src/types.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use std::iter::ExactSizeIterator;
  12 use std::ops::Deref;
  13
  14 use config::lists::*;
  15 use syntax::ast::{self, FunctionRetTy, Mutability};
  16 use syntax::codemap::{self, BytePos, Span};
  17 use syntax::symbol::keywords;
  18
  19 use codemap::SpanUtils;
  20 use config::{IndentStyle, TypeDensity};
  21 use expr::{rewrite_pair, rewrite_tuple, rewrite_unary_prefix, wrap_args_with_parens, PairParts};
  22 use items::{format_generics_item_list, generics_shape_from_config};
  23 use lists::{definitive_tactic, itemize_list, write_list, ListFormatting, Separator};
  24 use macros::{rewrite_macro, MacroPosition};
  25 use rewrite::{Rewrite, RewriteContext};
  26 use shape::Shape;
  27 use spanned::Spanned;
  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 mut result = String::with_capacity(128);
 204     result.push_str(&segment.identifier.name.as_str());
 205
 206     let ident_len = result.len();
 207     let shape = shape.shrink_left(ident_len)?;
 208
 209     if let Some(ref params) = segment.parameters {
 210         match **params {
 211             ast::PathParameters::AngleBracketed(ref data)
 212                 if !data.lifetimes.is_empty() || !data.types.is_empty()
 213                     || !data.bindings.is_empty() =>
 214             {
 215                 let param_list = data.lifetimes
 216                     .iter()
 217                     .map(SegmentParam::LifeTime)
 218                     .chain(data.types.iter().map(|x| SegmentParam::Type(&*x)))
 219                     .chain(data.bindings.iter().map(|x| SegmentParam::Binding(&*x)))
 220                     .collect::<Vec<_>>();
 221
 222                 let next_span_lo = param_list.last().unwrap().get_span().hi() + BytePos(1);
 223                 let list_lo = context
 224                     .snippet_provider
 225                     .span_after(mk_sp(*span_lo, span_hi), "<");
 226                 let separator = if path_context == PathContext::Expr {
 227                     "::"
 228                 } else {
 229                     ""
 230                 };
 231                 result.push_str(separator);
 232
 233                 let generics_shape =
 234                     generics_shape_from_config(context.config, shape, separator.len())?;
 235                 let one_line_width = shape.width.checked_sub(separator.len() + 2)?;
 236                 let items = itemize_list(
 237                     context.snippet_provider,
 238                     param_list.into_iter(),
 239                     ">",
 240                     ",",
 241                     |param| param.get_span().lo(),
 242                     |param| param.get_span().hi(),
 243                     |seg| seg.rewrite(context, generics_shape),
 244                     list_lo,
 245                     span_hi,
 246                     false,
 247                 );
 248                 let generics_str =
 249                     format_generics_item_list(context, items, generics_shape, one_line_width)?;
 250
 251                 // Update position of last bracket.
 252                 *span_lo = next_span_lo;
 253
 254                 result.push_str(&generics_str)
 255             }
 256             ast::PathParameters::Parenthesized(ref data) => {
 257                 let output = match data.output {
 258                     Some(ref ty) => FunctionRetTy::Ty(ty.clone()),
 259                     None => FunctionRetTy::Default(codemap::DUMMY_SP),
 260                 };
 261                 result.push_str(&format_function_type(
 262                     data.inputs.iter().map(|x| &**x),
 263                     &output,
 264                     false,
 265                     data.span,
 266                     context,
 267                     shape,
 268                 )?);
 269             }
 270             _ => (),
 271         }
 272     }
 273
 274     Some(result)
 275 }
 276
 277 fn format_function_type<'a, I>(
 278     inputs: I,
 279     output: &FunctionRetTy,
 280     variadic: bool,
 281     span: Span,
 282     context: &RewriteContext,
 283     shape: Shape,
 284 ) -> Option<String>
 285 where
 286     I: ExactSizeIterator,
 287     <I as Iterator>::Item: Deref,
 288     <I::Item as Deref>::Target: Rewrite + Spanned + 'a,
 289 {
 290     // Code for handling variadics is somewhat duplicated for items, but they
 291     // are different enough to need some serious refactoring to share code.
