src/items.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 // Formatting top-level items - functions, structs, enums, traits, impls.
  12
  13 use Indent;
  14 use codemap::SpanUtils;
  15 use utils::{format_mutability, format_visibility, contains_skip, end_typaram, wrap_str,
  16             last_line_width, format_unsafety, trim_newlines, stmt_expr, semicolon_for_expr};
  17 use lists::{write_list, itemize_list, ListItem, ListFormatting, SeparatorTactic,
  18             DefinitiveListTactic, ListTactic, definitive_tactic, format_item_list};
  19 use expr::{is_empty_block, is_simple_block_stmt, rewrite_assign_rhs, type_annotation_separator};
  20 use comment::{FindUncommented, contains_comment};
  21 use visitor::FmtVisitor;
  22 use rewrite::{Rewrite, RewriteContext};
  23 use config::{Config, BlockIndentStyle, Density, ReturnIndent, BraceStyle, FnArgLayoutStyle};
  24 use itertools::Itertools;
  25
  26 use syntax::{ast, abi, ptr, codemap};
  27 use syntax::codemap::{Span, BytePos, mk_sp};
  28 use syntax::parse::token;
  29 use syntax::ast::ImplItem;
  30
  31 // Statements of the form
  32 // let pat: ty = init;
  33 impl Rewrite for ast::Local {
  34     fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option<String> {
  35         let mut result = "let ".to_owned();
  36         let pattern_offset = offset + result.len();
  37         // 1 = ;
  38         let pattern_width = try_opt!(width.checked_sub(pattern_offset.width() + 1));
  39
  40         let pat_str = try_opt!(self.pat.rewrite(&context, pattern_width, pattern_offset));
  41         result.push_str(&pat_str);
  42
  43         // String that is placed within the assignment pattern and expression.
  44         let infix = {
  45             let mut infix = String::new();
  46
  47             if let Some(ref ty) = self.ty {
  48                 let separator = type_annotation_separator(context.config);
  49                 let indent = offset + last_line_width(&result) + separator.len();
  50                 // 1 = ;
  51                 let budget = try_opt!(width.checked_sub(indent.width() + 1));
  52                 let rewrite = try_opt!(ty.rewrite(context, budget, indent));
  53
  54                 infix.push_str(separator);
  55                 infix.push_str(&rewrite);
  56             }
  57
  58             if self.init.is_some() {
  59                 infix.push_str(" =");
  60             }
  61
  62             infix
  63         };
  64
  65         result.push_str(&infix);
  66
  67         if let Some(ref ex) = self.init {
  68             let budget = try_opt!(width.checked_sub(context.block_indent.width() + 1));
  69
  70             // 1 = trailing semicolon;
  71             result =
  72                 try_opt!(rewrite_assign_rhs(&context, result, ex, budget, context.block_indent));
  73         }
  74
  75         result.push(';');
  76         Some(result)
  77     }
  78 }
  79
  80 impl<'a> FmtVisitor<'a> {
  81     pub fn format_foreign_mod(&mut self, fm: &ast::ForeignMod, span: Span) {
  82         let abi_str = ::utils::format_abi(fm.abi, self.config.force_explicit_abi);
  83         self.buffer.push_str(&abi_str);
  84
  85         let snippet = self.snippet(span);
  86         let brace_pos = snippet.find_uncommented("{").unwrap();
  87
  88         self.buffer.push_str("{");
  89         if !fm.items.is_empty() || contains_comment(&snippet[brace_pos..]) {
  90             // FIXME: this skips comments between the extern keyword and the opening
  91             // brace.
  92             self.last_pos = span.lo + BytePos(brace_pos as u32 + 1);
  93             self.block_indent = self.block_indent.block_indent(self.config);
  94
  95             if fm.items.is_empty() {
  96                 self.format_missing_no_indent(span.hi - BytePos(1));
  97                 self.block_indent = self.block_indent.block_unindent(self.config);
  98
  99                 self.buffer.push_str(&self.block_indent.to_string(self.config));
 100             } else {
 101                 for item in &fm.items {
 102                     self.format_foreign_item(&*item);
 103                 }
 104
 105                 self.block_indent = self.block_indent.block_unindent(self.config);
 106                 self.format_missing_with_indent(span.hi - BytePos(1));
 107             }
 108         }
 109
 110         self.buffer.push_str("}");
 111         self.last_pos = span.hi;
 112     }
 113
 114     fn format_foreign_item(&mut self, item: &ast::ForeignItem) {
 115         self.format_missing_with_indent(item.span.lo);
 116         // Drop semicolon or it will be interpreted as comment.
 117         // FIXME: this may be a faulty span from libsyntax.
 118         let span = mk_sp(item.span.lo, item.span.hi - BytePos(1));
 119
 120         match item.node {
 121             ast::ForeignItemKind::Fn(ref fn_decl, ref generics) => {
 122                 let indent = self.block_indent;
 123                 let rewrite = rewrite_fn_base(&self.get_context(),
 124                                               indent,
 125                                               item.ident,
 126                                               fn_decl,
 127                                               generics,
 128                                               ast::Unsafety::Normal,
 129                                               ast::Constness::NotConst,
 130                                               ast::Defaultness::Final,
 131                                               // These are not actually rust functions,
 132                                               // but we format them as such.
 133                                               abi::Abi::Rust,
 134                                               &item.vis,
 135                                               span,
 136                                               false,
 137                                               false);
 138
 139                 match rewrite {
 140                     Some((new_fn, _)) => {
 141                         self.buffer.push_str(&new_fn);
 142                         self.buffer.push_str(";");
 143                     }
 144                     None => self.format_missing(item.span.hi),
 145                 }
 146             }
 147             ast::ForeignItemKind::Static(ref ty, is_mutable) => {
 148                 // FIXME(#21): we're dropping potential comments in between the
 149                 // function keywords here.
 150                 let vis = format_visibility(&item.vis);
 151                 let mut_str = if is_mutable { "mut " } else { "" };
 152                 let prefix = format!("{}static {}{}: ", vis, mut_str, item.ident);
 153                 let offset = self.block_indent + prefix.len();
 154                 // 1 = ;
 155                 let width = self.config.max_width - offset.width() - 1;
 156                 let rewrite = ty.rewrite(&self.get_context(), width, offset);
 157
 158                 match rewrite {
 159                     Some(result) => {
 160                         self.buffer.push_str(&prefix);
 161                         self.buffer.push_str(&result);
 162                         self.buffer.push_str(";");
 163                     }
 164                     None => self.format_missing(item.span.hi),
 165                 }
 166             }
 167         }
 168
 169         self.last_pos = item.span.hi;
 170     }
 171
 172     pub fn rewrite_fn(&mut self,
 173                       indent: Indent,
 174                       ident: ast::Ident,
 175                       fd: &ast::FnDecl,
 176                       generics: &ast::Generics,
 177                       unsafety: ast::Unsafety,
 178                       constness: ast::Constness,
 179                       defaultness: ast::Defaultness,
 180                       abi: abi::Abi,
 181                       vis: &ast::Visibility,
 182                       span: Span,
 183                       block: &ast::Block)
 184                       -> Option<String> {
 185         let mut newline_brace = newline_for_brace(self.config, &generics.where_clause);
 186         let context = self.get_context();
 187
 188         let block_snippet = self.snippet(codemap::mk_sp(block.span.lo, block.span.hi));
 189         let has_body = !block_snippet[1..block_snippet.len() - 1].trim().is_empty() ||
 190                        !context.config.fn_empty_single_line;
 191
 192         let (mut result, force_newline_brace) = try_opt!(rewrite_fn_base(&context,
 193                                                                          indent,
 194                                                                          ident,
 195                                                                          fd,
 196                                                                          generics,
 197                                                                          unsafety,
 198                                                                          constness,
 199                                                                          defaultness,
 200                                                                          abi,
 201                                                                          vis,
 202                                                                          span,
 203                                                                          newline_brace,
 204                                                                          has_body));
 205
 206         if self.config.fn_brace_style != BraceStyle::AlwaysNextLine && !result.contains('\n') {
 207             newline_brace = false;
 208         } else if force_newline_brace {
 209             newline_brace = true;
 210         }
 211
 212         // Prepare for the function body by possibly adding a newline and
 213         // indent.
 214         // FIXME we'll miss anything between the end of the signature and the
 215         // start of the body, but we need more spans from the compiler to solve
 216         // this.
 217         if newline_brace {
 218             result.push('\n');
 219             result.push_str(&indent.to_string(self.config));
 220         } else {
 221             result.push(' ');
 222         }
 223
 224         self.single_line_fn(&result, block).or_else(|| Some(result))
 225     }
 226
 227     pub fn rewrite_required_fn(&mut self,
 228                                indent: Indent,
 229                                ident: ast::Ident,
 230                                sig: &ast::MethodSig,
 231                                span: Span)
 232                                -> Option<String> {
 233         // Drop semicolon or it will be interpreted as comment.
