src/types.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 use std::iter::ExactSizeIterator;
  12 use std::ops::Deref;
  13
  14 use config::lists::*;
  15 use syntax::ast::{self, FunctionRetTy, Mutability};
  16 use syntax::source_map::{self, BytePos, Span};
  17 use syntax::symbol::keywords;
  18
  19 use config::{IndentStyle, TypeDensity};
  20 use expr::{rewrite_assign_rhs, rewrite_tuple, rewrite_unary_prefix};
  21 use lists::{definitive_tactic, itemize_list, write_list, ListFormatting, Separator};
  22 use macros::{rewrite_macro, MacroPosition};
  23 use overflow;
  24 use pairs::{rewrite_pair, PairParts};
  25 use rewrite::{Rewrite, RewriteContext};
  26 use shape::Shape;
  27 use source_map::SpanUtils;
  28 use spanned::Spanned;
  29 use utils::{
  30     colon_spaces, extra_offset, first_line_width, format_abi, format_mutability,
  31     last_line_extendable, last_line_width, mk_sp, rewrite_ident,
  32 };
  33
  34 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
  35 pub enum PathContext {
  36     Expr,
  37     Type,
  38     Import,
  39 }
  40
  41 // Does not wrap on simple segments.
  42 pub fn rewrite_path(
  43     context: &RewriteContext,
  44     path_context: PathContext,
  45     qself: Option<&ast::QSelf>,
  46     path: &ast::Path,
  47     shape: Shape,
  48 ) -> Option<String> {
  49     let skip_count = qself.map_or(0, |x| x.position);
  50
  51     let mut result = if path.is_global() && qself.is_none() && path_context != PathContext::Import {
  52         "::".to_owned()
  53     } else {
  54         String::new()
  55     };
  56
  57     let mut span_lo = path.span.lo();
  58
  59     if let Some(qself) = qself {
  60         result.push('<');
  61
  62         let fmt_ty = qself.ty.rewrite(context, shape)?;
  63         result.push_str(&fmt_ty);
  64
  65         if skip_count > 0 {
  66             result.push_str(" as ");
  67             if path.is_global() && path_context != PathContext::Import {
  68                 result.push_str("::");
  69             }
  70
  71             // 3 = ">::".len()
  72             let shape = shape.sub_width(3)?;
  73
  74             result = rewrite_path_segments(
  75                 PathContext::Type,
  76                 result,
  77                 path.segments.iter().take(skip_count),
  78                 span_lo,
  79                 path.span.hi(),
  80                 context,
  81                 shape,
  82             )?;
  83         }
  84
  85         result.push_str(">::");
  86         span_lo = qself.ty.span.hi() + BytePos(1);
  87     }
  88
  89     rewrite_path_segments(
  90         path_context,
  91         result,
  92         path.segments.iter().skip(skip_count),
  93         span_lo,
  94         path.span.hi(),
  95         context,
  96         shape,
  97     )
  98 }
  99
 100 fn rewrite_path_segments<'a, I>(
 101     path_context: PathContext,
 102     mut buffer: String,
 103     iter: I,
 104     mut span_lo: BytePos,
 105     span_hi: BytePos,
 106     context: &RewriteContext,
 107     shape: Shape,
 108 ) -> Option<String>
 109 where
 110     I: Iterator<Item = &'a ast::PathSegment>,
 111 {
 112     let mut first = true;
 113     let shape = shape.visual_indent(0);
 114
 115     for segment in iter {
 116         // Indicates a global path, shouldn't be rendered.
