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::abi;
  15 use syntax::ast::{self, FunctionRetTy, Mutability};
  16 use syntax::codemap::{self, BytePos, Span};
  17 use syntax::print::pprust;
  18 use syntax::symbol::keywords;
  19
  20 use spanned::Spanned;
  21 use codemap::SpanUtils;
  22 use config::{IndentStyle, Style, TypeDensity};
  23 use expr::{rewrite_pair, rewrite_tuple, rewrite_unary_prefix, wrap_args_with_parens};
  24 use items::{format_generics_item_list, generics_shape_from_config};
  25 use lists::{definitive_tactic, itemize_list, write_list, ListFormatting, ListTactic, Separator,
  26             SeparatorPlace, SeparatorTactic};
  27 use rewrite::{Rewrite, RewriteContext};
  28 use shape::Shape;
  29 use utils::{colon_spaces, extra_offset, format_mutability, last_line_width, mk_sp};
  30
  31 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
  32 pub enum PathContext {
  33     Expr,
  34     Type,
  35     Import,
  36 }
  37
  38 // Does not wrap on simple segments.
  39 pub fn rewrite_path(
  40     context: &RewriteContext,
  41     path_context: PathContext,
  42     qself: Option<&ast::QSelf>,
  43     path: &ast::Path,
  44     shape: Shape,
  45 ) -> Option<String> {
  46     let skip_count = qself.map_or(0, |x| x.position);
  47
  48     let mut result = if path.is_global() && qself.is_none() && path_context != PathContext::Import {
  49         "::".to_owned()
  50     } else {
  51         String::new()
  52     };
  53
  54     let mut span_lo = path.span.lo();
  55
  56     if let Some(qself) = qself {
  57         result.push('<');
  58         if context.config.spaces_within_angle_brackets() {
  59             result.push_str(" ")
  60         }
  61
  62         let fmt_ty = try_opt!(qself.ty.rewrite(context, shape));
  63         result.push_str(&fmt_ty);
  64
  65         if skip_count > 0 {
  66             result.push_str(" as ");
  67             if path.is_global() && path_context != PathContext::Import {
  68                 result.push_str("::");
  69             }
  70
  71             let extra_offset = extra_offset(&result, shape);
  72             // 3 = ">::".len()
  73             let shape = try_opt!(try_opt!(shape.shrink_left(extra_offset)).sub_width(3));
  74
  75             result = try_opt!(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_angle_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 = try_opt!(shape.shrink_left(extra_offset));
 133         let segment_string = try_opt!(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 = try_opt!(shape.width.checked_sub(result.len()));
 176                 let rewrite = try_opt!(
 177                     binding
 178                         .ty
 179                         .rewrite(context, Shape::legacy(budget, shape.indent + result.len()))
 180                 );
 181                 result.push_str(&rewrite);
 182                 Some(result)
 183             }
 184         }
 185     }
 186 }
 187
 188 // Formats a path segment. There are some hacks involved to correctly determine
 189 // the segment's associated span since it's not part of the AST.
 190 //
 191 // The span_lo is assumed to be greater than the end of any previous segment's
 192 // parameters and lesser or equal than the start of current segment.
 193 //
 194 // span_hi is assumed equal to the end of the entire path.
 195 //
 196 // When the segment contains a positive number of parameters, we update span_lo
 197 // so that invariants described above will hold for the next segment.
