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::codemap::{self, BytePos, Span};
  17 use syntax::symbol::keywords;
  18
  19 use codemap::SpanUtils;
  20 use config::{IndentStyle, TypeDensity};
  21 use expr::{rewrite_assign_rhs, rewrite_tuple, rewrite_unary_prefix, ToExpr};
  22 use lists::{definitive_tactic, itemize_list, write_list, ListFormatting, Separator};
  23 use macros::{rewrite_macro, MacroPosition};
  24 use overflow;
  25 use pairs::{rewrite_pair, PairParts};
  26 use rewrite::{Rewrite, RewriteContext};
  27 use shape::Shape;
  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 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> ToExpr for SegmentParam<'a> {
 170     fn to_expr(&self) -> Option<&ast::Expr> {
 171         None
 172     }
 173
 174     fn can_be_overflowed(&self, context: &RewriteContext, len: usize) -> bool {
 175         match *self {
 176             SegmentParam::Type(ty) => ty.can_be_overflowed(context, len),
 177             _ => false,
 178         }
 179     }
 180 }
 181
 182 impl<'a> Rewrite for SegmentParam<'a> {
 183     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 184         match *self {
 185             SegmentParam::LifeTime(lt) => lt.rewrite(context, shape),
 186             SegmentParam::Type(ty) => ty.rewrite(context, shape),
 187             SegmentParam::Binding(binding) => {
 188                 let mut result = match context.config.type_punctuation_density() {
 189                     TypeDensity::Wide => format!("{} = ", rewrite_ident(context, binding.ident)),
 190                     TypeDensity::Compressed => {
 191                         format!("{}=", rewrite_ident(context, binding.ident))
 192                     }
 193                 };
 194                 let budget = shape.width.checked_sub(result.len())?;
 195                 let rewrite = binding
 196                     .ty
 197                     .rewrite(context, Shape::legacy(budget, shape.indent + result.len()))?;
 198                 result.push_str(&rewrite);
 199                 Some(result)
 200             }
 201         }
 202     }
 203 }
 204
 205 // Formats a path segment. There are some hacks involved to correctly determine
 206 // the segment's associated span since it's not part of the AST.
 207 //
 208 // The span_lo is assumed to be greater than the end of any previous segment's
 209 // parameters and lesser or equal than the start of current segment.
 210 //
 211 // span_hi is assumed equal to the end of the entire path.
 212 //
 213 // When the segment contains a positive number of parameters, we update span_lo
 214 // so that invariants described above will hold for the next segment.
 215 fn rewrite_segment(
 216     path_context: PathContext,
 217     segment: &ast::PathSegment,
 218     span_lo: &mut BytePos,
 219     span_hi: BytePos,
 220     context: &RewriteContext,
 221     shape: Shape,
 222 ) -> Option<String> {
 223     let mut result = String::with_capacity(128);
 224     result.push_str(rewrite_ident(context, segment.ident));
 225
 226     let ident_len = result.len();
 227     let shape = if context.use_block_indent() {
 228         shape.offset_left(ident_len)?
 229     } else {
 230         shape.shrink_left(ident_len)?
 231     };
 232
 233     if let Some(ref args) = segment.args {
 234         match **args {
 235             ast::GenericArgs::AngleBracketed(ref data)
 236                 if !data.args.is_empty() || !data.bindings.is_empty() =>
 237             {
 238                 let param_list = data
 239                     .args
 240                     .iter()
 241                     .map(SegmentParam::from_generic_arg)
 242                     .chain(data.bindings.iter().map(|x| SegmentParam::Binding(&*x)))
 243                     .collect::<Vec<_>>();
 244
 245                 let separator = if path_context == PathContext::Expr {
 246                     "::"
 247                 } else {
 248                     ""
 249                 };
 250                 result.push_str(separator);
 251
 252                 let generics_str = overflow::rewrite_with_angle_brackets(
 253                     context,
 254                     "",
 255                     &param_list.iter().map(|e| &*e).collect::<Vec<_>>(),
 256                     shape,
 257                     mk_sp(*span_lo, span_hi),
 258                 )?;
 259
 260                 // Update position of last bracket.
