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::{
  22     rewrite_assign_rhs, rewrite_pair, rewrite_tuple, rewrite_unary_prefix, PairParts, ToExpr,
  23 };
  24 use lists::{definitive_tactic, itemize_list, write_list, ListFormatting, Separator};
  25 use macros::{rewrite_macro, MacroPosition};
  26 use overflow;
  27 use rewrite::{Rewrite, RewriteContext};
  28 use shape::Shape;
  29 use spanned::Spanned;
  30 use utils::{
  31     colon_spaces, extra_offset, first_line_width, format_abi, format_mutability, last_line_width,
  32     mk_sp,
  33 };
  34
  35 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
  36 pub enum PathContext {
  37     Expr,
  38     Type,
  39     Import,
  40 }
  41
  42 // Does not wrap on simple segments.
  43 pub fn rewrite_path(
  44     context: &RewriteContext,
  45     path_context: PathContext,
  46     qself: Option<&ast::QSelf>,
  47     path: &ast::Path,
  48     shape: Shape,
  49 ) -> Option<String> {
  50     let skip_count = qself.map_or(0, |x| x.position);
  51
  52     let mut result = if path.is_global() && qself.is_none() && path_context != PathContext::Import {
  53         "::".to_owned()
  54     } else {
  55         String::new()
  56     };
  57
  58     let mut span_lo = path.span.lo();
  59
  60     if let Some(qself) = qself {
  61         result.push('<');
  62         if context.config.spaces_within_parens_and_brackets() {
  63             result.push_str(" ")
  64         }
  65
  66         let fmt_ty = qself.ty.rewrite(context, shape)?;
  67         result.push_str(&fmt_ty);
  68
  69         if skip_count > 0 {
  70             result.push_str(" as ");
  71             if path.is_global() && path_context != PathContext::Import {
  72                 result.push_str("::");
  73             }
  74
  75             // 3 = ">::".len()
  76             let shape = shape.sub_width(3)?;
  77
  78             result = rewrite_path_segments(
  79                 PathContext::Type,
  80                 result,
  81                 path.segments.iter().take(skip_count),
  82                 span_lo,
  83                 path.span.hi(),
  84                 context,
  85                 shape,
  86             )?;
  87         }
  88
  89         if context.config.spaces_within_parens_and_brackets() {
  90             result.push_str(" ")
  91         }
  92
  93         result.push_str(">::");
  94         span_lo = qself.ty.span.hi() + BytePos(1);
  95     }
  96
  97     rewrite_path_segments(
  98         path_context,
  99         result,
 100         path.segments.iter().skip(skip_count),
 101         span_lo,
 102         path.span.hi(),
 103         context,
 104         shape,
 105     )
 106 }
 107
 108 fn rewrite_path_segments<'a, I>(
 109     path_context: PathContext,
 110     mut buffer: String,
 111     iter: I,
 112     mut span_lo: BytePos,
 113     span_hi: BytePos,
 114     context: &RewriteContext,
 115     shape: Shape,
 116 ) -> Option<String>
 117 where
 118     I: Iterator<Item = &'a ast::PathSegment>,
 119 {
 120     let mut first = true;
 121     let shape = shape.visual_indent(0);
 122
 123     for segment in iter {
 124         // Indicates a global path, shouldn't be rendered.
