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