 261                 *span_lo = context
 262                     .snippet_provider
 263                     .span_after(mk_sp(*span_lo, span_hi), "<");
 264
 265                 result.push_str(&generics_str)
 266             }
 267             ast::GenericArgs::Parenthesized(ref data) => {
 268                 let output = match data.output {
 269                     Some(ref ty) => FunctionRetTy::Ty(ty.clone()),
 270                     None => FunctionRetTy::Default(codemap::DUMMY_SP),
 271                 };
 272                 result.push_str(&format_function_type(
 273                     data.inputs.iter().map(|x| &**x),
 274                     &output,
 275                     false,
 276                     data.span,
 277                     context,
 278                     shape,
 279                 )?);
 280             }
 281             _ => (),
 282         }
 283     }
 284
 285     Some(result)
 286 }
 287
 288 fn format_function_type<'a, I>(
 289     inputs: I,
 290     output: &FunctionRetTy,
 291     variadic: bool,
 292     span: Span,
 293     context: &RewriteContext,
 294     shape: Shape,
 295 ) -> Option<String>
 296 where
 297     I: ExactSizeIterator,
 298     <I as Iterator>::Item: Deref,
 299     <I::Item as Deref>::Target: Rewrite + Spanned + 'a,
 300 {
 301     // Code for handling variadics is somewhat duplicated for items, but they
 302     // are different enough to need some serious refactoring to share code.
 303     enum ArgumentKind<T>
 304     where
 305         T: Deref,
 306         <T as Deref>::Target: Rewrite + Spanned,
 307     {
 308         Regular(T),
 309         Variadic(BytePos),
 310     }
 311
 312     let variadic_arg = if variadic {
 313         let variadic_start = context.snippet_provider.span_before(span, "...");
 314         Some(ArgumentKind::Variadic(variadic_start))
 315     } else {
 316         None
 317     };
 318
 319     // 2 for ()
 320     let budget = shape.width.checked_sub(2)?;
 321     // 1 for (
 322     let offset = match context.config.indent_style() {
 323         IndentStyle::Block => {
 324             shape
 325                 .block()
 326                 .block_indent(context.config.tab_spaces())
 327                 .indent
 328         }
 329         IndentStyle::Visual => shape.indent + 1,
 330     };
 331     let list_shape = Shape::legacy(budget, offset);
 332     let list_lo = context.snippet_provider.span_after(span, "(");
 333     let items = itemize_list(
 334         context.snippet_provider,
 335         inputs.map(ArgumentKind::Regular).chain(variadic_arg),
 336         ")",
 337         ",",
 338         |arg| match *arg {
 339             ArgumentKind::Regular(ref ty) => ty.span().lo(),
 340             ArgumentKind::Variadic(start) => start,
 341         },
 342         |arg| match *arg {
 343             ArgumentKind::Regular(ref ty) => ty.span().hi(),
 344             ArgumentKind::Variadic(start) => start + BytePos(3),
 345         },
 346         |arg| match *arg {
 347             ArgumentKind::Regular(ref ty) => ty.rewrite(context, list_shape),
 348             ArgumentKind::Variadic(_) => Some("...".to_owned()),
 349         },
 350         list_lo,
 351         span.hi(),
 352         false,
 353     );
 354
 355     let item_vec: Vec<_> = items.collect();
 356
 357     let tactic = definitive_tactic(
 358         &*item_vec,
 359         ListTactic::HorizontalVertical,
 360         Separator::Comma,
 361         budget,
 362     );
 363     let trailing_separator = if !context.use_block_indent() || variadic {
 364         SeparatorTactic::Never
 365     } else {
 366         context.config.trailing_comma()
 367     };
 368
 369     let fmt = ListFormatting::new(list_shape, context.config)
 370         .tactic(tactic)
 371         .trailing_separator(trailing_separator)
 372         .ends_with_newline(tactic.ends_with_newline(context.config.indent_style()))
 373         .preserve_newline(true);
 374     let list_str = write_list(&item_vec, &fmt)?;
 375
 376     let ty_shape = match context.config.indent_style() {
 377         // 4 = " -> "
 378         IndentStyle::Block => shape.offset_left(4)?,
 379         IndentStyle::Visual => shape.block_left(4)?,
 380     };
 381     let output = match *output {
 382         FunctionRetTy::Ty(ref ty) => {
 383             let type_str = ty.rewrite(context, ty_shape)?;
 384             format!(" -> {}", type_str)
 385         }
 386         FunctionRetTy::Default(..) => String::new(),
 387     };
 388
 389     let args = if (!list_str.contains('\n') || list_str.is_empty()) && !output.contains('\n')
 390         || !context.use_block_indent()
 391     {
 392         format!("({})", list_str)
 393     } else {
 394         format!(
 395             "({}{}{})",
 396             offset.to_string_with_newline(context.config),
 397             list_str,
 398             shape.block().indent.to_string_with_newline(context.config),
 399         )
 400     };
 401     if last_line_width(&args) + first_line_width(&output) <= shape.width {
 402         Some(format!("{}{}", args, output))
 403     } else {
 404         Some(format!(
 405             "{}\n{}{}",
 406             args,
 407             offset.to_string(context.config),
 408             output.trim_left()
 409         ))
 410     }
 411 }
 412
 413 fn type_bound_colon(context: &RewriteContext) -> &'static str {
 414     colon_spaces(
 415         context.config.space_before_colon(),
 416         context.config.space_after_colon(),
 417     )
 418 }
 419
 420 impl Rewrite for ast::WherePredicate {
 421     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 422         // FIXME: dead spans?
