src/librustc/ty/print/pretty.rs

   1 use crate::hir;
   2 use crate::hir::def::Namespace;
   3 use crate::hir::map::{DefPathData, DisambiguatedDefPathData};
   4 use crate::hir::def_id::{CrateNum, DefId, CRATE_DEF_INDEX, LOCAL_CRATE};
   5 use crate::middle::cstore::{ExternCrate, ExternCrateSource};
   6 use crate::middle::region;
   7 use crate::ty::{self, DefIdTree, ParamConst, Ty, TyCtxt, TypeFoldable};
   8 use crate::ty::subst::{Kind, Subst, UnpackedKind};
   9 use crate::mir::interpret::ConstValue;
  10 use syntax::symbol::{keywords, Symbol};
  11
  12 use rustc_target::spec::abi::Abi;
  13 use syntax::symbol::InternedString;
  14
  15 use std::cell::Cell;
  16 use std::fmt::{self, Write as _};
  17 use std::ops::{Deref, DerefMut};
  18
  19 // `pretty` is a separate module only for organization.
  20 use super::*;
  21
  22 macro_rules! p {
  23     (@write($($data:expr),+)) => {
  24         write!(scoped_cx!(), $($data),+)?
  25     };
  26     (@print($x:expr)) => {
  27         scoped_cx!() = $x.print(scoped_cx!())?
  28     };
  29     (@$method:ident($($arg:expr),*)) => {
  30         scoped_cx!() = scoped_cx!().$method($($arg),*)?
  31     };
  32     ($($kind:ident $data:tt),+) => {{
  33         $(p!(@$kind $data);)+
  34     }};
  35 }
  36 macro_rules! define_scoped_cx {
  37     ($cx:ident) => {
  38         #[allow(unused_macros)]
  39         macro_rules! scoped_cx {
  40             () => ($cx)
  41         }
  42     };
  43 }
  44
  45 thread_local! {
  46     static FORCE_IMPL_FILENAME_LINE: Cell<bool> = Cell::new(false);
  47     static SHOULD_PREFIX_WITH_CRATE: Cell<bool> = Cell::new(false);
  48 }
  49
  50 /// Force us to name impls with just the filename/line number. We
  51 /// normally try to use types. But at some points, notably while printing
  52 /// cycle errors, this can result in extra or suboptimal error output,
  53 /// so this variable disables that check.
  54 pub fn with_forced_impl_filename_line<F: FnOnce() -> R, R>(f: F) -> R {
  55     FORCE_IMPL_FILENAME_LINE.with(|force| {
  56         let old = force.get();
  57         force.set(true);
  58         let result = f();
  59         force.set(old);
  60         result
  61     })
  62 }
  63
  64 /// Adds the `crate::` prefix to paths where appropriate.
  65 pub fn with_crate_prefix<F: FnOnce() -> R, R>(f: F) -> R {
  66     SHOULD_PREFIX_WITH_CRATE.with(|flag| {
  67         let old = flag.get();
  68         flag.set(true);
  69         let result = f();
  70         flag.set(old);
  71         result
  72     })
  73 }
  74
  75 /// The "region highlights" are used to control region printing during
  76 /// specific error messages. When a "region highlight" is enabled, it
  77 /// gives an alternate way to print specific regions. For now, we
  78 /// always print those regions using a number, so something like "`'0`".
  79 ///
  80 /// Regions not selected by the region highlight mode are presently
  81 /// unaffected.
  82 #[derive(Copy, Clone, Default)]
  83 pub struct RegionHighlightMode {
  84     /// If enabled, when we see the selected region, use "`'N`"
  85     /// instead of the ordinary behavior.
  86     highlight_regions: [Option<(ty::RegionKind, usize)>; 3],
  87
  88     /// If enabled, when printing a "free region" that originated from
  89     /// the given `ty::BoundRegion`, print it as "`'1`". Free regions that would ordinarily
  90     /// have names print as normal.
  91     ///
  92     /// This is used when you have a signature like `fn foo(x: &u32,
  93     /// y: &'a u32)` and we want to give a name to the region of the
  94     /// reference `x`.
  95     highlight_bound_region: Option<(ty::BoundRegion, usize)>,
  96 }
  97
  98 impl RegionHighlightMode {
  99     /// If `region` and `number` are both `Some`, invokes
 100     /// `highlighting_region`.
 101     pub fn maybe_highlighting_region(
 102         &mut self,
 103         region: Option<ty::Region<'_>>,
 104         number: Option<usize>,
 105     ) {
 106         if let Some(k) = region {
 107             if let Some(n) = number {
 108                 self.highlighting_region(k, n);
 109             }
 110         }
 111     }
 112
 113     /// Highlights the region inference variable `vid` as `'N`.
 114     pub fn highlighting_region(
 115         &mut self,
 116         region: ty::Region<'_>,
 117         number: usize,
 118     ) {
 119         let num_slots = self.highlight_regions.len();
 120         let first_avail_slot = self.highlight_regions.iter_mut()
 121             .filter(|s| s.is_none())
 122             .next()
 123             .unwrap_or_else(|| {
 124                 bug!(
 125                     "can only highlight {} placeholders at a time",
 126                     num_slots,
 127                 )
 128             });
 129         *first_avail_slot = Some((*region, number));
 130     }
 131
 132     /// Convenience wrapper for `highlighting_region`.
 133     pub fn highlighting_region_vid(
 134         &mut self,
 135         vid: ty::RegionVid,
 136         number: usize,
 137     ) {
 138         self.highlighting_region(&ty::ReVar(vid), number)
 139     }
 140
 141     /// Returns `Some(n)` with the number to use for the given region, if any.
 142     fn region_highlighted(&self, region: ty::Region<'_>) -> Option<usize> {
 143         self
 144             .highlight_regions
 145             .iter()
 146             .filter_map(|h| match h {
 147                 Some((r, n)) if r == region => Some(*n),
 148                 _ => None,
 149             })
 150             .next()
 151     }
 152
 153     /// Highlight the given bound region.
 154     /// We can only highlight one bound region at a time. See
 155     /// the field `highlight_bound_region` for more detailed notes.
 156     pub fn highlighting_bound_region(
 157         &mut self,
 158         br: ty::BoundRegion,
 159         number: usize,
 160     ) {
 161         assert!(self.highlight_bound_region.is_none());
 162         self.highlight_bound_region = Some((br, number));
 163     }
 164 }
 165
 166 /// Trait for printers that pretty-print using `fmt::Write` to the printer.
 167 pub trait PrettyPrinter<'gcx: 'tcx, 'tcx>:
 168     Printer<'gcx, 'tcx,
 169         Error = fmt::Error,
 170         Path = Self,
 171         Region = Self,
 172         Type = Self,
 173         DynExistential = Self,
 174     > +
 175     fmt::Write
 176 {
 177     /// Like `print_def_path` but for value paths.
 178     fn print_value_path(
 179         self,
 180         def_id: DefId,
 181         substs: &'tcx [Kind<'tcx>],
 182     ) -> Result<Self::Path, Self::Error> {
 183         self.print_def_path(def_id, substs)
 184     }
 185
 186     fn in_binder<T>(
 187         self,
 188         value: &ty::Binder<T>,
 189     ) -> Result<Self, Self::Error>
 190         where T: Print<'gcx, 'tcx, Self, Output = Self, Error = Self::Error> + TypeFoldable<'tcx>
 191     {
 192         value.skip_binder().print(self)
 193     }
 194
 195     /// Print comma-separated elements.
 196     fn comma_sep<T>(
 197         mut self,
 198         mut elems: impl Iterator<Item = T>,
 199     ) -> Result<Self, Self::Error>
 200         where T: Print<'gcx, 'tcx, Self, Output = Self, Error = Self::Error>
 201     {
 202         if let Some(first) = elems.next() {
 203             self = first.print(self)?;
 204             for elem in elems {
 205                 self.write_str(", ")?;
 206                 self = elem.print(self)?;
 207             }
 208         }
 209         Ok(self)
 210     }
 211
 212     /// Print `<...>` around what `f` prints.
