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                 self.write_str(symbol.as_str())?;
 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().bound_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 => self.pretty_print_bound_var(debruijn, bound_ty.var)?,
 702                 ty::BoundTyKind::Param(p) => p!(write("{}", p)),
 703             },
 704             ty::Adt(def, substs) => {
 705                 p!(print_def_path(def.did(), substs));
 706             }
 707             ty::Dynamic(data, r, repr) => {
 708                 let print_r = self.should_print_region(r);
 709                 if print_r {
 710                     p!("(");
 711                 }
 712                 match repr {
 713                     ty::Dyn => p!("dyn "),
 714                     ty::DynStar => p!("dyn* "),
 715                 }
 716                 p!(print(data));
 717                 if print_r {
 718                     p!(" + ", print(r), ")");
 719                 }
 720             }
 721             ty::Foreign(def_id) => {
 722                 p!(print_def_path(def_id, &[]));
 723             }
 724             ty::Alias(ty::Projection, ref data) => {
 725                 if !(self.should_print_verbose() || NO_QUERIES.with(|q| q.get()))
 726                     && self.tcx().def_kind(data.def_id) == DefKind::ImplTraitPlaceholder
 727                 {
 728                     return self.pretty_print_opaque_impl_type(data.def_id, data.substs);
 729                 } else {
 730                     p!(print(data))
 731                 }
 732             }
 733             ty::Placeholder(placeholder) => p!(write("Placeholder({:?})", placeholder)),
 734             ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
 735                 // FIXME(eddyb) print this with `print_def_path`.
 736                 // We use verbose printing in 'NO_QUERIES' mode, to
 737                 // avoid needing to call `predicates_of`. This should
 738                 // only affect certain debug messages (e.g. messages printed
 739                 // from `rustc_middle::ty` during the computation of `tcx.predicates_of`),
 740                 // and should have no effect on any compiler output.
 741                 if self.should_print_verbose() || NO_QUERIES.with(|q| q.get()) {
 742                     p!(write("Opaque({:?}, {:?})", def_id, substs));
 743                     return Ok(self);
 744                 }
 745
 746                 let parent = self.tcx().parent(def_id);
 747                 match self.tcx().def_kind(parent) {
 748                     DefKind::TyAlias | DefKind::AssocTy => {
 749                         if let ty::Alias(ty::Opaque, ty::AliasTy { def_id: d, .. }) =
 750                             *self.tcx().type_of(parent).kind()
 751                         {
 752                             if d == def_id {
 753                                 // If the type alias directly starts with the `impl` of the
 754                                 // opaque type we're printing, then skip the `::{opaque#1}`.
 755                                 p!(print_def_path(parent, substs));
 756                                 return Ok(self);
 757                             }
 758                         }
 759                         // Complex opaque type, e.g. `type Foo = (i32, impl Debug);`
 760                         p!(print_def_path(def_id, substs));
 761                         return Ok(self);
 762                     }
 763                     _ => return self.pretty_print_opaque_impl_type(def_id, substs),
 764                 }
 765             }
 766             ty::Str => p!("str"),
 767             ty::Generator(did, substs, movability) => {
 768                 p!(write("["));
 769                 let generator_kind = self.tcx().generator_kind(did).unwrap();
 770                 let should_print_movability =
 771                     self.should_print_verbose() || generator_kind == hir::GeneratorKind::Gen;
 772
 773                 if should_print_movability {
 774                     match movability {
 775                         hir::Movability::Movable => {}
 776                         hir::Movability::Static => p!("static "),
 777                     }
 778                 }
 779
 780                 if !self.should_print_verbose() {
 781                     p!(write("{}", generator_kind));
 782                     // FIXME(eddyb) should use `def_span`.
