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::borrow::Cow;
  14 use std::cmp::min;
  15
  16 use syntax::{abi, ast, ptr, symbol};
  17 use syntax::ast::{CrateSugar, ImplItem};
  18 use syntax::codemap::{BytePos, Span};
  19 use syntax::visit;
  20
  21 use spanned::Spanned;
  22 use codemap::{LineRangeUtils, SpanUtils};
  23 use comment::{combine_strs_with_missing_comments, contains_comment, recover_comment_removed,
  24               recover_missing_comment_in_span, rewrite_missing_comment, FindUncommented};
  25 use config::{BraceStyle, Config, Density, IndentStyle, ReturnIndent, Style};
  26 use expr::{format_expr, is_empty_block, is_simple_block_stmt, rewrite_assign_rhs,
  27            rewrite_call_inner, ExprType};
  28 use lists::{definitive_tactic, itemize_list, write_list, DefinitiveListTactic, ListFormatting,
  29             ListItem, ListTactic, Separator, SeparatorPlace, SeparatorTactic};
  30 use rewrite::{Rewrite, RewriteContext};
  31 use shape::{Indent, Shape};
  32 use types::join_bounds;
  33 use utils::{colon_spaces, contains_skip, end_typaram, first_line_width, format_abi,
  34             format_constness, format_defaultness, format_mutability, format_unsafety,
  35             format_visibility, is_attributes_extendable, last_line_contains_single_line_comment,
  36             last_line_used_width, last_line_width, mk_sp, semicolon_for_expr, starts_with_newline,
  37             stmt_expr, trim_newlines, trimmed_last_line_width};
  38 use vertical::rewrite_with_alignment;
  39 use visitor::FmtVisitor;
  40
  41 fn type_annotation_separator(config: &Config) -> &str {
  42     colon_spaces(
  43         config.space_before_type_annotation(),
  44         config.space_after_type_annotation_colon(),
  45     )
  46 }
  47
  48 // Statements of the form
  49 // let pat: ty = init;
  50 impl Rewrite for ast::Local {
  51     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
  52         debug!(
  53             "Local::rewrite {:?} {} {:?}",
  54             self,
  55             shape.width,
  56             shape.indent
  57         );
  58
  59         skip_out_of_file_lines_range!(context, self.span);
  60
  61         if contains_skip(&self.attrs) {
  62             return None;
  63         }
  64
  65         let attrs_str = self.attrs.rewrite(context, shape)?;
  66         let mut result = if attrs_str.is_empty() {
  67             "let ".to_owned()
  68         } else {
  69             combine_strs_with_missing_comments(
  70                 context,
  71                 &attrs_str,
  72                 "let ",
  73                 mk_sp(
  74                     self.attrs.last().map(|a| a.span.hi()).unwrap(),
  75                     self.span.lo(),
  76                 ),
  77                 shape,
  78                 false,
  79             )?
  80         };
  81
  82         // 4 = "let ".len()
  83         let pat_shape = shape.offset_left(4)?;
  84         // 1 = ;
  85         let pat_shape = pat_shape.sub_width(1)?;
  86         let pat_str = self.pat.rewrite(context, pat_shape)?;
  87         result.push_str(&pat_str);
  88
  89         // String that is placed within the assignment pattern and expression.
  90         let infix = {
  91             let mut infix = String::with_capacity(32);
  92
  93             if let Some(ref ty) = self.ty {
  94                 let separator = type_annotation_separator(context.config);
  95                 let indent = shape.indent + last_line_width(&result) + separator.len();
  96                 // 1 = ;
  97                 let budget = shape.width.checked_sub(indent.width() + 1)?;
  98                 let rewrite = ty.rewrite(context, Shape::legacy(budget, indent))?;
  99
 100                 infix.push_str(separator);
 101                 infix.push_str(&rewrite);
 102             }
 103
 104             if self.init.is_some() {
 105                 infix.push_str(" =");
 106             }
 107
 108             infix
 109         };
 110
 111         result.push_str(&infix);
 112
 113         if let Some(ref ex) = self.init {
 114             // 1 = trailing semicolon;
 115             let nested_shape = shape.sub_width(1)?;
 116
 117             result = rewrite_assign_rhs(context, result, ex, nested_shape)?;
 118         }
 119
 120         result.push(';');
 121         Some(result)
 122     }
 123 }
 124
 125 // TODO convert to using rewrite style rather than visitor
 126 // TODO format modules in this style
 127 #[allow(dead_code)]
 128 struct Item<'a> {
 129     keyword: &'static str,
 130     abi: Cow<'static, str>,
 131     vis: Option<&'a ast::Visibility>,
 132     body: Vec<BodyElement<'a>>,
 133     span: Span,
 134 }
 135
 136 impl<'a> Item<'a> {
 137     fn from_foreign_mod(fm: &'a ast::ForeignMod, span: Span, config: &Config) -> Item<'a> {
 138         Item {
 139             keyword: "",
 140             abi: format_abi(fm.abi, config.force_explicit_abi(), true),
 141             vis: None,
 142             body: fm.items
 143                 .iter()
 144                 .map(|i| BodyElement::ForeignItem(i))
 145                 .collect(),
 146             span: span,
 147         }
 148     }
 149 }
 150
 151 enum BodyElement<'a> {
 152     // Stmt(&'a ast::Stmt),
 153     // Field(&'a ast::Field),
 154     // Variant(&'a ast::Variant),
 155     // Item(&'a ast::Item),
 156     ForeignItem(&'a ast::ForeignItem),
 157 }
 158
 159 /// Represents a fn's signature.
 160 pub struct FnSig<'a> {
 161     decl: &'a ast::FnDecl,
 162     generics: &'a ast::Generics,
 163     abi: abi::Abi,
 164     constness: ast::Constness,
 165     defaultness: ast::Defaultness,
 166     unsafety: ast::Unsafety,
 167     visibility: ast::Visibility,
 168 }
 169
 170 impl<'a> FnSig<'a> {
 171     pub fn new(
 172         decl: &'a ast::FnDecl,
 173         generics: &'a ast::Generics,
 174         vis: ast::Visibility,
 175     ) -> FnSig<'a> {
 176         FnSig {
 177             decl: decl,
 178             generics: generics,
 179             abi: abi::Abi::Rust,
 180             constness: ast::Constness::NotConst,
 181             defaultness: ast::Defaultness::Final,
 182             unsafety: ast::Unsafety::Normal,
 183             visibility: vis,
 184         }
 185     }
 186
 187     pub fn from_method_sig(
 188         method_sig: &'a ast::MethodSig,
 189         generics: &'a ast::Generics,
 190     ) -> FnSig<'a> {
 191         FnSig {
 192             unsafety: method_sig.unsafety,
 193             constness: method_sig.constness.node,
 194             defaultness: ast::Defaultness::Final,
 195             abi: method_sig.abi,
 196             decl: &*method_sig.decl,
 197             generics: generics,
 198             visibility: ast::Visibility::Inherited,
 199         }
 200     }
 201
 202     pub fn from_fn_kind(
 203         fn_kind: &'a visit::FnKind,
 204         generics: &'a ast::Generics,
 205         decl: &'a ast::FnDecl,
 206         defualtness: ast::Defaultness,
 207     ) -> FnSig<'a> {
 208         match *fn_kind {
 209             visit::FnKind::ItemFn(_, unsafety, constness, abi, visibility, _) => FnSig {
 210                 decl: decl,
 211                 generics: generics,
 212                 abi: abi,
 213                 constness: constness.node,
 214                 defaultness: defualtness,
 215                 unsafety: unsafety,
 216                 visibility: visibility.clone(),
 217             },
 218             visit::FnKind::Method(_, method_sig, vis, _) => {
 219                 let mut fn_sig = FnSig::from_method_sig(method_sig, generics);
 220                 fn_sig.defaultness = defualtness;
 221                 if let Some(vis) = vis {
 222                     fn_sig.visibility = vis.clone();
 223                 }
 224                 fn_sig
 225             }
 226             _ => unreachable!(),
 227         }
 228     }
 229
 230     fn to_str(&self, context: &RewriteContext) -> String {
 231         let mut result = String::with_capacity(128);
 232         // Vis defaultness constness unsafety abi.
 233         result.push_str(&*format_visibility(&self.visibility));
 234         result.push_str(format_defaultness(self.defaultness));
 235         result.push_str(format_constness(self.constness));
 236         result.push_str(format_unsafety(self.unsafety));
 237         result.push_str(&format_abi(
 238             self.abi,
 239             context.config.force_explicit_abi(),
 240             false,
 241         ));
 242         result
 243     }
 244 }
 245
 246 impl<'a> FmtVisitor<'a> {
 247     fn format_item(&mut self, item: Item) {
 248         self.buffer.push_str(&item.abi);
 249
 250         let snippet = self.snippet(item.span);
 251         let brace_pos = snippet.find_uncommented("{").unwrap();
 252
 253         self.buffer.push_str("{");
 254         if !item.body.is_empty() || contains_comment(&snippet[brace_pos..]) {
 255             // FIXME: this skips comments between the extern keyword and the opening
 256             // brace.
 257             self.last_pos = item.span.lo() + BytePos(brace_pos as u32 + 1);
 258             self.block_indent = self.block_indent.block_indent(self.config);
 259
 260             if item.body.is_empty() {
 261                 self.format_missing_no_indent(item.span.hi() - BytePos(1));
 262                 self.block_indent = self.block_indent.block_unindent(self.config);
 263
 264                 self.buffer
 265                     .push_str(&self.block_indent.to_string(self.config));
 266             } else {
 267                 for item in &item.body {
 268                     self.format_body_element(item);
 269                 }
 270
 271                 self.block_indent = self.block_indent.block_unindent(self.config);
 272                 self.format_missing_with_indent(item.span.hi() - BytePos(1));
 273             }
 274         }
 275
 276         self.buffer.push_str("}");
 277         self.last_pos = item.span.hi();
 278     }
 279
 280     fn format_body_element(&mut self, element: &BodyElement) {
 281         match *element {
 282             BodyElement::ForeignItem(item) => self.format_foreign_item(item),
 283         }
 284     }
 285
 286     pub fn format_foreign_mod(&mut self, fm: &ast::ForeignMod, span: Span) {
 287         let item = Item::from_foreign_mod(fm, span, self.config);
 288         self.format_item(item);
 289     }
 290
 291
 292     fn format_foreign_item(&mut self, item: &ast::ForeignItem) {
 293         let rewrite = item.rewrite(&self.get_context(), self.shape());
 294         self.push_rewrite(item.span(), rewrite);
 295         self.last_pos = item.span.hi();
 296     }
 297
 298     pub fn rewrite_fn(
 299         &mut self,
 300         indent: Indent,
 301         ident: ast::Ident,
 302         fn_sig: &FnSig,
 303         span: Span,
 304         block: &ast::Block,
 305     ) -> Option<String> {
 306         let context = self.get_context();
 307
 308         let has_body =
 309             !is_empty_block(block, self.codemap) || !context.config.fn_empty_single_line();
 310         let mut newline_brace =
 311             newline_for_brace(self.config, &fn_sig.generics.where_clause, has_body);
 312
 313         let (mut result, force_newline_brace) =
 314             rewrite_fn_base(&context, indent, ident, fn_sig, span, newline_brace, true)?;
 315
 316         // 2 = ` {`
 317         if self.config.fn_brace_style() == BraceStyle::AlwaysNextLine || force_newline_brace
 318             || last_line_width(&result) + 2 > self.shape().width
 319         {
 320             newline_brace = true;
 321         } else if !result.contains('\n') {
 322             newline_brace = false;
 323         }
 324
 325         // Prepare for the function body by possibly adding a newline and
 326         // indent.
 327         // FIXME we'll miss anything between the end of the signature and the
 328         // start of the body, but we need more spans from the compiler to solve
 329         // this.
 330         if newline_brace {
 331             result.push('\n');
 332             result.push_str(&indent.to_string(self.config));
 333         } else {
 334             result.push(' ');
 335         }
 336
 337         self.single_line_fn(&result, block).or_else(|| Some(result))
 338     }
 339
 340     pub fn rewrite_required_fn(
 341         &mut self,
 342         indent: Indent,
 343         ident: ast::Ident,
 344         sig: &ast::MethodSig,
 345         generics: &ast::Generics,
 346         span: Span,
 347     ) -> Option<String> {
 348         // Drop semicolon or it will be interpreted as comment.