 234         let span = mk_sp(span.lo, span.hi - BytePos(1));
 235         let context = self.get_context();
 236
 237         let (mut result, _) = try_opt!(rewrite_fn_base(&context,
 238                                                        indent,
 239                                                        ident,
 240                                                        &sig.decl,
 241                                                        &sig.generics,
 242                                                        sig.unsafety,
 243                                                        sig.constness.node,
 244                                                        ast::Defaultness::Final,
 245                                                        sig.abi,
 246                                                        &ast::Visibility::Inherited,
 247                                                        span,
 248                                                        false,
 249                                                        false));
 250
 251         // Re-attach semicolon
 252         result.push(';');
 253
 254         Some(result)
 255     }
 256
 257     fn single_line_fn(&self, fn_str: &str, block: &ast::Block) -> Option<String> {
 258         if fn_str.contains('\n') {
 259             return None;
 260         }
 261
 262         let codemap = self.get_context().codemap;
 263
 264         if self.config.fn_empty_single_line && is_empty_block(block, codemap) &&
 265            self.block_indent.width() + fn_str.len() + 2 <= self.config.max_width {
 266             return Some(format!("{}{{}}", fn_str));
 267         }
 268
 269         if self.config.fn_single_line && is_simple_block_stmt(block, codemap) {
 270             let rewrite = {
 271                 if let Some(ref stmt) = block.stmts.first() {
 272                     match stmt_expr(stmt) {
 273                         Some(e) => {
 274                             let suffix = if semicolon_for_expr(e) { ";" } else { "" };
 275
 276                             e.rewrite(&self.get_context(),
 277                                          self.config.max_width - self.block_indent.width(),
 278                                          self.block_indent)
 279                                 .map(|s| s + suffix)
 280                                 .or_else(|| Some(self.snippet(e.span)))
 281                         }
 282                         None => {
 283                             stmt.rewrite(&self.get_context(),
 284                                          self.config.max_width - self.block_indent.width(),
 285                                          self.block_indent)
 286                         }
 287                     }
 288                 } else {
 289                     None
 290                 }
 291             };
 292
 293             if let Some(res) = rewrite {
 294                 let width = self.block_indent.width() + fn_str.len() + res.len() + 4;
 295                 if !res.contains('\n') && width <= self.config.max_width {
 296                     return Some(format!("{}{{ {} }}", fn_str, res));
 297                 }
 298             }
 299         }
 300
 301         None
 302     }
 303
 304     pub fn visit_enum(&mut self,
 305                       ident: ast::Ident,
 306                       vis: &ast::Visibility,
 307                       enum_def: &ast::EnumDef,
 308                       generics: &ast::Generics,
 309                       span: Span) {
 310         self.buffer.push_str(&format_header("enum ", ident, vis));
 311
 312         let enum_snippet = self.snippet(span);
 313         let brace_pos = enum_snippet.find_uncommented("{").unwrap();
 314         let body_start = span.lo + BytePos(brace_pos as u32 + 1);
 315         let generics_str = format_generics(&self.get_context(),
 316                                            generics,
 317                                            "{",
 318                                            "{",
 319                                            self.config.item_brace_style,
 320                                            enum_def.variants.is_empty(),
 321                                            self.block_indent,
 322                                            self.block_indent.block_indent(self.config),
 323                                            mk_sp(span.lo, body_start))
 324             .unwrap();
 325         self.buffer.push_str(&generics_str);
 326
 327         self.last_pos = body_start;
 328
 329         self.block_indent = self.block_indent.block_indent(self.config);
 330         let variant_list = self.format_variant_list(enum_def, body_start, span.hi - BytePos(1));
 331         match variant_list {
 332             Some(ref body_str) => self.buffer.push_str(body_str),
 333             None => {
 334                 if contains_comment(&enum_snippet[brace_pos..]) {
 335                     self.format_missing_no_indent(span.hi - BytePos(1))
 336                 } else {
 337                     self.format_missing(span.hi - BytePos(1))
 338                 }
 339             }
 340         }
 341         self.block_indent = self.block_indent.block_unindent(self.config);
 342
 343         if variant_list.is_some() || contains_comment(&enum_snippet[brace_pos..]) {
 344             self.buffer.push_str(&self.block_indent.to_string(self.config));
 345         }
 346         self.buffer.push_str("}");
 347         self.last_pos = span.hi;
 348     }
 349
 350     // Format the body of an enum definition
 351     fn format_variant_list(&self,
 352                            enum_def: &ast::EnumDef,
 353                            body_lo: BytePos,
 354                            body_hi: BytePos)
 355                            -> Option<String> {
 356         if enum_def.variants.is_empty() {
 357             return None;
 358         }
 359         let mut result = String::with_capacity(1024);
 360         result.push('\n');
 361         let indentation = self.block_indent.to_string(self.config);
 362         result.push_str(&indentation);
 363
 364         let items = itemize_list(self.codemap,
 365                                  enum_def.variants.iter(),
 366                                  "}",
 367                                  |f| {
 368             if !f.node.attrs.is_empty() {
 369                 f.node.attrs[0].span.lo
 370             } else {
 371                 f.span.lo
 372             }
 373         },
 374                                  |f| f.span.hi,
 375                                  |f| self.format_variant(f),
 376                                  body_lo,
 377                                  body_hi);
 378
 379         let budget = self.config.max_width - self.block_indent.width() - 2;
 380         let fmt = ListFormatting {
 381             tactic: DefinitiveListTactic::Vertical,
 382             separator: ",",
 383             trailing_separator: SeparatorTactic::from_bool(self.config.enum_trailing_comma),
 384             indent: self.block_indent,
 385             width: budget,
 386             ends_with_newline: true,
 387             config: self.config,
 388         };
 389
 390         let list = try_opt!(write_list(items, &fmt));
 391         result.push_str(&list);
 392         result.push('\n');
 393         Some(result)
 394     }
 395
 396     // Variant of an enum.
 397     fn format_variant(&self, field: &ast::Variant) -> Option<String> {
 398         if contains_skip(&field.node.attrs) {
 399             let lo = field.node.attrs[0].span.lo;
 400             let span = mk_sp(lo, field.span.hi);
 401             return Some(self.snippet(span));
 402         }
 403
 404         let indent = self.block_indent;
 405         let mut result = try_opt!(field.node
 406             .attrs
 407             .rewrite(&self.get_context(),
 408                      self.config.max_width - indent.width(),
 409                      indent));
 410         if !result.is_empty() {
 411             result.push('\n');
 412             result.push_str(&indent.to_string(self.config));
 413         }
 414
 415         let context = self.get_context();
 416         let variant_body = match field.node.data {
 417             ast::VariantData::Tuple(..) |
 418             ast::VariantData::Struct(..) => {
 419                 // FIXME: Should limit the width, as we have a trailing comma
 420                 format_struct(&context,
 421                               "",
 422                               field.node.name,
 423                               &ast::Visibility::Inherited,
 424                               &field.node.data,
 425                               None,
 426                               field.span,
 427                               indent,
 428                               Some(self.config.struct_variant_width))
 429             }
 430             ast::VariantData::Unit(..) => {
 431                 let tag = if let Some(ref expr) = field.node.disr_expr {
 432                     format!("{} = {}", field.node.name, self.snippet(expr.span))
 433                 } else {
 434                     field.node.name.to_string()
 435                 };
 436
 437                 wrap_str(tag,
 438                          self.config.max_width,
 439                          self.config.max_width - indent.width(),
 440                          indent)
 441             }
 442         };
 443
 444         if let Some(variant_str) = variant_body {
 445             result.push_str(&variant_str);
 446             Some(result)
 447         } else {
 448             None
 449         }
 450     }
 451 }
 452
 453 pub fn format_impl(context: &RewriteContext, item: &ast::Item, offset: Indent) -> Option<String> {
 454     if let ast::ItemKind::Impl(_, _, ref generics, ref trait_ref, _, ref items) = item.node {
 455         let mut result = String::new();
 456
 457         // First try to format the ref and type without a split at the 'for'.
 458         let mut ref_and_type = try_opt!(format_impl_ref_and_type(context, item, offset, false));
 459
 460         // If there is a line break present in the first result format it again
 461         // with a split at the 'for'. Skip this if there is no trait ref and
 462         // therefore no 'for'.
