src/librustc/ty/print/pretty.rs

   1 use crate::hir;
   2 use crate::hir::def::{Namespace, DefKind};
   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<'tcx>:
 170     Printer<
 171         'tcx,
 172         Error = fmt::Error,
 173         Path = Self,
 174         Region = Self,
 175         Type = Self,
 176         DynExistential = Self,
 177         Const = Self,
 178     > + fmt::Write
 179 {
 180     /// Like `print_def_path` but for value paths.
 181     fn print_value_path(
 182         self,
 183         def_id: DefId,
 184         substs: &'tcx [Kind<'tcx>],
 185     ) -> Result<Self::Path, Self::Error> {
 186         self.print_def_path(def_id, substs)
 187     }
 188
 189     fn in_binder<T>(self, value: &ty::Binder<T>) -> Result<Self, Self::Error>
 190     where
 191         T: Print<'tcx, Self, Output = Self, Error = Self::Error> + TypeFoldable<'tcx>,
 192     {
 193         value.skip_binder().print(self)
 194     }
 195
 196     /// Print comma-separated elements.
 197     fn comma_sep<T>(mut self, mut elems: impl Iterator<Item = T>) -> Result<Self, Self::Error>
 198     where
 199         T: Print<'tcx, Self, Output = Self, Error = Self::Error>,
 200     {
 201         if let Some(first) = elems.next() {
 202             self = first.print(self)?;
 203             for elem in elems {
 204                 self.write_str(", ")?;
 205                 self = elem.print(self)?;
 206             }
 207         }
 208         Ok(self)
 209     }
 210
 211     /// Print `<...>` around what `f` prints.
 212     fn generic_delimiters(
 213         self,
 214         f: impl FnOnce(Self) -> Result<Self, Self::Error>,
 215     ) -> Result<Self, Self::Error>;
 216
 217     /// Return `true` if the region should be printed in
 218     /// optional positions, e.g. `&'a T` or `dyn Tr + 'b`.
 219     /// This is typically the case for all non-`'_` regions.
 220     fn region_should_not_be_omitted(
 221         &self,
 222         region: ty::Region<'_>,
 223     ) -> bool;
 224
 225     // Defaults (should not be overriden):
 226
 227     /// If possible, this returns a global path resolving to `def_id` that is visible
 228     /// from at least one local module and returns true. If the crate defining `def_id` is
 229     /// declared with an `extern crate`, the path is guaranteed to use the `extern crate`.
 230     fn try_print_visible_def_path(
 231         self,
 232         def_id: DefId,
 233     ) -> Result<(Self, bool), Self::Error> {
 234         let mut callers = Vec::new();
 235         self.try_print_visible_def_path_recur(def_id, &mut callers)
 236     }
 237
 238     /// Does the work of `try_print_visible_def_path`, building the
 239     /// full definition path recursively before attempting to
 240     /// post-process it into the valid and visible version that
 241     /// accounts for re-exports.
 242     ///
 243     /// This method should only be callled by itself or
 244     /// `try_print_visible_def_path`.
 245     ///
 246     /// `callers` is a chain of visible_parent's leading to `def_id`,
 247     /// to support cycle detection during recursion.
 248     fn try_print_visible_def_path_recur(
 249         mut self,
 250         def_id: DefId,
 251         callers: &mut Vec<DefId>,
 252     ) -> Result<(Self, bool), Self::Error> {
 253         define_scoped_cx!(self);
 254
 255         debug!("try_print_visible_def_path: def_id={:?}", def_id);
 256
 257         // If `def_id` is a direct or injected extern crate, return the
 258         // path to the crate followed by the path to the item within the crate.
 259         if def_id.index == CRATE_DEF_INDEX {
 260             let cnum = def_id.krate;
 261
 262             if cnum == LOCAL_CRATE {
 263                 return Ok((self.path_crate(cnum)?, true));
 264             }
 265
 266             // In local mode, when we encounter a crate other than
 267             // LOCAL_CRATE, execution proceeds in one of two ways:
 268             //
 269             // 1. for a direct dependency, where user added an
 270             //    `extern crate` manually, we put the `extern
 271             //    crate` as the parent. So you wind up with
 272             //    something relative to the current crate.
 273             // 2. for an extern inferred from a path or an indirect crate,
 274             //    where there is no explicit `extern crate`, we just prepend
 275             //    the crate name.
 276             match self.tcx().extern_crate(def_id) {
 277                 Some(&ExternCrate {
 278                     src: ExternCrateSource::Extern(def_id),
 279                     direct: true,
 280                     span,
 281                     ..
 282                 }) => {
 283                     debug!("try_print_visible_def_path: def_id={:?}", def_id);
 284                     return Ok((if !span.is_dummy() {
 285                         self.print_def_path(def_id, &[])?
 286                     } else {
 287                         self.path_crate(cnum)?
 288                     }, true));
 289                 }
 290                 None => {
 291                     return Ok((self.path_crate(cnum)?, true));
 292                 }
 293                 _ => {},
 294             }
 295         }
 296
 297         if def_id.is_local() {
 298             return Ok((self, false));
 299         }
 300
 301         let visible_parent_map = self.tcx().visible_parent_map(LOCAL_CRATE);
 302
 303         let mut cur_def_key = self.tcx().def_key(def_id);
 304         debug!("try_print_visible_def_path: cur_def_key={:?}", cur_def_key);
 305
 306         // For a constructor we want the name of its parent rather than <unnamed>.
 307         match cur_def_key.disambiguated_data.data {
 308             DefPathData::Ctor => {
 309                 let parent = DefId {
 310                     krate: def_id.krate,
 311                     index: cur_def_key.parent
 312                         .expect("DefPathData::Ctor/VariantData missing a parent"),
 313                 };
 314
 315                 cur_def_key = self.tcx().def_key(parent);
 316             },
 317             _ => {},
 318         }
 319
 320         let visible_parent = match visible_parent_map.get(&def_id).cloned() {
 321             Some(parent) => parent,
 322             None => return Ok((self, false)),
 323         };
 324         if callers.contains(&visible_parent) {
 325             return Ok((self, false));
 326         }
 327         callers.push(visible_parent);
 328         // HACK(eddyb) this bypasses `path_append`'s prefix printing to avoid
 329         // knowing ahead of time whether the entire path will succeed or not.
 330         // To support printers that do not implement `PrettyPrinter`, a `Vec` or
 331         // linked list on the stack would need to be built, before any printing.
 332         match self.try_print_visible_def_path_recur(visible_parent, callers)? {
 333             (cx, false) => return Ok((cx, false)),
 334             (cx, true) => self = cx,
 335         }
 336         callers.pop();
 337         let actual_parent = self.tcx().parent(def_id);
 338         debug!(
 339             "try_print_visible_def_path: visible_parent={:?} actual_parent={:?}",
 340             visible_parent, actual_parent,
 341         );
 342
 343         let mut data = cur_def_key.disambiguated_data.data;
 344         debug!(
 345             "try_print_visible_def_path: data={:?} visible_parent={:?} actual_parent={:?}",
 346             data, visible_parent, actual_parent,
 347         );
 348
 349         match data {
 350             // In order to output a path that could actually be imported (valid and visible),
 351             // we need to handle re-exports correctly.
 352             //
 353             // For example, take `std::os::unix::process::CommandExt`, this trait is actually
 354             // defined at `std::sys::unix::ext::process::CommandExt` (at time of writing).
 355             //
 356             // `std::os::unix` rexports the contents of `std::sys::unix::ext`. `std::sys` is
 357             // private so the "true" path to `CommandExt` isn't accessible.
