src/librustc/ty/print/pretty.rs

   1 use crate::hir;
   2 use crate::hir::def::{Namespace, Def};
   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::ty::layout::Size;
  10 use crate::mir::interpret::{ConstValue, sign_extend, Scalar};
  11 use syntax::ast;
  12 use rustc_apfloat::ieee::{Double, Single};
  13 use rustc_apfloat::Float;
  14 use rustc_target::spec::abi::Abi;
  15 use syntax::symbol::{kw, InternedString};
  16
  17 use std::cell::Cell;
  18 use std::fmt::{self, Write as _};
  19 use std::ops::{Deref, DerefMut};
  20
  21 // `pretty` is a separate module only for organization.
  22 use super::*;
  23
  24 macro_rules! p {
  25     (@write($($data:expr),+)) => {
  26         write!(scoped_cx!(), $($data),+)?
  27     };
  28     (@print($x:expr)) => {
  29         scoped_cx!() = $x.print(scoped_cx!())?
  30     };
  31     (@$method:ident($($arg:expr),*)) => {
  32         scoped_cx!() = scoped_cx!().$method($($arg),*)?
  33     };
  34     ($($kind:ident $data:tt),+) => {{
  35         $(p!(@$kind $data);)+
  36     }};
  37 }
  38 macro_rules! define_scoped_cx {
  39     ($cx:ident) => {
  40         #[allow(unused_macros)]
  41         macro_rules! scoped_cx {
  42             () => ($cx)
  43         }
  44     };
  45 }
  46
  47 thread_local! {
  48     static FORCE_IMPL_FILENAME_LINE: Cell<bool> = Cell::new(false);
  49     static SHOULD_PREFIX_WITH_CRATE: Cell<bool> = Cell::new(false);
  50 }
  51
  52 /// Force us to name impls with just the filename/line number. We
  53 /// normally try to use types. But at some points, notably while printing
  54 /// cycle errors, this can result in extra or suboptimal error output,
  55 /// so this variable disables that check.
  56 pub fn with_forced_impl_filename_line<F: FnOnce() -> R, R>(f: F) -> R {
  57     FORCE_IMPL_FILENAME_LINE.with(|force| {
  58         let old = force.get();
  59         force.set(true);
  60         let result = f();
  61         force.set(old);
  62         result
  63     })
  64 }
  65
  66 /// Adds the `crate::` prefix to paths where appropriate.
  67 pub fn with_crate_prefix<F: FnOnce() -> R, R>(f: F) -> R {
  68     SHOULD_PREFIX_WITH_CRATE.with(|flag| {
  69         let old = flag.get();
  70         flag.set(true);
  71         let result = f();
  72         flag.set(old);
  73         result
  74     })
  75 }
  76
  77 /// The "region highlights" are used to control region printing during
  78 /// specific error messages. When a "region highlight" is enabled, it
  79 /// gives an alternate way to print specific regions. For now, we
  80 /// always print those regions using a number, so something like "`'0`".
  81 ///
  82 /// Regions not selected by the region highlight mode are presently
  83 /// unaffected.
  84 #[derive(Copy, Clone, Default)]
  85 pub struct RegionHighlightMode {
  86     /// If enabled, when we see the selected region, use "`'N`"
  87     /// instead of the ordinary behavior.
  88     highlight_regions: [Option<(ty::RegionKind, usize)>; 3],
  89
  90     /// If enabled, when printing a "free region" that originated from
  91     /// the given `ty::BoundRegion`, print it as "`'1`". Free regions that would ordinarily
  92     /// have names print as normal.
  93     ///
  94     /// This is used when you have a signature like `fn foo(x: &u32,
  95     /// y: &'a u32)` and we want to give a name to the region of the
  96     /// reference `x`.
  97     highlight_bound_region: Option<(ty::BoundRegion, usize)>,
  98 }
  99
 100 impl RegionHighlightMode {
 101     /// If `region` and `number` are both `Some`, invokes
 102     /// `highlighting_region`.
 103     pub fn maybe_highlighting_region(
 104         &mut self,
 105         region: Option<ty::Region<'_>>,
 106         number: Option<usize>,
 107     ) {
 108         if let Some(k) = region {
 109             if let Some(n) = number {
 110                 self.highlighting_region(k, n);
 111             }
 112         }
 113     }
 114
 115     /// Highlights the region inference variable `vid` as `'N`.
 116     pub fn highlighting_region(
 117         &mut self,
 118         region: ty::Region<'_>,
 119         number: usize,
 120     ) {
 121         let num_slots = self.highlight_regions.len();
 122         let first_avail_slot = self.highlight_regions.iter_mut()
 123             .filter(|s| s.is_none())
 124             .next()
 125             .unwrap_or_else(|| {
 126                 bug!(
 127                     "can only highlight {} placeholders at a time",
 128                     num_slots,
 129                 )
 130             });
 131         *first_avail_slot = Some((*region, number));
 132     }
 133
 134     /// Convenience wrapper for `highlighting_region`.
 135     pub fn highlighting_region_vid(
 136         &mut self,
 137         vid: ty::RegionVid,
 138         number: usize,
 139     ) {
 140         self.highlighting_region(&ty::ReVar(vid), number)
 141     }
 142
 143     /// Returns `Some(n)` with the number to use for the given region, if any.
 144     fn region_highlighted(&self, region: ty::Region<'_>) -> Option<usize> {
 145         self
 146             .highlight_regions
 147             .iter()
 148             .filter_map(|h| match h {
 149                 Some((r, n)) if r == region => Some(*n),
 150                 _ => None,
 151             })
 152             .next()
 153     }
 154
 155     /// Highlight the given bound region.
 156     /// We can only highlight one bound region at a time. See
 157     /// the field `highlight_bound_region` for more detailed notes.
 158     pub fn highlighting_bound_region(
 159         &mut self,
 160         br: ty::BoundRegion,
 161         number: usize,
 162     ) {
 163         assert!(self.highlight_bound_region.is_none());
 164         self.highlight_bound_region = Some((br, number));
 165     }
 166 }
 167
 168 /// Trait for printers that pretty-print using `fmt::Write` to the printer.
 169 pub trait PrettyPrinter<'gcx: 'tcx, 'tcx>:
 170     Printer<'gcx, 'tcx,
 171         Error = fmt::Error,
 172         Path = Self,
 173         Region = Self,
 174         Type = Self,
 175         DynExistential = Self,
 176     > +
 177     fmt::Write
 178 {
 179     /// Like `print_def_path` but for value paths.
 180     fn print_value_path(
 181         self,
 182         def_id: DefId,
 183         substs: &'tcx [Kind<'tcx>],
 184     ) -> Result<Self::Path, Self::Error> {
 185         self.print_def_path(def_id, substs)
 186     }
 187
 188     fn in_binder<T>(
 189         self,
 190         value: &ty::Binder<T>,
 191     ) -> Result<Self, Self::Error>
 192         where T: Print<'gcx, 'tcx, Self, Output = Self, Error = Self::Error> + TypeFoldable<'tcx>
 193     {
 194         value.skip_binder().print(self)
 195     }
 196
 197     /// Print comma-separated elements.
 198     fn comma_sep<T>(
 199         mut self,
 200         mut elems: impl Iterator<Item = T>,
 201     ) -> Result<Self, Self::Error>
 202         where T: Print<'gcx, 'tcx, Self, Output = Self, Error = Self::Error>
 203     {
 204         if let Some(first) = elems.next() {
 205             self = first.print(self)?;
 206             for elem in elems {
 207                 self.write_str(", ")?;
 208                 self = elem.print(self)?;
 209             }
 210         }
 211         Ok(self)
 212     }
 213
 214     /// Print `<...>` around what `f` prints.
 215     fn generic_delimiters(
 216         self,
 217         f: impl FnOnce(Self) -> Result<Self, Self::Error>,
 218     ) -> Result<Self, Self::Error>;
 219
 220     /// Return `true` if the region should be printed in
 221     /// optional positions, e.g. `&'a T` or `dyn Tr + 'b`.
 222     /// This is typically the case for all non-`'_` regions.