 198 fn rewrite_segment(
 199     path_context: PathContext,
 200     segment: &ast::PathSegment,
 201     span_lo: &mut BytePos,
 202     span_hi: BytePos,
 203     context: &RewriteContext,
 204     shape: Shape,
 205 ) -> Option<String> {
 206     let ident_len = segment.identifier.to_string().len();
 207     let shape = try_opt!(shape.shrink_left(ident_len));
 208
 209     let params = if let Some(ref params) = segment.parameters {
 210         match **params {
 211             ast::PathParameters::AngleBracketed(ref data)
 212                 if !data.lifetimes.is_empty() || !data.types.is_empty()
 213                     || !data.bindings.is_empty() =>
 214             {
 215                 let param_list = data.lifetimes
 216                     .iter()
 217                     .map(SegmentParam::LifeTime)
 218                     .chain(data.types.iter().map(|x| SegmentParam::Type(&*x)))
 219                     .chain(data.bindings.iter().map(|x| SegmentParam::Binding(&*x)))
 220                     .collect::<Vec<_>>();
 221
 222                 let next_span_lo = param_list.last().unwrap().get_span().hi() + BytePos(1);
 223                 let list_lo = context.codemap.span_after(mk_sp(*span_lo, span_hi), "<");
 224                 let separator = if path_context == PathContext::Expr {
 225                     "::"
 226                 } else {
 227                     ""
 228                 };
 229
 230                 let generics_shape = try_opt!(generics_shape_from_config(
 231                     context.config,
 232                     shape,
 233                     separator.len(),
 234                 ));
 235                 let one_line_width = try_opt!(shape.width.checked_sub(separator.len() + 2));
 236                 let items = itemize_list(
 237                     context.codemap,
 238                     param_list.into_iter(),
 239                     ">",
 240                     |param| param.get_span().lo(),
 241                     |param| param.get_span().hi(),
 242                     |seg| seg.rewrite(context, generics_shape),
 243                     list_lo,
 244                     span_hi,
 245                     false,
 246                 );
 247                 let generics_str = try_opt!(format_generics_item_list(
 248                     context,
 249                     items,
 250                     generics_shape,
 251                     one_line_width,
 252                 ));
 253
 254                 // Update position of last bracket.
 255                 *span_lo = next_span_lo;
 256
 257                 format!("{}{}", separator, generics_str)
 258             }
 259             ast::PathParameters::Parenthesized(ref data) => {
 260                 let output = match data.output {
 261                     Some(ref ty) => FunctionRetTy::Ty(ty.clone()),
 262                     None => FunctionRetTy::Default(codemap::DUMMY_SP),
 263                 };
 264                 try_opt!(format_function_type(
 265                     data.inputs.iter().map(|x| &**x),
 266                     &output,
 267                     false,
 268                     data.span,
 269                     context,
 270                     shape,
 271                 ))
 272             }
 273             _ => String::new(),
 274         }
 275     } else {
 276         String::new()
 277     };
 278
 279     Some(format!("{}{}", segment.identifier, params))
 280 }
 281
 282 fn format_function_type<'a, I>(
 283     inputs: I,
 284     output: &FunctionRetTy,
 285     variadic: bool,
 286     span: Span,
 287     context: &RewriteContext,
 288     shape: Shape,
 289 ) -> Option<String>
 290 where
 291     I: ExactSizeIterator,
 292     <I as Iterator>::Item: Deref,
 293     <I::Item as Deref>::Target: Rewrite + Spanned + 'a,
 294 {
 295     // Code for handling variadics is somewhat duplicated for items, but they
 296     // are different enough to need some serious refactoring to share code.
 297     enum ArgumentKind<T>
 298     where
 299         T: Deref,
 300         <T as Deref>::Target: Rewrite + Spanned,
 301     {
 302         Regular(Box<T>),
 303         Variadic(BytePos),
 304     }
 305
 306     let variadic_arg = if variadic {
 307         let variadic_start = context.codemap.span_before(span, "...");
 308         Some(ArgumentKind::Variadic(variadic_start))
 309     } else {
 310         None
 311     };
 312
 313     // 2 for ()
 314     let budget = try_opt!(shape.width.checked_sub(2));
 315     // 1 for (
 316     let offset = match context.config.fn_args_layout() {
 317         IndentStyle::Block => {
 318             shape
 319                 .block()
 320                 .block_indent(context.config.tab_spaces())
 321                 .indent
 322         }
 323         IndentStyle::Visual => shape.indent + 1,
 324     };
 325     let list_shape = Shape::legacy(budget, offset);
 326     let list_lo = context.codemap.span_after(span, "(");
 327     let items = itemize_list(
 328         context.codemap,
 329         // FIXME Would be nice to avoid this allocation,
 330         // but I couldn't get the types to work out.
