compiler/rustc_middle/src/ty/print/pretty.rs

   1 use crate::mir::interpret::{AllocRange, GlobalAlloc, Pointer, Provenance, Scalar};
   2 use crate::ty::{
   3     self, ConstInt, DefIdTree, ParamConst, ScalarInt, Term, TermKind, Ty, TyCtxt, TypeFoldable,
   4     TypeSuperFoldable, TypeSuperVisitable, TypeVisitable,
   5 };
   6 use crate::ty::{GenericArg, GenericArgKind};
   7 use rustc_apfloat::ieee::{Double, Single};
   8 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
   9 use rustc_data_structures::sso::SsoHashSet;
  10 use rustc_hir as hir;
  11 use rustc_hir::def::{self, CtorKind, DefKind, Namespace};
  12 use rustc_hir::def_id::{DefId, DefIdSet, CRATE_DEF_ID, LOCAL_CRATE};
  13 use rustc_hir::definitions::{DefKey, DefPathData, DefPathDataName, DisambiguatedDefPathData};
  14 use rustc_hir::LangItem;
  15 use rustc_session::config::TrimmedDefPaths;
  16 use rustc_session::cstore::{ExternCrate, ExternCrateSource};
  17 use rustc_session::Limit;
  18 use rustc_span::symbol::{kw, Ident, Symbol};
  19 use rustc_span::FileNameDisplayPreference;
  20 use rustc_target::abi::Size;
  21 use rustc_target::spec::abi::Abi;
  22 use smallvec::SmallVec;
  23
  24 use std::cell::Cell;
  25 use std::char;
  26 use std::collections::BTreeMap;
  27 use std::fmt::{self, Write as _};
  28 use std::iter;
  29 use std::ops::{ControlFlow, Deref, DerefMut};
  30
  31 // `pretty` is a separate module only for organization.
  32 use super::*;
  33
  34 macro_rules! p {
  35     (@$lit:literal) => {
  36         write!(scoped_cx!(), $lit)?
  37     };
  38     (@write($($data:expr),+)) => {
  39         write!(scoped_cx!(), $($data),+)?
  40     };
  41     (@print($x:expr)) => {
  42         scoped_cx!() = $x.print(scoped_cx!())?
  43     };
  44     (@$method:ident($($arg:expr),*)) => {
  45         scoped_cx!() = scoped_cx!().$method($($arg),*)?
  46     };
  47     ($($elem:tt $(($($args:tt)*))?),+) => {{
  48         $(p!(@ $elem $(($($args)*))?);)+
  49     }};
  50 }
  51 macro_rules! define_scoped_cx {
  52     ($cx:ident) => {
  53         #[allow(unused_macros)]
  54         macro_rules! scoped_cx {
  55             () => {
  56                 $cx
  57             };
  58         }
  59     };
  60 }
  61
  62 thread_local! {
  63     static FORCE_IMPL_FILENAME_LINE: Cell<bool> = const { Cell::new(false) };
  64     static SHOULD_PREFIX_WITH_CRATE: Cell<bool> = const { Cell::new(false) };
  65     static NO_TRIMMED_PATH: Cell<bool> = const { Cell::new(false) };
  66     static FORCE_TRIMMED_PATH: Cell<bool> = const { Cell::new(false) };
  67     static NO_QUERIES: Cell<bool> = const { Cell::new(false) };
  68     static NO_VISIBLE_PATH: Cell<bool> = const { Cell::new(false) };
  69 }
  70
  71 macro_rules! define_helper {
  72     ($($(#[$a:meta])* fn $name:ident($helper:ident, $tl:ident);)+) => {
  73         $(
  74             #[must_use]
  75             pub struct $helper(bool);
  76
  77             impl $helper {
  78                 pub fn new() -> $helper {
  79                     $helper($tl.with(|c| c.replace(true)))
  80                 }
  81             }
  82
  83             $(#[$a])*
  84             pub macro $name($e:expr) {
  85                 {
  86                     let _guard = $helper::new();
  87                     $e
  88                 }
  89             }
  90
  91             impl Drop for $helper {
  92                 fn drop(&mut self) {
  93                     $tl.with(|c| c.set(self.0))
  94                 }
  95             }
  96         )+
  97     }
  98 }
  99
 100 define_helper!(
 101     /// Avoids running any queries during any prints that occur
 102     /// during the closure. This may alter the appearance of some
 103     /// types (e.g. forcing verbose printing for opaque types).
 104     /// This method is used during some queries (e.g. `explicit_item_bounds`
 105     /// for opaque types), to ensure that any debug printing that
 106     /// occurs during the query computation does not end up recursively
 107     /// calling the same query.
 108     fn with_no_queries(NoQueriesGuard, NO_QUERIES);
 109     /// Force us to name impls with just the filename/line number. We
 110     /// normally try to use types. But at some points, notably while printing
 111     /// cycle errors, this can result in extra or suboptimal error output,
 112     /// so this variable disables that check.
 113     fn with_forced_impl_filename_line(ForcedImplGuard, FORCE_IMPL_FILENAME_LINE);
 114     /// Adds the `crate::` prefix to paths where appropriate.
 115     fn with_crate_prefix(CratePrefixGuard, SHOULD_PREFIX_WITH_CRATE);
 116     /// Prevent path trimming if it is turned on. Path trimming affects `Display` impl
 117     /// of various rustc types, for example `std::vec::Vec` would be trimmed to `Vec`,
 118     /// if no other `Vec` is found.
 119     fn with_no_trimmed_paths(NoTrimmedGuard, NO_TRIMMED_PATH);
 120     fn with_forced_trimmed_paths(ForceTrimmedGuard, FORCE_TRIMMED_PATH);
 121     /// Prevent selection of visible paths. `Display` impl of DefId will prefer
 122     /// visible (public) reexports of types as paths.
 123     fn with_no_visible_paths(NoVisibleGuard, NO_VISIBLE_PATH);
 124 );
 125
 126 /// The "region highlights" are used to control region printing during
 127 /// specific error messages. When a "region highlight" is enabled, it
 128 /// gives an alternate way to print specific regions. For now, we
 129 /// always print those regions using a number, so something like "`'0`".
 130 ///
 131 /// Regions not selected by the region highlight mode are presently
 132 /// unaffected.
 133 #[derive(Copy, Clone)]
 134 pub struct RegionHighlightMode<'tcx> {
 135     tcx: TyCtxt<'tcx>,
 136
 137     /// If enabled, when we see the selected region, use "`'N`"
 138     /// instead of the ordinary behavior.
 139     highlight_regions: [Option<(ty::Region<'tcx>, usize)>; 3],
 140
 141     /// If enabled, when printing a "free region" that originated from
 142     /// the given `ty::BoundRegionKind`, print it as "`'1`". Free regions that would ordinarily
 143     /// have names print as normal.
 144     ///
 145     /// This is used when you have a signature like `fn foo(x: &u32,
 146     /// y: &'a u32)` and we want to give a name to the region of the
 147     /// reference `x`.
 148     highlight_bound_region: Option<(ty::BoundRegionKind, usize)>,
 149 }
 150
 151 impl<'tcx> RegionHighlightMode<'tcx> {
 152     pub fn new(tcx: TyCtxt<'tcx>) -> Self {
 153         Self {
 154             tcx,
 155             highlight_regions: Default::default(),
 156             highlight_bound_region: Default::default(),
 157         }
 158     }
 159
 160     /// If `region` and `number` are both `Some`, invokes
 161     /// `highlighting_region`.
 162     pub fn maybe_highlighting_region(
 163         &mut self,
 164         region: Option<ty::Region<'tcx>>,
 165         number: Option<usize>,
 166     ) {
 167         if let Some(k) = region {
 168             if let Some(n) = number {
 169                 self.highlighting_region(k, n);
 170             }
 171         }
 172     }
 173
 174     /// Highlights the region inference variable `vid` as `'N`.
 175     pub fn highlighting_region(&mut self, region: ty::Region<'tcx>, number: usize) {
 176         let num_slots = self.highlight_regions.len();
 177         let first_avail_slot =
 178             self.highlight_regions.iter_mut().find(|s| s.is_none()).unwrap_or_else(|| {
 179                 bug!("can only highlight {} placeholders at a time", num_slots,)
 180             });
 181         *first_avail_slot = Some((region, number));
 182     }
 183
 184     /// Convenience wrapper for `highlighting_region`.
 185     pub fn highlighting_region_vid(&mut self, vid: ty::RegionVid, number: usize) {
 186         self.highlighting_region(self.tcx.mk_region(ty::ReVar(vid)), number)
 187     }
 188
 189     /// Returns `Some(n)` with the number to use for the given region, if any.
 190     fn region_highlighted(&self, region: ty::Region<'tcx>) -> Option<usize> {
 191         self.highlight_regions.iter().find_map(|h| match h {
 192             Some((r, n)) if *r == region => Some(*n),
 193             _ => None,
 194         })
 195     }
 196
 197     /// Highlight the given bound region.
 198     /// We can only highlight one bound region at a time. See
 199     /// the field `highlight_bound_region` for more detailed notes.
 200     pub fn highlighting_bound_region(&mut self, br: ty::BoundRegionKind, number: usize) {
 201         assert!(self.highlight_bound_region.is_none());
 202         self.highlight_bound_region = Some((br, number));
 203     }
 204 }
 205
 206 /// Trait for printers that pretty-print using `fmt::Write` to the printer.
 207 pub trait PrettyPrinter<'tcx>:
 208     Printer<
 209         'tcx,
 210         Error = fmt::Error,
 211         Path = Self,
 212         Region = Self,
 213         Type = Self,
 214         DynExistential = Self,
 215         Const = Self,
 216     > + fmt::Write
 217 {
 218     /// Like `print_def_path` but for value paths.
 219     fn print_value_path(
 220         self,
 221         def_id: DefId,
 222         substs: &'tcx [GenericArg<'tcx>],
 223     ) -> Result<Self::Path, Self::Error> {
 224         self.print_def_path(def_id, substs)
 225     }
 226
 227     fn in_binder<T>(self, value: &ty::Binder<'tcx, T>) -> Result<Self, Self::Error>
 228     where
 229         T: Print<'tcx, Self, Output = Self, Error = Self::Error> + TypeFoldable<'tcx>,
 230     {
 231         value.as_ref().skip_binder().print(self)
 232     }
 233
 234     fn wrap_binder<T, F: FnOnce(&T, Self) -> Result<Self, fmt::Error>>(
 235         self,
 236         value: &ty::Binder<'tcx, T>,
 237         f: F,
 238     ) -> Result<Self, Self::Error>
 239     where
 240         T: Print<'tcx, Self, Output = Self, Error = Self::Error> + TypeFoldable<'tcx>,
 241     {
 242         f(value.as_ref().skip_binder(), self)
 243     }
 244
 245     /// Prints comma-separated elements.
 246     fn comma_sep<T>(mut self, mut elems: impl Iterator<Item = T>) -> Result<Self, Self::Error>
 247     where
 248         T: Print<'tcx, Self, Output = Self, Error = Self::Error>,
 249     {
 250         if let Some(first) = elems.next() {
 251             self = first.print(self)?;
 252             for elem in elems {
 253                 self.write_str(", ")?;
 254                 self = elem.print(self)?;
 255             }
 256         }
 257         Ok(self)
 258     }
 259
 260     /// Prints `{f: t}` or `{f as t}` depending on the `cast` argument
 261     fn typed_value(
 262         mut self,
 263         f: impl FnOnce(Self) -> Result<Self, Self::Error>,
 264         t: impl FnOnce(Self) -> Result<Self, Self::Error>,
 265         conversion: &str,
 266     ) -> Result<Self::Const, Self::Error> {
 267         self.write_str("{")?;
 268         self = f(self)?;
 269         self.write_str(conversion)?;
 270         self = t(self)?;
 271         self.write_str("}")?;
 272         Ok(self)
 273     }
 274
 275     /// Prints `<...>` around what `f` prints.
 276     fn generic_delimiters(
 277         self,
 278         f: impl FnOnce(Self) -> Result<Self, Self::Error>,
 279     ) -> Result<Self, Self::Error>;
 280
 281     /// Returns `true` if the region should be printed in
 282     /// optional positions, e.g., `&'a T` or `dyn Tr + 'b`.
 283     /// This is typically the case for all non-`'_` regions.
 284     fn should_print_region(&self, region: ty::Region<'tcx>) -> bool;
 285
 286     fn reset_type_limit(&mut self) {}
 287
 288     // Defaults (should not be overridden):
 289
 290     /// If possible, this returns a global path resolving to `def_id` that is visible
 291     /// from at least one local module, and returns `true`. If the crate defining `def_id` is
 292     /// declared with an `extern crate`, the path is guaranteed to use the `extern crate`.
 293     fn try_print_visible_def_path(self, def_id: DefId) -> Result<(Self, bool), Self::Error> {
 294         if NO_VISIBLE_PATH.with(|flag| flag.get()) {
 295             return Ok((self, false));
 296         }
 297
 298         let mut callers = Vec::new();
 299         self.try_print_visible_def_path_recur(def_id, &mut callers)
 300     }
 301
 302     // Given a `DefId`, produce a short name. For types and traits, it prints *only* its name,
 303     // For associated items on traits it prints out the trait's name and the associated item's name.
 304     // For enum variants, if they have an unique name, then we only print the name, otherwise we
 305     // print the enum name and the variant name. Otherwise, we do not print anything and let the
 306     // caller use the `print_def_path` fallback.
 307     fn force_print_trimmed_def_path(
 308         mut self,
 309         def_id: DefId,
 310     ) -> Result<(Self::Path, bool), Self::Error> {
 311         let key = self.tcx().def_key(def_id);
 312         let visible_parent_map = self.tcx().visible_parent_map(());
 313         let kind = self.tcx().def_kind(def_id);
 314
 315         let get_local_name = |this: &Self, name, def_id, key: DefKey| {
 316             if let Some(visible_parent) = visible_parent_map.get(&def_id)
 317                 && let actual_parent = this.tcx().opt_parent(def_id)
 318                 && let DefPathData::TypeNs(_) = key.disambiguated_data.data
 319                 && Some(*visible_parent) != actual_parent
 320             {
 321                 this
 322                     .tcx()
 323                     .module_children(visible_parent)
 324                     .iter()
 325                     .filter(|child| child.res.opt_def_id() == Some(def_id))
 326                     .find(|child| child.vis.is_public() && child.ident.name != kw::Underscore)
 327                     .map(|child| child.ident.name)
 328                     .unwrap_or(name)
 329             } else {
 330                 name
 331             }
 332         };
 333         if let DefKind::Variant = kind
 334             && let Some(symbol) = self.tcx().trimmed_def_paths(()).get(&def_id)
 335         {
 336             // If `Assoc` is unique, we don't want to talk about `Trait::Assoc`.