 223     fn region_should_not_be_omitted(
 224         &self,
 225         region: ty::Region<'_>,
 226     ) -> bool;
 227
 228     // Defaults (should not be overriden):
 229
 230     /// If possible, this returns a global path resolving to `def_id` that is visible
 231     /// from at least one local module and returns true. If the crate defining `def_id` is
 232     /// declared with an `extern crate`, the path is guaranteed to use the `extern crate`.
 233     fn try_print_visible_def_path(
 234         mut self,
 235         def_id: DefId,
 236     ) -> Result<(Self, bool), Self::Error> {
 237         define_scoped_cx!(self);
 238
 239         debug!("try_print_visible_def_path: def_id={:?}", def_id);
 240
 241         // If `def_id` is a direct or injected extern crate, return the
 242         // path to the crate followed by the path to the item within the crate.
 243         if def_id.index == CRATE_DEF_INDEX {
 244             let cnum = def_id.krate;
 245
 246             if cnum == LOCAL_CRATE {
 247                 return Ok((self.path_crate(cnum)?, true));
 248             }
 249
 250             // In local mode, when we encounter a crate other than
 251             // LOCAL_CRATE, execution proceeds in one of two ways:
 252             //
 253             // 1. for a direct dependency, where user added an
 254             //    `extern crate` manually, we put the `extern
 255             //    crate` as the parent. So you wind up with
 256             //    something relative to the current crate.
 257             // 2. for an extern inferred from a path or an indirect crate,
 258             //    where there is no explicit `extern crate`, we just prepend
 259             //    the crate name.
 260             match self.tcx().extern_crate(def_id) {
 261                 Some(&ExternCrate {
 262                     src: ExternCrateSource::Extern(def_id),
 263                     direct: true,
 264                     span,
 265                     ..
 266                 }) => {
 267                     debug!("try_print_visible_def_path: def_id={:?}", def_id);
 268                     return Ok((if !span.is_dummy() {
 269                         self.print_def_path(def_id, &[])?
 270                     } else {
 271                         self.path_crate(cnum)?
 272                     }, true));
 273                 }
 274                 None => {
 275                     return Ok((self.path_crate(cnum)?, true));
 276                 }
 277                 _ => {},
 278             }
 279         }
 280
 281         if def_id.is_local() {
 282             return Ok((self, false));
 283         }
 284
 285         let visible_parent_map = self.tcx().visible_parent_map(LOCAL_CRATE);
 286
 287         let mut cur_def_key = self.tcx().def_key(def_id);
 288         debug!("try_print_visible_def_path: cur_def_key={:?}", cur_def_key);
 289
 290         // For a constructor we want the name of its parent rather than <unnamed>.
 291         match cur_def_key.disambiguated_data.data {
 292             DefPathData::Ctor => {
 293                 let parent = DefId {
 294                     krate: def_id.krate,
 295                     index: cur_def_key.parent
 296                         .expect("DefPathData::Ctor/VariantData missing a parent"),
 297                 };
 298
 299                 cur_def_key = self.tcx().def_key(parent);
 300             },
 301             _ => {},
 302         }
 303
 304         let visible_parent = match visible_parent_map.get(&def_id).cloned() {
 305             Some(parent) => parent,
 306             None => return Ok((self, false)),
 307         };
 308         // HACK(eddyb) this bypasses `path_append`'s prefix printing to avoid
 309         // knowing ahead of time whether the entire path will succeed or not.
 310         // To support printers that do not implement `PrettyPrinter`, a `Vec` or
 311         // linked list on the stack would need to be built, before any printing.
 312         match self.try_print_visible_def_path(visible_parent)? {
 313             (cx, false) => return Ok((cx, false)),
 314             (cx, true) => self = cx,
 315         }
 316         let actual_parent = self.tcx().parent(def_id);
 317         debug!(
 318             "try_print_visible_def_path: visible_parent={:?} actual_parent={:?}",
 319             visible_parent, actual_parent,
 320         );
 321
 322         let mut data = cur_def_key.disambiguated_data.data;
 323         debug!(
 324             "try_print_visible_def_path: data={:?} visible_parent={:?} actual_parent={:?}",
 325             data, visible_parent, actual_parent,
 326         );
 327
 328         match data {
 329             // In order to output a path that could actually be imported (valid and visible),
 330             // we need to handle re-exports correctly.
 331             //
 332             // For example, take `std::os::unix::process::CommandExt`, this trait is actually
 333             // defined at `std::sys::unix::ext::process::CommandExt` (at time of writing).
 334             //
 335             // `std::os::unix` rexports the contents of `std::sys::unix::ext`. `std::sys` is
 336             // private so the "true" path to `CommandExt` isn't accessible.
 337             //
 338             // In this case, the `visible_parent_map` will look something like this:
 339             //
 340             // (child) -> (parent)
 341             // `std::sys::unix::ext::process::CommandExt` -> `std::sys::unix::ext::process`
 342             // `std::sys::unix::ext::process` -> `std::sys::unix::ext`
 343             // `std::sys::unix::ext` -> `std::os`
 344             //
 345             // This is correct, as the visible parent of `std::sys::unix::ext` is in fact
 346             // `std::os`.
 347             //
 348             // When printing the path to `CommandExt` and looking at the `cur_def_key` that
 349             // corresponds to `std::sys::unix::ext`, we would normally print `ext` and then go
 350             // to the parent - resulting in a mangled path like
 351             // `std::os::ext::process::CommandExt`.
 352             //
 353             // Instead, we must detect that there was a re-export and instead print `unix`
 354             // (which is the name `std::sys::unix::ext` was re-exported as in `std::os`). To
 355             // do this, we compare the parent of `std::sys::unix::ext` (`std::sys::unix`) with
 356             // the visible parent (`std::os`). If these do not match, then we iterate over
 357             // the children of the visible parent (as was done when computing
 358             // `visible_parent_map`), looking for the specific child we currently have and then
 359             // have access to the re-exported name.
 360             DefPathData::TypeNs(ref mut name) if Some(visible_parent) != actual_parent => {
 361                 let reexport = self.tcx().item_children(visible_parent)
 362                     .iter()
 363                     .find(|child| child.res.def_id() == def_id)
 364                     .map(|child| child.ident.as_interned_str());
 365                 if let Some(reexport) = reexport {
 366                     *name = reexport;
 367                 }
 368             }
 369             // Re-exported `extern crate` (#43189).
 370             DefPathData::CrateRoot => {
 371                 data = DefPathData::TypeNs(
 372                     self.tcx().original_crate_name(def_id.krate).as_interned_str(),
 373                 );
 374             }
 375             _ => {}
 376         }
 377         debug!("try_print_visible_def_path: data={:?}", data);
 378
 379         Ok((self.path_append(Ok, &DisambiguatedDefPathData {
 380             data,
 381             disambiguator: 0,
 382         })?, true))
 383     }
 384
 385     fn pretty_path_qualified(
 386         self,
 387         self_ty: Ty<'tcx>,
 388         trait_ref: Option<ty::TraitRef<'tcx>>,
 389     ) -> Result<Self::Path, Self::Error> {
 390         if trait_ref.is_none() {
 391             // Inherent impls. Try to print `Foo::bar` for an inherent
 392             // impl on `Foo`, but fallback to `<Foo>::bar` if self-type is
 393             // anything other than a simple path.