 783                     if let Some(did) = did.as_local() {
 784                         let span = self.tcx().def_span(did);
 785                         p!(write(
 786                             "@{}",
 787                             // This may end up in stderr diagnostics but it may also be emitted
 788                             // into MIR. Hence we use the remapped path if available
 789                             self.tcx().sess.source_map().span_to_embeddable_string(span)
 790                         ));
 791                     } else {
 792                         p!(write("@"), print_def_path(did, substs));
 793                     }
 794                 } else {
 795                     p!(print_def_path(did, substs));
 796                     p!(" upvar_tys=(");
 797                     if !substs.as_generator().is_valid() {
 798                         p!("unavailable");
 799                     } else {
 800                         self = self.comma_sep(substs.as_generator().upvar_tys())?;
 801                     }
 802                     p!(")");
 803
 804                     if substs.as_generator().is_valid() {
 805                         p!(" ", print(substs.as_generator().witness()));
 806                     }
 807                 }
 808
 809                 p!("]")
 810             }
 811             ty::GeneratorWitness(types) => {
 812                 p!(in_binder(&types));
 813             }
 814             ty::Closure(did, substs) => {
 815                 p!(write("["));
 816                 if !self.should_print_verbose() {
 817                     p!(write("closure"));
 818                     // FIXME(eddyb) should use `def_span`.
 819                     if let Some(did) = did.as_local() {
 820                         if self.tcx().sess.opts.unstable_opts.span_free_formats {
 821                             p!("@", print_def_path(did.to_def_id(), substs));
 822                         } else {
 823                             let span = self.tcx().def_span(did);
 824                             let preference = if FORCE_TRIMMED_PATH.with(|flag| flag.get()) {
 825                                 FileNameDisplayPreference::Short
 826                             } else {
 827                                 FileNameDisplayPreference::Remapped
 828                             };
 829                             p!(write(
 830                                 "@{}",
 831                                 // This may end up in stderr diagnostics but it may also be emitted
 832                                 // into MIR. Hence we use the remapped path if available
 833                                 self.tcx().sess.source_map().span_to_string(span, preference)
 834                             ));
 835                         }
 836                     } else {
 837                         p!(write("@"), print_def_path(did, substs));
 838                     }
 839                 } else {
 840                     p!(print_def_path(did, substs));
 841                     if !substs.as_closure().is_valid() {
 842                         p!(" closure_substs=(unavailable)");
 843                         p!(write(" substs={:?}", substs));
 844                     } else {
 845                         p!(" closure_kind_ty=", print(substs.as_closure().kind_ty()));
 846                         p!(
 847                             " closure_sig_as_fn_ptr_ty=",
 848                             print(substs.as_closure().sig_as_fn_ptr_ty())
 849                         );
 850                         p!(" upvar_tys=(");
 851                         self = self.comma_sep(substs.as_closure().upvar_tys())?;
 852                         p!(")");
 853                     }
 854                 }
 855                 p!("]");
 856             }
 857             ty::Array(ty, sz) => {
 858                 p!("[", print(ty), "; ");
 859                 if self.should_print_verbose() {
 860                     p!(write("{:?}", sz));
 861                 } else if let ty::ConstKind::Unevaluated(..) = sz.kind() {
 862                     // Do not try to evaluate unevaluated constants. If we are const evaluating an
 863                     // array length anon const, rustc will (with debug assertions) print the
 864                     // constant's path. Which will end up here again.
 865                     p!("_");
 866                 } else if let Some(n) = sz.kind().try_to_bits(self.tcx().data_layout.pointer_size) {
 867                     p!(write("{}", n));
 868                 } else if let ty::ConstKind::Param(param) = sz.kind() {
 869                     p!(print(param));
 870                 } else {
 871                     p!("_");
 872                 }
 873                 p!("]")
 874             }
 875             ty::Slice(ty) => p!("[", print(ty), "]"),
 876         }
 877
 878         Ok(self)
 879     }
 880
 881     fn pretty_print_opaque_impl_type(
 882         mut self,
 883         def_id: DefId,
 884         substs: &'tcx ty::List<ty::GenericArg<'tcx>>,
 885     ) -> Result<Self::Type, Self::Error> {
 886         let tcx = self.tcx();
 887
 888         // Grab the "TraitA + TraitB" from `impl TraitA + TraitB`,
 889         // by looking up the projections associated with the def_id.