 349         let span = mk_sp(span.lo(), span.hi() - BytePos(1));
 350         let context = self.get_context();
 351
 352         let (mut result, _) = rewrite_fn_base(
 353             &context,
 354             indent,
 355             ident,
 356             &FnSig::from_method_sig(sig, generics),
 357             span,
 358             false,
 359             false,
 360         )?;
 361
 362         // Re-attach semicolon
 363         result.push(';');
 364
 365         Some(result)
 366     }
 367
 368     fn single_line_fn(&self, fn_str: &str, block: &ast::Block) -> Option<String> {
 369         if fn_str.contains('\n') {
 370             return None;
 371         }
 372
 373         let codemap = self.get_context().codemap;
 374
 375         if self.config.fn_empty_single_line() && is_empty_block(block, codemap)
 376             && self.block_indent.width() + fn_str.len() + 2 <= self.config.max_width()
 377         {
 378             return Some(format!("{}{{}}", fn_str));
 379         }
 380
 381         if self.config.fn_single_line() && is_simple_block_stmt(block, codemap) {
 382             let rewrite = {
 383                 if let Some(stmt) = block.stmts.first() {
 384                     match stmt_expr(stmt) {
 385                         Some(e) => {
 386                             let suffix = if semicolon_for_expr(&self.get_context(), e) {
 387                                 ";"
 388                             } else {
 389                                 ""
 390                             };
 391
 392                             format_expr(e, ExprType::Statement, &self.get_context(), self.shape())
 393                                 .map(|s| s + suffix)
 394                                 .or_else(|| Some(self.snippet(e.span)))
 395                         }
 396                         None => stmt.rewrite(&self.get_context(), self.shape()),
 397                     }
 398                 } else {
 399                     None
 400                 }
 401             };
 402
 403             if let Some(res) = rewrite {
 404                 let width = self.block_indent.width() + fn_str.len() + res.len() + 4;
 405                 if !res.contains('\n') && width <= self.config.max_width() {
 406                     return Some(format!("{}{{ {} }}", fn_str, res));
 407                 }
 408             }
 409         }
 410
 411         None
 412     }
 413
 414     pub fn visit_static(&mut self, static_parts: &StaticParts) {
 415         let rewrite = rewrite_static(&self.get_context(), static_parts, self.block_indent);
 416         self.push_rewrite(static_parts.span, rewrite);
 417     }
 418
 419     pub fn visit_struct(&mut self, struct_parts: &StructParts) {
 420         let is_tuple = struct_parts.def.is_tuple();
 421         let rewrite = format_struct(&self.get_context(), struct_parts, self.block_indent, None)
 422             .map(|s| if is_tuple { s + ";" } else { s });
 423         self.push_rewrite(struct_parts.span, rewrite);
 424     }
 425
 426     pub fn visit_enum(
 427         &mut self,
 428         ident: ast::Ident,
 429         vis: &ast::Visibility,
 430         enum_def: &ast::EnumDef,
 431         generics: &ast::Generics,
 432         span: Span,
 433     ) {
 434         let enum_header = format_header("enum ", ident, vis);
 435         self.buffer.push_str(&enum_header);
 436
 437         let enum_snippet = self.snippet(span);
 438         let brace_pos = enum_snippet.find_uncommented("{").unwrap();
 439         let body_start = span.lo() + BytePos(brace_pos as u32 + 1);
 440         let generics_str = format_generics(
 441             &self.get_context(),
 442             generics,
 443             self.config.item_brace_style(),
 444             enum_def.variants.is_empty(),
 445             self.block_indent,
 446             mk_sp(span.lo(), body_start),
 447             last_line_width(&enum_header),
 448         ).unwrap();
 449         self.buffer.push_str(&generics_str);
 450
 451         self.last_pos = body_start;
 452
 453         self.block_indent = self.block_indent.block_indent(self.config);
 454         let variant_list = self.format_variant_list(enum_def, body_start, span.hi() - BytePos(1));
 455         match variant_list {
 456             Some(ref body_str) => self.buffer.push_str(body_str),
 457             None => if contains_comment(&enum_snippet[brace_pos..]) {
 458                 self.format_missing_no_indent(span.hi() - BytePos(1))
 459             },
 460         }
 461         self.block_indent = self.block_indent.block_unindent(self.config);
 462
 463         if variant_list.is_some() || contains_comment(&enum_snippet[brace_pos..]) {
 464             self.buffer
 465                 .push_str(&self.block_indent.to_string(self.config));
 466         }
 467         self.buffer.push_str("}");
 468         self.last_pos = span.hi();
 469     }
 470
 471     // Format the body of an enum definition
 472     fn format_variant_list(
 473         &self,
 474         enum_def: &ast::EnumDef,
 475         body_lo: BytePos,
 476         body_hi: BytePos,
 477     ) -> Option<String> {
 478         if enum_def.variants.is_empty() {
 479             return None;
 480         }
 481         let mut result = String::with_capacity(1024);
 482         result.push('\n');
 483         let indentation = self.block_indent.to_string(self.config);
 484         result.push_str(&indentation);
 485
 486         let items = itemize_list(
 487             self.codemap,
 488             enum_def.variants.iter(),
 489             "}",
 490             |f| if !f.node.attrs.is_empty() {
 491                 f.node.attrs[0].span.lo()
 492             } else {
 493                 f.span.lo()
 494             },
 495             |f| f.span.hi(),
 496             |f| self.format_variant(f),
 497             body_lo,
 498             body_hi,
 499             false,
 500         );
 501
 502         let shape = self.shape().sub_width(2).unwrap();
 503         let fmt = ListFormatting {
 504             tactic: DefinitiveListTactic::Vertical,
 505             separator: ",",
 506             trailing_separator: self.config.trailing_comma(),
 507             separator_place: SeparatorPlace::Back,
 508             shape: shape,
 509             ends_with_newline: true,
 510             preserve_newline: true,
 511             config: self.config,
 512         };
 513
 514         let list = write_list(&items.collect::<Vec<_>>(), &fmt)?;
 515         result.push_str(&list);
 516         result.push('\n');
 517         Some(result)
 518     }
 519
 520     // Variant of an enum.
 521     fn format_variant(&self, field: &ast::Variant) -> Option<String> {
 522         if contains_skip(&field.node.attrs) {
 523             let lo = field.node.attrs[0].span.lo();
 524             let span = mk_sp(lo, field.span.hi());
 525             return Some(self.snippet(span));
 526         }
 527
 528         let context = self.get_context();
 529         let indent = self.block_indent;
 530         let shape = self.shape();
 531         let attrs_str = field.node.attrs.rewrite(&context, shape)?;
 532         let lo = field
 533             .node
 534             .attrs
 535             .last()
 536             .map_or(field.span.lo(), |attr| attr.span.hi());
 537         let span = mk_sp(lo, field.span.lo());
 538
 539         let variant_body = match field.node.data {
 540             ast::VariantData::Tuple(..) | ast::VariantData::Struct(..) => {
 541                 // FIXME: Should limit the width, as we have a trailing comma
 542                 format_struct(
 543                     &context,
 544                     &StructParts::from_variant(field),
 545                     indent,
 546                     Some(self.config.struct_variant_width()),
 547                 )?
 548             }
 549             ast::VariantData::Unit(..) => if let Some(ref expr) = field.node.disr_expr {
 550                 let lhs = format!("{} =", field.node.name);
 551                 // 1 = ','
 552                 rewrite_assign_rhs(&context, lhs, expr, shape.sub_width(1)?)?
 553             } else {
 554                 field.node.name.to_string()
 555             },
 556         };
 557
 558         let attrs_extendable = attrs_str.is_empty()
 559             || (context.config.attributes_on_same_line_as_variant()
 560                 && is_attributes_extendable(&attrs_str));
 561         combine_strs_with_missing_comments(
 562             &context,
 563             &attrs_str,
 564             &variant_body,
 565             span,
 566             shape,
 567             attrs_extendable,
 568         )
 569     }
 570 }
 571
 572 pub fn format_impl(
 573     context: &RewriteContext,
 574     item: &ast::Item,
 575     offset: Indent,
 576     where_span_end: Option<BytePos>,
 577 ) -> Option<String> {
 578     if let ast::ItemKind::Impl(_, _, _, ref generics, _, ref self_ty, ref items) = item.node {
 579         let mut result = String::with_capacity(128);
 580         let ref_and_type = format_impl_ref_and_type(context, item, offset)?;
 581         let indent_str = offset.to_string(context.config);
 582         let sep = format!("\n{}", &indent_str);
 583         result.push_str(&ref_and_type);
 584
 585         let where_budget = if result.contains('\n') {
 586             context.config.max_width()
 587         } else {
 588             context.budget(last_line_width(&result))
 589         };
 590         let option = WhereClauseOption::snuggled(&ref_and_type);
 591         let where_clause_str = rewrite_where_clause(
 592             context,
 593             &generics.where_clause,
 594             context.config.item_brace_style(),
 595             Shape::legacy(where_budget, offset.block_only()),
 596             context.config.where_density(),
 597             "{",
 598             where_span_end,
 599             self_ty.span.hi(),
 600             option,
 601             false,
 602         )?;
 603
 604         // If there is no where clause, we may have missing comments between the trait name and
 605         // the opening brace.
 606         if generics.where_clause.predicates.is_empty() {
 607             if let Some(hi) = where_span_end {
 608                 match recover_missing_comment_in_span(
 609                     mk_sp(self_ty.span.hi(), hi),
 610                     Shape::indented(offset, context.config),
 611                     context,
 612                     last_line_width(&result),
 613                 ) {
 614                     Some(ref missing_comment) if !missing_comment.is_empty() => {
 615                         result.push_str(missing_comment);
 616                     }
 617                     _ => (),
 618                 }
 619             }
 620         }
 621
 622         if is_impl_single_line(context, items, &result, &where_clause_str, item)? {
 623             result.push_str(&where_clause_str);
 624             if where_clause_str.contains('\n') || last_line_contains_single_line_comment(&result) {
 625                 result.push_str(&format!("{}{{{}}}", &sep, &sep));
 626             } else {
 627                 result.push_str(" {}");
 628             }
 629             return Some(result);
 630         }
 631
 632         if !where_clause_str.is_empty() && !where_clause_str.contains('\n') {
 633             result.push('\n');
 634             let width = offset.block_indent + context.config.tab_spaces() - 1;
 635             let where_indent = Indent::new(0, width);
 636             result.push_str(&where_indent.to_string(context.config));
 637         }
 638         result.push_str(&where_clause_str);
 639
 640         match context.config.item_brace_style() {
 641             _ if last_line_contains_single_line_comment(&result) => result.push_str(&sep),
 642             BraceStyle::AlwaysNextLine => result.push_str(&sep),
 643             BraceStyle::PreferSameLine => result.push(' '),
 644             BraceStyle::SameLineWhere => if !where_clause_str.is_empty() {
 645                 result.push_str(&sep);
 646             } else {
 647                 result.push(' ');
 648             },
 649         }
 650
 651         result.push('{');
 652
 653         let snippet = context.snippet(item.span);
 654         let open_pos = snippet.find_uncommented("{")? + 1;
 655
 656         if !items.is_empty() || contains_comment(&snippet[open_pos..]) {
 657             let mut visitor = FmtVisitor::from_codemap(context.parse_session, context.config);
 658             visitor.block_indent = offset.block_only().block_indent(context.config);
 659             visitor.last_pos = item.span.lo() + BytePos(open_pos as u32);
 660
 661             visitor.visit_attrs(&item.attrs, ast::AttrStyle::Inner);
 662             for item in items {
 663                 visitor.visit_impl_item(item);
 664             }
 665
 666             visitor.format_missing(item.span.hi() - BytePos(1));
 667
 668             let inner_indent_str = visitor.block_indent.to_string(context.config);
 669             let outer_indent_str = offset.block_only().to_string(context.config);
 670
 671             result.push('\n');
 672             result.push_str(&inner_indent_str);
 673             result.push_str(trim_newlines(visitor.buffer.to_string().trim()));
 674             result.push('\n');
 675             result.push_str(&outer_indent_str);
 676         }
 677
 678         if result.ends_with('{') {
 679             result.push_str(&sep);
 680         }
 681         result.push('}');
 682
 683         Some(result)
 684     } else {
 685         unreachable!();
 686     }
 687 }
 688
 689 fn is_impl_single_line(
 690     context: &RewriteContext,
 691     items: &[ImplItem],
 692     result: &str,
 693     where_clause_str: &str,
 694     item: &ast::Item,
 695 ) -> Option<bool> {
 696     let snippet = context.snippet(item.span);
 697     let open_pos = snippet.find_uncommented("{")? + 1;
 698
 699     Some(
 700         context.config.impl_empty_single_line() && items.is_empty() && !result.contains('\n')
 701             && result.len() + where_clause_str.len() <= context.config.max_width()
 702             && !contains_comment(&snippet[open_pos..]),
 703     )
 704 }
 705
 706 fn format_impl_ref_and_type(
 707     context: &RewriteContext,
 708     item: &ast::Item,
 709     offset: Indent,
 710 ) -> Option<String> {
 711     if let ast::ItemKind::Impl(
 712         unsafety,
 713         polarity,
 714         defaultness,
 715         ref generics,
 716         ref trait_ref,
 717         ref self_ty,
 718         _,
 719     ) = item.node
 720     {
 721         let mut result = String::with_capacity(128);
 722
 723         result.push_str(&format_visibility(&item.vis));
 724         result.push_str(format_defaultness(defaultness));
 725         result.push_str(format_unsafety(unsafety));
 726         result.push_str("impl");
 727
 728         let lo = context.codemap.span_after(item.span, "impl");
 729         let hi = match *trait_ref {
 730             Some(ref tr) => tr.path.span.lo(),
 731             None => self_ty.span.lo(),
 732         };
 733         let shape = generics_shape_from_config(
 734             context.config,
 735             Shape::indented(offset + last_line_width(&result), context.config),
 736             0,
 737         )?;
 738         let one_line_budget = shape.width.checked_sub(last_line_width(&result) + 2)?;
 739         let generics_str =
 740             rewrite_generics_inner(context, generics, shape, one_line_budget, mk_sp(lo, hi))?;
 741
 742         let polarity_str = if polarity == ast::ImplPolarity::Negative {
 743             "!"