 337             self.write_str(get_local_name(&self, *symbol, def_id, key).as_str())?;
 338             return Ok((self, true));
 339         }
 340         if let Some(symbol) = key.get_opt_name() {
 341             if let DefKind::AssocConst | DefKind::AssocFn | DefKind::AssocTy = kind
 342                 && let Some(parent) = self.tcx().opt_parent(def_id)
 343                 && let parent_key = self.tcx().def_key(parent)
 344                 && let Some(symbol) = parent_key.get_opt_name()
 345             {
 346                 // Trait
 347                 self.write_str(get_local_name(&self, symbol, parent, parent_key).as_str())?;
 348                 self.write_str("::")?;
 349             } else if let DefKind::Variant = kind
 350                 && let Some(parent) = self.tcx().opt_parent(def_id)
 351                 && let parent_key = self.tcx().def_key(parent)
 352                 && let Some(symbol) = parent_key.get_opt_name()
 353             {
 354                 // Enum
 355
 356                 // For associated items and variants, we want the "full" path, namely, include
 357                 // the parent type in the path. For example, `Iterator::Item`.
 358                 self.write_str(get_local_name(&self, symbol, parent, parent_key).as_str())?;
 359                 self.write_str("::")?;
 360             } else if let DefKind::Struct | DefKind::Union | DefKind::Enum | DefKind::Trait
 361                 | DefKind::TyAlias | DefKind::Fn | DefKind::Const | DefKind::Static(_) = kind
 362             {
 363             } else {
 364                 // If not covered above, like for example items out of `impl` blocks, fallback.
 365                 return Ok((self, false));
 366             }
 367             self.write_str(get_local_name(&self, symbol, def_id, key).as_str())?;
 368             return Ok((self, true));
 369         }
 370         Ok((self, false))
 371     }
 372
 373     /// Try to see if this path can be trimmed to a unique symbol name.
 374     fn try_print_trimmed_def_path(
 375         mut self,
 376         def_id: DefId,
 377     ) -> Result<(Self::Path, bool), Self::Error> {
 378         if FORCE_TRIMMED_PATH.with(|flag| flag.get()) {
 379             let (s, trimmed) = self.force_print_trimmed_def_path(def_id)?;
 380             if trimmed {
 381                 return Ok((s, true));
 382             }
 383             self = s;
 384         }
 385         if !self.tcx().sess.opts.unstable_opts.trim_diagnostic_paths
 386             || matches!(self.tcx().sess.opts.trimmed_def_paths, TrimmedDefPaths::Never)
 387             || NO_TRIMMED_PATH.with(|flag| flag.get())
 388             || SHOULD_PREFIX_WITH_CRATE.with(|flag| flag.get())
 389         {
 390             return Ok((self, false));
 391         }
 392
 393         match self.tcx().trimmed_def_paths(()).get(&def_id) {
 394             None => Ok((self, false)),
 395             Some(symbol) => {
 396                 write!(self, "{}", Ident::with_dummy_span(*symbol))?;
 397                 Ok((self, true))
 398             }
 399         }
 400     }
 401
 402     /// Does the work of `try_print_visible_def_path`, building the
 403     /// full definition path recursively before attempting to
 404     /// post-process it into the valid and visible version that
 405     /// accounts for re-exports.
 406     ///
 407     /// This method should only be called by itself or
 408     /// `try_print_visible_def_path`.
 409     ///
 410     /// `callers` is a chain of visible_parent's leading to `def_id`,
 411     /// to support cycle detection during recursion.
 412     ///
 413     /// This method returns false if we can't print the visible path, so
 414     /// `print_def_path` can fall back on the item's real definition path.
 415     fn try_print_visible_def_path_recur(
 416         mut self,
 417         def_id: DefId,
 418         callers: &mut Vec<DefId>,
 419     ) -> Result<(Self, bool), Self::Error> {
 420         define_scoped_cx!(self);
 421
 422         debug!("try_print_visible_def_path: def_id={:?}", def_id);
 423
 424         // If `def_id` is a direct or injected extern crate, return the
 425         // path to the crate followed by the path to the item within the crate.
 426         if let Some(cnum) = def_id.as_crate_root() {
 427             if cnum == LOCAL_CRATE {
 428                 return Ok((self.path_crate(cnum)?, true));
 429             }
 430
 431             // In local mode, when we encounter a crate other than
 432             // LOCAL_CRATE, execution proceeds in one of two ways:
 433             //
 434             // 1. For a direct dependency, where user added an
 435             //    `extern crate` manually, we put the `extern
 436             //    crate` as the parent. So you wind up with
 437             //    something relative to the current crate.
 438             // 2. For an extern inferred from a path or an indirect crate,
 439             //    where there is no explicit `extern crate`, we just prepend
 440             //    the crate name.
 441             match self.tcx().extern_crate(def_id) {
 442                 Some(&ExternCrate { src, dependency_of, span, .. }) => match (src, dependency_of) {
 443                     (ExternCrateSource::Extern(def_id), LOCAL_CRATE) => {
 444                         // NOTE(eddyb) the only reason `span` might be dummy,
 445                         // that we're aware of, is that it's the `std`/`core`
 446                         // `extern crate` injected by default.
 447                         // FIXME(eddyb) find something better to key this on,
 448                         // or avoid ending up with `ExternCrateSource::Extern`,
 449                         // for the injected `std`/`core`.
 450                         if span.is_dummy() {
 451                             return Ok((self.path_crate(cnum)?, true));
 452                         }
 453
 454                         // Disable `try_print_trimmed_def_path` behavior within
 455                         // the `print_def_path` call, to avoid infinite recursion
 456                         // in cases where the `extern crate foo` has non-trivial
 457                         // parents, e.g. it's nested in `impl foo::Trait for Bar`
 458                         // (see also issues #55779 and #87932).
 459                         self = with_no_visible_paths!(self.print_def_path(def_id, &[])?);
 460
 461                         return Ok((self, true));
 462                     }
 463                     (ExternCrateSource::Path, LOCAL_CRATE) => {
 464                         return Ok((self.path_crate(cnum)?, true));
 465                     }
 466                     _ => {}
 467                 },
 468                 None => {
 469                     return Ok((self.path_crate(cnum)?, true));
 470                 }
 471             }
 472         }
 473
 474         if def_id.is_local() {
 475             return Ok((self, false));
 476         }
 477
 478         let visible_parent_map = self.tcx().visible_parent_map(());
 479
 480         let mut cur_def_key = self.tcx().def_key(def_id);
 481         debug!("try_print_visible_def_path: cur_def_key={:?}", cur_def_key);
 482
 483         // For a constructor, we want the name of its parent rather than <unnamed>.
 484         if let DefPathData::Ctor = cur_def_key.disambiguated_data.data {
 485             let parent = DefId {
 486                 krate: def_id.krate,
 487                 index: cur_def_key
 488                     .parent
 489                     .expect("`DefPathData::Ctor` / `VariantData` missing a parent"),
 490             };
 491
 492             cur_def_key = self.tcx().def_key(parent);
 493         }
 494
 495         let Some(visible_parent) = visible_parent_map.get(&def_id).cloned() else {
 496             return Ok((self, false));
 497         };
 498
 499         let actual_parent = self.tcx().opt_parent(def_id);
 500         debug!(
 501             "try_print_visible_def_path: visible_parent={:?} actual_parent={:?}",
 502             visible_parent, actual_parent,
 503         );
 504
 505         let mut data = cur_def_key.disambiguated_data.data;
 506         debug!(
 507             "try_print_visible_def_path: data={:?} visible_parent={:?} actual_parent={:?}",
 508             data, visible_parent, actual_parent,
 509         );
 510
 511         match data {
 512             // In order to output a path that could actually be imported (valid and visible),
 513             // we need to handle re-exports correctly.
 514             //
 515             // For example, take `std::os::unix::process::CommandExt`, this trait is actually
 516             // defined at `std::sys::unix::ext::process::CommandExt` (at time of writing).
 517             //
 518             // `std::os::unix` reexports the contents of `std::sys::unix::ext`. `std::sys` is
 519             // private so the "true" path to `CommandExt` isn't accessible.
 520             //
 521             // In this case, the `visible_parent_map` will look something like this:
 522             //
 523             // (child) -> (parent)
 524             // `std::sys::unix::ext::process::CommandExt` -> `std::sys::unix::ext::process`
 525             // `std::sys::unix::ext::process` -> `std::sys::unix::ext`
 526             // `std::sys::unix::ext` -> `std::os`
 527             //
 528             // This is correct, as the visible parent of `std::sys::unix::ext` is in fact
 529             // `std::os`.
 530             //
 531             // When printing the path to `CommandExt` and looking at the `cur_def_key` that
 532             // corresponds to `std::sys::unix::ext`, we would normally print `ext` and then go
 533             // to the parent - resulting in a mangled path like
 534             // `std::os::ext::process::CommandExt`.
 535             //
 536             // Instead, we must detect that there was a re-export and instead print `unix`
 537             // (which is the name `std::sys::unix::ext` was re-exported as in `std::os`). To
 538             // do this, we compare the parent of `std::sys::unix::ext` (`std::sys::unix`) with
 539             // the visible parent (`std::os`). If these do not match, then we iterate over
 540             // the children of the visible parent (as was done when computing
 541             // `visible_parent_map`), looking for the specific child we currently have and then
 542             // have access to the re-exported name.
 543             DefPathData::TypeNs(ref mut name) if Some(visible_parent) != actual_parent => {
 544                 // Item might be re-exported several times, but filter for the one
 545                 // that's public and whose identifier isn't `_`.
 546                 let reexport = self
 547                     .tcx()
 548                     .module_children(visible_parent)
 549                     .iter()
 550                     .filter(|child| child.res.opt_def_id() == Some(def_id))
 551                     .find(|child| child.vis.is_public() && child.ident.name != kw::Underscore)
 552                     .map(|child| child.ident.name);
 553
 554                 if let Some(new_name) = reexport {
 555                     *name = new_name;
 556                 } else {
 557                     // There is no name that is public and isn't `_`, so bail.
 558                     return Ok((self, false));
 559                 }
 560             }
 561             // Re-exported `extern crate` (#43189).
 562             DefPathData::CrateRoot => {
 563                 data = DefPathData::TypeNs(self.tcx().crate_name(def_id.krate));
 564             }
 565             _ => {}
 566         }
 567         debug!("try_print_visible_def_path: data={:?}", data);
 568
 569         if callers.contains(&visible_parent) {
 570             return Ok((self, false));
 571         }
 572         callers.push(visible_parent);
 573         // HACK(eddyb) this bypasses `path_append`'s prefix printing to avoid
 574         // knowing ahead of time whether the entire path will succeed or not.
 575         // To support printers that do not implement `PrettyPrinter`, a `Vec` or
 576         // linked list on the stack would need to be built, before any printing.
 577         match self.try_print_visible_def_path_recur(visible_parent, callers)? {
 578             (cx, false) => return Ok((cx, false)),
 579             (cx, true) => self = cx,
 580         }
 581         callers.pop();
 582
 583         Ok((self.path_append(Ok, &DisambiguatedDefPathData { data, disambiguator: 0 })?, true))
 584     }
 585
 586     fn pretty_path_qualified(
 587         self,
 588         self_ty: Ty<'tcx>,
 589         trait_ref: Option<ty::TraitRef<'tcx>>,
 590     ) -> Result<Self::Path, Self::Error> {
 591         if trait_ref.is_none() {
 592             // Inherent impls. Try to print `Foo::bar` for an inherent
 593             // impl on `Foo`, but fallback to `<Foo>::bar` if self-type is
 594             // anything other than a simple path.
 595             match self_ty.kind() {
 596                 ty::Adt(..)
 597                 | ty::Foreign(_)
 598                 | ty::Bool
 599                 | ty::Char
 600                 | ty::Str
 601                 | ty::Int(_)
 602                 | ty::Uint(_)
 603                 | ty::Float(_) => {
 604                     return self_ty.print(self);
 605                 }
 606
 607                 _ => {}
 608             }
 609         }
 610
 611         self.generic_delimiters(|mut cx| {
 612             define_scoped_cx!(cx);
 613
 614             p!(print(self_ty));
 615             if let Some(trait_ref) = trait_ref {
 616                 p!(" as ", print(trait_ref.print_only_trait_path()));
 617             }
 618             Ok(cx)
 619         })
 620     }
 621
 622     fn pretty_path_append_impl(
 623         mut self,
 624         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
 625         self_ty: Ty<'tcx>,
 626         trait_ref: Option<ty::TraitRef<'tcx>>,
 627     ) -> Result<Self::Path, Self::Error> {
 628         self = print_prefix(self)?;
 629
 630         self.generic_delimiters(|mut cx| {
 631             define_scoped_cx!(cx);
 632
 633             p!("impl ");
 634             if let Some(trait_ref) = trait_ref {
 635                 p!(print(trait_ref.print_only_trait_path()), " for ");
 636             }
 637             p!(print(self_ty));
 638
 639             Ok(cx)
 640         })
 641     }
 642
 643     fn pretty_print_type(mut self, ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
 644         define_scoped_cx!(self);
 645
 646         match *ty.kind() {
 647             ty::Bool => p!("bool"),
 648             ty::Char => p!("char"),
 649             ty::Int(t) => p!(write("{}", t.name_str())),
 650             ty::Uint(t) => p!(write("{}", t.name_str())),
 651             ty::Float(t) => p!(write("{}", t.name_str())),
 652             ty::RawPtr(ref tm) => {
 653                 p!(write(
 654                     "*{} ",
 655                     match tm.mutbl {
 656                         hir::Mutability::Mut => "mut",
 657                         hir::Mutability::Not => "const",
 658                     }
 659                 ));
 660                 p!(print(tm.ty))
 661             }
 662             ty::Ref(r, ty, mutbl) => {
 663                 p!("&");
 664                 if self.should_print_region(r) {
 665                     p!(print(r), " ");
 666                 }
 667                 p!(print(ty::TypeAndMut { ty, mutbl }))
 668             }
 669             ty::Never => p!("!"),
 670             ty::Tuple(ref tys) => {
 671                 p!("(", comma_sep(tys.iter()));
 672                 if tys.len() == 1 {
 673                     p!(",");
 674                 }
 675                 p!(")")
 676             }
 677             ty::FnDef(def_id, substs) => {
 678                 let sig = self.tcx().fn_sig(def_id).subst(self.tcx(), substs);
 679                 p!(print(sig), " {{", print_value_path(def_id, substs), "}}");
 680             }
 681             ty::FnPtr(ref bare_fn) => p!(print(bare_fn)),
 682             ty::Infer(infer_ty) => {
 683                 let verbose = self.should_print_verbose();
 684                 if let ty::TyVar(ty_vid) = infer_ty {
 685                     if let Some(name) = self.ty_infer_name(ty_vid) {
 686                         p!(write("{}", name))
 687                     } else {
 688                         if verbose {
 689                             p!(write("{:?}", infer_ty))
 690                         } else {
 691                             p!(write("{}", infer_ty))
 692                         }
 693                     }
 694                 } else {
 695                     if verbose { p!(write("{:?}", infer_ty)) } else { p!(write("{}", infer_ty)) }
 696                 }
 697             }
 698             ty::Error(_) => p!("[type error]"),
 699             ty::Param(ref param_ty) => p!(print(param_ty)),
 700             ty::Bound(debruijn, bound_ty) => match bound_ty.kind {
 701                 ty::BoundTyKind::Anon(bv) => {
 702                     self.pretty_print_bound_var(debruijn, ty::BoundVar::from_u32(bv))?