 331         inputs
 332             .map(|i| ArgumentKind::Regular(Box::new(i)))
 333             .chain(variadic_arg),
 334         ")",
 335         |arg| match *arg {
 336             ArgumentKind::Regular(ref ty) => ty.span().lo(),
 337             ArgumentKind::Variadic(start) => start,
 338         },
 339         |arg| match *arg {
 340             ArgumentKind::Regular(ref ty) => ty.span().hi(),
 341             ArgumentKind::Variadic(start) => start + BytePos(3),
 342         },
 343         |arg| match *arg {
 344             ArgumentKind::Regular(ref ty) => ty.rewrite(context, list_shape),
 345             ArgumentKind::Variadic(_) => Some("...".to_owned()),
 346         },
 347         list_lo,
 348         span.hi(),
 349         false,
 350     );
 351
 352     let item_vec: Vec<_> = items.collect();
 353
 354     let tactic = definitive_tactic(
 355         &*item_vec,
 356         ListTactic::HorizontalVertical,
 357         Separator::Comma,
 358         budget,
 359     );
 360
 361     let fmt = ListFormatting {
 362         tactic: tactic,
 363         separator: ",",
 364         trailing_separator: if !context.use_block_indent() || variadic {
 365             SeparatorTactic::Never
 366         } else {
 367             context.config.trailing_comma()
 368         },
 369         separator_place: SeparatorPlace::Back,
 370         shape: list_shape,
 371         ends_with_newline: tactic.ends_with_newline(context.config.fn_call_style()),
 372         preserve_newline: true,
 373         config: context.config,
 374     };
 375
 376     let list_str = try_opt!(write_list(&item_vec, &fmt));
 377
 378     let ty_shape = match context.config.fn_args_layout() {
 379         IndentStyle::Block => shape.block().block_indent(context.config.tab_spaces()),
 380         IndentStyle::Visual => try_opt!(shape.block_left(4)),
 381     };
 382     let output = match *output {
 383         FunctionRetTy::Ty(ref ty) => {
 384             let type_str = try_opt!(ty.rewrite(context, ty_shape));
 385             format!(" -> {}", type_str)
 386         }
 387         FunctionRetTy::Default(..) => String::new(),
 388     };
 389
 390     let shape = try_opt!(shape.sub_width(output.len()));
 391     let extendable = !list_str.contains('\n') || list_str.is_empty();
 392     let args = wrap_args_with_parens(
 393         context,
 394         &list_str,
 395         extendable,
 396         shape,
 397         Shape::indented(offset, context.config),
 398     );
 399     if last_line_width(&args) + output.len() > shape.width {
 400         Some(format!(
 401             "{}\n{}{}",
 402             args,
 403             offset.to_string(context.config),
 404             output.trim_left()
 405         ))
 406     } else {
 407         Some(format!("{}{}", args, output))
 408     }
 409 }
 410
 411 fn type_bound_colon(context: &RewriteContext) -> &'static str {
 412     colon_spaces(
 413         context.config.space_before_bound(),
 414         context.config.space_after_bound_colon(),
 415     )
 416 }
 417
 418 impl Rewrite for ast::WherePredicate {
 419     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 420         // TODO: dead spans?
 421         let result = match *self {
 422             ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
 423                 ref bound_lifetimes,
 424                 ref bounded_ty,
 425                 ref bounds,
 426                 ..