 744         } else {
 745             ""
 746         };
 747
 748         if let Some(ref trait_ref) = *trait_ref {
 749             let result_len = result.len();
 750             if let Some(trait_ref_str) = rewrite_trait_ref(
 751                 context,
 752                 trait_ref,
 753                 offset,
 754                 &generics_str,
 755                 true,
 756                 polarity_str,
 757                 result_len,
 758             ) {
 759                 result.push_str(&trait_ref_str);
 760             } else {
 761                 let generics_str =
 762                     rewrite_generics_inner(context, generics, shape, 0, mk_sp(lo, hi))?;
 763                 result.push_str(&rewrite_trait_ref(
 764                     context,
 765                     trait_ref,
 766                     offset,
 767                     &generics_str,
 768                     false,
 769                     polarity_str,
 770                     result_len,
 771                 )?);
 772             }
 773         } else {
 774             result.push_str(&generics_str);
 775         }
 776
 777         // Try to put the self type in a single line.
 778         // ` for`
 779         let trait_ref_overhead = if trait_ref.is_some() { 4 } else { 0 };
 780         let curly_brace_overhead = if generics.where_clause.predicates.is_empty() {
 781             // If there is no where clause adapt budget for type formatting to take space and curly
 782             // brace into account.
 783             match context.config.item_brace_style() {
 784                 BraceStyle::AlwaysNextLine => 0,
 785                 _ => 2,
 786             }
 787         } else {
 788             0
 789         };
 790         let used_space = last_line_width(&result) + trait_ref_overhead + curly_brace_overhead;
 791         // 1 = space before the type.
 792         let budget = context.budget(used_space + 1);
 793         if let Some(self_ty_str) = self_ty.rewrite(context, Shape::legacy(budget, offset)) {
 794             if !self_ty_str.contains('\n') {
 795                 if trait_ref.is_some() {
 796                     result.push_str(" for ");
 797                 } else {
 798                     result.push(' ');
 799                 }
 800                 result.push_str(&self_ty_str);
 801                 return Some(result);
 802             }
 803         }
 804
 805         // Couldn't fit the self type on a single line, put it on a new line.
 806         result.push('\n');
 807         // Add indentation of one additional tab.
 808         let new_line_offset = offset.block_indent(context.config);
 809         result.push_str(&new_line_offset.to_string(context.config));
 810         if trait_ref.is_some() {
 811             result.push_str("for ");
 812         }
 813         let budget = context.budget(last_line_width(&result));
 814         let type_offset = match context.config.where_style() {
 815             Style::Legacy => new_line_offset + trait_ref_overhead,
 816             Style::Rfc => new_line_offset,
 817         };
 818         result.push_str(&*self_ty
 819             .rewrite(context, Shape::legacy(budget, type_offset))?);
 820         Some(result)
 821     } else {
 822         unreachable!();
 823     }
 824 }
 825
 826 fn rewrite_trait_ref(
 827     context: &RewriteContext,
 828     trait_ref: &ast::TraitRef,
 829     offset: Indent,
 830     generics_str: &str,
 831     retry: bool,
 832     polarity_str: &str,
 833     result_len: usize,
 834 ) -> Option<String> {
 835     // 1 = space between generics and trait_ref
 836     let used_space = 1 + polarity_str.len() + last_line_used_width(generics_str, result_len);
 837     let shape = Shape::indented(offset + used_space, context.config);
 838     if let Some(trait_ref_str) = trait_ref.rewrite(context, shape) {
 839         if !(retry && trait_ref_str.contains('\n')) {
 840             return Some(format!(
 841                 "{} {}{}",
 842                 generics_str,
 843                 polarity_str,
 844                 &trait_ref_str
 845             ));
 846         }
 847     }
 848     // We could not make enough space for trait_ref, so put it on new line.
 849     if !retry {
 850         let offset = offset.block_indent(context.config);
 851         let shape = Shape::indented(offset, context.config);
 852         let trait_ref_str = trait_ref.rewrite(context, shape)?;
 853         Some(format!(
 854             "{}\n{}{}{}",
 855             generics_str,
 856             &offset.to_string(context.config),
 857             polarity_str,
 858             &trait_ref_str
 859         ))
 860     } else {
 861         None
 862     }
 863 }
 864
 865 pub struct StructParts<'a> {
 866     prefix: &'a str,
 867     ident: ast::Ident,
 868     vis: &'a ast::Visibility,
 869     def: &'a ast::VariantData,
 870     generics: Option<&'a ast::Generics>,
 871     span: Span,
 872 }
 873
 874 impl<'a> StructParts<'a> {
 875     fn format_header(&self) -> String {
 876         format_header(self.prefix, self.ident, self.vis)
 877     }
 878
 879     fn from_variant(variant: &'a ast::Variant) -> Self {
 880         StructParts {
 881             prefix: "",
 882             ident: variant.node.name,
 883             vis: &ast::Visibility::Inherited,
 884             def: &variant.node.data,
 885             generics: None,
 886             span: variant.span,
 887         }
 888     }
 889
 890     pub fn from_item(item: &'a ast::Item) -> Self {
 891         let (prefix, def, generics) = match item.node {
 892             ast::ItemKind::Struct(ref def, ref generics) => ("struct ", def, generics),
 893             ast::ItemKind::Union(ref def, ref generics) => ("union ", def, generics),
 894             _ => unreachable!(),
 895         };
 896         StructParts {
 897             prefix: prefix,
 898             ident: item.ident,
 899             vis: &item.vis,
 900             def: def,
 901             generics: Some(generics),
 902             span: item.span,
 903         }
 904     }
 905 }
 906
 907 fn format_struct(
 908     context: &RewriteContext,
 909     struct_parts: &StructParts,
 910     offset: Indent,
 911     one_line_width: Option<usize>,
 912 ) -> Option<String> {
 913     match *struct_parts.def {
 914         ast::VariantData::Unit(..) => Some(format_unit_struct(struct_parts)),
 915         ast::VariantData::Tuple(ref fields, _) => {
 916             format_tuple_struct(context, struct_parts, fields, offset)
 917         }
 918         ast::VariantData::Struct(ref fields, _) => {
 919             format_struct_struct(context, struct_parts, fields, offset, one_line_width)
 920         }
 921     }
 922 }
 923
 924 pub fn format_trait(context: &RewriteContext, item: &ast::Item, offset: Indent) -> Option<String> {
 925     if let ast::ItemKind::Trait(_, unsafety, ref generics, ref type_param_bounds, ref trait_items) =
 926         item.node
 927     {
 928         let mut result = String::with_capacity(128);
 929         let header = format!(
 930             "{}{}trait {}",
 931             format_visibility(&item.vis),
 932             format_unsafety(unsafety),
 933             item.ident
 934         );
 935
 936         result.push_str(&header);
 937
 938         let body_lo = context.codemap.span_after(item.span, "{");
 939
 940         let shape = Shape::indented(offset, context.config);
 941         let generics_str =
 942             rewrite_generics(context, generics, shape, mk_sp(item.span.lo(), body_lo))?;
 943         result.push_str(&generics_str);
 944
 945         // FIXME(#2055): rustfmt fails to format when there are comments between trait bounds.
 946         if !type_param_bounds.is_empty() {
 947             let ident_hi = context.codemap.span_after(item.span, &format!("{}", item.ident));
 948             let bound_hi = type_param_bounds.last().unwrap().span().hi();
 949             let snippet = context.snippet(mk_sp(ident_hi, bound_hi));
 950             if contains_comment(&snippet) {
 951                 return None;
 952             }
 953         }
 954         let trait_bound_str = rewrite_trait_bounds(
 955             context,
 956             type_param_bounds,
 957             Shape::indented(offset, context.config),
 958         )?;
 959         // If the trait, generics, and trait bound cannot fit on the same line,
 960         // put the trait bounds on an indented new line
 961         if offset.width() + last_line_width(&result) + trait_bound_str.len()
 962             > context.config.comment_width()
 963         {
 964             result.push('\n');
 965             let trait_indent = offset.block_only().block_indent(context.config);
 966             result.push_str(&trait_indent.to_string(context.config));
 967         }
 968         result.push_str(&trait_bound_str);
 969
 970         let has_body = !trait_items.is_empty();
 971
 972         let where_density = if (context.config.where_density() == Density::Compressed
 973             && (!result.contains('\n') || context.config.fn_args_indent() == IndentStyle::Block))
 974             || (context.config.fn_args_indent() == IndentStyle::Block && result.is_empty())
 975             || (context.config.where_density() == Density::CompressedIfEmpty && !has_body
 976                 && !result.contains('\n'))
 977         {
 978             Density::Compressed
 979         } else {
 980             Density::Tall
 981         };
 982
 983         let where_budget = context.budget(last_line_width(&result));
 984         let pos_before_where = if type_param_bounds.is_empty() {
 985             generics.where_clause.span.lo()
 986         } else {
 987             type_param_bounds[type_param_bounds.len() - 1].span().hi()
 988         };
 989         let option = WhereClauseOption::snuggled(&generics_str);
 990         let where_clause_str = rewrite_where_clause(
 991             context,
 992             &generics.where_clause,
 993             context.config.item_brace_style(),
 994             Shape::legacy(where_budget, offset.block_only()),
 995             where_density,
 996             "{",
 997             None,
 998             pos_before_where,
 999             option,
1000             false,
1001         )?;
1002         // If the where clause cannot fit on the same line,
1003         // put the where clause on a new line
1004         if !where_clause_str.contains('\n')
1005             && last_line_width(&result) + where_clause_str.len() + offset.width()
1006                 > context.config.comment_width()
1007         {
1008             result.push('\n');
1009             let width = offset.block_indent + context.config.tab_spaces() - 1;
1010             let where_indent = Indent::new(0, width);
1011             result.push_str(&where_indent.to_string(context.config));
1012         }
1013         result.push_str(&where_clause_str);
1014
1015         if generics.where_clause.predicates.is_empty() {
1016             let item_snippet = context.snippet(item.span);
1017             if let Some(lo) = item_snippet.chars().position(|c| c == '/') {
1018                 // 1 = `{`
1019                 let comment_hi = body_lo - BytePos(1);
1020                 let comment_lo = item.span.lo() + BytePos(lo as u32);
1021                 if comment_lo < comment_hi {
1022                     match recover_missing_comment_in_span(
1023                         mk_sp(comment_lo, comment_hi),
1024                         Shape::indented(offset, context.config),
1025                         context,
1026                         last_line_width(&result),
1027                     ) {
1028                         Some(ref missing_comment) if !missing_comment.is_empty() => {
1029                             result.push_str(missing_comment);
1030                         }
1031                         _ => (),
1032                     }
1033                 }
1034             }
1035         }
1036
1037         match context.config.item_brace_style() {
1038             _ if last_line_contains_single_line_comment(&result) => {
1039                 result.push('\n');
1040                 result.push_str(&offset.to_string(context.config));
1041             }
1042             BraceStyle::AlwaysNextLine => {
1043                 result.push('\n');
1044                 result.push_str(&offset.to_string(context.config));
1045             }
1046             BraceStyle::PreferSameLine => result.push(' '),
1047             BraceStyle::SameLineWhere => if !where_clause_str.is_empty()
1048                 && (!trait_items.is_empty() || result.contains('\n'))
1049             {
1050                 result.push('\n');
1051                 result.push_str(&offset.to_string(context.config));
1052             } else {
1053                 result.push(' ');
1054             },
1055         }
1056         result.push('{');
1057
1058         let snippet = context.snippet(item.span);
1059         let open_pos = snippet.find_uncommented("{")? + 1;
1060
1061         if !trait_items.is_empty() || contains_comment(&snippet[open_pos..]) {
1062             let mut visitor = FmtVisitor::from_codemap(context.parse_session, context.config);
1063             visitor.block_indent = offset.block_only().block_indent(context.config);
1064             visitor.last_pos = item.span.lo() + BytePos(open_pos as u32);
1065
1066             for item in trait_items {
1067                 visitor.visit_trait_item(item);
1068             }
1069
1070             visitor.format_missing(item.span.hi() - BytePos(1));
1071
1072             let inner_indent_str = visitor.block_indent.to_string(context.config);
1073             let outer_indent_str = offset.block_only().to_string(context.config);
1074
1075             result.push('\n');
1076             result.push_str(&inner_indent_str);
1077             result.push_str(trim_newlines(visitor.buffer.to_string().trim()));
1078             result.push('\n');
1079             result.push_str(&outer_indent_str);
1080         } else if result.contains('\n') {
1081             result.push('\n');
1082         }
1083
1084         result.push('}');
1085         Some(result)
1086     } else {
1087         unreachable!();
1088     }
1089 }
1090
1091 fn format_unit_struct(p: &StructParts) -> String {
1092     format!("{};", format_header(p.prefix, p.ident, p.vis))
1093 }
1094
1095 pub fn format_struct_struct(
1096     context: &RewriteContext,
1097     struct_parts: &StructParts,
1098     fields: &[ast::StructField],
1099     offset: Indent,
1100     one_line_width: Option<usize>,
1101 ) -> Option<String> {
1102     let mut result = String::with_capacity(1024);
1103     let span = struct_parts.span;
1104
1105     let header_str = struct_parts.format_header();
1106     result.push_str(&header_str);
1107
1108     let header_hi = span.lo() + BytePos(header_str.len() as u32);
1109     let body_lo = context.codemap.span_after(span, "{");
1110
1111     let generics_str = match struct_parts.generics {
1112         Some(g) => format_generics(
1113             context,
1114             g,
1115             context.config.item_brace_style(),
1116             fields.is_empty(),
1117             offset,
1118             mk_sp(header_hi, body_lo),
1119             last_line_width(&result),
1120         )?,
1121         None => {
1122             // 3 = ` {}`, 2 = ` {`.
