src/tools/rustfmt/src/types.rs

   1 use std::iter::ExactSizeIterator;
   2 use std::ops::Deref;
   3
   4 use rustc_ast::ast::{self, FnRetTy, Mutability};
   5 use rustc_span::{symbol::kw, symbol::Ident, BytePos, Pos, Span};
   6
   7 use crate::config::lists::*;
   8 use crate::config::{IndentStyle, TypeDensity, Version};
   9 use crate::expr::{
  10     format_expr, rewrite_assign_rhs, rewrite_call, rewrite_tuple, rewrite_unary_prefix, ExprType,
  11 };
  12 use crate::items::StructParts;
  13 use crate::lists::{
  14     definitive_tactic, itemize_list, write_list, ListFormatting, ListItem, Separator,
  15 };
  16 use crate::macros::{rewrite_macro, MacroPosition};
  17 use crate::overflow;
  18 use crate::pairs::{rewrite_pair, PairParts};
  19 use crate::rewrite::{Rewrite, RewriteContext};
  20 use crate::shape::Shape;
  21 use crate::source_map::SpanUtils;
  22 use crate::spanned::Spanned;
  23 use crate::utils::{
  24     colon_spaces, extra_offset, first_line_width, format_extern, format_mutability,
  25     last_line_extendable, last_line_width, mk_sp, rewrite_ident,
  26 };
  27 use crate::DEFAULT_VISIBILITY;
  28 use crate::{
  29     comment::{combine_strs_with_missing_comments, contains_comment},
  30     items::format_struct_struct,
  31 };
  32
  33 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
  34 pub(crate) enum PathContext {
  35     Expr,
  36     Type,
  37     Import,
  38 }
  39
  40 // Does not wrap on simple segments.
  41 pub(crate) fn rewrite_path(
  42     context: &RewriteContext<'_>,
  43     path_context: PathContext,
  44     qself: Option<&ast::QSelf>,
  45     path: &ast::Path,
  46     shape: Shape,
  47 ) -> Option<String> {
  48     let skip_count = qself.map_or(0, |x| x.position);
  49
  50     let mut result = if path.is_global() && qself.is_none() && path_context != PathContext::Import {
  51         "::".to_owned()
  52     } else {
  53         String::new()
  54     };
  55
  56     let mut span_lo = path.span.lo();
  57
  58     if let Some(qself) = qself {
  59         result.push('<');
  60
  61         let fmt_ty = qself.ty.rewrite(context, shape)?;
  62         result.push_str(&fmt_ty);
  63
  64         if skip_count > 0 {
  65             result.push_str(" as ");
  66             if path.is_global() && path_context != PathContext::Import {
  67                 result.push_str("::");
  68             }
  69
  70             // 3 = ">::".len()
  71             let shape = shape.sub_width(3)?;
  72
  73             result = rewrite_path_segments(
  74                 PathContext::Type,
  75                 result,
  76                 path.segments.iter().take(skip_count),
  77                 span_lo,
  78                 path.span.hi(),
  79                 context,
  80                 shape,
  81             )?;
  82         }
  83
  84         result.push_str(">::");
  85         span_lo = qself.ty.span.hi() + BytePos(1);
  86     }
  87
  88     rewrite_path_segments(
  89         path_context,
  90         result,
  91         path.segments.iter().skip(skip_count),
  92         span_lo,
  93         path.span.hi(),
  94         context,
  95         shape,
  96     )
  97 }
  98
  99 fn rewrite_path_segments<'a, I>(
 100     path_context: PathContext,
 101     mut buffer: String,
 102     iter: I,
 103     mut span_lo: BytePos,
 104     span_hi: BytePos,
 105     context: &RewriteContext<'_>,
 106     shape: Shape,
 107 ) -> Option<String>
 108 where
 109     I: Iterator<Item = &'a ast::PathSegment>,
 110 {
 111     let mut first = true;
 112     let shape = shape.visual_indent(0);
 113
 114     for segment in iter {
 115         // Indicates a global path, shouldn't be rendered.