 125         if segment.ident.name == keywords::CrateRoot.name() {
 126             continue;
 127         }
 128         if first {
 129             first = false;
 130         } else {
 131             buffer.push_str("::");
 132         }
 133
 134         let extra_offset = extra_offset(&buffer, shape);
 135         let new_shape = shape.shrink_left(extra_offset)?;
 136         let segment_string = rewrite_segment(
 137             path_context,
 138             segment,
 139             &mut span_lo,
 140             span_hi,
 141             context,
 142             new_shape,
 143         )?;
 144
 145         buffer.push_str(&segment_string);
 146     }
 147
 148     Some(buffer)
 149 }
 150
 151 #[derive(Debug)]
 152 enum SegmentParam<'a> {
 153     LifeTime(&'a ast::Lifetime),
 154     Type(&'a ast::Ty),
 155     Binding(&'a ast::TypeBinding),
 156 }
 157
 158 impl<'a> Spanned for SegmentParam<'a> {
 159     fn span(&self) -> Span {
 160         match *self {
 161             SegmentParam::LifeTime(lt) => lt.ident.span,
 162             SegmentParam::Type(ty) => ty.span,
 163             SegmentParam::Binding(binding) => binding.span,
 164         }
 165     }
 166 }
 167
 168 impl<'a> ToExpr for SegmentParam<'a> {
 169     fn to_expr(&self) -> Option<&ast::Expr> {
 170         None
 171     }
 172
 173     fn can_be_overflowed(&self, context: &RewriteContext, len: usize) -> bool {
 174         match *self {
 175             SegmentParam::Type(ty) => ty.can_be_overflowed(context, len),
 176             _ => false,
 177         }
 178     }
 179 }
 180
 181 impl<'a> Rewrite for SegmentParam<'a> {
 182     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 183         match *self {
 184             SegmentParam::LifeTime(lt) => lt.rewrite(context, shape),
 185             SegmentParam::Type(ty) => ty.rewrite(context, shape),
 186             SegmentParam::Binding(binding) => {
 187                 let mut result = match context.config.type_punctuation_density() {
 188                     TypeDensity::Wide => format!("{} = ", binding.ident),
 189                     TypeDensity::Compressed => format!("{}=", binding.ident),
 190                 };
 191                 let budget = shape.width.checked_sub(result.len())?;
 192                 let rewrite = binding
 193                     .ty
 194                     .rewrite(context, Shape::legacy(budget, shape.indent + result.len()))?;
 195                 result.push_str(&rewrite);
 196                 Some(result)
 197             }
 198         }
 199     }
 200 }
 201
 202 // Formats a path segment. There are some hacks involved to correctly determine
 203 // the segment's associated span since it's not part of the AST.
 204 //
 205 // The span_lo is assumed to be greater than the end of any previous segment's
 206 // parameters and lesser or equal than the start of current segment.
 207 //
 208 // span_hi is assumed equal to the end of the entire path.
 209 //
 210 // When the segment contains a positive number of parameters, we update span_lo
 211 // so that invariants described above will hold for the next segment.
 212 fn rewrite_segment(
 213     path_context: PathContext,
 214     segment: &ast::PathSegment,
 215     span_lo: &mut BytePos,
 216     span_hi: BytePos,
 217     context: &RewriteContext,
 218     shape: Shape,
 219 ) -> Option<String> {
 220     let mut result = String::with_capacity(128);
 221     result.push_str(&segment.ident.name.as_str());
 222
 223     let ident_len = result.len();
 224     let shape = if context.use_block_indent() {
 225         shape.offset_left(ident_len)?
 226     } else {
 227         shape.shrink_left(ident_len)?
 228     };
 229
 230     if let Some(ref params) = segment.parameters {
 231         match **params {
 232             ast::PathParameters::AngleBracketed(ref data)
 233                 if !data.lifetimes.is_empty() || !data.types.is_empty()
 234                     || !data.bindings.is_empty() =>
 235             {
 236                 let param_list = data.lifetimes
 237                     .iter()
 238                     .map(SegmentParam::LifeTime)
 239                     .chain(data.types.iter().map(|x| SegmentParam::Type(&*x)))
 240                     .chain(data.bindings.iter().map(|x| SegmentParam::Binding(&*x)))
 241                     .collect::<Vec<_>>();
 242
 243                 let separator = if path_context == PathContext::Expr {
 244                     "::"
 245                 } else {
 246                     ""
 247                 };
 248                 result.push_str(separator);
 249
 250                 let generics_str = overflow::rewrite_with_angle_brackets(
 251                     context,
 252                     "",
 253                     &param_list.iter().map(|e| &*e).collect::<Vec<_>>(),
 254                     shape,
 255                     mk_sp(*span_lo, span_hi),
 256                 )?;
 257
 258                 // Update position of last bracket.
