
1909     } else {
1910         let last_span = mk_sp(fd.inputs[fd.inputs.len() - 1].span().hi, span.hi);
1911         context.codemap.span_after(last_span, ")")
1912     };
1913     let args_span = mk_sp(
1914         context.codemap.span_after(mk_sp(args_start, span.hi), "("),
1915         args_end,
1916     );
1917     let arg_str = try_opt!(rewrite_args(
1918         context,
1919         &fd.inputs,
1920         fd.get_self().as_ref(),
1921         one_line_budget,
1922         multi_line_budget,
1923         indent,
1924         arg_indent,
1925         args_span,
1926         fd.variadic,
1927         generics_str.contains('\n'),
1928     ));
1929
1930     let multi_line_arg_str =
1931         arg_str.contains('\n') || arg_str.chars().last().map_or(false, |c| c == ',');
1932
1933     let put_args_in_block = match context.config.fn_args_layout() {
1934         IndentStyle::Block => multi_line_arg_str || generics_str.contains('\n'),
1935         _ => false,
1936     } && !fd.inputs.is_empty();
1937
1938     let mut args_last_line_contains_comment = false;
1939     if put_args_in_block {
1940         arg_indent = indent.block_indent(context.config);
1941         result.push('\n');
1942         result.push_str(&arg_indent.to_string(context.config));
1943         result.push_str(&arg_str);
1944         result.push('\n');
1945         result.push_str(&indent.to_string(context.config));
1946         result.push(')');
1947     } else {
1948         result.push_str(&arg_str);
1949         if context.config.spaces_within_parens() && fd.inputs.len() > 0 {
1950             result.push(' ')
1951         }
1952         // If the last line of args contains comment, we cannot put the closing paren
1953         // on the same line.
1954         if arg_str
1955             .lines()
1956             .last()
1957             .map_or(false, |last_line| last_line.contains("//"))
1958         {
1959             args_last_line_contains_comment = true;
1960             result.push('\n');
1961             result.push_str(&arg_indent.to_string(context.config));
1962         }
1963         result.push(')');
1964     }
1965
1966     // Return type.
1967     if !ret_str.is_empty() {
1968         let ret_should_indent = match context.config.fn_args_layout() {
1969             // If our args are block layout then we surely must have space.
1970             IndentStyle::Block if put_args_in_block => false,
1971             _ => {
1972                 // If we've already gone multi-line, or the return type would push over the max
1973                 // width, then put the return type on a new line. With the +1 for the signature
1974                 // length an additional space between the closing parenthesis of the argument and
1975                 // the arrow '->' is considered.
1976                 let mut sig_length = result.len() + indent.width() + ret_str_len + 1;
1977
1978                 // If there is no where clause, take into account the space after the return type
1979                 // and the brace.
1980                 if where_clause.predicates.is_empty() {
1981                     sig_length += 2;
1982                 }
1983
1984                 let overlong_sig = sig_length > context.config.max_width();
1985
1986                 (!args_last_line_contains_comment) &&
1987                     (result.contains('\n') || multi_line_ret_str || overlong_sig)
1988             }
1989         };
1990         let ret_indent = if ret_should_indent {
1991             let indent = match context.config.fn_return_indent() {
1992                 ReturnIndent::WithWhereClause => indent + 4,
1993                 // Aligning with non-existent args looks silly.
1994                 _ if arg_str.is_empty() => {
1995                     force_new_line_for_brace = true;
1996                     indent + 4
1997                 }
1998                 // FIXME: we might want to check that using the arg indent
1999                 // doesn't blow our budget, and if it does, then fallback to
2000                 // the where clause indent.
2001                 _ => arg_indent,
2002             };
2003
2004             result.push('\n');
2005             result.push_str(&indent.to_string(context.config));
2006             indent
2007         } else {
2008             result.push(' ');
2009             Indent::new(indent.block_indent, last_line_width(&result))
2010         };
2011
2012         if multi_line_ret_str || ret_should_indent {
2013             // Now that we know the proper indent and width, we need to
2014             // re-layout the return type.
2015             let ret_str = try_opt!(
2016                 fd.output
2017                     .rewrite(context, Shape::indented(ret_indent, context.config))
2018             );
2019             result.push_str(&ret_str);
2020         } else {
2021             result.push_str(&ret_str);
2022         }
2023
2024         // Comment between return type and the end of the decl.
