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::ops::Deref;
  12 use std::iter::ExactSizeIterator;
  13
  14 use syntax::ast::{self, Mutability, FunctionRetTy};
  15 use syntax::print::pprust;
  16 use syntax::codemap::{self, Span, BytePos};
  17 use syntax::abi;
  18
  19 use {Indent, Spanned};
  20 use codemap::SpanUtils;
  21 use lists::{format_item_list, itemize_list, format_fn_args};
  22 use rewrite::{Rewrite, RewriteContext};
  23 use utils::{extra_offset, format_mutability, wrap_str};
  24 use expr::{rewrite_unary_prefix, rewrite_pair, rewrite_tuple};
  25 use config::TypeDensity;
  26 use itertools::Itertools;
  27
  28 // Does not wrap on simple segments.
  29 pub fn rewrite_path(context: &RewriteContext,
  30                     expr_context: bool,
  31                     qself: Option<&ast::QSelf>,
  32                     path: &ast::Path,
  33                     width: usize,
  34                     offset: Indent)
  35                     -> Option<String> {
  36     let skip_count = qself.map_or(0, |x| x.position);
  37
  38     let mut result = if path.global && qself.is_none() {
  39         "::".to_owned()
  40     } else {
  41         String::new()
  42     };
  43
  44     let mut span_lo = path.span.lo;
  45
  46     if let Some(qself) = qself {
  47         result.push('<');
  48         if context.config.spaces_within_angle_brackets {
  49             result.push_str(" ")
  50         }
  51
  52         let fmt_ty = try_opt!(qself.ty.rewrite(context, width, offset));
  53         result.push_str(&fmt_ty);
  54
  55         if skip_count > 0 {
  56             result.push_str(" as ");
  57             if path.global {
  58                 result.push_str("::");
  59             }
  60
  61             let extra_offset = extra_offset(&result, offset);
  62             // 3 = ">::".len()
  63             let budget = try_opt!(width.checked_sub(extra_offset + 3));
  64
  65             result = try_opt!(rewrite_path_segments(false,
  66                                                     result,
  67                                                     path.segments.iter().take(skip_count),
  68                                                     span_lo,
  69                                                     path.span.hi,
  70                                                     context,
  71                                                     budget,
  72                                                     offset + extra_offset));
  73         }
  74
  75         if context.config.spaces_within_angle_brackets {
  76             result.push_str(" ")
  77         }
  78
  79         result.push_str(">::");
  80         span_lo = qself.ty.span.hi + BytePos(1);
  81     }
  82
  83     let extra_offset = extra_offset(&result, offset);
  84     let budget = try_opt!(width.checked_sub(extra_offset));
  85     rewrite_path_segments(expr_context,
  86                           result,
  87                           path.segments.iter().skip(skip_count),
  88                           span_lo,
  89                           path.span.hi,
  90                           context,
  91                           budget,
  92                           offset + extra_offset)
  93 }
  94
  95 fn rewrite_path_segments<'a, I>(expr_context: bool,
  96                                 mut buffer: String,
  97                                 iter: I,
  98                                 mut span_lo: BytePos,
  99                                 span_hi: BytePos,
 100                                 context: &RewriteContext,
 101                                 width: usize,
 102                                 offset: Indent)
 103                                 -> Option<String>
 104     where I: Iterator<Item = &'a ast::PathSegment>
 105 {
 106     let mut first = true;
 107
 108     for segment in iter {
 109         if first {
 110             first = false;
 111         } else {
 112             buffer.push_str("::");
 113         }
 114
 115         let extra_offset = extra_offset(&buffer, offset);
 116         let remaining_width = try_opt!(width.checked_sub(extra_offset));
 117         let new_offset = offset + extra_offset;
 118         let segment_string = try_opt!(rewrite_segment(expr_context,
 119                                                       segment,
 120                                                       &mut span_lo,
 121                                                       span_hi,
 122                                                       context,
 123                                                       remaining_width,
 124                                                       new_offset));
 125
 126         buffer.push_str(&segment_string);
 127     }
 128
 129     Some(buffer)
 130 }
 131
 132 #[derive(Debug)]
 133 enum SegmentParam<'a> {
 134     LifeTime(&'a ast::Lifetime),
 135     Type(&'a ast::Ty),
 136     Binding(&'a ast::TypeBinding),
 137 }
 138
 139 impl<'a> SegmentParam<'a> {
 140     fn get_span(&self) -> Span {
 141         match *self {
 142             SegmentParam::LifeTime(lt) => lt.span,
 143             SegmentParam::Type(ty) => ty.span,
 144             SegmentParam::Binding(binding) => binding.span,
 145         }
 146     }
 147 }
 148
 149 impl<'a> Rewrite for SegmentParam<'a> {
 150     fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option<String> {
 151         match *self {
 152             SegmentParam::LifeTime(lt) => lt.rewrite(context, width, offset),
 153             SegmentParam::Type(ty) => ty.rewrite(context, width, offset),
 154             SegmentParam::Binding(binding) => {
 155                 let mut result = format!("{} = ", binding.ident);
 156                 let budget = try_opt!(width.checked_sub(result.len()));
 157                 let rewrite = try_opt!(binding.ty.rewrite(context, budget, offset + result.len()));
 158                 result.push_str(&rewrite);
 159                 Some(result)
 160             }
 161         }
 162     }
 163 }
 164
 165 // Formats a path segment. There are some hacks involved to correctly determine
 166 // the segment's associated span since it's not part of the AST.