 259                 *span_lo = context
 260                     .snippet_provider
 261                     .span_after(mk_sp(*span_lo, span_hi), "<");
 262
 263                 result.push_str(&generics_str)
 264             }
 265             ast::PathParameters::Parenthesized(ref data) => {
 266                 let output = match data.output {
 267                     Some(ref ty) => FunctionRetTy::Ty(ty.clone()),
 268                     None => FunctionRetTy::Default(codemap::DUMMY_SP),
 269                 };
 270                 result.push_str(&format_function_type(
 271                     data.inputs.iter().map(|x| &**x),
 272                     &output,
 273                     false,
 274                     data.span,
 275                     context,
 276                     shape,
 277                 )?);
 278             }
 279             _ => (),
 280         }
 281     }
 282
 283     Some(result)
 284 }
 285
 286 fn format_function_type<'a, I>(
 287     inputs: I,
 288     output: &FunctionRetTy,
 289     variadic: bool,
 290     span: Span,
 291     context: &RewriteContext,
 292     shape: Shape,
 293 ) -> Option<String>
 294 where
 295     I: ExactSizeIterator,
 296     <I as Iterator>::Item: Deref,
 297     <I::Item as Deref>::Target: Rewrite + Spanned + 'a,
 298 {
 299     // Code for handling variadics is somewhat duplicated for items, but they
 300     // are different enough to need some serious refactoring to share code.
 301     enum ArgumentKind<T>
 302     where
 303         T: Deref,
 304         <T as Deref>::Target: Rewrite + Spanned,
 305     {
 306         Regular(Box<T>),
 307         Variadic(BytePos),
 308     }
 309
 310     let variadic_arg = if variadic {
 311         let variadic_start = context.snippet_provider.span_before(span, "...");
 312         Some(ArgumentKind::Variadic(variadic_start))
 313     } else {
 314         None
 315     };
 316
 317     // 2 for ()
 318     let budget = shape.width.checked_sub(2)?;
 319     // 1 for (
 320     let offset = match context.config.indent_style() {
 321         IndentStyle::Block => {
 322             shape
 323                 .block()
 324                 .block_indent(context.config.tab_spaces())
 325                 .indent
 326         }
 327         IndentStyle::Visual => shape.indent + 1,
 328     };
 329     let list_shape = Shape::legacy(budget, offset);
 330     let list_lo = context.snippet_provider.span_after(span, "(");
 331     let items = itemize_list(
 332         context.snippet_provider,
 333         // FIXME Would be nice to avoid this allocation,
 334         // but I couldn't get the types to work out.
 335         inputs
 336             .map(|i| ArgumentKind::Regular(Box::new(i)))
 337             .chain(variadic_arg),
 338         ")",
 339         ",",
 340         |arg| match *arg {
 341             ArgumentKind::Regular(ref ty) => ty.span().lo(),
 342             ArgumentKind::Variadic(start) => start,
 343         },
 344         |arg| match *arg {
 345             ArgumentKind::Regular(ref ty) => ty.span().hi(),
 346             ArgumentKind::Variadic(start) => start + BytePos(3),
 347         },
 348         |arg| match *arg {
 349             ArgumentKind::Regular(ref ty) => ty.rewrite(context, list_shape),
 350             ArgumentKind::Variadic(_) => Some("...".to_owned()),
 351         },
 352         list_lo,
 353         span.hi(),
 354         false,
 355     );
 356
 357     let item_vec: Vec<_> = items.collect();
 358
 359     let tactic = definitive_tactic(
 360         &*item_vec,
 361         ListTactic::HorizontalVertical,
 362         Separator::Comma,
 363         budget,
 364     );
 365
 366     let fmt = ListFormatting {
 367         tactic,
 368         separator: ",",
 369         trailing_separator: if !context.use_block_indent() || variadic {
 370             SeparatorTactic::Never
 371         } else {
 372             context.config.trailing_comma()
 373         },
 374         separator_place: SeparatorPlace::Back,
 375         shape: list_shape,
 376         ends_with_newline: tactic.ends_with_newline(context.config.indent_style()),
 377         preserve_newline: true,
 378         config: context.config,
 379     };
 380
 381     let list_str = write_list(&item_vec, &fmt)?;
 382
 383     let ty_shape = match context.config.indent_style() {