 116         if segment.ident.name == kw::PathRoot {
 117             continue;
 118         }
 119         if first {
 120             first = false;
 121         } else {
 122             buffer.push_str("::");
 123         }
 124
 125         let extra_offset = extra_offset(&buffer, shape);
 126         let new_shape = shape.shrink_left(extra_offset)?;
 127         let segment_string = rewrite_segment(
 128             path_context,
 129             segment,
 130             &mut span_lo,
 131             span_hi,
 132             context,
 133             new_shape,
 134         )?;
 135
 136         buffer.push_str(&segment_string);
 137     }
 138
 139     Some(buffer)
 140 }
 141
 142 #[derive(Debug)]
 143 pub(crate) enum SegmentParam<'a> {
 144     Const(&'a ast::AnonConst),
 145     LifeTime(&'a ast::Lifetime),
 146     Type(&'a ast::Ty),
 147     Binding(&'a ast::AssocTyConstraint),
 148 }
 149
 150 impl<'a> SegmentParam<'a> {
 151     fn from_generic_arg(arg: &ast::GenericArg) -> SegmentParam<'_> {
 152         match arg {
 153             ast::GenericArg::Lifetime(ref lt) => SegmentParam::LifeTime(lt),
 154             ast::GenericArg::Type(ref ty) => SegmentParam::Type(ty),
 155             ast::GenericArg::Const(const_) => SegmentParam::Const(const_),
 156         }
 157     }
 158 }
 159
 160 impl<'a> Spanned for SegmentParam<'a> {
 161     fn span(&self) -> Span {
 162         match *self {
 163             SegmentParam::Const(const_) => const_.value.span,
 164             SegmentParam::LifeTime(lt) => lt.ident.span,
 165             SegmentParam::Type(ty) => ty.span,
 166             SegmentParam::Binding(binding) => binding.span,
 167         }
 168     }
 169 }
 170
 171 impl<'a> Rewrite for SegmentParam<'a> {
 172     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 173         match *self {
 174             SegmentParam::Const(const_) => const_.rewrite(context, shape),
 175             SegmentParam::LifeTime(lt) => lt.rewrite(context, shape),
 176             SegmentParam::Type(ty) => ty.rewrite(context, shape),
 177             SegmentParam::Binding(assoc_ty_constraint) => {
 178                 let mut result = match assoc_ty_constraint.kind {
 179                     ast::AssocTyConstraintKind::Bound { .. } => {
 180                         format!("{}: ", rewrite_ident(context, assoc_ty_constraint.ident))
 181                     }
 182                     ast::AssocTyConstraintKind::Equality { .. } => {
 183                         match context.config.type_punctuation_density() {
 184                             TypeDensity::Wide => {
 185                                 format!("{} = ", rewrite_ident(context, assoc_ty_constraint.ident))
 186                             }
 187                             TypeDensity::Compressed => {
 188                                 format!("{}=", rewrite_ident(context, assoc_ty_constraint.ident))
 189                             }
 190                         }
 191                     }
 192                 };
 193
 194                 let budget = shape.width.checked_sub(result.len())?;
 195                 let rewrite = assoc_ty_constraint
 196                     .kind
 197                     .rewrite(context, Shape::legacy(budget, shape.indent + result.len()))?;
 198                 result.push_str(&rewrite);
 199                 Some(result)
 200             }
 201         }
 202     }
 203 }
 204
 205 impl Rewrite for ast::AssocTyConstraintKind {
 206     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 207         match self {
 208             ast::AssocTyConstraintKind::Equality { ty } => ty.rewrite(context, shape),
 209             ast::AssocTyConstraintKind::Bound { bounds } => bounds.rewrite(context, shape),
 210         }
 211     }
 212 }
 213
 214 // Formats a path segment. There are some hacks involved to correctly determine
 215 // the segment's associated span since it's not part of the AST.
 216 //
 217 // The span_lo is assumed to be greater than the end of any previous segment's
 218 // parameters and lesser or equal than the start of current segment.
 219 //
 220 // span_hi is assumed equal to the end of the entire path.
 221 //
 222 // When the segment contains a positive number of parameters, we update span_lo
 223 // so that invariants described above will hold for the next segment.
 224 fn rewrite_segment(
 225     path_context: PathContext,
 226     segment: &ast::PathSegment,
 227     span_lo: &mut BytePos,
 228     span_hi: BytePos,
 229     context: &RewriteContext<'_>,
 230     shape: Shape,
 231 ) -> Option<String> {
 232     let mut result = String::with_capacity(128);
 233     result.push_str(rewrite_ident(context, segment.ident));
 234
 235     let ident_len = result.len();
 236     let shape = if context.use_block_indent() {
 237         shape.offset_left(ident_len)?
 238     } else {
 239         shape.shrink_left(ident_len)?
 240     };
 241
 242     if let Some(ref args) = segment.args {
 243         match **args {
 244             ast::GenericArgs::AngleBracketed(ref data) if !data.args.is_empty() => {
 245                 let param_list = data
 246                     .args
 247                     .iter()
 248                     .map(|x| match x {
 249                         ast::AngleBracketedArg::Arg(generic_arg) => {
 250                             SegmentParam::from_generic_arg(generic_arg)
 251                         }
 252                         ast::AngleBracketedArg::Constraint(constraint) => {
 253                             SegmentParam::Binding(constraint)
 254                         }
 255                     })
 256                     .collect::<Vec<_>>();
 257
 258                 // HACK: squeeze out the span between the identifier and the parameters.
 259                 // The hack is requried so that we don't remove the separator inside macro calls.
 260                 // This does not work in the presence of comment, hoping that people are
 261                 // sane about where to put their comment.
 262                 let separator_snippet = context
 263                     .snippet(mk_sp(segment.ident.span.hi(), data.span.lo()))
 264                     .trim();
 265                 let force_separator = context.inside_macro() && separator_snippet.starts_with("::");
 266                 let separator = if path_context == PathContext::Expr || force_separator {
 267                     "::"
 268                 } else {
 269                     ""
 270                 };
 271                 result.push_str(separator);
 272
 273                 let generics_str = overflow::rewrite_with_angle_brackets(
 274                     context,
 275                     "",
 276                     param_list.iter(),
 277                     shape,
 278                     mk_sp(*span_lo, span_hi),
 279                 )?;
 280
 281                 // Update position of last bracket.