 703                 }
 704                 ty::BoundTyKind::Param(_, s) => p!(write("{}", s)),
 705             },
 706             ty::Adt(def, substs) => {
 707                 p!(print_def_path(def.did(), substs));
 708             }
 709             ty::Dynamic(data, r, repr) => {
 710                 let print_r = self.should_print_region(r);
 711                 if print_r {
 712                     p!("(");
 713                 }
 714                 match repr {
 715                     ty::Dyn => p!("dyn "),
 716                     ty::DynStar => p!("dyn* "),
 717                 }
 718                 p!(print(data));
 719                 if print_r {
 720                     p!(" + ", print(r), ")");
 721                 }
 722             }
 723             ty::Foreign(def_id) => {
 724                 p!(print_def_path(def_id, &[]));
 725             }
 726             ty::Alias(ty::Projection, ref data) => {
 727                 if !(self.should_print_verbose() || NO_QUERIES.with(|q| q.get()))
 728                     && self.tcx().def_kind(data.def_id) == DefKind::ImplTraitPlaceholder
 729                 {
 730                     return self.pretty_print_opaque_impl_type(data.def_id, data.substs);
 731                 } else {
 732                     p!(print(data))
 733                 }
 734             }
 735             ty::Placeholder(placeholder) => p!(write("Placeholder({:?})", placeholder)),
 736             ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
 737                 // FIXME(eddyb) print this with `print_def_path`.
 738                 // We use verbose printing in 'NO_QUERIES' mode, to
 739                 // avoid needing to call `predicates_of`. This should
 740                 // only affect certain debug messages (e.g. messages printed
 741                 // from `rustc_middle::ty` during the computation of `tcx.predicates_of`),
 742                 // and should have no effect on any compiler output.
 743                 if self.should_print_verbose() || NO_QUERIES.with(|q| q.get()) {
 744                     p!(write("Opaque({:?}, {:?})", def_id, substs));
 745                     return Ok(self);
 746                 }
 747
 748                 let parent = self.tcx().parent(def_id);
 749                 match self.tcx().def_kind(parent) {
 750                     DefKind::TyAlias | DefKind::AssocTy => {
 751                         if let ty::Alias(ty::Opaque, ty::AliasTy { def_id: d, .. }) =
 752                             *self.tcx().type_of(parent).kind()
 753                         {
 754                             if d == def_id {
 755                                 // If the type alias directly starts with the `impl` of the
 756                                 // opaque type we're printing, then skip the `::{opaque#1}`.
 757                                 p!(print_def_path(parent, substs));
 758                                 return Ok(self);
 759                             }
 760                         }
 761                         // Complex opaque type, e.g. `type Foo = (i32, impl Debug);`
 762                         p!(print_def_path(def_id, substs));
 763                         return Ok(self);
 764                     }
 765                     _ => return self.pretty_print_opaque_impl_type(def_id, substs),
 766                 }
 767             }
 768             ty::Str => p!("str"),
 769             ty::Generator(did, substs, movability) => {
 770                 p!(write("["));
 771                 let generator_kind = self.tcx().generator_kind(did).unwrap();
 772                 let should_print_movability =
 773                     self.should_print_verbose() || generator_kind == hir::GeneratorKind::Gen;
 774
 775                 if should_print_movability {
 776                     match movability {
 777                         hir::Movability::Movable => {}
 778                         hir::Movability::Static => p!("static "),
 779                     }
 780                 }
 781
 782                 if !self.should_print_verbose() {
 783                     p!(write("{}", generator_kind));
 784                     // FIXME(eddyb) should use `def_span`.
 785                     if let Some(did) = did.as_local() {
 786                         let span = self.tcx().def_span(did);
 787                         p!(write(
 788                             "@{}",
 789                             // This may end up in stderr diagnostics but it may also be emitted
 790                             // into MIR. Hence we use the remapped path if available
 791                             self.tcx().sess.source_map().span_to_embeddable_string(span)
 792                         ));
 793                     } else {
 794                         p!(write("@"), print_def_path(did, substs));
 795                     }
 796                 } else {
 797                     p!(print_def_path(did, substs));
 798                     p!(" upvar_tys=(");
 799                     if !substs.as_generator().is_valid() {
 800                         p!("unavailable");
 801                     } else {
 802                         self = self.comma_sep(substs.as_generator().upvar_tys())?;
 803                     }
 804                     p!(")");
 805
 806                     if substs.as_generator().is_valid() {
 807                         p!(" ", print(substs.as_generator().witness()));
 808                     }
 809                 }
 810
 811                 p!("]")
 812             }
 813             ty::GeneratorWitness(types) => {
 814                 p!(in_binder(&types));
 815             }
 816             ty::GeneratorWitnessMIR(did, substs) => {
 817                 p!(write("["));
 818                 if !self.tcx().sess.verbose() {
 819                     p!("generator witness");
 820                     // FIXME(eddyb) should use `def_span`.
 821                     if let Some(did) = did.as_local() {
 822                         let span = self.tcx().def_span(did);
 823                         p!(write(
 824                             "@{}",
 825                             // This may end up in stderr diagnostics but it may also be emitted
 826                             // into MIR. Hence we use the remapped path if available
 827                             self.tcx().sess.source_map().span_to_embeddable_string(span)
 828                         ));
 829                     } else {
 830                         p!(write("@"), print_def_path(did, substs));
 831                     }
 832                 } else {
 833                     p!(print_def_path(did, substs));
 834                 }
 835
 836                 p!("]")
 837             }
 838             ty::Closure(did, substs) => {
 839                 p!(write("["));
 840                 if !self.should_print_verbose() {
 841                     p!(write("closure"));
 842                     // FIXME(eddyb) should use `def_span`.
 843                     if let Some(did) = did.as_local() {
 844                         if self.tcx().sess.opts.unstable_opts.span_free_formats {
 845                             p!("@", print_def_path(did.to_def_id(), substs));
 846                         } else {
 847                             let span = self.tcx().def_span(did);
 848                             let preference = if FORCE_TRIMMED_PATH.with(|flag| flag.get()) {
 849                                 FileNameDisplayPreference::Short
 850                             } else {
 851                                 FileNameDisplayPreference::Remapped
 852                             };
 853                             p!(write(
 854                                 "@{}",
 855                                 // This may end up in stderr diagnostics but it may also be emitted
 856                                 // into MIR. Hence we use the remapped path if available
 857                                 self.tcx().sess.source_map().span_to_string(span, preference)
 858                             ));
 859                         }
 860                     } else {
 861                         p!(write("@"), print_def_path(did, substs));
 862                     }
 863                 } else {
 864                     p!(print_def_path(did, substs));
 865                     if !substs.as_closure().is_valid() {
 866                         p!(" closure_substs=(unavailable)");
 867                         p!(write(" substs={:?}", substs));
 868                     } else {
 869                         p!(" closure_kind_ty=", print(substs.as_closure().kind_ty()));
 870                         p!(
 871                             " closure_sig_as_fn_ptr_ty=",
 872                             print(substs.as_closure().sig_as_fn_ptr_ty())
 873                         );
 874                         p!(" upvar_tys=(");
 875                         self = self.comma_sep(substs.as_closure().upvar_tys())?;
 876                         p!(")");
 877                     }
 878                 }
 879                 p!("]");
 880             }
 881             ty::Array(ty, sz) => p!("[", print(ty), "; ", print(sz), "]"),
 882             ty::Slice(ty) => p!("[", print(ty), "]"),
 883         }
 884
 885         Ok(self)
 886     }
 887
 888     fn pretty_print_opaque_impl_type(
 889         mut self,
 890         def_id: DefId,
 891         substs: &'tcx ty::List<ty::GenericArg<'tcx>>,
 892     ) -> Result<Self::Type, Self::Error> {
 893         let tcx = self.tcx();
 894
 895         // Grab the "TraitA + TraitB" from `impl TraitA + TraitB`,
 896         // by looking up the projections associated with the def_id.
 897         let bounds = tcx.bound_explicit_item_bounds(def_id);
 898
 899         let mut traits = FxIndexMap::default();
 900         let mut fn_traits = FxIndexMap::default();
 901         let mut is_sized = false;
 902         let mut lifetimes = SmallVec::<[ty::Region<'tcx>; 1]>::new();
 903
 904         for (predicate, _) in bounds.subst_iter_copied(tcx, substs) {
 905             let bound_predicate = predicate.kind();
 906
 907             match bound_predicate.skip_binder() {
 908                 ty::PredicateKind::Clause(ty::Clause::Trait(pred)) => {
 909                     let trait_ref = bound_predicate.rebind(pred.trait_ref);
 910
 911                     // Don't print + Sized, but rather + ?Sized if absent.
 912                     if Some(trait_ref.def_id()) == tcx.lang_items().sized_trait() {
 913                         is_sized = true;
 914                         continue;
 915                     }
 916
 917                     self.insert_trait_and_projection(trait_ref, None, &mut traits, &mut fn_traits);
 918                 }
 919                 ty::PredicateKind::Clause(ty::Clause::Projection(pred)) => {
 920                     let proj_ref = bound_predicate.rebind(pred);
 921                     let trait_ref = proj_ref.required_poly_trait_ref(tcx);
 922
 923                     // Projection type entry -- the def-id for naming, and the ty.
 924                     let proj_ty = (proj_ref.projection_def_id(), proj_ref.term());
 925
 926                     self.insert_trait_and_projection(
 927                         trait_ref,
 928                         Some(proj_ty),
 929                         &mut traits,
 930                         &mut fn_traits,
 931                     );
 932                 }
 933                 ty::PredicateKind::Clause(ty::Clause::TypeOutlives(outlives)) => {
 934                     lifetimes.push(outlives.1);
 935                 }
 936                 _ => {}
 937             }
 938         }
 939
 940         write!(self, "impl ")?;
 941
 942         let mut first = true;
 943         // Insert parenthesis around (Fn(A, B) -> C) if the opaque ty has more than one other trait
 944         let paren_needed = fn_traits.len() > 1 || traits.len() > 0 || !is_sized;
 945
 946         for (fn_once_trait_ref, entry) in fn_traits {
 947             write!(self, "{}", if first { "" } else { " + " })?;
 948             write!(self, "{}", if paren_needed { "(" } else { "" })?;
 949
 950             self = self.wrap_binder(&fn_once_trait_ref, |trait_ref, mut cx| {
 951                 define_scoped_cx!(cx);
 952                 // Get the (single) generic ty (the args) of this FnOnce trait ref.
 953                 let generics = tcx.generics_of(trait_ref.def_id);
 954                 let args = generics.own_substs_no_defaults(tcx, trait_ref.substs);
 955
 956                 match (entry.return_ty, args[0].expect_ty()) {
 957                     // We can only print `impl Fn() -> ()` if we have a tuple of args and we recorded
 958                     // a return type.
 959                     (Some(return_ty), arg_tys) if matches!(arg_tys.kind(), ty::Tuple(_)) => {
 960                         let name = if entry.fn_trait_ref.is_some() {
 961                             "Fn"
 962                         } else if entry.fn_mut_trait_ref.is_some() {
 963                             "FnMut"
 964                         } else {
 965                             "FnOnce"
 966                         };
 967
 968                         p!(write("{}(", name));
 969
 970                         for (idx, ty) in arg_tys.tuple_fields().iter().enumerate() {
 971                             if idx > 0 {
 972                                 p!(", ");
 973                             }
 974                             p!(print(ty));
 975                         }
 976
 977                         p!(")");
 978                         if let Some(ty) = return_ty.skip_binder().ty() {
 979                             if !ty.is_unit() {
 980                                 p!(" -> ", print(return_ty));
 981                             }
 982                         }
 983                         p!(write("{}", if paren_needed { ")" } else { "" }));
 984
 985                         first = false;
 986                     }
 987                     // If we got here, we can't print as a `impl Fn(A, B) -> C`. Just record the
 988                     // trait_refs we collected in the OpaqueFnEntry as normal trait refs.
 989                     _ => {
 990                         if entry.has_fn_once {
 991                             traits.entry(fn_once_trait_ref).or_default().extend(
 992                                 // Group the return ty with its def id, if we had one.
 993                                 entry
 994                                     .return_ty
 995                                     .map(|ty| (tcx.require_lang_item(LangItem::FnOnce, None), ty)),
 996                             );
 997                         }
 998                         if let Some(trait_ref) = entry.fn_mut_trait_ref {
 999                             traits.entry(trait_ref).or_default();
1000                         }
1001                         if let Some(trait_ref) = entry.fn_trait_ref {
1002                             traits.entry(trait_ref).or_default();
1003                         }
1004                     }
1005                 }
1006
1007                 Ok(cx)
1008             })?;
1009         }
1010
1011         // Print the rest of the trait types (that aren't Fn* family of traits)
1012         for (trait_ref, assoc_items) in traits {
1013             write!(self, "{}", if first { "" } else { " + " })?;
1014
1015             self = self.wrap_binder(&trait_ref, |trait_ref, mut cx| {
1016                 define_scoped_cx!(cx);
1017                 p!(print(trait_ref.print_only_trait_name()));
1018
1019                 let generics = tcx.generics_of(trait_ref.def_id);
1020                 let args = generics.own_substs_no_defaults(tcx, trait_ref.substs);
1021
1022                 if !args.is_empty() || !assoc_items.is_empty() {
1023                     let mut first = true;
1024
1025                     for ty in args {
1026                         if first {
1027                             p!("<");
1028                             first = false;
1029                         } else {
1030                             p!(", ");
1031                         }
1032                         p!(print(ty));
1033                     }
1034
1035                     for (assoc_item_def_id, term) in assoc_items {
1036                         // Skip printing `<[generator@] as Generator<_>>::Return` from async blocks,
1037                         // unless we can find out what generator return type it comes from.
1038                         let term = if let Some(ty) = term.skip_binder().ty()
1039                             && let ty::Alias(ty::Projection, proj) = ty.kind()
1040                             && let Some(assoc) = tcx.opt_associated_item(proj.def_id)
1041                             && assoc.trait_container(tcx) == tcx.lang_items().gen_trait()
1042                             && assoc.name == rustc_span::sym::Return
1043                         {
1044                             if let ty::Generator(_, substs, _) = substs.type_at(0).kind() {
1045                                 let return_ty = substs.as_generator().return_ty();
1046                                 if !return_ty.is_ty_var() {
1047                                     return_ty.into()
1048                                 } else {
1049                                     continue;
1050                                 }
1051                             } else {
1052                                 continue;
1053                             }
1054                         } else {
1055                             term.skip_binder()
1056                         };
1057
1058                         if first {
1059                             p!("<");
1060                             first = false;
1061                         } else {
1062                             p!(", ");
1063                         }
1064
1065                         p!(write("{} = ", tcx.associated_item(assoc_item_def_id).name));
1066
1067                         match term.unpack() {
1068                             TermKind::Ty(ty) => p!(print(ty)),
1069                             TermKind::Const(c) => p!(print(c)),
1070                         };
1071                     }
1072
1073                     if !first {
1074                         p!(">");
1075                     }
1076                 }
1077
1078                 first = false;
1079                 Ok(cx)
1080             })?;
1081         }
1082
1083         if !is_sized {
1084             write!(self, "{}?Sized", if first { "" } else { " + " })?;
1085         } else if first {
1086             write!(self, "Sized")?;
1087         }
1088
1089         if !FORCE_TRIMMED_PATH.with(|flag| flag.get()) {
1090             for re in lifetimes {
1091                 write!(self, " + ")?;
1092                 self = self.print_region(re)?;
1093             }
1094         }
1095
1096         Ok(self)
1097     }
1098
1099     /// Insert the trait ref and optionally a projection type associated with it into either the
1100     /// traits map or fn_traits map, depending on if the trait is in the Fn* family of traits.