 384         // 4 = " -> "
 385         IndentStyle::Block => shape.offset_left(4)?,
 386         IndentStyle::Visual => shape.block_left(4)?,
 387     };
 388     let output = match *output {
 389         FunctionRetTy::Ty(ref ty) => {
 390             let type_str = ty.rewrite(context, ty_shape)?;
 391             format!(" -> {}", type_str)
 392         }
 393         FunctionRetTy::Default(..) => String::new(),
 394     };
 395
 396     let args = if (!list_str.contains('\n') || list_str.is_empty()) && !output.contains('\n')
 397         || !context.use_block_indent()
 398     {
 399         format!("({})", list_str)
 400     } else {
 401         format!(
 402             "({}{}{})",
 403             offset.to_string_with_newline(context.config),
 404             list_str,
 405             shape.block().indent.to_string_with_newline(context.config),
 406         )
 407     };
 408     if last_line_width(&args) + first_line_width(&output) <= shape.width {
 409         Some(format!("{}{}", args, output))
 410     } else {
 411         Some(format!(
 412             "{}\n{}{}",
 413             args,
 414             offset.to_string(context.config),
 415             output.trim_left()
 416         ))
 417     }
 418 }
 419
 420 fn type_bound_colon(context: &RewriteContext) -> &'static str {
 421     colon_spaces(
 422         context.config.space_before_colon(),
 423         context.config.space_after_colon(),
 424     )
 425 }
 426
 427 impl Rewrite for ast::WherePredicate {
 428     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 429         // TODO: dead spans?
 430         let result = match *self {
 431             ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
 432                 ref bound_generic_params,
 433                 ref bounded_ty,
 434                 ref bounds,
 435                 ..
 436             }) => {
 437                 let type_str = bounded_ty.rewrite(context, shape)?;
 438                 let colon = type_bound_colon(context).trim_right();
 439                 let lhs = if let Some(lifetime_str) =
 440                     rewrite_lifetime_param(context, shape, bound_generic_params)
 441                 {
 442                     if context.config.spaces_within_parens_and_brackets()
 443                         && !lifetime_str.is_empty()
 444                     {
 445                         format!("for< {} > {}{}", lifetime_str, type_str, colon)
 446                     } else {
 447                         format!("for<{}> {}{}", lifetime_str, type_str, colon)
 448                     }
 449                 } else {
 450                     format!("{}{}", type_str, colon)
 451                 };
 452
 453                 rewrite_assign_rhs(context, lhs, bounds, shape)?
 454             }
 455             ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate {
 456                 ref lifetime,
 457                 ref bounds,
 458                 ..
 459             }) => rewrite_bounded_lifetime(lifetime, bounds, context, shape)?,
 460             ast::WherePredicate::EqPredicate(ast::WhereEqPredicate {
 461                 ref lhs_ty,
 462                 ref rhs_ty,
 463                 ..
 464             }) => {
 465                 let lhs_ty_str = lhs_ty.rewrite(context, shape).map(|lhs| lhs + " =")?;
 466                 rewrite_assign_rhs(context, lhs_ty_str, &**rhs_ty, shape)?
 467             }
 468         };
 469
 470         Some(result)
 471     }
 472 }
 473
 474 impl Rewrite for ast::LifetimeDef {
 475     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 476         rewrite_bounded_lifetime(&self.lifetime, &self.bounds, context, shape)
 477     }
 478 }
 479
 480 fn rewrite_bounded_lifetime(
 481     lt: &ast::Lifetime,
 482     bounds: &[ast::Lifetime],
 483     context: &RewriteContext,
 484     shape: Shape,
 485 ) -> Option<String> {
 486     let result = lt.rewrite(context, shape)?;
 487
 488     if bounds.is_empty() {
 489         Some(result)
 490     } else {
 491         let colon = type_bound_colon(context);
 492         let overhead = last_line_width(&result) + colon.len();
 493         let result = format!(
 494             "{}{}{}",
 495             result,
 496             colon,
 497             join_bounds(context, shape.sub_width(overhead)?, bounds, true)?