 213     fn generic_delimiters(
 214         self,
 215         f: impl FnOnce(Self) -> Result<Self, Self::Error>,
 216     ) -> Result<Self, Self::Error>;
 217
 218     /// Return `true` if the region should be printed in
 219     /// optional positions, e.g. `&'a T` or `dyn Tr + 'b`.
 220     /// This is typically the case for all non-`'_` regions.
 221     fn region_should_not_be_omitted(
 222         &self,
 223         region: ty::Region<'_>,
 224     ) -> bool;
 225
 226     // Defaults (should not be overriden):
 227
 228     /// If possible, this returns a global path resolving to `def_id` that is visible
 229     /// from at least one local module and returns true. If the crate defining `def_id` is
 230     /// declared with an `extern crate`, the path is guaranteed to use the `extern crate`.
 231     fn try_print_visible_def_path(
 232         mut self,
 233         def_id: DefId,
 234     ) -> Result<(Self, bool), Self::Error> {
 235         define_scoped_cx!(self);
 236
 237         debug!("try_print_visible_def_path: def_id={:?}", def_id);
 238
 239         // If `def_id` is a direct or injected extern crate, return the
 240         // path to the crate followed by the path to the item within the crate.
 241         if def_id.index == CRATE_DEF_INDEX {
 242             let cnum = def_id.krate;
 243
 244             if cnum == LOCAL_CRATE {
 245                 return Ok((self.path_crate(cnum)?, true));
 246             }
 247
 248             // In local mode, when we encounter a crate other than
 249             // LOCAL_CRATE, execution proceeds in one of two ways:
 250             //
 251             // 1. for a direct dependency, where user added an
 252             //    `extern crate` manually, we put the `extern
 253             //    crate` as the parent. So you wind up with
 254             //    something relative to the current crate.
 255             // 2. for an extern inferred from a path or an indirect crate,
 256             //    where there is no explicit `extern crate`, we just prepend
 257             //    the crate name.
 258             match *self.tcx().extern_crate(def_id) {
 259                 Some(ExternCrate {
 260                     src: ExternCrateSource::Extern(def_id),
 261                     direct: true,
 262                     span,
 263                     ..
 264                 }) => {
 265                     debug!("try_print_visible_def_path: def_id={:?}", def_id);
 266                     return Ok((if !span.is_dummy() {
 267                         self.print_def_path(def_id, &[])?
 268                     } else {
 269                         self.path_crate(cnum)?
 270                     }, true));
 271                 }
 272                 None => {
 273                     return Ok((self.path_crate(cnum)?, true));
 274                 }
 275                 _ => {},
 276             }
 277         }
 278
 279         if def_id.is_local() {
 280             return Ok((self, false));
 281         }
 282
 283         let visible_parent_map = self.tcx().visible_parent_map(LOCAL_CRATE);
 284
 285         let mut cur_def_key = self.tcx().def_key(def_id);
 286         debug!("try_print_visible_def_path: cur_def_key={:?}", cur_def_key);
 287
 288         // For a constructor we want the name of its parent rather than <unnamed>.
 289         match cur_def_key.disambiguated_data.data {
 290             DefPathData::Ctor => {
 291                 let parent = DefId {
 292                     krate: def_id.krate,
 293                     index: cur_def_key.parent
 294                         .expect("DefPathData::Ctor/VariantData missing a parent"),
 295                 };
 296
 297                 cur_def_key = self.tcx().def_key(parent);
 298             },
 299             _ => {},
 300         }
 301
 302         let visible_parent = match visible_parent_map.get(&def_id).cloned() {
 303             Some(parent) => parent,
 304             None => return Ok((self, false)),
 305         };
 306         // HACK(eddyb) this bypasses `path_append`'s prefix printing to avoid
 307         // knowing ahead of time whether the entire path will succeed or not.
 308         // To support printers that do not implement `PrettyPrinter`, a `Vec` or
 309         // linked list on the stack would need to be built, before any printing.
 310         match self.try_print_visible_def_path(visible_parent)? {
 311             (cx, false) => return Ok((cx, false)),
 312             (cx, true) => self = cx,
 313         }
 314         let actual_parent = self.tcx().parent(def_id);
 315         debug!(
 316             "try_print_visible_def_path: visible_parent={:?} actual_parent={:?}",
 317             visible_parent, actual_parent,
 318         );
 319
 320         let mut data = cur_def_key.disambiguated_data.data;
 321         debug!(
 322             "try_print_visible_def_path: data={:?} visible_parent={:?} actual_parent={:?}",
 323             data, visible_parent, actual_parent,
 324         );
 325
 326         match data {
 327             // In order to output a path that could actually be imported (valid and visible),
 328             // we need to handle re-exports correctly.
 329             //
 330             // For example, take `std::os::unix::process::CommandExt`, this trait is actually
 331             // defined at `std::sys::unix::ext::process::CommandExt` (at time of writing).
 332             //
 333             // `std::os::unix` rexports the contents of `std::sys::unix::ext`. `std::sys` is
 334             // private so the "true" path to `CommandExt` isn't accessible.
 335             //
 336             // In this case, the `visible_parent_map` will look something like this:
 337             //
 338             // (child) -> (parent)
 339             // `std::sys::unix::ext::process::CommandExt` -> `std::sys::unix::ext::process`
 340             // `std::sys::unix::ext::process` -> `std::sys::unix::ext`
 341             // `std::sys::unix::ext` -> `std::os`
 342             //
 343             // This is correct, as the visible parent of `std::sys::unix::ext` is in fact
 344             // `std::os`.
 345             //
 346             // When printing the path to `CommandExt` and looking at the `cur_def_key` that
 347             // corresponds to `std::sys::unix::ext`, we would normally print `ext` and then go
 348             // to the parent - resulting in a mangled path like
 349             // `std::os::ext::process::CommandExt`.
 350             //
 351             // Instead, we must detect that there was a re-export and instead print `unix`
 352             // (which is the name `std::sys::unix::ext` was re-exported as in `std::os`). To
 353             // do this, we compare the parent of `std::sys::unix::ext` (`std::sys::unix`) with
 354             // the visible parent (`std::os`). If these do not match, then we iterate over
 355             // the children of the visible parent (as was done when computing
 356             // `visible_parent_map`), looking for the specific child we currently have and then
 357             // have access to the re-exported name.
 358             DefPathData::TypeNs(ref mut name) if Some(visible_parent) != actual_parent => {
 359                 let reexport = self.tcx().item_children(visible_parent)
 360                     .iter()
 361                     .find(|child| child.res.def_id() == def_id)
 362                     .map(|child| child.ident.as_interned_str());
 363                 if let Some(reexport) = reexport {
 364                     *name = reexport;
 365                 }
 366             }
 367             // Re-exported `extern crate` (#43189).
 368             DefPathData::CrateRoot => {
 369                 data = DefPathData::TypeNs(
 370                     self.tcx().original_crate_name(def_id.krate).as_interned_str(),
 371                 );
 372             }
 373             _ => {}
 374         }
 375         debug!("try_print_visible_def_path: data={:?}", data);
 376
 377         Ok((self.path_append(Ok, &DisambiguatedDefPathData {
 378             data,
 379             disambiguator: 0,
 380         })?, true))
 381     }
 382
 383     fn pretty_path_qualified(
 384         self,
 385         self_ty: Ty<'tcx>,
 386         trait_ref: Option<ty::TraitRef<'tcx>>,
 387     ) -> Result<Self::Path, Self::Error> {
 388         if trait_ref.is_none() {
 389             // Inherent impls. Try to print `Foo::bar` for an inherent
 390             // impl on `Foo`, but fallback to `<Foo>::bar` if self-type is
 391             // anything other than a simple path.
