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 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, ListTactic, Separator,
  24             SeparatorPlace, SeparatorTactic};
  25 use macros::{rewrite_macro, MacroPosition};
  26 use rewrite::{Rewrite, RewriteContext};
  27 use shape::Shape;
  28 use spanned::Spanned;
  29 use utils::{colon_spaces, extra_offset, first_line_width, format_abi, format_mutability,
  30             last_line_width, mk_sp};
  31
  32 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
  33 pub enum PathContext {
  34     Expr,
  35     Type,
  36     Import,
  37 }
  38
  39 // Does not wrap on simple segments.
  40 pub fn rewrite_path(
  41     context: &RewriteContext,
  42     path_context: PathContext,
  43     qself: Option<&ast::QSelf>,
  44     path: &ast::Path,
  45     shape: Shape,
  46 ) -> Option<String> {
  47     let skip_count = qself.map_or(0, |x| x.position);
  48
  49     let mut result = if path.is_global() && qself.is_none() && path_context != PathContext::Import {
  50         "::".to_owned()
  51     } else {
  52         String::new()
  53     };
  54
  55     let mut span_lo = path.span.lo();
  56
  57     if let Some(qself) = qself {
  58         result.push('<');
  59         if context.config.spaces_within_parens_and_brackets() {
  60             result.push_str(" ")
  61         }
  62
  63         let fmt_ty = qself.ty.rewrite(context, shape)?;
  64         result.push_str(&fmt_ty);
  65
  66         if skip_count > 0 {
  67             result.push_str(" as ");
  68             if path.is_global() && path_context != PathContext::Import {
  69                 result.push_str("::");
  70             }
  71
  72             // 3 = ">::".len()
  73             let shape = shape.sub_width(3)?;
  74
  75             result = rewrite_path_segments(
  76                 PathContext::Type,
  77                 result,
  78                 path.segments.iter().take(skip_count),
  79                 span_lo,
  80                 path.span.hi(),
  81                 context,
  82                 shape,
  83             )?;
  84         }
  85
  86         if context.config.spaces_within_parens_and_brackets() {
  87             result.push_str(" ")
  88         }
  89
  90         result.push_str(">::");
  91         span_lo = qself.ty.span.hi() + BytePos(1);
  92     }
  93
  94     rewrite_path_segments(
  95         path_context,
  96         result,
  97         path.segments.iter().skip(skip_count),
  98         span_lo,
  99         path.span.hi(),
 100         context,
 101         shape,
 102     )
 103 }
 104
 105 fn rewrite_path_segments<'a, I>(
 106     path_context: PathContext,
 107     mut buffer: String,
 108     iter: I,
 109     mut span_lo: BytePos,
 110     span_hi: BytePos,
 111     context: &RewriteContext,
 112     shape: Shape,
 113 ) -> Option<String>
 114 where
 115     I: Iterator<Item = &'a ast::PathSegment>,
 116 {
 117     let mut first = true;
 118     let shape = shape.visual_indent(0);
 119
 120     for segment in iter {
 121         // Indicates a global path, shouldn't be rendered.
 122         if segment.identifier.name == keywords::CrateRoot.name() {
 123             continue;
 124         }
 125         if first {
 126             first = false;
 127         } else {
 128             buffer.push_str("::");
 129         }
 130
 131         let extra_offset = extra_offset(&buffer, shape);
 132         let new_shape = shape.shrink_left(extra_offset)?;
 133         let segment_string = rewrite_segment(
 134             path_context,
 135             segment,
 136             &mut span_lo,
 137             span_hi,
 138             context,
 139             new_shape,
 140         )?;
 141
 142         buffer.push_str(&segment_string);
 143     }
 144
 145     Some(buffer)
 146 }
 147
 148 #[derive(Debug)]
 149 enum SegmentParam<'a> {
 150     LifeTime(&'a ast::Lifetime),
 151     Type(&'a ast::Ty),
 152     Binding(&'a ast::TypeBinding),
 153 }
 154
 155 impl<'a> SegmentParam<'a> {
 156     fn get_span(&self) -> Span {
 157         match *self {
 158             SegmentParam::LifeTime(lt) => lt.span,
 159             SegmentParam::Type(ty) => ty.span,
 160             SegmentParam::Binding(binding) => binding.span,
 161         }
 162     }
 163 }
 164
 165 impl<'a> Rewrite for SegmentParam<'a> {
 166     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 167         match *self {
 168             SegmentParam::LifeTime(lt) => lt.rewrite(context, shape),
 169             SegmentParam::Type(ty) => ty.rewrite(context, shape),
 170             SegmentParam::Binding(binding) => {
 171                 let mut result = match context.config.type_punctuation_density() {
 172                     TypeDensity::Wide => format!("{} = ", binding.ident),
 173                     TypeDensity::Compressed => format!("{}=", binding.ident),
 174                 };
 175                 let budget = shape.width.checked_sub(result.len())?;
 176                 let rewrite = binding
 177                     .ty
 178                     .rewrite(context, Shape::legacy(budget, shape.indent + result.len()))?;
 179                 result.push_str(&rewrite);
 180                 Some(result)
 181             }
 182         }
 183     }
 184 }
 185
 186 // Formats a path segment. There are some hacks involved to correctly determine
 187 // the segment's associated span since it's not part of the AST.