 498         );
 499         Some(result)
 500     }
 501 }
 502
 503 impl Rewrite for ast::TyParamBound {
 504     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 505         match *self {
 506             ast::TyParamBound::TraitTyParamBound(ref tref, ast::TraitBoundModifier::None) => {
 507                 tref.rewrite(context, shape)
 508             }
 509             ast::TyParamBound::TraitTyParamBound(ref tref, ast::TraitBoundModifier::Maybe) => Some(
 510                 format!("?{}", tref.rewrite(context, shape.offset_left(1)?)?),
 511             ),
 512             ast::TyParamBound::RegionTyParamBound(ref l) => l.rewrite(context, shape),
 513         }
 514     }
 515 }
 516
 517 impl Rewrite for ast::Lifetime {
 518     fn rewrite(&self, _: &RewriteContext, _: Shape) -> Option<String> {
 519         Some(self.ident.to_string())
 520     }
 521 }
 522
 523 /// A simple wrapper over type param bounds in trait.
 524 #[derive(new)]
 525 pub struct TraitTyParamBounds<'a> {
 526     inner: &'a ast::TyParamBounds,
 527 }
 528
 529 impl<'a> Rewrite for TraitTyParamBounds<'a> {
 530     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 531         join_bounds(context, shape, self.inner, false)
 532     }
 533 }
 534
 535 impl Rewrite for ast::TyParamBounds {
 536     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 537         join_bounds(context, shape, self, true)
 538     }
 539 }
 540
 541 impl Rewrite for ast::TyParam {
 542     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 543         let mut result = String::with_capacity(128);
 544         // FIXME: If there are more than one attributes, this will force multiline.
 545         match self.attrs.rewrite(context, shape) {
 546             Some(ref rw) if !rw.is_empty() => result.push_str(&format!("{} ", rw)),
 547             _ => (),
 548         }
 549         result.push_str(&self.ident.to_string());
 550         if !self.bounds.is_empty() {
 551             result.push_str(type_bound_colon(context));
 552             result.push_str(&self.bounds.rewrite(context, shape)?)
 553         }
 554         if let Some(ref def) = self.default {
 555             let eq_str = match context.config.type_punctuation_density() {
 556                 TypeDensity::Compressed => "=",
 557                 TypeDensity::Wide => " = ",
 558             };
 559             result.push_str(eq_str);
 560             let budget = shape.width.checked_sub(result.len())?;
 561             let rewrite = def.rewrite(context, Shape::legacy(budget, shape.indent + result.len()))?;
 562             result.push_str(&rewrite);
 563         }
 564
 565         Some(result)
 566     }
 567 }
 568
 569 impl Rewrite for ast::PolyTraitRef {
 570     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 571         if let Some(lifetime_str) =
 572             rewrite_lifetime_param(context, shape, &self.bound_generic_params)
 573         {
 574             // 6 is "for<> ".len()
 575             let extra_offset = lifetime_str.len() + 6;
 576             let path_str = self.trait_ref
 577                 .rewrite(context, shape.offset_left(extra_offset)?)?;
 578
 579             Some(
 580                 if context.config.spaces_within_parens_and_brackets() && !lifetime_str.is_empty() {
 581                     format!("for< {} > {}", lifetime_str, path_str)
 582                 } else {
 583                     format!("for<{}> {}", lifetime_str, path_str)
 584                 },
 585             )
 586         } else {
 587             self.trait_ref.rewrite(context, shape)
 588         }
 589     }
 590 }
 591
 592 impl Rewrite for ast::TraitRef {
 593     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 594         rewrite_path(context, PathContext::Type, None, &self.path, shape)
 595     }
 596 }
 597
 598 impl Rewrite for ast::Ty {
 599     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 600         match self.node {
 601             ast::TyKind::TraitObject(ref bounds, tobj_syntax) => {
 602                 // we have to consider 'dyn' keyword is used or not!!!