2025         let snippet_lo = fd.output.span().hi;
2026         if where_clause.predicates.is_empty() {
2027             let snippet_hi = span.hi;
2028             let snippet = context.snippet(mk_sp(snippet_lo, snippet_hi));
2029             // Try to preserve the layout of the original snippet.
2030             let original_starts_with_newline = snippet
2031                 .find(|c| c != ' ')
2032                 .map_or(false, |i| snippet[i..].starts_with('\n'));
2033             let original_ends_with_newline = snippet
2034                 .rfind(|c| c != ' ')
2035                 .map_or(false, |i| snippet[i..].ends_with('\n'));
2036             let snippet = snippet.trim();
2037             if !snippet.is_empty() {
2038                 result.push(if original_starts_with_newline {
2039                     '\n'
2040                 } else {
2041                     ' '
2042                 });
2043                 result.push_str(snippet);
2044                 if original_ends_with_newline {
2045                     force_new_line_for_brace = true;
2046                 }
2047             }
2048         } else {
2049             // FIXME it would be nice to catch comments between the return type
2050             // and the where clause, but we don't have a span for the where
2051             // clause.
2052         }
2053     }
2054
2055     let should_compress_where = match context.config.where_density() {
2056         Density::Compressed => !result.contains('\n') || put_args_in_block,
2057         Density::CompressedIfEmpty => !has_body && !result.contains('\n'),
2058         _ => false,
2059     } || (put_args_in_block && ret_str.is_empty());
2060
2061     let pos_before_where = match fd.output {
2062         ast::FunctionRetTy::Default(..) => args_span.hi,
2063         ast::FunctionRetTy::Ty(ref ty) => ty.span.hi,
2064     };
2065     if where_clause.predicates.len() == 1 && should_compress_where {
2066         let budget = try_opt!(
2067             context
2068                 .config
2069                 .max_width()
2070                 .checked_sub(last_line_width(&result))
2071         );
2072         if let Some(where_clause_str) = rewrite_where_clause(
2073             context,
2074             where_clause,
2075             context.config.fn_brace_style(),
2076             Shape::legacy(budget, indent),
2077             Density::Compressed,
2078             "{",
2079             !has_braces,
2080             put_args_in_block && ret_str.is_empty(),
2081             Some(span.hi),
2082             span,
2083             pos_before_where,
2084         ) {
2085             if !where_clause_str.contains('\n') {
2086                 if last_line_width(&result) + where_clause_str.len() > context.config.max_width() {
2087                     result.push('\n');
2088                 }
2089
2090                 result.push_str(&where_clause_str);
2091
2092                 force_new_line_for_brace |= last_line_contains_single_line_comment(&result);
2093                 return Some((result, force_new_line_for_brace));
2094             }
2095         }
2096     }
2097
2098     let where_clause_str = try_opt!(rewrite_where_clause(
2099         context,
2100         where_clause,
2101         context.config.fn_brace_style(),
2102         Shape::indented(indent, context.config),
2103         Density::Tall,
2104         "{",
2105         !has_braces,
2106         put_args_in_block && ret_str.is_empty(),
2107         Some(span.hi),
2108         span,
2109         pos_before_where,
2110     ));
2111
2112     result.push_str(&where_clause_str);
2113
2114     force_new_line_for_brace |= last_line_contains_single_line_comment(&result);
2115     return Some((result, force_new_line_for_brace));
2116 }
2117
2118 fn last_line_contains_single_line_comment(s: &str) -> bool {
2119     s.lines().last().map_or(false, |l| l.contains("//"))
2120 }
2121
2122 fn rewrite_args(
2123     context: &RewriteContext,
2124     args: &[ast::Arg],
2125     explicit_self: Option<&ast::ExplicitSelf>,
2126     one_line_budget: usize,
2127     multi_line_budget: usize,
2128     indent: Indent,
2129     arg_indent: Indent,
2130     span: Span,
2131     variadic: bool,
2132     generics_str_contains_newline: bool,
2133 ) -> Option<String> {
2134     let mut arg_item_strs = try_opt!(
2135         args.iter()
2136             .map(|arg| {
2137                 arg.rewrite(&context, Shape::legacy(multi_line_budget, arg_indent))
2138             })
2139             .collect::<Option<Vec<_>>>()
2140     );
2141
2142     // Account for sugary self.