 358             //
 359             // In this case, the `visible_parent_map` will look something like this:
 360             //
 361             // (child) -> (parent)
 362             // `std::sys::unix::ext::process::CommandExt` -> `std::sys::unix::ext::process`
 363             // `std::sys::unix::ext::process` -> `std::sys::unix::ext`
 364             // `std::sys::unix::ext` -> `std::os`
 365             //
 366             // This is correct, as the visible parent of `std::sys::unix::ext` is in fact
 367             // `std::os`.
 368             //
 369             // When printing the path to `CommandExt` and looking at the `cur_def_key` that
 370             // corresponds to `std::sys::unix::ext`, we would normally print `ext` and then go
 371             // to the parent - resulting in a mangled path like
 372             // `std::os::ext::process::CommandExt`.
 373             //
 374             // Instead, we must detect that there was a re-export and instead print `unix`
 375             // (which is the name `std::sys::unix::ext` was re-exported as in `std::os`). To
 376             // do this, we compare the parent of `std::sys::unix::ext` (`std::sys::unix`) with
 377             // the visible parent (`std::os`). If these do not match, then we iterate over
 378             // the children of the visible parent (as was done when computing
 379             // `visible_parent_map`), looking for the specific child we currently have and then
 380             // have access to the re-exported name.
 381             DefPathData::TypeNs(ref mut name) if Some(visible_parent) != actual_parent => {
 382                 let reexport = self.tcx().item_children(visible_parent)
 383                     .iter()
 384                     .find(|child| child.res.def_id() == def_id)
 385                     .map(|child| child.ident.as_interned_str());
 386                 if let Some(reexport) = reexport {
 387                     *name = reexport;
 388                 }
 389             }
 390             // Re-exported `extern crate` (#43189).
 391             DefPathData::CrateRoot => {
 392                 data = DefPathData::TypeNs(
 393                     self.tcx().original_crate_name(def_id.krate).as_interned_str(),
 394                 );
 395             }
 396             _ => {}
 397         }
 398         debug!("try_print_visible_def_path: data={:?}", data);
 399
 400         Ok((self.path_append(Ok, &DisambiguatedDefPathData {
 401             data,
 402             disambiguator: 0,
 403         })?, true))
 404     }
 405
 406     fn pretty_path_qualified(
 407         self,
 408         self_ty: Ty<'tcx>,
 409         trait_ref: Option<ty::TraitRef<'tcx>>,
 410     ) -> Result<Self::Path, Self::Error> {
 411         if trait_ref.is_none() {
 412             // Inherent impls. Try to print `Foo::bar` for an inherent
 413             // impl on `Foo`, but fallback to `<Foo>::bar` if self-type is
 414             // anything other than a simple path.
 415             match self_ty.sty {
 416                 ty::Adt(..) | ty::Foreign(_) |
 417                 ty::Bool | ty::Char | ty::Str |
 418                 ty::Int(_) | ty::Uint(_) | ty::Float(_) => {
 419                     return self_ty.print(self);
 420                 }
 421
 422                 _ => {}
 423             }
 424         }
 425
 426         self.generic_delimiters(|mut cx| {
 427             define_scoped_cx!(cx);
 428
 429             p!(print(self_ty));
 430             if let Some(trait_ref) = trait_ref {
 431                 p!(write(" as "), print(trait_ref));
 432             }
 433             Ok(cx)
 434         })
 435     }
 436
 437     fn pretty_path_append_impl(
 438         mut self,
 439         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
 440         self_ty: Ty<'tcx>,
 441         trait_ref: Option<ty::TraitRef<'tcx>>,
 442     ) -> Result<Self::Path, Self::Error> {
 443         self = print_prefix(self)?;
 444
 445         self.generic_delimiters(|mut cx| {
 446             define_scoped_cx!(cx);
 447
 448             p!(write("impl "));
 449             if let Some(trait_ref) = trait_ref {
 450                 p!(print(trait_ref), write(" for "));
 451             }
 452             p!(print(self_ty));
 453
 454             Ok(cx)
 455         })
 456     }
 457
 458     fn pretty_print_type(
 459         mut self,
 460         ty: Ty<'tcx>,
 461     ) -> Result<Self::Type, Self::Error> {
 462         define_scoped_cx!(self);
 463
 464         match ty.sty {
 465             ty::Bool => p!(write("bool")),
 466             ty::Char => p!(write("char")),
 467             ty::Int(t) => p!(write("{}", t.ty_to_string())),
 468             ty::Uint(t) => p!(write("{}", t.ty_to_string())),
 469             ty::Float(t) => p!(write("{}", t.ty_to_string())),
 470             ty::RawPtr(ref tm) => {
 471                 p!(write("*{} ", match tm.mutbl {
 472                     hir::MutMutable => "mut",
 473                     hir::MutImmutable => "const",
 474                 }));
 475                 p!(print(tm.ty))
 476             }
 477             ty::Ref(r, ty, mutbl) => {
 478                 p!(write("&"));
 479                 if self.region_should_not_be_omitted(r) {
 480                     p!(print(r), write(" "));
 481                 }
 482                 p!(print(ty::TypeAndMut { ty, mutbl }))
 483             }
 484             ty::Never => p!(write("!")),
 485             ty::Tuple(ref tys) => {
 486                 p!(write("("));
 487                 let mut tys = tys.iter();
 488                 if let Some(&ty) = tys.next() {
 489                     p!(print(ty), write(","));
 490                     if let Some(&ty) = tys.next() {
 491                         p!(write(" "), print(ty));
 492                         for &ty in tys {
 493                             p!(write(", "), print(ty));
 494                         }
 495                     }
 496                 }
 497                 p!(write(")"))
 498             }
 499             ty::FnDef(def_id, substs) => {
 500                 let sig = self.tcx().fn_sig(def_id).subst(self.tcx(), substs);
 501                 p!(print(sig), write(" {{"), print_value_path(def_id, substs), write("}}"));
 502             }
 503             ty::FnPtr(ref bare_fn) => {
 504                 p!(print(bare_fn))
 505             }
 506             ty::Infer(infer_ty) => {
 507                 if let ty::TyVar(ty_vid) = infer_ty {
 508                     if let Some(name) = self.infer_ty_name(ty_vid) {
 509                         p!(write("{}", name))
 510                     } else {
 511                         p!(write("{}", infer_ty))
 512                     }
 513                 } else {
 514                     p!(write("{}", infer_ty))
 515                 }
 516             },
 517             ty::Error => p!(write("[type error]")),
 518             ty::Param(ref param_ty) => p!(write("{}", param_ty)),
 519             ty::Bound(debruijn, bound_ty) => {
 520                 match bound_ty.kind {
 521                     ty::BoundTyKind::Anon => {
 522                         if debruijn == ty::INNERMOST {
 523                             p!(write("^{}", bound_ty.var.index()))
 524                         } else {
 525                             p!(write("^{}_{}", debruijn.index(), bound_ty.var.index()))
 526                         }
 527                     }
 528
 529                     ty::BoundTyKind::Param(p) => p!(write("{}", p)),
 530                 }
 531             }
 532             ty::Adt(def, substs) => {
 533                 p!(print_def_path(def.did, substs));
 534             }
 535             ty::Dynamic(data, r) => {
 536                 let print_r = self.region_should_not_be_omitted(r);
 537                 if print_r {
 538                     p!(write("("));
 539                 }
 540                 p!(write("dyn "), print(data));
 541                 if print_r {
 542                     p!(write(" + "), print(r), write(")"));
 543                 }
 544             }
 545             ty::Foreign(def_id) => {
 546                 p!(print_def_path(def_id, &[]));
 547             }
 548             ty::Projection(ref data) => p!(print(data)),
 549             ty::UnnormalizedProjection(ref data) => {
 550                 p!(write("Unnormalized("), print(data), write(")"))
 551             }
 552             ty::Placeholder(placeholder) => {
 553                 p!(write("Placeholder({:?})", placeholder))
 554             }
 555             ty::Opaque(def_id, substs) => {
 556                 // FIXME(eddyb) print this with `print_def_path`.