 392             match self_ty.sty {
 393                 ty::Adt(..) | ty::Foreign(_) |
 394                 ty::Bool | ty::Char | ty::Str |
 395                 ty::Int(_) | ty::Uint(_) | ty::Float(_) => {
 396                     return self_ty.print(self);
 397                 }
 398
 399                 _ => {}
 400             }
 401         }
 402
 403         self.generic_delimiters(|mut cx| {
 404             define_scoped_cx!(cx);
 405
 406             p!(print(self_ty));
 407             if let Some(trait_ref) = trait_ref {
 408                 p!(write(" as "), print(trait_ref));
 409             }
 410             Ok(cx)
 411         })
 412     }
 413
 414     fn pretty_path_append_impl(
 415         mut self,
 416         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
 417         self_ty: Ty<'tcx>,
 418         trait_ref: Option<ty::TraitRef<'tcx>>,
 419     ) -> Result<Self::Path, Self::Error> {
 420         self = print_prefix(self)?;
 421
 422         self.generic_delimiters(|mut cx| {
 423             define_scoped_cx!(cx);
 424
 425             p!(write("impl "));
 426             if let Some(trait_ref) = trait_ref {
 427                 p!(print(trait_ref), write(" for "));
 428             }
 429             p!(print(self_ty));
 430
 431             Ok(cx)
 432         })
 433     }
 434
 435     fn pretty_print_type(
 436         mut self,
 437         ty: Ty<'tcx>,
 438     ) -> Result<Self::Type, Self::Error> {
 439         define_scoped_cx!(self);
 440
 441         match ty.sty {
 442             ty::Bool => p!(write("bool")),
 443             ty::Char => p!(write("char")),
 444             ty::Int(t) => p!(write("{}", t.ty_to_string())),
 445             ty::Uint(t) => p!(write("{}", t.ty_to_string())),
 446             ty::Float(t) => p!(write("{}", t.ty_to_string())),
 447             ty::RawPtr(ref tm) => {
 448                 p!(write("*{} ", match tm.mutbl {
 449                     hir::MutMutable => "mut",
 450                     hir::MutImmutable => "const",
 451                 }));
 452                 p!(print(tm.ty))
 453             }
 454             ty::Ref(r, ty, mutbl) => {
 455                 p!(write("&"));
 456                 if self.region_should_not_be_omitted(r) {
 457                     p!(print(r), write(" "));
 458                 }
 459                 p!(print(ty::TypeAndMut { ty, mutbl }))
 460             }
 461             ty::Never => p!(write("!")),
 462             ty::Tuple(ref tys) => {
 463                 p!(write("("));
 464                 let mut tys = tys.iter();
 465                 if let Some(&ty) = tys.next() {
 466                     p!(print(ty), write(","));
 467                     if let Some(&ty) = tys.next() {
 468                         p!(write(" "), print(ty));
 469                         for &ty in tys {
 470                             p!(write(", "), print(ty));
 471                         }
 472                     }
 473                 }
 474                 p!(write(")"))
 475             }
 476             ty::FnDef(def_id, substs) => {
 477                 let sig = self.tcx().fn_sig(def_id).subst(self.tcx(), substs);
 478                 p!(print(sig), write(" {{"), print_value_path(def_id, substs), write("}}"));
 479             }
 480             ty::FnPtr(ref bare_fn) => {
 481                 p!(print(bare_fn))
 482             }
 483             ty::Infer(infer_ty) => p!(write("{}", infer_ty)),
 484             ty::Error => p!(write("[type error]")),
 485             ty::Param(ref param_ty) => p!(write("{}", param_ty)),
 486             ty::Bound(debruijn, bound_ty) => {
 487                 match bound_ty.kind {
 488                     ty::BoundTyKind::Anon => {
 489                         if debruijn == ty::INNERMOST {
 490                             p!(write("^{}", bound_ty.var.index()))
 491                         } else {
 492                             p!(write("^{}_{}", debruijn.index(), bound_ty.var.index()))
 493                         }
 494                     }
 495
 496                     ty::BoundTyKind::Param(p) => p!(write("{}", p)),
 497                 }
 498             }
 499             ty::Adt(def, substs) => {
 500                 p!(print_def_path(def.did, substs));
 501             }
 502             ty::Dynamic(data, r) => {
 503                 let print_r = self.region_should_not_be_omitted(r);
 504                 if print_r {
 505                     p!(write("("));
 506                 }
 507                 p!(write("dyn "), print(data));
 508                 if print_r {
 509                     p!(write(" + "), print(r), write(")"));
 510                 }
 511             }
 512             ty::Foreign(def_id) => {
 513                 p!(print_def_path(def_id, &[]));
 514             }
 515             ty::Projection(ref data) => p!(print(data)),
 516             ty::UnnormalizedProjection(ref data) => {
 517                 p!(write("Unnormalized("), print(data), write(")"))
 518             }
 519             ty::Placeholder(placeholder) => {
 520                 p!(write("Placeholder({:?})", placeholder))
 521             }
 522             ty::Opaque(def_id, substs) => {
 523                 // FIXME(eddyb) print this with `print_def_path`.
 524                 if self.tcx().sess.verbose() {
 525                     p!(write("Opaque({:?}, {:?})", def_id, substs));
 526                     return Ok(self);
 527                 }
 528
 529                 let def_key = self.tcx().def_key(def_id);
 530                 if let Some(name) = def_key.disambiguated_data.data.get_opt_name() {
 531                     p!(write("{}", name));
 532                     let mut substs = substs.iter();
 533                     // FIXME(eddyb) print this with `print_def_path`.
 534                     if let Some(first) = substs.next() {
 535                         p!(write("::<"));
 536                         p!(print(first));
 537                         for subst in substs {
 538                             p!(write(", "), print(subst));
 539                         }
 540                         p!(write(">"));
 541                     }
 542                     return Ok(self);
 543                 }
 544                 // Grab the "TraitA + TraitB" from `impl TraitA + TraitB`,
 545                 // by looking up the projections associated with the def_id.
 546                 let bounds = self.tcx().predicates_of(def_id).instantiate(self.tcx(), substs);
 547
 548                 let mut first = true;
 549                 let mut is_sized = false;
 550                 p!(write("impl"));
 551                 for predicate in bounds.predicates {
 552                     if let Some(trait_ref) = predicate.to_opt_poly_trait_ref() {
 553                         // Don't print +Sized, but rather +?Sized if absent.
 554                         if Some(trait_ref.def_id()) == self.tcx().lang_items().sized_trait() {
 555                             is_sized = true;
 556                             continue;
 557                         }
 558
 559                         p!(
 560                                 write("{}", if first { " " } else { "+" }),
 561                                 print(trait_ref));
 562                         first = false;
 563                     }
 564                 }
 565                 if !is_sized {
 566                     p!(write("{}?Sized", if first { " " } else { "+" }));
 567                 } else if first {
 568                     p!(write(" Sized"));
 569                 }
 570             }
 571             ty::Str => p!(write("str")),
 572             ty::Generator(did, substs, movability) => {
 573                 let upvar_tys = substs.upvar_tys(did, self.tcx());
 574                 let witness = substs.witness(did, self.tcx());
 575                 if movability == hir::GeneratorMovability::Movable {
 576                     p!(write("[generator"));
 577                 } else {
 578                     p!(write("[static generator"));
 579                 }
 580
 581                 // FIXME(eddyb) should use `def_span`.
 582                 if let Some(hir_id) = self.tcx().hir().as_local_hir_id(did) {
 583                     p!(write("@{:?}", self.tcx().hir().span_by_hir_id(hir_id)));
 584                     let mut sep = " ";
 585                     for (freevar, upvar_ty) in self.tcx().freevars(did)
 586                         .as_ref()
 587                         .map_or(&[][..], |fv| &fv[..])