2143     // FIXME: the comment for the self argument is dropped. This is blocked
2144     // on rust issue #27522.
2145     let min_args = explicit_self
2146         .and_then(|explicit_self| {
2147             rewrite_explicit_self(explicit_self, args, context)
2148         })
2149         .map_or(1, |self_str| {
2150             arg_item_strs[0] = self_str;
2151             2
2152         });
2153
2154     // Comments between args.
2155     let mut arg_items = Vec::new();
2156     if min_args == 2 {
2157         arg_items.push(ListItem::from_str(""));
2158     }
2159
2160     // FIXME(#21): if there are no args, there might still be a comment, but
2161     // without spans for the comment or parens, there is no chance of
2162     // getting it right. You also don't get to put a comment on self, unless
2163     // it is explicit.
2164     if args.len() >= min_args || variadic {
2165         let comment_span_start = if min_args == 2 {
2166             let second_arg_start = if arg_has_pattern(&args[1]) {
2167                 args[1].pat.span.lo
2168             } else {
2169                 args[1].ty.span.lo
2170             };
2171             let reduced_span = mk_sp(span.lo, second_arg_start);
2172
2173             context.codemap.span_after_last(reduced_span, ",")
2174         } else {
2175             span.lo
2176         };
2177
2178         enum ArgumentKind<'a> {
2179             Regular(&'a ast::Arg),
2180             Variadic(BytePos),
2181         }
2182
2183         let variadic_arg = if variadic {
2184             let variadic_span = mk_sp(args.last().unwrap().ty.span.hi, span.hi);
2185             let variadic_start = context.codemap.span_after(variadic_span, "...") - BytePos(3);
2186             Some(ArgumentKind::Variadic(variadic_start))
2187         } else {
2188             None
2189         };
2190
2191         let more_items = itemize_list(
2192             context.codemap,
2193             args[min_args - 1..]
2194                 .iter()
2195                 .map(ArgumentKind::Regular)
2196                 .chain(variadic_arg),
2197             ")",
2198             |arg| match *arg {
2199                 ArgumentKind::Regular(arg) => span_lo_for_arg(arg),
2200                 ArgumentKind::Variadic(start) => start,
2201             },
2202             |arg| match *arg {
2203                 ArgumentKind::Regular(arg) => arg.ty.span.hi,
2204                 ArgumentKind::Variadic(start) => start + BytePos(3),
2205             },
2206             |arg| match *arg {
2207                 ArgumentKind::Regular(..) => None,
2208                 ArgumentKind::Variadic(..) => Some("...".to_owned()),
2209             },
2210             comment_span_start,
2211             span.hi,
2212         );
2213
2214         arg_items.extend(more_items);
2215     }
2216
2217     let fits_in_one_line = !generics_str_contains_newline &&
2218         (arg_items.len() == 0 || arg_items.len() == 1 && arg_item_strs[0].len() <= one_line_budget);
2219
2220     for (item, arg) in arg_items.iter_mut().zip(arg_item_strs) {
2221         item.item = Some(arg);
2222     }
2223
2224     let last_line_ends_with_comment = arg_items
2225         .iter()
2226         .last()
2227         .and_then(|item| item.post_comment.as_ref())
2228         .map_or(false, |s| s.trim().starts_with("//"));
2229
2230     let (indent, trailing_comma) = match context.config.fn_args_layout() {
2231         IndentStyle::Block if fits_in_one_line => {
2232             (indent.block_indent(context.config), SeparatorTactic::Never)
2233         }
2234         IndentStyle::Block => (
2235             indent.block_indent(context.config),
2236             context.config.trailing_comma(),
2237         ),
2238         IndentStyle::Visual if last_line_ends_with_comment => {
2239             (arg_indent, context.config.trailing_comma())
2240         }
2241         IndentStyle::Visual => (arg_indent, SeparatorTactic::Never),
2242     };
2243
2244     let tactic = definitive_tactic(
2245         &arg_items,
2246         context.config.fn_args_density().to_list_tactic(),
2247         Separator::Comma,
2248         one_line_budget,
2249     );
2250     let budget = match tactic {