 167 //
 168 // The span_lo is assumed to be greater than the end of any previous segment's
 169 // parameters and lesser or equal than the start of current segment.
 170 //
 171 // span_hi is assumed equal to the end of the entire path.
 172 //
 173 // When the segment contains a positive number of parameters, we update span_lo
 174 // so that invariants described above will hold for the next segment.
 175 fn rewrite_segment(expr_context: bool,
 176                    segment: &ast::PathSegment,
 177                    span_lo: &mut BytePos,
 178                    span_hi: BytePos,
 179                    context: &RewriteContext,
 180                    width: usize,
 181                    offset: Indent)
 182                    -> Option<String> {
 183     let ident_len = segment.identifier.to_string().len();
 184     let width = try_opt!(width.checked_sub(ident_len));
 185     let offset = offset + ident_len;
 186
 187     let params = match segment.parameters {
 188         ast::PathParameters::AngleBracketed(ref data) if !data.lifetimes.is_empty() ||
 189                                                          !data.types.is_empty() ||
 190                                                          !data.bindings.is_empty() => {
 191             let param_list = data.lifetimes
 192                 .iter()
 193                 .map(SegmentParam::LifeTime)
 194                 .chain(data.types.iter().map(|x| SegmentParam::Type(&*x)))
 195                 .chain(data.bindings.iter().map(|x| SegmentParam::Binding(&*x)))
 196                 .collect::<Vec<_>>();
 197
 198             let next_span_lo = param_list.last().unwrap().get_span().hi + BytePos(1);
 199             let list_lo = context.codemap.span_after(codemap::mk_sp(*span_lo, span_hi), "<");
 200             let separator = if expr_context { "::" } else { "" };
 201
 202             // 1 for <
 203             let extra_offset = 1 + separator.len();
 204             // 1 for >
 205             let list_width = try_opt!(width.checked_sub(extra_offset + 1));
 206
 207             let items = itemize_list(context.codemap,
 208                                      param_list.into_iter(),
 209                                      ">",
 210                                      |param| param.get_span().lo,
 211                                      |param| param.get_span().hi,
 212                                      |seg| seg.rewrite(context, list_width, offset + extra_offset),
 213                                      list_lo,
 214                                      span_hi);
 215             let list_str = try_opt!(format_item_list(items,
 216                                                      list_width,
 217                                                      offset + extra_offset,
 218                                                      context.config));
 219
 220             // Update position of last bracket.
 221             *span_lo = next_span_lo;
 222
 223             if context.config.spaces_within_angle_brackets && list_str.len() > 0 {
 224                 format!("{}< {} >", separator, list_str)
 225             } else {
 226                 format!("{}<{}>", separator, list_str)
 227             }
 228         }
 229         ast::PathParameters::Parenthesized(ref data) => {
 230             let output = match data.output {
 231                 Some(ref ty) => FunctionRetTy::Ty(ty.clone()),
 232                 None => FunctionRetTy::Default(codemap::DUMMY_SP),
 233             };
 234             try_opt!(format_function_type(data.inputs.iter().map(|x| &**x),
 235                                           &output,
 236                                           false,
 237                                           data.span,
 238                                           context,
 239                                           width,
 240                                           offset))
 241         }
 242         _ => String::new(),
 243     };
 244
 245     Some(format!("{}{}", segment.identifier, params))
 246 }
 247
 248 fn format_function_type<'a, I>(inputs: I,
 249                                output: &FunctionRetTy,
 250                                variadic: bool,
 251                                span: Span,
 252                                context: &RewriteContext,
 253                                width: usize,
 254                                offset: Indent)
 255                                -> Option<String>
 256     where I: ExactSizeIterator,
 257           <I as Iterator>::Item: Deref,
 258           <I::Item as Deref>::Target: Rewrite + Spanned + 'a
 259 {
 260     // Code for handling variadics is somewhat duplicated for items, but they
 261     // are different enough to need some serious refactoring to share code.