 463         if let Some(_) = *trait_ref {
 464             if ref_and_type.contains('\n') {
 465                 ref_and_type = try_opt!(format_impl_ref_and_type(context, item, offset, true));
 466             }
 467         }
 468         result.push_str(&ref_and_type);
 469
 470         let where_budget = try_opt!(context.config.max_width.checked_sub(last_line_width(&result)));
 471         let where_clause_str = try_opt!(rewrite_where_clause(context,
 472                                                              &generics.where_clause,
 473                                                              context.config,
 474                                                              context.config.item_brace_style,
 475                                                              context.block_indent,
 476                                                              where_budget,
 477                                                              context.config.where_density,
 478                                                              "{",
 479                                                              true,
 480                                                              None));
 481
 482         if try_opt!(is_impl_single_line(context, &items, &result, &where_clause_str, &item)) {
 483             result.push_str(&where_clause_str);
 484             if where_clause_str.contains('\n') {
 485                 let white_space = offset.to_string(context.config);
 486                 result.push_str(&format!("\n{}{{\n{}}}", &white_space, &white_space));
 487             } else {
 488                 result.push_str(" {}");
 489             }
 490             return Some(result);
 491         }
 492
 493         if !where_clause_str.is_empty() && !where_clause_str.contains('\n') {
 494             result.push('\n');
 495             let width = context.block_indent.width() + context.config.tab_spaces - 1;
 496             let where_indent = Indent::new(0, width);
 497             result.push_str(&where_indent.to_string(context.config));
 498         }
 499         result.push_str(&where_clause_str);
 500
 501         match context.config.item_brace_style {
 502             BraceStyle::AlwaysNextLine => result.push('\n'),
 503             BraceStyle::PreferSameLine => result.push(' '),
 504             BraceStyle::SameLineWhere => {
 505                 if !where_clause_str.is_empty() {
 506                     result.push('\n');
 507                     result.push_str(&offset.to_string(context.config));
 508                 } else {
 509                     result.push(' ');
 510                 }
 511             }
 512         }
 513
 514         result.push('{');
 515
 516         let snippet = context.snippet(item.span);
 517         let open_pos = try_opt!(snippet.find_uncommented("{")) + 1;
 518
 519         if !items.is_empty() || contains_comment(&snippet[open_pos..]) {
 520             let mut visitor = FmtVisitor::from_codemap(context.parse_session, context.config);
 521             visitor.block_indent = context.block_indent.block_indent(context.config);
 522             visitor.last_pos = item.span.lo + BytePos(open_pos as u32);
 523
 524             for item in items {
 525                 visitor.visit_impl_item(item);
 526             }
 527
 528             visitor.format_missing(item.span.hi - BytePos(1));
 529
 530             let inner_indent_str = visitor.block_indent.to_string(context.config);
 531             let outer_indent_str = context.block_indent.to_string(context.config);
 532
 533             result.push('\n');
 534             result.push_str(&inner_indent_str);
 535             result.push_str(trim_newlines(visitor.buffer.to_string().trim()));
 536             result.push('\n');
 537             result.push_str(&outer_indent_str);
 538         }
 539
 540         if result.chars().last().unwrap() == '{' {
 541             result.push('\n');
 542         }
 543         result.push('}');
 544
 545         Some(result)
 546     } else {
 547         unreachable!();
 548     }
 549 }
 550
 551 fn is_impl_single_line(context: &RewriteContext,
 552                        items: &[ImplItem],
 553                        result: &str,
 554                        where_clause_str: &str,
 555                        item: &ast::Item)
 556                        -> Option<bool> {
 557     let snippet = context.snippet(item.span);
 558     let open_pos = try_opt!(snippet.find_uncommented("{")) + 1;
 559
 560     Some(context.config.impl_empty_single_line && items.is_empty() &&
 561          result.len() + where_clause_str.len() <= context.config.max_width &&
 562          !contains_comment(&snippet[open_pos..]))
 563 }
 564
 565 fn format_impl_ref_and_type(context: &RewriteContext,
 566                             item: &ast::Item,
 567                             offset: Indent,
 568                             split_at_for: bool)
 569                             -> Option<String> {
 570     if let ast::ItemKind::Impl(unsafety, polarity, ref generics, ref trait_ref, ref self_ty, _) =
 571            item.node {
 572         let mut result = String::new();
 573
 574         result.push_str(&*format_visibility(&item.vis));
 575         result.push_str(format_unsafety(unsafety));
 576         result.push_str("impl");
 577
 578         let lo = context.codemap.span_after(item.span, "impl");
 579         let hi = match *trait_ref {
 580             Some(ref tr) => tr.path.span.lo,
 581             None => self_ty.span.lo,
 582         };
 583         let generics_str = try_opt!(rewrite_generics(context,
 584                                                      generics,
 585                                                      offset,
 586                                                      context.config.max_width,
 587                                                      offset + result.len(),
 588                                                      mk_sp(lo, hi)));
 589         result.push_str(&generics_str);
 590
 591         result.push(' ');
 592         if polarity == ast::ImplPolarity::Negative {
 593             result.push('!');
 594         }
 595         if let Some(ref trait_ref) = *trait_ref {
 596             let budget = try_opt!(context.config.max_width.checked_sub(result.len()));
 597             let indent = offset + result.len();
 598             result.push_str(&*try_opt!(trait_ref.rewrite(context, budget, indent)));
 599
 600             if split_at_for {
 601                 result.push('\n');
 602
 603                 // Add indentation of one additional tab.
 604                 let width = context.block_indent.width() + context.config.tab_spaces;
 605                 let for_indent = Indent::new(0, width);
 606                 result.push_str(&for_indent.to_string(context.config));
 607
 608                 result.push_str("for ");
 609             } else {
 610                 result.push_str(" for ");
 611             }
 612         }
 613
 614         let mut used_space = last_line_width(&result);
 615         if generics.where_clause.predicates.is_empty() {
 616             // If there is no where clause adapt budget for type formatting to take space and curly
 617             // brace into account.
 618             match context.config.item_brace_style {
 619                 BraceStyle::AlwaysNextLine => {}
 620                 BraceStyle::PreferSameLine => used_space += 2,
 621                 BraceStyle::SameLineWhere => used_space += 2,
 622             }
 623         }
 624
 625         let budget = try_opt!(context.config.max_width.checked_sub(used_space));
 626         let indent = offset + result.len();
 627         result.push_str(&*try_opt!(self_ty.rewrite(context, budget, indent)));
 628
 629         Some(result)
 630     } else {
 631         unreachable!();
 632     }
 633 }
 634
 635 pub fn format_struct(context: &RewriteContext,
 636                      item_name: &str,
 637                      ident: ast::Ident,
 638                      vis: &ast::Visibility,
 639                      struct_def: &ast::VariantData,
 640                      generics: Option<&ast::Generics>,
 641                      span: Span,
 642                      offset: Indent,
 643                      one_line_width: Option<usize>)
 644                      -> Option<String> {
 645     match *struct_def {
 646         ast::VariantData::Unit(..) => Some(format_unit_struct(item_name, ident, vis)),
 647         ast::VariantData::Tuple(ref fields, _) => {
 648             format_tuple_struct(context,
 649                                 item_name,
 650                                 ident,
 651                                 vis,
 652                                 fields,
 653                                 generics,
 654                                 span,
 655                                 offset)
 656         }
 657         ast::VariantData::Struct(ref fields, _) => {
 658             format_struct_struct(context,
 659                                  item_name,
 660                                  ident,
 661                                  vis,
 662                                  fields,
 663                                  generics,
 664                                  span,
 665                                  offset,
 666                                  one_line_width)
 667         }
 668     }
 669 }
 670
 671 pub fn format_trait(context: &RewriteContext, item: &ast::Item, offset: Indent) -> Option<String> {
 672     if let ast::ItemKind::Trait(unsafety, ref generics, ref type_param_bounds, ref trait_items) =
 673            item.node {
 674         let mut result = String::new();
 675         let header = format!("{}{}trait {}",
 676                              format_visibility(&item.vis),
 677                              format_unsafety(unsafety),
 678                              item.ident);
 679
 680         result.push_str(&header);
 681
 682         let body_lo = context.codemap.span_after(item.span, "{");
 683
 684         let generics_str = try_opt!(rewrite_generics(context,
 685                                                      generics,
 686                                                      offset,
 687                                                      context.config.max_width,
 688                                                      offset + result.len(),
 689                                                      mk_sp(item.span.lo, body_lo)));
 690         result.push_str(&generics_str);
 691
 692         let trait_bound_str = try_opt!(rewrite_trait_bounds(context,
 693                                                             type_param_bounds,
 694                                                             offset,
 695                                                             context.config.max_width));
 696         // If the trait, generics, and trait bound cannot fit on the same line,
 697         // put the trait bounds on an indented new line
 698         if offset.width() + last_line_width(&result) + trait_bound_str.len() >
 699            context.config.ideal_width {
 700             result.push('\n');
 701             let width = context.block_indent.width() + context.config.tab_spaces;
 702             let trait_indent = Indent::new(0, width);
 703             result.push_str(&trait_indent.to_string(context.config));
 704         }
 705         result.push_str(&trait_bound_str);
 706
 707         let has_body = !trait_items.is_empty();
 708
 709         let where_density =
 710             if (context.config.where_density == Density::Compressed &&
 711                 (!result.contains('\n') ||
 712                  context.config.fn_args_layout == FnArgLayoutStyle::Block)) ||
 713                (context.config.fn_args_layout == FnArgLayoutStyle::Block && result.is_empty()) ||