 603                 let is_dyn = tobj_syntax == ast::TraitObjectSyntax::Dyn;
 604                 // 4 is length of 'dyn '
 605                 let shape = if is_dyn { shape.offset_left(4)? } else { shape };
 606                 let res = bounds.rewrite(context, shape)?;
 607                 if is_dyn {
 608                     Some(format!("dyn {}", res))
 609                 } else {
 610                     Some(res)
 611                 }
 612             }
 613             ast::TyKind::Ptr(ref mt) => {
 614                 let prefix = match mt.mutbl {
 615                     Mutability::Mutable => "*mut ",
 616                     Mutability::Immutable => "*const ",
 617                 };
 618
 619                 rewrite_unary_prefix(context, prefix, &*mt.ty, shape)
 620             }
 621             ast::TyKind::Rptr(ref lifetime, ref mt) => {
 622                 let mut_str = format_mutability(mt.mutbl);
 623                 let mut_len = mut_str.len();
 624                 Some(match *lifetime {
 625                     Some(ref lifetime) => {
 626                         let lt_budget = shape.width.checked_sub(2 + mut_len)?;
 627                         let lt_str = lifetime.rewrite(
 628                             context,
 629                             Shape::legacy(lt_budget, shape.indent + 2 + mut_len),
 630                         )?;
 631                         let lt_len = lt_str.len();
 632                         let budget = shape.width.checked_sub(2 + mut_len + lt_len)?;
 633                         format!(
 634                             "&{} {}{}",
 635                             lt_str,
 636                             mut_str,
 637                             mt.ty.rewrite(
 638                                 context,
 639                                 Shape::legacy(budget, shape.indent + 2 + mut_len + lt_len)
 640                             )?
 641                         )
 642                     }
 643                     None => {
 644                         let budget = shape.width.checked_sub(1 + mut_len)?;
 645                         format!(
 646                             "&{}{}",
 647                             mut_str,
 648                             mt.ty.rewrite(
 649                                 context,
 650                                 Shape::legacy(budget, shape.indent + 1 + mut_len)
 651                             )?
 652                         )
 653                     }
 654                 })
 655             }
 656             // FIXME: we drop any comments here, even though it's a silly place to put
 657             // comments.
 658             ast::TyKind::Paren(ref ty) => {
 659                 let budget = shape.width.checked_sub(2)?;
 660                 ty.rewrite(context, Shape::legacy(budget, shape.indent + 1))
 661                     .map(|ty_str| {
 662                         if context.config.spaces_within_parens_and_brackets() {
 663                             format!("( {} )", ty_str)
 664                         } else {
 665                             format!("({})", ty_str)
 666                         }
 667                     })
 668             }
 669             ast::TyKind::Slice(ref ty) => {
 670                 let budget = if context.config.spaces_within_parens_and_brackets() {
 671                     shape.width.checked_sub(4)?
 672                 } else {
 673                     shape.width.checked_sub(2)?
 674                 };
 675                 ty.rewrite(context, Shape::legacy(budget, shape.indent + 1))
 676                     .map(|ty_str| {
 677                         if context.config.spaces_within_parens_and_brackets() {
 678                             format!("[ {} ]", ty_str)
 679                         } else {
 680                             format!("[{}]", ty_str)
 681                         }
 682                     })
 683             }
 684             ast::TyKind::Tup(ref items) => rewrite_tuple(
 685                 context,
 686                 &::utils::ptr_vec_to_ref_vec(items),
 687                 self.span,
 688                 shape,
 689             ),
 690             ast::TyKind::Path(ref q_self, ref path) => {
 691                 rewrite_path(context, PathContext::Type, q_self.as_ref(), path, shape)
 692             }
 693             ast::TyKind::Array(ref ty, ref repeats) => {
 694                 let use_spaces = context.config.spaces_within_parens_and_brackets();
 695                 let lbr = if use_spaces { "[ " } else { "[" };
 696                 let rbr = if use_spaces { " ]" } else { "]" };
 697                 rewrite_pair(
 698                     &**ty,
 699                     &**repeats,
 700                     PairParts::new(lbr, "; ", rbr),
 701                     context,
 702                     shape,
 703                     SeparatorPlace::Back,
 704                 )
 705             }
 706             ast::TyKind::Infer => {
 707                 if shape.width >= 1 {
 708                     Some("_".to_owned())
 709                 } else {
 710                     None
 711                 }
 712             }
 713             ast::TyKind::BareFn(ref bare_fn) => rewrite_bare_fn(bare_fn, self.span, context, shape),
 714             ast::TyKind::Never => Some(String::from("!")),
 715             ast::TyKind::Mac(ref mac) => {
 716                 rewrite_macro(mac, None, context, shape, MacroPosition::Expression)
 717             }
 718             ast::TyKind::ImplicitSelf => Some(String::from("")),
 719             ast::TyKind::ImplTrait(ref it) => it.rewrite(context, shape)
 720                 .map(|it_str| format!("impl {}", it_str)),
 721             ast::TyKind::Err | ast::TyKind::Typeof(..) => unreachable!(),
 722         }
 723     }
 724 }
 725
 726 fn rewrite_bare_fn(
 727     bare_fn: &ast::BareFnTy,
 728     span: Span,
 729     context: &RewriteContext,
 730     shape: Shape,
 731 ) -> Option<String> {
 732     let mut result = String::with_capacity(128);
 733
 734     if let Some(ref lifetime_str) = rewrite_lifetime_param(context, shape, &bare_fn.generic_params)
 735     {
 736         result.push_str("for<");
 737         // 6 = "for<> ".len(), 4 = "for<".