 394             match self_ty.sty {
 395                 ty::Adt(..) | ty::Foreign(_) |
 396                 ty::Bool | ty::Char | ty::Str |
 397                 ty::Int(_) | ty::Uint(_) | ty::Float(_) => {
 398                     return self_ty.print(self);
 399                 }
 400
 401                 _ => {}
 402             }
 403         }
 404
 405         self.generic_delimiters(|mut cx| {
 406             define_scoped_cx!(cx);
 407
 408             p!(print(self_ty));
 409             if let Some(trait_ref) = trait_ref {
 410                 p!(write(" as "), print(trait_ref));
 411             }
 412             Ok(cx)
 413         })
 414     }
 415
 416     fn pretty_path_append_impl(
 417         mut self,
 418         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
 419         self_ty: Ty<'tcx>,
 420         trait_ref: Option<ty::TraitRef<'tcx>>,
 421     ) -> Result<Self::Path, Self::Error> {
 422         self = print_prefix(self)?;
 423
 424         self.generic_delimiters(|mut cx| {
 425             define_scoped_cx!(cx);
 426
 427             p!(write("impl "));
 428             if let Some(trait_ref) = trait_ref {
 429                 p!(print(trait_ref), write(" for "));
 430             }
 431             p!(print(self_ty));
 432
 433             Ok(cx)
 434         })
 435     }
 436
 437     fn pretty_print_type(
 438         mut self,
 439         ty: Ty<'tcx>,
 440     ) -> Result<Self::Type, Self::Error> {
 441         define_scoped_cx!(self);
 442
 443         match ty.sty {
 444             ty::Bool => p!(write("bool")),
 445             ty::Char => p!(write("char")),
 446             ty::Int(t) => p!(write("{}", t.ty_to_string())),
 447             ty::Uint(t) => p!(write("{}", t.ty_to_string())),
 448             ty::Float(t) => p!(write("{}", t.ty_to_string())),
 449             ty::RawPtr(ref tm) => {
 450                 p!(write("*{} ", match tm.mutbl {
 451                     hir::MutMutable => "mut",
 452                     hir::MutImmutable => "const",
 453                 }));
 454                 p!(print(tm.ty))
 455             }
 456             ty::Ref(r, ty, mutbl) => {
 457                 p!(write("&"));
 458                 if self.region_should_not_be_omitted(r) {
 459                     p!(print(r), write(" "));
 460                 }
 461                 p!(print(ty::TypeAndMut { ty, mutbl }))
 462             }
 463             ty::Never => p!(write("!")),
 464             ty::Tuple(ref tys) => {
 465                 p!(write("("));
 466                 let mut tys = tys.iter();
 467                 if let Some(&ty) = tys.next() {
 468                     p!(print(ty), write(","));
 469                     if let Some(&ty) = tys.next() {
 470                         p!(write(" "), print(ty));
 471                         for &ty in tys {
 472                             p!(write(", "), print(ty));
 473                         }
 474                     }
 475                 }
 476                 p!(write(")"))
 477             }
 478             ty::FnDef(def_id, substs) => {
 479                 let sig = self.tcx().fn_sig(def_id).subst(self.tcx(), substs);
 480                 p!(print(sig), write(" {{"), print_value_path(def_id, substs), write("}}"));
 481             }
 482             ty::FnPtr(ref bare_fn) => {
 483                 p!(print(bare_fn))
 484             }
 485             ty::Infer(infer_ty) => p!(write("{}", infer_ty)),
 486             ty::Error => p!(write("[type error]")),
 487             ty::Param(ref param_ty) => p!(write("{}", param_ty)),
 488             ty::Bound(debruijn, bound_ty) => {
 489                 match bound_ty.kind {
 490                     ty::BoundTyKind::Anon => {
 491                         if debruijn == ty::INNERMOST {
 492                             p!(write("^{}", bound_ty.var.index()))
 493                         } else {
 494                             p!(write("^{}_{}", debruijn.index(), bound_ty.var.index()))
 495                         }
 496                     }
 497
 498                     ty::BoundTyKind::Param(p) => p!(write("{}", p)),
 499                 }
 500             }
 501             ty::Adt(def, substs) => {
 502                 p!(print_def_path(def.did, substs));
 503             }
 504             ty::Dynamic(data, r) => {
 505                 let print_r = self.region_should_not_be_omitted(r);
 506                 if print_r {
 507                     p!(write("("));
 508                 }
 509                 p!(write("dyn "), print(data));
 510                 if print_r {
 511                     p!(write(" + "), print(r), write(")"));
 512                 }
 513             }
 514             ty::Foreign(def_id) => {
 515                 p!(print_def_path(def_id, &[]));
 516             }
 517             ty::Projection(ref data) => p!(print(data)),
 518             ty::UnnormalizedProjection(ref data) => {
 519                 p!(write("Unnormalized("), print(data), write(")"))
 520             }
 521             ty::Placeholder(placeholder) => {
 522                 p!(write("Placeholder({:?})", placeholder))
 523             }
 524             ty::Opaque(def_id, substs) => {
 525                 // FIXME(eddyb) print this with `print_def_path`.
 526                 if self.tcx().sess.verbose() {
 527                     p!(write("Opaque({:?}, {:?})", def_id, substs));
 528                     return Ok(self);
 529                 }
 530
 531                 let def_key = self.tcx().def_key(def_id);
 532                 if let Some(name) = def_key.disambiguated_data.data.get_opt_name() {
 533                     p!(write("{}", name));
 534                     let mut substs = substs.iter();
 535                     // FIXME(eddyb) print this with `print_def_path`.
 536                     if let Some(first) = substs.next() {
 537                         p!(write("::<"));
 538                         p!(print(first));
 539                         for subst in substs {
 540                             p!(write(", "), print(subst));
 541                         }
 542                         p!(write(">"));
 543                     }
 544                     return Ok(self);
 545                 }
 546                 // Grab the "TraitA + TraitB" from `impl TraitA + TraitB`,
 547                 // by looking up the projections associated with the def_id.
 548                 let bounds = self.tcx().predicates_of(def_id).instantiate(self.tcx(), substs);
 549
 550                 let mut first = true;
 551                 let mut is_sized = false;
 552                 p!(write("impl"));
 553                 for predicate in bounds.predicates {
 554                     if let Some(trait_ref) = predicate.to_opt_poly_trait_ref() {
 555                         // Don't print +Sized, but rather +?Sized if absent.
 556                         if Some(trait_ref.def_id()) == self.tcx().lang_items().sized_trait() {
 557                             is_sized = true;
 558                             continue;
 559                         }
 560
 561                         p!(
 562                                 write("{}", if first { " " } else { "+" }),
 563                                 print(trait_ref));
 564                         first = false;
 565                     }
 566                 }
 567                 if !is_sized {
 568                     p!(write("{}?Sized", if first { " " } else { "+" }));
 569                 } else if first {
 570                     p!(write(" Sized"));
 571                 }
 572             }
 573             ty::Str => p!(write("str")),
 574             ty::Generator(did, substs, movability) => {
 575                 let upvar_tys = substs.upvar_tys(did, self.tcx());
 576                 let witness = substs.witness(did, self.tcx());
 577                 if movability == hir::GeneratorMovability::Movable {
 578                     p!(write("[generator"));
 579                 } else {
 580                     p!(write("[static generator"));
 581                 }
 582
 583                 // FIXME(eddyb) should use `def_span`.
 584                 if let Some(hir_id) = self.tcx().hir().as_local_hir_id(did) {
 585                     p!(write("@{:?}", self.tcx().hir().span_by_hir_id(hir_id)));
 586                     let mut sep = " ";
 587                     for (upvar, upvar_ty) in self.tcx().upvars(did)
 588                         .as_ref()
 589                         .map_or(&[][..], |v| &v[..])
 590                         .iter()
 591                         .zip(upvar_tys)
 592                     {
 593                         p!(
 594                             write("{}{}:",
 595                                     sep,
 596                                     self.tcx().hir().name_by_hir_id(upvar.var_id())),
 597                             print(upvar_ty));
 598                         sep = ", ";
 599                     }
 600                 } else {
 601                     // cross-crate closure types should only be
 602                     // visible in codegen bug reports, I imagine.
 603                     p!(write("@{:?}", did));
 604                     let mut sep = " ";
 605                     for (index, upvar_ty) in upvar_tys.enumerate() {
 606                         p!(
 607                                 write("{}{}:", sep, index),
 608                                 print(upvar_ty));
 609                         sep = ", ";
 610                     }
 611                 }
 612
 613                 p!(write(" "), print(witness), write("]"))
 614             },
 615             ty::GeneratorWitness(types) => {
 616                 p!(in_binder(&types));
 617             }
 618             ty::Closure(did, substs) => {
 619                 let upvar_tys = substs.upvar_tys(did, self.tcx());
 620                 p!(write("[closure"));
 621
 622                 // FIXME(eddyb) should use `def_span`.
 623                 if let Some(hir_id) = self.tcx().hir().as_local_hir_id(did) {
 624                     if self.tcx().sess.opts.debugging_opts.span_free_formats {
 625                         p!(write("@{:?}", hir_id));
 626                     } else {
 627                         p!(write("@{:?}", self.tcx().hir().span_by_hir_id(hir_id)));
 628                     }
 629                     let mut sep = " ";
 630                     for (upvar, upvar_ty) in self.tcx().upvars(did)
 631                         .as_ref()
 632                         .map_or(&[][..], |v| &v[..])