 557                 if self.tcx().sess.verbose() {
 558                     p!(write("Opaque({:?}, {:?})", def_id, substs));
 559                     return Ok(self);
 560                 }
 561
 562                 let def_key = self.tcx().def_key(def_id);
 563                 if let Some(name) = def_key.disambiguated_data.data.get_opt_name() {
 564                     p!(write("{}", name));
 565                     let mut substs = substs.iter();
 566                     // FIXME(eddyb) print this with `print_def_path`.
 567                     if let Some(first) = substs.next() {
 568                         p!(write("::<"));
 569                         p!(print(first));
 570                         for subst in substs {
 571                             p!(write(", "), print(subst));
 572                         }
 573                         p!(write(">"));
 574                     }
 575                     return Ok(self);
 576                 }
 577                 // Grab the "TraitA + TraitB" from `impl TraitA + TraitB`,
 578                 // by looking up the projections associated with the def_id.
 579                 let bounds = self.tcx().predicates_of(def_id).instantiate(self.tcx(), substs);
 580
 581                 let mut first = true;
 582                 let mut is_sized = false;
 583                 p!(write("impl"));
 584                 for predicate in bounds.predicates {
 585                     if let Some(trait_ref) = predicate.to_opt_poly_trait_ref() {
 586                         // Don't print +Sized, but rather +?Sized if absent.
 587                         if Some(trait_ref.def_id()) == self.tcx().lang_items().sized_trait() {
 588                             is_sized = true;
 589                             continue;
 590                         }
 591
 592                         p!(
 593                                 write("{}", if first { " " } else { "+" }),
 594                                 print(trait_ref));
 595                         first = false;
 596                     }
 597                 }
 598                 if !is_sized {
 599                     p!(write("{}?Sized", if first { " " } else { "+" }));
 600                 } else if first {
 601                     p!(write(" Sized"));
 602                 }
 603             }
 604             ty::Str => p!(write("str")),
 605             ty::Generator(did, substs, movability) => {
 606                 let upvar_tys = substs.upvar_tys(did, self.tcx());
 607                 let witness = substs.witness(did, self.tcx());
 608                 if movability == hir::GeneratorMovability::Movable {
 609                     p!(write("[generator"));
 610                 } else {
 611                     p!(write("[static generator"));
 612                 }
 613
 614                 // FIXME(eddyb) should use `def_span`.
 615                 if let Some(hir_id) = self.tcx().hir().as_local_hir_id(did) {
 616                     p!(write("@{:?}", self.tcx().hir().span(hir_id)));
 617                     let mut sep = " ";
 618                     for (&var_id, upvar_ty) in self.tcx().upvars(did)
 619                         .as_ref()
 620                         .iter()
 621                         .flat_map(|v| v.keys())
 622                         .zip(upvar_tys)
 623                     {
 624                         p!(
 625                             write("{}{}:",
 626                                     sep,
 627                                     self.tcx().hir().name(var_id)),
 628                             print(upvar_ty));
 629                         sep = ", ";
 630                     }
 631                 } else {
 632                     // cross-crate closure types should only be
 633                     // visible in codegen bug reports, I imagine.
 634                     p!(write("@{:?}", did));
 635                     let mut sep = " ";
 636                     for (index, upvar_ty) in upvar_tys.enumerate() {
 637                         p!(
 638                                 write("{}{}:", sep, index),
 639                                 print(upvar_ty));
 640                         sep = ", ";
 641                     }
 642                 }
 643
 644                 p!(write(" "), print(witness), write("]"))
 645             },
 646             ty::GeneratorWitness(types) => {
 647                 p!(in_binder(&types));
 648             }
 649             ty::Closure(did, substs) => {
 650                 let upvar_tys = substs.upvar_tys(did, self.tcx());
 651                 p!(write("[closure"));
 652
 653                 // FIXME(eddyb) should use `def_span`.
 654                 if let Some(hir_id) = self.tcx().hir().as_local_hir_id(did) {
 655                     if self.tcx().sess.opts.debugging_opts.span_free_formats {
 656                         p!(write("@{:?}", hir_id));
 657                     } else {
 658                         p!(write("@{:?}", self.tcx().hir().span(hir_id)));
 659                     }
 660                     let mut sep = " ";
 661                     for (&var_id, upvar_ty) in self.tcx().upvars(did)
 662                         .as_ref()
 663                         .iter()
 664                         .flat_map(|v| v.keys())
 665                         .zip(upvar_tys)
 666                     {
 667                         p!(
 668                             write("{}{}:",
 669                                     sep,
 670                                     self.tcx().hir().name(var_id)),
 671                             print(upvar_ty));
 672                         sep = ", ";
 673                     }
 674                 } else {
 675                     // cross-crate closure types should only be
 676                     // visible in codegen bug reports, I imagine.
 677                     p!(write("@{:?}", did));
 678                     let mut sep = " ";
 679                     for (index, upvar_ty) in upvar_tys.enumerate() {
 680                         p!(
 681                                 write("{}{}:", sep, index),
 682                                 print(upvar_ty));
 683                         sep = ", ";
 684                     }
 685                 }
 686
 687                 if self.tcx().sess.verbose() {
 688                     p!(write(
 689                         " closure_kind_ty={:?} closure_sig_ty={:?}",
 690                         substs.closure_kind_ty(did, self.tcx()),
 691                         substs.closure_sig_ty(did, self.tcx())
 692                     ));
 693                 }
 694
 695                 p!(write("]"))
 696             },
 697             ty::Array(ty, sz) => {
 698                 p!(write("["), print(ty), write("; "));
 699                 if let Some(n) = sz.assert_usize(self.tcx()) {
 700                     p!(write("{}", n));
 701                 } else {
 702                     p!(write("_"));
 703                 }
 704                 p!(write("]"))
 705             }
 706             ty::Slice(ty) => {
 707                 p!(write("["), print(ty), write("]"))
 708             }
 709         }
 710
 711         Ok(self)
 712     }
 713
 714     fn infer_ty_name(&self, _: ty::TyVid) -> Option<String> {
 715         None
 716     }
 717
 718     fn pretty_print_dyn_existential(
 719         mut self,
 720         predicates: &'tcx ty::List<ty::ExistentialPredicate<'tcx>>,
 721     ) -> Result<Self::DynExistential, Self::Error> {
 722         define_scoped_cx!(self);
 723
 724         // Generate the main trait ref, including associated types.
 725         let mut first = true;
 726
 727         if let Some(principal) = predicates.principal() {
 728             p!(print_def_path(principal.def_id, &[]));
 729
 730             let mut resugared = false;
 731
 732             // Special-case `Fn(...) -> ...` and resugar it.
 733             let fn_trait_kind = self.tcx().lang_items().fn_trait_kind(principal.def_id);
 734             if !self.tcx().sess.verbose() && fn_trait_kind.is_some() {
 735                 if let ty::Tuple(ref args) = principal.substs.type_at(0).sty {
 736                     let mut projections = predicates.projection_bounds();
 737                     if let (Some(proj), None) = (projections.next(), projections.next()) {
 738                         let tys: Vec<_> = args.iter().map(|k| k.expect_ty()).collect();
 739                         p!(pretty_fn_sig(&tys, false, proj.ty));
 740                         resugared = true;
 741                     }
 742                 }
 743             }
 744
 745             // HACK(eddyb) this duplicates `FmtPrinter`'s `path_generic_args`,
 746             // in order to place the projections inside the `<...>`.
