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