 633                         .iter()
 634                         .zip(upvar_tys)
 635                     {
 636                         p!(
 637                             write("{}{}:",
 638                                     sep,
 639                                     self.tcx().hir().name_by_hir_id(upvar.var_id())),
 640                             print(upvar_ty));
 641                         sep = ", ";
 642                     }
 643                 } else {
 644                     // cross-crate closure types should only be
 645                     // visible in codegen bug reports, I imagine.
 646                     p!(write("@{:?}", did));
 647                     let mut sep = " ";
 648                     for (index, upvar_ty) in upvar_tys.enumerate() {
 649                         p!(
 650                                 write("{}{}:", sep, index),
 651                                 print(upvar_ty));
 652                         sep = ", ";
 653                     }
 654                 }
 655
 656                 if self.tcx().sess.verbose() {
 657                     p!(write(
 658                         " closure_kind_ty={:?} closure_sig_ty={:?}",
 659                         substs.closure_kind_ty(did, self.tcx()),
 660                         substs.closure_sig_ty(did, self.tcx())
 661                     ));
 662                 }
 663
 664                 p!(write("]"))
 665             },
 666             ty::Array(ty, sz) => {
 667                 p!(write("["), print(ty), write("; "));
 668                 match sz.val {
 669                     ConstValue::Unevaluated(..) |
 670                     ConstValue::Infer(..) => p!(write("_")),
 671                     ConstValue::Param(ParamConst { name, .. }) =>
 672                         p!(write("{}", name)),
 673                     _ => p!(write("{}", sz.unwrap_usize(self.tcx()))),
 674                 }
 675                 p!(write("]"))
 676             }
 677             ty::Slice(ty) => {
 678                 p!(write("["), print(ty), write("]"))
 679             }
 680         }
 681
 682         Ok(self)
 683     }
 684
 685     fn pretty_print_dyn_existential(
 686         mut self,
 687         predicates: &'tcx ty::List<ty::ExistentialPredicate<'tcx>>,
 688     ) -> Result<Self::DynExistential, Self::Error> {
 689         define_scoped_cx!(self);
 690
 691         // Generate the main trait ref, including associated types.
 692         let mut first = true;
 693
 694         if let Some(principal) = predicates.principal() {
 695             p!(print_def_path(principal.def_id, &[]));
 696
 697             let mut resugared = false;
 698
 699             // Special-case `Fn(...) -> ...` and resugar it.
 700             let fn_trait_kind = self.tcx().lang_items().fn_trait_kind(principal.def_id);
 701             if !self.tcx().sess.verbose() && fn_trait_kind.is_some() {
 702                 if let ty::Tuple(ref args) = principal.substs.type_at(0).sty {
 703                     let mut projections = predicates.projection_bounds();
 704                     if let (Some(proj), None) = (projections.next(), projections.next()) {
 705                         let tys: Vec<_> = args.iter().map(|k| k.expect_ty()).collect();
 706                         p!(pretty_fn_sig(&tys, false, proj.ty));
 707                         resugared = true;
 708                     }
 709                 }
 710             }
 711
 712             // HACK(eddyb) this duplicates `FmtPrinter`'s `path_generic_args`,
 713             // in order to place the projections inside the `<...>`.
 714             if !resugared {
 715                 // Use a type that can't appear in defaults of type parameters.
 716                 let dummy_self = self.tcx().mk_ty_infer(ty::FreshTy(0));
 717                 let principal = principal.with_self_ty(self.tcx(), dummy_self);
 718
 719                 let args = self.generic_args_to_print(
 720                     self.tcx().generics_of(principal.def_id),
 721                     principal.substs,
 722                 );
 723
 724                 // Don't print `'_` if there's no unerased regions.
 725                 let print_regions = args.iter().any(|arg| {
 726                     match arg.unpack() {
 727                         UnpackedKind::Lifetime(r) => *r != ty::ReErased,
 728                         _ => false,
 729                     }
 730                 });
 731                 let mut args = args.iter().cloned().filter(|arg| {
 732                     match arg.unpack() {
 733                         UnpackedKind::Lifetime(_) => print_regions,
 734                         _ => true,
 735                     }
 736                 });
 737                 let mut projections = predicates.projection_bounds();
 738
 739                 let arg0 = args.next();
 740                 let projection0 = projections.next();
 741                 if arg0.is_some() || projection0.is_some() {
 742                     let args = arg0.into_iter().chain(args);
 743                     let projections = projection0.into_iter().chain(projections);
 744
 745                     p!(generic_delimiters(|mut cx| {
 746                         cx = cx.comma_sep(args)?;
 747                         if arg0.is_some() && projection0.is_some() {
 748                             write!(cx, ", ")?;
 749                         }
 750                         cx.comma_sep(projections)
 751                     }));
 752                 }
 753             }
 754             first = false;
 755         }
 756
 757         // Builtin bounds.
 758         // FIXME(eddyb) avoid printing twice (needed to ensure
 759         // that the auto traits are sorted *and* printed via cx).
 760         let mut auto_traits: Vec<_> = predicates.auto_traits().map(|did| {
 761             (self.tcx().def_path_str(did), did)
 762         }).collect();
 763
 764         // The auto traits come ordered by `DefPathHash`. While
 765         // `DefPathHash` is *stable* in the sense that it depends on
 766         // neither the host nor the phase of the moon, it depends
 767         // "pseudorandomly" on the compiler version and the target.
 768         //
 769         // To avoid that causing instabilities in compiletest
 770         // output, sort the auto-traits alphabetically.
 771         auto_traits.sort();
 772
 773         for (_, def_id) in auto_traits {
 774             if !first {
 775                 p!(write(" + "));
 776             }
 777             first = false;
 778
 779             p!(print_def_path(def_id, &[]));
 780         }
 781
 782         Ok(self)
 783     }
 784
 785     fn pretty_fn_sig(
 786         mut self,
 787         inputs: &[Ty<'tcx>],
 788         c_variadic: bool,
 789         output: Ty<'tcx>,
 790     ) -> Result<Self, Self::Error> {
 791         define_scoped_cx!(self);
 792
 793         p!(write("("));
 794         let mut inputs = inputs.iter();
 795         if let Some(&ty) = inputs.next() {
 796             p!(print(ty));
 797             for &ty in inputs {
 798                 p!(write(", "), print(ty));
 799             }
 800             if c_variadic {
 801                 p!(write(", ..."));
 802             }
 803         }
 804         p!(write(")"));
 805         if !output.is_unit() {
 806             p!(write(" -> "), print(output));
 807         }
 808
 809         Ok(self)
 810     }
 811 }
 812
 813 // HACK(eddyb) boxed to avoid moving around a large struct by-value.
 814 pub struct FmtPrinter<'a, 'gcx, 'tcx, F>(Box<FmtPrinterData<'a, 'gcx, 'tcx, F>>);
 815
 816 pub struct FmtPrinterData<'a, 'gcx, 'tcx, F> {
 817     tcx: TyCtxt<'a, 'gcx, 'tcx>,
 818     fmt: F,
 819
 820     empty_path: bool,
 821     in_value: bool,
 822
 823     used_region_names: FxHashSet<InternedString>,
 824     region_index: usize,
 825     binder_depth: usize,
 826
 827     pub region_highlight_mode: RegionHighlightMode,
 828 }
 829
 830 impl<F> Deref for FmtPrinter<'a, 'gcx, 'tcx, F> {
 831     type Target = FmtPrinterData<'a, 'gcx, 'tcx, F>;
 832     fn deref(&self) -> &Self::Target {
 833         &self.0
 834     }
 835 }
 836
 837 impl<F> DerefMut for FmtPrinter<'_, '_, '_, F> {
 838     fn deref_mut(&mut self) -> &mut Self::Target {
 839         &mut self.0
 840     }
 841 }
 842
 843 impl<F> FmtPrinter<'a, 'gcx, 'tcx, F> {
 844     pub fn new(tcx: TyCtxt<'a, 'gcx, 'tcx>, fmt: F, ns: Namespace) -> Self {
 845         FmtPrinter(Box::new(FmtPrinterData {
 846             tcx,
 847             fmt,
 848             empty_path: false,
 849             in_value: ns == Namespace::ValueNS,
 850             used_region_names: Default::default(),
 851             region_index: 0,
 852             binder_depth: 0,
 853             region_highlight_mode: RegionHighlightMode::default(),
 854         }))
 855     }
 856 }
 857
 858 impl TyCtxt<'_, '_, '_> {
 859     // HACK(eddyb) get rid of `def_path_str` and/or pass `Namespace` explicitly always
 860     // (but also some things just print a `DefId` generally so maybe we need this?)