 427             }) => {
 428                 let type_str = try_opt!(bounded_ty.rewrite(context, shape));
 429
 430                 let colon = type_bound_colon(context);
 431
 432                 if !bound_lifetimes.is_empty() {
 433                     let lifetime_str: String = try_opt!(
 434                         bound_lifetimes
 435                             .iter()
 436                             .map(|lt| lt.rewrite(context, shape))
 437                             .collect::<Option<Vec<_>>>()
 438                     ).join(", ");
 439
 440                     // 6 = "for<> ".len()
 441                     let used_width = lifetime_str.len() + type_str.len() + colon.len() + 6;
 442                     let ty_shape = try_opt!(shape.block_left(used_width));
 443                     let bounds: Vec<_> = try_opt!(
 444                         bounds
 445                             .iter()
 446                             .map(|ty_bound| ty_bound.rewrite(context, ty_shape))
 447                             .collect()
 448                     );
 449                     let bounds_str = join_bounds(context, ty_shape, &bounds);
 450
 451                     if context.config.spaces_within_angle_brackets() && !lifetime_str.is_empty() {
 452                         format!(
 453                             "for< {} > {}{}{}",
 454                             lifetime_str,
 455                             type_str,
 456                             colon,
 457                             bounds_str
 458                         )
 459                     } else {
 460                         format!("for<{}> {}{}{}", lifetime_str, type_str, colon, bounds_str)
 461                     }
 462                 } else {
 463                     let used_width = type_str.len() + colon.len();
 464                     let ty_shape = match context.config.where_style() {
 465                         Style::Legacy => try_opt!(shape.block_left(used_width)),
 466                         Style::Rfc => shape.block_indent(context.config.tab_spaces()),
 467                     };
 468                     let bounds: Vec<_> = try_opt!(
 469                         bounds
 470                             .iter()
 471                             .map(|ty_bound| ty_bound.rewrite(context, ty_shape))
 472                             .collect()
 473                     );
 474                     let overhead = type_str.len() + colon.len();
 475                     let bounds_str =
 476                         join_bounds(context, try_opt!(ty_shape.sub_width(overhead)), &bounds);
 477
 478                     format!("{}{}{}", type_str, colon, bounds_str)
 479                 }
 480             }
 481             ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate {
 482                 ref lifetime,
 483                 ref bounds,
 484                 ..
 485             }) => try_opt!(rewrite_bounded_lifetime(
 486                 lifetime,
 487                 bounds.iter(),
 488                 context,
 489                 shape,
 490             )),
 491             ast::WherePredicate::EqPredicate(ast::WhereEqPredicate {
 492                 ref lhs_ty,
 493                 ref rhs_ty,
 494                 ..
 495             }) => {
 496                 let lhs_ty_str = try_opt!(lhs_ty.rewrite(context, shape));
 497                 // 3 = " = ".len()
 498                 let used_width = 3 + lhs_ty_str.len();
 499                 let budget = try_opt!(shape.width.checked_sub(used_width));
 500                 let rhs_ty_str = try_opt!(
 501                     rhs_ty.rewrite(context, Shape::legacy(budget, shape.indent + used_width))
 502                 );
 503                 format!("{} = {}", lhs_ty_str, rhs_ty_str)
 504             }
 505         };
 506
 507         Some(result)
 508     }
 509 }
 510
 511 impl Rewrite for ast::LifetimeDef {
 512     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 513         rewrite_bounded_lifetime(&self.lifetime, self.bounds.iter(), context, shape)
 514     }
 515 }
 516
 517 fn rewrite_bounded_lifetime<'b, I>(
 518     lt: &ast::Lifetime,
 519     bounds: I,
 520     context: &RewriteContext,
 521     shape: Shape,
 522 ) -> Option<String>
 523 where
 524     I: ExactSizeIterator<Item = &'b ast::Lifetime>,
 525 {
 526     let result = try_opt!(lt.rewrite(context, shape));
 527
 528     if bounds.len() == 0 {