 714                (context.config.where_density == Density::CompressedIfEmpty && !has_body &&
 715                 !result.contains('\n')) {
 716                 Density::Compressed
 717             } else {
 718                 Density::Tall
 719             };
 720
 721         let where_budget = try_opt!(context.config
 722             .max_width
 723             .checked_sub(last_line_width(&result)));
 724         let where_clause_str = try_opt!(rewrite_where_clause(context,
 725                                                              &generics.where_clause,
 726                                                              context.config,
 727                                                              context.config.item_brace_style,
 728                                                              context.block_indent,
 729                                                              where_budget,
 730                                                              where_density,
 731                                                              "{",
 732                                                              has_body,
 733                                                              None));
 734         // If the where clause cannot fit on the same line,
 735         // put the where clause on a new line
 736         if !where_clause_str.contains('\n') &&
 737            last_line_width(&result) + where_clause_str.len() + offset.width() >
 738            context.config.ideal_width {
 739             result.push('\n');
 740             let width = context.block_indent.width() + context.config.tab_spaces - 1;
 741             let where_indent = Indent::new(0, width);
 742             result.push_str(&where_indent.to_string(context.config));
 743         }
 744         result.push_str(&where_clause_str);
 745
 746         match context.config.item_brace_style {
 747             BraceStyle::AlwaysNextLine => {
 748                 result.push('\n');
 749                 result.push_str(&offset.to_string(context.config));
 750             }
 751             BraceStyle::PreferSameLine => result.push(' '),
 752             BraceStyle::SameLineWhere => {
 753                 if !where_clause_str.is_empty() &&
 754                    (!trait_items.is_empty() || result.contains('\n')) {
 755                     result.push('\n');
 756                     result.push_str(&offset.to_string(context.config));
 757                 } else {
 758                     result.push(' ');
 759                 }
 760             }
 761         }
 762         result.push('{');
 763
 764         let snippet = context.snippet(item.span);
 765         let open_pos = try_opt!(snippet.find_uncommented("{")) + 1;
 766
 767         if !trait_items.is_empty() || contains_comment(&snippet[open_pos..]) {
 768             let mut visitor = FmtVisitor::from_codemap(context.parse_session, context.config);
 769             visitor.block_indent = context.block_indent.block_indent(context.config);
 770             visitor.last_pos = item.span.lo + BytePos(open_pos as u32);
 771
 772             for item in trait_items {
 773                 visitor.visit_trait_item(item);
 774             }
 775
 776             visitor.format_missing(item.span.hi - BytePos(1));
 777
 778             let inner_indent_str = visitor.block_indent.to_string(context.config);
 779             let outer_indent_str = context.block_indent.to_string(context.config);
 780
 781             result.push('\n');
 782             result.push_str(&inner_indent_str);
 783             result.push_str(trim_newlines(visitor.buffer.to_string().trim()));
 784             result.push('\n');
 785             result.push_str(&outer_indent_str);
 786         } else if result.contains('\n') {
 787             result.push('\n');
 788         }
 789
 790         result.push('}');
 791         Some(result)
 792     } else {
 793         unreachable!();
 794     }
 795 }
 796
 797 fn format_unit_struct(item_name: &str, ident: ast::Ident, vis: &ast::Visibility) -> String {
 798     format!("{};", format_header(item_name, ident, vis))
 799 }
 800
 801 fn format_struct_struct(context: &RewriteContext,
 802                         item_name: &str,
 803                         ident: ast::Ident,
 804                         vis: &ast::Visibility,
 805                         fields: &[ast::StructField],
 806                         generics: Option<&ast::Generics>,
 807                         span: Span,
 808                         offset: Indent,
 809                         one_line_width: Option<usize>)
 810                         -> Option<String> {
 811     let mut result = String::with_capacity(1024);
 812
 813     let header_str = format_header(item_name, ident, vis);
 814     result.push_str(&header_str);
 815
 816     let body_lo = context.codemap.span_after(span, "{");
 817
 818     let generics_str = match generics {
 819         Some(g) => {
 820             try_opt!(format_generics(context,
 821                                      g,
 822                                      "{",
 823                                      "{",
 824                                      context.config.item_brace_style,
 825                                      fields.is_empty(),
 826                                      offset,
 827                                      offset + header_str.len(),
 828                                      mk_sp(span.lo, body_lo)))
 829         }
 830         None => {
 831             if context.config.item_brace_style == BraceStyle::AlwaysNextLine && !fields.is_empty() {
 832                 format!("\n{}{{", context.block_indent.to_string(context.config))
 833             } else {
 834                 " {".to_owned()
 835             }
 836         }
 837     };
 838     result.push_str(&generics_str);
 839
 840     // FIXME(#919): properly format empty structs and their comments.
 841     if fields.is_empty() {
 842         result.push_str(&context.snippet(mk_sp(body_lo, span.hi)));
 843         return Some(result);
 844     }
 845
 846     let item_indent = offset.block_indent(context.config);
 847     // 1 = ","
 848     let item_budget = try_opt!(context.config.max_width.checked_sub(item_indent.width() + 1));
 849
 850     let items = itemize_list(context.codemap,
 851                              fields.iter(),
 852                              "}",
 853                              |field| {
 854         // Include attributes and doc comments, if present
 855         if !field.attrs.is_empty() {
 856             field.attrs[0].span.lo
 857         } else {
 858             field.span.lo
 859         }
 860     },
 861                              |field| field.ty.span.hi,
 862                              |field| field.rewrite(context, item_budget, item_indent),
 863                              context.codemap.span_after(span, "{"),
 864                              span.hi)
 865         .collect::<Vec<_>>();
 866     // 1 = ,
 867     let budget = context.config.max_width - offset.width() + context.config.tab_spaces - 1;
 868
 869     let tactic = match one_line_width {
 870         Some(w) => definitive_tactic(&items, ListTactic::LimitedHorizontalVertical(w), budget),
 871         None => DefinitiveListTactic::Vertical,
 872     };
 873
 874     let fmt = ListFormatting {
 875         tactic: tactic,
 876         separator: ",",
 877         trailing_separator: context.config.struct_trailing_comma,
 878         indent: item_indent,
 879         width: budget,
 880         ends_with_newline: true,
 881         config: context.config,
 882     };
 883     let items_str = try_opt!(write_list(&items, &fmt));
 884     if one_line_width.is_some() && !items_str.contains('\n') {
 885         Some(format!("{} {} }}", result, items_str))
 886     } else {
 887         Some(format!("{}\n{}{}\n{}}}",
 888                      result,
 889                      offset.block_indent(context.config).to_string(context.config),
 890                      items_str,
 891                      offset.to_string(context.config)))
 892     }
 893 }
 894
 895 fn format_tuple_struct(context: &RewriteContext,
 896                        item_name: &str,
 897                        ident: ast::Ident,
 898                        vis: &ast::Visibility,
 899                        fields: &[ast::StructField],
 900                        generics: Option<&ast::Generics>,
 901                        span: Span,
 902                        offset: Indent)
 903                        -> Option<String> {
 904     let mut result = String::with_capacity(1024);
 905
 906     let header_str = format_header(item_name, ident, vis);
 907     result.push_str(&header_str);
 908
 909     // FIXME(#919): don't lose comments on empty tuple structs.
 910     let body_lo = if fields.is_empty() {
 911         span.hi
 912     } else {
 913         fields[0].span.lo
 914     };
 915
 916     let where_clause_str = match generics {
 917         Some(generics) => {
 918             let generics_str = try_opt!(rewrite_generics(context,
 919                                                          generics,
 920                                                          offset,
 921                                                          context.config.max_width,
 922                                                          offset + header_str.len(),
 923                                                          mk_sp(span.lo, body_lo)));
 924             result.push_str(&generics_str);
 925
 926             let where_budget = try_opt!(context.config
 927                 .max_width
 928                 .checked_sub(last_line_width(&result)));
 929             try_opt!(rewrite_where_clause(context,
 930                                           &generics.where_clause,
 931                                           context.config,
 932                                           context.config.item_brace_style,
 933                                           context.block_indent,
 934                                           where_budget,
 935                                           Density::Compressed,
 936                                           ";",
 937                                           false,
 938                                           None))
 939         }
 940         None => "".to_owned(),
 941     };
 942     result.push('(');
 943
 944     let item_indent = context.block_indent + result.len();
 945     // 2 = ");"
 946     let item_budget = try_opt!(context.config.max_width.checked_sub(item_indent.width() + 2));
 947
 948     let items = itemize_list(context.codemap,
 949                              fields.iter(),
 950                              ")",
 951                              |field| {
 952         // Include attributes and doc comments, if present
 953         if !field.attrs.is_empty() {
 954             field.attrs[0].span.lo
 955         } else {
 956             field.span.lo
 957         }
 958     },
 959                              |field| field.ty.span.hi,
 960                              |field| field.rewrite(context, item_budget, item_indent),
 961                              context.codemap.span_after(span, "("),
 962                              span.hi);
 963     let body = try_opt!(format_item_list(items, item_budget, item_indent, context.config));
 964     result.push_str(&body);
 965     result.push(')');
 966
 967     if !where_clause_str.is_empty() && !where_clause_str.contains('\n') &&
 968        (result.contains('\n') ||
 969         context.block_indent.width() + result.len() + where_clause_str.len() + 1 >
 970         context.config.max_width) {
 971         // We need to put the where clause on a new line, but we didn'to_string
 972         // know that earlier, so the where clause will not be indented properly.