 292     enum ArgumentKind<T>
 293     where
 294         T: Deref,
 295         <T as Deref>::Target: Rewrite + Spanned,
 296     {
 297         Regular(Box<T>),
 298         Variadic(BytePos),
 299     }
 300
 301     let variadic_arg = if variadic {
 302         let variadic_start = context.snippet_provider.span_before(span, "...");
 303         Some(ArgumentKind::Variadic(variadic_start))
 304     } else {
 305         None
 306     };
 307
 308     // 2 for ()
 309     let budget = shape.width.checked_sub(2)?;
 310     // 1 for (
 311     let offset = match context.config.indent_style() {
 312         IndentStyle::Block => {
 313             shape
 314                 .block()
 315                 .block_indent(context.config.tab_spaces())
 316                 .indent
 317         }
 318         IndentStyle::Visual => shape.indent + 1,
 319     };
 320     let list_shape = Shape::legacy(budget, offset);
 321     let list_lo = context.snippet_provider.span_after(span, "(");
 322     let items = itemize_list(
 323         context.snippet_provider,
 324         // FIXME Would be nice to avoid this allocation,
 325         // but I couldn't get the types to work out.
 326         inputs
 327             .map(|i| ArgumentKind::Regular(Box::new(i)))
 328             .chain(variadic_arg),
 329         ")",
 330         ",",
 331         |arg| match *arg {
 332             ArgumentKind::Regular(ref ty) => ty.span().lo(),
 333             ArgumentKind::Variadic(start) => start,
 334         },
 335         |arg| match *arg {
 336             ArgumentKind::Regular(ref ty) => ty.span().hi(),
 337             ArgumentKind::Variadic(start) => start + BytePos(3),
 338         },
 339         |arg| match *arg {
 340             ArgumentKind::Regular(ref ty) => ty.rewrite(context, list_shape),
 341             ArgumentKind::Variadic(_) => Some("...".to_owned()),
 342         },
 343         list_lo,
 344         span.hi(),
 345         false,
 346     );
 347
 348     let item_vec: Vec<_> = items.collect();
 349
 350     let tactic = definitive_tactic(
 351         &*item_vec,
 352         ListTactic::HorizontalVertical,
 353         Separator::Comma,
 354         budget,
 355     );
 356
 357     let fmt = ListFormatting {
 358         tactic,
 359         separator: ",",
 360         trailing_separator: if !context.use_block_indent() || variadic {
 361             SeparatorTactic::Never
 362         } else {
 363             context.config.trailing_comma()
 364         },
 365         separator_place: SeparatorPlace::Back,
 366         shape: list_shape,
 367         ends_with_newline: tactic.ends_with_newline(context.config.indent_style()),
 368         preserve_newline: true,
 369         config: context.config,
 370     };
 371
 372     let list_str = write_list(&item_vec, &fmt)?;
 373
 374     let ty_shape = match context.config.indent_style() {
 375         // 4 = " -> "
 376         IndentStyle::Block => shape.offset_left(4)?,
 377         IndentStyle::Visual => shape.block_left(4)?,
 378     };
 379     let output = match *output {
 380         FunctionRetTy::Ty(ref ty) => {
 381             let type_str = ty.rewrite(context, ty_shape)?;
 382             format!(" -> {}", type_str)
 383         }
 384         FunctionRetTy::Default(..) => String::new(),
 385     };
 386
 387     let extendable = (!list_str.contains('\n') || list_str.is_empty()) && !output.contains('\n');
 388     let args = wrap_args_with_parens(
 389         context,
 390         &list_str,
 391         extendable,
 392         shape.sub_width(first_line_width(&output))?,
 393         Shape::indented(offset, context.config),
 394     );
 395     if last_line_width(&args) + first_line_width(&output) <= shape.width {
 396         Some(format!("{}{}", args, output))
 397     } else {
 398         Some(format!(
 399             "{}\n{}{}",
 400             args,
 401             offset.to_string(context.config),
 402             output.trim_left()
 403         ))
 404     }
 405 }
 406
 407 fn type_bound_colon(context: &RewriteContext) -> &'static str {
 408     colon_spaces(
 409         context.config.space_before_colon(),
 410         context.config.space_after_colon(),
 411     )
 412 }
 413
 414 impl Rewrite for ast::WherePredicate {
 415     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 416         // TODO: dead spans?