 861     fn guess_def_namespace(self, def_id: DefId) -> Namespace {
 862         match self.def_key(def_id).disambiguated_data.data {
 863             DefPathData::TypeNs(..)
 864             | DefPathData::CrateRoot
 865             | DefPathData::ImplTrait => Namespace::TypeNS,
 866
 867             DefPathData::ValueNs(..)
 868             | DefPathData::AnonConst
 869             | DefPathData::ClosureExpr
 870             | DefPathData::Ctor => Namespace::ValueNS,
 871
 872             DefPathData::MacroNs(..) => Namespace::MacroNS,
 873
 874             _ => Namespace::TypeNS,
 875         }
 876     }
 877
 878     /// Returns a string identifying this `DefId`. This string is
 879     /// suitable for user output.
 880     pub fn def_path_str(self, def_id: DefId) -> String {
 881         let ns = self.guess_def_namespace(def_id);
 882         debug!("def_path_str: def_id={:?}, ns={:?}", def_id, ns);
 883         let mut s = String::new();
 884         let _ = FmtPrinter::new(self, &mut s, ns)
 885             .print_def_path(def_id, &[]);
 886         s
 887     }
 888 }
 889
 890 impl<F: fmt::Write> fmt::Write for FmtPrinter<'_, '_, '_, F> {
 891     fn write_str(&mut self, s: &str) -> fmt::Result {
 892         self.fmt.write_str(s)
 893     }
 894 }
 895
 896 impl<F: fmt::Write> Printer<'gcx, 'tcx> for FmtPrinter<'_, 'gcx, 'tcx, F> {
 897     type Error = fmt::Error;
 898
 899     type Path = Self;
 900     type Region = Self;
 901     type Type = Self;
 902     type DynExistential = Self;
 903
 904     fn tcx(&'a self) -> TyCtxt<'a, 'gcx, 'tcx> {
 905         self.tcx
 906     }
 907
 908     fn print_def_path(
 909         mut self,
 910         def_id: DefId,
 911         substs: &'tcx [Kind<'tcx>],
 912     ) -> Result<Self::Path, Self::Error> {
 913         define_scoped_cx!(self);
 914
 915         if substs.is_empty() {
 916             match self.try_print_visible_def_path(def_id)? {
 917                 (cx, true) => return Ok(cx),
 918                 (cx, false) => self = cx,
 919             }
 920         }
 921
 922         let key = self.tcx.def_key(def_id);
 923         if let DefPathData::Impl = key.disambiguated_data.data {
 924             // Always use types for non-local impls, where types are always
 925             // available, and filename/line-number is mostly uninteresting.
 926             let use_types =
 927                 !def_id.is_local() || {
 928                     // Otherwise, use filename/line-number if forced.
 929                     let force_no_types = FORCE_IMPL_FILENAME_LINE.with(|f| f.get());
 930                     !force_no_types
 931                 };
 932
 933             if !use_types {
 934                 // If no type info is available, fall back to
 935                 // pretty printing some span information. This should
 936                 // only occur very early in the compiler pipeline.
 937                 let parent_def_id = DefId { index: key.parent.unwrap(), ..def_id };
 938                 let span = self.tcx.def_span(def_id);
 939
 940                 self = self.print_def_path(parent_def_id, &[])?;
 941
 942                 // HACK(eddyb) copy of `path_append` to avoid
 943                 // constructing a `DisambiguatedDefPathData`.
 944                 if !self.empty_path {
 945                     write!(self, "::")?;
 946                 }
 947                 write!(self, "<impl at {:?}>", span)?;
 948                 self.empty_path = false;
 949
 950                 return Ok(self);
 951             }
 952         }
 953
 954         self.default_print_def_path(def_id, substs)
 955     }
 956
 957     fn print_region(
 958         self,
 959         region: ty::Region<'_>,
 960     ) -> Result<Self::Region, Self::Error> {
 961         self.pretty_print_region(region)
 962     }
 963
 964     fn print_type(
 965         self,
 966         ty: Ty<'tcx>,
 967     ) -> Result<Self::Type, Self::Error> {
 968         self.pretty_print_type(ty)
 969     }
 970
 971     fn print_dyn_existential(
 972         self,
 973         predicates: &'tcx ty::List<ty::ExistentialPredicate<'tcx>>,
 974     ) -> Result<Self::DynExistential, Self::Error> {
 975         self.pretty_print_dyn_existential(predicates)
 976     }
 977
 978     fn path_crate(
 979         mut self,
 980         cnum: CrateNum,
 981     ) -> Result<Self::Path, Self::Error> {
 982         self.empty_path = true;
 983         if cnum == LOCAL_CRATE {
 984             if self.tcx.sess.rust_2018() {
 985                 // We add the `crate::` keyword on Rust 2018, only when desired.
 986                 if SHOULD_PREFIX_WITH_CRATE.with(|flag| flag.get()) {
 987                     write!(self, "{}", kw::Crate)?;
 988                     self.empty_path = false;
 989                 }
 990             }
 991         } else {
 992             write!(self, "{}", self.tcx.crate_name(cnum))?;
 993             self.empty_path = false;
 994         }
 995         Ok(self)
 996     }
 997     fn path_qualified(
 998         mut self,
 999         self_ty: Ty<'tcx>,
1000         trait_ref: Option<ty::TraitRef<'tcx>>,
1001     ) -> Result<Self::Path, Self::Error> {
1002         self = self.pretty_path_qualified(self_ty, trait_ref)?;
1003         self.empty_path = false;
1004         Ok(self)
1005     }
1006
1007     fn path_append_impl(
1008         mut self,
1009         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1010         _disambiguated_data: &DisambiguatedDefPathData,
1011         self_ty: Ty<'tcx>,
1012         trait_ref: Option<ty::TraitRef<'tcx>>,
1013     ) -> Result<Self::Path, Self::Error> {
1014         self = self.pretty_path_append_impl(|mut cx| {
1015             cx = print_prefix(cx)?;
1016             if !cx.empty_path {
1017                 write!(cx, "::")?;
1018             }
1019
1020             Ok(cx)
1021         }, self_ty, trait_ref)?;
1022         self.empty_path = false;
1023         Ok(self)
1024     }
1025     fn path_append(
1026         mut self,
1027         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1028         disambiguated_data: &DisambiguatedDefPathData,
1029     ) -> Result<Self::Path, Self::Error> {
1030         self = print_prefix(self)?;
1031
1032         // Skip `::{{constructor}}` on tuple/unit structs.
1033         match disambiguated_data.data {
1034             DefPathData::Ctor => return Ok(self),
1035             _ => {}
1036         }
1037
1038         // FIXME(eddyb) `name` should never be empty, but it
1039         // currently is for `extern { ... }` "foreign modules".
1040         let name = disambiguated_data.data.as_interned_str().as_str();
1041         if !name.is_empty() {
1042             if !self.empty_path {
1043                 write!(self, "::")?;
1044             }
1045             write!(self, "{}", name)?;
1046
1047             // FIXME(eddyb) this will print e.g. `{{closure}}#3`, but it
1048             // might be nicer to use something else, e.g. `{closure#3}`.
1049             let dis = disambiguated_data.disambiguator;
1050             let print_dis =
1051                 disambiguated_data.data.get_opt_name().is_none() ||
1052                 dis != 0 && self.tcx.sess.verbose();
1053             if print_dis {
1054                 write!(self, "#{}", dis)?;
1055             }
1056
1057             self.empty_path = false;
1058         }
1059
1060         Ok(self)
1061     }
1062     fn path_generic_args(
1063         mut self,
1064         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1065         args: &[Kind<'tcx>],
1066     ) -> Result<Self::Path, Self::Error> {
1067         self = print_prefix(self)?;
1068
1069         // Don't print `'_` if there's no unerased regions.