2251         DefinitiveListTactic::Horizontal => one_line_budget,
2252         _ => multi_line_budget,
2253     };
2254
2255     debug!("rewrite_args: budget: {}, tactic: {:?}", budget, tactic);
2256
2257     let fmt = ListFormatting {
2258         tactic: tactic,
2259         separator: ",",
2260         trailing_separator: if variadic {
2261             SeparatorTactic::Never
2262         } else {
2263             trailing_comma
2264         },
2265         shape: Shape::legacy(budget, indent),
2266         ends_with_newline: tactic.ends_with_newline(context.config.fn_args_layout()),
2267         preserve_newline: true,
2268         config: context.config,
2269     };
2270
2271     write_list(&arg_items, &fmt)
2272 }
2273
2274 fn arg_has_pattern(arg: &ast::Arg) -> bool {
2275     if let ast::PatKind::Ident(_, ident, _) = arg.pat.node {
2276         ident.node != symbol::keywords::Invalid.ident()
2277     } else {
2278         true
2279     }
2280 }
2281
2282 fn compute_budgets_for_args(
2283     context: &RewriteContext,
2284     result: &str,
2285     indent: Indent,
2286     ret_str_len: usize,
2287     newline_brace: bool,
2288     has_braces: bool,
2289 ) -> Option<((usize, usize, Indent))> {
2290     debug!(
2291         "compute_budgets_for_args {} {:?}, {}, {}",
2292         result.len(),
2293         indent,
2294         ret_str_len,
2295         newline_brace
2296     );
2297     // Try keeping everything on the same line.
2298     if !result.contains('\n') {
2299         // 2 = `()`, 3 = `() `, space is before ret_string.
2300         let overhead = if ret_str_len == 0 { 2 } else { 3 };
2301         let mut used_space = indent.width() + result.len() + ret_str_len + overhead;
2302         if has_braces {
2303             if !newline_brace {
2304                 // 2 = `{}`
2305                 used_space += 2;
2306             }
2307         } else {
2308             // 1 = `;`
2309             used_space += 1;
2310         }
2311         let one_line_budget = context
2312             .config
2313             .max_width()
2314             .checked_sub(used_space)
2315             .unwrap_or(0);
2316
2317         if one_line_budget > 0 {
2318             // 4 = "() {".len()
2319             let multi_line_overhead =
2320                 indent.width() + result.len() + if newline_brace { 2 } else { 4 };
2321             let multi_line_budget =
2322                 try_opt!(context.config.max_width().checked_sub(multi_line_overhead));
2323
2324             return Some((
2325                 one_line_budget,
2326                 multi_line_budget,
2327                 indent + result.len() + 1,
2328             ));
2329         }
2330     }
2331
2332     // Didn't work. we must force vertical layout and put args on a newline.
2333     let new_indent = indent.block_indent(context.config);
2334     // Account for `)` and possibly ` {`.
2335     let used_space = new_indent.width() + if ret_str_len == 0 { 1 } else { 3 };
2336     let max_space = try_opt!(context.config.max_width().checked_sub(used_space));
2337     Some((0, max_space, new_indent))
2338 }
2339
2340 fn newline_for_brace(config: &Config, where_clause: &ast::WhereClause) -> bool {
2341     match config.fn_brace_style() {
2342         BraceStyle::AlwaysNextLine => true,
2343         BraceStyle::SameLineWhere if !where_clause.predicates.is_empty() => true,
2344         _ => false,
2345     }
2346 }
2347
2348 fn rewrite_generics(
2349     context: &RewriteContext,
2350     generics: &ast::Generics,
2351     shape: Shape,
2352     span: Span,
2353 ) -> Option<String> {
2354     let g_shape = try_opt!(generics_shape_from_config(context.config, shape, 0));
2355     let one_line_width = shape.width.checked_sub(2).unwrap_or(0);
2356     rewrite_generics_inner(context, generics, g_shape, one_line_width, span).or_else(|| {
2357         rewrite_generics_inner(context, generics, g_shape, 0, span)
2358     })
2359 }
2360
2361 fn rewrite_generics_inner(
2362     context: &RewriteContext,
2363     generics: &ast::Generics,
2364     shape: Shape,
2365     one_line_width: usize,
2366     span: Span,
2367 ) -> Option<String> {
2368     // FIXME: convert bounds to where clauses where they get too big or if
2369     // there is a where clause at all.