 529         Some(result)
 530     } else {
 531         let appendix: Vec<_> = try_opt!(
 532             bounds
 533                 .into_iter()
 534                 .map(|b| b.rewrite(context, shape))
 535                 .collect()
 536         );
 537         let colon = type_bound_colon(context);
 538         let overhead = last_line_width(&result) + colon.len();
 539         let result = format!(
 540             "{}{}{}",
 541             result,
 542             colon,
 543             join_bounds(context, try_opt!(shape.sub_width(overhead)), &appendix)
 544         );
 545         Some(result)
 546     }
 547 }
 548
 549 impl Rewrite for ast::TyParamBound {
 550     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 551         match *self {
 552             ast::TyParamBound::TraitTyParamBound(ref tref, ast::TraitBoundModifier::None) => {
 553                 tref.rewrite(context, shape)
 554             }
 555             ast::TyParamBound::TraitTyParamBound(ref tref, ast::TraitBoundModifier::Maybe) => {
 556                 let budget = try_opt!(shape.width.checked_sub(1));
 557                 Some(format!(
 558                     "?{}",
 559                     try_opt!(tref.rewrite(context, Shape::legacy(budget, shape.indent + 1)))
 560                 ))
 561             }
 562             ast::TyParamBound::RegionTyParamBound(ref l) => l.rewrite(context, shape),
 563         }
 564     }
 565 }
 566
 567 impl Rewrite for ast::Lifetime {
 568     fn rewrite(&self, _: &RewriteContext, _: Shape) -> Option<String> {
 569         Some(pprust::lifetime_to_string(self))
 570     }
 571 }
 572
 573 impl Rewrite for ast::TyParamBounds {
 574     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 575         let strs: Vec<_> = try_opt!(self.iter().map(|b| b.rewrite(context, shape)).collect());
 576         join_bounds(context, shape, &strs).rewrite(context, shape)
 577     }
 578 }
 579
 580 impl Rewrite for ast::TyParam {
 581     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 582         let mut result = String::with_capacity(128);
 583         // FIXME: If there are more than one attributes, this will force multiline.
 584         match self.attrs.rewrite(context, shape) {
 585             Some(ref rw) if !rw.is_empty() => result.push_str(&format!("{} ", rw)),
 586             _ => (),
 587         }
 588         result.push_str(&self.ident.to_string());
 589         if !self.bounds.is_empty() {
 590             result.push_str(type_bound_colon(context));
 591             let strs: Vec<_> = try_opt!(
 592                 self.bounds
 593                     .iter()
 594                     .map(|ty_bound| ty_bound.rewrite(context, shape))
 595                     .collect()
 596             );
 597             result.push_str(&join_bounds(context, shape, &strs));
 598         }
 599         if let Some(ref def) = self.default {
 600             let eq_str = match context.config.type_punctuation_density() {
 601                 TypeDensity::Compressed => "=",
 602                 TypeDensity::Wide => " = ",
 603             };
 604             result.push_str(eq_str);
 605             let budget = try_opt!(shape.width.checked_sub(result.len()));
 606             let rewrite =
 607                 try_opt!(def.rewrite(context, Shape::legacy(budget, shape.indent + result.len())));
 608             result.push_str(&rewrite);
 609         }
 610
 611         Some(result)
 612     }
 613 }
 614
 615 impl Rewrite for ast::PolyTraitRef {
 616     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 617         if !self.bound_lifetimes.is_empty() {
 618             let lifetime_str: String = try_opt!(
 619                 self.bound_lifetimes
 620                     .iter()
 621                     .map(|lt| lt.rewrite(context, shape))
 622                     .collect::<Option<Vec<_>>>()
 623             ).join(", ");
 624
 625             // 6 is "for<> ".len()
 626             let extra_offset = lifetime_str.len() + 6;
 627             let max_path_width = try_opt!(shape.width.checked_sub(extra_offset));
 628             let path_str = try_opt!(self.trait_ref.rewrite(
 629                 context,
 630                 Shape::legacy(max_path_width, shape.indent + extra_offset),
 631             ));
 632
 633             Some(
 634                 if context.config.spaces_within_angle_brackets() && !lifetime_str.is_empty() {