 588                         .iter()
 589                         .zip(upvar_tys)
 590                     {
 591                         p!(
 592                             write("{}{}:",
 593                                     sep,
 594                                     self.tcx().hir().name_by_hir_id(freevar.var_id())),
 595                             print(upvar_ty));
 596                         sep = ", ";
 597                     }
 598                 } else {
 599                     // cross-crate closure types should only be
 600                     // visible in codegen bug reports, I imagine.
 601                     p!(write("@{:?}", did));
 602                     let mut sep = " ";
 603                     for (index, upvar_ty) in upvar_tys.enumerate() {
 604                         p!(
 605                                 write("{}{}:", sep, index),
 606                                 print(upvar_ty));
 607                         sep = ", ";
 608                     }
 609                 }
 610
 611                 p!(write(" "), print(witness), write("]"))
 612             },
 613             ty::GeneratorWitness(types) => {
 614                 p!(in_binder(&types));
 615             }
 616             ty::Closure(did, substs) => {
 617                 let upvar_tys = substs.upvar_tys(did, self.tcx());
 618                 p!(write("[closure"));
 619
 620                 // FIXME(eddyb) should use `def_span`.
 621                 if let Some(hir_id) = self.tcx().hir().as_local_hir_id(did) {
 622                     if self.tcx().sess.opts.debugging_opts.span_free_formats {
 623                         p!(write("@{:?}", hir_id));
 624                     } else {
 625                         p!(write("@{:?}", self.tcx().hir().span_by_hir_id(hir_id)));
 626                     }
 627                     let mut sep = " ";
 628                     for (freevar, upvar_ty) in self.tcx().freevars(did)
 629                         .as_ref()
 630                         .map_or(&[][..], |fv| &fv[..])
 631                         .iter()
 632                         .zip(upvar_tys)
 633                     {
 634                         p!(
 635                             write("{}{}:",
 636                                     sep,
 637                                     self.tcx().hir().name_by_hir_id(freevar.var_id())),
 638                             print(upvar_ty));
 639                         sep = ", ";
 640                     }
 641                 } else {
 642                     // cross-crate closure types should only be
 643                     // visible in codegen bug reports, I imagine.
 644                     p!(write("@{:?}", did));
 645                     let mut sep = " ";
 646                     for (index, upvar_ty) in upvar_tys.enumerate() {
 647                         p!(
 648                                 write("{}{}:", sep, index),
 649                                 print(upvar_ty));
 650                         sep = ", ";
 651                     }
 652                 }
 653
 654                 if self.tcx().sess.verbose() {
 655                     p!(write(
 656                         " closure_kind_ty={:?} closure_sig_ty={:?}",
 657                         substs.closure_kind_ty(did, self.tcx()),
 658                         substs.closure_sig_ty(did, self.tcx())
 659                     ));
 660                 }
 661
 662                 p!(write("]"))
 663             },
 664             ty::Array(ty, sz) => {
 665                 p!(write("["), print(ty), write("; "));
 666                 match sz.val {
 667                     ConstValue::Unevaluated(..) |
 668                     ConstValue::Infer(..) => p!(write("_")),
 669                     ConstValue::Param(ParamConst { name, .. }) =>
 670                         p!(write("{}", name)),
 671                     _ => p!(write("{}", sz.unwrap_usize(self.tcx()))),
 672                 }
 673                 p!(write("]"))
 674             }
 675             ty::Slice(ty) => {
 676                 p!(write("["), print(ty), write("]"))
 677             }
 678         }
 679
 680         Ok(self)
 681     }
 682
 683     fn pretty_print_dyn_existential(
 684         mut self,
 685         predicates: &'tcx ty::List<ty::ExistentialPredicate<'tcx>>,
 686     ) -> Result<Self::DynExistential, Self::Error> {
 687         define_scoped_cx!(self);
 688
 689         // Generate the main trait ref, including associated types.
 690         let mut first = true;
 691
 692         if let Some(principal) = predicates.principal() {
 693             p!(print_def_path(principal.def_id, &[]));
 694
 695             let mut resugared = false;
 696
 697             // Special-case `Fn(...) -> ...` and resugar it.
 698             let fn_trait_kind = self.tcx().lang_items().fn_trait_kind(principal.def_id);
 699             if !self.tcx().sess.verbose() && fn_trait_kind.is_some() {
 700                 if let ty::Tuple(ref args) = principal.substs.type_at(0).sty {
 701                     let mut projections = predicates.projection_bounds();
 702                     if let (Some(proj), None) = (projections.next(), projections.next()) {
 703                         let tys: Vec<_> = args.iter().map(|k| k.expect_ty()).collect();
 704                         p!(pretty_fn_sig(&tys, false, proj.ty));
 705                         resugared = true;
 706                     }
 707                 }
 708             }
 709
 710             // HACK(eddyb) this duplicates `FmtPrinter`'s `path_generic_args`,
 711             // in order to place the projections inside the `<...>`.
 712             if !resugared {
 713                 // Use a type that can't appear in defaults of type parameters.
 714                 let dummy_self = self.tcx().mk_ty_infer(ty::FreshTy(0));
 715                 let principal = principal.with_self_ty(self.tcx(), dummy_self);
 716
 717                 let args = self.generic_args_to_print(
 718                     self.tcx().generics_of(principal.def_id),
 719                     principal.substs,
 720                 );
 721
 722                 // Don't print `'_` if there's no unerased regions.
 723                 let print_regions = args.iter().any(|arg| {
 724                     match arg.unpack() {
 725                         UnpackedKind::Lifetime(r) => *r != ty::ReErased,
 726                         _ => false,
 727                     }
 728                 });
 729                 let mut args = args.iter().cloned().filter(|arg| {
 730                     match arg.unpack() {
 731                         UnpackedKind::Lifetime(_) => print_regions,
 732                         _ => true,
 733                     }
 734                 });
 735                 let mut projections = predicates.projection_bounds();
 736
 737                 let arg0 = args.next();
 738                 let projection0 = projections.next();
 739                 if arg0.is_some() || projection0.is_some() {
 740                     let args = arg0.into_iter().chain(args);
 741                     let projections = projection0.into_iter().chain(projections);
 742
 743                     p!(generic_delimiters(|mut cx| {
 744                         cx = cx.comma_sep(args)?;
 745                         if arg0.is_some() && projection0.is_some() {
 746                             write!(cx, ", ")?;
 747                         }
 748                         cx.comma_sep(projections)
 749                     }));
 750                 }
 751             }
 752             first = false;
 753         }
 754
 755         // Builtin bounds.
 756         // FIXME(eddyb) avoid printing twice (needed to ensure
 757         // that the auto traits are sorted *and* printed via cx).
 758         let mut auto_traits: Vec<_> = predicates.auto_traits().map(|did| {
 759             (self.tcx().def_path_str(did), did)
 760         }).collect();
 761
 762         // The auto traits come ordered by `DefPathHash`. While
 763         // `DefPathHash` is *stable* in the sense that it depends on
 764         // neither the host nor the phase of the moon, it depends
 765         // "pseudorandomly" on the compiler version and the target.
 766         //
 767         // To avoid that causing instabilities in compiletest
 768         // output, sort the auto-traits alphabetically.