 262     enum ArgumentKind<T>
 263         where T: Deref,
 264               <T as Deref>::Target: Rewrite + Spanned
 265     {
 266         Regular(Box<T>),
 267         Variadic(BytePos),
 268     }
 269
 270     let variadic_arg = if variadic {
 271         let variadic_start = context.codemap.span_before(span, "...");
 272         Some(ArgumentKind::Variadic(variadic_start))
 273     } else {
 274         None
 275     };
 276
 277     // 2 for ()
 278     let budget = try_opt!(width.checked_sub(2));
 279     // 1 for (
 280     let offset = offset + 1;
 281     let list_lo = context.codemap.span_after(span, "(");
 282     let items = itemize_list(context.codemap,
 283                              // FIXME Would be nice to avoid this allocation,
 284                              // but I couldn't get the types to work out.
 285                              inputs.map(|i| ArgumentKind::Regular(Box::new(i)))
 286                                  .chain(variadic_arg),
 287                              ")",
 288                              |arg| {
 289                                  match *arg {
 290                                      ArgumentKind::Regular(ref ty) => ty.span().lo,
 291                                      ArgumentKind::Variadic(start) => start,
 292                                  }
 293                              },
 294                              |arg| {
 295                                  match *arg {
 296                                      ArgumentKind::Regular(ref ty) => ty.span().hi,
 297                                      ArgumentKind::Variadic(start) => start + BytePos(3),
 298                                  }
 299                              },
 300                              |arg| {
 301         match *arg {
 302             ArgumentKind::Regular(ref ty) => ty.rewrite(context, budget, offset),
 303             ArgumentKind::Variadic(_) => Some("...".to_owned()),
 304         }
 305     },
 306                              list_lo,
 307                              span.hi);
 308
 309     let list_str = try_opt!(format_fn_args(items, budget, offset, context.config));
 310
 311     let output = match *output {
 312         FunctionRetTy::Ty(ref ty) => {
 313             let budget = try_opt!(width.checked_sub(4));
 314             let type_str = try_opt!(ty.rewrite(context, budget, offset + 4));
 315             format!(" -> {}", type_str)
 316         }
 317         FunctionRetTy::Default(..) => String::new(),
 318     };
 319
 320     let infix = if !output.is_empty() && output.len() + list_str.len() > width {
 321         format!("\n{}", (offset - 1).to_string(context.config))
 322     } else {
 323         String::new()
 324     };
 325
 326     Some(if context.config.spaces_within_parens {
 327         format!("( {} ){}{}", list_str, infix, output)
 328     } else {
 329         format!("({}){}{}", list_str, infix, output)
 330     })
 331 }
 332
 333 impl Rewrite for ast::WherePredicate {
 334     fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option<String> {
 335         // TODO: dead spans?
