src/types.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use std::iter::ExactSizeIterator;
  12 use std::ops::Deref;
  13
  14 use syntax::ast::{self, FunctionRetTy, Mutability};
  15 use syntax::codemap::{self, BytePos, Span};
  16 use syntax::print::pprust;
  17 use syntax::symbol::keywords;
  18
  19 use spanned::Spanned;
  20 use codemap::SpanUtils;
  21 use config::{IndentStyle, TypeDensity};
  22 use expr::{rewrite_pair, rewrite_tuple, rewrite_unary_prefix, wrap_args_with_parens, PairParts};
  23 use items::{format_generics_item_list, generics_shape_from_config};
  24 use lists::{definitive_tactic, itemize_list, write_list, ListFormatting, ListTactic, Separator,
  25             SeparatorPlace, SeparatorTactic};
  26 use macros::{rewrite_macro, MacroPosition};
  27 use rewrite::{Rewrite, RewriteContext};
  28 use shape::Shape;
  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_lifetimes,
 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 !bound_lifetimes.is_empty() {
 426                     let lifetime_str: String = bound_lifetimes
 427                         .iter()
 428                         .map(|lt| lt.rewrite(context, shape))
 429                         .collect::<Option<Vec<_>>>()?
 430                         .join(", ");
 431
 432                     // 6 = "for<> ".len()
 433                     let used_width = lifetime_str.len() + type_str.len() + colon.len() + 6;
 434                     let ty_shape = shape.offset_left(used_width)?;
 435                     let bounds = bounds
 436                         .iter()
 437                         .map(|ty_bound| ty_bound.rewrite(context, ty_shape))
 438                         .collect::<Option<Vec<_>>>()?;
 439                     let bounds_str = join_bounds(context, ty_shape, &bounds);
 440
 441                     if context.config.spaces_within_parens_and_brackets()
 442                         && !lifetime_str.is_empty()
 443                     {
 444                         format!(
 445                             "for< {} > {}{}{}",
 446                             lifetime_str, type_str, colon, bounds_str
 447                         )
 448                     } else {
 449                         format!("for<{}> {}{}{}", lifetime_str, type_str, colon, bounds_str)
 450                     }
 451                 } else {
 452                     let used_width = type_str.len() + colon.len();
 453                     let ty_shape = match context.config.indent_style() {
 454                         IndentStyle::Visual => shape.block_left(used_width)?,
 455                         IndentStyle::Block => shape,
 456                     };
 457                     let bounds = bounds
 458                         .iter()
 459                         .map(|ty_bound| ty_bound.rewrite(context, ty_shape))
 460                         .collect::<Option<Vec<_>>>()?;
 461                     let overhead = type_str.len() + colon.len();
 462                     let bounds_str = join_bounds(context, ty_shape.sub_width(overhead)?, &bounds);
 463
 464                     format!("{}{}{}", type_str, colon, bounds_str)
 465                 }
 466             }
 467             ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate {
 468                 ref lifetime,
 469                 ref bounds,
 470                 ..
 471             }) => rewrite_bounded_lifetime(lifetime, bounds.iter(), context, shape)?,
 472             ast::WherePredicate::EqPredicate(ast::WhereEqPredicate {
 473                 ref lhs_ty,
 474                 ref rhs_ty,
 475                 ..