 188 //
 189 // The span_lo is assumed to be greater than the end of any previous segment's
 190 // parameters and lesser or equal than the start of current segment.
 191 //
 192 // span_hi is assumed equal to the end of the entire path.
 193 //
 194 // When the segment contains a positive number of parameters, we update span_lo
 195 // so that invariants described above will hold for the next segment.
 196 fn rewrite_segment(
 197     path_context: PathContext,
 198     segment: &ast::PathSegment,
 199     span_lo: &mut BytePos,
 200     span_hi: BytePos,
 201     context: &RewriteContext,
 202     shape: Shape,
 203 ) -> Option<String> {
 204     let ident_len = segment.identifier.to_string().len();
 205     let shape = shape.shrink_left(ident_len)?;
 206
 207     let params = if let Some(ref params) = segment.parameters {
 208         match **params {
 209             ast::PathParameters::AngleBracketed(ref data)
 210                 if !data.lifetimes.is_empty() || !data.types.is_empty()
 211                     || !data.bindings.is_empty() =>
 212             {
 213                 let param_list = data.lifetimes
 214                     .iter()
 215                     .map(SegmentParam::LifeTime)
 216                     .chain(data.types.iter().map(|x| SegmentParam::Type(&*x)))
 217                     .chain(data.bindings.iter().map(|x| SegmentParam::Binding(&*x)))
 218                     .collect::<Vec<_>>();
 219
 220                 let next_span_lo = param_list.last().unwrap().get_span().hi() + BytePos(1);
 221                 let list_lo = context.codemap.span_after(mk_sp(*span_lo, span_hi), "<");
 222                 let separator = if path_context == PathContext::Expr {
 223                     "::"
 224                 } else {
 225                     ""
 226                 };
 227
 228                 let generics_shape =
 229                     generics_shape_from_config(context.config, shape, separator.len())?;
 230                 let one_line_width = shape.width.checked_sub(separator.len() + 2)?;
 231                 let items = itemize_list(
 232                     context.codemap,
 233                     param_list.into_iter(),
 234                     ">",
 235                     ",",
 236                     |param| param.get_span().lo(),
 237                     |param| param.get_span().hi(),
 238                     |seg| seg.rewrite(context, generics_shape),
 239                     list_lo,
 240                     span_hi,
 241                     false,
 242                 );
 243                 let generics_str =
 244                     format_generics_item_list(context, items, generics_shape, one_line_width)?;
 245
 246                 // Update position of last bracket.
 247                 *span_lo = next_span_lo;
 248
 249                 format!("{}{}", separator, generics_str)
 250             }
 251             ast::PathParameters::Parenthesized(ref data) => {
 252                 let output = match data.output {
 253                     Some(ref ty) => FunctionRetTy::Ty(ty.clone()),
 254                     None => FunctionRetTy::Default(codemap::DUMMY_SP),
 255                 };
 256                 format_function_type(
 257                     data.inputs.iter().map(|x| &**x),
 258                     &output,
 259                     false,
 260                     data.span,
 261                     context,
 262                     shape,
 263                 )?
 264             }
 265             _ => String::new(),
 266         }
 267     } else {
 268         String::new()
 269     };
 270
 271     Some(format!("{}{}", segment.identifier, params))
 272 }
 273
 274 fn format_function_type<'a, I>(
 275     inputs: I,
 276     output: &FunctionRetTy,
 277     variadic: bool,
 278     span: Span,
 279     context: &RewriteContext,
 280     shape: Shape,
 281 ) -> Option<String>
 282 where
 283     I: ExactSizeIterator,
 284     <I as Iterator>::Item: Deref,
 285     <I::Item as Deref>::Target: Rewrite + Spanned + 'a,
 286 {
 287     // Code for handling variadics is somewhat duplicated for items, but they
 288     // are different enough to need some serious refactoring to share code.