1101     fn insert_trait_and_projection(
1102         &mut self,
1103         trait_ref: ty::PolyTraitRef<'tcx>,
1104         proj_ty: Option<(DefId, ty::Binder<'tcx, Term<'tcx>>)>,
1105         traits: &mut FxIndexMap<
1106             ty::PolyTraitRef<'tcx>,
1107             FxIndexMap<DefId, ty::Binder<'tcx, Term<'tcx>>>,
1108         >,
1109         fn_traits: &mut FxIndexMap<ty::PolyTraitRef<'tcx>, OpaqueFnEntry<'tcx>>,
1110     ) {
1111         let trait_def_id = trait_ref.def_id();
1112
1113         // If our trait_ref is FnOnce or any of its children, project it onto the parent FnOnce
1114         // super-trait ref and record it there.
1115         if let Some(fn_once_trait) = self.tcx().lang_items().fn_once_trait() {
1116             // If we have a FnOnce, then insert it into
1117             if trait_def_id == fn_once_trait {
1118                 let entry = fn_traits.entry(trait_ref).or_default();
1119                 // Optionally insert the return_ty as well.
1120                 if let Some((_, ty)) = proj_ty {
1121                     entry.return_ty = Some(ty);
1122                 }
1123                 entry.has_fn_once = true;
1124                 return;
1125             } else if Some(trait_def_id) == self.tcx().lang_items().fn_mut_trait() {
1126                 let super_trait_ref = crate::traits::util::supertraits(self.tcx(), trait_ref)
1127                     .find(|super_trait_ref| super_trait_ref.def_id() == fn_once_trait)
1128                     .unwrap();
1129
1130                 fn_traits.entry(super_trait_ref).or_default().fn_mut_trait_ref = Some(trait_ref);
1131                 return;
1132             } else if Some(trait_def_id) == self.tcx().lang_items().fn_trait() {
1133                 let super_trait_ref = crate::traits::util::supertraits(self.tcx(), trait_ref)
1134                     .find(|super_trait_ref| super_trait_ref.def_id() == fn_once_trait)
1135                     .unwrap();
1136
1137                 fn_traits.entry(super_trait_ref).or_default().fn_trait_ref = Some(trait_ref);
1138                 return;
1139             }
1140         }
1141
1142         // Otherwise, just group our traits and projection types.
1143         traits.entry(trait_ref).or_default().extend(proj_ty);
1144     }
1145
1146     fn pretty_print_bound_var(
1147         &mut self,
1148         debruijn: ty::DebruijnIndex,
1149         var: ty::BoundVar,
1150     ) -> Result<(), Self::Error> {
1151         if debruijn == ty::INNERMOST {
1152             write!(self, "^{}", var.index())
1153         } else {
1154             write!(self, "^{}_{}", debruijn.index(), var.index())
1155         }
1156     }
1157
1158     fn ty_infer_name(&self, _: ty::TyVid) -> Option<Symbol> {
1159         None
1160     }
1161
1162     fn const_infer_name(&self, _: ty::ConstVid<'tcx>) -> Option<Symbol> {
1163         None
1164     }
1165
1166     fn pretty_print_dyn_existential(
1167         mut self,
1168         predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
1169     ) -> Result<Self::DynExistential, Self::Error> {
1170         // Generate the main trait ref, including associated types.
1171         let mut first = true;
1172
1173         if let Some(principal) = predicates.principal() {
1174             self = self.wrap_binder(&principal, |principal, mut cx| {
1175                 define_scoped_cx!(cx);
1176                 p!(print_def_path(principal.def_id, &[]));
1177
1178                 let mut resugared = false;
1179
1180                 // Special-case `Fn(...) -> ...` and re-sugar it.
1181                 let fn_trait_kind = cx.tcx().fn_trait_kind_from_def_id(principal.def_id);
1182                 if !cx.should_print_verbose() && fn_trait_kind.is_some() {
1183                     if let ty::Tuple(tys) = principal.substs.type_at(0).kind() {
1184                         let mut projections = predicates.projection_bounds();
1185                         if let (Some(proj), None) = (projections.next(), projections.next()) {
1186                             p!(pretty_fn_sig(
1187                                 tys,
1188                                 false,
1189                                 proj.skip_binder().term.ty().expect("Return type was a const")
1190                             ));
1191                             resugared = true;
1192                         }
1193                     }
1194                 }
1195
1196                 // HACK(eddyb) this duplicates `FmtPrinter`'s `path_generic_args`,
1197                 // in order to place the projections inside the `<...>`.
1198                 if !resugared {
1199                     // Use a type that can't appear in defaults of type parameters.
1200                     let dummy_cx = cx.tcx().mk_ty_infer(ty::FreshTy(0));
1201                     let principal = principal.with_self_ty(cx.tcx(), dummy_cx);
1202
1203                     let args = cx
1204                         .tcx()
1205                         .generics_of(principal.def_id)
1206                         .own_substs_no_defaults(cx.tcx(), principal.substs);
1207
1208                     let mut projections = predicates.projection_bounds();
1209
1210                     let mut args = args.iter().cloned();
1211                     let arg0 = args.next();
1212                     let projection0 = projections.next();
1213                     if arg0.is_some() || projection0.is_some() {
1214                         let args = arg0.into_iter().chain(args);
1215                         let projections = projection0.into_iter().chain(projections);
1216
1217                         p!(generic_delimiters(|mut cx| {
1218                             cx = cx.comma_sep(args)?;
1219                             if arg0.is_some() && projection0.is_some() {
1220                                 write!(cx, ", ")?;
1221                             }
1222                             cx.comma_sep(projections)
1223                         }));
1224                     }
1225                 }
1226                 Ok(cx)
1227             })?;
1228
1229             first = false;
1230         }
1231
1232         define_scoped_cx!(self);
1233
1234         // Builtin bounds.
1235         // FIXME(eddyb) avoid printing twice (needed to ensure
1236         // that the auto traits are sorted *and* printed via cx).
1237         let mut auto_traits: Vec<_> = predicates.auto_traits().collect();
1238
1239         // The auto traits come ordered by `DefPathHash`. While
1240         // `DefPathHash` is *stable* in the sense that it depends on
1241         // neither the host nor the phase of the moon, it depends
1242         // "pseudorandomly" on the compiler version and the target.
1243         //
1244         // To avoid causing instabilities in compiletest
1245         // output, sort the auto-traits alphabetically.
1246         auto_traits.sort_by_cached_key(|did| with_no_trimmed_paths!(self.tcx().def_path_str(*did)));
1247
1248         for def_id in auto_traits {
1249             if !first {
1250                 p!(" + ");
1251             }
1252             first = false;
1253
1254             p!(print_def_path(def_id, &[]));
1255         }
1256
1257         Ok(self)
1258     }
1259
1260     fn pretty_fn_sig(
1261         mut self,
1262         inputs: &[Ty<'tcx>],
1263         c_variadic: bool,
1264         output: Ty<'tcx>,
1265     ) -> Result<Self, Self::Error> {
1266         define_scoped_cx!(self);
1267
1268         p!("(", comma_sep(inputs.iter().copied()));
1269         if c_variadic {
1270             if !inputs.is_empty() {
1271                 p!(", ");
1272             }
1273             p!("...");
1274         }
1275         p!(")");
1276         if !output.is_unit() {
1277             p!(" -> ", print(output));
1278         }
1279
1280         Ok(self)
1281     }
1282
1283     fn pretty_print_const(
1284         mut self,
1285         ct: ty::Const<'tcx>,
1286         print_ty: bool,
1287     ) -> Result<Self::Const, Self::Error> {
1288         define_scoped_cx!(self);
1289
1290         if self.should_print_verbose() {
1291             p!(write("Const({:?}: {:?})", ct.kind(), ct.ty()));
1292             return Ok(self);
1293         }
1294
1295         macro_rules! print_underscore {
1296             () => {{
1297                 if print_ty {
1298                     self = self.typed_value(
1299                         |mut this| {
1300                             write!(this, "_")?;
1301                             Ok(this)
1302                         },
1303                         |this| this.print_type(ct.ty()),
1304                         ": ",
1305                     )?;
1306                 } else {
1307                     write!(self, "_")?;
1308                 }
1309             }};
1310         }
1311
1312         match ct.kind() {
1313             ty::ConstKind::Unevaluated(ty::UnevaluatedConst { def, substs }) => {
1314                 match self.tcx().def_kind(def.did) {
1315                     DefKind::Const | DefKind::AssocConst => {
1316                         p!(print_value_path(def.did, substs))
1317                     }
1318                     DefKind::AnonConst => {
1319                         if def.is_local()
1320                             && let span = self.tcx().def_span(def.did)
1321                             && let Ok(snip) = self.tcx().sess.source_map().span_to_snippet(span)
1322                         {
1323                             p!(write("{}", snip))
1324                         } else {
1325                             // Do not call `print_value_path` as if a parent of this anon const is an impl it will
1326                             // attempt to print out the impl trait ref i.e. `<T as Trait>::{constant#0}`. This would
1327                             // cause printing to enter an infinite recursion if the anon const is in the self type i.e.
1328                             // `impl<T: Default> Default for [T; 32 - 1 - 1 - 1] {`
1329                             // where we would try to print `<[T; /* print `constant#0` again */] as Default>::{constant#0}`
1330                             p!(write("{}::{}", self.tcx().crate_name(def.did.krate), self.tcx().def_path(def.did).to_string_no_crate_verbose()))
1331                         }
1332                     }
1333                     defkind => bug!("`{:?}` has unexpcted defkind {:?}", ct, defkind),
1334                 }
1335             }
1336             ty::ConstKind::Infer(infer_ct) => {
1337                 match infer_ct {
1338                     ty::InferConst::Var(ct_vid)
1339                         if let Some(name) = self.const_infer_name(ct_vid) =>
1340                             p!(write("{}", name)),
1341                     _ => print_underscore!(),
1342                 }
1343             }
1344             ty::ConstKind::Param(ParamConst { name, .. }) => p!(write("{}", name)),
1345             ty::ConstKind::Value(value) => {
1346                 return self.pretty_print_const_valtree(value, ct.ty(), print_ty);
1347             }
1348
1349             ty::ConstKind::Bound(debruijn, bound_var) => {
1350                 self.pretty_print_bound_var(debruijn, bound_var)?
1351             }
1352             ty::ConstKind::Placeholder(placeholder) => p!(write("Placeholder({:?})", placeholder)),
1353             // FIXME(generic_const_exprs):
1354             // write out some legible representation of an abstract const?
1355             ty::ConstKind::Expr(_) => p!("[const expr]"),
1356             ty::ConstKind::Error(_) => p!("[const error]"),
1357         };
1358         Ok(self)
1359     }
1360
1361     fn pretty_print_const_scalar(
1362         self,
1363         scalar: Scalar,
1364         ty: Ty<'tcx>,
1365         print_ty: bool,
1366     ) -> Result<Self::Const, Self::Error> {
1367         match scalar {
1368             Scalar::Ptr(ptr, _size) => self.pretty_print_const_scalar_ptr(ptr, ty, print_ty),
1369             Scalar::Int(int) => self.pretty_print_const_scalar_int(int, ty, print_ty),
1370         }
1371     }
1372
1373     fn pretty_print_const_scalar_ptr(
1374         mut self,
1375         ptr: Pointer,
1376         ty: Ty<'tcx>,
1377         print_ty: bool,
1378     ) -> Result<Self::Const, Self::Error> {
1379         define_scoped_cx!(self);
1380
1381         let (alloc_id, offset) = ptr.into_parts();
1382         match ty.kind() {
1383             // Byte strings (&[u8; N])
1384             ty::Ref(_, inner, _) => {
1385                 if let ty::Array(elem, len) = inner.kind() {
1386                     if let ty::Uint(ty::UintTy::U8) = elem.kind() {
1387                         if let ty::ConstKind::Value(ty::ValTree::Leaf(int)) = len.kind() {
1388                             match self.tcx().try_get_global_alloc(alloc_id) {
1389                                 Some(GlobalAlloc::Memory(alloc)) => {
1390                                     let len = int.assert_bits(self.tcx().data_layout.pointer_size);
1391                                     let range =
1392                                         AllocRange { start: offset, size: Size::from_bytes(len) };
1393                                     if let Ok(byte_str) =
1394                                         alloc.inner().get_bytes_strip_provenance(&self.tcx(), range)
1395                                     {
1396                                         p!(pretty_print_byte_str(byte_str))
1397                                     } else {
1398                                         p!("<too short allocation>")
1399                                     }
1400                                 }
1401                                 // FIXME: for statics, vtables, and functions, we could in principle print more detail.
1402                                 Some(GlobalAlloc::Static(def_id)) => {
1403                                     p!(write("<static({:?})>", def_id))
1404                                 }
1405                                 Some(GlobalAlloc::Function(_)) => p!("<function>"),
1406                                 Some(GlobalAlloc::VTable(..)) => p!("<vtable>"),
1407                                 None => p!("<dangling pointer>"),
1408                             }
1409                             return Ok(self);
1410                         }
1411                     }
1412                 }
1413             }
1414             ty::FnPtr(_) => {
1415                 // FIXME: We should probably have a helper method to share code with the "Byte strings"
1416                 // printing above (which also has to handle pointers to all sorts of things).