 973         result.push('\n');
 974         result.push_str(&(context.block_indent + (context.config.tab_spaces - 1))
 975             .to_string(context.config));
 976     }
 977     result.push_str(&where_clause_str);
 978
 979     Some(result)
 980 }
 981
 982 pub fn rewrite_type_alias(context: &RewriteContext,
 983                           indent: Indent,
 984                           ident: ast::Ident,
 985                           ty: &ast::Ty,
 986                           generics: &ast::Generics,
 987                           vis: &ast::Visibility,
 988                           span: Span)
 989                           -> Option<String> {
 990     let mut result = String::new();
 991
 992     result.push_str(&format_visibility(vis));
 993     result.push_str("type ");
 994     result.push_str(&ident.to_string());
 995
 996     let generics_indent = indent + result.len();
 997     let generics_span = mk_sp(context.codemap.span_after(span, "type"), ty.span.lo);
 998     let generics_width = context.config.max_width - " =".len();
 999     let generics_str = try_opt!(rewrite_generics(context,
1000                                                  generics,
1001                                                  indent,
1002                                                  generics_width,
1003                                                  generics_indent,
1004                                                  generics_span));
1005
1006     result.push_str(&generics_str);
1007
1008     let where_budget = try_opt!(context.config
1009         .max_width
1010         .checked_sub(last_line_width(&result)));
1011     let where_clause_str = try_opt!(rewrite_where_clause(context,
1012                                                          &generics.where_clause,
1013                                                          context.config,
1014                                                          context.config.item_brace_style,
1015                                                          indent,
1016                                                          where_budget,
1017                                                          context.config.where_density,
1018                                                          "=",
1019                                                          false,
1020                                                          Some(span.hi)));
1021     result.push_str(&where_clause_str);
1022     result.push_str(" = ");
1023
1024     let line_width = last_line_width(&result);
1025     // This checked_sub may fail as the extra space after '=' is not taken into account
1026     // In that case the budget is set to 0 which will make ty.rewrite retry on a new line
1027     let budget = context.config
1028         .max_width
1029         .checked_sub(indent.width() + line_width + ";".len())
1030         .unwrap_or(0);
1031     let type_indent = indent + line_width;
1032     // Try to fit the type on the same line
1033     let ty_str = try_opt!(ty.rewrite(context, budget, type_indent)
1034         .or_else(|| {
1035             // The line was too short, try to put the type on the next line
1036
1037             // Remove the space after '='
1038             result.pop();
1039             let type_indent = indent.block_indent(context.config);
1040             result.push('\n');
1041             result.push_str(&type_indent.to_string(context.config));
1042             let budget = try_opt!(context.config
1043                 .max_width
1044                 .checked_sub(type_indent.width() + ";".len()));
1045             ty.rewrite(context, budget, type_indent)
1046         }));
1047     result.push_str(&ty_str);
1048     result.push_str(";");
1049     Some(result)
1050 }
1051
1052 fn type_annotation_spacing(config: &Config) -> (&str, &str) {
1053     (if config.space_before_type_annotation {
1054          " "
1055      } else {
1056          ""
1057      },
1058      if config.space_after_type_annotation_colon {
1059          " "
1060      } else {
1061          ""
1062      })
1063 }
1064
1065 impl Rewrite for ast::StructField {
1066     fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option<String> {
1067         if contains_skip(&self.attrs) {
1068             let span = context.snippet(mk_sp(self.attrs[0].span.lo, self.span.hi));
1069             return wrap_str(span, context.config.max_width, width, offset);
1070         }
1071
1072         let name = self.ident;
1073         let vis = format_visibility(&self.vis);
1074         let mut attr_str = try_opt!(self.attrs
1075             .rewrite(context, context.config.max_width - offset.width(), offset));
1076         if !attr_str.is_empty() {
1077             attr_str.push('\n');
1078             attr_str.push_str(&offset.to_string(context.config));
1079         }
1080
1081         let type_annotation_spacing = type_annotation_spacing(context.config);
1082         let result = match name {
1083             Some(name) => {
1084                 format!("{}{}{}{}:{}",
1085                         attr_str,
1086                         vis,
1087                         name,
1088                         type_annotation_spacing.0,
1089                         type_annotation_spacing.1)
1090             }
1091             None => format!("{}{}", attr_str, vis),
1092         };
1093
1094         let last_line_width = last_line_width(&result);
1095         let budget = try_opt!(width.checked_sub(last_line_width));
1096         let rewrite = try_opt!(self.ty.rewrite(context, budget, offset + last_line_width));
1097         Some(result + &rewrite)
1098     }
1099 }
1100
1101 pub fn rewrite_static(prefix: &str,
1102                       vis: &ast::Visibility,
1103                       ident: ast::Ident,
1104                       ty: &ast::Ty,
1105                       mutability: ast::Mutability,
1106                       expr_opt: Option<&ptr::P<ast::Expr>>,
1107                       context: &RewriteContext)
1108                       -> Option<String> {
1109     let type_annotation_spacing = type_annotation_spacing(context.config);
1110     let prefix = format!("{}{} {}{}{}:{}",
1111                          format_visibility(vis),
1112                          prefix,
1113                          format_mutability(mutability),
1114                          ident,
1115                          type_annotation_spacing.0,
1116                          type_annotation_spacing.1);
1117     // 2 = " =".len()
1118     let ty_str = try_opt!(ty.rewrite(context,
1119                                      context.config.max_width - context.block_indent.width() -
1120                                      prefix.len() - 2,
1121                                      context.block_indent));
1122
1123     if let Some(expr) = expr_opt {
1124         let lhs = format!("{}{} =", prefix, ty_str);
1125         // 1 = ;
1126         let remaining_width = context.config.max_width - context.block_indent.width() - 1;
1127         rewrite_assign_rhs(context, lhs, expr, remaining_width, context.block_indent)
1128             .map(|s| s + ";")
1129     } else {
1130         let lhs = format!("{}{};", prefix, ty_str);
1131         Some(lhs)
1132     }
1133 }
1134
1135 pub fn rewrite_associated_type(ident: ast::Ident,
1136                                ty_opt: Option<&ptr::P<ast::Ty>>,
1137                                ty_param_bounds_opt: Option<&ast::TyParamBounds>,
1138                                context: &RewriteContext,
1139                                indent: Indent)
1140                                -> Option<String> {
1141     let prefix = format!("type {}", ident);
1142
1143     let type_bounds_str = if let Some(ty_param_bounds) = ty_param_bounds_opt {
1144         let bounds: &[_] = ty_param_bounds;
1145         let bound_str = try_opt!(bounds.iter()
1146             .map(|ty_bound| ty_bound.rewrite(context, context.config.max_width, indent))
1147             .intersperse(Some(" + ".to_string()))
1148             .collect::<Option<String>>());
1149         if bounds.len() > 0 {
1150             format!(": {}", bound_str)
1151         } else {
1152             String::new()
1153         }
1154     } else {
1155         String::new()
1156     };
1157
1158     if let Some(ty) = ty_opt {
1159         let ty_str = try_opt!(ty.rewrite(context,
1160                                          context.config.max_width - context.block_indent.width() -
1161                                          prefix.len() -
1162                                          2,
1163                                          context.block_indent));
1164         Some(format!("{} = {};", prefix, ty_str))
1165     } else {
1166         Some(format!("{}{};", prefix, type_bounds_str))
1167     }
1168 }
1169
1170 impl Rewrite for ast::FunctionRetTy {
1171     fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option<String> {
1172         match *self {
1173             ast::FunctionRetTy::Default(_) => Some(String::new()),
1174             ast::FunctionRetTy::Ty(ref ty) => {
1175                 let inner_width = try_opt!(width.checked_sub(3));
1176                 ty.rewrite(context, inner_width, offset + 3).map(|r| format!("-> {}", r))
1177             }
1178         }
1179     }
1180 }
1181
1182 impl Rewrite for ast::Arg {
1183     fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option<String> {
1184         if is_named_arg(self) {
1185             let mut result = try_opt!(self.pat.rewrite(context, width, offset));
1186
1187             if self.ty.node != ast::TyKind::Infer {
1188                 if context.config.space_before_type_annotation {
1189                     result.push_str(" ");
1190                 }
1191                 result.push_str(":");
1192                 if context.config.space_after_type_annotation_colon {
1193                     result.push_str(" ");
1194                 }
1195                 let max_width = try_opt!(width.checked_sub(result.len()));
1196                 let ty_str = try_opt!(self.ty.rewrite(context, max_width, offset + result.len()));
1197                 result.push_str(&ty_str);
1198             }
1199
1200             Some(result)
1201         } else {
1202             self.ty.rewrite(context, width, offset)
1203         }
1204     }
1205 }
1206
1207 fn rewrite_explicit_self(explicit_self: &ast::ExplicitSelf,
1208                          args: &[ast::Arg],
1209                          context: &RewriteContext)
1210                          -> Option<String> {
1211     match explicit_self.node {
1212         ast::SelfKind::Region(lt, m) => {
1213             let mut_str = format_mutability(m);
1214             match lt {
1215                 Some(ref l) => {
1216                     let lifetime_str =
1217                         try_opt!(l.rewrite(context, usize::max_value(), Indent::empty()));
1218                     Some(format!("&{} {}self", lifetime_str, mut_str))
1219                 }
1220                 None => Some(format!("&{}self", mut_str)),
1221             }
1222         }
1223         ast::SelfKind::Explicit(ref ty, _) => {
1224             assert!(!args.is_empty(), "&[ast::Arg] shouldn't be empty.");
1225
1226             let mutability = explicit_self_mutability(&args[0]);
1227             let type_str = try_opt!(ty.rewrite(context, usize::max_value(), Indent::empty()));
1228
1229             Some(format!("{}self: {}", format_mutability(mutability), type_str))
1230         }
1231         ast::SelfKind::Value(_) => {
1232             assert!(!args.is_empty(), "&[ast::Arg] shouldn't be empty.");
1233
1234             let mutability = explicit_self_mutability(&args[0]);
1235
1236             Some(format!("{}self", format_mutability(mutability)))
1237         }
1238     }
1239 }
1240
1241 // Hacky solution caused by absence of `Mutability` in `SelfValue` and
1242 // `SelfExplicit` variants of `ast::ExplicitSelf_`.