1070         let print_regions = args.iter().any(|arg| {
1071             match arg.unpack() {
1072                 UnpackedKind::Lifetime(r) => *r != ty::ReErased,
1073                 _ => false,
1074             }
1075         });
1076         let args = args.iter().cloned().filter(|arg| {
1077             match arg.unpack() {
1078                 UnpackedKind::Lifetime(_) => print_regions,
1079                 _ => true,
1080             }
1081         });
1082
1083         if args.clone().next().is_some() {
1084             if self.in_value {
1085                 write!(self, "::")?;
1086             }
1087             self.generic_delimiters(|cx| cx.comma_sep(args))
1088         } else {
1089             Ok(self)
1090         }
1091     }
1092 }
1093
1094 impl<F: fmt::Write> PrettyPrinter<'gcx, 'tcx> for FmtPrinter<'_, 'gcx, 'tcx, F> {
1095     fn print_value_path(
1096         mut self,
1097         def_id: DefId,
1098         substs: &'tcx [Kind<'tcx>],
1099     ) -> Result<Self::Path, Self::Error> {
1100         let was_in_value = std::mem::replace(&mut self.in_value, true);
1101         self = self.print_def_path(def_id, substs)?;
1102         self.in_value = was_in_value;
1103
1104         Ok(self)
1105     }
1106
1107     fn in_binder<T>(
1108         self,
1109         value: &ty::Binder<T>,
1110     ) -> Result<Self, Self::Error>
1111         where T: Print<'gcx, 'tcx, Self, Output = Self, Error = Self::Error> + TypeFoldable<'tcx>
1112     {
1113         self.pretty_in_binder(value)
1114     }
1115
1116     fn generic_delimiters(
1117         mut self,
1118         f: impl FnOnce(Self) -> Result<Self, Self::Error>,
1119     ) -> Result<Self, Self::Error> {
1120         write!(self, "<")?;
1121
1122         let was_in_value = std::mem::replace(&mut self.in_value, false);
1123         let mut inner = f(self)?;
1124         inner.in_value = was_in_value;
1125
1126         write!(inner, ">")?;
1127         Ok(inner)
1128     }
1129
1130     fn region_should_not_be_omitted(
1131         &self,
1132         region: ty::Region<'_>,
1133     ) -> bool {
1134         let highlight = self.region_highlight_mode;
1135         if highlight.region_highlighted(region).is_some() {
1136             return true;
1137         }
1138
1139         if self.tcx.sess.verbose() {
1140             return true;
1141         }
1142
1143         let identify_regions = self.tcx.sess.opts.debugging_opts.identify_regions;
1144
1145         match *region {
1146             ty::ReEarlyBound(ref data) => {
1147                 data.name.as_symbol() != kw::Invalid &&
1148                 data.name.as_symbol() != kw::UnderscoreLifetime
1149             }
1150
1151             ty::ReLateBound(_, br) |
1152             ty::ReFree(ty::FreeRegion { bound_region: br, .. }) |
1153             ty::RePlaceholder(ty::Placeholder { name: br, .. }) => {
1154                 if let ty::BrNamed(_, name) = br {
1155                     if name.as_symbol() != kw::Invalid &&
1156                        name.as_symbol() != kw::UnderscoreLifetime {
1157                         return true;
1158                     }
1159                 }
1160
1161                 if let Some((region, _)) = highlight.highlight_bound_region {
1162                     if br == region {
1163                         return true;
1164                     }
1165                 }
1166
1167                 false
1168             }
1169
1170             ty::ReScope(_) |
1171             ty::ReVar(_) if identify_regions => true,
1172
1173             ty::ReVar(_) |
1174             ty::ReScope(_) |
1175             ty::ReErased => false,
1176
1177             ty::ReStatic |
1178             ty::ReEmpty |
1179             ty::ReClosureBound(_) => true,
1180         }
1181     }
1182 }
1183
1184 // HACK(eddyb) limited to `FmtPrinter` because of `region_highlight_mode`.
1185 impl<F: fmt::Write> FmtPrinter<'_, '_, '_, F> {
1186     pub fn pretty_print_region(
1187         mut self,
1188         region: ty::Region<'_>,
1189     ) -> Result<Self, fmt::Error> {
1190         define_scoped_cx!(self);
1191
1192         // Watch out for region highlights.
1193         let highlight = self.region_highlight_mode;
1194         if let Some(n) = highlight.region_highlighted(region) {
1195             p!(write("'{}", n));
1196             return Ok(self);
1197         }
1198
1199         if self.tcx.sess.verbose() {
1200             p!(write("{:?}", region));
1201             return Ok(self);
1202         }
1203
1204         let identify_regions = self.tcx.sess.opts.debugging_opts.identify_regions;
1205
1206         // These printouts are concise.  They do not contain all the information
1207         // the user might want to diagnose an error, but there is basically no way
1208         // to fit that into a short string.  Hence the recommendation to use
1209         // `explain_region()` or `note_and_explain_region()`.
1210         match *region {
1211             ty::ReEarlyBound(ref data) => {
1212                 if data.name.as_symbol() != kw::Invalid {
1213                     p!(write("{}", data.name));
1214                     return Ok(self);
1215                 }
1216             }
1217             ty::ReLateBound(_, br) |
1218             ty::ReFree(ty::FreeRegion { bound_region: br, .. }) |
1219             ty::RePlaceholder(ty::Placeholder { name: br, .. }) => {
1220                 if let ty::BrNamed(_, name) = br {
1221                     if name.as_symbol() != kw::Invalid &&
1222                        name.as_symbol() != kw::UnderscoreLifetime {
1223                         p!(write("{}", name));
1224                         return Ok(self);
1225                     }
1226                 }
1227
1228                 if let Some((region, counter)) = highlight.highlight_bound_region {
1229                     if br == region {
1230                         p!(write("'{}", counter));
1231                         return Ok(self);
1232                     }
1233                 }
1234             }
1235             ty::ReScope(scope) if identify_regions => {
1236                 match scope.data {
1237                     region::ScopeData::Node =>
1238                         p!(write("'{}s", scope.item_local_id().as_usize())),
1239                     region::ScopeData::CallSite =>
1240                         p!(write("'{}cs", scope.item_local_id().as_usize())),
1241                     region::ScopeData::Arguments =>
1242                         p!(write("'{}as", scope.item_local_id().as_usize())),
1243                     region::ScopeData::Destruction =>
1244                         p!(write("'{}ds", scope.item_local_id().as_usize())),
1245                     region::ScopeData::Remainder(first_statement_index) => p!(write(
1246                         "'{}_{}rs",
1247                         scope.item_local_id().as_usize(),
1248                         first_statement_index.index()
1249                     )),
1250                 }
1251                 return Ok(self);
1252             }
1253             ty::ReVar(region_vid) if identify_regions => {
1254                 p!(write("{:?}", region_vid));
1255                 return Ok(self);
1256             }
1257             ty::ReVar(_) => {}
1258             ty::ReScope(_) |
1259             ty::ReErased => {}
1260             ty::ReStatic => {
1261                 p!(write("'static"));
1262                 return Ok(self);
1263             }
1264             ty::ReEmpty => {
1265                 p!(write("'<empty>"));
1266                 return Ok(self);
1267             }
1268
1269             // The user should never encounter these in unsubstituted form.
1270             ty::ReClosureBound(vid) => {
1271                 p!(write("{:?}", vid));
1272                 return Ok(self);
1273             }
1274         }
1275
1276         p!(write("'_"));
1277
1278         Ok(self)
1279     }
1280 }
1281
1282 // HACK(eddyb) limited to `FmtPrinter` because of `binder_depth`,
1283 // `region_index` and `used_region_names`.
1284 impl<F: fmt::Write> FmtPrinter<'_, 'gcx, 'tcx, F> {
1285     pub fn pretty_in_binder<T>(
1286         mut self,
1287         value: &ty::Binder<T>,
1288     ) -> Result<Self, fmt::Error>
1289         where T: Print<'gcx, 'tcx, Self, Output = Self, Error = fmt::Error> + TypeFoldable<'tcx>
1290     {
1291         fn name_by_region_index(index: usize) -> InternedString {
1292             match index {
1293                 0 => InternedString::intern("'r"),
1294                 1 => InternedString::intern("'s"),
1295                 i => InternedString::intern(&format!("'t{}", i-2)),
1296             }
1297         }
1298
1299         // Replace any anonymous late-bound regions with named
1300         // variants, using gensym'd identifiers, so that we can
1301         // clearly differentiate between named and unnamed regions in
1302         // the output. We'll probably want to tweak this over time to
1303         // decide just how much information to give.