2370     let lifetimes: &[_] = &generics.lifetimes;
2371     let tys: &[_] = &generics.ty_params;
2372     if lifetimes.is_empty() && tys.is_empty() {
2373         return Some(String::new());
2374     }
2375
2376     // Strings for the generics.
2377     let lt_strs = lifetimes.iter().map(|lt| lt.rewrite(context, shape));
2378     let ty_strs = tys.iter().map(|ty_param| ty_param.rewrite(context, shape));
2379
2380     // Extract comments between generics.
2381     let lt_spans = lifetimes.iter().map(|l| {
2382         let hi = if l.bounds.is_empty() {
2383             l.lifetime.span.hi
2384         } else {
2385             l.bounds[l.bounds.len() - 1].span.hi
2386         };
2387         mk_sp(l.lifetime.span.lo, hi)
2388     });
2389     let ty_spans = tys.iter().map(|ty| ty.span());
2390
2391     let items = itemize_list(
2392         context.codemap,
2393         lt_spans.chain(ty_spans).zip(lt_strs.chain(ty_strs)),
2394         ">",
2395         |&(sp, _)| sp.lo,
2396         |&(sp, _)| sp.hi,
2397         // FIXME: don't clone
2398         |&(_, ref str)| str.clone(),
2399         context.codemap.span_after(span, "<"),
2400         span.hi,
2401     );
2402     format_generics_item_list(context, items, shape, one_line_width)
2403 }
2404
2405 pub fn generics_shape_from_config(config: &Config, shape: Shape, offset: usize) -> Option<Shape> {
2406     match config.generics_indent() {
2407         IndentStyle::Visual => shape.visual_indent(1 + offset).sub_width(offset + 2),
2408         IndentStyle::Block => {
2409             // 1 = ","
2410             shape
2411                 .block()
2412                 .block_indent(config.tab_spaces())
2413                 .with_max_width(config)
2414                 .sub_width(1)
2415         }
2416     }
2417 }
2418
2419 pub fn format_generics_item_list<I>(
2420     context: &RewriteContext,
2421     items: I,
2422     shape: Shape,
2423     one_line_budget: usize,
2424 ) -> Option<String>
2425 where
2426     I: Iterator<Item = ListItem>,
2427 {
2428     let item_vec = items.collect::<Vec<_>>();
2429
2430     let tactic = definitive_tactic(
2431         &item_vec,
2432         ListTactic::HorizontalVertical,
2433         Separator::Comma,
2434         one_line_budget,
2435     );
2436     let fmt = ListFormatting {
2437         tactic: tactic,
2438         separator: ",",
2439         trailing_separator: if context.config.generics_indent() == IndentStyle::Visual {
2440             SeparatorTactic::Never
2441         } else {
2442             context.config.trailing_comma()
2443         },
2444         shape: shape,
2445         ends_with_newline: tactic.ends_with_newline(context.config.generics_indent()),
2446         preserve_newline: true,
2447         config: context.config,
2448     };
2449
2450     let list_str = try_opt!(write_list(&item_vec, &fmt));
2451
2452     Some(wrap_generics_with_angle_brackets(
2453         context,
2454         &list_str,
2455         shape.indent,
2456     ))
2457 }
2458
2459 pub fn wrap_generics_with_angle_brackets(
2460     context: &RewriteContext,
2461     list_str: &str,
2462     list_offset: Indent,
2463 ) -> String {
2464     if context.config.generics_indent() == IndentStyle::Block &&
2465         (list_str.contains('\n') || list_str.ends_with(','))
2466     {
2467         format!(
2468             "<\n{}{}\n{}>",
2469             list_offset.to_string(context.config),
2470             list_str,
2471             list_offset
2472                 .block_unindent(context.config)
2473                 .to_string(context.config)
2474         )
2475     } else if context.config.spaces_within_angle_brackets() {
2476         format!("< {} >", list_str)
2477     } else {
2478         format!("<{}>", list_str)
2479     }
2480 }
2481
2482 fn rewrite_trait_bounds(
2483     context: &RewriteContext,
2484     type_param_bounds: &ast::TyParamBounds,
2485     shape: Shape,
2486 ) -> Option<String> {
2487     let bounds: &[_] = type_param_bounds;
2488
2489     if bounds.is_empty() {
2490         return Some(String::new());
2491     }
2492     let bound_str = try_opt!(
2493         bounds
2494             .iter()
2495             .map(|ty_bound| ty_bound.rewrite(&context, shape))
2496             .collect::<Option<Vec<_>>>()
2497     );
2498     Some(format!(": {}", join_bounds(context, shape, &bound_str)))
2499 }
2500
2501 fn rewrite_where_clause_rfc_style(
2502     context: &RewriteContext,
2503     where_clause: &ast::WhereClause,
2504     shape: Shape,
2505     terminator: &str,
2506     suppress_comma: bool,
2507     // where clause can be kept on the current line.