1243 fn explicit_self_mutability(arg: &ast::Arg) -> ast::Mutability {
1244     if let ast::PatKind::Ident(ast::BindingMode::ByValue(mutability), _, _) = arg.pat.node {
1245         mutability
1246     } else {
1247         unreachable!()
1248     }
1249 }
1250
1251 pub fn span_lo_for_arg(arg: &ast::Arg) -> BytePos {
1252     if is_named_arg(arg) {
1253         arg.pat.span.lo
1254     } else {
1255         arg.ty.span.lo
1256     }
1257 }
1258
1259 pub fn span_hi_for_arg(arg: &ast::Arg) -> BytePos {
1260     match arg.ty.node {
1261         ast::TyKind::Infer if is_named_arg(arg) => arg.pat.span.hi,
1262         _ => arg.ty.span.hi,
1263     }
1264 }
1265
1266 pub fn is_named_arg(arg: &ast::Arg) -> bool {
1267     if let ast::PatKind::Ident(_, ident, _) = arg.pat.node {
1268         ident.node != token::keywords::Invalid.ident()
1269     } else {
1270         true
1271     }
1272 }
1273
1274 fn span_for_return(ret: &ast::FunctionRetTy) -> Span {
1275     match *ret {
1276         ast::FunctionRetTy::Default(ref span) => span.clone(),
1277         ast::FunctionRetTy::Ty(ref ty) => ty.span,
1278     }
1279 }
1280
1281 fn span_for_ty_param(ty: &ast::TyParam) -> Span {
1282     // Note that ty.span is the span for ty.ident, not the whole item.
1283     let lo = ty.span.lo;
1284     if let Some(ref def) = ty.default {
1285         return mk_sp(lo, def.span.hi);
1286     }
1287     if ty.bounds.is_empty() {
1288         return ty.span;
1289     }
1290     let hi = match ty.bounds[ty.bounds.len() - 1] {
1291         ast::TyParamBound::TraitTyParamBound(ref ptr, _) => ptr.span.hi,
1292         ast::TyParamBound::RegionTyParamBound(ref l) => l.span.hi,
1293     };
1294     mk_sp(lo, hi)
1295 }
1296
1297 fn span_for_where_pred(pred: &ast::WherePredicate) -> Span {
1298     match *pred {
1299         ast::WherePredicate::BoundPredicate(ref p) => p.span,
1300         ast::WherePredicate::RegionPredicate(ref p) => p.span,
1301         ast::WherePredicate::EqPredicate(ref p) => p.span,
1302     }
1303 }
1304
1305 // Return type is (result, force_new_line_for_brace)
1306 fn rewrite_fn_base(context: &RewriteContext,
1307                    indent: Indent,
1308                    ident: ast::Ident,
1309                    fd: &ast::FnDecl,
1310                    generics: &ast::Generics,
1311                    unsafety: ast::Unsafety,
1312                    constness: ast::Constness,
1313                    defaultness: ast::Defaultness,
1314                    abi: abi::Abi,
1315                    vis: &ast::Visibility,
1316                    span: Span,
1317                    newline_brace: bool,
1318                    has_body: bool)
1319                    -> Option<(String, bool)> {
1320     let mut force_new_line_for_brace = false;
1321     // FIXME we'll lose any comments in between parts of the function decl, but
1322     // anyone who comments there probably deserves what they get.
1323
1324     let where_clause = &generics.where_clause;
1325
1326     let mut result = String::with_capacity(1024);
1327     // Vis unsafety abi.
1328     result.push_str(&*format_visibility(vis));
1329
1330     if let ast::Defaultness::Default = defaultness {
1331         result.push_str("default ");
1332     }
1333
1334     if let ast::Constness::Const = constness {
1335         result.push_str("const ");
1336     }
1337
1338     result.push_str(::utils::format_unsafety(unsafety));
1339
1340     if abi != abi::Abi::Rust {
1341         result.push_str(&::utils::format_abi(abi, context.config.force_explicit_abi));
1342     }
1343
1344     // fn foo
1345     result.push_str("fn ");
1346     result.push_str(&ident.to_string());
1347
1348     // Generics.
1349     let generics_indent = indent + result.len();
1350     let generics_span = mk_sp(span.lo, span_for_return(&fd.output).lo);
1351     let generics_str = try_opt!(rewrite_generics(context,
1352                                                  generics,
1353                                                  indent,
1354                                                  context.config.max_width,
1355                                                  generics_indent,
1356                                                  generics_span));
1357     result.push_str(&generics_str);
1358
1359     // Note that if the width and indent really matter, we'll re-layout the
1360     // return type later anyway.
1361     let ret_str = try_opt!(fd.output
1362         .rewrite(&context, context.config.max_width - indent.width(), indent));
1363
1364     let multi_line_ret_str = ret_str.contains('\n');
1365     let ret_str_len = if multi_line_ret_str { 0 } else { ret_str.len() };
1366
1367     // Args.
1368     let (mut one_line_budget, mut multi_line_budget, mut arg_indent) =
1369         try_opt!(compute_budgets_for_args(context, &result, indent, ret_str_len, newline_brace));
1370
1371     if context.config.fn_args_layout == FnArgLayoutStyle::Block ||
1372        context.config.fn_args_layout == FnArgLayoutStyle::BlockAlways {
1373         arg_indent = indent.block_indent(context.config);
1374         multi_line_budget = context.config.max_width - arg_indent.width();
1375     }
1376
1377     debug!("rewrite_fn: one_line_budget: {}, multi_line_budget: {}, arg_indent: {:?}",
1378            one_line_budget,
1379            multi_line_budget,
1380            arg_indent);
1381
1382     // Check if vertical layout was forced by compute_budget_for_args.
1383     if one_line_budget == 0 {
1384         if context.config.fn_args_paren_newline {
1385             result.push('\n');
1386             result.push_str(&arg_indent.to_string(context.config));
1387             arg_indent = arg_indent + 1; // extra space for `(`
1388             result.push('(');
1389         } else {
1390             result.push_str("(\n");
1391             result.push_str(&arg_indent.to_string(context.config));
1392         }
1393     } else {
1394         result.push('(');
1395     }
1396
1397     if multi_line_ret_str {
1398         one_line_budget = 0;
1399     }
1400
1401     // A conservative estimation, to goal is to be over all parens in generics
1402     let args_start = generics.ty_params
1403         .last()
1404         .map_or(span.lo, |tp| end_typaram(tp));
1405     let args_span = mk_sp(context.codemap.span_after(mk_sp(args_start, span.hi), "("),
1406                           span_for_return(&fd.output).lo);
1407     let arg_str = try_opt!(rewrite_args(context,
1408                                         &fd.inputs,
1409                                         fd.get_self().as_ref(),
1410                                         one_line_budget,
1411                                         multi_line_budget,
1412                                         indent,
1413                                         arg_indent,
1414                                         args_span,
1415                                         fd.variadic));
1416
1417     let multi_line_arg_str = arg_str.contains('\n');
1418
1419     let put_args_in_block = match context.config.fn_args_layout {
1420         FnArgLayoutStyle::Block => multi_line_arg_str,
1421         FnArgLayoutStyle::BlockAlways => true,
1422         _ => false,
1423     } && !fd.inputs.is_empty();
1424
1425     if put_args_in_block {
1426         arg_indent = indent.block_indent(context.config);
1427         result.push('\n');
1428         result.push_str(&arg_indent.to_string(context.config));
1429         result.push_str(&arg_str);
1430         result.push('\n');
1431         result.push_str(&indent.to_string(context.config));
1432         result.push(')');
1433     } else {
1434         result.push_str(&arg_str);
1435         result.push(')');
1436     }
1437
1438     // Return type.
1439     if !ret_str.is_empty() {
1440         let ret_should_indent = match context.config.fn_args_layout {
1441             // If our args are block layout then we surely must have space.
1442             FnArgLayoutStyle::Block if put_args_in_block => false,
1443             FnArgLayoutStyle::BlockAlways => false,
1444             _ => {
1445                 // If we've already gone multi-line, or the return type would push over the max
1446                 // width, then put the return type on a new line. With the +1 for the signature
1447                 // length an additional space between the closing parenthesis of the argument and
1448                 // the arrow '->' is considered.
1449                 let mut sig_length = result.len() + indent.width() + ret_str_len + 1;
1450
1451                 // If there is no where clause, take into account the space after the return type
1452                 // and the brace.
1453                 if where_clause.predicates.is_empty() {
1454                     sig_length += 2;
1455                 }
1456
1457                 let overlong_sig = sig_length > context.config.max_width;
1458
1459                 result.contains('\n') || multi_line_ret_str || overlong_sig
1460             }
1461         };
1462         let ret_indent = if ret_should_indent {
1463             let indent = match context.config.fn_return_indent {
1464                 ReturnIndent::WithWhereClause => indent + 4,
1465                 // Aligning with non-existent args looks silly.