 476             }) => {
 477                 let lhs_ty_str = lhs_ty.rewrite(context, shape)?;
 478                 // 3 = " = ".len()
 479                 let used_width = 3 + lhs_ty_str.len();
 480                 let budget = shape.width.checked_sub(used_width)?;
 481                 let rhs_ty_str =
 482                     rhs_ty.rewrite(context, Shape::legacy(budget, shape.indent + used_width))?;
 483                 format!("{} = {}", lhs_ty_str, rhs_ty_str)
 484             }
 485         };
 486
 487         Some(result)
 488     }
 489 }
 490
 491 impl Rewrite for ast::LifetimeDef {
 492     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 493         rewrite_bounded_lifetime(&self.lifetime, self.bounds.iter(), context, shape)
 494     }
 495 }
 496
 497 fn rewrite_bounded_lifetime<'b, I>(
 498     lt: &ast::Lifetime,
 499     bounds: I,
 500     context: &RewriteContext,
 501     shape: Shape,
 502 ) -> Option<String>
 503 where
 504     I: ExactSizeIterator<Item = &'b ast::Lifetime>,
 505 {
 506     let result = lt.rewrite(context, shape)?;
 507
 508     if bounds.len() == 0 {
 509         Some(result)
 510     } else {
 511         let appendix = bounds
 512             .into_iter()
 513             .map(|b| b.rewrite(context, shape))
 514             .collect::<Option<Vec<_>>>()?;
 515         let colon = type_bound_colon(context);
 516         let overhead = last_line_width(&result) + colon.len();
 517         let result = format!(
 518             "{}{}{}",
 519             result,
 520             colon,
 521             join_bounds(context, shape.sub_width(overhead)?, &appendix)
 522         );
 523         Some(result)
 524     }
 525 }
 526
 527 impl Rewrite for ast::TyParamBound {
 528     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 529         match *self {
 530             ast::TyParamBound::TraitTyParamBound(ref tref, ast::TraitBoundModifier::None) => {
 531                 tref.rewrite(context, shape)
 532             }
 533             ast::TyParamBound::TraitTyParamBound(ref tref, ast::TraitBoundModifier::Maybe) => {
 534                 Some(format!(
 535                     "?{}",
 536                     tref.rewrite(context, shape.offset_left(1)?)?
 537                 ))
 538             }
 539             ast::TyParamBound::RegionTyParamBound(ref l) => l.rewrite(context, shape),
 540         }
 541     }
 542 }
 543
 544 impl Rewrite for ast::Lifetime {
 545     fn rewrite(&self, _: &RewriteContext, _: Shape) -> Option<String> {
 546         Some(pprust::lifetime_to_string(self))
 547     }
 548 }
 549
 550 impl Rewrite for ast::TyParamBounds {
 551     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 552         let strs = self.iter()
 553             .map(|b| b.rewrite(context, shape))
 554             .collect::<Option<Vec<_>>>()?;
 555         Some(join_bounds(context, shape, &strs))
 556     }
 557 }
 558
 559 impl Rewrite for ast::TyParam {
 560     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 561         let mut result = String::with_capacity(128);
 562         // FIXME: If there are more than one attributes, this will force multiline.
 563         match self.attrs.rewrite(context, shape) {
 564             Some(ref rw) if !rw.is_empty() => result.push_str(&format!("{} ", rw)),
 565             _ => (),
 566         }
 567         result.push_str(&self.ident.to_string());
 568         if !self.bounds.is_empty() {
 569             result.push_str(type_bound_colon(context));
 570             let strs = self.bounds
 571                 .iter()
 572                 .map(|ty_bound| ty_bound.rewrite(context, shape))
 573                 .collect::<Option<Vec<_>>>()?;
 574             result.push_str(&join_bounds(context, shape, &strs));
 575         }
 576         if let Some(ref def) = self.default {
 577             let eq_str = match context.config.type_punctuation_density() {
 578                 TypeDensity::Compressed => "=",
 579                 TypeDensity::Wide => " = ",
 580             };
 581             result.push_str(eq_str);
 582             let budget = shape.width.checked_sub(result.len())?;
 583             let rewrite = def.rewrite(context, Shape::legacy(budget, shape.indent + result.len()))?;
 584             result.push_str(&rewrite);
 585         }
 586
 587         Some(result)
 588     }
 589 }
 590
 591 impl Rewrite for ast::PolyTraitRef {
 592     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 593         if !self.bound_lifetimes.is_empty() {
 594             let lifetime_str: String = self.bound_lifetimes
 595                 .iter()
 596                 .map(|lt| lt.rewrite(context, shape))
 597                 .collect::<Option<Vec<_>>>()?