 747             if !resugared {
 748                 // Use a type that can't appear in defaults of type parameters.
 749                 let dummy_self = self.tcx().mk_ty_infer(ty::FreshTy(0));
 750                 let principal = principal.with_self_ty(self.tcx(), dummy_self);
 751
 752                 let args = self.generic_args_to_print(
 753                     self.tcx().generics_of(principal.def_id),
 754                     principal.substs,
 755                 );
 756
 757                 // Don't print `'_` if there's no unerased regions.
 758                 let print_regions = args.iter().any(|arg| {
 759                     match arg.unpack() {
 760                         UnpackedKind::Lifetime(r) => *r != ty::ReErased,
 761                         _ => false,
 762                     }
 763                 });
 764                 let mut args = args.iter().cloned().filter(|arg| {
 765                     match arg.unpack() {
 766                         UnpackedKind::Lifetime(_) => print_regions,
 767                         _ => true,
 768                     }
 769                 });
 770                 let mut projections = predicates.projection_bounds();
 771
 772                 let arg0 = args.next();
 773                 let projection0 = projections.next();
 774                 if arg0.is_some() || projection0.is_some() {
 775                     let args = arg0.into_iter().chain(args);
 776                     let projections = projection0.into_iter().chain(projections);
 777
 778                     p!(generic_delimiters(|mut cx| {
 779                         cx = cx.comma_sep(args)?;
 780                         if arg0.is_some() && projection0.is_some() {
 781                             write!(cx, ", ")?;
 782                         }
 783                         cx.comma_sep(projections)
 784                     }));
 785                 }
 786             }
 787             first = false;
 788         }
 789
 790         // Builtin bounds.
 791         // FIXME(eddyb) avoid printing twice (needed to ensure
 792         // that the auto traits are sorted *and* printed via cx).
 793         let mut auto_traits: Vec<_> = predicates.auto_traits().map(|did| {
 794             (self.tcx().def_path_str(did), did)
 795         }).collect();
 796
 797         // The auto traits come ordered by `DefPathHash`. While
 798         // `DefPathHash` is *stable* in the sense that it depends on
 799         // neither the host nor the phase of the moon, it depends
 800         // "pseudorandomly" on the compiler version and the target.
 801         //
 802         // To avoid that causing instabilities in compiletest
 803         // output, sort the auto-traits alphabetically.
 804         auto_traits.sort();
 805
 806         for (_, def_id) in auto_traits {
 807             if !first {
 808                 p!(write(" + "));
 809             }
 810             first = false;
 811
 812             p!(print_def_path(def_id, &[]));
 813         }
 814
 815         Ok(self)
 816     }
 817
 818     fn pretty_fn_sig(
 819         mut self,
 820         inputs: &[Ty<'tcx>],
 821         c_variadic: bool,
 822         output: Ty<'tcx>,
 823     ) -> Result<Self, Self::Error> {
 824         define_scoped_cx!(self);
 825
 826         p!(write("("));
 827         let mut inputs = inputs.iter();
 828         if let Some(&ty) = inputs.next() {
 829             p!(print(ty));
 830             for &ty in inputs {
 831                 p!(write(", "), print(ty));
 832             }
 833             if c_variadic {
 834                 p!(write(", ..."));
 835             }
 836         }
 837         p!(write(")"));
 838         if !output.is_unit() {
 839             p!(write(" -> "), print(output));
 840         }
 841
 842         Ok(self)
 843     }
 844
 845     fn pretty_print_const(
 846         mut self,
 847         ct: &'tcx ty::Const<'tcx>,
 848     ) -> Result<Self::Const, Self::Error> {
 849         define_scoped_cx!(self);
 850
 851         let u8 = self.tcx().types.u8;
 852         if let ty::FnDef(did, substs) = ct.ty.sty {
 853             p!(print_value_path(did, substs));
 854             return Ok(self);
 855         }
 856         if let ConstValue::Unevaluated(did, substs) = ct.val {
 857             match self.tcx().def_kind(did) {
 858                 | Some(DefKind::Static)
 859                 | Some(DefKind::Const)
 860                 | Some(DefKind::AssocConst) => p!(print_value_path(did, substs)),
 861                 _ => if did.is_local() {
 862                     let span = self.tcx().def_span(did);
 863                     if let Ok(snip) = self.tcx().sess.source_map().span_to_snippet(span) {
 864                         p!(write("{}", snip))
 865                     } else {
 866                         p!(write("_: "), print(ct.ty))
 867                     }
 868                 } else {
 869                     p!(write("_: "), print(ct.ty))
 870                 },
 871             }
 872             return Ok(self);
 873         }
 874         if let ConstValue::Infer(..) = ct.val {
 875             p!(write("_: "), print(ct.ty));
 876             return Ok(self);
 877         }
 878         if let ConstValue::Param(ParamConst { name, .. }) = ct.val {
 879             p!(write("{}", name));
 880             return Ok(self);
 881         }
 882         if let ConstValue::Scalar(Scalar::Raw { data, .. }) = ct.val {
 883             match ct.ty.sty {
 884                 ty::Bool => {
 885                     p!(write("{}", if data == 0 { "false" } else { "true" }));
 886                     return Ok(self);
 887                 },
 888                 ty::Float(ast::FloatTy::F32) => {
 889                     p!(write("{}f32", Single::from_bits(data)));
 890                     return Ok(self);
 891                 },
 892                 ty::Float(ast::FloatTy::F64) => {
 893                     p!(write("{}f64", Double::from_bits(data)));
 894                     return Ok(self);
 895                 },
 896                 ty::Uint(ui) => {
 897                     p!(write("{}{}", data, ui));
 898                     return Ok(self);
 899                 },
 900                 ty::Int(i) =>{
 901                     let ty = self.tcx().lift_to_global(&ct.ty).unwrap();
 902                     let size = self.tcx().layout_of(ty::ParamEnv::empty().and(ty))
 903                         .unwrap()
 904                         .size;
 905                     p!(write("{}{}", sign_extend(data, size) as i128, i));
 906                     return Ok(self);
 907                 },
 908                 ty::Char => {
 909                     p!(write("{:?}", ::std::char::from_u32(data as u32).unwrap()));
 910                     return Ok(self);
 911                 }
 912                 _ => {},
 913             }
 914         }
 915         if let ty::Ref(_, ref_ty, _) = ct.ty.sty {
 916             let byte_str = match (ct.val, &ref_ty.sty) {
 917                 (ConstValue::Scalar(Scalar::Ptr(ptr)), ty::Array(t, n)) if *t == u8 => {
 918                     let n = n.unwrap_usize(self.tcx());
 919                     Some(self.tcx()
 920                         .alloc_map.lock()
 921                         .unwrap_memory(ptr.alloc_id)
 922                         .get_bytes(&self.tcx(), ptr, Size::from_bytes(n)).unwrap())
 923                 },
 924                 (ConstValue::Slice { data, start, end }, ty::Slice(t)) if *t == u8 => {
 925                     Some(&data.bytes[start..end])
 926                 },
 927                 (ConstValue::Slice { data, start, end }, ty::Str) => {
 928                     let slice = &data.bytes[start..end];
 929                     let s = ::std::str::from_utf8(slice)
 930                         .expect("non utf8 str from miri");
 931                     p!(write("{:?}", s));
 932                     return Ok(self);
 933                 },
 934                 _ => None,
 935             };
 936             if let Some(byte_str) = byte_str {
 937                 p!(write("b\""));
 938                 for &c in byte_str {
 939                     for e in std::ascii::escape_default(c) {
 940                         self.write_char(e as char)?;
 941                     }
 942                 }
 943                 p!(write("\""));
 944                 return Ok(self);
 945             }
 946         }
 947         p!(write("{:?} : ", ct.val), print(ct.ty));
 948
 949         Ok(self)
 950     }
 951 }
 952
 953 // HACK(eddyb) boxed to avoid moving around a large struct by-value.