 890         let bounds = tcx.bound_explicit_item_bounds(def_id);
 891
 892         let mut traits = FxIndexMap::default();
 893         let mut fn_traits = FxIndexMap::default();
 894         let mut is_sized = false;
 895         let mut lifetimes = SmallVec::<[ty::Region<'tcx>; 1]>::new();
 896
 897         for (predicate, _) in bounds.subst_iter_copied(tcx, substs) {
 898             let bound_predicate = predicate.kind();
 899
 900             match bound_predicate.skip_binder() {
 901                 ty::PredicateKind::Clause(ty::Clause::Trait(pred)) => {
 902                     let trait_ref = bound_predicate.rebind(pred.trait_ref);
 903
 904                     // Don't print + Sized, but rather + ?Sized if absent.
 905                     if Some(trait_ref.def_id()) == tcx.lang_items().sized_trait() {
 906                         is_sized = true;
 907                         continue;
 908                     }
 909
 910                     self.insert_trait_and_projection(trait_ref, None, &mut traits, &mut fn_traits);
 911                 }
 912                 ty::PredicateKind::Clause(ty::Clause::Projection(pred)) => {
 913                     let proj_ref = bound_predicate.rebind(pred);
 914                     let trait_ref = proj_ref.required_poly_trait_ref(tcx);
 915
 916                     // Projection type entry -- the def-id for naming, and the ty.
 917                     let proj_ty = (proj_ref.projection_def_id(), proj_ref.term());
 918
 919                     self.insert_trait_and_projection(
 920                         trait_ref,
 921                         Some(proj_ty),
 922                         &mut traits,
 923                         &mut fn_traits,
 924                     );
 925                 }
 926                 ty::PredicateKind::Clause(ty::Clause::TypeOutlives(outlives)) => {
 927                     lifetimes.push(outlives.1);
 928                 }
 929                 _ => {}
 930             }
 931         }
 932
 933         write!(self, "impl ")?;
 934
 935         let mut first = true;
 936         // Insert parenthesis around (Fn(A, B) -> C) if the opaque ty has more than one other trait
 937         let paren_needed = fn_traits.len() > 1 || traits.len() > 0 || !is_sized;
 938
 939         for (fn_once_trait_ref, entry) in fn_traits {
 940             write!(self, "{}", if first { "" } else { " + " })?;
 941             write!(self, "{}", if paren_needed { "(" } else { "" })?;
 942
 943             self = self.wrap_binder(&fn_once_trait_ref, |trait_ref, mut cx| {
 944                 define_scoped_cx!(cx);
 945                 // Get the (single) generic ty (the args) of this FnOnce trait ref.
 946                 let generics = tcx.generics_of(trait_ref.def_id);
 947                 let args = generics.own_substs_no_defaults(tcx, trait_ref.substs);
 948
 949                 match (entry.return_ty, args[0].expect_ty()) {
 950                     // We can only print `impl Fn() -> ()` if we have a tuple of args and we recorded
 951                     // a return type.
 952                     (Some(return_ty), arg_tys) if matches!(arg_tys.kind(), ty::Tuple(_)) => {
 953                         let name = if entry.fn_trait_ref.is_some() {
 954                             "Fn"
 955                         } else if entry.fn_mut_trait_ref.is_some() {
 956                             "FnMut"
 957                         } else {
 958                             "FnOnce"
 959                         };
 960
 961                         p!(write("{}(", name));
 962
 963                         for (idx, ty) in arg_tys.tuple_fields().iter().enumerate() {
 964                             if idx > 0 {
 965                                 p!(", ");
 966                             }
 967                             p!(print(ty));
 968                         }
 969
 970                         p!(")");
 971                         if let Some(ty) = return_ty.skip_binder().ty() {
 972                             if !ty.is_unit() {
 973                                 p!(" -> ", print(return_ty));
 974                             }
 975                         }
 976                         p!(write("{}", if paren_needed { ")" } else { "" }));
 977
 978                         first = false;
 979                     }
 980                     // If we got here, we can't print as a `impl Fn(A, B) -> C`. Just record the
 981                     // trait_refs we collected in the OpaqueFnEntry as normal trait refs.
 982                     _ => {
 983                         if entry.has_fn_once {
 984                             traits.entry(fn_once_trait_ref).or_default().extend(
 985                                 // Group the return ty with its def id, if we had one.