1123             let overhead = if fields.is_empty() { 3 } else { 2 };
1124             if (context.config.item_brace_style() == BraceStyle::AlwaysNextLine
1125                 && !fields.is_empty())
1126                 || context.config.max_width() < overhead + result.len()
1127             {
1128                 format!("\n{}{{", offset.block_only().to_string(context.config))
1129             } else {
1130                 " {".to_owned()
1131             }
1132         }
1133     };
1134     // 1 = `}`
1135     let overhead = if fields.is_empty() { 1 } else { 0 };
1136     let total_width = result.len() + generics_str.len() + overhead;
1137     if !generics_str.is_empty() && !generics_str.contains('\n')
1138         && total_width > context.config.max_width()
1139     {
1140         result.push('\n');
1141         result.push_str(&offset.to_string(context.config));
1142         result.push_str(generics_str.trim_left());
1143     } else {
1144         result.push_str(&generics_str);
1145     }
1146
1147     if fields.is_empty() {
1148         let snippet = context.snippet(mk_sp(body_lo, span.hi() - BytePos(1)));
1149         if snippet.trim().is_empty() {
1150             // `struct S {}`
1151         } else if snippet.trim_right_matches(&[' ', '\t'][..]).ends_with('\n') {
1152             // fix indent
1153             result.push_str(snippet.trim_right());
1154             result.push('\n');
1155             result.push_str(&offset.to_string(context.config));
1156         } else {
1157             result.push_str(&snippet);
1158         }
1159         result.push('}');
1160         return Some(result);
1161     }
1162
1163     // 3 = ` ` and ` }`
1164     let one_line_budget = context.budget(result.len() + 3 + offset.width());
1165     let one_line_budget =
1166         one_line_width.map_or(0, |one_line_width| min(one_line_width, one_line_budget));
1167
1168     let items_str = rewrite_with_alignment(
1169         fields,
1170         context,
1171         Shape::indented(offset, context.config),
1172         mk_sp(body_lo, span.hi()),
1173         one_line_budget,
1174     )?;
1175
1176     if !items_str.contains('\n') && !result.contains('\n') && items_str.len() <= one_line_budget {
1177         Some(format!("{} {} }}", result, items_str))
1178     } else {
1179         Some(format!(
1180             "{}\n{}{}\n{}}}",
1181             result,
1182             offset
1183                 .block_indent(context.config)
1184                 .to_string(context.config),
1185             items_str,
1186             offset.to_string(context.config)
1187         ))
1188     }
1189 }
1190
1191 /// Returns a bytepos that is after that of `(` in `pub(..)`. If the given visibility does not
1192 /// contain `pub(..)`, then return the `lo` of the `defualt_span`. Yeah, but for what? Well, we need
1193 /// to bypass the `(` in the visibility when creating a span of tuple's body or fn's args.
1194 fn get_bytepos_after_visibility(
1195     context: &RewriteContext,
1196     vis: &ast::Visibility,
1197     default_span: Span,
1198     terminator: &str,
1199 ) -> BytePos {
1200     match *vis {
1201         ast::Visibility::Crate(s, CrateSugar::PubCrate) => context
1202             .codemap
1203             .span_after(mk_sp(s.hi(), default_span.hi()), terminator),
1204         ast::Visibility::Crate(s, CrateSugar::JustCrate) => s.hi(),
1205         ast::Visibility::Restricted { ref path, .. } => path.span.hi(),
1206         _ => default_span.lo(),
1207     }
1208 }
1209
1210 fn format_tuple_struct(
1211     context: &RewriteContext,
1212     struct_parts: &StructParts,
1213     fields: &[ast::StructField],
1214     offset: Indent,
1215 ) -> Option<String> {
1216     let mut result = String::with_capacity(1024);
1217     let span = struct_parts.span;
1218
1219     let header_str = struct_parts.format_header();
1220     result.push_str(&header_str);
1221
1222     let body_lo = if fields.is_empty() {
1223         let lo = get_bytepos_after_visibility(context, struct_parts.vis, span, ")");
1224         context.codemap.span_after(mk_sp(lo, span.hi()), "(")
1225     } else {
1226         fields[0].span.lo()
1227     };
1228     let body_hi = if fields.is_empty() {
1229         context.codemap.span_after(mk_sp(body_lo, span.hi()), ")")
1230     } else {
1231         // This is a dirty hack to work around a missing `)` from the span of the last field.
1232         let last_arg_span = fields[fields.len() - 1].span;
1233         if context.snippet(last_arg_span).ends_with(')') {
1234             last_arg_span.hi()
1235         } else {
1236             context
1237                 .codemap
1238                 .span_after(mk_sp(last_arg_span.hi(), span.hi()), ")")
1239         }
1240     };
1241
1242     let where_clause_str = match struct_parts.generics {
1243         Some(generics) => {
1244             let budget = context.budget(last_line_width(&header_str));
1245             let shape = Shape::legacy(budget, offset);
1246             let g_span = mk_sp(span.lo(), body_lo);
1247             let generics_str = rewrite_generics(context, generics, shape, g_span)?;
1248             result.push_str(&generics_str);
1249
1250             let where_budget = context.budget(last_line_width(&result));
1251             let option = WhereClauseOption::new(true, false);
1252             rewrite_where_clause(
1253                 context,
1254                 &generics.where_clause,
1255                 context.config.item_brace_style(),
1256                 Shape::legacy(where_budget, offset.block_only()),
1257                 Density::Compressed,
1258                 ";",
1259                 None,
1260                 body_hi,
1261                 option,
1262                 false,
1263             )?
1264         }
1265         None => "".to_owned(),
1266     };
1267
1268     if fields.is_empty() {
1269         // 3 = `();`
1270         let used_width = last_line_used_width(&result, offset.width()) + 3;
1271         if used_width > context.config.max_width() {
1272             result.push('\n');
1273             result.push_str(&offset
1274                 .block_indent(context.config)
1275                 .to_string(context.config))
1276         }
1277         result.push('(');
1278         let snippet = context.snippet(mk_sp(
1279             body_lo,
1280             context.codemap.span_before(mk_sp(body_lo, span.hi()), ")"),
1281         ));
1282         if snippet.is_empty() {
1283             // `struct S ()`
1284         } else if snippet.trim_right_matches(&[' ', '\t'][..]).ends_with('\n') {
1285             result.push_str(snippet.trim_right());
1286             result.push('\n');
1287             result.push_str(&offset.to_string(context.config));
1288         } else {
1289             result.push_str(&snippet);
1290         }
1291         result.push(')');
1292     } else {
1293         let shape = Shape::indented(offset, context.config);
1294         let fields = &fields.iter().map(|field| field).collect::<Vec<_>>()[..];
1295         let one_line_width = context.config.fn_call_width();
1296         result = rewrite_call_inner(context, &result, fields, span, shape, one_line_width, false)?;
1297     }
1298
1299     if !where_clause_str.is_empty() && !where_clause_str.contains('\n')
1300         && (result.contains('\n')
1301             || offset.block_indent + result.len() + where_clause_str.len() + 1
1302                 > context.config.max_width())
1303     {
1304         // We need to put the where clause on a new line, but we didn't
1305         // know that earlier, so the where clause will not be indented properly.
1306         result.push('\n');
1307         result.push_str(&(offset.block_only() + (context.config.tab_spaces() - 1))
1308             .to_string(context.config));
1309     }
1310     result.push_str(&where_clause_str);
1311
1312     Some(result)
1313 }
1314
1315 pub fn rewrite_type_alias(
1316     context: &RewriteContext,
1317     indent: Indent,
1318     ident: ast::Ident,
1319     ty: &ast::Ty,
1320     generics: &ast::Generics,
1321     vis: &ast::Visibility,
1322     span: Span,
1323 ) -> Option<String> {
1324     let mut result = String::with_capacity(128);
1325
1326     result.push_str(&format_visibility(vis));
1327     result.push_str("type ");
1328     result.push_str(&ident.to_string());
1329
1330     // 2 = `= `
1331     let shape = Shape::indented(indent + result.len(), context.config).sub_width(2)?;
1332     let g_span = mk_sp(context.codemap.span_after(span, "type"), ty.span.lo());
1333     let generics_str = rewrite_generics(context, generics, shape, g_span)?;
1334     result.push_str(&generics_str);
1335
1336     let where_budget = context.budget(last_line_width(&result));
1337     let option = WhereClauseOption::snuggled(&result);
1338     let where_clause_str = rewrite_where_clause(
1339         context,
1340         &generics.where_clause,
1341         context.config.item_brace_style(),
1342         Shape::legacy(where_budget, indent),
1343         context.config.where_density(),
1344         "=",
1345         Some(span.hi()),
1346         generics.span.hi(),
1347         option,
1348         false,
1349     )?;
1350     result.push_str(&where_clause_str);
1351     if where_clause_str.is_empty() {
1352         result.push_str(" = ");
1353     } else {
1354         result.push_str(&format!("\n{}= ", indent.to_string(context.config)));
1355     }
1356
1357     let line_width = last_line_width(&result);
1358     // This checked_sub may fail as the extra space after '=' is not taken into account
1359     // In that case the budget is set to 0 which will make ty.rewrite retry on a new line
1360     let budget = context.budget(indent.width() + line_width + ";".len());
1361     let type_indent = indent + line_width;
1362     // Try to fit the type on the same line
1363     let ty_str = ty.rewrite(context, Shape::legacy(budget, type_indent))
1364         .or_else(|| {
1365             // The line was too short, try to put the type on the next line
1366
1367             // Remove the space after '='
1368             result.pop();
1369             let type_indent = indent.block_indent(context.config);
1370             result.push('\n');
1371             result.push_str(&type_indent.to_string(context.config));
1372             let budget = context.budget(type_indent.width() + ";".len());
1373             ty.rewrite(context, Shape::legacy(budget, type_indent))
1374         })?;
1375     result.push_str(&ty_str);
1376     result.push_str(";");
1377     Some(result)
1378 }
1379
1380 fn type_annotation_spacing(config: &Config) -> (&str, &str) {
1381     (
1382         if config.space_before_type_annotation() {
1383             " "
1384         } else {
1385             ""
1386         },
1387         if config.space_after_type_annotation_colon() {
1388             " "
1389         } else {
1390             ""
1391         },
1392     )
1393 }
1394
1395 pub fn rewrite_struct_field_prefix(
1396     context: &RewriteContext,
1397     field: &ast::StructField,
1398 ) -> Option<String> {
1399     let vis = format_visibility(&field.vis);
1400     let type_annotation_spacing = type_annotation_spacing(context.config);
1401     Some(match field.ident {
1402         Some(name) => format!("{}{}{}:", vis, name, type_annotation_spacing.0),
1403         None => format!("{}", vis),
1404     })
1405 }
1406
1407 impl Rewrite for ast::StructField {
1408     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
1409         rewrite_struct_field(context, self, shape, 0)
1410     }
1411 }
1412
1413 pub fn rewrite_struct_field(
1414     context: &RewriteContext,
1415     field: &ast::StructField,
1416     shape: Shape,
1417     lhs_max_width: usize,
1418 ) -> Option<String> {
1419     if contains_skip(&field.attrs) {
1420         return Some(context.snippet(mk_sp(field.attrs[0].span.lo(), field.span.hi())));
1421     }
1422
1423     let type_annotation_spacing = type_annotation_spacing(context.config);
1424     let prefix = rewrite_struct_field_prefix(context, field)?;
1425
1426     let attrs_str = field.attrs.rewrite(context, shape)?;
1427     let attrs_extendable = attrs_str.is_empty()
1428         || (context.config.attributes_on_same_line_as_field()
1429             && is_attributes_extendable(&attrs_str));
1430     let missing_span = if field.attrs.is_empty() {
1431         mk_sp(field.span.lo(), field.span.lo())
1432     } else {
1433         mk_sp(field.attrs.last().unwrap().span.hi(), field.span.lo())
1434     };
1435     let mut spacing = String::from(if field.ident.is_some() {
1436         type_annotation_spacing.1
1437     } else {
1438         ""
1439     });
1440     // Try to put everything on a single line.
1441     let attr_prefix = combine_strs_with_missing_comments(
1442         context,
1443         &attrs_str,
1444         &prefix,
1445         missing_span,
1446         shape,
1447         attrs_extendable,
1448     )?;
1449     let overhead = last_line_width(&attr_prefix);
1450     let lhs_offset = lhs_max_width.checked_sub(overhead).unwrap_or(0);
1451     for _ in 0..lhs_offset {
1452         spacing.push(' ');
1453     }
1454     // In this extreme case we will be missing a space betweeen an attribute and a field.
1455     if prefix.is_empty() && !attrs_str.is_empty() && attrs_extendable && spacing.is_empty() {
1456         spacing.push(' ');
1457     }
1458     let ty_shape = shape.offset_left(overhead + spacing.len())?;
1459     if let Some(ref ty) = field.ty.rewrite(context, ty_shape) {
1460         if !ty.contains('\n') {
1461             return Some(attr_prefix + &spacing + ty);
1462         }
1463     }
1464
1465     // We must use multiline.