 954 pub struct FmtPrinter<'a, 'tcx, F>(Box<FmtPrinterData<'a, 'tcx, F>>);
 955
 956 pub struct FmtPrinterData<'a, 'tcx, F> {
 957     tcx: TyCtxt<'tcx>,
 958     fmt: F,
 959
 960     empty_path: bool,
 961     in_value: bool,
 962
 963     used_region_names: FxHashSet<InternedString>,
 964     region_index: usize,
 965     binder_depth: usize,
 966
 967     pub region_highlight_mode: RegionHighlightMode,
 968
 969     pub name_resolver: Option<Box<&'a dyn Fn(ty::sty::TyVid) -> Option<String>>>,
 970 }
 971
 972 impl<F> Deref for FmtPrinter<'a, 'tcx, F> {
 973     type Target = FmtPrinterData<'a, 'tcx, F>;
 974     fn deref(&self) -> &Self::Target {
 975         &self.0
 976     }
 977 }
 978
 979 impl<F> DerefMut for FmtPrinter<'_, '_, F> {
 980     fn deref_mut(&mut self) -> &mut Self::Target {
 981         &mut self.0
 982     }
 983 }
 984
 985 impl<F> FmtPrinter<'a, 'tcx, F> {
 986     pub fn new(tcx: TyCtxt<'tcx>, fmt: F, ns: Namespace) -> Self {
 987         FmtPrinter(Box::new(FmtPrinterData {
 988             tcx,
 989             fmt,
 990             empty_path: false,
 991             in_value: ns == Namespace::ValueNS,
 992             used_region_names: Default::default(),
 993             region_index: 0,
 994             binder_depth: 0,
 995             region_highlight_mode: RegionHighlightMode::default(),
 996             name_resolver: None,
 997         }))
 998     }
 999 }
1000
1001 impl TyCtxt<'_> {
1002     // HACK(eddyb) get rid of `def_path_str` and/or pass `Namespace` explicitly always
1003     // (but also some things just print a `DefId` generally so maybe we need this?)
1004     fn guess_def_namespace(self, def_id: DefId) -> Namespace {
1005         match self.def_key(def_id).disambiguated_data.data {
1006             DefPathData::TypeNs(..)
1007             | DefPathData::CrateRoot
1008             | DefPathData::ImplTrait => Namespace::TypeNS,
1009
1010             DefPathData::ValueNs(..)
1011             | DefPathData::AnonConst
1012             | DefPathData::ClosureExpr
1013             | DefPathData::Ctor => Namespace::ValueNS,
1014
1015             DefPathData::MacroNs(..) => Namespace::MacroNS,
1016
1017             _ => Namespace::TypeNS,
1018         }
1019     }
1020
1021     /// Returns a string identifying this `DefId`. This string is
1022     /// suitable for user output.
1023     pub fn def_path_str(self, def_id: DefId) -> String {
1024         let ns = self.guess_def_namespace(def_id);
1025         debug!("def_path_str: def_id={:?}, ns={:?}", def_id, ns);
1026         let mut s = String::new();
1027         let _ = FmtPrinter::new(self, &mut s, ns)
1028             .print_def_path(def_id, &[]);
1029         s
1030     }
1031 }
1032
1033 impl<F: fmt::Write> fmt::Write for FmtPrinter<'_, '_, F> {
1034     fn write_str(&mut self, s: &str) -> fmt::Result {
1035         self.fmt.write_str(s)
1036     }
1037 }
1038
1039 impl<F: fmt::Write> Printer<'tcx> for FmtPrinter<'_, 'tcx, F> {
1040     type Error = fmt::Error;
1041
1042     type Path = Self;
1043     type Region = Self;
1044     type Type = Self;
1045     type DynExistential = Self;
1046     type Const = Self;
1047
1048     fn tcx(&'a self) -> TyCtxt<'tcx> {
1049         self.tcx
1050     }
1051
1052     fn print_def_path(
1053         mut self,
1054         def_id: DefId,
1055         substs: &'tcx [Kind<'tcx>],
1056     ) -> Result<Self::Path, Self::Error> {
1057         define_scoped_cx!(self);
1058
1059         if substs.is_empty() {
1060             match self.try_print_visible_def_path(def_id)? {
1061                 (cx, true) => return Ok(cx),
1062                 (cx, false) => self = cx,
1063             }
1064         }
1065
1066         let key = self.tcx.def_key(def_id);
1067         if let DefPathData::Impl = key.disambiguated_data.data {
1068             // Always use types for non-local impls, where types are always
1069             // available, and filename/line-number is mostly uninteresting.
1070             let use_types =
1071                 !def_id.is_local() || {
1072                     // Otherwise, use filename/line-number if forced.
1073                     let force_no_types = FORCE_IMPL_FILENAME_LINE.with(|f| f.get());
1074                     !force_no_types
1075                 };
1076
1077             if !use_types {
1078                 // If no type info is available, fall back to
1079                 // pretty printing some span information. This should
1080                 // only occur very early in the compiler pipeline.
1081                 let parent_def_id = DefId { index: key.parent.unwrap(), ..def_id };
1082                 let span = self.tcx.def_span(def_id);
1083
1084                 self = self.print_def_path(parent_def_id, &[])?;
1085
1086                 // HACK(eddyb) copy of `path_append` to avoid
1087                 // constructing a `DisambiguatedDefPathData`.
1088                 if !self.empty_path {
1089                     write!(self, "::")?;
1090                 }
1091                 write!(self, "<impl at {:?}>", span)?;
1092                 self.empty_path = false;
1093
1094                 return Ok(self);
1095             }
1096         }
1097
1098         self.default_print_def_path(def_id, substs)
1099     }
1100
1101     fn print_region(
1102         self,
1103         region: ty::Region<'_>,
1104     ) -> Result<Self::Region, Self::Error> {
1105         self.pretty_print_region(region)
1106     }
1107
1108     fn print_type(
1109         self,
1110         ty: Ty<'tcx>,
1111     ) -> Result<Self::Type, Self::Error> {
1112         self.pretty_print_type(ty)
1113     }
1114
1115     fn print_dyn_existential(
1116         self,
1117         predicates: &'tcx ty::List<ty::ExistentialPredicate<'tcx>>,
1118     ) -> Result<Self::DynExistential, Self::Error> {
1119         self.pretty_print_dyn_existential(predicates)
1120     }
1121
1122     fn print_const(
1123         self,
1124         ct: &'tcx ty::Const<'tcx>,
1125     ) -> Result<Self::Const, Self::Error> {
1126         self.pretty_print_const(ct)
1127     }
1128
1129     fn path_crate(
1130         mut self,
1131         cnum: CrateNum,
1132     ) -> Result<Self::Path, Self::Error> {
1133         self.empty_path = true;
1134         if cnum == LOCAL_CRATE {
1135             if self.tcx.sess.rust_2018() {
1136                 // We add the `crate::` keyword on Rust 2018, only when desired.