 598                 .join(", ");
 599
 600             // 6 is "for<> ".len()
 601             let extra_offset = lifetime_str.len() + 6;
 602             let path_str = self.trait_ref
 603                 .rewrite(context, shape.offset_left(extra_offset)?)?;
 604
 605             Some(
 606                 if context.config.spaces_within_parens_and_brackets() && !lifetime_str.is_empty() {
 607                     format!("for< {} > {}", lifetime_str, path_str)
 608                 } else {
 609                     format!("for<{}> {}", lifetime_str, path_str)
 610                 },
 611             )
 612         } else {
 613             self.trait_ref.rewrite(context, shape)
 614         }
 615     }
 616 }
 617
 618 impl Rewrite for ast::TraitRef {
 619     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 620         rewrite_path(context, PathContext::Type, None, &self.path, shape)
 621     }
 622 }
 623
 624 impl Rewrite for ast::Ty {
 625     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 626         match self.node {
 627             ast::TyKind::TraitObject(ref bounds, ..) => bounds.rewrite(context, shape),
 628             ast::TyKind::Ptr(ref mt) => {
 629                 let prefix = match mt.mutbl {
 630                     Mutability::Mutable => "*mut ",
 631                     Mutability::Immutable => "*const ",
 632                 };
 633
 634                 rewrite_unary_prefix(context, prefix, &*mt.ty, shape)
 635             }
 636             ast::TyKind::Rptr(ref lifetime, ref mt) => {
 637                 let mut_str = format_mutability(mt.mutbl);
 638                 let mut_len = mut_str.len();
 639                 Some(match *lifetime {
 640                     Some(ref lifetime) => {
 641                         let lt_budget = shape.width.checked_sub(2 + mut_len)?;
 642                         let lt_str = lifetime.rewrite(
 643                             context,
 644                             Shape::legacy(lt_budget, shape.indent + 2 + mut_len),
 645                         )?;
 646                         let lt_len = lt_str.len();
 647                         let budget = shape.width.checked_sub(2 + mut_len + lt_len)?;
 648                         format!(
 649                             "&{} {}{}",
 650                             lt_str,
 651                             mut_str,
 652                             mt.ty.rewrite(
 653                                 context,
 654                                 Shape::legacy(budget, shape.indent + 2 + mut_len + lt_len)
 655                             )?
 656                         )
 657                     }
 658                     None => {
 659                         let budget = shape.width.checked_sub(1 + mut_len)?;
 660                         format!(
 661                             "&{}{}",
 662                             mut_str,
 663                             mt.ty.rewrite(
 664                                 context,
 665                                 Shape::legacy(budget, shape.indent + 1 + mut_len)
 666                             )?
 667                         )
 668                     }
 669                 })
 670             }
 671             // FIXME: we drop any comments here, even though it's a silly place to put
 672             // comments.
 673             ast::TyKind::Paren(ref ty) => {
 674                 let budget = shape.width.checked_sub(2)?;
 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::Slice(ref ty) => {
 685                 let budget = if context.config.spaces_within_parens_and_brackets() {
 686                     shape.width.checked_sub(4)?
 687                 } else {
 688                     shape.width.checked_sub(2)?