1417                 if let Some(GlobalAlloc::Function(instance)) =
1418                     self.tcx().try_get_global_alloc(alloc_id)
1419                 {
1420                     self = self.typed_value(
1421                         |this| this.print_value_path(instance.def_id(), instance.substs),
1422                         |this| this.print_type(ty),
1423                         " as ",
1424                     )?;
1425                     return Ok(self);
1426                 }
1427             }
1428             _ => {}
1429         }
1430         // Any pointer values not covered by a branch above
1431         self = self.pretty_print_const_pointer(ptr, ty, print_ty)?;
1432         Ok(self)
1433     }
1434
1435     fn pretty_print_const_scalar_int(
1436         mut self,
1437         int: ScalarInt,
1438         ty: Ty<'tcx>,
1439         print_ty: bool,
1440     ) -> Result<Self::Const, Self::Error> {
1441         define_scoped_cx!(self);
1442
1443         match ty.kind() {
1444             // Bool
1445             ty::Bool if int == ScalarInt::FALSE => p!("false"),
1446             ty::Bool if int == ScalarInt::TRUE => p!("true"),
1447             // Float
1448             ty::Float(ty::FloatTy::F32) => {
1449                 p!(write("{}f32", Single::try_from(int).unwrap()))
1450             }
1451             ty::Float(ty::FloatTy::F64) => {
1452                 p!(write("{}f64", Double::try_from(int).unwrap()))
1453             }
1454             // Int
1455             ty::Uint(_) | ty::Int(_) => {
1456                 let int =
1457                     ConstInt::new(int, matches!(ty.kind(), ty::Int(_)), ty.is_ptr_sized_integral());
1458                 if print_ty { p!(write("{:#?}", int)) } else { p!(write("{:?}", int)) }
1459             }
1460             // Char
1461             ty::Char if char::try_from(int).is_ok() => {
1462                 p!(write("{:?}", char::try_from(int).unwrap()))
1463             }
1464             // Pointer types
1465             ty::Ref(..) | ty::RawPtr(_) | ty::FnPtr(_) => {
1466                 let data = int.assert_bits(self.tcx().data_layout.pointer_size);
1467                 self = self.typed_value(
1468                     |mut this| {
1469                         write!(this, "0x{:x}", data)?;
1470                         Ok(this)
1471                     },
1472                     |this| this.print_type(ty),
1473                     " as ",
1474                 )?;
1475             }
1476             // Nontrivial types with scalar bit representation
1477             _ => {
1478                 let print = |mut this: Self| {
1479                     if int.size() == Size::ZERO {
1480                         write!(this, "transmute(())")?;
1481                     } else {
1482                         write!(this, "transmute(0x{:x})", int)?;
1483                     }
1484                     Ok(this)
1485                 };
1486                 self = if print_ty {
1487                     self.typed_value(print, |this| this.print_type(ty), ": ")?
1488                 } else {
1489                     print(self)?
1490                 };
1491             }
1492         }
1493         Ok(self)
1494     }
1495
1496     /// This is overridden for MIR printing because we only want to hide alloc ids from users, not
1497     /// from MIR where it is actually useful.
1498     fn pretty_print_const_pointer<Prov: Provenance>(
1499         mut self,
1500         _: Pointer<Prov>,
1501         ty: Ty<'tcx>,
1502         print_ty: bool,
1503     ) -> Result<Self::Const, Self::Error> {
1504         if print_ty {
1505             self.typed_value(
1506                 |mut this| {
1507                     this.write_str("&_")?;
1508                     Ok(this)
1509                 },
1510                 |this| this.print_type(ty),
1511                 ": ",
1512             )
1513         } else {
1514             self.write_str("&_")?;
1515             Ok(self)
1516         }
1517     }
1518
1519     fn pretty_print_byte_str(mut self, byte_str: &'tcx [u8]) -> Result<Self::Const, Self::Error> {
1520         write!(self, "b\"{}\"", byte_str.escape_ascii())?;
1521         Ok(self)
1522     }
1523
1524     fn pretty_print_const_valtree(
1525         mut self,
1526         valtree: ty::ValTree<'tcx>,
1527         ty: Ty<'tcx>,
1528         print_ty: bool,
1529     ) -> Result<Self::Const, Self::Error> {
1530         define_scoped_cx!(self);
1531
1532         if self.should_print_verbose() {
1533             p!(write("ValTree({:?}: ", valtree), print(ty), ")");
1534             return Ok(self);
1535         }
1536
1537         let u8_type = self.tcx().types.u8;
1538         match (valtree, ty.kind()) {
1539             (ty::ValTree::Branch(_), ty::Ref(_, inner_ty, _)) => match inner_ty.kind() {
1540                 ty::Slice(t) if *t == u8_type => {
1541                     let bytes = valtree.try_to_raw_bytes(self.tcx(), ty).unwrap_or_else(|| {
1542                         bug!(
1543                             "expected to convert valtree {:?} to raw bytes for type {:?}",
1544                             valtree,
1545                             t
1546                         )
1547                     });
1548                     return self.pretty_print_byte_str(bytes);
1549                 }
1550                 ty::Str => {
1551                     let bytes = valtree.try_to_raw_bytes(self.tcx(), ty).unwrap_or_else(|| {
1552                         bug!("expected to convert valtree to raw bytes for type {:?}", ty)
1553                     });
1554                     p!(write("{:?}", String::from_utf8_lossy(bytes)));
1555                     return Ok(self);
1556                 }
1557                 _ => {
1558                     p!("&");
1559                     p!(pretty_print_const_valtree(valtree, *inner_ty, print_ty));
1560                     return Ok(self);
1561                 }
1562             },
1563             (ty::ValTree::Branch(_), ty::Array(t, _)) if *t == u8_type => {
1564                 let bytes = valtree.try_to_raw_bytes(self.tcx(), ty).unwrap_or_else(|| {
1565                     bug!("expected to convert valtree to raw bytes for type {:?}", t)
1566                 });
1567                 p!("*");
1568                 p!(pretty_print_byte_str(bytes));
1569                 return Ok(self);
1570             }
1571             // Aggregates, printed as array/tuple/struct/variant construction syntax.
1572             (ty::ValTree::Branch(_), ty::Array(..) | ty::Tuple(..) | ty::Adt(..)) => {
1573                 let contents = self.tcx().destructure_const(self.tcx().mk_const(valtree, ty));
1574                 let fields = contents.fields.iter().copied();
1575                 match *ty.kind() {
1576                     ty::Array(..) => {
1577                         p!("[", comma_sep(fields), "]");
1578                     }
1579                     ty::Tuple(..) => {
1580                         p!("(", comma_sep(fields));
1581                         if contents.fields.len() == 1 {
1582                             p!(",");
1583                         }
1584                         p!(")");
1585                     }
1586                     ty::Adt(def, _) if def.variants().is_empty() => {
1587                         self = self.typed_value(
1588                             |mut this| {
1589                                 write!(this, "unreachable()")?;
1590                                 Ok(this)
1591                             },
1592                             |this| this.print_type(ty),
1593                             ": ",
1594                         )?;
1595                     }
1596                     ty::Adt(def, substs) => {
1597                         let variant_idx =
1598                             contents.variant.expect("destructed const of adt without variant idx");
1599                         let variant_def = &def.variant(variant_idx);
1600                         p!(print_value_path(variant_def.def_id, substs));
1601                         match variant_def.ctor_kind() {
1602                             Some(CtorKind::Const) => {}
1603                             Some(CtorKind::Fn) => {
1604                                 p!("(", comma_sep(fields), ")");
1605                             }
1606                             None => {
1607                                 p!(" {{ ");
1608                                 let mut first = true;
1609                                 for (field_def, field) in iter::zip(&variant_def.fields, fields) {
1610                                     if !first {
1611                                         p!(", ");
1612                                     }
1613                                     p!(write("{}: ", field_def.name), print(field));
1614                                     first = false;
1615                                 }
1616                                 p!(" }}");
1617                             }
1618                         }
1619                     }
1620                     _ => unreachable!(),
1621                 }
1622                 return Ok(self);
1623             }
1624             (ty::ValTree::Leaf(leaf), ty::Ref(_, inner_ty, _)) => {
1625                 p!(write("&"));
1626                 return self.pretty_print_const_scalar_int(leaf, *inner_ty, print_ty);
1627             }
1628             (ty::ValTree::Leaf(leaf), _) => {
1629                 return self.pretty_print_const_scalar_int(leaf, ty, print_ty);
1630             }
1631             // FIXME(oli-obk): also pretty print arrays and other aggregate constants by reading
1632             // their fields instead of just dumping the memory.
1633             _ => {}
1634         }
1635
1636         // fallback
1637         if valtree == ty::ValTree::zst() {
1638             p!(write("<ZST>"));
1639         } else {
1640             p!(write("{:?}", valtree));
1641         }
1642         if print_ty {
1643             p!(": ", print(ty));
1644         }
1645         Ok(self)
1646     }
1647
1648     fn pretty_closure_as_impl(
1649         mut self,
1650         closure: ty::ClosureSubsts<'tcx>,
1651     ) -> Result<Self::Const, Self::Error> {
1652         let sig = closure.sig();
1653         let kind = closure.kind_ty().to_opt_closure_kind().unwrap_or(ty::ClosureKind::Fn);
1654
1655         write!(self, "impl ")?;
1656         self.wrap_binder(&sig, |sig, mut cx| {
1657             define_scoped_cx!(cx);
1658
1659             p!(print(kind), "(");
1660             for (i, arg) in sig.inputs()[0].tuple_fields().iter().enumerate() {
1661                 if i > 0 {
1662                     p!(", ");
1663                 }
1664                 p!(print(arg));
1665             }
1666             p!(")");
1667
1668             if !sig.output().is_unit() {
1669                 p!(" -> ", print(sig.output()));
1670             }
1671
1672             Ok(cx)
1673         })
1674     }
1675
1676     fn should_print_verbose(&self) -> bool {
1677         self.tcx().sess.verbose()
1678     }
1679 }
1680
1681 // HACK(eddyb) boxed to avoid moving around a large struct by-value.
1682 pub struct FmtPrinter<'a, 'tcx>(Box<FmtPrinterData<'a, 'tcx>>);
1683
1684 pub struct FmtPrinterData<'a, 'tcx> {
1685     tcx: TyCtxt<'tcx>,
1686     fmt: String,
1687
1688     empty_path: bool,
1689     in_value: bool,
1690     pub print_alloc_ids: bool,
1691
1692     // set of all named (non-anonymous) region names
1693     used_region_names: FxHashSet<Symbol>,
1694
1695     region_index: usize,
1696     binder_depth: usize,
1697     printed_type_count: usize,
1698     type_length_limit: Limit,
1699     truncated: bool,
1700
1701     pub region_highlight_mode: RegionHighlightMode<'tcx>,
1702
1703     pub ty_infer_name_resolver: Option<Box<dyn Fn(ty::TyVid) -> Option<Symbol> + 'a>>,
1704     pub const_infer_name_resolver: Option<Box<dyn Fn(ty::ConstVid<'tcx>) -> Option<Symbol> + 'a>>,
1705 }
1706
1707 impl<'a, 'tcx> Deref for FmtPrinter<'a, 'tcx> {
1708     type Target = FmtPrinterData<'a, 'tcx>;
1709     fn deref(&self) -> &Self::Target {
1710         &self.0
1711     }
1712 }
1713
1714 impl DerefMut for FmtPrinter<'_, '_> {
1715     fn deref_mut(&mut self) -> &mut Self::Target {
1716         &mut self.0
1717     }
1718 }
1719
1720 impl<'a, 'tcx> FmtPrinter<'a, 'tcx> {
1721     pub fn new(tcx: TyCtxt<'tcx>, ns: Namespace) -> Self {
1722         Self::new_with_limit(tcx, ns, tcx.type_length_limit())
1723     }
1724
1725     pub fn new_with_limit(tcx: TyCtxt<'tcx>, ns: Namespace, type_length_limit: Limit) -> Self {
1726         FmtPrinter(Box::new(FmtPrinterData {
1727             tcx,
1728             // Estimated reasonable capacity to allocate upfront based on a few
1729             // benchmarks.
1730             fmt: String::with_capacity(64),
1731             empty_path: false,
1732             in_value: ns == Namespace::ValueNS,
1733             print_alloc_ids: false,
1734             used_region_names: Default::default(),
1735             region_index: 0,
1736             binder_depth: 0,
1737             printed_type_count: 0,
1738             type_length_limit,
1739             truncated: false,
1740             region_highlight_mode: RegionHighlightMode::new(tcx),
1741             ty_infer_name_resolver: None,
1742             const_infer_name_resolver: None,
1743         }))
1744     }
1745
1746     pub fn into_buffer(self) -> String {
1747         self.0.fmt
1748     }
1749 }
1750
1751 // HACK(eddyb) get rid of `def_path_str` and/or pass `Namespace` explicitly always
1752 // (but also some things just print a `DefId` generally so maybe we need this?)
1753 fn guess_def_namespace(tcx: TyCtxt<'_>, def_id: DefId) -> Namespace {
1754     match tcx.def_key(def_id).disambiguated_data.data {
1755         DefPathData::TypeNs(..) | DefPathData::CrateRoot | DefPathData::ImplTrait => {
1756             Namespace::TypeNS
1757         }
1758
1759         DefPathData::ValueNs(..)
1760         | DefPathData::AnonConst
1761         | DefPathData::ClosureExpr
1762         | DefPathData::Ctor => Namespace::ValueNS,
1763
1764         DefPathData::MacroNs(..) => Namespace::MacroNS,
1765
1766         _ => Namespace::TypeNS,
1767     }
1768 }
1769
1770 impl<'t> TyCtxt<'t> {
1771     /// Returns a string identifying this `DefId`. This string is
1772     /// suitable for user output.
1773     pub fn def_path_str(self, def_id: DefId) -> String {
1774         self.def_path_str_with_substs(def_id, &[])
1775     }
1776
1777     pub fn def_path_str_with_substs(self, def_id: DefId, substs: &'t [GenericArg<'t>]) -> String {
1778         let ns = guess_def_namespace(self, def_id);
1779         debug!("def_path_str: def_id={:?}, ns={:?}", def_id, ns);
1780         FmtPrinter::new(self, ns).print_def_path(def_id, substs).unwrap().into_buffer()
1781     }
1782
1783     pub fn value_path_str_with_substs(self, def_id: DefId, substs: &'t [GenericArg<'t>]) -> String {
1784         let ns = guess_def_namespace(self, def_id);
1785         debug!("value_path_str: def_id={:?}, ns={:?}", def_id, ns);
1786         FmtPrinter::new(self, ns).print_value_path(def_id, substs).unwrap().into_buffer()
1787     }
1788 }
1789
1790 impl fmt::Write for FmtPrinter<'_, '_> {
1791     fn write_str(&mut self, s: &str) -> fmt::Result {
1792         self.fmt.push_str(s);
1793         Ok(())
1794     }
1795 }
1796
1797 impl<'tcx> Printer<'tcx> for FmtPrinter<'_, 'tcx> {
1798     type Error = fmt::Error;
1799
1800     type Path = Self;
1801     type Region = Self;
1802     type Type = Self;
1803     type DynExistential = Self;
1804     type Const = Self;
1805
1806     fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
1807         self.tcx
1808     }
1809
1810     fn print_def_path(
1811         mut self,
1812         def_id: DefId,
1813         substs: &'tcx [GenericArg<'tcx>],
1814     ) -> Result<Self::Path, Self::Error> {
1815         define_scoped_cx!(self);
1816
1817         if substs.is_empty() {
1818             match self.try_print_trimmed_def_path(def_id)? {
1819                 (cx, true) => return Ok(cx),
1820                 (cx, false) => self = cx,
1821             }
1822
1823             match self.try_print_visible_def_path(def_id)? {
1824                 (cx, true) => return Ok(cx),
1825                 (cx, false) => self = cx,
1826             }
1827         }
1828
1829         let key = self.tcx.def_key(def_id);
1830         if let DefPathData::Impl = key.disambiguated_data.data {
1831             // Always use types for non-local impls, where types are always
1832             // available, and filename/line-number is mostly uninteresting.