 282                 *span_lo = context
 283                     .snippet_provider
 284                     .span_after(mk_sp(*span_lo, span_hi), "<");
 285
 286                 result.push_str(&generics_str)
 287             }
 288             ast::GenericArgs::Parenthesized(ref data) => {
 289                 result.push_str(&format_function_type(
 290                     data.inputs.iter().map(|x| &**x),
 291                     &data.output,
 292                     false,
 293                     data.span,
 294                     context,
 295                     shape,
 296                 )?);
 297             }
 298             _ => (),
 299         }
 300     }
 301
 302     Some(result)
 303 }
 304
 305 fn format_function_type<'a, I>(
 306     inputs: I,
 307     output: &FnRetTy,
 308     variadic: bool,
 309     span: Span,
 310     context: &RewriteContext<'_>,
 311     shape: Shape,
 312 ) -> Option<String>
 313 where
 314     I: ExactSizeIterator,
 315     <I as Iterator>::Item: Deref,
 316     <I::Item as Deref>::Target: Rewrite + Spanned + 'a,
 317 {
 318     debug!("format_function_type {:#?}", shape);
 319
 320     let ty_shape = match context.config.indent_style() {
 321         // 4 = " -> "
 322         IndentStyle::Block => shape.offset_left(4)?,
 323         IndentStyle::Visual => shape.block_left(4)?,
 324     };
 325     let output = match *output {
 326         FnRetTy::Ty(ref ty) => {
 327             let type_str = ty.rewrite(context, ty_shape)?;
 328             format!(" -> {}", type_str)
 329         }
 330         FnRetTy::Default(..) => String::new(),
 331     };
 332
 333     let list_shape = if context.use_block_indent() {
 334         Shape::indented(
 335             shape.block().indent.block_indent(context.config),
 336             context.config,
 337         )
 338     } else {
 339         // 2 for ()
 340         let budget = shape.width.checked_sub(2)?;
 341         // 1 for (
 342         let offset = shape.indent + 1;
 343         Shape::legacy(budget, offset)
 344     };
 345
 346     let is_inputs_empty = inputs.len() == 0;
 347     let list_lo = context.snippet_provider.span_after(span, "(");
 348     let (list_str, tactic) = if is_inputs_empty {
 349         let tactic = get_tactics(&[], &output, shape);
 350         let list_hi = context.snippet_provider.span_before(span, ")");
 351         let comment = context
 352             .snippet_provider
 353             .span_to_snippet(mk_sp(list_lo, list_hi))?
 354             .trim();
 355         let comment = if comment.starts_with("//") {
 356             format!(
 357                 "{}{}{}",
 358                 &list_shape.indent.to_string_with_newline(context.config),
 359                 comment,
 360                 &shape.block().indent.to_string_with_newline(context.config)
 361             )
 362         } else {
 363             comment.to_string()
 364         };
 365         (comment, tactic)
 366     } else {
 367         let items = itemize_list(
 368             context.snippet_provider,
 369             inputs,
 370             ")",
 371             ",",
 372             |arg| arg.span().lo(),
 373             |arg| arg.span().hi(),
 374             |arg| arg.rewrite(context, list_shape),
 375             list_lo,
 376             span.hi(),
 377             false,
 378         );
 379
 380         let item_vec: Vec<_> = items.collect();
 381         let tactic = get_tactics(&item_vec, &output, shape);
 382         let trailing_separator = if !context.use_block_indent() || variadic {
 383             SeparatorTactic::Never
 384         } else {
 385             context.config.trailing_comma()
 386         };
 387
 388         let fmt = ListFormatting::new(list_shape, context.config)
 389             .tactic(tactic)
 390             .trailing_separator(trailing_separator)
 391             .ends_with_newline(tactic.ends_with_newline(context.config.indent_style()))
 392             .preserve_newline(true);
 393         (write_list(&item_vec, &fmt)?, tactic)
 394     };
 395
 396     let args = if tactic == DefinitiveListTactic::Horizontal
 397         || !context.use_block_indent()
 398         || is_inputs_empty
 399     {
 400         format!("({})", list_str)
 401     } else {
 402         format!(
 403             "({}{}{})",
 404             list_shape.indent.to_string_with_newline(context.config),
 405             list_str,
 406             shape.block().indent.to_string_with_newline(context.config),
 407         )
 408     };
 409     if output.is_empty() || last_line_width(&args) + first_line_width(&output) <= shape.width {
 410         Some(format!("{}{}", args, output))
 411     } else {
 412         Some(format!(
 413             "{}\n{}{}",
 414             args,
 415             list_shape.indent.to_string(context.config),
 416             output.trim_start()
 417         ))
 418     }
 419 }
 420
 421 fn type_bound_colon(context: &RewriteContext<'_>) -> &'static str {
 422     colon_spaces(context.config)
 423 }
 424
 425 // If the return type is multi-lined, then force to use multiple lines for
 426 // arguments as well.