2508     snuggle: bool,
2509     span_end: Option<BytePos>,
2510     span: Span,
2511     span_end_before_where: BytePos,
2512 ) -> Option<String> {
2513     let block_shape = shape.block().with_max_width(context.config);
2514
2515     let (span_before, span_after) =
2516         missing_span_before_after_where(context, span.hi, span_end_before_where, where_clause);
2517     let (comment_before, comment_after) = try_opt!(rewrite_comments_before_after_where(
2518         context,
2519         span_before,
2520         span_after,
2521         shape,
2522     ));
2523
2524     let starting_newline = if snuggle && comment_before.is_empty() {
2525         " ".to_owned()
2526     } else {
2527         "\n".to_owned() + &block_shape.indent.to_string(context.config)
2528     };
2529
2530     let clause_shape = block_shape.block_indent(context.config.tab_spaces());
2531     // each clause on one line, trailing comma (except if suppress_comma)
2532     let span_start = where_clause.predicates[0].span().lo;
2533     // If we don't have the start of the next span, then use the end of the
2534     // predicates, but that means we miss comments.
2535     let len = where_clause.predicates.len();
2536     let end_of_preds = where_clause.predicates[len - 1].span().hi;
2537     let span_end = span_end.unwrap_or(end_of_preds);
2538     let items = itemize_list(
2539         context.codemap,
2540         where_clause.predicates.iter(),
2541         terminator,
2542         |pred| pred.span().lo,
2543         |pred| pred.span().hi,
2544         |pred| pred.rewrite(context, block_shape),
2545         span_start,
2546         span_end,
2547     );
2548     let comma_tactic = if suppress_comma {
2549         SeparatorTactic::Never
2550     } else {
2551         context.config.trailing_comma()
2552     };
2553
2554     let fmt = ListFormatting {
2555         tactic: DefinitiveListTactic::Vertical,
2556         separator: ",",
2557         trailing_separator: comma_tactic,
2558         shape: clause_shape,
2559         ends_with_newline: true,
2560         preserve_newline: true,
2561         config: context.config,
2562     };
2563     let preds_str = try_opt!(write_list(&items.collect::<Vec<_>>(), &fmt));
2564
2565     let newline_before_where = if comment_before.is_empty() || comment_before.ends_with('\n') {
2566         String::new()
2567     } else {
2568         "\n".to_owned() + &shape.indent.to_string(context.config)
2569     };
2570     let newline_after_where = if comment_after.is_empty() {
2571         String::new()
2572     } else {
2573         "\n".to_owned() + &clause_shape.indent.to_string(context.config)
2574     };
2575     Some(format!(
2576         "{}{}{}where{}{}\n{}{}",
2577         starting_newline,
2578         comment_before,
2579         newline_before_where,
2580         newline_after_where,
2581         comment_after,
2582         clause_shape.indent.to_string(context.config),
2583         preds_str
2584     ))
2585 }
2586
2587 fn rewrite_where_clause(
2588     context: &RewriteContext,
2589     where_clause: &ast::WhereClause,
2590     brace_style: BraceStyle,
2591     shape: Shape,
2592     density: Density,
2593     terminator: &str,
2594     suppress_comma: bool,
2595     snuggle: bool,
2596     span_end: Option<BytePos>,
2597     span: Span,
2598     span_end_before_where: BytePos,
2599 ) -> Option<String> {
2600     if where_clause.predicates.is_empty() {
2601         return Some(String::new());
2602     }
2603
2604     if context.config.where_style() == Style::Rfc {
2605         return rewrite_where_clause_rfc_style(
2606             context,
2607             where_clause,
2608             shape,
2609             terminator,
2610             suppress_comma,
2611             snuggle,
2612             span_end,
2613             span,
2614             span_end_before_where,
2615         );
2616     }
2617
2618     let extra_indent = Indent::new(context.config.tab_spaces(), 0);
2619
2620     let offset = match context.config.where_pred_indent() {
2621         IndentStyle::Block => shape.indent + extra_indent.block_indent(context.config),
2622         // 6 = "where ".len()
2623         IndentStyle::Visual => shape.indent + extra_indent + 6,
2624     };
2625     // FIXME: if where_pred_indent != Visual, then the budgets below might
2626     // be out by a char or two.