 769         auto_traits.sort();
 770
 771         for (_, def_id) in auto_traits {
 772             if !first {
 773                 p!(write(" + "));
 774             }
 775             first = false;
 776
 777             p!(print_def_path(def_id, &[]));
 778         }
 779
 780         Ok(self)
 781     }
 782
 783     fn pretty_fn_sig(
 784         mut self,
 785         inputs: &[Ty<'tcx>],
 786         c_variadic: bool,
 787         output: Ty<'tcx>,
 788     ) -> Result<Self, Self::Error> {
 789         define_scoped_cx!(self);
 790
 791         p!(write("("));
 792         let mut inputs = inputs.iter();
 793         if let Some(&ty) = inputs.next() {
 794             p!(print(ty));
 795             for &ty in inputs {
 796                 p!(write(", "), print(ty));
 797             }
 798             if c_variadic {
 799                 p!(write(", ..."));
 800             }
 801         }
 802         p!(write(")"));
 803         if !output.is_unit() {
 804             p!(write(" -> "), print(output));
 805         }
 806
 807         Ok(self)
 808     }
 809 }
 810
 811 // HACK(eddyb) boxed to avoid moving around a large struct by-value.
 812 pub struct FmtPrinter<'a, 'gcx, 'tcx, F>(Box<FmtPrinterData<'a, 'gcx, 'tcx, F>>);
 813
 814 pub struct FmtPrinterData<'a, 'gcx, 'tcx, F> {
 815     tcx: TyCtxt<'a, 'gcx, 'tcx>,
 816     fmt: F,
 817
 818     empty_path: bool,
 819     in_value: bool,
 820
 821     used_region_names: FxHashSet<InternedString>,
 822     region_index: usize,
 823     binder_depth: usize,
 824
 825     pub region_highlight_mode: RegionHighlightMode,
 826 }
 827
 828 impl<F> Deref for FmtPrinter<'a, 'gcx, 'tcx, F> {
 829     type Target = FmtPrinterData<'a, 'gcx, 'tcx, F>;
 830     fn deref(&self) -> &Self::Target {
 831         &self.0
 832     }
 833 }
 834
 835 impl<F> DerefMut for FmtPrinter<'_, '_, '_, F> {
 836     fn deref_mut(&mut self) -> &mut Self::Target {
 837         &mut self.0
 838     }
 839 }
 840
 841 impl<F> FmtPrinter<'a, 'gcx, 'tcx, F> {
 842     pub fn new(tcx: TyCtxt<'a, 'gcx, 'tcx>, fmt: F, ns: Namespace) -> Self {
 843         FmtPrinter(Box::new(FmtPrinterData {
 844             tcx,
 845             fmt,
 846             empty_path: false,
 847             in_value: ns == Namespace::ValueNS,
 848             used_region_names: Default::default(),
 849             region_index: 0,
 850             binder_depth: 0,
 851             region_highlight_mode: RegionHighlightMode::default(),
 852         }))
 853     }
 854 }
 855
 856 impl TyCtxt<'_, '_, '_> {
 857     // HACK(eddyb) get rid of `def_path_str` and/or pass `Namespace` explicitly always
 858     // (but also some things just print a `DefId` generally so maybe we need this?)
 859     fn guess_def_namespace(self, def_id: DefId) -> Namespace {
 860         match self.def_key(def_id).disambiguated_data.data {
 861             DefPathData::ValueNs(..) |
 862             DefPathData::Field(..) |
 863             DefPathData::AnonConst |
 864             DefPathData::ConstParam(..) |
 865             DefPathData::ClosureExpr |
 866             DefPathData::Ctor => Namespace::ValueNS,
 867
 868             DefPathData::MacroDef(..) => Namespace::MacroNS,
 869
 870             _ => Namespace::TypeNS,
 871         }
 872     }
 873
 874     /// Returns a string identifying this `DefId`. This string is
 875     /// suitable for user output.
 876     pub fn def_path_str(self, def_id: DefId) -> String {
 877         let ns = self.guess_def_namespace(def_id);
 878         debug!("def_path_str: def_id={:?}, ns={:?}", def_id, ns);
 879         let mut s = String::new();
 880         let _ = FmtPrinter::new(self, &mut s, ns)
 881             .print_def_path(def_id, &[]);
 882         s
 883     }
 884 }
 885
 886 impl<F: fmt::Write> fmt::Write for FmtPrinter<'_, '_, '_, F> {
 887     fn write_str(&mut self, s: &str) -> fmt::Result {
 888         self.fmt.write_str(s)
 889     }
 890 }
 891
 892 impl<F: fmt::Write> Printer<'gcx, 'tcx> for FmtPrinter<'_, 'gcx, 'tcx, F> {
 893     type Error = fmt::Error;
 894
 895     type Path = Self;
 896     type Region = Self;
 897     type Type = Self;
 898     type DynExistential = Self;
 899
 900     fn tcx(&'a self) -> TyCtxt<'a, 'gcx, 'tcx> {
 901         self.tcx
 902     }
 903
 904     fn print_def_path(
 905         mut self,
 906         def_id: DefId,
 907         substs: &'tcx [Kind<'tcx>],
 908     ) -> Result<Self::Path, Self::Error> {
 909         define_scoped_cx!(self);
 910
 911         if substs.is_empty() {
 912             match self.try_print_visible_def_path(def_id)? {
 913                 (cx, true) => return Ok(cx),
 914                 (cx, false) => self = cx,
 915             }
 916         }
 917
 918         let key = self.tcx.def_key(def_id);
 919         if let DefPathData::Impl = key.disambiguated_data.data {
 920             // Always use types for non-local impls, where types are always
 921             // available, and filename/line-number is mostly uninteresting.
 922             let use_types =
 923                 !def_id.is_local() || {
 924                     // Otherwise, use filename/line-number if forced.
 925                     let force_no_types = FORCE_IMPL_FILENAME_LINE.with(|f| f.get());
 926                     !force_no_types
 927                 };
 928
 929             if !use_types {
 930                 // If no type info is available, fall back to
 931                 // pretty printing some span information. This should
 932                 // only occur very early in the compiler pipeline.
 933                 let parent_def_id = DefId { index: key.parent.unwrap(), ..def_id };
 934                 let span = self.tcx.def_span(def_id);
 935
 936                 self = self.print_def_path(parent_def_id, &[])?;
 937
 938                 // HACK(eddyb) copy of `path_append` to avoid
 939                 // constructing a `DisambiguatedDefPathData`.
 940                 if !self.empty_path {
 941                     write!(self, "::")?;
 942                 }
 943                 write!(self, "<impl at {:?}>", span)?;
 944                 self.empty_path = false;
 945
 946                 return Ok(self);
 947             }
 948         }
 949
 950         self.default_print_def_path(def_id, substs)
 951     }
 952
 953     fn print_region(
 954         self,
 955         region: ty::Region<'_>,
 956     ) -> Result<Self::Region, Self::Error> {
 957         self.pretty_print_region(region)
 958     }
 959
 960     fn print_type(
 961         self,
 962         ty: Ty<'tcx>,
 963     ) -> Result<Self::Type, Self::Error> {
 964         self.pretty_print_type(ty)
 965     }
 966
 967     fn print_dyn_existential(
 968         self,
 969         predicates: &'tcx ty::List<ty::ExistentialPredicate<'tcx>>,
 970     ) -> Result<Self::DynExistential, Self::Error> {
 971         self.pretty_print_dyn_existential(predicates)
 972     }
 973
 974     fn path_crate(
 975         mut self,
 976         cnum: CrateNum,
 977     ) -> Result<Self::Path, Self::Error> {
 978         self.empty_path = true;
 979         if cnum == LOCAL_CRATE {
 980             if self.tcx.sess.rust_2018() {
 981                 // We add the `crate::` keyword on Rust 2018, only when desired.