 427 fn get_tactics(item_vec: &[ListItem], output: &str, shape: Shape) -> DefinitiveListTactic {
 428     if output.contains('\n') {
 429         DefinitiveListTactic::Vertical
 430     } else {
 431         definitive_tactic(
 432             item_vec,
 433             ListTactic::HorizontalVertical,
 434             Separator::Comma,
 435             // 2 is for the case of ',\n'
 436             shape.width.saturating_sub(2 + output.len()),
 437         )
 438     }
 439 }
 440
 441 impl Rewrite for ast::WherePredicate {
 442     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 443         // FIXME: dead spans?
 444         let result = match *self {
 445             ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
 446                 ref bound_generic_params,
 447                 ref bounded_ty,
 448                 ref bounds,
 449                 ..
 450             }) => {
 451                 let type_str = bounded_ty.rewrite(context, shape)?;
 452                 let colon = type_bound_colon(context).trim_end();
 453                 let lhs = if let Some(lifetime_str) =
 454                     rewrite_lifetime_param(context, shape, bound_generic_params)
 455                 {
 456                     format!("for<{}> {}{}", lifetime_str, type_str, colon)
 457                 } else {
 458                     format!("{}{}", type_str, colon)
 459                 };
 460
 461                 rewrite_assign_rhs(context, lhs, bounds, shape)?
 462             }
 463             ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate {
 464                 ref lifetime,
 465                 ref bounds,
 466                 ..
 467             }) => rewrite_bounded_lifetime(lifetime, bounds, 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).map(|lhs| lhs + " =")?;
 474                 rewrite_assign_rhs(context, lhs_ty_str, &**rhs_ty, shape)?
 475             }
 476         };
 477
 478         Some(result)
 479     }
 480 }
 481
 482 impl Rewrite for ast::GenericArg {
 483     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 484         match *self {
 485             ast::GenericArg::Lifetime(ref lt) => lt.rewrite(context, shape),
 486             ast::GenericArg::Type(ref ty) => ty.rewrite(context, shape),
 487             ast::GenericArg::Const(ref const_) => const_.rewrite(context, shape),
 488         }
 489     }
 490 }
 491
 492 fn rewrite_bounded_lifetime(
 493     lt: &ast::Lifetime,
 494     bounds: &[ast::GenericBound],
 495     context: &RewriteContext<'_>,
 496     shape: Shape,
 497 ) -> Option<String> {
 498     let result = lt.rewrite(context, shape)?;
 499
 500     if bounds.is_empty() {
 501         Some(result)
 502     } else {
 503         let colon = type_bound_colon(context);
 504         let overhead = last_line_width(&result) + colon.len();
 505         let result = format!(
 506             "{}{}{}",
 507             result,
 508             colon,
 509             join_bounds(context, shape.sub_width(overhead)?, bounds, true)?
 510         );
 511         Some(result)
 512     }
 513 }
 514
 515 impl Rewrite for ast::AnonConst {
 516     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 517         format_expr(&self.value, ExprType::SubExpression, context, shape)
 518     }
 519 }
 520
 521 impl Rewrite for ast::Lifetime {
 522     fn rewrite(&self, context: &RewriteContext<'_>, _: Shape) -> Option<String> {
 523         Some(rewrite_ident(context, self.ident).to_owned())
 524     }
 525 }
 526
 527 impl Rewrite for ast::GenericBound {
 528     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 529         match *self {
 530             ast::GenericBound::Trait(ref poly_trait_ref, trait_bound_modifier) => {
 531                 let snippet = context.snippet(self.span());
 532                 let has_paren = snippet.starts_with('(') && snippet.ends_with(')');
 533                 let rewrite = match trait_bound_modifier {
 534                     ast::TraitBoundModifier::None => poly_trait_ref.rewrite(context, shape),
 535                     ast::TraitBoundModifier::Maybe => poly_trait_ref
 536                         .rewrite(context, shape.offset_left(1)?)
 537                         .map(|s| format!("?{}", s)),
 538                     ast::TraitBoundModifier::MaybeConst => poly_trait_ref
 539                         .rewrite(context, shape.offset_left(7)?)
 540                         .map(|s| format!("?const {}", s)),
 541                     ast::TraitBoundModifier::MaybeConstMaybe => poly_trait_ref
 542                         .rewrite(context, shape.offset_left(8)?)
 543                         .map(|s| format!("?const ?{}", s)),
 544                 };
 545                 rewrite.map(|s| if has_paren { format!("({})", s) } else { s })
 546             }
 547             ast::GenericBound::Outlives(ref lifetime) => lifetime.rewrite(context, shape),
 548         }
 549     }
 550 }
 551
 552 impl Rewrite for ast::GenericBounds {
 553     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 554         if self.is_empty() {
 555             return Some(String::new());
 556         }
 557
 558         join_bounds(context, shape, self, true)
 559     }
 560 }
 561
 562 impl Rewrite for ast::GenericParam {
 563     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 564         let mut result = String::with_capacity(128);
 565         // FIXME: If there are more than one attributes, this will force multiline.