 117         if segment.ident.name == keywords::CrateRoot.name() {
 118             continue;
 119         }
 120         if first {
 121             first = false;
 122         } else {
 123             buffer.push_str("::");
 124         }
 125
 126         let extra_offset = extra_offset(&buffer, shape);
 127         let new_shape = shape.shrink_left(extra_offset)?;
 128         let segment_string = rewrite_segment(
 129             path_context,
 130             segment,
 131             &mut span_lo,
 132             span_hi,
 133             context,
 134             new_shape,
 135         )?;
 136
 137         buffer.push_str(&segment_string);
 138     }
 139
 140     Some(buffer)
 141 }
 142
 143 #[derive(Debug)]
 144 pub enum SegmentParam<'a> {
 145     LifeTime(&'a ast::Lifetime),
 146     Type(&'a ast::Ty),
 147     Binding(&'a ast::TypeBinding),
 148 }
 149
 150 impl<'a> SegmentParam<'a> {
 151     fn from_generic_arg(arg: &ast::GenericArg) -> SegmentParam {
 152         match arg {
 153             ast::GenericArg::Lifetime(ref lt) => SegmentParam::LifeTime(lt),
 154             ast::GenericArg::Type(ref ty) => SegmentParam::Type(ty),
 155         }
 156     }
 157 }
 158
 159 impl<'a> Spanned for SegmentParam<'a> {
 160     fn span(&self) -> Span {
 161         match *self {
 162             SegmentParam::LifeTime(lt) => lt.ident.span,
 163             SegmentParam::Type(ty) => ty.span,
 164             SegmentParam::Binding(binding) => binding.span,
 165         }
 166     }
 167 }
 168
 169 impl<'a> Rewrite for SegmentParam<'a> {
 170     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 171         match *self {
 172             SegmentParam::LifeTime(lt) => lt.rewrite(context, shape),
 173             SegmentParam::Type(ty) => ty.rewrite(context, shape),
 174             SegmentParam::Binding(binding) => {
 175                 let mut result = match context.config.type_punctuation_density() {
 176                     TypeDensity::Wide => format!("{} = ", rewrite_ident(context, binding.ident)),
 177                     TypeDensity::Compressed => {
 178                         format!("{}=", rewrite_ident(context, binding.ident))
 179                     }
 180                 };
 181                 let budget = shape.width.checked_sub(result.len())?;
 182                 let rewrite = binding
 183                     .ty
 184                     .rewrite(context, Shape::legacy(budget, shape.indent + result.len()))?;
 185                 result.push_str(&rewrite);
 186                 Some(result)
 187             }
 188         }
 189     }
 190 }
 191
 192 // Formats a path segment. There are some hacks involved to correctly determine
 193 // the segment's associated span since it's not part of the AST.
 194 //
 195 // The span_lo is assumed to be greater than the end of any previous segment's
 196 // parameters and lesser or equal than the start of current segment.
 197 //
 198 // span_hi is assumed equal to the end of the entire path.
 199 //
 200 // When the segment contains a positive number of parameters, we update span_lo
 201 // so that invariants described above will hold for the next segment.
 202 fn rewrite_segment(
 203     path_context: PathContext,
 204     segment: &ast::PathSegment,
 205     span_lo: &mut BytePos,
 206     span_hi: BytePos,
 207     context: &RewriteContext,
 208     shape: Shape,
 209 ) -> Option<String> {
 210     let mut result = String::with_capacity(128);
 211     result.push_str(rewrite_ident(context, segment.ident));
 212
 213     let ident_len = result.len();
 214     let shape = if context.use_block_indent() {
 215         shape.offset_left(ident_len)?
 216     } else {
 217         shape.shrink_left(ident_len)?
 218     };
 219
 220     if let Some(ref args) = segment.args {
 221         match **args {
 222             ast::GenericArgs::AngleBracketed(ref data)
 223                 if !data.args.is_empty() || !data.bindings.is_empty() =>
 224             {
 225                 let param_list = data
 226                     .args
 227                     .iter()
 228                     .map(SegmentParam::from_generic_arg)
 229                     .chain(data.bindings.iter().map(|x| SegmentParam::Binding(&*x)))
 230                     .collect::<Vec<_>>();
 231
 232                 let force_separator =
 233                     context.inside_macro() && context.snippet(data.span).starts_with("::");
 234                 let separator = if path_context == PathContext::Expr || force_separator {
 235                     "::"
 236                 } else {
 237                     ""
 238                 };
 239                 result.push_str(separator);
 240
 241                 let generics_str = overflow::rewrite_with_angle_brackets(
 242                     context,
 243                     "",
 244                     param_list.iter(),
 245                     shape,
 246                     mk_sp(*span_lo, span_hi),
 247                 )?;
 248
 249                 // Update position of last bracket.