 336         let result = match *self {
 337             ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate { ref bound_lifetimes,
 338                                                                            ref bounded_ty,
 339                                                                            ref bounds,
 340                                                                            .. }) => {
 341                 let type_str = try_opt!(bounded_ty.rewrite(context, width, offset));
 342
 343                 if !bound_lifetimes.is_empty() {
 344                     let lifetime_str: String = try_opt!(bound_lifetimes.iter()
 345                                                                .map(|lt| {
 346                                                                    lt.rewrite(context,
 347                                                                               width,
 348                                                                               offset)
 349                                                                })
 350                                                                .intersperse(Some(", ".to_string()))
 351                                                                .collect());
 352
 353                     // 8 = "for<> : ".len()
 354                     let used_width = lifetime_str.len() + type_str.len() + 8;
 355                     let budget = try_opt!(width.checked_sub(used_width));
 356                     let bounds_str: String = try_opt!(bounds.iter()
 357                                                     .map(|ty_bound| {
 358                                                         ty_bound.rewrite(context,
 359                                                                          budget,
 360                                                                          offset + used_width)
 361                                                     })
 362                                                     .intersperse(Some(" + ".to_string()))
 363                                                     .collect());
 364
 365                     if context.config.spaces_within_angle_brackets && lifetime_str.len() > 0 {
 366                         format!("for< {} > {}: {}", lifetime_str, type_str, bounds_str)
 367                     } else {
 368                         format!("for<{}> {}: {}", lifetime_str, type_str, bounds_str)
 369                     }
 370                 } else {
 371                     // 2 = ": ".len()
 372                     let used_width = type_str.len() + 2;
 373                     let budget = try_opt!(width.checked_sub(used_width));
 374                     let bounds_str: String = try_opt!(bounds.iter()
 375                                                     .map(|ty_bound| {
 376                                                         ty_bound.rewrite(context,
 377                                                                          budget,
 378                                                                          offset + used_width)
 379                                                     })
 380                                                     .intersperse(Some(" + ".to_string()))
 381                                                     .collect());
 382
 383                     format!("{}: {}", type_str, bounds_str)
 384                 }
 385             }
 386             ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate { ref lifetime,
 387                                                                              ref bounds,
 388                                                                              .. }) => {
 389                 try_opt!(rewrite_bounded_lifetime(lifetime, bounds.iter(), context, width, offset))
 390             }
 391             ast::WherePredicate::EqPredicate(ast::WhereEqPredicate { ref path, ref ty, .. }) => {
 392                 let ty_str = try_opt!(ty.rewrite(context, width, offset));
 393                 // 3 = " = ".len()
 394                 let used_width = 3 + ty_str.len();
 395                 let budget = try_opt!(width.checked_sub(used_width));
 396                 let path_str =
 397                     try_opt!(rewrite_path(context, false, None, path, budget, offset + used_width));
 398                 format!("{} = {}", path_str, ty_str)
 399             }
 400         };
 401
 402         wrap_str(result, context.config.max_width, width, offset)
 403     }
 404 }
 405
 406 impl Rewrite for ast::LifetimeDef {
 407     fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option<String> {
 408         rewrite_bounded_lifetime(&self.lifetime, self.bounds.iter(), context, width, offset)
 409     }
 410 }
 411
 412 fn rewrite_bounded_lifetime<'b, I>(lt: &ast::Lifetime,
 413                                    bounds: I,
 414                                    context: &RewriteContext,
 415                                    width: usize,
 416                                    offset: Indent)
 417                                    -> Option<String>
 418     where I: ExactSizeIterator<Item = &'b ast::Lifetime>
 419 {
 420     let result = try_opt!(lt.rewrite(context, width, offset));
 421
 422     if bounds.len() == 0 {
 423         Some(result)
 424     } else {
 425         let appendix: Vec<_> = try_opt!(bounds.into_iter()
 426             .map(|b| b.rewrite(context, width, offset))
 427             .collect());
 428         let bound_spacing_before = if context.config.space_before_bound {
 429             " "
 430         } else {
 431             ""
 432         };
 433         let bound_spacing_after = if context.config.space_after_bound_colon {
 434             " "
 435         } else {
 436             ""
 437         };
 438         let result = format!("{}{}:{}{}",
 439                              result,
 440                              bound_spacing_before,
 441                              bound_spacing_after,
 442                              appendix.join(" + "));
 443         wrap_str(result, context.config.max_width, width, offset)
 444     }
 445 }
 446
 447 impl Rewrite for ast::TyParamBound {
 448     fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option<String> {
 449         match *self {
 450             ast::TyParamBound::TraitTyParamBound(ref tref, ast::TraitBoundModifier::None) => {
 451                 tref.rewrite(context, width, offset)
 452             }
 453             ast::TyParamBound::TraitTyParamBound(ref tref, ast::TraitBoundModifier::Maybe) => {