 423         let result = match *self {
 424             ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
 425                 ref bound_generic_params,
 426                 ref bounded_ty,
 427                 ref bounds,
 428                 ..
 429             }) => {
 430                 let type_str = bounded_ty.rewrite(context, shape)?;
 431                 let colon = type_bound_colon(context).trim_right();
 432                 let lhs = if let Some(lifetime_str) =
 433                     rewrite_lifetime_param(context, shape, bound_generic_params)
 434                 {
 435                     format!("for<{}> {}{}", lifetime_str, type_str, colon)
 436                 } else {
 437                     format!("{}{}", type_str, colon)
 438                 };
 439
 440                 rewrite_assign_rhs(context, lhs, bounds, shape)?
 441             }
 442             ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate {
 443                 ref lifetime,
 444                 ref bounds,
 445                 ..
 446             }) => rewrite_bounded_lifetime(lifetime, bounds, context, shape)?,
 447             ast::WherePredicate::EqPredicate(ast::WhereEqPredicate {
 448                 ref lhs_ty,
 449                 ref rhs_ty,
 450                 ..
 451             }) => {
 452                 let lhs_ty_str = lhs_ty.rewrite(context, shape).map(|lhs| lhs + " =")?;
 453                 rewrite_assign_rhs(context, lhs_ty_str, &**rhs_ty, shape)?
 454             }
 455         };
 456
 457         Some(result)
 458     }
 459 }
 460
 461 impl Rewrite for ast::GenericArg {
 462     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 463         match *self {
 464             ast::GenericArg::Lifetime(ref lt) => lt.rewrite(context, shape),
 465             ast::GenericArg::Type(ref ty) => ty.rewrite(context, shape),
 466         }
 467     }
 468 }
 469
 470 fn rewrite_bounded_lifetime(
 471     lt: &ast::Lifetime,
 472     bounds: &[ast::GenericBound],
 473     context: &RewriteContext,
 474     shape: Shape,
 475 ) -> Option<String> {
 476     let result = lt.rewrite(context, shape)?;
 477
 478     if bounds.is_empty() {
 479         Some(result)
 480     } else {
 481         let colon = type_bound_colon(context);
 482         let overhead = last_line_width(&result) + colon.len();
 483         let result = format!(
 484             "{}{}{}",
 485             result,
 486             colon,
 487             join_bounds(context, shape.sub_width(overhead)?, bounds, true)?
 488         );
 489         Some(result)
 490     }
 491 }
 492
 493 impl Rewrite for ast::Lifetime {
 494     fn rewrite(&self, context: &RewriteContext, _: Shape) -> Option<String> {
 495         Some(rewrite_ident(context, self.ident).to_owned())
 496     }
 497 }
 498
 499 impl Rewrite for ast::GenericBound {
 500     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 501         match *self {
 502             ast::GenericBound::Trait(ref poly_trait_ref, trait_bound_modifier) => {
 503                 match trait_bound_modifier {
 504                     ast::TraitBoundModifier::None => poly_trait_ref.rewrite(context, shape),
 505                     ast::TraitBoundModifier::Maybe => {
 506                         let rw = poly_trait_ref.rewrite(context, shape.offset_left(1)?)?;
 507                         Some(format!("?{}", rw))
 508                     }
 509                 }
 510             }
 511             ast::GenericBound::Outlives(ref lifetime) => lifetime.rewrite(context, shape),
 512         }
 513     }
 514 }
 515
 516 impl Rewrite for ast::GenericBounds {
 517     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 518         if self.is_empty() {
 519             return Some(String::new());
 520         }
 521
 522         let span = mk_sp(self.get(0)?.span().lo(), self.last()?.span().hi());
 523         let has_paren = context.snippet(span).starts_with("(");
 524         let bounds_shape = if has_paren {
 525             shape.offset_left(1)?.sub_width(1)?