2627
2628     let budget = context.config.max_width() - offset.width();
2629     let span_start = where_clause.predicates[0].span().lo;
2630     // If we don't have the start of the next span, then use the end of the
2631     // predicates, but that means we miss comments.
2632     let len = where_clause.predicates.len();
2633     let end_of_preds = where_clause.predicates[len - 1].span().hi;
2634     let span_end = span_end.unwrap_or(end_of_preds);
2635     let items = itemize_list(
2636         context.codemap,
2637         where_clause.predicates.iter(),
2638         terminator,
2639         |pred| pred.span().lo,
2640         |pred| pred.span().hi,
2641         |pred| pred.rewrite(context, Shape::legacy(budget, offset)),
2642         span_start,
2643         span_end,
2644     );
2645     let item_vec = items.collect::<Vec<_>>();
2646     // FIXME: we don't need to collect here if the where_layout isn't
2647     // HorizontalVertical.
2648     let tactic = definitive_tactic(
2649         &item_vec,
2650         context.config.where_layout(),
2651         Separator::Comma,
2652         budget,
2653     );
2654
2655     let mut comma_tactic = context.config.trailing_comma();
2656     // Kind of a hack because we don't usually have trailing commas in where clauses.
2657     if comma_tactic == SeparatorTactic::Vertical || suppress_comma {
2658         comma_tactic = SeparatorTactic::Never;
2659     }
2660
2661     let fmt = ListFormatting {
2662         tactic: tactic,
2663         separator: ",",
2664         trailing_separator: comma_tactic,
2665         shape: Shape::legacy(budget, offset),
2666         ends_with_newline: tactic.ends_with_newline(context.config.where_pred_indent()),
2667         preserve_newline: true,
2668         config: context.config,
2669     };
2670     let preds_str = try_opt!(write_list(&item_vec, &fmt));
2671
2672     let end_length = if terminator == "{" {
2673         // If the brace is on the next line we don't need to count it otherwise it needs two
2674         // characters " {"
2675         match brace_style {
2676             BraceStyle::AlwaysNextLine | BraceStyle::SameLineWhere => 0,
2677             BraceStyle::PreferSameLine => 2,
2678         }
2679     } else if terminator == "=" {
2680         2
2681     } else {
2682         terminator.len()
2683     };
2684     if density == Density::Tall || preds_str.contains('\n') ||
2685         shape.indent.width() + " where ".len() + preds_str.len() + end_length > shape.width
2686     {
2687         Some(format!(
2688             "\n{}where {}",
2689             (shape.indent + extra_indent).to_string(context.config),
2690             preds_str
2691         ))
2692     } else {
2693         Some(format!(" where {}", preds_str))
2694     }
2695 }
2696
2697 fn missing_span_before_after_where(
2698     context: &RewriteContext,
2699     item_end: BytePos,
2700     before_item_span_end: BytePos,
2701     where_clause: &ast::WhereClause,
2702 ) -> (Span, Span) {
2703     let snippet = context.snippet(mk_sp(before_item_span_end, item_end));
2704     let pos_before_where =
2705         before_item_span_end + BytePos(snippet.find_uncommented("where").unwrap() as u32);
2706     let missing_span_before = mk_sp(before_item_span_end, pos_before_where);
2707     // 5 = `where`
2708     let pos_after_where = pos_before_where + BytePos(5);
2709     let missing_span_after = mk_sp(pos_after_where, where_clause.predicates[0].span().lo);
2710     (missing_span_before, missing_span_after)
2711 }
2712
2713 fn rewrite_missing_comment_in_where(
2714     context: &RewriteContext,
2715     comment: &str,
2716     shape: Shape,
2717 ) -> Option<String> {
2718     let comment = comment.trim();
2719     if comment.is_empty() {