1137                 if SHOULD_PREFIX_WITH_CRATE.with(|flag| flag.get()) {
1138                     write!(self, "{}", kw::Crate)?;
1139                     self.empty_path = false;
1140                 }
1141             }
1142         } else {
1143             write!(self, "{}", self.tcx.crate_name(cnum))?;
1144             self.empty_path = false;
1145         }
1146         Ok(self)
1147     }
1148     fn path_qualified(
1149         mut self,
1150         self_ty: Ty<'tcx>,
1151         trait_ref: Option<ty::TraitRef<'tcx>>,
1152     ) -> Result<Self::Path, Self::Error> {
1153         self = self.pretty_path_qualified(self_ty, trait_ref)?;
1154         self.empty_path = false;
1155         Ok(self)
1156     }
1157
1158     fn path_append_impl(
1159         mut self,
1160         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1161         _disambiguated_data: &DisambiguatedDefPathData,
1162         self_ty: Ty<'tcx>,
1163         trait_ref: Option<ty::TraitRef<'tcx>>,
1164     ) -> Result<Self::Path, Self::Error> {
1165         self = self.pretty_path_append_impl(|mut cx| {
1166             cx = print_prefix(cx)?;
1167             if !cx.empty_path {
1168                 write!(cx, "::")?;
1169             }
1170
1171             Ok(cx)
1172         }, self_ty, trait_ref)?;
1173         self.empty_path = false;
1174         Ok(self)
1175     }
1176     fn path_append(
1177         mut self,
1178         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1179         disambiguated_data: &DisambiguatedDefPathData,
1180     ) -> Result<Self::Path, Self::Error> {
1181         self = print_prefix(self)?;
1182
1183         // Skip `::{{constructor}}` on tuple/unit structs.
1184         match disambiguated_data.data {
1185             DefPathData::Ctor => return Ok(self),
1186             _ => {}
1187         }
1188
1189         // FIXME(eddyb) `name` should never be empty, but it
1190         // currently is for `extern { ... }` "foreign modules".
1191         let name = disambiguated_data.data.as_interned_str().as_str();
1192         if !name.is_empty() {
1193             if !self.empty_path {
1194                 write!(self, "::")?;
1195             }
1196             write!(self, "{}", name)?;
1197
1198             // FIXME(eddyb) this will print e.g. `{{closure}}#3`, but it
1199             // might be nicer to use something else, e.g. `{closure#3}`.
1200             let dis = disambiguated_data.disambiguator;
1201             let print_dis =
1202                 disambiguated_data.data.get_opt_name().is_none() ||
1203                 dis != 0 && self.tcx.sess.verbose();
1204             if print_dis {
1205                 write!(self, "#{}", dis)?;
1206             }
1207
1208             self.empty_path = false;
1209         }
1210
1211         Ok(self)
1212     }
1213     fn path_generic_args(
1214         mut self,
1215         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1216         args: &[Kind<'tcx>],
1217     ) -> Result<Self::Path, Self::Error> {
1218         self = print_prefix(self)?;
1219
1220         // Don't print `'_` if there's no unerased regions.
1221         let print_regions = args.iter().any(|arg| {
1222             match arg.unpack() {
1223                 UnpackedKind::Lifetime(r) => *r != ty::ReErased,
1224                 _ => false,
1225             }
1226         });
1227         let args = args.iter().cloned().filter(|arg| {
1228             match arg.unpack() {
1229                 UnpackedKind::Lifetime(_) => print_regions,
1230                 _ => true,
1231             }
1232         });
1233
1234         if args.clone().next().is_some() {
1235             if self.in_value {
1236                 write!(self, "::")?;
1237             }
1238             self.generic_delimiters(|cx| cx.comma_sep(args))
1239         } else {
1240             Ok(self)
1241         }
1242     }
1243 }
1244
1245 impl<F: fmt::Write> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx, F> {
1246     fn infer_ty_name(&self, id: ty::TyVid) -> Option<String> {
1247         self.0.name_resolver.as_ref().and_then(|func| func(id))
1248     }
1249
1250     fn print_value_path(
1251         mut self,
1252         def_id: DefId,
1253         substs: &'tcx [Kind<'tcx>],
1254     ) -> Result<Self::Path, Self::Error> {
1255         let was_in_value = std::mem::replace(&mut self.in_value, true);
1256         self = self.print_def_path(def_id, substs)?;
1257         self.in_value = was_in_value;
1258
1259         Ok(self)
1260     }
1261
1262     fn in_binder<T>(self, value: &ty::Binder<T>) -> Result<Self, Self::Error>
1263     where
1264         T: Print<'tcx, Self, Output = Self, Error = Self::Error> + TypeFoldable<'tcx>,
1265     {
1266         self.pretty_in_binder(value)
1267     }
1268
1269     fn generic_delimiters(
1270         mut self,
1271         f: impl FnOnce(Self) -> Result<Self, Self::Error>,
1272     ) -> Result<Self, Self::Error> {
1273         write!(self, "<")?;
1274
1275         let was_in_value = std::mem::replace(&mut self.in_value, false);
1276         let mut inner = f(self)?;
1277         inner.in_value = was_in_value;
1278
1279         write!(inner, ">")?;
1280         Ok(inner)
1281     }
1282
1283     fn region_should_not_be_omitted(
1284         &self,
1285         region: ty::Region<'_>,
1286     ) -> bool {
1287         let highlight = self.region_highlight_mode;
1288         if highlight.region_highlighted(region).is_some() {
1289             return true;
1290         }
1291
1292         if self.tcx.sess.verbose() {
1293             return true;
1294         }
1295
1296         let identify_regions = self.tcx.sess.opts.debugging_opts.identify_regions;
1297
1298         match *region {
1299             ty::ReEarlyBound(ref data) => {
1300                 data.name.as_symbol() != kw::Invalid &&
1301                 data.name.as_symbol() != kw::UnderscoreLifetime
1302             }
1303
1304             ty::ReLateBound(_, br) |
1305             ty::ReFree(ty::FreeRegion { bound_region: br, .. }) |
1306             ty::RePlaceholder(ty::Placeholder { name: br, .. }) => {
1307                 if let ty::BrNamed(_, name) = br {
1308                     if name.as_symbol() != kw::Invalid &&
1309                        name.as_symbol() != kw::UnderscoreLifetime {
1310                         return true;
1311                     }
1312                 }
1313
1314                 if let Some((region, _)) = highlight.highlight_bound_region {
1315                     if br == region {
1316                         return true;
1317                     }
1318                 }
1319
1320                 false
1321             }
1322
1323             ty::ReScope(_) |
1324             ty::ReVar(_) if identify_regions => true,
1325
1326             ty::ReVar(_) |
1327             ty::ReScope(_) |
1328             ty::ReErased => false,
1329
1330             ty::ReStatic |
1331             ty::ReEmpty |
1332             ty::ReClosureBound(_) => true,
1333         }
1334     }
1335 }
1336
1337 // HACK(eddyb) limited to `FmtPrinter` because of `region_highlight_mode`.
1338 impl<F: fmt::Write> FmtPrinter<'_, '_, F> {
1339     pub fn pretty_print_region(
1340         mut self,
1341         region: ty::Region<'_>,
1342     ) -> Result<Self, fmt::Error> {
1343         define_scoped_cx!(self);
1344
1345         // Watch out for region highlights.
1346         let highlight = self.region_highlight_mode;
1347         if let Some(n) = highlight.region_highlighted(region) {
1348             p!(write("'{}", n));
1349             return Ok(self);
1350         }
1351
1352         if self.tcx.sess.verbose() {
1353             p!(write("{:?}", region));
1354             return Ok(self);
1355         }
1356
1357         let identify_regions = self.tcx.sess.opts.debugging_opts.identify_regions;
1358
1359         // These printouts are concise.  They do not contain all the information
1360         // the user might want to diagnose an error, but there is basically no way
1361         // to fit that into a short string.  Hence the recommendation to use
1362         // `explain_region()` or `note_and_explain_region()`.