 526         } else {
 527             shape
 528         };
 529         join_bounds(context, bounds_shape, self, true).map(|s| {
 530             if has_paren {
 531                 format!("({})", s)
 532             } else {
 533                 s
 534             }
 535         })
 536     }
 537 }
 538
 539 impl Rewrite for ast::GenericParam {
 540     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 541         let mut result = String::with_capacity(128);
 542         // FIXME: If there are more than one attributes, this will force multiline.
 543         match self.attrs.rewrite(context, shape) {
 544             Some(ref rw) if !rw.is_empty() => result.push_str(&format!("{} ", rw)),
 545             _ => (),
 546         }
 547         result.push_str(rewrite_ident(context, self.ident));
 548         if !self.bounds.is_empty() {
 549             result.push_str(type_bound_colon(context));
 550             result.push_str(&self.bounds.rewrite(context, shape)?)
 551         }
 552         if let ast::GenericParamKind::Type {
 553             default: Some(ref def),
 554         } = self.kind
 555         {
 556             let eq_str = match context.config.type_punctuation_density() {
 557                 TypeDensity::Compressed => "=",
 558                 TypeDensity::Wide => " = ",
 559             };
 560             result.push_str(eq_str);
 561             let budget = shape.width.checked_sub(result.len())?;
 562             let rewrite =
 563                 def.rewrite(context, Shape::legacy(budget, shape.indent + result.len()))?;
 564             result.push_str(&rewrite);
 565         }
 566
 567         Some(result)
 568     }
 569 }
 570
 571 impl Rewrite for ast::PolyTraitRef {
 572     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 573         if let Some(lifetime_str) =
 574             rewrite_lifetime_param(context, shape, &self.bound_generic_params)
 575         {
 576             // 6 is "for<> ".len()
 577             let extra_offset = lifetime_str.len() + 6;
 578             let path_str = self
 579                 .trait_ref
 580                 .rewrite(context, shape.offset_left(extra_offset)?)?;
 581
 582             Some(format!("for<{}> {}", lifetime_str, path_str))
 583         } else {
 584             self.trait_ref.rewrite(context, shape)
 585         }
 586     }
 587 }
 588
 589 impl Rewrite for ast::TraitRef {
 590     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 591         rewrite_path(context, PathContext::Type, None, &self.path, shape)
 592     }
 593 }
 594
 595 impl Rewrite for ast::Ty {
 596     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 597         match self.node {
 598             ast::TyKind::TraitObject(ref bounds, tobj_syntax) => {
 599                 // we have to consider 'dyn' keyword is used or not!!!
 600                 let is_dyn = tobj_syntax == ast::TraitObjectSyntax::Dyn;
 601                 // 4 is length of 'dyn '
 602                 let shape = if is_dyn { shape.offset_left(4)? } else { shape };
 603                 let res = bounds.rewrite(context, shape)?;
 604                 if is_dyn {
 605                     Some(format!("dyn {}", res))
 606                 } else {
 607                     Some(res)
 608                 }
 609             }
 610             ast::TyKind::Ptr(ref mt) => {
 611                 let prefix = match mt.mutbl {
 612                     Mutability::Mutable => "*mut ",
 613                     Mutability::Immutable => "*const ",
 614                 };
 615
 616                 rewrite_unary_prefix(context, prefix, &*mt.ty, shape)
 617             }
 618             ast::TyKind::Rptr(ref lifetime, ref mt) => {
 619                 let mut_str = format_mutability(mt.mutbl);
 620                 let mut_len = mut_str.len();
 621                 Some(match *lifetime {
 622                     Some(ref lifetime) => {
 623                         let lt_budget = shape.width.checked_sub(2 + mut_len)?;
 624                         let lt_str = lifetime.rewrite(
 625                             context,
 626                             Shape::legacy(lt_budget, shape.indent + 2 + mut_len),
 627                         )?;
 628                         let lt_len = lt_str.len();
 629                         let budget = shape.width.checked_sub(2 + mut_len + lt_len)?;
 630                         format!(
 631                             "&{} {}{}",
 632                             lt_str,
 633                             mut_str,
 634                             mt.ty.rewrite(
 635                                 context,
 636                                 Shape::legacy(budget, shape.indent + 2 + mut_len + lt_len)
 637                             )?