 250                 *span_lo = context
 251                     .snippet_provider
 252                     .span_after(mk_sp(*span_lo, span_hi), "<");
 253
 254                 result.push_str(&generics_str)
 255             }
 256             ast::GenericArgs::Parenthesized(ref data) => {
 257                 let output = match data.output {
 258                     Some(ref ty) => FunctionRetTy::Ty(ty.clone()),
 259                     None => FunctionRetTy::Default(source_map::DUMMY_SP),
 260                 };
 261                 result.push_str(&format_function_type(
 262                     data.inputs.iter().map(|x| &**x),
 263                     &output,
 264                     false,
 265                     data.span,
 266                     context,
 267                     shape,
 268                 )?);
 269             }
 270             _ => (),
 271         }
 272     }
 273
 274     Some(result)
 275 }
 276
 277 fn format_function_type<'a, I>(
 278     inputs: I,
 279     output: &FunctionRetTy,
 280     variadic: bool,
 281     span: Span,
 282     context: &RewriteContext,
 283     shape: Shape,
 284 ) -> Option<String>
 285 where
 286     I: ExactSizeIterator,
 287     <I as Iterator>::Item: Deref,
 288     <I::Item as Deref>::Target: Rewrite + Spanned + 'a,
 289 {
 290     debug!("format_function_type {:#?}", shape);
 291
 292     // Code for handling variadics is somewhat duplicated for items, but they
 293     // are different enough to need some serious refactoring to share code.
 294     enum ArgumentKind<T>
 295     where
 296         T: Deref,
 297         <T as Deref>::Target: Rewrite + Spanned,
 298     {
 299         Regular(T),
 300         Variadic(BytePos),
 301     }
 302
 303     let variadic_arg = if variadic {
 304         let variadic_start = context.snippet_provider.span_before(span, "...");
 305         Some(ArgumentKind::Variadic(variadic_start))
 306     } else {
 307         None
 308     };
 309
 310     // 2 for ()
 311     let budget = shape.width.checked_sub(2)?;
 312     // 1 for (
 313     let offset = match context.config.indent_style() {
 314         IndentStyle::Block => {
 315             shape
 316                 .block()
 317                 .block_indent(context.config.tab_spaces())
 318                 .indent
 319         }
 320         IndentStyle::Visual => shape.indent + 1,
 321     };
 322     let list_shape = Shape::legacy(budget, offset);
 323     let list_lo = context.snippet_provider.span_after(span, "(");
 324     let items = itemize_list(
 325         context.snippet_provider,
 326         inputs.map(ArgumentKind::Regular).chain(variadic_arg),
 327         ")",
 328         ",",
 329         |arg| match *arg {
 330             ArgumentKind::Regular(ref ty) => ty.span().lo(),
 331             ArgumentKind::Variadic(start) => start,
 332         },
 333         |arg| match *arg {
 334             ArgumentKind::Regular(ref ty) => ty.span().hi(),
 335             ArgumentKind::Variadic(start) => start + BytePos(3),
 336         },
 337         |arg| match *arg {
 338             ArgumentKind::Regular(ref ty) => ty.rewrite(context, list_shape),
 339             ArgumentKind::Variadic(_) => Some("...".to_owned()),
 340         },
 341         list_lo,
 342         span.hi(),
 343         false,
 344     );
 345
 346     let item_vec: Vec<_> = items.collect();
 347
 348     let tactic = definitive_tactic(
 349         &*item_vec,
 350         ListTactic::HorizontalVertical,
 351         Separator::Comma,
 352         budget,
 353     );
 354     let trailing_separator = if !context.use_block_indent() || variadic {
 355         SeparatorTactic::Never
 356     } else {
 357         context.config.trailing_comma()
 358     };
 359
 360     let fmt = ListFormatting::new(list_shape, context.config)
 361         .tactic(tactic)
 362         .trailing_separator(trailing_separator)
 363         .ends_with_newline(tactic.ends_with_newline(context.config.indent_style()))
 364         .preserve_newline(true);
 365     let list_str = write_list(&item_vec, &fmt)?;
 366
 367     let ty_shape = match context.config.indent_style() {
 368         // 4 = " -> "
 369         IndentStyle::Block => shape.offset_left(4)?,
 370         IndentStyle::Visual => shape.block_left(4)?,
 371     };
 372     let output = match *output {
 373         FunctionRetTy::Ty(ref ty) => {
 374             let type_str = ty.rewrite(context, ty_shape)?;
 375             format!(" -> {}", type_str)
 376         }
 377         FunctionRetTy::Default(..) => String::new(),
 378     };
 379
 380     let args = if (!list_str.contains('\n') || list_str.is_empty()) && !output.contains('\n')
 381         || !context.use_block_indent()
 382     {
 383         format!("({})", list_str)
 384     } else {
 385         format!(
 386             "({}{}{})",
 387             offset.to_string_with_newline(context.config),
 388             list_str,
 389             shape.block().indent.to_string_with_newline(context.config),
 390         )
 391     };
 392     if output.is_empty() || last_line_width(&args) + first_line_width(&output) <= shape.width {
 393         Some(format!("{}{}", args, output))
 394     } else {
 395         Some(format!(
 396             "{}\n{}{}",
 397             args,
 398             offset.to_string(context.config),
 399             output.trim_left()
 400         ))
 401     }
 402 }
 403
 404 fn type_bound_colon(context: &RewriteContext) -> &'static str {
 405     colon_spaces(
 406         context.config.space_before_colon(),
 407         context.config.space_after_colon(),
 408     )
 409 }
 410
 411 impl Rewrite for ast::WherePredicate {
 412     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 413         // FIXME: dead spans?