1363         match *region {
1364             ty::ReEarlyBound(ref data) => {
1365                 if data.name.as_symbol() != kw::Invalid {
1366                     p!(write("{}", data.name));
1367                     return Ok(self);
1368                 }
1369             }
1370             ty::ReLateBound(_, br) |
1371             ty::ReFree(ty::FreeRegion { bound_region: br, .. }) |
1372             ty::RePlaceholder(ty::Placeholder { name: br, .. }) => {
1373                 if let ty::BrNamed(_, name) = br {
1374                     if name.as_symbol() != kw::Invalid &&
1375                        name.as_symbol() != kw::UnderscoreLifetime {
1376                         p!(write("{}", name));
1377                         return Ok(self);
1378                     }
1379                 }
1380
1381                 if let Some((region, counter)) = highlight.highlight_bound_region {
1382                     if br == region {
1383                         p!(write("'{}", counter));
1384                         return Ok(self);
1385                     }
1386                 }
1387             }
1388             ty::ReScope(scope) if identify_regions => {
1389                 match scope.data {
1390                     region::ScopeData::Node =>
1391                         p!(write("'{}s", scope.item_local_id().as_usize())),
1392                     region::ScopeData::CallSite =>
1393                         p!(write("'{}cs", scope.item_local_id().as_usize())),
1394                     region::ScopeData::Arguments =>
1395                         p!(write("'{}as", scope.item_local_id().as_usize())),
1396                     region::ScopeData::Destruction =>
1397                         p!(write("'{}ds", scope.item_local_id().as_usize())),
1398                     region::ScopeData::Remainder(first_statement_index) => p!(write(
1399                         "'{}_{}rs",
1400                         scope.item_local_id().as_usize(),
1401                         first_statement_index.index()
1402                     )),
1403                 }
1404                 return Ok(self);
1405             }
1406             ty::ReVar(region_vid) if identify_regions => {
1407                 p!(write("{:?}", region_vid));
1408                 return Ok(self);
1409             }
1410             ty::ReVar(_) => {}
1411             ty::ReScope(_) |
1412             ty::ReErased => {}
1413             ty::ReStatic => {
1414                 p!(write("'static"));
1415                 return Ok(self);
1416             }
1417             ty::ReEmpty => {
1418                 p!(write("'<empty>"));
1419                 return Ok(self);
1420             }
1421
1422             // The user should never encounter these in unsubstituted form.
1423             ty::ReClosureBound(vid) => {
1424                 p!(write("{:?}", vid));
1425                 return Ok(self);
1426             }
1427         }
1428
1429         p!(write("'_"));
1430
1431         Ok(self)
1432     }
1433 }
1434
1435 // HACK(eddyb) limited to `FmtPrinter` because of `binder_depth`,
1436 // `region_index` and `used_region_names`.
1437 impl<F: fmt::Write> FmtPrinter<'_, 'tcx, F> {
1438     pub fn pretty_in_binder<T>(mut self, value: &ty::Binder<T>) -> Result<Self, fmt::Error>
1439     where
1440         T: Print<'tcx, Self, Output = Self, Error = fmt::Error> + TypeFoldable<'tcx>,
1441     {
1442         fn name_by_region_index(index: usize) -> InternedString {
1443             match index {
1444                 0 => InternedString::intern("'r"),
1445                 1 => InternedString::intern("'s"),
1446                 i => InternedString::intern(&format!("'t{}", i-2)),
1447             }
1448         }
1449
1450         // Replace any anonymous late-bound regions with named
1451         // variants, using gensym'd identifiers, so that we can
1452         // clearly differentiate between named and unnamed regions in
1453         // the output. We'll probably want to tweak this over time to
1454         // decide just how much information to give.
1455         if self.binder_depth == 0 {
1456             self.prepare_late_bound_region_info(value);
1457         }
1458
1459         let mut empty = true;
1460         let mut start_or_continue = |cx: &mut Self, start: &str, cont: &str| {
1461             write!(cx, "{}", if empty {
1462                 empty = false;
1463                 start
1464             } else {
1465                 cont
1466             })
1467         };
1468
1469         define_scoped_cx!(self);
1470
1471         let old_region_index = self.region_index;
1472         let mut region_index = old_region_index;
1473         let new_value = self.tcx.replace_late_bound_regions(value, |br| {
1474             let _ = start_or_continue(&mut self, "for<", ", ");
1475             let br = match br {
1476                 ty::BrNamed(_, name) => {
1477                     let _ = write!(self, "{}", name);
1478                     br
1479                 }
1480                 ty::BrAnon(_) |
1481                 ty::BrEnv => {
1482                     let name = loop {
1483                         let name = name_by_region_index(region_index);
1484                         region_index += 1;
1485                         if !self.used_region_names.contains(&name) {
1486                             break name;
1487                         }
1488                     };
1489                     let _ = write!(self, "{}", name);
1490                     ty::BrNamed(DefId::local(CRATE_DEF_INDEX), name)
1491                 }
1492             };
1493             self.tcx.mk_region(ty::ReLateBound(ty::INNERMOST, br))
1494         }).0;
1495         start_or_continue(&mut self, "", "> ")?;
1496
1497         self.binder_depth += 1;
1498         self.region_index = region_index;
1499         let mut inner = new_value.print(self)?;
1500         inner.region_index = old_region_index;
1501         inner.binder_depth -= 1;
1502         Ok(inner)
1503     }
1504
1505     fn prepare_late_bound_region_info<T>(&mut self, value: &ty::Binder<T>)
1506         where T: TypeFoldable<'tcx>
1507     {
1508
1509         struct LateBoundRegionNameCollector<'a>(&'a mut FxHashSet<InternedString>);
1510         impl<'tcx> ty::fold::TypeVisitor<'tcx> for LateBoundRegionNameCollector<'_> {
1511             fn visit_region(&mut self, r: ty::Region<'tcx>) -> bool {
1512                 match *r {
1513                     ty::ReLateBound(_, ty::BrNamed(_, name)) => {
1514                         self.0.insert(name);
1515                     },
1516                     _ => {},
1517                 }
1518                 r.super_visit_with(self)
1519             }
1520         }
1521
1522         self.used_region_names.clear();
1523         let mut collector = LateBoundRegionNameCollector(&mut self.used_region_names);
1524         value.visit_with(&mut collector);
1525         self.region_index = 0;
1526     }
1527 }
1528
1529 impl<'tcx, T, P: PrettyPrinter<'tcx>> Print<'tcx, P> for ty::Binder<T>
1530 where
1531     T: Print<'tcx, P, Output = P, Error = P::Error> + TypeFoldable<'tcx>,
1532 {
1533     type Output = P;
1534     type Error = P::Error;
1535     fn print(&self, cx: P) -> Result<Self::Output, Self::Error> {
1536         cx.in_binder(self)
1537     }
1538 }
1539
1540 impl<'tcx, T, U, P: PrettyPrinter<'tcx>> Print<'tcx, P> for ty::OutlivesPredicate<T, U>
1541 where
1542     T: Print<'tcx, P, Output = P, Error = P::Error>,
1543     U: Print<'tcx, P, Output = P, Error = P::Error>,
1544 {
1545     type Output = P;
1546     type Error = P::Error;
1547     fn print(&self, mut cx: P) -> Result<Self::Output, Self::Error> {
1548         define_scoped_cx!(cx);
1549         p!(print(self.0), write(" : "), print(self.1));
1550         Ok(cx)
1551     }
1552 }
1553
1554 macro_rules! forward_display_to_print {
1555     ($($ty:ty),+) => {
1556         $(impl fmt::Display for $ty {
1557             fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1558                 ty::tls::with(|tcx| {
1559                     tcx.lift(self)
1560                         .expect("could not lift for printing")
1561                         .print(FmtPrinter::new(tcx, f, Namespace::TypeNS))?;
1562                     Ok(())
1563                 })
1564             }
1565         })+
1566     };
1567 }
1568
1569 macro_rules! define_print_and_forward_display {
1570     (($self:ident, $cx:ident): $($ty:ty $print:block)+) => {
1571         $(impl<'tcx, P: PrettyPrinter<'tcx>> Print<'tcx, P> for $ty {
1572             type Output = P;
1573             type Error = fmt::Error;
1574             fn print(&$self, $cx: P) -> Result<Self::Output, Self::Error> {
1575                 #[allow(unused_mut)]
1576                 let mut $cx = $cx;
1577                 define_scoped_cx!($cx);
1578                 let _: () = $print;
1579                 #[allow(unreachable_code)]
1580                 Ok($cx)
1581             }
1582         })+
1583
1584         forward_display_to_print!($($ty),+);
1585     };
1586 }
1587
1588 // HACK(eddyb) this is separate because `ty::RegionKind` doesn't need lifting.