1466     let new_shape = shape.with_max_width(context.config);
1467     let ty_rewritten = field.ty.rewrite(context, new_shape)?;
1468
1469     let field_str = if prefix.is_empty() {
1470         ty_rewritten
1471     } else if prefix.len() + first_line_width(&ty_rewritten) + 1 <= shape.width {
1472         prefix + " " + &ty_rewritten
1473     } else {
1474         let type_offset = shape.indent.block_indent(context.config);
1475         let nested_shape = Shape::indented(type_offset, context.config);
1476         let nested_ty = field.ty.rewrite(context, nested_shape)?;
1477         prefix + "\n" + &type_offset.to_string(context.config) + &nested_ty
1478     };
1479     combine_strs_with_missing_comments(
1480         context,
1481         &attrs_str,
1482         &field_str,
1483         missing_span,
1484         shape,
1485         attrs_extendable,
1486     )
1487 }
1488
1489 pub struct StaticParts<'a> {
1490     prefix: &'a str,
1491     vis: &'a ast::Visibility,
1492     ident: ast::Ident,
1493     ty: &'a ast::Ty,
1494     mutability: ast::Mutability,
1495     expr_opt: Option<&'a ptr::P<ast::Expr>>,
1496     span: Span,
1497 }
1498
1499 impl<'a> StaticParts<'a> {
1500     pub fn from_item(item: &'a ast::Item) -> Self {
1501         let (prefix, ty, mutability, expr) = match item.node {
1502             ast::ItemKind::Static(ref ty, mutability, ref expr) => ("static", ty, mutability, expr),
1503             ast::ItemKind::Const(ref ty, ref expr) => {
1504                 ("const", ty, ast::Mutability::Immutable, expr)
1505             }
1506             _ => unreachable!(),
1507         };
1508         StaticParts {
1509             prefix: prefix,
1510             vis: &item.vis,
1511             ident: item.ident,
1512             ty: ty,
1513             mutability: mutability,
1514             expr_opt: Some(expr),
1515             span: item.span,
1516         }
1517     }
1518
1519     pub fn from_trait_item(ti: &'a ast::TraitItem) -> Self {
1520         let (ty, expr_opt) = match ti.node {
1521             ast::TraitItemKind::Const(ref ty, ref expr_opt) => (ty, expr_opt),
1522             _ => unreachable!(),
1523         };
1524         StaticParts {
1525             prefix: "const",
1526             vis: &ast::Visibility::Inherited,
1527             ident: ti.ident,
1528             ty: ty,
1529             mutability: ast::Mutability::Immutable,
1530             expr_opt: expr_opt.as_ref(),
1531             span: ti.span,
1532         }
1533     }
1534
1535     pub fn from_impl_item(ii: &'a ast::ImplItem) -> Self {
1536         let (ty, expr) = match ii.node {
1537             ast::ImplItemKind::Const(ref ty, ref expr) => (ty, expr),
1538             _ => unreachable!(),
1539         };
1540         StaticParts {
1541             prefix: "const",
1542             vis: &ii.vis,
1543             ident: ii.ident,
1544             ty: ty,
1545             mutability: ast::Mutability::Immutable,
1546             expr_opt: Some(expr),
1547             span: ii.span,
1548         }
1549     }
1550 }
1551
1552 fn rewrite_static(
1553     context: &RewriteContext,
1554     static_parts: &StaticParts,
1555     offset: Indent,
1556 ) -> Option<String> {
1557     let colon = colon_spaces(
1558         context.config.space_before_type_annotation(),
1559         context.config.space_after_type_annotation_colon(),
1560     );
1561     let prefix = format!(
1562         "{}{} {}{}{}",
1563         format_visibility(static_parts.vis),
1564         static_parts.prefix,
1565         format_mutability(static_parts.mutability),
1566         static_parts.ident,
1567         colon,
1568     );
1569     // 2 = " =".len()
1570     let ty_shape =
1571         Shape::indented(offset.block_only(), context.config).offset_left(prefix.len() + 2)?;
1572     let ty_str = static_parts.ty.rewrite(context, ty_shape)?;
1573
1574     if let Some(expr) = static_parts.expr_opt {
1575         let lhs = format!("{}{} =", prefix, ty_str);
1576         // 1 = ;
1577         let remaining_width = context.budget(offset.block_indent + 1);
1578         rewrite_assign_rhs(
1579             context,
1580             lhs,
1581             expr,
1582             Shape::legacy(remaining_width, offset.block_only()),
1583         ).and_then(|res| {
1584             recover_comment_removed(res, static_parts.span, context)
1585         })
1586             .map(|s| if s.ends_with(';') { s } else { s + ";" })
1587     } else {
1588         Some(format!("{}{};", prefix, ty_str))
1589     }
1590 }
1591
1592 pub fn rewrite_associated_type(
1593     ident: ast::Ident,
1594     ty_opt: Option<&ptr::P<ast::Ty>>,
1595     ty_param_bounds_opt: Option<&ast::TyParamBounds>,
1596     context: &RewriteContext,
1597     indent: Indent,
1598 ) -> Option<String> {
1599     let prefix = format!("type {}", ident);
1600
1601     let type_bounds_str = if let Some(ty_param_bounds) = ty_param_bounds_opt {
1602         // 2 = ": ".len()
1603         let shape = Shape::indented(indent, context.config).offset_left(prefix.len() + 2)?;
1604         let bounds: &[_] = ty_param_bounds;
1605         let bound_str = bounds
1606             .iter()
1607             .map(|ty_bound| ty_bound.rewrite(context, shape))
1608             .collect::<Option<Vec<_>>>()?;
1609         if !bounds.is_empty() {
1610             format!(": {}", join_bounds(context, shape, &bound_str))
1611         } else {
1612             String::new()
1613         }
1614     } else {
1615         String::new()
1616     };
1617
1618     if let Some(ty) = ty_opt {
1619         let ty_str = ty.rewrite(
1620             context,
1621             Shape::legacy(
1622                 context.budget(indent.block_indent + prefix.len() + 2),
1623                 indent.block_only(),
1624             ),
1625         )?;
1626         Some(format!("{}{} = {};", prefix, type_bounds_str, ty_str))
1627     } else {
1628         Some(format!("{}{};", prefix, type_bounds_str))
1629     }
1630 }
1631
1632 pub fn rewrite_associated_impl_type(
1633     ident: ast::Ident,
1634     defaultness: ast::Defaultness,
1635     ty_opt: Option<&ptr::P<ast::Ty>>,
1636     ty_param_bounds_opt: Option<&ast::TyParamBounds>,
1637     context: &RewriteContext,
1638     indent: Indent,
1639 ) -> Option<String> {
1640     let result = rewrite_associated_type(ident, ty_opt, ty_param_bounds_opt, context, indent)?;
1641
1642     match defaultness {
1643         ast::Defaultness::Default => Some(format!("default {}", result)),
1644         _ => Some(result),
1645     }
1646 }
1647
1648 impl Rewrite for ast::FunctionRetTy {
1649     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
1650         match *self {
1651             ast::FunctionRetTy::Default(_) => Some(String::new()),
1652             ast::FunctionRetTy::Ty(ref ty) => {
1653                 let inner_width = shape.width.checked_sub(3)?;
1654                 ty.rewrite(context, Shape::legacy(inner_width, shape.indent + 3))
1655                     .map(|r| format!("-> {}", r))
1656             }
1657         }
1658     }
1659 }
1660
1661 fn is_empty_infer(context: &RewriteContext, ty: &ast::Ty) -> bool {
1662     match ty.node {
1663         ast::TyKind::Infer => {
1664             let original = context.snippet(ty.span);
1665             original != "_"
1666         }
1667         _ => false,
1668     }
1669 }
1670
1671 impl Rewrite for ast::Arg {
1672     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
1673         if is_named_arg(self) {
1674             let mut result = self.pat
1675                 .rewrite(context, Shape::legacy(shape.width, shape.indent))?;
1676
1677             if !is_empty_infer(context, &*self.ty) {
1678                 if context.config.space_before_type_annotation() {
1679                     result.push_str(" ");
1680                 }
1681                 result.push_str(":");
1682                 if context.config.space_after_type_annotation_colon() {
1683                     result.push_str(" ");
1684                 }
1685                 let overhead = last_line_width(&result);
1686                 let max_width = shape.width.checked_sub(overhead)?;
1687                 let ty_str = self.ty
1688                     .rewrite(context, Shape::legacy(max_width, shape.indent))?;
1689                 result.push_str(&ty_str);
1690             }
1691
1692             Some(result)
1693         } else {
1694             self.ty.rewrite(context, shape)
1695         }
1696     }
1697 }
1698
1699 fn rewrite_explicit_self(
1700     explicit_self: &ast::ExplicitSelf,
1701     args: &[ast::Arg],
1702     context: &RewriteContext,
1703 ) -> Option<String> {
1704     match explicit_self.node {
1705         ast::SelfKind::Region(lt, m) => {
1706             let mut_str = format_mutability(m);
1707             match lt {
1708                 Some(ref l) => {
1709                     let lifetime_str = l.rewrite(
1710                         context,
1711                         Shape::legacy(context.config.max_width(), Indent::empty()),
1712                     )?;
1713                     Some(format!("&{} {}self", lifetime_str, mut_str))
1714                 }
1715                 None => Some(format!("&{}self", mut_str)),
1716             }
1717         }
1718         ast::SelfKind::Explicit(ref ty, _) => {
1719             assert!(!args.is_empty(), "&[ast::Arg] shouldn't be empty.");
1720
1721             let mutability = explicit_self_mutability(&args[0]);
1722             let type_str = ty.rewrite(
1723                 context,
1724                 Shape::legacy(context.config.max_width(), Indent::empty()),
1725             )?;
1726
1727             Some(format!(
1728                 "{}self: {}",
1729                 format_mutability(mutability),
1730                 type_str
1731             ))
1732         }
1733         ast::SelfKind::Value(_) => {
1734             assert!(!args.is_empty(), "&[ast::Arg] shouldn't be empty.");
1735
1736             let mutability = explicit_self_mutability(&args[0]);
1737
1738             Some(format!("{}self", format_mutability(mutability)))
1739         }
1740     }
1741 }
1742
1743 // Hacky solution caused by absence of `Mutability` in `SelfValue` and
1744 // `SelfExplicit` variants of `ast::ExplicitSelf_`.
1745 fn explicit_self_mutability(arg: &ast::Arg) -> ast::Mutability {
1746     if let ast::PatKind::Ident(ast::BindingMode::ByValue(mutability), _, _) = arg.pat.node {
1747         mutability
1748     } else {
1749         unreachable!()
1750     }
1751 }
1752
1753 pub fn span_lo_for_arg(arg: &ast::Arg) -> BytePos {
1754     if is_named_arg(arg) {
1755         arg.pat.span.lo()
1756     } else {
1757         arg.ty.span.lo()
1758     }
1759 }
1760
1761 pub fn span_hi_for_arg(context: &RewriteContext, arg: &ast::Arg) -> BytePos {
1762     match arg.ty.node {
1763         ast::TyKind::Infer if context.snippet(arg.ty.span) == "_" => arg.ty.span.hi(),
1764         ast::TyKind::Infer if is_named_arg(arg) => arg.pat.span.hi(),
1765         _ => arg.ty.span.hi(),
1766     }
1767 }
1768
1769 pub fn is_named_arg(arg: &ast::Arg) -> bool {
1770     if let ast::PatKind::Ident(_, ident, _) = arg.pat.node {
1771         ident.node != symbol::keywords::Invalid.ident()
1772     } else {
1773         true
1774     }
1775 }
1776
1777 // Return type is (result, force_new_line_for_brace)
1778 fn rewrite_fn_base(
1779     context: &RewriteContext,
1780     indent: Indent,
1781     ident: ast::Ident,
1782     fn_sig: &FnSig,
1783     span: Span,
1784     newline_brace: bool,
1785     has_body: bool,
1786 ) -> Option<(String, bool)> {
1787     let mut force_new_line_for_brace = false;
1788
1789     let where_clause = &fn_sig.generics.where_clause;
1790
1791     let mut result = String::with_capacity(1024);
1792     result.push_str(&fn_sig.to_str(context));
1793
1794     // fn foo
1795     result.push_str("fn ");
1796     result.push_str(&ident.to_string());
1797
1798     // Generics.
1799     let overhead = if has_body && !newline_brace {
1800         // 4 = `() {`
1801         4
1802     } else {
1803         // 2 = `()`
1804         2
1805     };
1806     let used_width = last_line_used_width(&result, indent.width());
1807     let one_line_budget = context.budget(used_width + overhead);
1808     let shape = Shape {
1809         width: one_line_budget,
1810         indent: indent,
1811         offset: used_width,
1812     };
1813     let fd = fn_sig.decl;
1814     let g_span = mk_sp(span.lo(), fd.output.span().lo());
1815     let generics_str = rewrite_generics(context, fn_sig.generics, shape, g_span)?;
1816     result.push_str(&generics_str);
1817
1818     let snuggle_angle_bracket = generics_str
1819         .lines()
1820         .last()
1821         .map_or(false, |l| l.trim_left().len() == 1);
1822
1823     // Note that the width and indent don't really matter, we'll re-layout the
1824     // return type later anyway.