 566         match self.attrs.rewrite(context, shape) {
 567             Some(ref rw) if !rw.is_empty() => result.push_str(&format!("{} ", rw)),
 568             _ => (),
 569         }
 570
 571         if let ast::GenericParamKind::Const {
 572             ref ty,
 573             kw_span: _,
 574             default: _,
 575         } = &self.kind
 576         {
 577             result.push_str("const ");
 578             result.push_str(rewrite_ident(context, self.ident));
 579             result.push_str(": ");
 580             result.push_str(&ty.rewrite(context, shape)?);
 581         } else {
 582             result.push_str(rewrite_ident(context, self.ident));
 583         }
 584
 585         if !self.bounds.is_empty() {
 586             result.push_str(type_bound_colon(context));
 587             result.push_str(&self.bounds.rewrite(context, shape)?)
 588         }
 589         if let ast::GenericParamKind::Type {
 590             default: Some(ref def),
 591         } = self.kind
 592         {
 593             let eq_str = match context.config.type_punctuation_density() {
 594                 TypeDensity::Compressed => "=",
 595                 TypeDensity::Wide => " = ",
 596             };
 597             result.push_str(eq_str);
 598             let budget = shape.width.checked_sub(result.len())?;
 599             let rewrite =
 600                 def.rewrite(context, Shape::legacy(budget, shape.indent + result.len()))?;
 601             result.push_str(&rewrite);
 602         }
 603
 604         Some(result)
 605     }
 606 }
 607
 608 impl Rewrite for ast::PolyTraitRef {
 609     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 610         if let Some(lifetime_str) =
 611             rewrite_lifetime_param(context, shape, &self.bound_generic_params)
 612         {
 613             // 6 is "for<> ".len()
 614             let extra_offset = lifetime_str.len() + 6;
 615             let path_str = self
 616                 .trait_ref
 617                 .rewrite(context, shape.offset_left(extra_offset)?)?;
 618
 619             Some(format!("for<{}> {}", lifetime_str, path_str))
 620         } else {
 621             self.trait_ref.rewrite(context, shape)
 622         }
 623     }
 624 }
 625
 626 impl Rewrite for ast::TraitRef {
 627     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 628         rewrite_path(context, PathContext::Type, None, &self.path, shape)
 629     }
 630 }
 631
 632 impl Rewrite for ast::Ty {
 633     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 634         match self.kind {
 635             ast::TyKind::TraitObject(ref bounds, tobj_syntax) => {
 636                 // we have to consider 'dyn' keyword is used or not!!!
 637                 let is_dyn = tobj_syntax == ast::TraitObjectSyntax::Dyn;
 638                 // 4 is length of 'dyn '
 639                 let shape = if is_dyn { shape.offset_left(4)? } else { shape };
 640                 let mut res = bounds.rewrite(context, shape)?;
 641                 // We may have falsely removed a trailing `+` inside macro call.
 642                 if context.inside_macro() && bounds.len() == 1 {
 643                     if context.snippet(self.span).ends_with('+') && !res.ends_with('+') {
 644                         res.push('+');
 645                     }
 646                 }
 647                 if is_dyn {
 648                     Some(format!("dyn {}", res))
 649                 } else {
 650                     Some(res)
 651                 }
 652             }
 653             ast::TyKind::Ptr(ref mt) => {
 654                 let prefix = match mt.mutbl {
 655                     Mutability::Mut => "*mut ",
 656                     Mutability::Not => "*const ",
 657                 };
 658
 659                 rewrite_unary_prefix(context, prefix, &*mt.ty, shape)
 660             }
 661             ast::TyKind::Rptr(ref lifetime, ref mt) => {
 662                 let mut_str = format_mutability(mt.mutbl);
 663                 let mut_len = mut_str.len();
 664                 let mut result = String::with_capacity(128);
 665                 result.push_str("&");
 666                 let ref_hi = context.snippet_provider.span_after(self.span(), "&");
 667                 let mut cmnt_lo = ref_hi;
 668
 669                 if let Some(ref lifetime) = *lifetime {
 670                     let lt_budget = shape.width.checked_sub(2 + mut_len)?;
 671                     let lt_str = lifetime.rewrite(
 672                         context,
 673                         Shape::legacy(lt_budget, shape.indent + 2 + mut_len),
 674                     )?;
 675                     let before_lt_span = mk_sp(cmnt_lo, lifetime.ident.span.lo());
 676                     if contains_comment(context.snippet(before_lt_span)) {
 677                         result = combine_strs_with_missing_comments(
 678                             context,
 679                             &result,
 680                             &lt_str,
 681                             before_lt_span,
 682                             shape,
 683                             true,
 684                         )?;
 685                     } else {
 686                         result.push_str(&lt_str);
 687                     }
 688                     result.push_str(" ");
 689                     cmnt_lo = lifetime.ident.span.hi();
 690                 }
 691
 692                 if ast::Mutability::Mut == mt.mutbl {
 693                     let mut_hi = context.snippet_provider.span_after(self.span(), "mut");
 694                     let before_mut_span = mk_sp(cmnt_lo, mut_hi - BytePos::from_usize(3));
 695                     if contains_comment(context.snippet(before_mut_span)) {
 696                         result = combine_strs_with_missing_comments(
 697                             context,
 698                             result.trim_end(),
 699                             mut_str,
 700                             before_mut_span,
 701                             shape,
 702                             true,
 703                         )?;
 704                     } else {
 705                         result.push_str(mut_str);
 706                     }
 707                     cmnt_lo = mut_hi;
 708                 }
 709
 710                 let before_ty_span = mk_sp(cmnt_lo, mt.ty.span.lo());
 711                 if contains_comment(context.snippet(before_ty_span)) {
 712                     result = combine_strs_with_missing_comments(
 713                         context,
 714                         result.trim_end(),
 715                         &mt.ty.rewrite(&context, shape)?,
 716                         before_ty_span,
 717                         shape,
 718                         true,
 719                     )?;
 720                 } else {
 721                     let used_width = last_line_width(&result);
 722                     let budget = shape.width.checked_sub(used_width)?;
 723                     let ty_str = mt
 724                         .ty
 725                         .rewrite(&context, Shape::legacy(budget, shape.indent + used_width))?;
 726                     result.push_str(&ty_str);
 727                 }
 728
 729                 Some(result)
 730             }
 731             // FIXME: we drop any comments here, even though it's a silly place to put
 732             // comments.