 289     enum ArgumentKind<T>
 290     where
 291         T: Deref,
 292         <T as Deref>::Target: Rewrite + Spanned,
 293     {
 294         Regular(Box<T>),
 295         Variadic(BytePos),
 296     }
 297
 298     let variadic_arg = if variadic {
 299         let variadic_start = context.codemap.span_before(span, "...");
 300         Some(ArgumentKind::Variadic(variadic_start))
 301     } else {
 302         None
 303     };
 304
 305     // 2 for ()
 306     let budget = shape.width.checked_sub(2)?;
 307     // 1 for (
 308     let offset = match context.config.indent_style() {
 309         IndentStyle::Block => {
 310             shape
 311                 .block()
 312                 .block_indent(context.config.tab_spaces())
 313                 .indent
 314         }
 315         IndentStyle::Visual => shape.indent + 1,
 316     };
 317     let list_shape = Shape::legacy(budget, offset);
 318     let list_lo = context.codemap.span_after(span, "(");
 319     let items = itemize_list(
 320         context.codemap,
 321         // FIXME Would be nice to avoid this allocation,
 322         // but I couldn't get the types to work out.
 323         inputs
 324             .map(|i| ArgumentKind::Regular(Box::new(i)))
 325             .chain(variadic_arg),
 326         ")",
 327         ",",
 328         |arg| match *arg {
 329             ArgumentKind::Regular(ref ty) => ty.span().lo(),
 330             ArgumentKind::Variadic(start) => start,
 331         },
 332         |arg| match *arg {
 333             ArgumentKind::Regular(ref ty) => ty.span().hi(),
 334             ArgumentKind::Variadic(start) => start + BytePos(3),
 335         },
 336         |arg| match *arg {
 337             ArgumentKind::Regular(ref ty) => ty.rewrite(context, list_shape),
 338             ArgumentKind::Variadic(_) => Some("...".to_owned()),
 339         },
 340         list_lo,
 341         span.hi(),
 342         false,
 343     );
 344
 345     let item_vec: Vec<_> = items.collect();
 346
 347     let tactic = definitive_tactic(
 348         &*item_vec,
 349         ListTactic::HorizontalVertical,
 350         Separator::Comma,
 351         budget,
 352     );
 353
 354     let fmt = ListFormatting {
 355         tactic: tactic,
 356         separator: ",",
 357         trailing_separator: if !context.use_block_indent() || variadic {
 358             SeparatorTactic::Never
 359         } else {
 360             context.config.trailing_comma()
 361         },
 362         separator_place: SeparatorPlace::Back,
 363         shape: list_shape,
 364         ends_with_newline: tactic.ends_with_newline(context.config.indent_style()),
 365         preserve_newline: true,
 366         config: context.config,
 367     };
 368
 369     let list_str = write_list(&item_vec, &fmt)?;
 370
 371     let ty_shape = match context.config.indent_style() {
 372         // 4 = " -> "
 373         IndentStyle::Block => shape.offset_left(4)?,
 374         IndentStyle::Visual => shape.block_left(4)?,
 375     };
 376     let output = match *output {
 377         FunctionRetTy::Ty(ref ty) => {
 378             let type_str = ty.rewrite(context, ty_shape)?;
 379             format!(" -> {}", type_str)
 380         }
 381         FunctionRetTy::Default(..) => String::new(),
 382     };
 383
 384     let extendable = (!list_str.contains('\n') || list_str.is_empty()) && !output.contains('\n');
 385     let args = wrap_args_with_parens(
 386         context,
 387         &list_str,
 388         extendable,
 389         shape.sub_width(first_line_width(&output))?,
 390         Shape::indented(offset, context.config),
 391     );
 392     if last_line_width(&args) + first_line_width(&output) <= shape.width {
 393         Some(format!("{}{}", args, output))
 394     } else {
 395         Some(format!(
 396             "{}\n{}{}",
 397             args,
 398             offset.to_string(context.config),
 399             output.trim_left()
 400         ))
 401     }
 402 }
 403
 404 fn type_bound_colon(context: &RewriteContext) -> &'static str {
 405     colon_spaces(
 406         context.config.space_before_colon(),
 407         context.config.space_after_colon(),
 408     )
 409 }
 410
 411 impl Rewrite for ast::WherePredicate {
 412     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 413         // TODO: dead spans?
 414         let result = match *self {
 415             ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
 416                 ref bound_generic_params,
 417                 ref bounded_ty,
 418                 ref bounds,
 419                 ..