1825     let ret_str = fd.output
1826         .rewrite(context, Shape::indented(indent, context.config))?;
1827
1828     let multi_line_ret_str = ret_str.contains('\n');
1829     let ret_str_len = if multi_line_ret_str { 0 } else { ret_str.len() };
1830
1831     // Args.
1832     let (one_line_budget, multi_line_budget, mut arg_indent) = compute_budgets_for_args(
1833         context,
1834         &result,
1835         indent,
1836         ret_str_len,
1837         newline_brace,
1838         has_body,
1839         multi_line_ret_str,
1840     )?;
1841
1842     debug!(
1843         "rewrite_fn_base: one_line_budget: {}, multi_line_budget: {}, arg_indent: {:?}",
1844         one_line_budget,
1845         multi_line_budget,
1846         arg_indent
1847     );
1848
1849     // Check if vertical layout was forced.
1850     if one_line_budget == 0 {
1851         if snuggle_angle_bracket {
1852             result.push('(');
1853         } else if context.config.fn_args_paren_newline() {
1854             result.push('\n');
1855             result.push_str(&arg_indent.to_string(context.config));
1856             if context.config.fn_args_indent() == IndentStyle::Visual {
1857                 arg_indent = arg_indent + 1; // extra space for `(`
1858             }
1859             result.push('(');
1860         } else {
1861             result.push_str("(");
1862             if context.config.fn_args_indent() == IndentStyle::Visual {
1863                 result.push('\n');
1864                 result.push_str(&arg_indent.to_string(context.config));
1865             }
1866         }
1867     } else {
1868         result.push('(');
1869     }
1870     if context.config.spaces_within_parens() && !fd.inputs.is_empty() && result.ends_with('(') {
1871         result.push(' ')
1872     }
1873
1874     // Skip `pub(crate)`.
1875     let lo_after_visibility = get_bytepos_after_visibility(context, &fn_sig.visibility, span, ")");
1876     // A conservative estimation, to goal is to be over all parens in generics
1877     let args_start = fn_sig
1878         .generics
1879         .ty_params
1880         .last()
1881         .map_or(lo_after_visibility, |tp| end_typaram(tp));
1882     let args_end = if fd.inputs.is_empty() {
1883         context
1884             .codemap
1885             .span_after(mk_sp(args_start, span.hi()), ")")
1886     } else {
1887         let last_span = mk_sp(fd.inputs[fd.inputs.len() - 1].span().hi(), span.hi());
1888         context.codemap.span_after(last_span, ")")
1889     };
1890     let args_span = mk_sp(
1891         context
1892             .codemap
1893             .span_after(mk_sp(args_start, span.hi()), "("),
1894         args_end,
1895     );
1896     let arg_str = rewrite_args(
1897         context,
1898         &fd.inputs,
1899         fd.get_self().as_ref(),
1900         one_line_budget,
1901         multi_line_budget,
1902         indent,
1903         arg_indent,
1904         args_span,
1905         fd.variadic,
1906         generics_str.contains('\n'),
1907     )?;
1908
1909     let put_args_in_block = match context.config.fn_args_indent() {
1910         IndentStyle::Block => arg_str.contains('\n') || arg_str.len() > one_line_budget,
1911         _ => false,
1912     } && !fd.inputs.is_empty();
1913
1914     let mut args_last_line_contains_comment = false;
1915     if put_args_in_block {
1916         arg_indent = indent.block_indent(context.config);
1917         result.push('\n');
1918         result.push_str(&arg_indent.to_string(context.config));
1919         result.push_str(&arg_str);
1920         result.push('\n');
1921         result.push_str(&indent.to_string(context.config));
1922         result.push(')');
1923     } else {
1924         result.push_str(&arg_str);
1925         let used_width = last_line_used_width(&result, indent.width()) + first_line_width(&ret_str);
1926         // Put the closing brace on the next line if it overflows the max width.
1927         // 1 = `)`
1928         if fd.inputs.is_empty() && used_width + 1 > context.config.max_width() {
1929             result.push('\n');
1930         }
1931         if context.config.spaces_within_parens() && !fd.inputs.is_empty() {
1932             result.push(' ')
1933         }
1934         // If the last line of args contains comment, we cannot put the closing paren
1935         // on the same line.
1936         if arg_str
1937             .lines()
1938             .last()
1939             .map_or(false, |last_line| last_line.contains("//"))
1940         {
1941             args_last_line_contains_comment = true;
1942             result.push('\n');
1943             result.push_str(&arg_indent.to_string(context.config));
1944         }
1945         result.push(')');
1946     }
1947
1948     // Return type.
1949     if let ast::FunctionRetTy::Ty(..) = fd.output {
1950         let ret_should_indent = match context.config.fn_args_indent() {
1951             // If our args are block layout then we surely must have space.
1952             IndentStyle::Block if put_args_in_block || fd.inputs.is_empty() => false,
1953             _ if args_last_line_contains_comment => false,
1954             _ if result.contains('\n') || multi_line_ret_str => true,
1955             _ => {
1956                 // If the return type would push over the max width, then put the return type on
1957                 // a new line. With the +1 for the signature length an additional space between
1958                 // the closing parenthesis of the argument and the arrow '->' is considered.
1959                 let mut sig_length = result.len() + indent.width() + ret_str_len + 1;
1960
1961                 // If there is no where clause, take into account the space after the return type
1962                 // and the brace.
1963                 if where_clause.predicates.is_empty() {
1964                     sig_length += 2;
1965                 }
1966
1967                 sig_length > context.config.max_width()
1968             }
1969         };
1970         let ret_indent = if ret_should_indent {
1971             let indent = match context.config.fn_return_indent() {
1972                 ReturnIndent::WithWhereClause => indent + 4,
1973                 // Aligning with non-existent args looks silly.
1974                 _ if arg_str.is_empty() => {
1975                     force_new_line_for_brace = true;
1976                     indent + 4
1977                 }
1978                 // FIXME: we might want to check that using the arg indent
1979                 // doesn't blow our budget, and if it does, then fallback to
1980                 // the where clause indent.
1981                 _ => arg_indent,
1982             };
1983
1984             result.push('\n');
1985             result.push_str(&indent.to_string(context.config));
1986             indent
1987         } else {
1988             result.push(' ');
1989             Indent::new(indent.block_indent, last_line_width(&result))
1990         };
1991
1992         if multi_line_ret_str || ret_should_indent {
1993             // Now that we know the proper indent and width, we need to
1994             // re-layout the return type.
1995             let ret_str = fd.output
1996                 .rewrite(context, Shape::indented(ret_indent, context.config))?;
1997             result.push_str(&ret_str);
1998         } else {
1999             result.push_str(&ret_str);
2000         }
2001
2002         // Comment between return type and the end of the decl.
2003         let snippet_lo = fd.output.span().hi();
2004         if where_clause.predicates.is_empty() {
2005             let snippet_hi = span.hi();
2006             let snippet = context.snippet(mk_sp(snippet_lo, snippet_hi));
2007             // Try to preserve the layout of the original snippet.
2008             let original_starts_with_newline = snippet
2009                 .find(|c| c != ' ')
2010                 .map_or(false, |i| starts_with_newline(&snippet[i..]));
2011             let original_ends_with_newline = snippet
2012                 .rfind(|c| c != ' ')
2013                 .map_or(false, |i| snippet[i..].ends_with('\n'));
2014             let snippet = snippet.trim();
2015             if !snippet.is_empty() {
2016                 result.push(if original_starts_with_newline {
2017                     '\n'
2018                 } else {
2019                     ' '
2020                 });
2021                 result.push_str(snippet);
2022                 if original_ends_with_newline {
2023                     force_new_line_for_brace = true;
2024                 }
2025             }
2026         }
2027     }
2028
2029     let should_compress_where = match context.config.where_density() {
2030         Density::Compressed => !result.contains('\n'),
2031         Density::CompressedIfEmpty => !has_body && !result.contains('\n'),
2032         _ => false,
2033     };
2034
2035     let pos_before_where = match fd.output {
2036         ast::FunctionRetTy::Default(..) => args_span.hi(),
2037         ast::FunctionRetTy::Ty(ref ty) => ty.span.hi(),
2038     };
2039
2040     let is_args_multi_lined = arg_str.contains('\n');
2041
2042     if where_clause.predicates.len() == 1 && should_compress_where {
2043         let budget = context.budget(last_line_used_width(&result, indent.width()));
2044         if let Some(where_clause_str) = rewrite_where_clause(
2045             context,
2046             where_clause,
2047             context.config.fn_brace_style(),
2048             Shape::legacy(budget, indent),
2049             Density::Compressed,
2050             "{",
2051             Some(span.hi()),
2052             pos_before_where,
2053             WhereClauseOption::compressed(),
2054             is_args_multi_lined,
2055         ) {
2056             result.push_str(&where_clause_str);
2057             force_new_line_for_brace |= last_line_contains_single_line_comment(&result);
2058             return Some((result, force_new_line_for_brace));
2059         }
2060     }
2061
2062     let option = WhereClauseOption::new(!has_body, put_args_in_block && ret_str.is_empty());
2063     let where_clause_str = rewrite_where_clause(
2064         context,
2065         where_clause,
2066         context.config.fn_brace_style(),
2067         Shape::indented(indent, context.config),
2068         Density::Tall,
2069         "{",
2070         Some(span.hi()),
2071         pos_before_where,
2072         option,
2073         is_args_multi_lined,
2074     )?;
2075     // If there are neither where clause nor return type, we may be missing comments between
2076     // args and `{`.
2077     if where_clause_str.is_empty() {
2078         if let ast::FunctionRetTy::Default(ret_span) = fd.output {
2079             match recover_missing_comment_in_span(
2080                 mk_sp(args_span.hi(), ret_span.hi()),
2081                 shape,
2082                 context,
2083                 last_line_width(&result),
2084             ) {
2085                 Some(ref missing_comment) if !missing_comment.is_empty() => {
2086                     result.push_str(missing_comment);
2087                     force_new_line_for_brace = true;
2088                 }
2089                 _ => (),
2090             }
2091         }
2092     }
2093
2094     result.push_str(&where_clause_str);
2095
2096     force_new_line_for_brace |= last_line_contains_single_line_comment(&result);
2097     force_new_line_for_brace |= is_args_multi_lined && context.config.where_single_line();
2098     Some((result, force_new_line_for_brace))
2099 }
2100
2101 #[derive(Copy, Clone)]
2102 struct WhereClauseOption {
2103     suppress_comma: bool, // Force no trailing comma
2104     snuggle: bool,        // Do not insert newline before `where`
2105     compress_where: bool, // Try single line where clause instead of vertical layout
2106 }
2107
2108 impl WhereClauseOption {
2109     pub fn new(suppress_comma: bool, snuggle: bool) -> WhereClauseOption {
2110         WhereClauseOption {
2111             suppress_comma: suppress_comma,
2112             snuggle: snuggle,
2113             compress_where: false,
2114         }
2115     }
2116
2117     pub fn compressed() -> WhereClauseOption {
2118         WhereClauseOption {
2119             suppress_comma: true,
2120             snuggle: false,
2121             compress_where: true,
2122         }
2123     }
2124
2125     pub fn snuggled(current: &str) -> WhereClauseOption {
2126         WhereClauseOption {
2127             suppress_comma: false,
2128             snuggle: trimmed_last_line_width(current) == 1,
2129             compress_where: false,
2130         }
2131     }
2132 }
2133
2134 fn rewrite_args(
2135     context: &RewriteContext,
2136     args: &[ast::Arg],
2137     explicit_self: Option<&ast::ExplicitSelf>,
2138     one_line_budget: usize,
2139     multi_line_budget: usize,
2140     indent: Indent,
2141     arg_indent: Indent,
2142     span: Span,
2143     variadic: bool,
2144     generics_str_contains_newline: bool,
2145 ) -> Option<String> {
2146     let mut arg_item_strs = args.iter()
2147         .map(|arg| {
2148             arg.rewrite(context, Shape::legacy(multi_line_budget, arg_indent))
2149         })
2150         .collect::<Option<Vec<_>>>()?;
2151
2152     // Account for sugary self.
2153     // FIXME: the comment for the self argument is dropped. This is blocked
2154     // on rust issue #27522.
2155     let min_args = explicit_self
2156         .and_then(|explicit_self| {
2157             rewrite_explicit_self(explicit_self, args, context)
2158         })
2159         .map_or(1, |self_str| {
2160             arg_item_strs[0] = self_str;
2161             2
2162         });
2163
2164     // Comments between args.
2165     let mut arg_items = Vec::new();
2166     if min_args == 2 {
2167         arg_items.push(ListItem::from_str(""));
2168     }
2169
2170     // FIXME(#21): if there are no args, there might still be a comment, but
2171     // without spans for the comment or parens, there is no chance of
2172     // getting it right. You also don't get to put a comment on self, unless
2173     // it is explicit.