 733             ast::TyKind::Paren(ref ty) => {
 734                 if context.config.version() == Version::One
 735                     || context.config.indent_style() == IndentStyle::Visual
 736                 {
 737                     let budget = shape.width.checked_sub(2)?;
 738                     return ty
 739                         .rewrite(context, Shape::legacy(budget, shape.indent + 1))
 740                         .map(|ty_str| format!("({})", ty_str));
 741                 }
 742
 743                 // 2 = ()
 744                 if let Some(sh) = shape.sub_width(2) {
 745                     if let Some(ref s) = ty.rewrite(context, sh) {
 746                         if !s.contains('\n') {
 747                             return Some(format!("({})", s));
 748                         }
 749                     }
 750                 }
 751
 752                 let indent_str = shape.indent.to_string_with_newline(context.config);
 753                 let shape = shape
 754                     .block_indent(context.config.tab_spaces())
 755                     .with_max_width(context.config);
 756                 let rw = ty.rewrite(context, shape)?;
 757                 Some(format!(
 758                     "({}{}{})",
 759                     shape.to_string_with_newline(context.config),
 760                     rw,
 761                     indent_str
 762                 ))
 763             }
 764             ast::TyKind::Slice(ref ty) => {
 765                 let budget = shape.width.checked_sub(4)?;
 766                 ty.rewrite(context, Shape::legacy(budget, shape.indent + 1))
 767                     .map(|ty_str| format!("[{}]", ty_str))
 768             }
 769             ast::TyKind::Tup(ref items) => {
 770                 rewrite_tuple(context, items.iter(), self.span, shape, items.len() == 1)
 771             }
 772             ast::TyKind::AnonymousStruct(ref fields, recovered) => {
 773                 let ident = Ident::new(
 774                     kw::Struct,
 775                     mk_sp(self.span.lo(), self.span.lo() + BytePos(6)),
 776                 );
 777                 let data = ast::VariantData::Struct(fields.clone(), recovered);
 778                 let variant = ast::Variant {
 779                     attrs: vec![],
 780                     id: self.id,
 781                     span: self.span,
 782                     vis: DEFAULT_VISIBILITY,
 783                     ident,
 784                     data,
 785                     disr_expr: None,
 786                     is_placeholder: false,
 787                 };
 788                 format_struct_struct(
 789                     &context,
 790                     &StructParts::from_variant(&variant),
 791                     fields,
 792                     shape.indent,
 793                     None,
 794                 )
 795             }
 796             ast::TyKind::AnonymousUnion(ref fields, recovered) => {
 797                 let ident = Ident::new(
 798                     kw::Union,
 799                     mk_sp(self.span.lo(), self.span.lo() + BytePos(5)),
 800                 );
 801                 let data = ast::VariantData::Struct(fields.clone(), recovered);
 802                 let variant = ast::Variant {
 803                     attrs: vec![],
 804                     id: self.id,
 805                     span: self.span,
 806                     vis: DEFAULT_VISIBILITY,
 807                     ident,
 808                     data,
 809                     disr_expr: None,
 810                     is_placeholder: false,
 811                 };
 812                 format_struct_struct(
 813                     &context,
 814                     &StructParts::from_variant(&variant),
 815                     fields,
 816                     shape.indent,
 817                     None,
 818                 )
 819             }
 820             ast::TyKind::Path(ref q_self, ref path) => {
 821                 rewrite_path(context, PathContext::Type, q_self.as_ref(), path, shape)
 822             }
 823             ast::TyKind::Array(ref ty, ref repeats) => rewrite_pair(
 824                 &**ty,
 825                 &*repeats.value,
 826                 PairParts::new("[", "; ", "]"),
 827                 context,
 828                 shape,
 829                 SeparatorPlace::Back,
 830             ),
 831             ast::TyKind::Infer => {
 832                 if shape.width >= 1 {
 833                     Some("_".to_owned())
 834                 } else {
 835                     None
 836                 }
 837             }
 838             ast::TyKind::BareFn(ref bare_fn) => rewrite_bare_fn(bare_fn, self.span, context, shape),
 839             ast::TyKind::Never => Some(String::from("!")),
 840             ast::TyKind::MacCall(ref mac) => {
 841                 rewrite_macro(mac, None, context, shape, MacroPosition::Expression)
 842             }
 843             ast::TyKind::ImplicitSelf => Some(String::from("")),
 844             ast::TyKind::ImplTrait(_, ref it) => {
 845                 // Empty trait is not a parser error.