 982                 if SHOULD_PREFIX_WITH_CRATE.with(|flag| flag.get()) {
 983                     write!(self, "{}", keywords::Crate.name())?;
 984                     self.empty_path = false;
 985                 }
 986             }
 987         } else {
 988             write!(self, "{}", self.tcx.crate_name(cnum))?;
 989             self.empty_path = false;
 990         }
 991         Ok(self)
 992     }
 993     fn path_qualified(
 994         mut self,
 995         self_ty: Ty<'tcx>,
 996         trait_ref: Option<ty::TraitRef<'tcx>>,
 997     ) -> Result<Self::Path, Self::Error> {
 998         self = self.pretty_path_qualified(self_ty, trait_ref)?;
 999         self.empty_path = false;
1000         Ok(self)
1001     }
1002
1003     fn path_append_impl(
1004         mut self,
1005         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1006         _disambiguated_data: &DisambiguatedDefPathData,
1007         self_ty: Ty<'tcx>,
1008         trait_ref: Option<ty::TraitRef<'tcx>>,
1009     ) -> Result<Self::Path, Self::Error> {
1010         self = self.pretty_path_append_impl(|mut cx| {
1011             cx = print_prefix(cx)?;
1012             if !cx.empty_path {
1013                 write!(cx, "::")?;
1014             }
1015
1016             Ok(cx)
1017         }, self_ty, trait_ref)?;
1018         self.empty_path = false;
1019         Ok(self)
1020     }
1021     fn path_append(
1022         mut self,
1023         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1024         disambiguated_data: &DisambiguatedDefPathData,
1025     ) -> Result<Self::Path, Self::Error> {
1026         self = print_prefix(self)?;
1027
1028         // Skip `::{{constructor}}` on tuple/unit structs.
1029         match disambiguated_data.data {
1030             DefPathData::Ctor => return Ok(self),
1031             _ => {}
1032         }
1033
1034         // FIXME(eddyb) `name` should never be empty, but it
1035         // currently is for `extern { ... }` "foreign modules".
1036         let name = disambiguated_data.data.as_interned_str().as_str();
1037         if !name.is_empty() {
1038             if !self.empty_path {
1039                 write!(self, "::")?;
1040             }
1041             write!(self, "{}", name)?;
1042
1043             // FIXME(eddyb) this will print e.g. `{{closure}}#3`, but it
1044             // might be nicer to use something else, e.g. `{closure#3}`.
1045             let dis = disambiguated_data.disambiguator;
1046             let print_dis =
1047                 disambiguated_data.data.get_opt_name().is_none() ||
1048                 dis != 0 && self.tcx.sess.verbose();
1049             if print_dis {
1050                 write!(self, "#{}", dis)?;
1051             }
1052
1053             self.empty_path = false;
1054         }
1055
1056         Ok(self)
1057     }
1058     fn path_generic_args(
1059         mut self,
1060         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1061         args: &[Kind<'tcx>],
1062     ) -> Result<Self::Path, Self::Error> {
1063         self = print_prefix(self)?;
1064
1065         // Don't print `'_` if there's no unerased regions.
1066         let print_regions = args.iter().any(|arg| {
1067             match arg.unpack() {
1068                 UnpackedKind::Lifetime(r) => *r != ty::ReErased,
1069                 _ => false,
1070             }
1071         });
1072         let args = args.iter().cloned().filter(|arg| {
1073             match arg.unpack() {
1074                 UnpackedKind::Lifetime(_) => print_regions,
1075                 _ => true,
1076             }
1077         });
1078
1079         if args.clone().next().is_some() {
1080             if self.in_value {
1081                 write!(self, "::")?;
1082             }
1083             self.generic_delimiters(|cx| cx.comma_sep(args))
1084         } else {
1085             Ok(self)
1086         }
1087     }
1088 }
1089
1090 impl<F: fmt::Write> PrettyPrinter<'gcx, 'tcx> for FmtPrinter<'_, 'gcx, 'tcx, F> {
1091     fn print_value_path(
1092         mut self,
1093         def_id: DefId,
1094         substs: &'tcx [Kind<'tcx>],
1095     ) -> Result<Self::Path, Self::Error> {
1096         let was_in_value = std::mem::replace(&mut self.in_value, true);
1097         self = self.print_def_path(def_id, substs)?;
1098         self.in_value = was_in_value;
1099
1100         Ok(self)
1101     }
1102
1103     fn in_binder<T>(
1104         self,
1105         value: &ty::Binder<T>,
1106     ) -> Result<Self, Self::Error>
1107         where T: Print<'gcx, 'tcx, Self, Output = Self, Error = Self::Error> + TypeFoldable<'tcx>
1108     {
1109         self.pretty_in_binder(value)
1110     }
1111
1112     fn generic_delimiters(
1113         mut self,
1114         f: impl FnOnce(Self) -> Result<Self, Self::Error>,
1115     ) -> Result<Self, Self::Error> {
1116         write!(self, "<")?;
1117
1118         let was_in_value = std::mem::replace(&mut self.in_value, false);
1119         let mut inner = f(self)?;
1120         inner.in_value = was_in_value;
1121
1122         write!(inner, ">")?;
1123         Ok(inner)
1124     }
1125
1126     fn region_should_not_be_omitted(
1127         &self,
1128         region: ty::Region<'_>,
1129     ) -> bool {
1130         let highlight = self.region_highlight_mode;
1131         if highlight.region_highlighted(region).is_some() {
1132             return true;
1133         }
1134
1135         if self.tcx.sess.verbose() {
1136             return true;
1137         }
1138
1139         let identify_regions = self.tcx.sess.opts.debugging_opts.identify_regions;
1140
1141         match *region {
1142             ty::ReEarlyBound(ref data) => {
1143                 data.name != "" && data.name != "'_"
1144             }
1145
1146             ty::ReLateBound(_, br) |
1147             ty::ReFree(ty::FreeRegion { bound_region: br, .. }) |
1148             ty::RePlaceholder(ty::Placeholder { name: br, .. }) => {
1149                 if let ty::BrNamed(_, name) = br {
1150                     if name != "" && name != "'_" {
1151                         return true;
1152                     }
1153                 }
1154
1155                 if let Some((region, _)) = highlight.highlight_bound_region {
1156                     if br == region {
1157                         return true;
1158                     }
1159                 }
1160
1161                 false
1162             }
1163
1164             ty::ReScope(_) |
1165             ty::ReVar(_) if identify_regions => true,
1166
1167             ty::ReVar(_) |
1168             ty::ReScope(_) |
1169             ty::ReErased => false,
1170
1171             ty::ReStatic |
1172             ty::ReEmpty |
1173             ty::ReClosureBound(_) => true,
1174         }
1175     }
1176 }
1177
1178 // HACK(eddyb) limited to `FmtPrinter` because of `region_highlight_mode`.
1179 impl<F: fmt::Write> FmtPrinter<'_, '_, '_, F> {
1180     pub fn pretty_print_region(
1181         mut self,
1182         region: ty::Region<'_>,
1183     ) -> Result<Self, fmt::Error> {
1184         define_scoped_cx!(self);
1185
1186         // Watch out for region highlights.
1187         let highlight = self.region_highlight_mode;
1188         if let Some(n) = highlight.region_highlighted(region) {
1189             p!(write("'{}", n));
1190             return Ok(self);
1191         }
1192
1193         if self.tcx.sess.verbose() {
1194             p!(write("{:?}", region));
1195             return Ok(self);
1196         }
1197
1198         let identify_regions = self.tcx.sess.opts.debugging_opts.identify_regions;
1199
1200         // These printouts are concise.  They do not contain all the information
1201         // the user might want to diagnose an error, but there is basically no way
1202         // to fit that into a short string.  Hence the recommendation to use
1203         // `explain_region()` or `note_and_explain_region()`.