 417         let result = match *self {
 418             ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
 419                 ref bound_generic_params,
 420                 ref bounded_ty,
 421                 ref bounds,
 422                 ..
 423             }) => {
 424                 let type_str = bounded_ty.rewrite(context, shape)?;
 425
 426                 let colon = type_bound_colon(context);
 427
 428                 if let Some(lifetime_str) =
 429                     rewrite_lifetime_param(context, shape, bound_generic_params)
 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) => Some(
 533                 format!("?{}", tref.rewrite(context, shape.offset_left(1)?)?),
 534             ),
 535             ast::TyParamBound::RegionTyParamBound(ref l) => l.rewrite(context, shape),
 536         }
 537     }
 538 }
 539
 540 impl Rewrite for ast::Lifetime {
 541     fn rewrite(&self, _: &RewriteContext, _: Shape) -> Option<String> {
 542         Some(self.ident.to_string())
 543     }
 544 }
 545
 546 impl Rewrite for ast::TyParamBounds {
 547     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 548         let strs = self.iter()
 549             .map(|b| b.rewrite(context, shape))
 550             .collect::<Option<Vec<_>>>()?;
 551         Some(join_bounds(context, shape, &strs))
 552     }
 553 }
 554
 555 impl Rewrite for ast::TyParam {
 556     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 557         let mut result = String::with_capacity(128);
 558         // FIXME: If there are more than one attributes, this will force multiline.
 559         match self.attrs.rewrite(context, shape) {
 560             Some(ref rw) if !rw.is_empty() => result.push_str(&format!("{} ", rw)),
 561             _ => (),
 562         }
 563         result.push_str(&self.ident.to_string());
 564         if !self.bounds.is_empty() {
 565             result.push_str(type_bound_colon(context));
 566             let strs = self.bounds
 567                 .iter()
 568                 .map(|ty_bound| ty_bound.rewrite(context, shape))
 569                 .collect::<Option<Vec<_>>>()?;
 570             result.push_str(&join_bounds(context, shape, &strs));
 571         }
 572         if let Some(ref def) = self.default {
 573             let eq_str = match context.config.type_punctuation_density() {
 574                 TypeDensity::Compressed => "=",
 575                 TypeDensity::Wide => " = ",
 576             };
 577             result.push_str(eq_str);
 578             let budget = shape.width.checked_sub(result.len())?;
 579             let rewrite = def.rewrite(context, Shape::legacy(budget, shape.indent + result.len()))?;
 580             result.push_str(&rewrite);
 581         }
 582
 583         Some(result)
 584     }
 585 }
 586
 587 impl Rewrite for ast::PolyTraitRef {
 588     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 589         if let Some(lifetime_str) =
 590             rewrite_lifetime_param(context, shape, &self.bound_generic_params)
 591         {
 592             // 6 is "for<> ".len()
 593             let extra_offset = lifetime_str.len() + 6;
 594             let path_str = self.trait_ref
 595                 .rewrite(context, shape.offset_left(extra_offset)?)?;
 596
 597             Some(
 598                 if context.config.spaces_within_parens_and_brackets() && !lifetime_str.is_empty() {
 599                     format!("for< {} > {}", lifetime_str, path_str)
 600                 } else {
 601                     format!("for<{}> {}", lifetime_str, path_str)
 602                 },
 603             )
 604         } else {
 605             self.trait_ref.rewrite(context, shape)
 606         }
 607     }
 608 }
 609
 610 impl Rewrite for ast::TraitRef {
 611     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 612         rewrite_path(context, PathContext::Type, None, &self.path, shape)
 613     }
 614 }
 615
 616 impl Rewrite for ast::Ty {
 617     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 618         match self.node {
 619             ast::TyKind::TraitObject(ref bounds, ..) => bounds.rewrite(context, shape),
 620             ast::TyKind::Ptr(ref mt) => {