1833             let use_types = !def_id.is_local() || {
1834                 // Otherwise, use filename/line-number if forced.
1835                 let force_no_types = FORCE_IMPL_FILENAME_LINE.with(|f| f.get());
1836                 !force_no_types
1837             };
1838
1839             if !use_types {
1840                 // If no type info is available, fall back to
1841                 // pretty printing some span information. This should
1842                 // only occur very early in the compiler pipeline.
1843                 let parent_def_id = DefId { index: key.parent.unwrap(), ..def_id };
1844                 let span = self.tcx.def_span(def_id);
1845
1846                 self = self.print_def_path(parent_def_id, &[])?;
1847
1848                 // HACK(eddyb) copy of `path_append` to avoid
1849                 // constructing a `DisambiguatedDefPathData`.
1850                 if !self.empty_path {
1851                     write!(self, "::")?;
1852                 }
1853                 write!(
1854                     self,
1855                     "<impl at {}>",
1856                     // This may end up in stderr diagnostics but it may also be emitted
1857                     // into MIR. Hence we use the remapped path if available
1858                     self.tcx.sess.source_map().span_to_embeddable_string(span)
1859                 )?;
1860                 self.empty_path = false;
1861
1862                 return Ok(self);
1863             }
1864         }
1865
1866         self.default_print_def_path(def_id, substs)
1867     }
1868
1869     fn print_region(self, region: ty::Region<'tcx>) -> Result<Self::Region, Self::Error> {
1870         self.pretty_print_region(region)
1871     }
1872
1873     fn print_type(mut self, ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
1874         if self.type_length_limit.value_within_limit(self.printed_type_count) {
1875             self.printed_type_count += 1;
1876             self.pretty_print_type(ty)
1877         } else {
1878             self.truncated = true;
1879             write!(self, "...")?;
1880             Ok(self)
1881         }
1882     }
1883
1884     fn print_dyn_existential(
1885         self,
1886         predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
1887     ) -> Result<Self::DynExistential, Self::Error> {
1888         self.pretty_print_dyn_existential(predicates)
1889     }
1890
1891     fn print_const(self, ct: ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
1892         self.pretty_print_const(ct, false)
1893     }
1894
1895     fn path_crate(mut self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
1896         self.empty_path = true;
1897         if cnum == LOCAL_CRATE {
1898             if self.tcx.sess.rust_2018() {
1899                 // We add the `crate::` keyword on Rust 2018, only when desired.
1900                 if SHOULD_PREFIX_WITH_CRATE.with(|flag| flag.get()) {
1901                     write!(self, "{}", kw::Crate)?;
1902                     self.empty_path = false;
1903                 }
1904             }
1905         } else {
1906             write!(self, "{}", self.tcx.crate_name(cnum))?;
1907             self.empty_path = false;
1908         }
1909         Ok(self)
1910     }
1911
1912     fn path_qualified(
1913         mut self,
1914         self_ty: Ty<'tcx>,
1915         trait_ref: Option<ty::TraitRef<'tcx>>,
1916     ) -> Result<Self::Path, Self::Error> {
1917         self = self.pretty_path_qualified(self_ty, trait_ref)?;
1918         self.empty_path = false;
1919         Ok(self)
1920     }
1921
1922     fn path_append_impl(
1923         mut self,
1924         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1925         _disambiguated_data: &DisambiguatedDefPathData,
1926         self_ty: Ty<'tcx>,
1927         trait_ref: Option<ty::TraitRef<'tcx>>,
1928     ) -> Result<Self::Path, Self::Error> {
1929         self = self.pretty_path_append_impl(
1930             |mut cx| {
1931                 cx = print_prefix(cx)?;
1932                 if !cx.empty_path {
1933                     write!(cx, "::")?;
1934                 }
1935
1936                 Ok(cx)
1937             },
1938             self_ty,
1939             trait_ref,
1940         )?;
1941         self.empty_path = false;
1942         Ok(self)
1943     }
1944
1945     fn path_append(
1946         mut self,
1947         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1948         disambiguated_data: &DisambiguatedDefPathData,
1949     ) -> Result<Self::Path, Self::Error> {
1950         self = print_prefix(self)?;
1951
1952         // Skip `::{{extern}}` blocks and `::{{constructor}}` on tuple/unit structs.
1953         if let DefPathData::ForeignMod | DefPathData::Ctor = disambiguated_data.data {
1954             return Ok(self);
1955         }
1956
1957         let name = disambiguated_data.data.name();
1958         if !self.empty_path {
1959             write!(self, "::")?;
1960         }
1961
1962         if let DefPathDataName::Named(name) = name {
1963             if Ident::with_dummy_span(name).is_raw_guess() {
1964                 write!(self, "r#")?;
1965             }
1966         }
1967
1968         let verbose = self.should_print_verbose();
1969         disambiguated_data.fmt_maybe_verbose(&mut self, verbose)?;
1970
1971         self.empty_path = false;
1972
1973         Ok(self)
1974     }
1975
1976     fn path_generic_args(
1977         mut self,
1978         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1979         args: &[GenericArg<'tcx>],
1980     ) -> Result<Self::Path, Self::Error> {
1981         self = print_prefix(self)?;
1982
1983         if args.first().is_some() {
1984             if self.in_value {
1985                 write!(self, "::")?;
1986             }
1987             self.generic_delimiters(|cx| cx.comma_sep(args.iter().cloned()))
1988         } else {
1989             Ok(self)
1990         }
1991     }
1992 }
1993
1994 impl<'tcx> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx> {
1995     fn ty_infer_name(&self, id: ty::TyVid) -> Option<Symbol> {
1996         self.0.ty_infer_name_resolver.as_ref().and_then(|func| func(id))
1997     }
1998
1999     fn reset_type_limit(&mut self) {
2000         self.printed_type_count = 0;
2001     }
2002
2003     fn const_infer_name(&self, id: ty::ConstVid<'tcx>) -> Option<Symbol> {
2004         self.0.const_infer_name_resolver.as_ref().and_then(|func| func(id))
2005     }
2006
2007     fn print_value_path(
2008         mut self,
2009         def_id: DefId,
2010         substs: &'tcx [GenericArg<'tcx>],
2011     ) -> Result<Self::Path, Self::Error> {
2012         let was_in_value = std::mem::replace(&mut self.in_value, true);
2013         self = self.print_def_path(def_id, substs)?;
2014         self.in_value = was_in_value;
2015
2016         Ok(self)
2017     }
2018
2019     fn in_binder<T>(self, value: &ty::Binder<'tcx, T>) -> Result<Self, Self::Error>
2020     where
2021         T: Print<'tcx, Self, Output = Self, Error = Self::Error> + TypeFoldable<'tcx>,
2022     {
2023         self.pretty_in_binder(value)
2024     }
2025
2026     fn wrap_binder<T, C: FnOnce(&T, Self) -> Result<Self, Self::Error>>(
2027         self,
2028         value: &ty::Binder<'tcx, T>,
2029         f: C,
2030     ) -> Result<Self, Self::Error>
2031     where
2032         T: Print<'tcx, Self, Output = Self, Error = Self::Error> + TypeFoldable<'tcx>,
2033     {
2034         self.pretty_wrap_binder(value, f)
2035     }
2036
2037     fn typed_value(
2038         mut self,
2039         f: impl FnOnce(Self) -> Result<Self, Self::Error>,
2040         t: impl FnOnce(Self) -> Result<Self, Self::Error>,
2041         conversion: &str,
2042     ) -> Result<Self::Const, Self::Error> {
2043         self.write_str("{")?;
2044         self = f(self)?;
2045         self.write_str(conversion)?;
2046         let was_in_value = std::mem::replace(&mut self.in_value, false);
2047         self = t(self)?;
2048         self.in_value = was_in_value;
2049         self.write_str("}")?;
2050         Ok(self)
2051     }
2052
2053     fn generic_delimiters(
2054         mut self,
2055         f: impl FnOnce(Self) -> Result<Self, Self::Error>,
2056     ) -> Result<Self, Self::Error> {
2057         write!(self, "<")?;
2058
2059         let was_in_value = std::mem::replace(&mut self.in_value, false);
2060         let mut inner = f(self)?;
2061         inner.in_value = was_in_value;
2062
2063         write!(inner, ">")?;
2064         Ok(inner)
2065     }
2066
2067     fn should_print_region(&self, region: ty::Region<'tcx>) -> bool {
2068         let highlight = self.region_highlight_mode;
2069         if highlight.region_highlighted(region).is_some() {
2070             return true;
2071         }
2072
2073         if self.should_print_verbose() {
2074             return true;
2075         }
2076
2077         if FORCE_TRIMMED_PATH.with(|flag| flag.get()) {
2078             return false;
2079         }
2080
2081         let identify_regions = self.tcx.sess.opts.unstable_opts.identify_regions;
2082
2083         match *region {
2084             ty::ReEarlyBound(ref data) => data.has_name(),
2085
2086             ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
2087             | ty::ReFree(ty::FreeRegion { bound_region: br, .. })
2088             | ty::RePlaceholder(ty::Placeholder { name: br, .. }) => {
2089                 if br.is_named() {
2090                     return true;
2091                 }
2092
2093                 if let Some((region, _)) = highlight.highlight_bound_region {
2094                     if br == region {
2095                         return true;
2096                     }
2097                 }
2098
2099                 false
2100             }
2101
2102             ty::ReVar(_) if identify_regions => true,
2103
2104             ty::ReVar(_) | ty::ReErased => false,
2105
2106             ty::ReStatic => true,
2107         }
2108     }
2109
2110     fn pretty_print_const_pointer<Prov: Provenance>(
2111         self,
2112         p: Pointer<Prov>,
2113         ty: Ty<'tcx>,
2114         print_ty: bool,
2115     ) -> Result<Self::Const, Self::Error> {
2116         let print = |mut this: Self| {
2117             define_scoped_cx!(this);
2118             if this.print_alloc_ids {
2119                 p!(write("{:?}", p));
2120             } else {
2121                 p!("&_");
2122             }
2123             Ok(this)
2124         };
2125         if print_ty {
2126             self.typed_value(print, |this| this.print_type(ty), ": ")
2127         } else {
2128             print(self)
2129         }
2130     }
2131 }
2132
2133 // HACK(eddyb) limited to `FmtPrinter` because of `region_highlight_mode`.
2134 impl<'tcx> FmtPrinter<'_, 'tcx> {
2135     pub fn pretty_print_region(mut self, region: ty::Region<'tcx>) -> Result<Self, fmt::Error> {
2136         define_scoped_cx!(self);
2137
2138         // Watch out for region highlights.
2139         let highlight = self.region_highlight_mode;
2140         if let Some(n) = highlight.region_highlighted(region) {
2141             p!(write("'{}", n));
2142             return Ok(self);
2143         }
2144
2145         if self.should_print_verbose() {
2146             p!(write("{:?}", region));
2147             return Ok(self);
2148         }
2149
2150         let identify_regions = self.tcx.sess.opts.unstable_opts.identify_regions;
2151
2152         // These printouts are concise. They do not contain all the information
2153         // the user might want to diagnose an error, but there is basically no way
2154         // to fit that into a short string. Hence the recommendation to use
2155         // `explain_region()` or `note_and_explain_region()`.
2156         match *region {
2157             ty::ReEarlyBound(ref data) => {
2158                 if data.name != kw::Empty {
2159                     p!(write("{}", data.name));
2160                     return Ok(self);
2161                 }
2162             }
2163             ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
2164             | ty::ReFree(ty::FreeRegion { bound_region: br, .. })
2165             | ty::RePlaceholder(ty::Placeholder { name: br, .. }) => {
2166                 if let ty::BrNamed(_, name) = br && br.is_named() {
2167                     p!(write("{}", name));
2168                     return Ok(self);
2169                 }
2170
2171                 if let Some((region, counter)) = highlight.highlight_bound_region {
2172                     if br == region {
2173                         p!(write("'{}", counter));
2174                         return Ok(self);
2175                     }
2176                 }
2177             }
2178             ty::ReVar(region_vid) if identify_regions => {
2179                 p!(write("{:?}", region_vid));
2180                 return Ok(self);
2181             }
2182             ty::ReVar(_) => {}
2183             ty::ReErased => {}
2184             ty::ReStatic => {
2185                 p!("'static");
2186                 return Ok(self);
2187             }
2188         }
2189
2190         p!("'_");
2191
2192         Ok(self)
2193     }
2194 }
2195
2196 /// Folds through bound vars and placeholders, naming them
2197 struct RegionFolder<'a, 'tcx> {
2198     tcx: TyCtxt<'tcx>,
2199     current_index: ty::DebruijnIndex,
2200     region_map: BTreeMap<ty::BoundRegion, ty::Region<'tcx>>,
2201     name: &'a mut (
2202                 dyn FnMut(
2203         Option<ty::DebruijnIndex>, // Debruijn index of the folded late-bound region
2204         ty::DebruijnIndex,         // Index corresponding to binder level
2205         ty::BoundRegion,
2206     ) -> ty::Region<'tcx>
2207                     + 'a
2208             ),
2209 }
2210
2211 impl<'a, 'tcx> ty::TypeFolder<'tcx> for RegionFolder<'a, 'tcx> {
2212     fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
2213         self.tcx
2214     }
2215
2216     fn fold_binder<T: TypeFoldable<'tcx>>(
2217         &mut self,
2218         t: ty::Binder<'tcx, T>,
2219     ) -> ty::Binder<'tcx, T> {
2220         self.current_index.shift_in(1);
2221         let t = t.super_fold_with(self);
2222         self.current_index.shift_out(1);
2223         t
2224     }
2225
2226     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
2227         match *t.kind() {
2228             _ if t.has_vars_bound_at_or_above(self.current_index) || t.has_placeholders() => {
2229                 return t.super_fold_with(self);
2230             }
2231             _ => {}
2232         }
2233         t
2234     }
2235
2236     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
2237         let name = &mut self.name;
2238         let region = match *r {
2239             ty::ReLateBound(db, br) if db >= self.current_index => {
2240                 *self.region_map.entry(br).or_insert_with(|| name(Some(db), self.current_index, br))
2241             }
2242             ty::RePlaceholder(ty::PlaceholderRegion { name: kind, .. }) => {
2243                 // If this is an anonymous placeholder, don't rename. Otherwise, in some
2244                 // async fns, we get a `for<'r> Send` bound
2245                 match kind {
2246                     ty::BrAnon(..) | ty::BrEnv => r,
2247                     _ => {
2248                         // Index doesn't matter, since this is just for naming and these never get bound
2249                         let br = ty::BoundRegion { var: ty::BoundVar::from_u32(0), kind };
2250                         *self
2251                             .region_map
2252                             .entry(br)
2253                             .or_insert_with(|| name(None, self.current_index, br))
2254                     }
2255                 }
2256             }
2257             _ => return r,
2258         };
2259         if let ty::ReLateBound(debruijn1, br) = *region {
2260             assert_eq!(debruijn1, ty::INNERMOST);
2261             self.tcx.mk_region(ty::ReLateBound(self.current_index, br))
2262         } else {
2263             region
2264         }
2265     }
2266 }
2267
2268 // HACK(eddyb) limited to `FmtPrinter` because of `binder_depth`,
2269 // `region_index` and `used_region_names`.