1589 impl fmt::Display for ty::RegionKind {
1590     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1591         ty::tls::with(|tcx| {
1592             self.print(FmtPrinter::new(tcx, f, Namespace::TypeNS))?;
1593             Ok(())
1594         })
1595     }
1596 }
1597
1598 forward_display_to_print! {
1599     Ty<'tcx>,
1600     &'tcx ty::List<ty::ExistentialPredicate<'tcx>>,
1601     &'tcx ty::Const<'tcx>,
1602
1603     // HACK(eddyb) these are exhaustive instead of generic,
1604     // because `for<'tcx>` isn't possible yet.
1605     ty::Binder<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>,
1606     ty::Binder<ty::TraitRef<'tcx>>,
1607     ty::Binder<ty::FnSig<'tcx>>,
1608     ty::Binder<ty::TraitPredicate<'tcx>>,
1609     ty::Binder<ty::SubtypePredicate<'tcx>>,
1610     ty::Binder<ty::ProjectionPredicate<'tcx>>,
1611     ty::Binder<ty::OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>>,
1612     ty::Binder<ty::OutlivesPredicate<ty::Region<'tcx>, ty::Region<'tcx>>>,
1613
1614     ty::OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>,
1615     ty::OutlivesPredicate<ty::Region<'tcx>, ty::Region<'tcx>>
1616 }
1617
1618 define_print_and_forward_display! {
1619     (self, cx):
1620
1621     &'tcx ty::List<Ty<'tcx>> {
1622         p!(write("{{"));
1623         let mut tys = self.iter();
1624         if let Some(&ty) = tys.next() {
1625             p!(print(ty));
1626             for &ty in tys {
1627                 p!(write(", "), print(ty));
1628             }
1629         }
1630         p!(write("}}"))
1631     }
1632
1633     ty::TypeAndMut<'tcx> {
1634         p!(write("{}", if self.mutbl == hir::MutMutable { "mut " } else { "" }),
1635             print(self.ty))
1636     }
1637
1638     ty::ExistentialTraitRef<'tcx> {
1639         // Use a type that can't appear in defaults of type parameters.
1640         let dummy_self = cx.tcx().mk_ty_infer(ty::FreshTy(0));
1641         let trait_ref = self.with_self_ty(cx.tcx(), dummy_self);
1642         p!(print(trait_ref))
1643     }
1644
1645     ty::ExistentialProjection<'tcx> {
1646         let name = cx.tcx().associated_item(self.item_def_id).ident;
1647         p!(write("{} = ", name), print(self.ty))
1648     }
1649
1650     ty::ExistentialPredicate<'tcx> {
1651         match *self {
1652             ty::ExistentialPredicate::Trait(x) => p!(print(x)),
1653             ty::ExistentialPredicate::Projection(x) => p!(print(x)),
1654             ty::ExistentialPredicate::AutoTrait(def_id) => {
1655                 p!(print_def_path(def_id, &[]));
1656             }
1657         }
1658     }
1659
1660     ty::FnSig<'tcx> {
1661         if self.unsafety == hir::Unsafety::Unsafe {
1662             p!(write("unsafe "));
1663         }
1664
1665         if self.abi != Abi::Rust {
1666             p!(write("extern {} ", self.abi));
1667         }
1668
1669         p!(write("fn"), pretty_fn_sig(self.inputs(), self.c_variadic, self.output()));
1670     }
1671
1672     ty::InferTy {
1673         if cx.tcx().sess.verbose() {
1674             p!(write("{:?}", self));
1675             return Ok(cx);
1676         }
1677         match *self {
1678             ty::TyVar(_) => p!(write("_")),
1679             ty::IntVar(_) => p!(write("{}", "{integer}")),
1680             ty::FloatVar(_) => p!(write("{}", "{float}")),
1681             ty::FreshTy(v) => p!(write("FreshTy({})", v)),
1682             ty::FreshIntTy(v) => p!(write("FreshIntTy({})", v)),
1683             ty::FreshFloatTy(v) => p!(write("FreshFloatTy({})", v))
1684         }
1685     }
1686
1687     ty::TraitRef<'tcx> {
1688         p!(print_def_path(self.def_id, self.substs));
1689     }
1690
1691     ty::ParamTy {
1692         p!(write("{}", self.name))
1693     }
1694
1695     ty::ParamConst {
1696         p!(write("{}", self.name))
1697     }
1698
1699     ty::SubtypePredicate<'tcx> {
1700         p!(print(self.a), write(" <: "), print(self.b))
1701     }
1702
1703     ty::TraitPredicate<'tcx> {
1704         p!(print(self.trait_ref.self_ty()), write(": "), print(self.trait_ref))
1705     }
1706
1707     ty::ProjectionPredicate<'tcx> {
1708         p!(print(self.projection_ty), write(" == "), print(self.ty))
1709     }
1710
1711     ty::ProjectionTy<'tcx> {
1712         p!(print_def_path(self.item_def_id, self.substs));
1713     }
1714
1715     ty::ClosureKind {
1716         match *self {
1717             ty::ClosureKind::Fn => p!(write("Fn")),
1718             ty::ClosureKind::FnMut => p!(write("FnMut")),
1719             ty::ClosureKind::FnOnce => p!(write("FnOnce")),
1720         }
1721     }
1722
1723     ty::Predicate<'tcx> {
1724         match *self {
1725             ty::Predicate::Trait(ref data) => p!(print(data)),
1726             ty::Predicate::Subtype(ref predicate) => p!(print(predicate)),
1727             ty::Predicate::RegionOutlives(ref predicate) => p!(print(predicate)),
1728             ty::Predicate::TypeOutlives(ref predicate) => p!(print(predicate)),
1729             ty::Predicate::Projection(ref predicate) => p!(print(predicate)),
1730             ty::Predicate::WellFormed(ty) => p!(print(ty), write(" well-formed")),
1731             ty::Predicate::ObjectSafe(trait_def_id) => {
1732                 p!(write("the trait `"),
1733                    print_def_path(trait_def_id, &[]),
1734                    write("` is object-safe"))
1735             }
1736             ty::Predicate::ClosureKind(closure_def_id, _closure_substs, kind) => {
1737                 p!(write("the closure `"),
1738                    print_value_path(closure_def_id, &[]),
1739                    write("` implements the trait `{}`", kind))
1740             }
1741             ty::Predicate::ConstEvaluatable(def_id, substs) => {
1742                 p!(write("the constant `"),
1743                    print_value_path(def_id, substs),
1744                    write("` can be evaluated"))
1745             }
1746         }
1747     }
1748
1749     Kind<'tcx> {
1750         match self.unpack() {
1751             UnpackedKind::Lifetime(lt) => p!(print(lt)),
1752             UnpackedKind::Type(ty) => p!(print(ty)),
1753             UnpackedKind::Const(ct) => p!(print(ct)),
1754         }
1755     }
1756 }