 621                 let prefix = match mt.mutbl {
 622                     Mutability::Mutable => "*mut ",
 623                     Mutability::Immutable => "*const ",
 624                 };
 625
 626                 rewrite_unary_prefix(context, prefix, &*mt.ty, shape)
 627             }
 628             ast::TyKind::Rptr(ref lifetime, ref mt) => {
 629                 let mut_str = format_mutability(mt.mutbl);
 630                 let mut_len = mut_str.len();
 631                 Some(match *lifetime {
 632                     Some(ref lifetime) => {
 633                         let lt_budget = shape.width.checked_sub(2 + mut_len)?;
 634                         let lt_str = lifetime.rewrite(
 635                             context,
 636                             Shape::legacy(lt_budget, shape.indent + 2 + mut_len),
 637                         )?;
 638                         let lt_len = lt_str.len();
 639                         let budget = shape.width.checked_sub(2 + mut_len + lt_len)?;
 640                         format!(
 641                             "&{} {}{}",
 642                             lt_str,
 643                             mut_str,
 644                             mt.ty.rewrite(
 645                                 context,
 646                                 Shape::legacy(budget, shape.indent + 2 + mut_len + lt_len)
 647                             )?
 648                         )
 649                     }
 650                     None => {
 651                         let budget = shape.width.checked_sub(1 + mut_len)?;
 652                         format!(
 653                             "&{}{}",
 654                             mut_str,
 655                             mt.ty.rewrite(
 656                                 context,
 657                                 Shape::legacy(budget, shape.indent + 1 + mut_len)
 658                             )?
 659                         )
 660                     }
 661                 })
 662             }
 663             // FIXME: we drop any comments here, even though it's a silly place to put
 664             // comments.
 665             ast::TyKind::Paren(ref ty) => {
 666                 let budget = shape.width.checked_sub(2)?;
 667                 ty.rewrite(context, Shape::legacy(budget, shape.indent + 1))
 668                     .map(|ty_str| {
 669                         if context.config.spaces_within_parens_and_brackets() {
 670                             format!("( {} )", ty_str)
 671                         } else {
 672                             format!("({})", ty_str)
 673                         }
 674                     })
 675             }
 676             ast::TyKind::Slice(ref ty) => {
 677                 let budget = if context.config.spaces_within_parens_and_brackets() {
 678                     shape.width.checked_sub(4)?
 679                 } else {
 680                     shape.width.checked_sub(2)?
 681                 };
 682                 ty.rewrite(context, Shape::legacy(budget, shape.indent + 1))
 683                     .map(|ty_str| {
 684                         if context.config.spaces_within_parens_and_brackets() {
 685                             format!("[ {} ]", ty_str)
 686                         } else {
 687                             format!("[{}]", ty_str)
 688                         }
 689                     })
 690             }
 691             ast::TyKind::Tup(ref items) => rewrite_tuple(
 692                 context,
 693                 &::utils::ptr_vec_to_ref_vec(items),
 694                 self.span,
 695                 shape,
 696             ),
 697             ast::TyKind::Path(ref q_self, ref path) => {
 698                 rewrite_path(context, PathContext::Type, q_self.as_ref(), path, shape)
 699             }
 700             ast::TyKind::Array(ref ty, ref repeats) => {
 701                 let use_spaces = context.config.spaces_within_parens_and_brackets();
 702                 let lbr = if use_spaces { "[ " } else { "[" };
 703                 let rbr = if use_spaces { " ]" } else { "]" };
 704                 rewrite_pair(
 705                     &**ty,