 414         let result = match *self {
 415             ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
 416                 ref bound_generic_params,
 417                 ref bounded_ty,
 418                 ref bounds,
 419                 ..
 420             }) => {
 421                 let type_str = bounded_ty.rewrite(context, shape)?;
 422                 let colon = type_bound_colon(context).trim_right();
 423                 let lhs = if let Some(lifetime_str) =
 424                     rewrite_lifetime_param(context, shape, bound_generic_params)
 425                 {
 426                     format!("for<{}> {}{}", lifetime_str, type_str, colon)
 427                 } else {
 428                     format!("{}{}", type_str, colon)
 429                 };
 430
 431                 rewrite_assign_rhs(context, lhs, bounds, shape)?
 432             }
 433             ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate {
 434                 ref lifetime,
 435                 ref bounds,
 436                 ..
 437             }) => rewrite_bounded_lifetime(lifetime, bounds, context, shape)?,
 438             ast::WherePredicate::EqPredicate(ast::WhereEqPredicate {
 439                 ref lhs_ty,
 440                 ref rhs_ty,
 441                 ..
 442             }) => {
 443                 let lhs_ty_str = lhs_ty.rewrite(context, shape).map(|lhs| lhs + " =")?;
 444                 rewrite_assign_rhs(context, lhs_ty_str, &**rhs_ty, shape)?
 445             }
 446         };
 447
 448         Some(result)
 449     }
 450 }
 451
 452 impl Rewrite for ast::GenericArg {
 453     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 454         match *self {
 455             ast::GenericArg::Lifetime(ref lt) => lt.rewrite(context, shape),
 456             ast::GenericArg::Type(ref ty) => ty.rewrite(context, shape),
 457         }
 458     }
 459 }
 460
 461 fn rewrite_bounded_lifetime(
 462     lt: &ast::Lifetime,
 463     bounds: &[ast::GenericBound],
 464     context: &RewriteContext,
 465     shape: Shape,
 466 ) -> Option<String> {
 467     let result = lt.rewrite(context, shape)?;
 468
 469     if bounds.is_empty() {
 470         Some(result)
 471     } else {
 472         let colon = type_bound_colon(context);
 473         let overhead = last_line_width(&result) + colon.len();
 474         let result = format!(
 475             "{}{}{}",
 476             result,
 477             colon,
 478             join_bounds(context, shape.sub_width(overhead)?, bounds, true)?
 479         );
 480         Some(result)
 481     }
 482 }
 483
 484 impl Rewrite for ast::Lifetime {
 485     fn rewrite(&self, context: &RewriteContext, _: Shape) -> Option<String> {
 486         Some(rewrite_ident(context, self.ident).to_owned())
 487     }
 488 }
 489
 490 impl Rewrite for ast::GenericBound {
 491     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 492         match *self {
 493             ast::GenericBound::Trait(ref poly_trait_ref, trait_bound_modifier) => {
 494                 let snippet = context.snippet(self.span());
 495                 let has_paren = snippet.starts_with("(") && snippet.ends_with(")");
 496                 let rewrite = match trait_bound_modifier {
 497                     ast::TraitBoundModifier::None => poly_trait_ref.rewrite(context, shape),
 498                     ast::TraitBoundModifier::Maybe => poly_trait_ref
 499                         .rewrite(context, shape.offset_left(1)?)