2270 impl<'tcx> FmtPrinter<'_, 'tcx> {
2271     pub fn name_all_regions<T>(
2272         mut self,
2273         value: &ty::Binder<'tcx, T>,
2274     ) -> Result<(Self, T, BTreeMap<ty::BoundRegion, ty::Region<'tcx>>), fmt::Error>
2275     where
2276         T: Print<'tcx, Self, Output = Self, Error = fmt::Error> + TypeFoldable<'tcx>,
2277     {
2278         fn name_by_region_index(
2279             index: usize,
2280             available_names: &mut Vec<Symbol>,
2281             num_available: usize,
2282         ) -> Symbol {
2283             if let Some(name) = available_names.pop() {
2284                 name
2285             } else {
2286                 Symbol::intern(&format!("'z{}", index - num_available))
2287             }
2288         }
2289
2290         debug!("name_all_regions");
2291
2292         // Replace any anonymous late-bound regions with named
2293         // variants, using new unique identifiers, so that we can
2294         // clearly differentiate between named and unnamed regions in
2295         // the output. We'll probably want to tweak this over time to
2296         // decide just how much information to give.
2297         if self.binder_depth == 0 {
2298             self.prepare_region_info(value);
2299         }
2300
2301         debug!("self.used_region_names: {:?}", &self.used_region_names);
2302
2303         let mut empty = true;
2304         let mut start_or_continue = |cx: &mut Self, start: &str, cont: &str| {
2305             let w = if empty {
2306                 empty = false;
2307                 start
2308             } else {
2309                 cont
2310             };
2311             let _ = write!(cx, "{}", w);
2312         };
2313         let do_continue = |cx: &mut Self, cont: Symbol| {
2314             let _ = write!(cx, "{}", cont);
2315         };
2316
2317         define_scoped_cx!(self);
2318
2319         let possible_names = ('a'..='z').rev().map(|s| Symbol::intern(&format!("'{s}")));
2320
2321         let mut available_names = possible_names
2322             .filter(|name| !self.used_region_names.contains(&name))
2323             .collect::<Vec<_>>();
2324         debug!(?available_names);
2325         let num_available = available_names.len();
2326
2327         let mut region_index = self.region_index;
2328         let mut next_name = |this: &Self| {
2329             let mut name;
2330
2331             loop {
2332                 name = name_by_region_index(region_index, &mut available_names, num_available);
2333                 region_index += 1;
2334
2335                 if !this.used_region_names.contains(&name) {
2336                     break;
2337                 }
2338             }
2339
2340             name
2341         };
2342
2343         // If we want to print verbosely, then print *all* binders, even if they
2344         // aren't named. Eventually, we might just want this as the default, but
2345         // this is not *quite* right and changes the ordering of some output
2346         // anyways.
2347         let (new_value, map) = if self.should_print_verbose() {
2348             for var in value.bound_vars().iter() {
2349                 start_or_continue(&mut self, "for<", ", ");
2350                 write!(self, "{:?}", var)?;
2351             }
2352             start_or_continue(&mut self, "", "> ");
2353             (value.clone().skip_binder(), BTreeMap::default())
2354         } else {
2355             let tcx = self.tcx;
2356
2357             let trim_path = FORCE_TRIMMED_PATH.with(|flag| flag.get());
2358             // Closure used in `RegionFolder` to create names for anonymous late-bound
2359             // regions. We use two `DebruijnIndex`es (one for the currently folded
2360             // late-bound region and the other for the binder level) to determine
2361             // whether a name has already been created for the currently folded region,
2362             // see issue #102392.
2363             let mut name = |lifetime_idx: Option<ty::DebruijnIndex>,
2364                             binder_level_idx: ty::DebruijnIndex,
2365                             br: ty::BoundRegion| {
2366                 let (name, kind) = match br.kind {
2367                     ty::BrAnon(..) | ty::BrEnv => {
2368                         let name = next_name(&self);
2369
2370                         if let Some(lt_idx) = lifetime_idx {
2371                             if lt_idx > binder_level_idx {
2372                                 let kind = ty::BrNamed(CRATE_DEF_ID.to_def_id(), name);
2373                                 return tcx.mk_region(ty::ReLateBound(
2374                                     ty::INNERMOST,
2375                                     ty::BoundRegion { var: br.var, kind },
2376                                 ));
2377                             }
2378                         }
2379
2380                         (name, ty::BrNamed(CRATE_DEF_ID.to_def_id(), name))
2381                     }
2382                     ty::BrNamed(def_id, kw::UnderscoreLifetime | kw::Empty) => {
2383                         let name = next_name(&self);
2384
2385                         if let Some(lt_idx) = lifetime_idx {
2386                             if lt_idx > binder_level_idx {
2387                                 let kind = ty::BrNamed(def_id, name);
2388                                 return tcx.mk_region(ty::ReLateBound(
2389                                     ty::INNERMOST,
2390                                     ty::BoundRegion { var: br.var, kind },
2391                                 ));
2392                             }
2393                         }
2394
2395                         (name, ty::BrNamed(def_id, name))
2396                     }
2397                     ty::BrNamed(_, name) => {
2398                         if let Some(lt_idx) = lifetime_idx {
2399                             if lt_idx > binder_level_idx {
2400                                 let kind = br.kind;
2401                                 return tcx.mk_region(ty::ReLateBound(
2402                                     ty::INNERMOST,
2403                                     ty::BoundRegion { var: br.var, kind },
2404                                 ));
2405                             }
2406                         }
2407
2408                         (name, br.kind)
2409                     }
2410                 };
2411
2412                 if !trim_path {
2413                     start_or_continue(&mut self, "for<", ", ");
2414                     do_continue(&mut self, name);
2415                 }
2416                 tcx.mk_region(ty::ReLateBound(ty::INNERMOST, ty::BoundRegion { var: br.var, kind }))
2417             };
2418             let mut folder = RegionFolder {
2419                 tcx,
2420                 current_index: ty::INNERMOST,
2421                 name: &mut name,
2422                 region_map: BTreeMap::new(),
2423             };
2424             let new_value = value.clone().skip_binder().fold_with(&mut folder);
2425             let region_map = folder.region_map;
2426             if !trim_path {
2427                 start_or_continue(&mut self, "", "> ");
2428             }
2429             (new_value, region_map)
2430         };
2431
2432         self.binder_depth += 1;
2433         self.region_index = region_index;
2434         Ok((self, new_value, map))
2435     }
2436
2437     pub fn pretty_in_binder<T>(self, value: &ty::Binder<'tcx, T>) -> Result<Self, fmt::Error>
2438     where
2439         T: Print<'tcx, Self, Output = Self, Error = fmt::Error> + TypeFoldable<'tcx>,
2440     {
2441         let old_region_index = self.region_index;
2442         let (new, new_value, _) = self.name_all_regions(value)?;
2443         let mut inner = new_value.print(new)?;
2444         inner.region_index = old_region_index;
2445         inner.binder_depth -= 1;
2446         Ok(inner)
2447     }
2448
2449     pub fn pretty_wrap_binder<T, C: FnOnce(&T, Self) -> Result<Self, fmt::Error>>(
2450         self,
2451         value: &ty::Binder<'tcx, T>,
2452         f: C,
2453     ) -> Result<Self, fmt::Error>
2454     where
2455         T: Print<'tcx, Self, Output = Self, Error = fmt::Error> + TypeFoldable<'tcx>,
2456     {
2457         let old_region_index = self.region_index;
2458         let (new, new_value, _) = self.name_all_regions(value)?;
2459         let mut inner = f(&new_value, new)?;
2460         inner.region_index = old_region_index;
2461         inner.binder_depth -= 1;
2462         Ok(inner)
2463     }
2464
2465     fn prepare_region_info<T>(&mut self, value: &ty::Binder<'tcx, T>)
2466     where
2467         T: TypeVisitable<'tcx>,
2468     {
2469         struct RegionNameCollector<'tcx> {
2470             used_region_names: FxHashSet<Symbol>,
2471             type_collector: SsoHashSet<Ty<'tcx>>,
2472         }
2473
2474         impl<'tcx> RegionNameCollector<'tcx> {
2475             fn new() -> Self {
2476                 RegionNameCollector {
2477                     used_region_names: Default::default(),
2478                     type_collector: SsoHashSet::new(),
2479                 }
2480             }
2481         }
2482
2483         impl<'tcx> ty::visit::TypeVisitor<'tcx> for RegionNameCollector<'tcx> {
2484             type BreakTy = ();
2485
2486             fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
2487                 trace!("address: {:p}", r.0.0);
2488
2489                 // Collect all named lifetimes. These allow us to prevent duplication
2490                 // of already existing lifetime names when introducing names for
2491                 // anonymous late-bound regions.
2492                 if let Some(name) = r.get_name() {
2493                     self.used_region_names.insert(name);
2494                 }
2495
2496                 r.super_visit_with(self)
2497             }
2498
2499             // We collect types in order to prevent really large types from compiling for
2500             // a really long time. See issue #83150 for why this is necessary.
2501             fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
2502                 let not_previously_inserted = self.type_collector.insert(ty);
2503                 if not_previously_inserted {
2504                     ty.super_visit_with(self)
2505                 } else {
2506                     ControlFlow::Continue(())
2507                 }
2508             }
2509         }
2510
2511         let mut collector = RegionNameCollector::new();
2512         value.visit_with(&mut collector);
2513         self.used_region_names = collector.used_region_names;
2514         self.region_index = 0;
2515     }
2516 }
2517
2518 impl<'tcx, T, P: PrettyPrinter<'tcx>> Print<'tcx, P> for ty::Binder<'tcx, T>
2519 where
2520     T: Print<'tcx, P, Output = P, Error = P::Error> + TypeFoldable<'tcx>,
2521 {
2522     type Output = P;
2523     type Error = P::Error;
2524
2525     fn print(&self, cx: P) -> Result<Self::Output, Self::Error> {
2526         cx.in_binder(self)
2527     }
2528 }
2529
2530 impl<'tcx, T, U, P: PrettyPrinter<'tcx>> Print<'tcx, P> for ty::OutlivesPredicate<T, U>
2531 where
2532     T: Print<'tcx, P, Output = P, Error = P::Error>,
2533     U: Print<'tcx, P, Output = P, Error = P::Error>,
2534 {
2535     type Output = P;
2536     type Error = P::Error;
2537     fn print(&self, mut cx: P) -> Result<Self::Output, Self::Error> {
2538         define_scoped_cx!(cx);
2539         p!(print(self.0), ": ", print(self.1));
2540         Ok(cx)
2541     }
2542 }
2543
2544 macro_rules! forward_display_to_print {
2545     ($($ty:ty),+) => {
2546         // Some of the $ty arguments may not actually use 'tcx
2547         $(#[allow(unused_lifetimes)] impl<'tcx> fmt::Display for $ty {
2548             fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2549                 ty::tls::with(|tcx| {
2550                     let cx = tcx.lift(*self)
2551                         .expect("could not lift for printing")
2552                         .print(FmtPrinter::new(tcx, Namespace::TypeNS))?;
2553                     f.write_str(&cx.into_buffer())?;
2554                     Ok(())
2555                 })
2556             }
2557         })+
2558     };
2559 }
2560
2561 macro_rules! define_print_and_forward_display {
2562     (($self:ident, $cx:ident): $($ty:ty $print:block)+) => {
2563         $(impl<'tcx, P: PrettyPrinter<'tcx>> Print<'tcx, P> for $ty {
2564             type Output = P;
2565             type Error = fmt::Error;
2566             fn print(&$self, $cx: P) -> Result<Self::Output, Self::Error> {
2567                 #[allow(unused_mut)]
2568                 let mut $cx = $cx;
2569                 define_scoped_cx!($cx);
2570                 let _: () = $print;
2571                 #[allow(unreachable_code)]
2572                 Ok($cx)
2573             }
2574         })+
2575
2576         forward_display_to_print!($($ty),+);
2577     };
2578 }
2579
2580 /// Wrapper type for `ty::TraitRef` which opts-in to pretty printing only
2581 /// the trait path. That is, it will print `Trait<U>` instead of
2582 /// `<T as Trait<U>>`.
2583 #[derive(Copy, Clone, TypeFoldable, TypeVisitable, Lift)]
2584 pub struct TraitRefPrintOnlyTraitPath<'tcx>(ty::TraitRef<'tcx>);
2585
2586 impl<'tcx> fmt::Debug for TraitRefPrintOnlyTraitPath<'tcx> {
2587     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2588         fmt::Display::fmt(self, f)
2589     }
2590 }
2591
2592 /// Wrapper type for `ty::TraitRef` which opts-in to pretty printing only
2593 /// the trait name. That is, it will print `Trait` instead of
2594 /// `<T as Trait<U>>`.
2595 #[derive(Copy, Clone, TypeFoldable, TypeVisitable, Lift)]
2596 pub struct TraitRefPrintOnlyTraitName<'tcx>(ty::TraitRef<'tcx>);
2597
2598 impl<'tcx> fmt::Debug for TraitRefPrintOnlyTraitName<'tcx> {
2599     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2600         fmt::Display::fmt(self, f)
2601     }
2602 }
2603
2604 impl<'tcx> ty::TraitRef<'tcx> {
2605     pub fn print_only_trait_path(self) -> TraitRefPrintOnlyTraitPath<'tcx> {
2606         TraitRefPrintOnlyTraitPath(self)
2607     }
2608
2609     pub fn print_only_trait_name(self) -> TraitRefPrintOnlyTraitName<'tcx> {
2610         TraitRefPrintOnlyTraitName(self)
2611     }
2612 }
2613
2614 impl<'tcx> ty::Binder<'tcx, ty::TraitRef<'tcx>> {
2615     pub fn print_only_trait_path(self) -> ty::Binder<'tcx, TraitRefPrintOnlyTraitPath<'tcx>> {
2616         self.map_bound(|tr| tr.print_only_trait_path())
2617     }
2618 }
2619
2620 #[derive(Copy, Clone, TypeFoldable, TypeVisitable, Lift)]
2621 pub struct TraitPredPrintModifiersAndPath<'tcx>(ty::TraitPredicate<'tcx>);
2622
2623 impl<'tcx> fmt::Debug for TraitPredPrintModifiersAndPath<'tcx> {
2624     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2625         fmt::Display::fmt(self, f)
2626     }
2627 }
2628
2629 impl<'tcx> ty::TraitPredicate<'tcx> {
2630     pub fn print_modifiers_and_trait_path(self) -> TraitPredPrintModifiersAndPath<'tcx> {
2631         TraitPredPrintModifiersAndPath(self)
2632     }
2633 }
2634
2635 impl<'tcx> ty::PolyTraitPredicate<'tcx> {
2636     pub fn print_modifiers_and_trait_path(
2637         self,
2638     ) -> ty::Binder<'tcx, TraitPredPrintModifiersAndPath<'tcx>> {
2639         self.map_bound(TraitPredPrintModifiersAndPath)
2640     }
2641 }
2642
2643 #[derive(Debug, Copy, Clone, TypeFoldable, TypeVisitable, Lift)]
2644 pub struct PrintClosureAsImpl<'tcx> {
2645     pub closure: ty::ClosureSubsts<'tcx>,
2646 }
2647
2648 forward_display_to_print! {
2649     ty::Region<'tcx>,
2650     Ty<'tcx>,
2651     &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
2652     ty::Const<'tcx>,
2653
2654     // HACK(eddyb) these are exhaustive instead of generic,
2655     // because `for<'tcx>` isn't possible yet.