 638                         )
 639                     }
 640                     None => {
 641                         let budget = shape.width.checked_sub(1 + mut_len)?;
 642                         format!(
 643                             "&{}{}",
 644                             mut_str,
 645                             mt.ty.rewrite(
 646                                 context,
 647                                 Shape::legacy(budget, shape.indent + 1 + mut_len)
 648                             )?
 649                         )
 650                     }
 651                 })
 652             }
 653             // FIXME: we drop any comments here, even though it's a silly place to put
 654             // comments.
 655             ast::TyKind::Paren(ref ty) => {
 656                 let budget = shape.width.checked_sub(2)?;
 657                 ty.rewrite(context, Shape::legacy(budget, shape.indent + 1))
 658                     .map(|ty_str| format!("({})", ty_str))
 659             }
 660             ast::TyKind::Slice(ref ty) => {
 661                 let budget = shape.width.checked_sub(4)?;
 662                 ty.rewrite(context, Shape::legacy(budget, shape.indent + 1))
 663                     .map(|ty_str| format!("[{}]", ty_str))
 664             }
 665             ast::TyKind::Tup(ref items) => rewrite_tuple(
 666                 context,
 667                 &::utils::ptr_vec_to_ref_vec(items),
 668                 self.span,
 669                 shape,
 670             ),
 671             ast::TyKind::Path(ref q_self, ref path) => {
 672                 rewrite_path(context, PathContext::Type, q_self.as_ref(), path, shape)
 673             }
 674             ast::TyKind::Array(ref ty, ref repeats) => rewrite_pair(
 675                 &**ty,
 676                 &*repeats.value,
 677                 PairParts::new("[", "; ", "]"),
 678                 context,
 679                 shape,
 680                 SeparatorPlace::Back,
 681             ),
 682             ast::TyKind::Infer => {
 683                 if shape.width >= 1 {
 684                     Some("_".to_owned())
 685                 } else {
 686                     None
 687                 }
 688             }
 689             ast::TyKind::BareFn(ref bare_fn) => rewrite_bare_fn(bare_fn, self.span, context, shape),
 690             ast::TyKind::Never => Some(String::from("!")),
 691             ast::TyKind::Mac(ref mac) => {
 692                 rewrite_macro(mac, None, context, shape, MacroPosition::Expression)
 693             }
 694             ast::TyKind::ImplicitSelf => Some(String::from("")),
 695             ast::TyKind::ImplTrait(_, ref it) => it
 696                 .rewrite(context, shape)
 697                 .map(|it_str| format!("impl {}", it_str)),
 698             ast::TyKind::Err | ast::TyKind::Typeof(..) => unreachable!(),
 699         }
 700     }
 701 }
 702
 703 fn rewrite_bare_fn(
 704     bare_fn: &ast::BareFnTy,
 705     span: Span,
 706     context: &RewriteContext,
 707     shape: Shape,
 708 ) -> Option<String> {
 709     let mut result = String::with_capacity(128);
 710
 711     if let Some(ref lifetime_str) = rewrite_lifetime_param(context, shape, &bare_fn.generic_params)
 712     {
 713         result.push_str("for<");
 714         // 6 = "for<> ".len(), 4 = "for<".
 715         // This doesn't work out so nicely for multiline situation with lots of
 716         // rightward drift. If that is a problem, we could use the list stuff.