 635                     format!("for< {} > {}", lifetime_str, path_str)
 636                 } else {
 637                     format!("for<{}> {}", lifetime_str, path_str)
 638                 },
 639             )
 640         } else {
 641             self.trait_ref.rewrite(context, shape)
 642         }
 643     }
 644 }
 645
 646 impl Rewrite for ast::TraitRef {
 647     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 648         rewrite_path(context, PathContext::Type, None, &self.path, shape)
 649     }
 650 }
 651
 652 impl Rewrite for ast::Ty {
 653     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 654         match self.node {
 655             ast::TyKind::TraitObject(ref bounds) => bounds.rewrite(context, shape),
 656             ast::TyKind::Ptr(ref mt) => {
 657                 let prefix = match mt.mutbl {
 658                     Mutability::Mutable => "*mut ",
 659                     Mutability::Immutable => "*const ",
 660                 };
 661
 662                 rewrite_unary_prefix(context, prefix, &*mt.ty, shape)
 663             }
 664             ast::TyKind::Rptr(ref lifetime, ref mt) => {
 665                 let mut_str = format_mutability(mt.mutbl);
 666                 let mut_len = mut_str.len();
 667                 Some(match *lifetime {
 668                     Some(ref lifetime) => {
 669                         let lt_budget = try_opt!(shape.width.checked_sub(2 + mut_len));
 670                         let lt_str = try_opt!(lifetime.rewrite(
 671                             context,
 672                             Shape::legacy(lt_budget, shape.indent + 2 + mut_len),
 673                         ));
 674                         let lt_len = lt_str.len();
 675                         let budget = try_opt!(shape.width.checked_sub(2 + mut_len + lt_len));
 676                         format!(
 677                             "&{} {}{}",
 678                             lt_str,
 679                             mut_str,
 680                             try_opt!(mt.ty.rewrite(
 681                                 context,
 682                                 Shape::legacy(budget, shape.indent + 2 + mut_len + lt_len),
 683                             ))
 684                         )
 685                     }
 686                     None => {
 687                         let budget = try_opt!(shape.width.checked_sub(1 + mut_len));
 688                         format!(
 689                             "&{}{}",
 690                             mut_str,
 691                             try_opt!(
 692                                 mt.ty.rewrite(
 693                                     context,
 694                                     Shape::legacy(budget, shape.indent + 1 + mut_len),
 695                                 )
 696                             )
 697                         )
 698                     }
 699                 })
 700             }
 701             // FIXME: we drop any comments here, even though it's a silly place to put
 702             // comments.
 703             ast::TyKind::Paren(ref ty) => {
 704                 let budget = try_opt!(shape.width.checked_sub(2));
 705                 ty.rewrite(context, Shape::legacy(budget, shape.indent + 1))
 706                     .map(|ty_str| if context.config.spaces_within_parens() {
 707                         format!("( {} )", ty_str)
 708                     } else {
 709                         format!("({})", ty_str)
 710                     })
 711             }
 712             ast::TyKind::Slice(ref ty) => {
 713                 let budget = if context.config.spaces_within_square_brackets() {
 714                     try_opt!(shape.width.checked_sub(4))
 715                 } else {
 716                     try_opt!(shape.width.checked_sub(2))
 717                 };
 718                 ty.rewrite(context, Shape::legacy(budget, shape.indent + 1))
 719                     .map(|ty_str| if context.config.spaces_within_square_brackets() {
 720                         format!("[ {} ]", ty_str)
 721                     } else {
 722                         format!("[{}]", ty_str)
 723                     })
 724             }
 725             ast::TyKind::Tup(ref items) => rewrite_tuple(
 726                 context,
 727                 &::utils::ptr_vec_to_ref_vec(&items),
 728                 self.span,
 729                 shape,