 706                     &**repeats,
 707                     PairParts::new(lbr, "; ", rbr),
 708                     context,
 709                     shape,
 710                     SeparatorPlace::Back,
 711                 )
 712             }
 713             ast::TyKind::Infer => {
 714                 if shape.width >= 1 {
 715                     Some("_".to_owned())
 716                 } else {
 717                     None
 718                 }
 719             }
 720             ast::TyKind::BareFn(ref bare_fn) => rewrite_bare_fn(bare_fn, self.span, context, shape),
 721             ast::TyKind::Never => Some(String::from("!")),
 722             ast::TyKind::Mac(ref mac) => {
 723                 rewrite_macro(mac, None, context, shape, MacroPosition::Expression)
 724             }
 725             ast::TyKind::ImplicitSelf => Some(String::from("")),
 726             ast::TyKind::ImplTrait(ref it) => it.rewrite(context, shape)
 727                 .map(|it_str| format!("impl {}", it_str)),
 728             ast::TyKind::Err | ast::TyKind::Typeof(..) => unreachable!(),
 729         }
 730     }
 731 }
 732
 733 fn rewrite_bare_fn(
 734     bare_fn: &ast::BareFnTy,
 735     span: Span,
 736     context: &RewriteContext,
 737     shape: Shape,
 738 ) -> Option<String> {
 739     let mut result = String::with_capacity(128);
 740
 741     if let Some(ref lifetime_str) = rewrite_lifetime_param(context, shape, &bare_fn.generic_params)
 742     {
 743         result.push_str("for<");
 744         // 6 = "for<> ".len(), 4 = "for<".
 745         // This doesn't work out so nicely for mutliline situation with lots of
 746         // rightward drift. If that is a problem, we could use the list stuff.
 747         result.push_str(lifetime_str);
 748         result.push_str("> ");
 749     }
 750
 751     result.push_str(::utils::format_unsafety(bare_fn.unsafety));
 752
 753     result.push_str(&format_abi(
 754         bare_fn.abi,
 755         context.config.force_explicit_abi(),
 756         false,
 757     ));
 758
 759     result.push_str("fn");
 760
 761     let func_ty_shape = shape.offset_left(result.len())?;
 762
 763     let rewrite = format_function_type(
 764         bare_fn.decl.inputs.iter(),
 765         &bare_fn.decl.output,
 766         bare_fn.decl.variadic,
 767         span,
 768         context,
 769         func_ty_shape,
 770     )?;
 771
 772     result.push_str(&rewrite);
 773
 774     Some(result)
 775 }
 776
 777 pub fn join_bounds(context: &RewriteContext, shape: Shape, type_strs: &[String]) -> String {
 778     // Try to join types in a single line
 779     let joiner = match context.config.type_punctuation_density() {
 780         TypeDensity::Compressed => "+",
 781         TypeDensity::Wide => " + ",
 782     };
 783     let result = type_strs.join(joiner);
 784     if result.contains('\n') || result.len() > shape.width {
 785         let joiner_indent = shape.indent.block_indent(context.config);
 786         let joiner = format!("{}+ ", joiner_indent.to_string_with_newline(context.config));
 787         type_strs.join(&joiner)
 788     } else {
 789         result
 790     }
 791 }
 792
 793 pub fn can_be_overflowed_type(context: &RewriteContext, ty: &ast::Ty, len: usize) -> bool {
 794     match ty.node {
 795         ast::TyKind::Path(..) | ast::TyKind::Tup(..) => context.use_block_indent() && len == 1,
 796         ast::TyKind::Rptr(_, ref mutty) | ast::TyKind::Ptr(ref mutty) => {
 797             can_be_overflowed_type(context, &*mutty.ty, len)
 798         }
 799         _ => false,
 800     }
 801 }
 802
 803 /// Returns `None` if there is no `LifetimeDef` in the given generic parameters.
 804 fn rewrite_lifetime_param(
 805     context: &RewriteContext,
 806     shape: Shape,
 807     generic_params: &[ast::GenericParam],
 808 ) -> Option<String> {
 809     let result = generic_params
 810         .iter()
 811         .filter(|p| p.is_lifetime_param())
 812         .map(|lt| lt.rewrite(context, shape))
 813         .collect::<Option<Vec<_>>>()?
 814         .join(", ");
 815     if result.is_empty() {
 816         None
 817     } else {
 818         Some(result)
 819     }
 820 }