 717         result.push_str(lifetime_str);
 718         result.push_str("> ");
 719     }
 720
 721     result.push_str(::utils::format_unsafety(bare_fn.unsafety));
 722
 723     result.push_str(&format_abi(
 724         bare_fn.abi,
 725         context.config.force_explicit_abi(),
 726         false,
 727     ));
 728
 729     result.push_str("fn");
 730
 731     let func_ty_shape = shape.offset_left(result.len())?;
 732
 733     let rewrite = format_function_type(
 734         bare_fn.decl.inputs.iter(),
 735         &bare_fn.decl.output,
 736         bare_fn.decl.variadic,
 737         span,
 738         context,
 739         func_ty_shape,
 740     )?;
 741
 742     result.push_str(&rewrite);
 743
 744     Some(result)
 745 }
 746
 747 fn is_generic_bounds_in_order(generic_bounds: &[ast::GenericBound]) -> bool {
 748     let is_trait = |b: &ast::GenericBound| match b {
 749         ast::GenericBound::Outlives(..) => false,
 750         ast::GenericBound::Trait(..) => true,
 751     };
 752     let is_lifetime = |b: &ast::GenericBound| !is_trait(b);
 753     let last_trait_index = generic_bounds.iter().rposition(is_trait);
 754     let first_lifetime_index = generic_bounds.iter().position(is_lifetime);
 755     match (last_trait_index, first_lifetime_index) {
 756         (Some(last_trait_index), Some(first_lifetime_index)) => {
 757             last_trait_index < first_lifetime_index
 758         }
 759         _ => true,
 760     }
 761 }
 762
 763 fn join_bounds(
 764     context: &RewriteContext,
 765     shape: Shape,
 766     items: &[ast::GenericBound],
 767     need_indent: bool,
 768 ) -> Option<String> {
 769     // Try to join types in a single line
 770     let joiner = match context.config.type_punctuation_density() {
 771         TypeDensity::Compressed => "+",
 772         TypeDensity::Wide => " + ",
 773     };
 774     let type_strs = items
 775         .iter()
 776         .map(|item| item.rewrite(context, shape))
 777         .collect::<Option<Vec<_>>>()?;
 778     let result = type_strs.join(joiner);
 779     if items.len() <= 1 || (!result.contains('\n') && result.len() <= shape.width) {
 780         return Some(result);
 781     }
 782
 783     // We need to use multiple lines.
 784     let (type_strs, offset) = if need_indent {
 785         // Rewrite with additional indentation.
 786         let nested_shape = shape.block_indent(context.config.tab_spaces());
 787         let type_strs = items
 788             .iter()
 789             .map(|item| item.rewrite(context, nested_shape))
 790             .collect::<Option<Vec<_>>>()?;
 791         (type_strs, nested_shape.indent)
 792     } else {
 793         (type_strs, shape.indent)
 794     };
 795
 796     let is_bound_extendable = |s: &str, b: &ast::GenericBound| match b {
 797         ast::GenericBound::Outlives(..) => true,
 798         ast::GenericBound::Trait(..) => last_line_extendable(s),
 799     };
 800     let mut result = String::with_capacity(128);
 801     result.push_str(&type_strs[0]);
 802     let mut can_be_put_on_the_same_line = is_bound_extendable(&result, &items[0]);
 803     let generic_bounds_in_order = is_generic_bounds_in_order(items);
 804     for (bound, bound_str) in items[1..].iter().zip(type_strs[1..].iter()) {
 805         if generic_bounds_in_order && can_be_put_on_the_same_line {
 806             result.push_str(joiner);
 807         } else {
 808             result.push_str(&offset.to_string_with_newline(context.config));
 809             result.push_str("+ ");
 810         }
 811         result.push_str(bound_str);
 812         can_be_put_on_the_same_line = is_bound_extendable(bound_str, bound);
 813     }
 814
 815     Some(result)
 816 }
 817
 818 pub fn can_be_overflowed_type(context: &RewriteContext, ty: &ast::Ty, len: usize) -> bool {
 819     match ty.node {
 820         ast::TyKind::Tup(..) => context.use_block_indent() && len == 1,
 821         ast::TyKind::Rptr(_, ref mutty) | ast::TyKind::Ptr(ref mutty) => {
 822             can_be_overflowed_type(context, &*mutty.ty, len)
 823         }
 824         _ => false,
 825     }
 826 }
 827
 828 /// Returns `None` if there is no `LifetimeDef` in the given generic parameters.
 829 fn rewrite_lifetime_param(
 830     context: &RewriteContext,
 831     shape: Shape,
 832     generic_params: &[ast::GenericParam],
 833 ) -> Option<String> {
 834     let result = generic_params
 835         .iter()
 836         .filter(|p| match p.kind {
 837             ast::GenericParamKind::Lifetime => true,
 838             _ => false,
 839         }).map(|lt| lt.rewrite(context, shape))
 840         .collect::<Option<Vec<_>>>()?
 841         .join(", ");
 842     if result.is_empty() {
 843         None
 844     } else {
 845         Some(result)
 846     }
 847 }