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