 730             ),
 731             ast::TyKind::Path(ref q_self, ref path) => {
 732                 rewrite_path(context, PathContext::Type, q_self.as_ref(), path, shape)
 733             }
 734             ast::TyKind::Array(ref ty, ref repeats) => {
 735                 let use_spaces = context.config.spaces_within_square_brackets();
 736                 let lbr = if use_spaces { "[ " } else { "[" };
 737                 let rbr = if use_spaces { " ]" } else { "]" };
 738                 rewrite_pair(
 739                     &**ty,
 740                     &**repeats,
 741                     lbr,
 742                     "; ",
 743                     rbr,
 744                     context,
 745                     shape,
 746                     SeparatorPlace::Back,
 747                 )
 748             }
 749             ast::TyKind::Infer => if shape.width >= 1 {
 750                 Some("_".to_owned())
 751             } else {
 752                 None
 753             },
 754             ast::TyKind::BareFn(ref bare_fn) => rewrite_bare_fn(bare_fn, self.span, context, shape),
 755             ast::TyKind::Never => Some(String::from("!")),
 756             ast::TyKind::Mac(..) => None,
 757             ast::TyKind::ImplicitSelf => Some(String::from("")),
 758             ast::TyKind::ImplTrait(ref it) => it.rewrite(context, shape)
 759                 .map(|it_str| format!("impl {}", it_str)),
 760             ast::TyKind::Err | ast::TyKind::Typeof(..) => unreachable!(),
 761         }
 762     }
 763 }
 764
 765 fn rewrite_bare_fn(
 766     bare_fn: &ast::BareFnTy,
 767     span: Span,
 768     context: &RewriteContext,
 769     shape: Shape,
 770 ) -> Option<String> {
 771     let mut result = String::with_capacity(128);
 772
 773     if !bare_fn.lifetimes.is_empty() {
 774         result.push_str("for<");
 775         // 6 = "for<> ".len(), 4 = "for<".
 776         // This doesn't work out so nicely for mutliline situation with lots of
 777         // rightward drift. If that is a problem, we could use the list stuff.
 778         result.push_str(&try_opt!(
 779             bare_fn
 780                 .lifetimes
 781                 .iter()
 782                 .map(|l| {
 783                     l.rewrite(
 784                         context,
 785                         Shape::legacy(try_opt!(shape.width.checked_sub(6)), shape.indent + 4),
 786                     )
 787                 })
 788                 .collect::<Option<Vec<_>>>()
 789         ).join(", "));
 790         result.push_str("> ");
 791     }
 792
 793     result.push_str(::utils::format_unsafety(bare_fn.unsafety));
 794
 795     if bare_fn.abi != abi::Abi::Rust {
 796         result.push_str(&::utils::format_abi(
 797             bare_fn.abi,
 798             context.config.force_explicit_abi(),
 799         ));
 800     }
 801
 802     result.push_str("fn");
 803
 804     let func_ty_shape = try_opt!(shape.offset_left(result.len()));
 805
 806     let rewrite = try_opt!(format_function_type(
 807         bare_fn.decl.inputs.iter(),
 808         &bare_fn.decl.output,
 809         bare_fn.decl.variadic,
 810         span,
 811         context,
 812         func_ty_shape,
 813     ));
 814
 815     result.push_str(&rewrite);
 816
 817     Some(result)
 818 }
 819
 820 pub fn join_bounds(context: &RewriteContext, shape: Shape, type_strs: &[String]) -> String {
 821     // Try to join types in a single line
 822     let joiner = match context.config.type_punctuation_density() {
 823         TypeDensity::Compressed => "+",
 824         TypeDensity::Wide => " + ",
 825     };
 826     let result = type_strs.join(joiner);
 827     if result.contains('\n') || result.len() > shape.width {
 828         let joiner_indent = shape.indent.block_indent(context.config);
 829         let joiner = format!("\n{}+ ", joiner_indent.to_string(context.config));
 830         type_strs.join(&joiner)
 831     } else {
 832         result
 833     }
 834 }
 835
 836 pub fn can_be_overflowed_type(context: &RewriteContext, ty: &ast::Ty, len: usize) -> bool {
 837     match ty.node {
 838         ast::TyKind::Path(..) | ast::TyKind::Tup(..) => context.use_block_indent() && len == 1,
 839         ast::TyKind::Rptr(_, ref mutty) | ast::TyKind::Ptr(ref mutty) => {
 840             can_be_overflowed_type(context, &*mutty.ty, len)
 841         }
 842         _ => false,
 843     }
 844 }