 454                 let budget = try_opt!(width.checked_sub(1));
 455                 Some(format!("?{}", try_opt!(tref.rewrite(context, budget, offset + 1))))
 456             }
 457             ast::TyParamBound::RegionTyParamBound(ref l) => l.rewrite(context, width, offset),
 458         }
 459     }
 460 }
 461
 462 impl Rewrite for ast::Lifetime {
 463     fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option<String> {
 464         wrap_str(pprust::lifetime_to_string(self),
 465                  context.config.max_width,
 466                  width,
 467                  offset)
 468     }
 469 }
 470
 471 impl Rewrite for ast::TyParamBounds {
 472     fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option<String> {
 473         let strs: Vec<_> = try_opt!(self.iter()
 474             .map(|b| b.rewrite(context, width, offset))
 475             .collect());
 476         wrap_str(strs.join(" + "), context.config.max_width, width, offset)
 477     }
 478 }
 479
 480 impl Rewrite for ast::TyParam {
 481     fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option<String> {
 482         let mut result = String::with_capacity(128);
 483         result.push_str(&self.ident.to_string());
 484         if !self.bounds.is_empty() {
 485             if context.config.space_before_bound {
 486                 result.push_str(" ");
 487             }
 488             result.push_str(":");
 489             if context.config.space_after_bound_colon {
 490                 result.push_str(" ");
 491             }
 492
 493             let bounds: String = try_opt!(self.bounds
 494                 .iter()
 495                 .map(|ty_bound| ty_bound.rewrite(context, width, offset))
 496                 .intersperse(Some(" + ".to_string()))
 497                 .collect());
 498
 499             result.push_str(&bounds);
 500         }
 501         if let Some(ref def) = self.default {
 502
 503             let eq_str = match context.config.type_punctuation_density {
 504                 TypeDensity::Compressed => "=",
 505                 TypeDensity::Wide => " = ",
 506             };
 507             result.push_str(eq_str);
 508             let budget = try_opt!(width.checked_sub(result.len()));
 509             let rewrite = try_opt!(def.rewrite(context, budget, offset + result.len()));
 510             result.push_str(&rewrite);
 511         }
 512
 513         wrap_str(result, context.config.max_width, width, offset)
 514     }
 515 }
 516
 517 impl Rewrite for ast::PolyTraitRef {
 518     fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option<String> {
 519         if !self.bound_lifetimes.is_empty() {
 520             let lifetime_str: String = try_opt!(self.bound_lifetimes
 521                 .iter()
 522                 .map(|lt| lt.rewrite(context, width, offset))
 523                 .intersperse(Some(", ".to_string()))
 524                 .collect());
 525
 526             // 6 is "for<> ".len()
 527             let extra_offset = lifetime_str.len() + 6;
 528             let max_path_width = try_opt!(width.checked_sub(extra_offset));
 529             let path_str = try_opt!(self.trait_ref
 530                 .rewrite(context, max_path_width, offset + extra_offset));
 531
 532             Some(if context.config.spaces_within_angle_brackets && lifetime_str.len() > 0 {
 533                 format!("for< {} > {}", lifetime_str, path_str)
 534             } else {
 535                 format!("for<{}> {}", lifetime_str, path_str)
 536             })
 537         } else {
 538             self.trait_ref.rewrite(context, width, offset)
 539         }
 540     }
 541 }
 542
 543 impl Rewrite for ast::TraitRef {
 544     fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option<String> {
 545         rewrite_path(context, false, None, &self.path, width, offset)
 546     }
 547 }
 548
 549 impl Rewrite for ast::Ty {
 550     fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option<String> {
 551         match self.node {
 552             ast::TyKind::ObjectSum(ref ty, ref bounds) => {
 553                 let ty_str = try_opt!(ty.rewrite(context, width, offset));
 554                 let overhead = ty_str.len() + 3;
 555                 let plus_str = match context.config.type_punctuation_density {
 556                     TypeDensity::Compressed => "+",
 557                     TypeDensity::Wide => " + ",
 558                 };
 559                 Some(format!("{}{}{}",
 560                              ty_str,
 561                              plus_str,
 562                              try_opt!(bounds.rewrite(context,
 563                                                      try_opt!(width.checked_sub(overhead)),
 564                                                      offset + overhead))))
 565             }
 566             ast::TyKind::Ptr(ref mt) => {
 567                 let prefix = match mt.mutbl {
 568                     Mutability::Mutable => "*mut ",
 569                     Mutability::Immutable => "*const ",
 570                 };
 571
 572                 rewrite_unary_prefix(context, prefix, &*mt.ty, width, offset)
 573             }
 574             ast::TyKind::Rptr(ref lifetime, ref mt) => {
 575                 let mut_str = format_mutability(mt.mutbl);
 576                 let mut_len = mut_str.len();
 577                 Some(match *lifetime {
 578                     Some(ref lifetime) => {
 579                         let lt_budget = try_opt!(width.checked_sub(2 + mut_len));
 580                         let lt_str =
 581                             try_opt!(lifetime.rewrite(context, lt_budget, offset + 2 + mut_len));
 582                         let lt_len = lt_str.len();
 583                         let budget = try_opt!(width.checked_sub(2 + mut_len + lt_len));
 584                         format!("&{} {}{}",
 585                                 lt_str,
 586                                 mut_str,
 587                                 try_opt!(mt.ty
 588                                     .rewrite(context, budget, offset + 2 + mut_len + lt_len)))
 589                     }
 590                     None => {
 591                         let budget = try_opt!(width.checked_sub(1 + mut_len));
 592                         format!("&{}{}",
 593                                 mut_str,
 594                                 try_opt!(mt.ty.rewrite(context, budget, offset + 1 + mut_len)))
 595                     }
 596                 })
 597             }
 598             // FIXME: we drop any comments here, even though it's a silly place to put
 599             // comments.