1466                 _ if arg_str.is_empty() => {
1467                     force_new_line_for_brace = true;
1468                     indent + 4
1469                 }
1470                 // FIXME: we might want to check that using the arg indent
1471                 // doesn't blow our budget, and if it does, then fallback to
1472                 // the where clause indent.
1473                 _ => arg_indent,
1474             };
1475
1476             result.push('\n');
1477             result.push_str(&indent.to_string(context.config));
1478             indent
1479         } else {
1480             result.push(' ');
1481             Indent::new(indent.width(), result.len())
1482         };
1483
1484         if multi_line_ret_str {
1485             // Now that we know the proper indent and width, we need to
1486             // re-layout the return type.
1487             let budget = try_opt!(context.config.max_width.checked_sub(ret_indent.width()));
1488             let ret_str = try_opt!(fd.output.rewrite(context, budget, ret_indent));
1489             result.push_str(&ret_str);
1490         } else {
1491             result.push_str(&ret_str);
1492         }
1493
1494         // Comment between return type and the end of the decl.
1495         let snippet_lo = fd.output.span().hi;
1496         if where_clause.predicates.is_empty() {
1497             let snippet_hi = span.hi;
1498             let snippet = context.snippet(mk_sp(snippet_lo, snippet_hi));
1499             let snippet = snippet.trim();
1500             if !snippet.is_empty() {
1501                 result.push(' ');
1502                 result.push_str(snippet);
1503             }
1504         } else {
1505             // FIXME it would be nice to catch comments between the return type
1506             // and the where clause, but we don't have a span for the where
1507             // clause.
1508         }
1509     }
1510
1511     let should_compress_where = match context.config.where_density {
1512         Density::Compressed => !result.contains('\n') || put_args_in_block,
1513         Density::CompressedIfEmpty => !has_body && !result.contains('\n'),
1514         _ => false,
1515     } || (put_args_in_block && ret_str.is_empty());
1516
1517     let where_density = if should_compress_where {
1518         Density::Compressed
1519     } else {
1520         Density::Tall
1521     };
1522
1523     // Where clause.
1524     let where_budget = try_opt!(context.config.max_width.checked_sub(last_line_width(&result)));
1525     let where_clause_str = try_opt!(rewrite_where_clause(context,
1526                                                          where_clause,
1527                                                          context.config,
1528                                                          context.config.fn_brace_style,
1529                                                          indent,
1530                                                          where_budget,
1531                                                          where_density,
1532                                                          "{",
1533                                                          has_body,
1534                                                          Some(span.hi)));
1535
1536     if last_line_width(&result) + where_clause_str.len() > context.config.max_width &&
1537        !where_clause_str.contains('\n') {
1538         result.push('\n');
1539     }
1540
1541     result.push_str(&where_clause_str);
1542
1543     Some((result, force_new_line_for_brace))
1544 }
1545
1546 fn rewrite_args(context: &RewriteContext,
1547                 args: &[ast::Arg],
1548                 explicit_self: Option<&ast::ExplicitSelf>,
1549                 one_line_budget: usize,
1550                 multi_line_budget: usize,
1551                 indent: Indent,
1552                 arg_indent: Indent,
1553                 span: Span,
1554                 variadic: bool)
1555                 -> Option<String> {
1556     let mut arg_item_strs = try_opt!(args.iter()
1557         .map(|arg| arg.rewrite(&context, multi_line_budget, arg_indent))
1558         .collect::<Option<Vec<_>>>());
1559
1560     // Account for sugary self.
1561     // FIXME: the comment for the self argument is dropped. This is blocked
1562     // on rust issue #27522.
1563     let min_args =
1564         explicit_self.and_then(|explicit_self| rewrite_explicit_self(explicit_self, args, context))
1565             .map_or(1, |self_str| {
1566                 arg_item_strs[0] = self_str;
1567                 2
1568             });
1569
1570     // Comments between args.
1571     let mut arg_items = Vec::new();
1572     if min_args == 2 {
1573         arg_items.push(ListItem::from_str(""));
1574     }
1575
1576     // FIXME(#21): if there are no args, there might still be a comment, but
1577     // without spans for the comment or parens, there is no chance of
1578     // getting it right. You also don't get to put a comment on self, unless
1579     // it is explicit.
1580     if args.len() >= min_args || variadic {
1581         let comment_span_start = if min_args == 2 {
1582             let second_arg_start = if arg_has_pattern(&args[1]) {
1583                 args[1].pat.span.lo
1584             } else {
1585                 args[1].ty.span.lo
1586             };
1587             let reduced_span = mk_sp(span.lo, second_arg_start);
1588
1589             context.codemap.span_after_last(reduced_span, ",")
1590         } else {
1591             span.lo
1592         };
1593
1594         enum ArgumentKind<'a> {
1595             Regular(&'a ast::Arg),
1596             Variadic(BytePos),
1597         }
1598
1599         let variadic_arg = if variadic {
1600             let variadic_span = mk_sp(args.last().unwrap().ty.span.hi, span.hi);
1601             let variadic_start = context.codemap.span_after(variadic_span, "...") - BytePos(3);
1602             Some(ArgumentKind::Variadic(variadic_start))
1603         } else {
1604             None
1605         };
1606
1607         let more_items = itemize_list(context.codemap,
1608                                       args[min_args - 1..]
1609                                           .iter()
1610                                           .map(ArgumentKind::Regular)
1611                                           .chain(variadic_arg),
1612                                       ")",
1613                                       |arg| {
1614                                           match *arg {
1615                                               ArgumentKind::Regular(arg) => span_lo_for_arg(arg),
1616                                               ArgumentKind::Variadic(start) => start,
1617                                           }
1618                                       },
1619                                       |arg| {
1620                                           match *arg {
1621                                               ArgumentKind::Regular(arg) => arg.ty.span.hi,
1622                                               ArgumentKind::Variadic(start) => start + BytePos(3),
1623                                           }
1624                                       },
1625                                       |arg| {
1626                                           match *arg {
1627                                               ArgumentKind::Regular(..) => None,
1628                                               ArgumentKind::Variadic(..) => Some("...".to_owned()),
1629                                           }
1630                                       },
1631                                       comment_span_start,
1632                                       span.hi);
1633
1634         arg_items.extend(more_items);
1635     }
1636
1637     for (item, arg) in arg_items.iter_mut().zip(arg_item_strs) {
1638         item.item = Some(arg);
1639     }
1640
1641     let indent = match context.config.fn_arg_indent {
1642         BlockIndentStyle::Inherit => indent,
1643         BlockIndentStyle::Tabbed => indent.block_indent(context.config),
1644         BlockIndentStyle::Visual => arg_indent,
1645     };
1646
1647     let tactic = definitive_tactic(&arg_items,
1648                                    context.config.fn_args_density.to_list_tactic(),
1649                                    one_line_budget);
1650     let budget = match tactic {
1651         DefinitiveListTactic::Horizontal => one_line_budget,
1652         _ => multi_line_budget,
1653     };
1654
1655     debug!("rewrite_args: budget: {}, tactic: {:?}", budget, tactic);
1656
1657     let end_with_newline = match context.config.fn_args_layout {
1658         FnArgLayoutStyle::Block |
1659         FnArgLayoutStyle::BlockAlways => true,
1660         _ => false,
1661     };
1662
1663     let fmt = ListFormatting {
1664         tactic: tactic,
1665         separator: ",",
1666         trailing_separator: SeparatorTactic::Never,
1667         indent: indent,
1668         width: budget,
1669         ends_with_newline: end_with_newline,
1670         config: context.config,
1671     };
1672
1673     write_list(&arg_items, &fmt)
1674 }
1675
1676 fn arg_has_pattern(arg: &ast::Arg) -> bool {
1677     if let ast::PatKind::Ident(_,
1678                                codemap::Spanned {
1679                                    node: ast::Ident { name: ast::Name(0u32), .. },
1680                                    ..
1681                                },
1682                                _) = arg.pat.node {
1683         false
1684     } else {
1685         true
1686     }
1687 }
1688
1689 fn compute_budgets_for_args(context: &RewriteContext,
1690                             result: &str,
1691                             indent: Indent,
1692                             ret_str_len: usize,
1693                             newline_brace: bool)
1694                             -> Option<((usize, usize, Indent))> {
1695     // Try keeping everything on the same line.
1696     if !result.contains('\n') {
1697         // 3 = `() `, space is before ret_string.
1698         let mut used_space = indent.width() + result.len() + ret_str_len + 3;
1699         if !newline_brace {
1700             used_space += 2;
1701         }
1702         let one_line_budget = context.config.max_width.checked_sub(used_space).unwrap_or(0);
1703
1704         if one_line_budget > 0 {
1705             // 4 = "() {".len()
1706             let multi_line_budget =
1707                 try_opt!(context.config.max_width.checked_sub(indent.width() + result.len() + 4));
1708
1709             return Some((one_line_budget, multi_line_budget, indent + result.len() + 1));
1710         }
1711     }
1712
1713     // Didn't work. we must force vertical layout and put args on a newline.
1714     let new_indent = indent.block_indent(context.config);
1715     let used_space = new_indent.width() + 4; // Account for `(` and `)` and possibly ` {`.