2174     if args.len() >= min_args || variadic {
2175         let comment_span_start = if min_args == 2 {
2176             let second_arg_start = if arg_has_pattern(&args[1]) {
2177                 args[1].pat.span.lo()
2178             } else {
2179                 args[1].ty.span.lo()
2180             };
2181             let reduced_span = mk_sp(span.lo(), second_arg_start);
2182
2183             context.codemap.span_after_last(reduced_span, ",")
2184         } else {
2185             span.lo()
2186         };
2187
2188         enum ArgumentKind<'a> {
2189             Regular(&'a ast::Arg),
2190             Variadic(BytePos),
2191         }
2192
2193         let variadic_arg = if variadic {
2194             let variadic_span = mk_sp(args.last().unwrap().ty.span.hi(), span.hi());
2195             let variadic_start = context.codemap.span_after(variadic_span, "...") - BytePos(3);
2196             Some(ArgumentKind::Variadic(variadic_start))
2197         } else {
2198             None
2199         };
2200
2201         let more_items = itemize_list(
2202             context.codemap,
2203             args[min_args - 1..]
2204                 .iter()
2205                 .map(ArgumentKind::Regular)
2206                 .chain(variadic_arg),
2207             ")",
2208             |arg| match *arg {
2209                 ArgumentKind::Regular(arg) => span_lo_for_arg(arg),
2210                 ArgumentKind::Variadic(start) => start,
2211             },
2212             |arg| match *arg {
2213                 ArgumentKind::Regular(arg) => arg.ty.span.hi(),
2214                 ArgumentKind::Variadic(start) => start + BytePos(3),
2215             },
2216             |arg| match *arg {
2217                 ArgumentKind::Regular(..) => None,
2218                 ArgumentKind::Variadic(..) => Some("...".to_owned()),
2219             },
2220             comment_span_start,
2221             span.hi(),
2222             false,
2223         );
2224
2225         arg_items.extend(more_items);
2226     }
2227
2228     let fits_in_one_line = !generics_str_contains_newline
2229         && (arg_items.is_empty()
2230             || arg_items.len() == 1 && arg_item_strs[0].len() <= one_line_budget);
2231
2232     for (item, arg) in arg_items.iter_mut().zip(arg_item_strs) {
2233         item.item = Some(arg);
2234     }
2235
2236     let last_line_ends_with_comment = arg_items
2237         .iter()
2238         .last()
2239         .and_then(|item| item.post_comment.as_ref())
2240         .map_or(false, |s| s.trim().starts_with("//"));
2241
2242     let (indent, trailing_comma) = match context.config.fn_args_indent() {
2243         IndentStyle::Block if fits_in_one_line => {
2244             (indent.block_indent(context.config), SeparatorTactic::Never)
2245         }
2246         IndentStyle::Block => (
2247             indent.block_indent(context.config),
2248             context.config.trailing_comma(),
2249         ),
2250         IndentStyle::Visual if last_line_ends_with_comment => {
2251             (arg_indent, context.config.trailing_comma())
2252         }
2253         IndentStyle::Visual => (arg_indent, SeparatorTactic::Never),
2254     };
2255
2256     let tactic = definitive_tactic(
2257         &arg_items,
2258         context.config.fn_args_density().to_list_tactic(),
2259         Separator::Comma,
2260         one_line_budget,
2261     );
2262     let budget = match tactic {
2263         DefinitiveListTactic::Horizontal => one_line_budget,
2264         _ => multi_line_budget,
2265     };
2266
2267     debug!("rewrite_args: budget: {}, tactic: {:?}", budget, tactic);
2268
2269     let fmt = ListFormatting {
2270         tactic: tactic,
2271         separator: ",",
2272         trailing_separator: if variadic {
2273             SeparatorTactic::Never
2274         } else {
2275             trailing_comma
2276         },
2277         separator_place: SeparatorPlace::Back,
2278         shape: Shape::legacy(budget, indent),
2279         ends_with_newline: tactic.ends_with_newline(context.config.fn_args_indent()),
2280         preserve_newline: true,
2281         config: context.config,
2282     };
2283
2284     write_list(&arg_items, &fmt)
2285 }
2286
2287 fn arg_has_pattern(arg: &ast::Arg) -> bool {
2288     if let ast::PatKind::Ident(_, ident, _) = arg.pat.node {
2289         ident.node != symbol::keywords::Invalid.ident()
2290     } else {
2291         true
2292     }
2293 }
2294
2295 fn compute_budgets_for_args(
2296     context: &RewriteContext,
2297     result: &str,
2298     indent: Indent,
2299     ret_str_len: usize,
2300     newline_brace: bool,
2301     has_braces: bool,
2302     force_vertical_layout: bool,
2303 ) -> Option<((usize, usize, Indent))> {
2304     debug!(
2305         "compute_budgets_for_args {} {:?}, {}, {}",
2306         result.len(),
2307         indent,
2308         ret_str_len,
2309         newline_brace
2310     );
2311     // Try keeping everything on the same line.
2312     if !result.contains('\n') && !force_vertical_layout {
2313         // 2 = `()`, 3 = `() `, space is before ret_string.
2314         let overhead = if ret_str_len == 0 { 2 } else { 3 };
2315         let mut used_space = indent.width() + result.len() + ret_str_len + overhead;
2316         if has_braces {
2317             if !newline_brace {
2318                 // 2 = `{}`
2319                 used_space += 2;
2320             }
2321         } else {
2322             // 1 = `;`
2323             used_space += 1;
2324         }
2325         let one_line_budget = context.budget(used_space);
2326
2327         if one_line_budget > 0 {
2328             // 4 = "() {".len()
2329             let (indent, multi_line_budget) = match context.config.fn_args_indent() {
2330                 IndentStyle::Block => {
2331                     let indent = indent.block_indent(context.config);
2332                     (indent, context.budget(indent.width() + 1))
2333                 }
2334                 IndentStyle::Visual => {
2335                     let indent = indent + result.len() + 1;
2336                     let multi_line_overhead = indent.width() + if newline_brace { 2 } else { 4 };
2337                     (indent, context.budget(multi_line_overhead))
2338                 }
2339             };
2340
2341             return Some((one_line_budget, multi_line_budget, indent));
2342         }
2343     }
2344
2345     // Didn't work. we must force vertical layout and put args on a newline.
2346     let new_indent = indent.block_indent(context.config);
2347     let used_space = match context.config.fn_args_indent() {
2348         // 1 = `,`
2349         IndentStyle::Block => new_indent.width() + 1,
2350         // Account for `)` and possibly ` {`.
2351         IndentStyle::Visual => new_indent.width() + if ret_str_len == 0 { 1 } else { 3 },
2352     };
2353     Some((0, context.budget(used_space), new_indent))
2354 }
2355
2356 fn newline_for_brace(config: &Config, where_clause: &ast::WhereClause, has_body: bool) -> bool {
2357     let predicate_count = where_clause.predicates.len();
2358
2359     if config.where_single_line() && predicate_count == 1 {
2360         return false;
2361     }
2362     match (config.fn_brace_style(), config.where_density()) {
2363         (BraceStyle::AlwaysNextLine, _) => true,
2364         (_, Density::Compressed) if predicate_count == 1 => false,
2365         (_, Density::CompressedIfEmpty) if predicate_count == 1 && !has_body => false,
2366         (BraceStyle::SameLineWhere, _) if predicate_count > 0 => true,
2367         _ => false,
2368     }
2369 }
2370
2371 fn rewrite_generics(
2372     context: &RewriteContext,
2373     generics: &ast::Generics,
2374     shape: Shape,
2375     span: Span,
2376 ) -> Option<String> {
2377     let g_shape = generics_shape_from_config(context.config, shape, 0)?;
2378     let one_line_width = shape.width.checked_sub(2).unwrap_or(0);
2379     rewrite_generics_inner(context, generics, g_shape, one_line_width, span).or_else(|| {
2380         rewrite_generics_inner(context, generics, g_shape, 0, span)
2381     })
2382 }
2383
2384 fn rewrite_generics_inner(
2385     context: &RewriteContext,
2386     generics: &ast::Generics,
2387     shape: Shape,
2388     one_line_width: usize,
2389     span: Span,
2390 ) -> Option<String> {
2391     // FIXME: convert bounds to where clauses where they get too big or if
2392     // there is a where clause at all.
2393
2394     // Wrapper type
2395     enum GenericsArg<'a> {
2396         Lifetime(&'a ast::LifetimeDef),
2397         TyParam(&'a ast::TyParam),
2398     }
2399     impl<'a> Rewrite for GenericsArg<'a> {
2400         fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
2401             match *self {
2402                 GenericsArg::Lifetime(lifetime) => lifetime.rewrite(context, shape),
2403                 GenericsArg::TyParam(ty) => ty.rewrite(context, shape),
2404             }
2405         }
2406     }
2407     impl<'a> Spanned for GenericsArg<'a> {
2408         fn span(&self) -> Span {
2409             match *self {
2410                 GenericsArg::Lifetime(lifetime) => lifetime.span(),
2411                 GenericsArg::TyParam(ty) => ty.span(),
2412             }
2413         }
2414     }
2415
2416     if generics.lifetimes.is_empty() && generics.ty_params.is_empty() {
2417         return Some(String::new());
2418     }
2419
2420     let generics_args = generics
2421         .lifetimes
2422         .iter()
2423         .map(|lt| GenericsArg::Lifetime(lt))
2424         .chain(generics.ty_params.iter().map(|ty| GenericsArg::TyParam(ty)));
2425     let items = itemize_list(
2426         context.codemap,
2427         generics_args,
2428         ">",
2429         |arg| arg.span().lo(),
2430         |arg| arg.span().hi(),
2431         |arg| arg.rewrite(context, shape),
2432         context.codemap.span_after(span, "<"),
2433         span.hi(),
2434         false,
2435     );
2436     format_generics_item_list(context, items, shape, one_line_width)
2437 }
2438
2439 pub fn generics_shape_from_config(config: &Config, shape: Shape, offset: usize) -> Option<Shape> {
2440     match config.generics_indent() {
2441         IndentStyle::Visual => shape.visual_indent(1 + offset).sub_width(offset + 2),
2442         IndentStyle::Block => {
2443             // 1 = ","
2444             shape
2445                 .block()
2446                 .block_indent(config.tab_spaces())
2447                 .with_max_width(config)
2448                 .sub_width(1)
2449         }
2450     }
2451 }
2452
2453 pub fn format_generics_item_list<I>(
2454     context: &RewriteContext,
2455     items: I,
2456     shape: Shape,
2457     one_line_budget: usize,
2458 ) -> Option<String>
2459 where
2460     I: Iterator<Item = ListItem>,
2461 {
2462     let item_vec = items.collect::<Vec<_>>();
2463
2464     let tactic = definitive_tactic(
2465         &item_vec,
2466         ListTactic::HorizontalVertical,
2467         Separator::Comma,
2468         one_line_budget,
2469     );
2470     let fmt = ListFormatting {
2471         tactic: tactic,
2472         separator: ",",
2473         trailing_separator: if context.config.generics_indent() == IndentStyle::Visual {
2474             SeparatorTactic::Never
2475         } else {
2476             context.config.trailing_comma()
2477         },
2478         separator_place: SeparatorPlace::Back,
2479         shape: shape,
2480         ends_with_newline: tactic.ends_with_newline(context.config.generics_indent()),
2481         preserve_newline: true,
2482         config: context.config,
2483     };
2484
2485     let list_str = write_list(&item_vec, &fmt)?;
2486
2487     Some(wrap_generics_with_angle_brackets(
2488         context,
2489         &list_str,
2490         shape.indent,
2491     ))
2492 }
2493
2494 pub fn wrap_generics_with_angle_brackets(
2495     context: &RewriteContext,
2496     list_str: &str,
2497     list_offset: Indent,
2498 ) -> String {
2499     if context.config.generics_indent() == IndentStyle::Block
2500         && (list_str.contains('\n') || list_str.ends_with(','))
2501     {
2502         format!(
2503             "<\n{}{}\n{}>",
2504             list_offset.to_string(context.config),
2505             list_str,
2506             list_offset
2507                 .block_unindent(context.config)
2508                 .to_string(context.config)
2509         )
2510     } else if context.config.spaces_within_angle_brackets() {
2511         format!("< {} >", list_str)
2512     } else {
2513         format!("<{}>", list_str)
2514     }
2515 }
2516
2517 fn rewrite_trait_bounds(
2518     context: &RewriteContext,
2519     type_param_bounds: &ast::TyParamBounds,
2520     shape: Shape,
2521 ) -> Option<String> {
2522     let bounds: &[_] = type_param_bounds;
2523
2524     if bounds.is_empty() {
2525         return Some(String::new());
2526     }
2527     let bound_str = bounds
2528         .iter()
2529         .map(|ty_bound| ty_bound.rewrite(context, shape))
2530         .collect::<Option<Vec<_>>>()?;
2531     Some(format!(": {}", join_bounds(context, shape, &bound_str)))
2532 }
2533
2534 fn rewrite_where_clause_rfc_style(
2535     context: &RewriteContext,
2536     where_clause: &ast::WhereClause,
2537     shape: Shape,
2538     terminator: &str,
2539     span_end: Option<BytePos>,
2540     span_end_before_where: BytePos,
2541     where_clause_option: WhereClauseOption,
2542     is_args_multi_line: bool,
2543 ) -> Option<String> {
2544     let block_shape = shape.block().with_max_width(context.config);
2545
2546     let (span_before, span_after) =
2547         missing_span_before_after_where(span_end_before_where, where_clause);
2548     let (comment_before, comment_after) =
2549         rewrite_comments_before_after_where(context, span_before, span_after, shape)?;
2550
2551     let starting_newline = if where_clause_option.snuggle && comment_before.is_empty() {
2552         " ".to_owned()
2553     } else {
2554         "\n".to_owned() + &block_shape.indent.to_string(context.config)
2555     };
2556
2557     let clause_shape = block_shape.block_left(context.config.tab_spaces())?;
2558     // 1 = `,`
2559     let clause_shape = clause_shape.sub_width(1)?;
2560     // each clause on one line, trailing comma (except if suppress_comma)
2561     let span_start = where_clause.predicates[0].span().lo();
2562     // If we don't have the start of the next span, then use the end of the
2563     // predicates, but that means we miss comments.