 738         // This doesn't work out so nicely for multiline situation with lots of
 739         // rightward drift. If that is a problem, we could use the list stuff.
 740         result.push_str(lifetime_str);
 741         result.push_str("> ");
 742     }
 743
 744     result.push_str(::utils::format_unsafety(bare_fn.unsafety));
 745
 746     result.push_str(&format_abi(
 747         bare_fn.abi,
 748         context.config.force_explicit_abi(),
 749         false,
 750     ));
 751
 752     result.push_str("fn");
 753
 754     let func_ty_shape = shape.offset_left(result.len())?;
 755
 756     let rewrite = format_function_type(
 757         bare_fn.decl.inputs.iter(),
 758         &bare_fn.decl.output,
 759         bare_fn.decl.variadic,
 760         span,
 761         context,
 762         func_ty_shape,
 763     )?;
 764
 765     result.push_str(&rewrite);
 766
 767     Some(result)
 768 }
 769
 770 fn join_bounds<T>(
 771     context: &RewriteContext,
 772     shape: Shape,
 773     items: &[T],
 774     need_indent: bool,
 775 ) -> Option<String>
 776 where
 777     T: Rewrite,
 778 {
 779     // Try to join types in a single line
 780     let joiner = match context.config.type_punctuation_density() {
 781         TypeDensity::Compressed => "+",
 782         TypeDensity::Wide => " + ",
 783     };
 784     let type_strs = items
 785         .iter()
 786         .map(|item| item.rewrite(context, shape))
 787         .collect::<Option<Vec<_>>>()?;
 788     let result = type_strs.join(joiner);
 789     if items.len() == 1 || (!result.contains('\n') && result.len() <= shape.width) {
 790         return Some(result);
 791     }
 792
 793     // We need to use multiple lines.
 794     let (type_strs, offset) = if need_indent {
 795         // Rewrite with additional indentation.
 796         let nested_shape = shape.block_indent(context.config.tab_spaces());
 797         let type_strs = items
 798             .iter()
 799             .map(|item| item.rewrite(context, nested_shape))
 800             .collect::<Option<Vec<_>>>()?;
 801         (type_strs, nested_shape.indent)
 802     } else {
 803         (type_strs, shape.indent)
 804     };
 805
 806     let joiner = format!("{}+ ", offset.to_string_with_newline(context.config));
 807     Some(type_strs.join(&joiner))
 808 }
 809
 810 pub fn can_be_overflowed_type(context: &RewriteContext, ty: &ast::Ty, len: usize) -> bool {
 811     match ty.node {
 812         ast::TyKind::Tup(..) => context.use_block_indent() && len == 1,
 813         ast::TyKind::Rptr(_, ref mutty) | ast::TyKind::Ptr(ref mutty) => {
 814             can_be_overflowed_type(context, &*mutty.ty, len)
 815         }
 816         _ => false,
 817     }
 818 }
 819
 820 /// Returns `None` if there is no `LifetimeDef` in the given generic parameters.
 821 fn rewrite_lifetime_param(
 822     context: &RewriteContext,
 823     shape: Shape,
 824     generic_params: &[ast::GenericParam],
 825 ) -> Option<String> {
 826     let result = generic_params
 827         .iter()
 828         .filter(|p| p.is_lifetime_param())
 829         .map(|lt| lt.rewrite(context, shape))
 830         .collect::<Option<Vec<_>>>()?
 831         .join(", ");
 832     if result.is_empty() {
 833         None
 834     } else {
 835         Some(result)
 836     }
 837 }