 500                         .map(|s| format!("?{}", s)),
 501                 };
 502                 rewrite.map(|s| if has_paren { format!("({})", s) } else { s })
 503             }
 504             ast::GenericBound::Outlives(ref lifetime) => lifetime.rewrite(context, shape),
 505         }
 506     }
 507 }
 508
 509 impl Rewrite for ast::GenericBounds {
 510     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 511         if self.is_empty() {
 512             return Some(String::new());
 513         }
 514
 515         join_bounds(context, shape, self, true)
 516     }
 517 }
 518
 519 impl Rewrite for ast::GenericParam {
 520     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 521         let mut result = String::with_capacity(128);
 522         // FIXME: If there are more than one attributes, this will force multiline.
 523         match self.attrs.rewrite(context, shape) {
 524             Some(ref rw) if !rw.is_empty() => result.push_str(&format!("{} ", rw)),
 525             _ => (),
 526         }
 527         result.push_str(rewrite_ident(context, self.ident));
 528         if !self.bounds.is_empty() {
 529             result.push_str(type_bound_colon(context));
 530             result.push_str(&self.bounds.rewrite(context, shape)?)
 531         }
 532         if let ast::GenericParamKind::Type {
 533             default: Some(ref def),
 534         } = self.kind
 535         {
 536             let eq_str = match context.config.type_punctuation_density() {
 537                 TypeDensity::Compressed => "=",
 538                 TypeDensity::Wide => " = ",
 539             };
 540             result.push_str(eq_str);
 541             let budget = shape.width.checked_sub(result.len())?;
 542             let rewrite =
 543                 def.rewrite(context, Shape::legacy(budget, shape.indent + result.len()))?;
 544             result.push_str(&rewrite);
 545         }
 546
 547         Some(result)
 548     }
 549 }
 550
 551 impl Rewrite for ast::PolyTraitRef {
 552     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 553         if let Some(lifetime_str) =
 554             rewrite_lifetime_param(context, shape, &self.bound_generic_params)
 555         {
 556             // 6 is "for<> ".len()
 557             let extra_offset = lifetime_str.len() + 6;
 558             let path_str = self
 559                 .trait_ref
 560                 .rewrite(context, shape.offset_left(extra_offset)?)?;
 561
 562             Some(format!("for<{}> {}", lifetime_str, path_str))
 563         } else {
 564             self.trait_ref.rewrite(context, shape)
 565         }
 566     }
 567 }
 568
 569 impl Rewrite for ast::TraitRef {
 570     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 571         rewrite_path(context, PathContext::Type, None, &self.path, shape)
 572     }
 573 }
 574
 575 impl Rewrite for ast::Ty {
 576     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 577         match self.node {
 578             ast::TyKind::TraitObject(ref bounds, tobj_syntax) => {
 579                 // we have to consider 'dyn' keyword is used or not!!!
 580                 let is_dyn = tobj_syntax == ast::TraitObjectSyntax::Dyn;
 581                 // 4 is length of 'dyn '
 582                 let shape = if is_dyn { shape.offset_left(4)? } else { shape };
 583                 let res = bounds.rewrite(context, shape)?;
 584                 if is_dyn {
 585                     Some(format!("dyn {}", res))
 586                 } else {
 587                     Some(res)
 588                 }
 589             }
 590             ast::TyKind::Ptr(ref mt) => {
 591                 let prefix = match mt.mutbl {
 592                     Mutability::Mutable => "*mut ",
 593                     Mutability::Immutable => "*const ",
 594                 };
 595
 596                 rewrite_unary_prefix(context, prefix, &*mt.ty, shape)
 597             }
 598             ast::TyKind::Rptr(ref lifetime, ref mt) => {
 599                 let mut_str = format_mutability(mt.mutbl);
 600                 let mut_len = mut_str.len();
 601                 Some(match *lifetime {
 602                     Some(ref lifetime) => {
 603                         let lt_budget = shape.width.checked_sub(2 + mut_len)?;
 604                         let lt_str = lifetime.rewrite(
 605                             context,
 606                             Shape::legacy(lt_budget, shape.indent + 2 + mut_len),
 607                         )?;
 608                         let lt_len = lt_str.len();
 609                         let budget = shape.width.checked_sub(2 + mut_len + lt_len)?;
 610                         format!(
 611                             "&{} {}{}",
 612                             lt_str,
 613                             mut_str,
 614                             mt.ty.rewrite(
 615                                 context,
 616                                 Shape::legacy(budget, shape.indent + 2 + mut_len + lt_len)
 617                             )?