2564     let len = where_clause.predicates.len();
2565     let end_of_preds = where_clause.predicates[len - 1].span().hi();
2566     let span_end = span_end.unwrap_or(end_of_preds);
2567     let items = itemize_list(
2568         context.codemap,
2569         where_clause.predicates.iter(),
2570         terminator,
2571         |pred| pred.span().lo(),
2572         |pred| pred.span().hi(),
2573         |pred| pred.rewrite(context, clause_shape),
2574         span_start,
2575         span_end,
2576         false,
2577     );
2578     let where_single_line = context.config.where_single_line() && len == 1 && !is_args_multi_line;
2579     let comma_tactic = if where_clause_option.suppress_comma || where_single_line {
2580         SeparatorTactic::Never
2581     } else {
2582         context.config.trailing_comma()
2583     };
2584
2585     // shape should be vertical only and only if we have `where_single_line` option enabled
2586     // and the number of items of the where clause is equal to 1
2587     let shape_tactic = if where_single_line {
2588         DefinitiveListTactic::Horizontal
2589     } else {
2590         DefinitiveListTactic::Vertical
2591     };
2592
2593     let fmt = ListFormatting {
2594         tactic: shape_tactic,
2595         separator: ",",
2596         trailing_separator: comma_tactic,
2597         separator_place: SeparatorPlace::Back,
2598         shape: clause_shape,
2599         ends_with_newline: true,
2600         preserve_newline: true,
2601         config: context.config,
2602     };
2603     let preds_str = write_list(&items.collect::<Vec<_>>(), &fmt)?;
2604
2605     let comment_separator = |comment: &str, shape: Shape| if comment.is_empty() {
2606         String::new()
2607     } else {
2608         format!("\n{}", shape.indent.to_string(context.config))
2609     };
2610     let newline_before_where = comment_separator(&comment_before, shape);
2611     let newline_after_where = comment_separator(&comment_after, clause_shape);
2612
2613     // 6 = `where `
2614     let clause_sep = if where_clause_option.compress_where && comment_before.is_empty()
2615         && comment_after.is_empty() && !preds_str.contains('\n')
2616         && 6 + preds_str.len() <= shape.width || where_single_line
2617     {
2618         String::from(" ")
2619     } else {
2620         format!("\n{}", clause_shape.indent.to_string(context.config))
2621     };
2622     Some(format!(
2623         "{}{}{}where{}{}{}{}",
2624         starting_newline,
2625         comment_before,
2626         newline_before_where,
2627         newline_after_where,
2628         comment_after,
2629         clause_sep,
2630         preds_str
2631     ))
2632 }
2633
2634 fn rewrite_where_clause(
2635     context: &RewriteContext,
2636     where_clause: &ast::WhereClause,
2637     brace_style: BraceStyle,
2638     shape: Shape,
2639     density: Density,
2640     terminator: &str,
2641     span_end: Option<BytePos>,
2642     span_end_before_where: BytePos,
2643     where_clause_option: WhereClauseOption,
2644     is_args_multi_line: bool,
2645 ) -> Option<String> {
2646     if where_clause.predicates.is_empty() {
2647         return Some(String::new());
2648     }
2649
2650     if context.config.where_style() == Style::Rfc {
2651         return rewrite_where_clause_rfc_style(
2652             context,
2653             where_clause,
2654             shape,
2655             terminator,
2656             span_end,
2657             span_end_before_where,
2658             where_clause_option,
2659             is_args_multi_line,
2660         );
2661     }
2662
2663     let extra_indent = Indent::new(context.config.tab_spaces(), 0);
2664
2665     let offset = match context.config.where_pred_indent() {
2666         IndentStyle::Block => shape.indent + extra_indent.block_indent(context.config),
2667         // 6 = "where ".len()
2668         IndentStyle::Visual => shape.indent + extra_indent + 6,
2669     };
2670     // FIXME: if where_pred_indent != Visual, then the budgets below might
2671     // be out by a char or two.
2672
2673     let budget = context.config.max_width() - offset.width();
2674     let span_start = where_clause.predicates[0].span().lo();
2675     // If we don't have the start of the next span, then use the end of the
2676     // predicates, but that means we miss comments.
2677     let len = where_clause.predicates.len();
2678     let end_of_preds = where_clause.predicates[len - 1].span().hi();
2679     let span_end = span_end.unwrap_or(end_of_preds);
2680     let items = itemize_list(
2681         context.codemap,
2682         where_clause.predicates.iter(),
2683         terminator,
2684         |pred| pred.span().lo(),
2685         |pred| pred.span().hi(),
2686         |pred| pred.rewrite(context, Shape::legacy(budget, offset)),
2687         span_start,
2688         span_end,
2689         false,
2690     );
2691     let item_vec = items.collect::<Vec<_>>();
2692     // FIXME: we don't need to collect here if the where_layout isn't
2693     // HorizontalVertical.
2694     let tactic = definitive_tactic(
2695         &item_vec,
2696         context.config.where_layout(),
2697         Separator::Comma,
2698         budget,
2699     );
2700
2701     let mut comma_tactic = context.config.trailing_comma();
2702     // Kind of a hack because we don't usually have trailing commas in where clauses.
2703     if comma_tactic == SeparatorTactic::Vertical || where_clause_option.suppress_comma {
2704         comma_tactic = SeparatorTactic::Never;
2705     }
2706
2707     let fmt = ListFormatting {
2708         tactic: tactic,
2709         separator: ",",
2710         trailing_separator: comma_tactic,
2711         separator_place: SeparatorPlace::Back,
2712         shape: Shape::legacy(budget, offset),
2713         ends_with_newline: tactic.ends_with_newline(context.config.where_pred_indent()),
2714         preserve_newline: true,
2715         config: context.config,
2716     };
2717     let preds_str = write_list(&item_vec, &fmt)?;
2718
2719     let end_length = if terminator == "{" {
2720         // If the brace is on the next line we don't need to count it otherwise it needs two
2721         // characters " {"
2722         match brace_style {
2723             BraceStyle::AlwaysNextLine | BraceStyle::SameLineWhere => 0,
2724             BraceStyle::PreferSameLine => 2,
2725         }
2726     } else if terminator == "=" {
2727         2
2728     } else {
2729         terminator.len()
2730     };
2731     if density == Density::Tall || preds_str.contains('\n')
2732         || shape.indent.width() + " where ".len() + preds_str.len() + end_length > shape.width
2733     {
2734         Some(format!(
2735             "\n{}where {}",
2736             (shape.indent + extra_indent).to_string(context.config),
2737             preds_str
2738         ))
2739     } else {
2740         Some(format!(" where {}", preds_str))
2741     }
2742 }
2743
2744 fn missing_span_before_after_where(
2745     before_item_span_end: BytePos,
2746     where_clause: &ast::WhereClause,
2747 ) -> (Span, Span) {
2748     let missing_span_before = mk_sp(before_item_span_end, where_clause.span.lo());
2749     // 5 = `where`
2750     let pos_after_where = where_clause.span.lo() + BytePos(5);
2751     let missing_span_after = mk_sp(pos_after_where, where_clause.predicates[0].span().lo());
2752     (missing_span_before, missing_span_after)
2753 }
2754
2755 fn rewrite_comments_before_after_where(
2756     context: &RewriteContext,
2757     span_before_where: Span,
2758     span_after_where: Span,
2759     shape: Shape,
2760 ) -> Option<(String, String)> {
2761     let before_comment = rewrite_missing_comment(span_before_where, shape, context)?;
2762     let after_comment = rewrite_missing_comment(
2763         span_after_where,
2764         shape.block_indent(context.config.tab_spaces()),
2765         context,
2766     )?;
2767     Some((before_comment, after_comment))
2768 }
2769
2770 fn format_header(item_name: &str, ident: ast::Ident, vis: &ast::Visibility) -> String {
2771     format!("{}{}{}", format_visibility(vis), item_name, ident)
2772 }
2773
2774 fn format_generics(
2775     context: &RewriteContext,
2776     generics: &ast::Generics,
2777     brace_style: BraceStyle,
2778     force_same_line_brace: bool,
2779     offset: Indent,
2780     span: Span,
2781     used_width: usize,
2782 ) -> Option<String> {
2783     let shape = Shape::legacy(context.budget(used_width + offset.width()), offset);
2784     let mut result = rewrite_generics(context, generics, shape, span)?;
2785
2786     let same_line_brace = if !generics.where_clause.predicates.is_empty() || result.contains('\n') {
2787         let budget = context.budget(last_line_used_width(&result, offset.width()));
2788         let option = WhereClauseOption::snuggled(&result);
2789         // If the generics are not parameterized then generics.span.hi() == 0,
2790         // so we use span.lo(), which is the position after `struct Foo`.
2791         let span_end_before_where = if generics.is_parameterized() {
2792             generics.span.hi()
2793         } else {
2794             span.lo()
2795         };
2796         let where_clause_str = rewrite_where_clause(
2797             context,
2798             &generics.where_clause,
2799             brace_style,
2800             Shape::legacy(budget, offset.block_only()),
2801             Density::Tall,
2802             "{",
2803             Some(span.hi()),
2804             span_end_before_where,
2805             option,
2806             false,
2807         )?;
2808         result.push_str(&where_clause_str);
2809         force_same_line_brace || brace_style == BraceStyle::PreferSameLine
2810             || (generics.where_clause.predicates.is_empty()
2811                 && trimmed_last_line_width(&result) == 1)
2812     } else {
2813         force_same_line_brace || trimmed_last_line_width(&result) == 1
2814             || brace_style != BraceStyle::AlwaysNextLine
2815     };
2816     let total_used_width = last_line_used_width(&result, used_width);
2817     let remaining_budget = context.budget(total_used_width);
2818     // If the same line brace if forced, it indicates that we are rewriting an item with empty body,
2819     // and hence we take the closer into account as well for one line budget.
2820     // We assume that the closer has the same length as the opener.
2821     let overhead = if force_same_line_brace {
2822         // 3 = ` {}`
2823         3
2824     } else {
2825         // 2 = ` {`
2826         2
2827     };
2828     let forbid_same_line_brace = overhead > remaining_budget;
2829     if !forbid_same_line_brace && same_line_brace {
2830         result.push(' ');
2831     } else {
2832         result.push('\n');
2833         result.push_str(&offset.block_only().to_string(context.config));
2834     }
2835     result.push('{');
2836
2837     Some(result)
2838 }
2839
2840 impl Rewrite for ast::ForeignItem {
2841     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
2842         let attrs_str = self.attrs.rewrite(context, shape)?;
2843         // Drop semicolon or it will be interpreted as comment.
2844         // FIXME: this may be a faulty span from libsyntax.
2845         let span = mk_sp(self.span.lo(), self.span.hi() - BytePos(1));
2846
2847         let item_str = match self.node {
2848             ast::ForeignItemKind::Fn(ref fn_decl, ref generics) => {
2849                 rewrite_fn_base(
2850                     context,
2851                     shape.indent,
2852                     self.ident,
2853                     &FnSig::new(fn_decl, generics, self.vis.clone()),
2854                     span,
2855                     false,
2856                     false,
2857                 ).map(|(s, _)| format!("{};", s))
2858             }
2859             ast::ForeignItemKind::Static(ref ty, is_mutable) => {
2860                 // FIXME(#21): we're dropping potential comments in between the
2861                 // function keywords here.
2862                 let vis = format_visibility(&self.vis);
2863                 let mut_str = if is_mutable { "mut " } else { "" };
2864                 let prefix = format!("{}static {}{}:", vis, mut_str, self.ident);
2865                 // 1 = ;
2866                 let shape = shape.sub_width(1)?;
2867                 ty.rewrite(context, shape).map(|ty_str| {
2868                     // 1 = space between prefix and type.
2869                     let sep = if prefix.len() + ty_str.len() + 1 <= shape.width {
2870                         String::from(" ")
2871                     } else {
2872                         let nested_indent = shape.indent.block_indent(context.config);
2873                         format!("\n{}", nested_indent.to_string(context.config))
2874                     };
2875                     format!("{}{}{};", prefix, sep, ty_str)
2876                 })
2877             }
2878             ast::ForeignItemKind::Ty => {
2879                 let vis = format_visibility(&self.vis);
2880                 Some(format!("{}type {};", vis, self.ident))
2881             }
2882         }?;
2883
2884         let missing_span = if self.attrs.is_empty() {
2885             mk_sp(self.span.lo(), self.span.lo())
2886         } else {
2887             mk_sp(self.attrs[self.attrs.len() - 1].span.hi(), self.span.lo())
2888         };
2889         combine_strs_with_missing_comments(
2890             context,
2891             &attrs_str,
2892             &item_str,
2893             missing_span,
2894             shape,
2895             false,
2896         )
2897     }
2898 }