1304         if self.binder_depth == 0 {
1305             self.prepare_late_bound_region_info(value);
1306         }
1307
1308         let mut empty = true;
1309         let mut start_or_continue = |cx: &mut Self, start: &str, cont: &str| {
1310             write!(cx, "{}", if empty {
1311                 empty = false;
1312                 start
1313             } else {
1314                 cont
1315             })
1316         };
1317
1318         define_scoped_cx!(self);
1319
1320         let old_region_index = self.region_index;
1321         let mut region_index = old_region_index;
1322         let new_value = self.tcx.replace_late_bound_regions(value, |br| {
1323             let _ = start_or_continue(&mut self, "for<", ", ");
1324             let br = match br {
1325                 ty::BrNamed(_, name) => {
1326                     let _ = write!(self, "{}", name);
1327                     br
1328                 }
1329                 ty::BrAnon(_) |
1330                 ty::BrFresh(_) |
1331                 ty::BrEnv => {
1332                     let name = loop {
1333                         let name = name_by_region_index(region_index);
1334                         region_index += 1;
1335                         if !self.used_region_names.contains(&name) {
1336                             break name;
1337                         }
1338                     };
1339                     let _ = write!(self, "{}", name);
1340                     ty::BrNamed(DefId::local(CRATE_DEF_INDEX), name)
1341                 }
1342             };
1343             self.tcx.mk_region(ty::ReLateBound(ty::INNERMOST, br))
1344         }).0;
1345         start_or_continue(&mut self, "", "> ")?;
1346
1347         self.binder_depth += 1;
1348         self.region_index = region_index;
1349         let mut inner = new_value.print(self)?;
1350         inner.region_index = old_region_index;
1351         inner.binder_depth -= 1;
1352         Ok(inner)
1353     }
1354
1355     fn prepare_late_bound_region_info<T>(&mut self, value: &ty::Binder<T>)
1356         where T: TypeFoldable<'tcx>
1357     {
1358
1359         struct LateBoundRegionNameCollector<'a>(&'a mut FxHashSet<InternedString>);
1360         impl<'tcx> ty::fold::TypeVisitor<'tcx> for LateBoundRegionNameCollector<'_> {
1361             fn visit_region(&mut self, r: ty::Region<'tcx>) -> bool {
1362                 match *r {
1363                     ty::ReLateBound(_, ty::BrNamed(_, name)) => {
1364                         self.0.insert(name);
1365                     },
1366                     _ => {},
1367                 }
1368                 r.super_visit_with(self)
1369             }
1370         }
1371
1372         self.used_region_names.clear();
1373         let mut collector = LateBoundRegionNameCollector(&mut self.used_region_names);
1374         value.visit_with(&mut collector);
1375         self.region_index = 0;
1376     }
1377 }
1378
1379 impl<'gcx: 'tcx, 'tcx, T, P: PrettyPrinter<'gcx, 'tcx>> Print<'gcx, 'tcx, P>
1380     for ty::Binder<T>
1381     where T: Print<'gcx, 'tcx, P, Output = P, Error = P::Error> + TypeFoldable<'tcx>
1382 {
1383     type Output = P;
1384     type Error = P::Error;
1385     fn print(&self, cx: P) -> Result<Self::Output, Self::Error> {
1386         cx.in_binder(self)
1387     }
1388 }
1389
1390 impl<'gcx: 'tcx, 'tcx, T, U, P: PrettyPrinter<'gcx, 'tcx>> Print<'gcx, 'tcx, P>
1391     for ty::OutlivesPredicate<T, U>
1392     where T: Print<'gcx, 'tcx, P, Output = P, Error = P::Error>,
1393           U: Print<'gcx, 'tcx, P, Output = P, Error = P::Error>,
1394 {
1395     type Output = P;
1396     type Error = P::Error;
1397     fn print(&self, mut cx: P) -> Result<Self::Output, Self::Error> {
1398         define_scoped_cx!(cx);
1399         p!(print(self.0), write(" : "), print(self.1));
1400         Ok(cx)
1401     }
1402 }
1403
1404 macro_rules! forward_display_to_print {
1405     ($($ty:ty),+) => {
1406         $(impl fmt::Display for $ty {
1407             fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1408                 ty::tls::with(|tcx| {
1409                     tcx.lift(self)
1410                         .expect("could not lift for printing")
1411                         .print(FmtPrinter::new(tcx, f, Namespace::TypeNS))?;
1412                     Ok(())
1413                 })
1414             }
1415         })+
1416     };
1417 }
1418
1419 macro_rules! define_print_and_forward_display {
1420     (($self:ident, $cx:ident): $($ty:ty $print:block)+) => {
1421         $(impl<'gcx: 'tcx, 'tcx, P: PrettyPrinter<'gcx, 'tcx>> Print<'gcx, 'tcx, P> for $ty {
1422             type Output = P;
1423             type Error = fmt::Error;
1424             fn print(&$self, $cx: P) -> Result<Self::Output, Self::Error> {
1425                 #[allow(unused_mut)]
1426                 let mut $cx = $cx;
1427                 define_scoped_cx!($cx);
1428                 let _: () = $print;
1429                 #[allow(unreachable_code)]
1430                 Ok($cx)
1431             }
1432         })+
1433
1434         forward_display_to_print!($($ty),+);
1435     };
1436 }
1437
1438 // HACK(eddyb) this is separate because `ty::RegionKind` doesn't need lifting.
1439 impl fmt::Display for ty::RegionKind {
1440     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1441         ty::tls::with(|tcx| {
1442             self.print(FmtPrinter::new(tcx, f, Namespace::TypeNS))?;
1443             Ok(())
1444         })
1445     }
1446 }
1447
1448 forward_display_to_print! {
1449     Ty<'tcx>,
1450     &'tcx ty::List<ty::ExistentialPredicate<'tcx>>,
1451
1452     // HACK(eddyb) these are exhaustive instead of generic,
1453     // because `for<'gcx: 'tcx, 'tcx>` isn't possible yet.
1454     ty::Binder<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>,
1455     ty::Binder<ty::TraitRef<'tcx>>,
1456     ty::Binder<ty::FnSig<'tcx>>,
1457     ty::Binder<ty::TraitPredicate<'tcx>>,
1458     ty::Binder<ty::SubtypePredicate<'tcx>>,
1459     ty::Binder<ty::ProjectionPredicate<'tcx>>,
1460     ty::Binder<ty::OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>>,
1461     ty::Binder<ty::OutlivesPredicate<ty::Region<'tcx>, ty::Region<'tcx>>>,
1462
1463     ty::OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>,
1464     ty::OutlivesPredicate<ty::Region<'tcx>, ty::Region<'tcx>>
1465 }
1466
1467 define_print_and_forward_display! {
1468     (self, cx):
1469
1470     &'tcx ty::List<Ty<'tcx>> {
1471         p!(write("{{"));
1472         let mut tys = self.iter();
1473         if let Some(&ty) = tys.next() {
1474             p!(print(ty));
1475             for &ty in tys {
1476                 p!(write(", "), print(ty));
1477             }
1478         }
1479         p!(write("}}"))
1480     }
1481
1482     ty::TypeAndMut<'tcx> {
1483         p!(write("{}", if self.mutbl == hir::MutMutable { "mut " } else { "" }),
1484             print(self.ty))
1485     }
1486
1487     ty::ExistentialTraitRef<'tcx> {
1488         // Use a type that can't appear in defaults of type parameters.