2720         Some(String::new())
2721     } else {
2722         rewrite_comment(comment, false, shape, context.config)
2723     }
2724 }
2725
2726 fn rewrite_comments_before_after_where(
2727     context: &RewriteContext,
2728     span_before_where: Span,
2729     span_after_where: Span,
2730     shape: Shape,
2731 ) -> Option<(String, String)> {
2732     let before_comment = try_opt!(rewrite_missing_comment_in_where(
2733         context,
2734         &context.snippet(span_before_where),
2735         shape,
2736     ));
2737     let after_comment = try_opt!(rewrite_missing_comment_in_where(
2738         context,
2739         &context.snippet(span_after_where),
2740         shape.block_indent(context.config.tab_spaces()),
2741     ));
2742     Some((before_comment, after_comment))
2743 }
2744
2745 fn format_header(item_name: &str, ident: ast::Ident, vis: &ast::Visibility) -> String {
2746     format!("{}{}{}", format_visibility(vis), item_name, ident)
2747 }
2748
2749 fn format_generics(
2750     context: &RewriteContext,
2751     generics: &ast::Generics,
2752     opener: &str,
2753     terminator: &str,
2754     brace_style: BraceStyle,
2755     force_same_line_brace: bool,
2756     offset: Indent,
2757     span: Span,
2758     used_width: usize,
2759 ) -> Option<String> {
2760     let shape = Shape::legacy(context.budget(used_width + offset.width()), offset);
2761     let mut result = try_opt!(rewrite_generics(context, generics, shape, span));
2762
2763     let same_line_brace = if !generics.where_clause.predicates.is_empty() || result.contains('\n') {
2764         let budget = context
2765             .config
2766             .max_width()
2767             .checked_sub(last_line_width(&result))
2768             .unwrap_or(0);
2769         let where_clause_str = try_opt!(rewrite_where_clause(
2770             context,
2771             &generics.where_clause,
2772             brace_style,
2773             Shape::legacy(budget, offset.block_only()),
2774             Density::Tall,
2775             terminator,
2776             false,
2777             trimmed_last_line_width(&result) == 1,
2778             Some(span.hi),
2779             span,
2780             generics.span.hi,
2781         ));
2782         result.push_str(&where_clause_str);
2783         force_same_line_brace || brace_style == BraceStyle::PreferSameLine ||
2784             (generics.where_clause.predicates.is_empty() && trimmed_last_line_width(&result) == 1)
2785     } else {
2786         force_same_line_brace || trimmed_last_line_width(&result) == 1 ||
2787             brace_style != BraceStyle::AlwaysNextLine
2788     };
2789     let total_used_width = if result.contains('\n') {
2790         last_line_width(&result)
2791     } else {
2792         used_width + result.len()
2793     };
2794     let remaining_budget = context
2795         .config
2796         .max_width()
2797         .checked_sub(total_used_width)
2798         .unwrap_or(0);
2799     // If the same line brace if forced, it indicates that we are rewriting an item with empty body,
2800     // and hence we take the closer into account as well for one line budget.
2801     // We assume that the closer has the same length as the opener.
2802     let overhead = if force_same_line_brace {
2803         1 + opener.len() + opener.len()
2804     } else {
2805         1 + opener.len()
2806     };
2807     let forbid_same_line_brace = overhead > remaining_budget;
2808     if !forbid_same_line_brace && same_line_brace {
2809         result.push(' ');
2810     } else {
2811         result.push('\n');
2812         result.push_str(&offset.block_only().to_string(context.config));
2813     }
2814     result.push_str(opener);
2815
2816     Some(result)
2817 }