1204         match *region {
1205             ty::ReEarlyBound(ref data) => {
1206                 if data.name != "" {
1207                     p!(write("{}", data.name));
1208                     return Ok(self);
1209                 }
1210             }
1211             ty::ReLateBound(_, br) |
1212             ty::ReFree(ty::FreeRegion { bound_region: br, .. }) |
1213             ty::RePlaceholder(ty::Placeholder { name: br, .. }) => {
1214                 if let ty::BrNamed(_, name) = br {
1215                     if name != "" && name != "'_" {
1216                         p!(write("{}", name));
1217                         return Ok(self);
1218                     }
1219                 }
1220
1221                 if let Some((region, counter)) = highlight.highlight_bound_region {
1222                     if br == region {
1223                         p!(write("'{}", counter));
1224                         return Ok(self);
1225                     }
1226                 }
1227             }
1228             ty::ReScope(scope) if identify_regions => {
1229                 match scope.data {
1230                     region::ScopeData::Node =>
1231                         p!(write("'{}s", scope.item_local_id().as_usize())),
1232                     region::ScopeData::CallSite =>
1233                         p!(write("'{}cs", scope.item_local_id().as_usize())),
1234                     region::ScopeData::Arguments =>
1235                         p!(write("'{}as", scope.item_local_id().as_usize())),
1236                     region::ScopeData::Destruction =>
1237                         p!(write("'{}ds", scope.item_local_id().as_usize())),
1238                     region::ScopeData::Remainder(first_statement_index) => p!(write(
1239                         "'{}_{}rs",
1240                         scope.item_local_id().as_usize(),
1241                         first_statement_index.index()
1242                     )),
1243                 }
1244                 return Ok(self);
1245             }
1246             ty::ReVar(region_vid) if identify_regions => {
1247                 p!(write("{:?}", region_vid));
1248                 return Ok(self);
1249             }
1250             ty::ReVar(_) => {}
1251             ty::ReScope(_) |
1252             ty::ReErased => {}
1253             ty::ReStatic => {
1254                 p!(write("'static"));
1255                 return Ok(self);
1256             }
1257             ty::ReEmpty => {
1258                 p!(write("'<empty>"));
1259                 return Ok(self);
1260             }
1261
1262             // The user should never encounter these in unsubstituted form.
1263             ty::ReClosureBound(vid) => {
1264                 p!(write("{:?}", vid));
1265                 return Ok(self);
1266             }
1267         }
1268
1269         p!(write("'_"));
1270
1271         Ok(self)
1272     }
1273 }
1274
1275 // HACK(eddyb) limited to `FmtPrinter` because of `binder_depth`,
1276 // `region_index` and `used_region_names`.
1277 impl<F: fmt::Write> FmtPrinter<'_, 'gcx, 'tcx, F> {
1278     pub fn pretty_in_binder<T>(
1279         mut self,
1280         value: &ty::Binder<T>,
1281     ) -> Result<Self, fmt::Error>
1282         where T: Print<'gcx, 'tcx, Self, Output = Self, Error = fmt::Error> + TypeFoldable<'tcx>
1283     {
1284         fn name_by_region_index(index: usize) -> InternedString {
1285             match index {
1286                 0 => Symbol::intern("'r"),
1287                 1 => Symbol::intern("'s"),
1288                 i => Symbol::intern(&format!("'t{}", i-2)),
1289             }.as_interned_str()
1290         }
1291
1292         // Replace any anonymous late-bound regions with named
1293         // variants, using gensym'd identifiers, so that we can
1294         // clearly differentiate between named and unnamed regions in
1295         // the output. We'll probably want to tweak this over time to
1296         // decide just how much information to give.
1297         if self.binder_depth == 0 {
1298             self.prepare_late_bound_region_info(value);
1299         }
1300
1301         let mut empty = true;
1302         let mut start_or_continue = |cx: &mut Self, start: &str, cont: &str| {
1303             write!(cx, "{}", if empty {
1304                 empty = false;
1305                 start
1306             } else {
1307                 cont
1308             })
1309         };
1310
1311         define_scoped_cx!(self);
1312
1313         let old_region_index = self.region_index;
1314         let mut region_index = old_region_index;
1315         let new_value = self.tcx.replace_late_bound_regions(value, |br| {
1316             let _ = start_or_continue(&mut self, "for<", ", ");
1317             let br = match br {
1318                 ty::BrNamed(_, name) => {
1319                     let _ = write!(self, "{}", name);
1320                     br
1321                 }
1322                 ty::BrAnon(_) |
1323                 ty::BrFresh(_) |
1324                 ty::BrEnv => {
1325                     let name = loop {
1326                         let name = name_by_region_index(region_index);
1327                         region_index += 1;
1328                         if !self.used_region_names.contains(&name) {
1329                             break name;
1330                         }
1331                     };
1332                     let _ = write!(self, "{}", name);
1333                     ty::BrNamed(DefId::local(CRATE_DEF_INDEX), name)
1334                 }
1335             };
1336             self.tcx.mk_region(ty::ReLateBound(ty::INNERMOST, br))
1337         }).0;
1338         start_or_continue(&mut self, "", "> ")?;
1339
1340         self.binder_depth += 1;
1341         self.region_index = region_index;
1342         let mut inner = new_value.print(self)?;
1343         inner.region_index = old_region_index;
1344         inner.binder_depth -= 1;
1345         Ok(inner)
1346     }
1347
1348     fn prepare_late_bound_region_info<T>(&mut self, value: &ty::Binder<T>)
1349         where T: TypeFoldable<'tcx>
1350     {
1351
1352         struct LateBoundRegionNameCollector<'a>(&'a mut FxHashSet<InternedString>);
1353         impl<'tcx> ty::fold::TypeVisitor<'tcx> for LateBoundRegionNameCollector<'_> {
1354             fn visit_region(&mut self, r: ty::Region<'tcx>) -> bool {
1355                 match *r {
1356                     ty::ReLateBound(_, ty::BrNamed(_, name)) => {
1357                         self.0.insert(name);
1358                     },
1359                     _ => {},
1360                 }
1361                 r.super_visit_with(self)
1362             }
1363         }
1364
1365         self.used_region_names.clear();
1366         let mut collector = LateBoundRegionNameCollector(&mut self.used_region_names);
1367         value.visit_with(&mut collector);
1368         self.region_index = 0;
1369     }
1370 }
1371
1372 impl<'gcx: 'tcx, 'tcx, T, P: PrettyPrinter<'gcx, 'tcx>> Print<'gcx, 'tcx, P>
1373     for ty::Binder<T>
1374     where T: Print<'gcx, 'tcx, P, Output = P, Error = P::Error> + TypeFoldable<'tcx>
1375 {
1376     type Output = P;
1377     type Error = P::Error;
1378     fn print(&self, cx: P) -> Result<Self::Output, Self::Error> {
1379         cx.in_binder(self)
1380     }
1381 }
1382
1383 impl<'gcx: 'tcx, 'tcx, T, U, P: PrettyPrinter<'gcx, 'tcx>> Print<'gcx, 'tcx, P>
1384     for ty::OutlivesPredicate<T, U>
1385     where T: Print<'gcx, 'tcx, P, Output = P, Error = P::Error>,
1386           U: Print<'gcx, 'tcx, P, Output = P, Error = P::Error>,
1387 {
1388     type Output = P;
1389     type Error = P::Error;
1390     fn print(&self, mut cx: P) -> Result<Self::Output, Self::Error> {
1391         define_scoped_cx!(cx);
1392         p!(print(self.0), write(" : "), print(self.1));
1393         Ok(cx)
1394     }
1395 }
1396
1397 macro_rules! forward_display_to_print {
1398     ($($ty:ty),+) => {
1399         $(impl fmt::Display for $ty {
1400             fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1401                 ty::tls::with(|tcx| {
1402                     tcx.lift(self)
1403                         .expect("could not lift for printing")
1404                         .print(FmtPrinter::new(tcx, f, Namespace::TypeNS))?;
1405                     Ok(())
1406                 })
1407             }
1408         })+
1409     };
1410 }
1411
1412 macro_rules! define_print_and_forward_display {
1413     (($self:ident, $cx:ident): $($ty:ty $print:block)+) => {
1414         $(impl<'gcx: 'tcx, 'tcx, P: PrettyPrinter<'gcx, 'tcx>> Print<'gcx, 'tcx, P> for $ty {
1415             type Output = P;
1416             type Error = fmt::Error;
1417             fn print(&$self, $cx: P) -> Result<Self::Output, Self::Error> {
1418                 #[allow(unused_mut)]
1419                 let mut $cx = $cx;
1420                 define_scoped_cx!($cx);
1421                 let _: () = $print;
1422                 #[allow(unreachable_code)]
1423                 Ok($cx)
1424             }
1425         })+
1426
1427         forward_display_to_print!($($ty),+);
1428     };
1429 }
1430
1431 // HACK(eddyb) this is separate because `ty::RegionKind` doesn't need lifting.