 618                         )
 619                     }
 620                     None => {
 621                         let budget = shape.width.checked_sub(1 + mut_len)?;
 622                         format!(
 623                             "&{}{}",
 624                             mut_str,
 625                             mt.ty.rewrite(
 626                                 context,
 627                                 Shape::legacy(budget, shape.indent + 1 + mut_len)
 628                             )?
 629                         )
 630                     }
 631                 })
 632             }
 633             // FIXME: we drop any comments here, even though it's a silly place to put
 634             // comments.
 635             ast::TyKind::Paren(ref ty) => {
 636                 let budget = shape.width.checked_sub(2)?;
 637                 ty.rewrite(context, Shape::legacy(budget, shape.indent + 1))
 638                     .map(|ty_str| format!("({})", ty_str))
 639             }
 640             ast::TyKind::Slice(ref ty) => {
 641                 let budget = shape.width.checked_sub(4)?;
 642                 ty.rewrite(context, Shape::legacy(budget, shape.indent + 1))
 643                     .map(|ty_str| format!("[{}]", ty_str))
 644             }
 645             ast::TyKind::Tup(ref items) => {
 646                 rewrite_tuple(context, items.iter(), self.span, shape, items.len() == 1)
 647             }
 648             ast::TyKind::Path(ref q_self, ref path) => {
 649                 rewrite_path(context, PathContext::Type, q_self.as_ref(), path, shape)
 650             }
 651             ast::TyKind::Array(ref ty, ref repeats) => rewrite_pair(
 652                 &**ty,
 653                 &*repeats.value,
 654                 PairParts::new("[", "; ", "]"),
 655                 context,
 656                 shape,
 657                 SeparatorPlace::Back,
 658             ),
 659             ast::TyKind::Infer => {
 660                 if shape.width >= 1 {
 661                     Some("_".to_owned())
 662                 } else {
 663                     None
 664                 }
 665             }
 666             ast::TyKind::BareFn(ref bare_fn) => rewrite_bare_fn(bare_fn, self.span, context, shape),
 667             ast::TyKind::Never => Some(String::from("!")),
 668             ast::TyKind::Mac(ref mac) => {
 669                 rewrite_macro(mac, None, context, shape, MacroPosition::Expression)
 670             }
 671             ast::TyKind::ImplicitSelf => Some(String::from("")),
 672             ast::TyKind::ImplTrait(_, ref it) => it
 673                 .rewrite(context, shape)
 674                 .map(|it_str| format!("impl {}", it_str)),
 675             ast::TyKind::Err | ast::TyKind::Typeof(..) => unreachable!(),
 676         }
 677     }
 678 }
 679
 680 fn rewrite_bare_fn(
 681     bare_fn: &ast::BareFnTy,
 682     span: Span,
 683     context: &RewriteContext,
 684     shape: Shape,
 685 ) -> Option<String> {
 686     debug!("rewrite_bare_fn {:#?}", shape);
 687
 688     let mut result = String::with_capacity(128);
 689
 690     if let Some(ref lifetime_str) = rewrite_lifetime_param(context, shape, &bare_fn.generic_params)
 691     {
 692         result.push_str("for<");
 693         // 6 = "for<> ".len(), 4 = "for<".
 694         // This doesn't work out so nicely for multiline situation with lots of
 695         // rightward drift. If that is a problem, we could use the list stuff.
 696         result.push_str(lifetime_str);
 697         result.push_str("> ");
 698     }
 699
 700     result.push_str(::utils::format_unsafety(bare_fn.unsafety));
 701
 702     result.push_str(&format_abi(
 703         bare_fn.abi,
 704         context.config.force_explicit_abi(),
 705         false,
 706     ));
 707
 708     result.push_str("fn");
 709
 710     let func_ty_shape = if context.use_block_indent() {
 711         shape.offset_left(result.len())?
 712     } else {
 713         shape.visual_indent(result.len()).sub_width(result.len())?