 420             }) => {
 421                 let type_str = bounded_ty.rewrite(context, shape)?;
 422
 423                 let colon = type_bound_colon(context);
 424
 425                 if let Some(lifetime_str) =
 426                     rewrite_lifetime_param(context, shape, bound_generic_params)
 427                 {
 428                     // 6 = "for<> ".len()
 429                     let used_width = lifetime_str.len() + type_str.len() + colon.len() + 6;
 430                     let ty_shape = shape.offset_left(used_width)?;
 431                     let bounds = bounds
 432                         .iter()
 433                         .map(|ty_bound| ty_bound.rewrite(context, ty_shape))
 434                         .collect::<Option<Vec<_>>>()?;
 435                     let bounds_str = join_bounds(context, ty_shape, &bounds);
 436
 437                     if context.config.spaces_within_parens_and_brackets()
 438                         && !lifetime_str.is_empty()
 439                     {
 440                         format!(
 441                             "for< {} > {}{}{}",
 442                             lifetime_str, type_str, colon, bounds_str
 443                         )
 444                     } else {
 445                         format!("for<{}> {}{}{}", lifetime_str, type_str, colon, bounds_str)
 446                     }
 447                 } else {
 448                     let used_width = type_str.len() + colon.len();
 449                     let ty_shape = match context.config.indent_style() {
 450                         IndentStyle::Visual => shape.block_left(used_width)?,
 451                         IndentStyle::Block => shape,
 452                     };
 453                     let bounds = bounds
 454                         .iter()
 455                         .map(|ty_bound| ty_bound.rewrite(context, ty_shape))
 456                         .collect::<Option<Vec<_>>>()?;
 457                     let overhead = type_str.len() + colon.len();
 458                     let bounds_str = join_bounds(context, ty_shape.sub_width(overhead)?, &bounds);
 459
 460                     format!("{}{}{}", type_str, colon, bounds_str)
 461                 }
 462             }
 463             ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate {
 464                 ref lifetime,
 465                 ref bounds,
 466                 ..
 467             }) => rewrite_bounded_lifetime(lifetime, bounds.iter(), context, shape)?,
 468             ast::WherePredicate::EqPredicate(ast::WhereEqPredicate {
 469                 ref lhs_ty,
 470                 ref rhs_ty,
 471                 ..
 472             }) => {
 473                 let lhs_ty_str = lhs_ty.rewrite(context, shape)?;
 474                 // 3 = " = ".len()
 475                 let used_width = 3 + lhs_ty_str.len();
 476                 let budget = shape.width.checked_sub(used_width)?;
 477                 let rhs_ty_str =
 478                     rhs_ty.rewrite(context, Shape::legacy(budget, shape.indent + used_width))?;
 479                 format!("{} = {}", lhs_ty_str, rhs_ty_str)
 480             }
 481         };
 482
 483         Some(result)
 484     }
 485 }
 486
 487 impl Rewrite for ast::LifetimeDef {
 488     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 489         rewrite_bounded_lifetime(&self.lifetime, self.bounds.iter(), context, shape)
 490     }
 491 }
 492
 493 fn rewrite_bounded_lifetime<'b, I>(
 494     lt: &ast::Lifetime,
 495     bounds: I,
 496     context: &RewriteContext,
 497     shape: Shape,
 498 ) -> Option<String>
 499 where
 500     I: ExactSizeIterator<Item = &'b ast::Lifetime>,
 501 {
 502     let result = lt.rewrite(context, shape)?;
 503
 504     if bounds.len() == 0 {
 505         Some(result)
 506     } else {
 507         let appendix = bounds
 508             .into_iter()
 509             .map(|b| b.rewrite(context, shape))
 510             .collect::<Option<Vec<_>>>()?;
 511         let colon = type_bound_colon(context);
 512         let overhead = last_line_width(&result) + colon.len();
 513         let result = format!(
 514             "{}{}{}",
 515             result,
 516             colon,
 517             join_bounds(context, shape.sub_width(overhead)?, &appendix)
 518         );
 519         Some(result)
 520     }
 521 }
 522
 523 impl Rewrite for ast::TyParamBound {
 524     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 525         match *self {
 526             ast::TyParamBound::TraitTyParamBound(ref tref, ast::TraitBoundModifier::None) => {
 527                 tref.rewrite(context, shape)
 528             }
 529             ast::TyParamBound::TraitTyParamBound(ref tref, ast::TraitBoundModifier::Maybe) => {
 530                 Some(format!(
 531                     "?{}",
 532                     tref.rewrite(context, shape.offset_left(1)?)?
 533                 ))
 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(pprust::lifetime_to_string(self))
 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!("\n{}+ ", joiner_indent.to_string(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 }