1432 impl fmt::Display for ty::RegionKind {
1433     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1434         ty::tls::with(|tcx| {
1435             self.print(FmtPrinter::new(tcx, f, Namespace::TypeNS))?;
1436             Ok(())
1437         })
1438     }
1439 }
1440
1441 forward_display_to_print! {
1442     Ty<'tcx>,
1443     &'tcx ty::List<ty::ExistentialPredicate<'tcx>>,
1444
1445     // HACK(eddyb) these are exhaustive instead of generic,
1446     // because `for<'gcx: 'tcx, 'tcx>` isn't possible yet.
1447     ty::Binder<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>,
1448     ty::Binder<ty::TraitRef<'tcx>>,
1449     ty::Binder<ty::FnSig<'tcx>>,
1450     ty::Binder<ty::TraitPredicate<'tcx>>,
1451     ty::Binder<ty::SubtypePredicate<'tcx>>,
1452     ty::Binder<ty::ProjectionPredicate<'tcx>>,
1453     ty::Binder<ty::OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>>,
1454     ty::Binder<ty::OutlivesPredicate<ty::Region<'tcx>, ty::Region<'tcx>>>,
1455
1456     ty::OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>,
1457     ty::OutlivesPredicate<ty::Region<'tcx>, ty::Region<'tcx>>
1458 }
1459
1460 define_print_and_forward_display! {
1461     (self, cx):
1462
1463     &'tcx ty::List<Ty<'tcx>> {
1464         p!(write("{{"));
1465         let mut tys = self.iter();
1466         if let Some(&ty) = tys.next() {
1467             p!(print(ty));
1468             for &ty in tys {
1469                 p!(write(", "), print(ty));
1470             }
1471         }
1472         p!(write("}}"))
1473     }
1474
1475     ty::TypeAndMut<'tcx> {
1476         p!(write("{}", if self.mutbl == hir::MutMutable { "mut " } else { "" }),
1477             print(self.ty))
1478     }
1479
1480     ty::ExistentialTraitRef<'tcx> {
1481         // Use a type that can't appear in defaults of type parameters.
1482         let dummy_self = cx.tcx().mk_ty_infer(ty::FreshTy(0));
1483         let trait_ref = self.with_self_ty(cx.tcx(), dummy_self);
1484         p!(print(trait_ref))
1485     }
1486
1487     ty::ExistentialProjection<'tcx> {
1488         let name = cx.tcx().associated_item(self.item_def_id).ident;
1489         p!(write("{} = ", name), print(self.ty))
1490     }
1491
1492     ty::ExistentialPredicate<'tcx> {
1493         match *self {
1494             ty::ExistentialPredicate::Trait(x) => p!(print(x)),
1495             ty::ExistentialPredicate::Projection(x) => p!(print(x)),
1496             ty::ExistentialPredicate::AutoTrait(def_id) => {
1497                 p!(print_def_path(def_id, &[]));
1498             }
1499         }
1500     }
1501
1502     ty::FnSig<'tcx> {
1503         if self.unsafety == hir::Unsafety::Unsafe {
1504             p!(write("unsafe "));
1505         }
1506
1507         if self.abi != Abi::Rust {
1508             p!(write("extern {} ", self.abi));
1509         }
1510
1511         p!(write("fn"), pretty_fn_sig(self.inputs(), self.c_variadic, self.output()));
1512     }
1513
1514     ty::InferTy {
1515         if cx.tcx().sess.verbose() {
1516             p!(write("{:?}", self));
1517             return Ok(cx);
1518         }
1519         match *self {
1520             ty::TyVar(_) => p!(write("_")),
1521             ty::IntVar(_) => p!(write("{}", "{integer}")),
1522             ty::FloatVar(_) => p!(write("{}", "{float}")),
1523             ty::FreshTy(v) => p!(write("FreshTy({})", v)),
1524             ty::FreshIntTy(v) => p!(write("FreshIntTy({})", v)),
1525             ty::FreshFloatTy(v) => p!(write("FreshFloatTy({})", v))
1526         }
1527     }
1528
1529     ty::TraitRef<'tcx> {
1530         p!(print_def_path(self.def_id, self.substs));
1531     }
1532
1533     &'tcx ty::Const<'tcx> {
1534         match self.val {
1535             ConstValue::Unevaluated(..) |
1536             ConstValue::Infer(..) => p!(write("_")),
1537             ConstValue::Param(ParamConst { name, .. }) => p!(write("{}", name)),
1538             _ => p!(write("{:?}", self)),
1539         }
1540     }
1541
1542     ty::ParamTy {
1543         p!(write("{}", self.name))
1544     }
1545
1546     ty::ParamConst {
1547         p!(write("{}", self.name))
1548     }
1549
1550     ty::SubtypePredicate<'tcx> {
1551         p!(print(self.a), write(" <: "), print(self.b))
1552     }
1553
1554     ty::TraitPredicate<'tcx> {
1555         p!(print(self.trait_ref.self_ty()), write(": "), print(self.trait_ref))
1556     }
1557
1558     ty::ProjectionPredicate<'tcx> {
1559         p!(print(self.projection_ty), write(" == "), print(self.ty))
1560     }
1561
1562     ty::ProjectionTy<'tcx> {
1563         p!(print_def_path(self.item_def_id, self.substs));
1564     }
1565
1566     ty::ClosureKind {
1567         match *self {
1568             ty::ClosureKind::Fn => p!(write("Fn")),
1569             ty::ClosureKind::FnMut => p!(write("FnMut")),
1570             ty::ClosureKind::FnOnce => p!(write("FnOnce")),
1571         }
1572     }
1573
1574     ty::Predicate<'tcx> {
1575         match *self {
1576             ty::Predicate::Trait(ref data) => p!(print(data)),
1577             ty::Predicate::Subtype(ref predicate) => p!(print(predicate)),
1578             ty::Predicate::RegionOutlives(ref predicate) => p!(print(predicate)),
1579             ty::Predicate::TypeOutlives(ref predicate) => p!(print(predicate)),
1580             ty::Predicate::Projection(ref predicate) => p!(print(predicate)),
1581             ty::Predicate::WellFormed(ty) => p!(print(ty), write(" well-formed")),
1582             ty::Predicate::ObjectSafe(trait_def_id) => {
1583                 p!(write("the trait `"),
1584                    print_def_path(trait_def_id, &[]),
1585                    write("` is object-safe"))
1586             }
1587             ty::Predicate::ClosureKind(closure_def_id, _closure_substs, kind) => {
1588                 p!(write("the closure `"),
1589                    print_value_path(closure_def_id, &[]),
1590                    write("` implements the trait `{}`", kind))
1591             }
1592             ty::Predicate::ConstEvaluatable(def_id, substs) => {
1593                 p!(write("the constant `"),
1594                    print_value_path(def_id, substs),
1595                    write("` can be evaluated"))
1596             }
1597         }
1598     }
1599
1600     Kind<'tcx> {
1601         match self.unpack() {
1602             UnpackedKind::Lifetime(lt) => p!(print(lt)),
1603             UnpackedKind::Type(ty) => p!(print(ty)),
1604             UnpackedKind::Const(ct) => p!(print(ct)),
1605         }
1606     }
1607 }