2656     ty::PolyExistentialPredicate<'tcx>,
2657     ty::Binder<'tcx, ty::TraitRef<'tcx>>,
2658     ty::Binder<'tcx, ty::ExistentialTraitRef<'tcx>>,
2659     ty::Binder<'tcx, TraitRefPrintOnlyTraitPath<'tcx>>,
2660     ty::Binder<'tcx, TraitRefPrintOnlyTraitName<'tcx>>,
2661     ty::Binder<'tcx, ty::FnSig<'tcx>>,
2662     ty::Binder<'tcx, ty::TraitPredicate<'tcx>>,
2663     ty::Binder<'tcx, TraitPredPrintModifiersAndPath<'tcx>>,
2664     ty::Binder<'tcx, ty::SubtypePredicate<'tcx>>,
2665     ty::Binder<'tcx, ty::ProjectionPredicate<'tcx>>,
2666     ty::Binder<'tcx, ty::OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>>,
2667     ty::Binder<'tcx, ty::OutlivesPredicate<ty::Region<'tcx>, ty::Region<'tcx>>>,
2668
2669     ty::OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>,
2670     ty::OutlivesPredicate<ty::Region<'tcx>, ty::Region<'tcx>>
2671 }
2672
2673 define_print_and_forward_display! {
2674     (self, cx):
2675
2676     &'tcx ty::List<Ty<'tcx>> {
2677         p!("{{", comma_sep(self.iter()), "}}")
2678     }
2679
2680     ty::TypeAndMut<'tcx> {
2681         p!(write("{}", self.mutbl.prefix_str()), print(self.ty))
2682     }
2683
2684     ty::ExistentialTraitRef<'tcx> {
2685         // Use a type that can't appear in defaults of type parameters.
2686         let dummy_self = cx.tcx().mk_ty_infer(ty::FreshTy(0));
2687         let trait_ref = self.with_self_ty(cx.tcx(), dummy_self);
2688         p!(print(trait_ref.print_only_trait_path()))
2689     }
2690
2691     ty::ExistentialProjection<'tcx> {
2692         let name = cx.tcx().associated_item(self.def_id).name;
2693         p!(write("{} = ", name), print(self.term))
2694     }
2695
2696     ty::ExistentialPredicate<'tcx> {
2697         match *self {
2698             ty::ExistentialPredicate::Trait(x) => p!(print(x)),
2699             ty::ExistentialPredicate::Projection(x) => p!(print(x)),
2700             ty::ExistentialPredicate::AutoTrait(def_id) => {
2701                 p!(print_def_path(def_id, &[]));
2702             }
2703         }
2704     }
2705
2706     ty::FnSig<'tcx> {
2707         p!(write("{}", self.unsafety.prefix_str()));
2708
2709         if self.abi != Abi::Rust {
2710             p!(write("extern {} ", self.abi));
2711         }
2712
2713         p!("fn", pretty_fn_sig(self.inputs(), self.c_variadic, self.output()));
2714     }
2715
2716     ty::TraitRef<'tcx> {
2717         p!(write("<{} as {}>", self.self_ty(), self.print_only_trait_path()))
2718     }
2719
2720     TraitRefPrintOnlyTraitPath<'tcx> {
2721         p!(print_def_path(self.0.def_id, self.0.substs));
2722     }
2723
2724     TraitRefPrintOnlyTraitName<'tcx> {
2725         p!(print_def_path(self.0.def_id, &[]));
2726     }
2727
2728     TraitPredPrintModifiersAndPath<'tcx> {
2729         if let ty::BoundConstness::ConstIfConst = self.0.constness {
2730             p!("~const ")
2731         }
2732
2733         if let ty::ImplPolarity::Negative = self.0.polarity {
2734             p!("!")
2735         }
2736
2737         p!(print(self.0.trait_ref.print_only_trait_path()));
2738     }
2739
2740     PrintClosureAsImpl<'tcx> {
2741         p!(pretty_closure_as_impl(self.closure))
2742     }
2743
2744     ty::ParamTy {
2745         p!(write("{}", self.name))
2746     }
2747
2748     ty::ParamConst {
2749         p!(write("{}", self.name))
2750     }
2751
2752     ty::SubtypePredicate<'tcx> {
2753         p!(print(self.a), " <: ");
2754         cx.reset_type_limit();
2755         p!(print(self.b))
2756     }
2757
2758     ty::CoercePredicate<'tcx> {
2759         p!(print(self.a), " -> ");
2760         cx.reset_type_limit();
2761         p!(print(self.b))
2762     }
2763
2764     ty::TraitPredicate<'tcx> {
2765         p!(print(self.trait_ref.self_ty()), ": ");
2766         if let ty::BoundConstness::ConstIfConst = self.constness && cx.tcx().features().const_trait_impl {
2767             p!("~const ");
2768         }
2769         p!(print(self.trait_ref.print_only_trait_path()))
2770     }
2771
2772     ty::ProjectionPredicate<'tcx> {
2773         p!(print(self.projection_ty), " == ");
2774         cx.reset_type_limit();
2775         p!(print(self.term))
2776     }
2777
2778     ty::Term<'tcx> {
2779       match self.unpack() {
2780         ty::TermKind::Ty(ty) => p!(print(ty)),
2781         ty::TermKind::Const(c) => p!(print(c)),
2782       }
2783     }
2784
2785     ty::AliasTy<'tcx> {
2786         p!(print_def_path(self.def_id, self.substs));
2787     }
2788
2789     ty::ClosureKind {
2790         match *self {
2791             ty::ClosureKind::Fn => p!("Fn"),
2792             ty::ClosureKind::FnMut => p!("FnMut"),
2793             ty::ClosureKind::FnOnce => p!("FnOnce"),
2794         }
2795     }
2796
2797     ty::Predicate<'tcx> {
2798         let binder = self.kind();
2799         p!(print(binder))
2800     }
2801
2802     ty::PredicateKind<'tcx> {
2803         match *self {
2804             ty::PredicateKind::Clause(ty::Clause::Trait(ref data)) => {
2805                 p!(print(data))
2806             }
2807             ty::PredicateKind::Subtype(predicate) => p!(print(predicate)),
2808             ty::PredicateKind::Coerce(predicate) => p!(print(predicate)),
2809             ty::PredicateKind::Clause(ty::Clause::RegionOutlives(predicate)) => p!(print(predicate)),
2810             ty::PredicateKind::Clause(ty::Clause::TypeOutlives(predicate)) => p!(print(predicate)),
2811             ty::PredicateKind::Clause(ty::Clause::Projection(predicate)) => p!(print(predicate)),
2812             ty::PredicateKind::WellFormed(arg) => p!(print(arg), " well-formed"),
2813             ty::PredicateKind::ObjectSafe(trait_def_id) => {
2814                 p!("the trait `", print_def_path(trait_def_id, &[]), "` is object-safe")
2815             }
2816             ty::PredicateKind::ClosureKind(closure_def_id, _closure_substs, kind) => {
2817                 p!("the closure `",
2818                 print_value_path(closure_def_id, &[]),
2819                 write("` implements the trait `{}`", kind))
2820             }
2821             ty::PredicateKind::ConstEvaluatable(ct) => {
2822                 p!("the constant `", print(ct), "` can be evaluated")
2823             }
2824             ty::PredicateKind::ConstEquate(c1, c2) => {
2825                 p!("the constant `", print(c1), "` equals `", print(c2), "`")
2826             }
2827             ty::PredicateKind::TypeWellFormedFromEnv(ty) => {
2828                 p!("the type `", print(ty), "` is found in the environment")
2829             }
2830             ty::PredicateKind::Ambiguous => p!("ambiguous"),
2831         }
2832     }
2833
2834     GenericArg<'tcx> {
2835         match self.unpack() {
2836             GenericArgKind::Lifetime(lt) => p!(print(lt)),
2837             GenericArgKind::Type(ty) => p!(print(ty)),
2838             GenericArgKind::Const(ct) => p!(print(ct)),
2839         }
2840     }
2841 }
2842
2843 fn for_each_def(tcx: TyCtxt<'_>, mut collect_fn: impl for<'b> FnMut(&'b Ident, Namespace, DefId)) {
2844     // Iterate all local crate items no matter where they are defined.
2845     let hir = tcx.hir();
2846     for id in hir.items() {
2847         if matches!(tcx.def_kind(id.owner_id), DefKind::Use) {
2848             continue;
2849         }
2850
2851         let item = hir.item(id);
2852         if item.ident.name == kw::Empty {
2853             continue;
2854         }
2855
2856         let def_id = item.owner_id.to_def_id();
2857         let ns = tcx.def_kind(def_id).ns().unwrap_or(Namespace::TypeNS);
2858         collect_fn(&item.ident, ns, def_id);
2859     }
2860
2861     // Now take care of extern crate items.
2862     let queue = &mut Vec::new();
2863     let mut seen_defs: DefIdSet = Default::default();
2864
2865     for &cnum in tcx.crates(()).iter() {
2866         let def_id = cnum.as_def_id();
2867
2868         // Ignore crates that are not direct dependencies.
2869         match tcx.extern_crate(def_id) {
2870             None => continue,
2871             Some(extern_crate) => {
2872                 if !extern_crate.is_direct() {
2873                     continue;
2874                 }
2875             }
2876         }
2877
2878         queue.push(def_id);
2879     }
2880
2881     // Iterate external crate defs but be mindful about visibility
2882     while let Some(def) = queue.pop() {
2883         for child in tcx.module_children(def).iter() {
2884             if !child.vis.is_public() {
2885                 continue;
2886             }
2887
2888             match child.res {
2889                 def::Res::Def(DefKind::AssocTy, _) => {}
2890                 def::Res::Def(DefKind::TyAlias, _) => {}
2891                 def::Res::Def(defkind, def_id) => {
2892                     if let Some(ns) = defkind.ns() {
2893                         collect_fn(&child.ident, ns, def_id);
2894                     }
2895
2896                     if matches!(defkind, DefKind::Mod | DefKind::Enum | DefKind::Trait)
2897                         && seen_defs.insert(def_id)
2898                     {
2899                         queue.push(def_id);
2900                     }
2901                 }
2902                 _ => {}
2903             }
2904         }
2905     }
2906 }
2907
2908 /// The purpose of this function is to collect public symbols names that are unique across all
2909 /// crates in the build. Later, when printing about types we can use those names instead of the
2910 /// full exported path to them.
2911 ///
2912 /// So essentially, if a symbol name can only be imported from one place for a type, and as
2913 /// long as it was not glob-imported anywhere in the current crate, we can trim its printed
2914 /// path and print only the name.
2915 ///
2916 /// This has wide implications on error messages with types, for example, shortening
2917 /// `std::vec::Vec` to just `Vec`, as long as there is no other `Vec` importable anywhere.
2918 ///
2919 /// The implementation uses similar import discovery logic to that of 'use' suggestions.
2920 ///
2921 /// See also [`DelayDm`](rustc_error_messages::DelayDm) and [`with_no_trimmed_paths`].
2922 fn trimmed_def_paths(tcx: TyCtxt<'_>, (): ()) -> FxHashMap<DefId, Symbol> {
2923     let mut map: FxHashMap<DefId, Symbol> = FxHashMap::default();
2924
2925     if let TrimmedDefPaths::GoodPath = tcx.sess.opts.trimmed_def_paths {
2926         // Trimming paths is expensive and not optimized, since we expect it to only be used for error reporting.
2927         //
2928         // For good paths causing this bug, the `rustc_middle::ty::print::with_no_trimmed_paths`
2929         // wrapper can be used to suppress this query, in exchange for full paths being formatted.
2930         tcx.sess.delay_good_path_bug(
2931             "trimmed_def_paths constructed but no error emitted; use `DelayDm` for lints or `with_no_trimmed_paths` for debugging",
2932         );
2933     }
2934
2935     let unique_symbols_rev: &mut FxHashMap<(Namespace, Symbol), Option<DefId>> =
2936         &mut FxHashMap::default();
2937
2938     for symbol_set in tcx.resolutions(()).glob_map.values() {
2939         for symbol in symbol_set {
2940             unique_symbols_rev.insert((Namespace::TypeNS, *symbol), None);
2941             unique_symbols_rev.insert((Namespace::ValueNS, *symbol), None);
2942             unique_symbols_rev.insert((Namespace::MacroNS, *symbol), None);
2943         }
2944     }
2945
2946     for_each_def(tcx, |ident, ns, def_id| {
2947         use std::collections::hash_map::Entry::{Occupied, Vacant};
2948
2949         match unique_symbols_rev.entry((ns, ident.name)) {
2950             Occupied(mut v) => match v.get() {
2951                 None => {}
2952                 Some(existing) => {
2953                     if *existing != def_id {
2954                         v.insert(None);
2955                     }
2956                 }
2957             },
2958             Vacant(v) => {
2959                 v.insert(Some(def_id));
2960             }
2961         }
2962     });
2963
2964     for ((_, symbol), opt_def_id) in unique_symbols_rev.drain() {
2965         use std::collections::hash_map::Entry::{Occupied, Vacant};
2966
2967         if let Some(def_id) = opt_def_id {
2968             match map.entry(def_id) {
2969                 Occupied(mut v) => {
2970                     // A single DefId can be known under multiple names (e.g.,
2971                     // with a `pub use ... as ...;`). We need to ensure that the
2972                     // name placed in this map is chosen deterministically, so
2973                     // if we find multiple names (`symbol`) resolving to the
2974                     // same `def_id`, we prefer the lexicographically smallest
2975                     // name.
2976                     //
2977                     // Any stable ordering would be fine here though.
2978                     if *v.get() != symbol {
2979                         if v.get().as_str() > symbol.as_str() {
2980                             v.insert(symbol);
2981                         }
2982                     }
2983                 }
2984                 Vacant(v) => {
2985                     v.insert(symbol);
2986                 }
2987             }
2988         }
2989     }
2990
2991     map
2992 }
2993
2994 pub fn provide(providers: &mut ty::query::Providers) {
2995     *providers = ty::query::Providers { trimmed_def_paths, ..*providers };
2996 }
2997
2998 #[derive(Default)]
2999 pub struct OpaqueFnEntry<'tcx> {
3000     // The trait ref is already stored as a key, so just track if we have it as a real predicate
3001     has_fn_once: bool,
3002     fn_mut_trait_ref: Option<ty::PolyTraitRef<'tcx>>,
3003     fn_trait_ref: Option<ty::PolyTraitRef<'tcx>>,
3004     return_ty: Option<ty::Binder<'tcx, Term<'tcx>>>,
3005 }