 714     };
 715
 716     let rewrite = format_function_type(
 717         bare_fn.decl.inputs.iter(),
 718         &bare_fn.decl.output,
 719         bare_fn.decl.variadic,
 720         span,
 721         context,
 722         func_ty_shape,
 723     )?;
 724
 725     result.push_str(&rewrite);
 726
 727     Some(result)
 728 }
 729
 730 fn is_generic_bounds_in_order(generic_bounds: &[ast::GenericBound]) -> bool {
 731     let is_trait = |b: &ast::GenericBound| match b {
 732         ast::GenericBound::Outlives(..) => false,
 733         ast::GenericBound::Trait(..) => true,
 734     };
 735     let is_lifetime = |b: &ast::GenericBound| !is_trait(b);
 736     let last_trait_index = generic_bounds.iter().rposition(is_trait);
 737     let first_lifetime_index = generic_bounds.iter().position(is_lifetime);
 738     match (last_trait_index, first_lifetime_index) {
 739         (Some(last_trait_index), Some(first_lifetime_index)) => {
 740             last_trait_index < first_lifetime_index
 741         }
 742         _ => true,
 743     }
 744 }
 745
 746 fn join_bounds(
 747     context: &RewriteContext,
 748     shape: Shape,
 749     items: &[ast::GenericBound],
 750     need_indent: bool,
 751 ) -> Option<String> {
 752     debug_assert!(!items.is_empty());
 753
 754     // Try to join types in a single line
 755     let joiner = match context.config.type_punctuation_density() {
 756         TypeDensity::Compressed => "+",
 757         TypeDensity::Wide => " + ",
 758     };
 759     let type_strs = items
 760         .iter()
 761         .map(|item| item.rewrite(context, shape))
 762         .collect::<Option<Vec<_>>>()?;
 763     let result = type_strs.join(joiner);
 764     if items.len() <= 1 || (!result.contains('\n') && result.len() <= shape.width) {
 765         return Some(result);
 766     }
 767
 768     // We need to use multiple lines.
 769     let (type_strs, offset) = if need_indent {
 770         // Rewrite with additional indentation.
 771         let nested_shape = shape.block_indent(context.config.tab_spaces());
 772         let type_strs = items
 773             .iter()
 774             .map(|item| item.rewrite(context, nested_shape))
 775             .collect::<Option<Vec<_>>>()?;
 776         (type_strs, nested_shape.indent)
 777     } else {
 778         (type_strs, shape.indent)
 779     };
 780
 781     let is_bound_extendable = |s: &str, b: &ast::GenericBound| match b {
 782         ast::GenericBound::Outlives(..) => true,
 783         ast::GenericBound::Trait(..) => last_line_extendable(s),
 784     };
 785     let mut result = String::with_capacity(128);
 786     result.push_str(&type_strs[0]);
 787     let mut can_be_put_on_the_same_line = is_bound_extendable(&result, &items[0]);
 788     let generic_bounds_in_order = is_generic_bounds_in_order(items);
 789     for (bound, bound_str) in items[1..].iter().zip(type_strs[1..].iter()) {
 790         if generic_bounds_in_order && can_be_put_on_the_same_line {
 791             result.push_str(joiner);
 792         } else {
 793             result.push_str(&offset.to_string_with_newline(context.config));
 794             result.push_str("+ ");
 795         }
 796         result.push_str(bound_str);
 797         can_be_put_on_the_same_line = is_bound_extendable(bound_str, bound);
 798     }
 799
 800     Some(result)
 801 }
 802
 803 pub fn can_be_overflowed_type(context: &RewriteContext, ty: &ast::Ty, len: usize) -> bool {
 804     match ty.node {
 805         ast::TyKind::Tup(..) => context.use_block_indent() && len == 1,
 806         ast::TyKind::Rptr(_, ref mutty) | ast::TyKind::Ptr(ref mutty) => {
 807             can_be_overflowed_type(context, &*mutty.ty, len)
 808         }
 809         _ => false,
 810     }
 811 }
 812
 813 /// Returns `None` if there is no `LifetimeDef` in the given generic parameters.
 814 fn rewrite_lifetime_param(
 815     context: &RewriteContext,
 816     shape: Shape,
 817     generic_params: &[ast::GenericParam],
 818 ) -> Option<String> {
 819     let result = generic_params
 820         .iter()
 821         .filter(|p| match p.kind {
 822             ast::GenericParamKind::Lifetime => true,
 823             _ => false,
 824         })
 825         .map(|lt| lt.rewrite(context, shape))
 826         .collect::<Option<Vec<_>>>()?
 827         .join(", ");
 828     if result.is_empty() {
 829         None
 830     } else {
 831         Some(result)
 832     }
 833 }