 600             ast::TyKind::Paren(ref ty) => {
 601                 let budget = try_opt!(width.checked_sub(2));
 602                 ty.rewrite(context, budget, offset + 1)
 603                     .map(|ty_str| if context.config.spaces_within_parens {
 604                         format!("( {} )", ty_str)
 605                     } else {
 606                         format!("({})", ty_str)
 607                     })
 608             }
 609             ast::TyKind::Vec(ref ty) => {
 610                 let budget = try_opt!(width.checked_sub(2));
 611                 ty.rewrite(context, budget, offset + 1).map(|ty_str| format!("[{}]", ty_str))
 612             }
 613             ast::TyKind::Tup(ref items) => {
 614                 rewrite_tuple(context,
 615                               items.iter().map(|x| &**x),
 616                               self.span,
 617                               width,
 618                               offset)
 619             }
 620             ast::TyKind::PolyTraitRef(ref trait_ref) => trait_ref.rewrite(context, width, offset),
 621             ast::TyKind::Path(ref q_self, ref path) => {
 622                 rewrite_path(context, false, q_self.as_ref(), path, width, offset)
 623             }
 624             ast::TyKind::FixedLengthVec(ref ty, ref repeats) => {
 625                 rewrite_pair(&**ty, &**repeats, "[", "; ", "]", context, width, offset)
 626             }
 627             ast::TyKind::Infer => {
 628                 if width >= 1 {
 629                     Some("_".to_owned())
 630                 } else {
 631                     None
 632                 }
 633             }
 634             ast::TyKind::BareFn(ref bare_fn) => {
 635                 rewrite_bare_fn(bare_fn, self.span, context, width, offset)
 636             }
 637             ast::TyKind::Never => Some(String::from("!")),
 638             ast::TyKind::Mac(..) |
 639             ast::TyKind::Typeof(..) => unreachable!(),
 640             ast::TyKind::ImplicitSelf => Some(String::from("")),
 641             ast::TyKind::ImplTrait(ref it) => {
 642                 it.rewrite(context, width, offset).map(|it_str| format!("impl {}", it_str))
 643             }
 644         }
 645     }
 646 }
 647
 648 fn rewrite_bare_fn(bare_fn: &ast::BareFnTy,
 649                    span: Span,
 650                    context: &RewriteContext,
 651                    width: usize,
 652                    offset: Indent)
 653                    -> Option<String> {
 654     let mut result = String::with_capacity(128);
 655
 656     if !bare_fn.lifetimes.is_empty() {
 657         result.push_str("for<");
 658         // 6 = "for<> ".len(), 4 = "for<".
 659         // This doesn't work out so nicely for mutliline situation with lots of
 660         // rightward drift. If that is a problem, we could use the list stuff.
 661         result.push_str(&try_opt!(bare_fn.lifetimes
 662             .iter()
 663             .map(|l| l.rewrite(context, try_opt!(width.checked_sub(6)), offset + 4))
 664             .intersperse(Some(", ".to_string()))
 665             .collect::<Option<String>>()));
 666         result.push_str("> ");
 667     }
 668
 669     result.push_str(::utils::format_unsafety(bare_fn.unsafety));
 670
 671     if bare_fn.abi != abi::Abi::Rust {
 672         result.push_str(&::utils::format_abi(bare_fn.abi, context.config.force_explicit_abi));
 673     }
 674
 675     result.push_str("fn");
 676
 677     let budget = try_opt!(width.checked_sub(result.len()));
 678     let indent = offset + result.len();
 679
 680     let rewrite = try_opt!(format_function_type(bare_fn.decl.inputs.iter(),
 681                                                 &bare_fn.decl.output,
 682                                                 bare_fn.decl.variadic,
 683                                                 span,
 684                                                 context,
 685                                                 budget,
 686                                                 indent));
 687
 688     result.push_str(&rewrite);
 689
 690     Some(result)
 691 }