1716     let max_space = context.config.max_width;
1717     if used_space <= max_space {
1718         Some((0, max_space - used_space, new_indent))
1719     } else {
1720         // Whoops! bankrupt.
1721         None
1722     }
1723 }
1724
1725 fn newline_for_brace(config: &Config, where_clause: &ast::WhereClause) -> bool {
1726     match config.fn_brace_style {
1727         BraceStyle::AlwaysNextLine => true,
1728         BraceStyle::SameLineWhere if !where_clause.predicates.is_empty() => true,
1729         _ => false,
1730     }
1731 }
1732
1733 fn rewrite_generics(context: &RewriteContext,
1734                     generics: &ast::Generics,
1735                     offset: Indent,
1736                     width: usize,
1737                     generics_offset: Indent,
1738                     span: Span)
1739                     -> Option<String> {
1740     // FIXME: convert bounds to where clauses where they get too big or if
1741     // there is a where clause at all.
1742     let lifetimes: &[_] = &generics.lifetimes;
1743     let tys: &[_] = &generics.ty_params;
1744     if lifetimes.is_empty() && tys.is_empty() {
1745         return Some(String::new());
1746     }
1747
1748     let offset = match context.config.generics_indent {
1749         BlockIndentStyle::Inherit => offset,
1750         BlockIndentStyle::Tabbed => offset.block_indent(context.config),
1751         // 1 = <
1752         BlockIndentStyle::Visual => generics_offset + 1,
1753     };
1754
1755     let h_budget = try_opt!(width.checked_sub(generics_offset.width() + 2));
1756     // FIXME: might need to insert a newline if the generics are really long.
1757
1758     // Strings for the generics.
1759     let lt_strs = lifetimes.iter().map(|lt| lt.rewrite(context, h_budget, offset));
1760     let ty_strs = tys.iter().map(|ty_param| ty_param.rewrite(context, h_budget, offset));
1761
1762     // Extract comments between generics.
1763     let lt_spans = lifetimes.iter().map(|l| {
1764         let hi = if l.bounds.is_empty() {
1765             l.lifetime.span.hi
1766         } else {
1767             l.bounds[l.bounds.len() - 1].span.hi
1768         };
1769         mk_sp(l.lifetime.span.lo, hi)
1770     });
1771     let ty_spans = tys.iter().map(span_for_ty_param);
1772
1773     let items = itemize_list(context.codemap,
1774                              lt_spans.chain(ty_spans).zip(lt_strs.chain(ty_strs)),
1775                              ">",
1776                              |&(sp, _)| sp.lo,
1777                              |&(sp, _)| sp.hi,
1778                              // FIXME: don't clone
1779                              |&(_, ref str)| str.clone(),
1780                              context.codemap.span_after(span, "<"),
1781                              span.hi);
1782     let list_str = try_opt!(format_item_list(items, h_budget, offset, context.config));
1783
1784     Some(format!("<{}>", list_str))
1785 }
1786
1787 fn rewrite_trait_bounds(context: &RewriteContext,
1788                         type_param_bounds: &ast::TyParamBounds,
1789                         indent: Indent,
1790                         width: usize)
1791                         -> Option<String> {
1792     let bounds: &[_] = type_param_bounds;
1793
1794     if bounds.is_empty() {
1795         return Some(String::new());
1796     }
1797
1798     let bound_str = try_opt!(bounds.iter()
1799         .map(|ty_bound| ty_bound.rewrite(&context, width, indent))
1800         .intersperse(Some(" + ".to_string()))
1801         .collect::<Option<String>>());
1802
1803     let mut result = String::new();
1804     result.push_str(": ");
1805     result.push_str(&bound_str);
1806     Some(result)
1807 }
1808
1809 fn rewrite_where_clause(context: &RewriteContext,
1810                         where_clause: &ast::WhereClause,
1811                         config: &Config,
1812                         brace_style: BraceStyle,
1813                         indent: Indent,
1814                         width: usize,
1815                         density: Density,
1816                         terminator: &str,
1817                         allow_trailing_comma: bool,
1818                         span_end: Option<BytePos>)
1819                         -> Option<String> {
1820     if where_clause.predicates.is_empty() {
1821         return Some(String::new());
1822     }
1823
1824     let extra_indent = match context.config.where_indent {
1825         BlockIndentStyle::Inherit => Indent::empty(),
1826         BlockIndentStyle::Tabbed | BlockIndentStyle::Visual => Indent::new(config.tab_spaces, 0),
1827     };
1828
1829     let offset = match context.config.where_pred_indent {
1830         BlockIndentStyle::Inherit => indent + extra_indent,
1831         BlockIndentStyle::Tabbed => indent + extra_indent.block_indent(config),
1832         // 6 = "where ".len()
1833         BlockIndentStyle::Visual => indent + extra_indent + 6,
1834     };
1835     // FIXME: if where_pred_indent != Visual, then the budgets below might
1836     // be out by a char or two.
1837
1838     let budget = context.config.max_width - offset.width();
1839     let span_start = span_for_where_pred(&where_clause.predicates[0]).lo;
1840     // If we don't have the start of the next span, then use the end of the
1841     // predicates, but that means we miss comments.
1842     let len = where_clause.predicates.len();
1843     let end_of_preds = span_for_where_pred(&where_clause.predicates[len - 1]).hi;
1844     let span_end = span_end.unwrap_or(end_of_preds);
1845     let items = itemize_list(context.codemap,
1846                              where_clause.predicates.iter(),
1847                              terminator,
1848                              |pred| span_for_where_pred(pred).lo,
1849                              |pred| span_for_where_pred(pred).hi,
1850                              |pred| pred.rewrite(context, budget, offset),
1851                              span_start,
1852                              span_end);
1853     let item_vec = items.collect::<Vec<_>>();
1854     // FIXME: we don't need to collect here if the where_layout isn't
1855     // HorizontalVertical.
1856     let tactic = definitive_tactic(&item_vec, context.config.where_layout, budget);
1857     let use_trailing_comma = allow_trailing_comma && context.config.where_trailing_comma;
1858
1859     let fmt = ListFormatting {
1860         tactic: tactic,
1861         separator: ",",
1862         trailing_separator: SeparatorTactic::from_bool(use_trailing_comma),
1863         indent: offset,
1864         width: budget,
1865         ends_with_newline: true,
1866         config: context.config,
1867     };
1868     let preds_str = try_opt!(write_list(&item_vec, &fmt));
1869
1870     let end_length = if terminator == "{" {
1871         // If the brace is on the next line we don't need to count it otherwise it needs two
1872         // characters " {"
1873         match brace_style {
1874             BraceStyle::AlwaysNextLine |
1875             BraceStyle::SameLineWhere => 0,
1876             BraceStyle::PreferSameLine => 2,
1877         }
1878     } else if terminator == "=" {
1879         2
1880     } else {
1881         terminator.len()
1882     };
1883     if density == Density::Tall || preds_str.contains('\n') ||
1884        indent.width() + " where ".len() + preds_str.len() + end_length > width {
1885         Some(format!("\n{}where {}",
1886                      (indent + extra_indent).to_string(context.config),
1887                      preds_str))
1888     } else {
1889         Some(format!(" where {}", preds_str))
1890     }
1891 }
1892
1893 fn format_header(item_name: &str, ident: ast::Ident, vis: &ast::Visibility) -> String {
1894     format!("{}{}{}", format_visibility(vis), item_name, ident)
1895 }
1896
1897 fn format_generics(context: &RewriteContext,
1898                    generics: &ast::Generics,
1899                    opener: &str,
1900                    terminator: &str,
1901                    brace_style: BraceStyle,
1902                    force_same_line_brace: bool,
1903                    offset: Indent,
1904                    generics_offset: Indent,
1905                    span: Span)
1906                    -> Option<String> {
1907     let mut result = try_opt!(rewrite_generics(context,
1908                                                generics,
1909                                                offset,
1910                                                context.config.max_width,
1911                                                generics_offset,
1912                                                span));
1913
1914     if !generics.where_clause.predicates.is_empty() || result.contains('\n') {
1915         let budget = try_opt!(context.config.max_width.checked_sub(last_line_width(&result)));
1916         let where_clause_str = try_opt!(rewrite_where_clause(context,
1917                                                              &generics.where_clause,
1918                                                              context.config,
1919                                                              brace_style,
1920                                                              context.block_indent,
1921                                                              budget,
1922                                                              Density::Tall,
1923                                                              terminator,
1924                                                              true,
1925                                                              Some(span.hi)));
1926         result.push_str(&where_clause_str);
1927         if !force_same_line_brace &&
1928            (brace_style == BraceStyle::SameLineWhere || brace_style == BraceStyle::AlwaysNextLine) {
1929             result.push('\n');
1930             result.push_str(&context.block_indent.to_string(context.config));
1931         } else {
1932             result.push(' ');
1933         }
1934         result.push_str(opener);
1935     } else {
1936         if !force_same_line_brace && brace_style == BraceStyle::AlwaysNextLine {
1937             result.push('\n');
1938             result.push_str(&context.block_indent.to_string(context.config));
1939         } else {
1940             result.push(' ');
1941         }
1942         result.push_str(opener);
1943     }
1944
1945     Some(result)
1946 }