 846                 if it.is_empty() {
 847                     return Some("impl".to_owned());
 848                 }
 849                 let rw = if context.config.version() == Version::One {
 850                     it.rewrite(context, shape)
 851                 } else {
 852                     join_bounds(context, shape, it, false)
 853                 };
 854                 rw.map(|it_str| {
 855                     let space = if it_str.is_empty() { "" } else { " " };
 856                     format!("impl{}{}", space, it_str)
 857                 })
 858             }
 859             ast::TyKind::CVarArgs => Some("...".to_owned()),
 860             ast::TyKind::Err => Some(context.snippet(self.span).to_owned()),
 861             ast::TyKind::Typeof(ref anon_const) => rewrite_call(
 862                 context,
 863                 "typeof",
 864                 &[anon_const.value.clone()],
 865                 self.span,
 866                 shape,
 867             ),
 868         }
 869     }
 870 }
 871
 872 fn rewrite_bare_fn(
 873     bare_fn: &ast::BareFnTy,
 874     span: Span,
 875     context: &RewriteContext<'_>,
 876     shape: Shape,
 877 ) -> Option<String> {
 878     debug!("rewrite_bare_fn {:#?}", shape);
 879
 880     let mut result = String::with_capacity(128);
 881
 882     if let Some(ref lifetime_str) = rewrite_lifetime_param(context, shape, &bare_fn.generic_params)
 883     {
 884         result.push_str("for<");
 885         // 6 = "for<> ".len(), 4 = "for<".
 886         // This doesn't work out so nicely for multiline situation with lots of
 887         // rightward drift. If that is a problem, we could use the list stuff.
 888         result.push_str(lifetime_str);
 889         result.push_str("> ");
 890     }
 891
 892     result.push_str(crate::utils::format_unsafety(bare_fn.unsafety));
 893
 894     result.push_str(&format_extern(
 895         bare_fn.ext,
 896         context.config.force_explicit_abi(),
 897         false,
 898     ));
 899
 900     result.push_str("fn");
 901
 902     let func_ty_shape = if context.use_block_indent() {
 903         shape.offset_left(result.len())?
 904     } else {
 905         shape.visual_indent(result.len()).sub_width(result.len())?
 906     };
 907
 908     let rewrite = format_function_type(
 909         bare_fn.decl.inputs.iter(),
 910         &bare_fn.decl.output,
 911         bare_fn.decl.c_variadic(),
 912         span,
 913         context,
 914         func_ty_shape,
 915     )?;
 916
 917     result.push_str(&rewrite);
 918
 919     Some(result)
 920 }
 921
 922 fn is_generic_bounds_in_order(generic_bounds: &[ast::GenericBound]) -> bool {
 923     let is_trait = |b: &ast::GenericBound| match b {
 924         ast::GenericBound::Outlives(..) => false,
 925         ast::GenericBound::Trait(..) => true,
 926     };
 927     let is_lifetime = |b: &ast::GenericBound| !is_trait(b);
 928     let last_trait_index = generic_bounds.iter().rposition(is_trait);
 929     let first_lifetime_index = generic_bounds.iter().position(is_lifetime);
 930     match (last_trait_index, first_lifetime_index) {
 931         (Some(last_trait_index), Some(first_lifetime_index)) => {
 932             last_trait_index < first_lifetime_index
 933         }
 934         _ => true,
 935     }
 936 }
 937
 938 fn join_bounds(
 939     context: &RewriteContext<'_>,
 940     shape: Shape,
 941     items: &[ast::GenericBound],
 942     need_indent: bool,
 943 ) -> Option<String> {
 944     join_bounds_inner(context, shape, items, need_indent, false)
 945 }
 946
 947 fn join_bounds_inner(
 948     context: &RewriteContext<'_>,
 949     shape: Shape,
 950     items: &[ast::GenericBound],
 951     need_indent: bool,
 952     force_newline: bool,
 953 ) -> Option<String> {
 954     debug_assert!(!items.is_empty());
 955
 956     let generic_bounds_in_order = is_generic_bounds_in_order(items);
 957     let is_bound_extendable = |s: &str, b: &ast::GenericBound| match b {
 958         ast::GenericBound::Outlives(..) => true,
 959         ast::GenericBound::Trait(..) => last_line_extendable(s),
 960     };
 961
 962     let result = items.iter().enumerate().try_fold(
 963         (String::new(), None, false),
 964         |(strs, prev_trailing_span, prev_extendable), (i, item)| {
 965             let trailing_span = if i < items.len() - 1 {
 966                 let hi = context
 967                     .snippet_provider
 968                     .span_before(mk_sp(items[i + 1].span().lo(), item.span().hi()), "+");
 969
 970                 Some(mk_sp(item.span().hi(), hi))
 971             } else {
 972                 None
 973             };
 974             let (leading_span, has_leading_comment) = if i > 0 {
 975                 let lo = context
 976                     .snippet_provider