1489         let dummy_self = cx.tcx().mk_ty_infer(ty::FreshTy(0));
1490         let trait_ref = self.with_self_ty(cx.tcx(), dummy_self);
1491         p!(print(trait_ref))
1492     }
1493
1494     ty::ExistentialProjection<'tcx> {
1495         let name = cx.tcx().associated_item(self.item_def_id).ident;
1496         p!(write("{} = ", name), print(self.ty))
1497     }
1498
1499     ty::ExistentialPredicate<'tcx> {
1500         match *self {
1501             ty::ExistentialPredicate::Trait(x) => p!(print(x)),
1502             ty::ExistentialPredicate::Projection(x) => p!(print(x)),
1503             ty::ExistentialPredicate::AutoTrait(def_id) => {
1504                 p!(print_def_path(def_id, &[]));
1505             }
1506         }
1507     }
1508
1509     ty::FnSig<'tcx> {
1510         if self.unsafety == hir::Unsafety::Unsafe {
1511             p!(write("unsafe "));
1512         }
1513
1514         if self.abi != Abi::Rust {
1515             p!(write("extern {} ", self.abi));
1516         }
1517
1518         p!(write("fn"), pretty_fn_sig(self.inputs(), self.c_variadic, self.output()));
1519     }
1520
1521     ty::InferTy {
1522         if cx.tcx().sess.verbose() {
1523             p!(write("{:?}", self));
1524             return Ok(cx);
1525         }
1526         match *self {
1527             ty::TyVar(_) => p!(write("_")),
1528             ty::IntVar(_) => p!(write("{}", "{integer}")),
1529             ty::FloatVar(_) => p!(write("{}", "{float}")),
1530             ty::FreshTy(v) => p!(write("FreshTy({})", v)),
1531             ty::FreshIntTy(v) => p!(write("FreshIntTy({})", v)),
1532             ty::FreshFloatTy(v) => p!(write("FreshFloatTy({})", v))
1533         }
1534     }
1535
1536     ty::TraitRef<'tcx> {
1537         p!(print_def_path(self.def_id, self.substs));
1538     }
1539
1540     &'tcx ty::Const<'tcx> {
1541         let u8 = cx.tcx().types.u8;
1542         if let ty::FnDef(did, substs) = self.ty.sty {
1543             p!(print_value_path(did, substs));
1544             return Ok(cx);
1545         }
1546         if let ConstValue::Unevaluated(did, substs) = self.val {
1547             match cx.tcx().describe_def(did) {
1548                 | Some(Def::Static(_, _))
1549                 | Some(Def::Const(_, false))
1550                 | Some(Def::AssociatedConst(_)) => p!(write("{}", cx.tcx().def_path_str(did))),
1551                 _ => p!(write("_")),
1552             }
1553             return Ok(cx);
1554         }
1555         if let ConstValue::Infer(..) = self.val {
1556             p!(write("_: "), print(self.ty));
1557             return Ok(cx);
1558         }
1559         if let ConstValue::Param(ParamConst { name, .. }) = self.val {
1560             p!(write("{}", name));
1561             return Ok(cx);
1562         }
1563         if let ConstValue::Scalar(Scalar::Bits { bits, .. }) = self.val {
1564             match self.ty.sty {
1565                 ty::Bool => {
1566                     p!(write("{}", if bits == 0 { "false" } else { "true" }));
1567                     return Ok(cx);
1568                 },
1569                 ty::Float(ast::FloatTy::F32) => {
1570                     p!(write("{}f32", Single::from_bits(bits)));
1571                     return Ok(cx);
1572                 },
1573                 ty::Float(ast::FloatTy::F64) => {
1574                     p!(write("{}f64", Double::from_bits(bits)));
1575                     return Ok(cx);
1576                 },
1577                 ty::Uint(ui) => {
1578                     p!(write("{}{}", bits, ui));
1579                     return Ok(cx);
1580                 },
1581                 ty::Int(i) =>{
1582                     let ty = cx.tcx().lift_to_global(&self.ty).unwrap();
1583                     let size = cx.tcx().layout_of(ty::ParamEnv::empty().and(ty))
1584                         .unwrap()
1585                         .size;
1586                     p!(write("{}{}", sign_extend(bits, size) as i128, i));
1587                     return Ok(cx);
1588                 },
1589                 ty::Char => {
1590                     p!(write("{:?}", ::std::char::from_u32(bits as u32).unwrap()));
1591                     return Ok(cx);
1592                 }
1593                 _ => {},
1594             }
1595         }
1596         if let ty::Ref(_, ref_ty, _) = self.ty.sty {
1597             let byte_str = match (self.val, &ref_ty.sty) {
1598                 (ConstValue::Scalar(Scalar::Ptr(ptr)), ty::Array(t, n)) if *t == u8 => {
1599                     let n = n.unwrap_usize(cx.tcx());
1600                     Some(cx.tcx()
1601                         .alloc_map.lock()
1602                         .unwrap_memory(ptr.alloc_id)
1603                         .get_bytes(&cx.tcx(), ptr, Size::from_bytes(n)).unwrap())
1604                 },
1605                 (ConstValue::Slice { data, start, end }, ty::Slice(t)) if *t == u8 => {
1606                     Some(&data.bytes[start..end])
1607                 },
1608                 (ConstValue::Slice { data, start, end }, ty::Str) => {
1609                     let slice = &data.bytes[start..end];
1610                     let s = ::std::str::from_utf8(slice)
1611                         .expect("non utf8 str from miri");
1612                     p!(write("{:?}", s));
1613                     return Ok(cx);
1614                 },
1615                 _ => None,
1616             };
1617             if let Some(byte_str) = byte_str {
1618                 p!(write("b\""));
1619                 for &c in byte_str {
1620                     for e in std::ascii::escape_default(c) {
1621                         cx.write_char(e as char)?;
1622                     }
1623                 }
1624                 p!(write("\""));
1625                 return Ok(cx);
1626             }
1627         }
1628         p!(write("{:?} : ", self.val), print(self.ty));
1629     }
1630
1631     ty::ParamTy {
1632         p!(write("{}", self.name))
1633     }
1634
1635     ty::ParamConst {
1636         p!(write("{}", self.name))
1637     }
1638
1639     ty::SubtypePredicate<'tcx> {
1640         p!(print(self.a), write(" <: "), print(self.b))
1641     }
1642
1643     ty::TraitPredicate<'tcx> {
1644         p!(print(self.trait_ref.self_ty()), write(": "), print(self.trait_ref))
1645     }
1646
1647     ty::ProjectionPredicate<'tcx> {
1648         p!(print(self.projection_ty), write(" == "), print(self.ty))
1649     }
1650
1651     ty::ProjectionTy<'tcx> {
1652         p!(print_def_path(self.item_def_id, self.substs));
1653     }
1654
1655     ty::ClosureKind {
1656         match *self {
1657             ty::ClosureKind::Fn => p!(write("Fn")),
1658             ty::ClosureKind::FnMut => p!(write("FnMut")),
1659             ty::ClosureKind::FnOnce => p!(write("FnOnce")),
1660         }
1661     }
1662
1663     ty::Predicate<'tcx> {
1664         match *self {
1665             ty::Predicate::Trait(ref data) => p!(print(data)),
1666             ty::Predicate::Subtype(ref predicate) => p!(print(predicate)),
1667             ty::Predicate::RegionOutlives(ref predicate) => p!(print(predicate)),
1668             ty::Predicate::TypeOutlives(ref predicate) => p!(print(predicate)),
1669             ty::Predicate::Projection(ref predicate) => p!(print(predicate)),
1670             ty::Predicate::WellFormed(ty) => p!(print(ty), write(" well-formed")),
1671             ty::Predicate::ObjectSafe(trait_def_id) => {
1672                 p!(write("the trait `"),
1673                    print_def_path(trait_def_id, &[]),
1674                    write("` is object-safe"))
1675             }
1676             ty::Predicate::ClosureKind(closure_def_id, _closure_substs, kind) => {
1677                 p!(write("the closure `"),
1678                    print_value_path(closure_def_id, &[]),
1679                    write("` implements the trait `{}`", kind))
1680             }
1681             ty::Predicate::ConstEvaluatable(def_id, substs) => {
1682                 p!(write("the constant `"),
1683                    print_value_path(def_id, substs),
1684                    write("` can be evaluated"))
1685             }
1686         }
1687     }
1688
1689     Kind<'tcx> {
1690         match self.unpack() {
1691             UnpackedKind::Lifetime(lt) => p!(print(lt)),
1692             UnpackedKind::Type(ty) => p!(print(ty)),
1693             UnpackedKind::Const(ct) => p!(print(ct)),
1694         }
1695     }
1696 }