 689                 };
 690                 ty.rewrite(context, Shape::legacy(budget, shape.indent + 1))
 691                     .map(|ty_str| {
 692                         if context.config.spaces_within_parens_and_brackets() {
 693                             format!("[ {} ]", ty_str)
 694                         } else {
 695                             format!("[{}]", ty_str)
 696                         }
 697                     })
 698             }
 699             ast::TyKind::Tup(ref items) => rewrite_tuple(
 700                 context,
 701                 &::utils::ptr_vec_to_ref_vec(items),
 702                 self.span,
 703                 shape,
 704             ),
 705             ast::TyKind::Path(ref q_self, ref path) => {
 706                 rewrite_path(context, PathContext::Type, q_self.as_ref(), path, shape)
 707             }
 708             ast::TyKind::Array(ref ty, ref repeats) => {
 709                 let use_spaces = context.config.spaces_within_parens_and_brackets();
 710                 let lbr = if use_spaces { "[ " } else { "[" };
 711                 let rbr = if use_spaces { " ]" } else { "]" };
 712                 rewrite_pair(
 713                     &**ty,
 714                     &**repeats,
 715                     PairParts::new(lbr, "; ", rbr),
 716                     context,
 717                     shape,
 718                     SeparatorPlace::Back,
 719                 )
 720             }
 721             ast::TyKind::Infer => {
 722                 if shape.width >= 1 {
 723                     Some("_".to_owned())
 724                 } else {
 725                     None
 726                 }
 727             }
 728             ast::TyKind::BareFn(ref bare_fn) => rewrite_bare_fn(bare_fn, self.span, context, shape),
 729             ast::TyKind::Never => Some(String::from("!")),
 730             ast::TyKind::Mac(ref mac) => {
 731                 rewrite_macro(mac, None, context, shape, MacroPosition::Expression)
 732             }
 733             ast::TyKind::ImplicitSelf => Some(String::from("")),
 734             ast::TyKind::ImplTrait(ref it) => it.rewrite(context, shape)
 735                 .map(|it_str| format!("impl {}", it_str)),
 736             ast::TyKind::Err | ast::TyKind::Typeof(..) => unreachable!(),
 737         }
 738     }
 739 }
 740
 741 fn rewrite_bare_fn(
 742     bare_fn: &ast::BareFnTy,
 743     span: Span,
 744     context: &RewriteContext,
 745     shape: Shape,
 746 ) -> Option<String> {
 747     let mut result = String::with_capacity(128);
 748
 749     if !bare_fn.lifetimes.is_empty() {
 750         result.push_str("for<");
 751         // 6 = "for<> ".len(), 4 = "for<".
 752         // This doesn't work out so nicely for mutliline situation with lots of
 753         // rightward drift. If that is a problem, we could use the list stuff.
 754         result.push_str(&bare_fn
 755             .lifetimes
 756             .iter()
 757             .map(|l| {
 758                 l.rewrite(
 759                     context,
 760                     Shape::legacy(shape.width.checked_sub(6)?, shape.indent + 4),
 761                 )
 762             })
 763             .collect::<Option<Vec<_>>>()?
 764             .join(", "));
 765         result.push_str("> ");
 766     }
 767
 768     result.push_str(::utils::format_unsafety(bare_fn.unsafety));
 769
 770     result.push_str(&format_abi(
 771         bare_fn.abi,
 772         context.config.force_explicit_abi(),
 773         false,
 774     ));
 775
 776     result.push_str("fn");
 777
 778     let func_ty_shape = shape.offset_left(result.len())?;
 779
 780     let rewrite = format_function_type(
 781         bare_fn.decl.inputs.iter(),
 782         &bare_fn.decl.output,
 783         bare_fn.decl.variadic,
 784         span,
 785         context,
 786         func_ty_shape,
 787     )?;
 788
 789     result.push_str(&rewrite);
 790
 791     Some(result)
 792 }
 793
 794 pub fn join_bounds(context: &RewriteContext, shape: Shape, type_strs: &[String]) -> String {
 795     // Try to join types in a single line
 796     let joiner = match context.config.type_punctuation_density() {
 797         TypeDensity::Compressed => "+",
 798         TypeDensity::Wide => " + ",
 799     };
 800     let result = type_strs.join(joiner);
 801     if result.contains('\n') || result.len() > shape.width {
 802         let joiner_indent = shape.indent.block_indent(context.config);
 803         let joiner = format!("\n{}+ ", joiner_indent.to_string(context.config));
 804         type_strs.join(&joiner)
 805     } else {
 806         result
 807     }
 808 }
 809
 810 pub fn can_be_overflowed_type(context: &RewriteContext, ty: &ast::Ty, len: usize) -> bool {
 811     match ty.node {
 812         ast::TyKind::Path(..) | 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 }