 977                     .span_after(mk_sp(items[i - 1].span().hi(), item.span().lo()), "+");
 978
 979                 let span = mk_sp(lo, item.span().lo());
 980
 981                 let has_comments = contains_comment(context.snippet(span));
 982
 983                 (Some(mk_sp(lo, item.span().lo())), has_comments)
 984             } else {
 985                 (None, false)
 986             };
 987             let prev_has_trailing_comment = match prev_trailing_span {
 988                 Some(ts) => contains_comment(context.snippet(ts)),
 989                 _ => false,
 990             };
 991
 992             let shape = if need_indent && force_newline {
 993                 shape
 994                     .block_indent(context.config.tab_spaces())
 995                     .with_max_width(context.config)
 996             } else {
 997                 shape
 998             };
 999             let whitespace = if force_newline && (!prev_extendable || !generic_bounds_in_order) {
1000                 shape
1001                     .indent
1002                     .to_string_with_newline(context.config)
1003                     .to_string()
1004             } else {
1005                 String::from(" ")
1006             };
1007
1008             let joiner = match context.config.type_punctuation_density() {
1009                 TypeDensity::Compressed => String::from("+"),
1010                 TypeDensity::Wide => whitespace + "+ ",
1011             };
1012             let joiner = if has_leading_comment {
1013                 joiner.trim_end()
1014             } else {
1015                 &joiner
1016             };
1017             let joiner = if prev_has_trailing_comment {
1018                 joiner.trim_start()
1019             } else {
1020                 joiner
1021             };
1022
1023             let (extendable, trailing_str) = if i == 0 {
1024                 let bound_str = item.rewrite(context, shape)?;
1025                 (is_bound_extendable(&bound_str, item), bound_str)
1026             } else {
1027                 let bound_str = &item.rewrite(context, shape)?;
1028                 match leading_span {
1029                     Some(ls) if has_leading_comment => (
1030                         is_bound_extendable(bound_str, item),
1031                         combine_strs_with_missing_comments(
1032                             context, joiner, bound_str, ls, shape, true,
1033                         )?,
1034                     ),
1035                     _ => (
1036                         is_bound_extendable(bound_str, item),
1037                         String::from(joiner) + bound_str,
1038                     ),
1039                 }
1040             };
1041             match prev_trailing_span {
1042                 Some(ts) if prev_has_trailing_comment => combine_strs_with_missing_comments(
1043                     context,
1044                     &strs,
1045                     &trailing_str,
1046                     ts,
1047                     shape,
1048                     true,
1049                 )
1050                 .map(|v| (v, trailing_span, extendable)),
1051                 _ => Some((
1052                     String::from(strs) + &trailing_str,
1053                     trailing_span,
1054                     extendable,
1055                 )),
1056             }
1057         },
1058     )?;
1059
1060     if !force_newline
1061         && items.len() > 1
1062         && (result.0.contains('\n') || result.0.len() > shape.width)
1063     {
1064         join_bounds_inner(context, shape, items, need_indent, true)
1065     } else {
1066         Some(result.0)
1067     }
1068 }
1069
1070 pub(crate) fn can_be_overflowed_type(
1071     context: &RewriteContext<'_>,
1072     ty: &ast::Ty,
1073     len: usize,
1074 ) -> bool {
1075     match ty.kind {
1076         ast::TyKind::Tup(..) => context.use_block_indent() && len == 1,
1077         ast::TyKind::Rptr(_, ref mutty) | ast::TyKind::Ptr(ref mutty) => {
1078             can_be_overflowed_type(context, &*mutty.ty, len)
1079         }
1080         _ => false,
1081     }
1082 }
1083
1084 /// Returns `None` if there is no `LifetimeDef` in the given generic parameters.
1085 fn rewrite_lifetime_param(
1086     context: &RewriteContext<'_>,
1087     shape: Shape,
1088     generic_params: &[ast::GenericParam],
1089 ) -> Option<String> {
1090     let result = generic_params
1091         .iter()
1092         .filter(|p| match p.kind {
1093             ast::GenericParamKind::Lifetime => true,
1094             _ => false,
1095         })
1096         .map(|lt| lt.rewrite(context, shape))
1097         .collect::<Option<Vec<_>>>()?
1098         .join(", ");
1099     if result.is_empty() {
1100         None
1101     } else {
1102         Some(result)
1103     }
1104 }