 986                                 entry
 987                                     .return_ty
 988                                     .map(|ty| (tcx.require_lang_item(LangItem::FnOnce, None), ty)),
 989                             );
 990                         }
 991                         if let Some(trait_ref) = entry.fn_mut_trait_ref {
 992                             traits.entry(trait_ref).or_default();
 993                         }
 994                         if let Some(trait_ref) = entry.fn_trait_ref {
 995                             traits.entry(trait_ref).or_default();
 996                         }
 997                     }
 998                 }
 999
1000                 Ok(cx)
1001             })?;
1002         }
1003
1004         // Print the rest of the trait types (that aren't Fn* family of traits)
1005         for (trait_ref, assoc_items) in traits {
1006             write!(self, "{}", if first { "" } else { " + " })?;
1007
1008             self = self.wrap_binder(&trait_ref, |trait_ref, mut cx| {
1009                 define_scoped_cx!(cx);
1010                 p!(print(trait_ref.print_only_trait_name()));
1011
1012                 let generics = tcx.generics_of(trait_ref.def_id);
1013                 let args = generics.own_substs_no_defaults(tcx, trait_ref.substs);
1014
1015                 if !args.is_empty() || !assoc_items.is_empty() {
1016                     let mut first = true;
1017
1018                     for ty in args {
1019                         if first {
1020                             p!("<");
1021                             first = false;
1022                         } else {
1023                             p!(", ");
1024                         }
1025                         p!(print(ty));
1026                     }
1027
1028                     for (assoc_item_def_id, term) in assoc_items {
1029                         // Skip printing `<[generator@] as Generator<_>>::Return` from async blocks,
1030                         // unless we can find out what generator return type it comes from.
1031                         let term = if let Some(ty) = term.skip_binder().ty()
1032                             && let ty::Alias(ty::Projection, proj) = ty.kind()
1033                             && let Some(assoc) = tcx.opt_associated_item(proj.def_id)
1034                             && assoc.trait_container(tcx) == tcx.lang_items().gen_trait()
1035                             && assoc.name == rustc_span::sym::Return
1036                         {
1037                             if let ty::Generator(_, substs, _) = substs.type_at(0).kind() {
1038                                 let return_ty = substs.as_generator().return_ty();
1039                                 if !return_ty.is_ty_var() {
1040                                     return_ty.into()
1041                                 } else {
1042                                     continue;
1043                                 }
1044                             } else {
1045                                 continue;
1046                             }
1047                         } else {
1048                             term.skip_binder()
1049                         };
1050
1051                         if first {
1052                             p!("<");
1053                             first = false;
1054                         } else {
1055                             p!(", ");
1056                         }
1057
1058                         p!(write("{} = ", tcx.associated_item(assoc_item_def_id).name));
1059
1060                         match term.unpack() {
1061                             TermKind::Ty(ty) => p!(print(ty)),
1062                             TermKind::Const(c) => p!(print(c)),
1063                         };
1064                     }
1065
1066                     if !first {
1067                         p!(">");
1068                     }
1069                 }
1070
1071                 first = false;
1072                 Ok(cx)
1073             })?;
1074         }
1075
1076         if !is_sized {
1077             write!(self, "{}?Sized", if first { "" } else { " + " })?;
1078         } else if first {
1079             write!(self, "Sized")?;
1080         }
1081
1082         for re in lifetimes {
1083             write!(self, " + ")?;
1084             self = self.print_region(re)?;
1085         }
1086
1087         Ok(self)
1088     }
1089
1090     /// Insert the trait ref and optionally a projection type associated with it into either the
1091     /// traits map or fn_traits map, depending on if the trait is in the Fn* family of traits.
1092     fn insert_trait_and_projection(
1093         &mut self,
1094         trait_ref: ty::PolyTraitRef<'tcx>,
1095         proj_ty: Option<(DefId, ty::Binder<'tcx, Term<'tcx>>)>,
1096         traits: &mut FxIndexMap<
1097             ty::PolyTraitRef<'tcx>,
1098             FxIndexMap<DefId, ty::Binder<'tcx, Term<'tcx>>>,
1099         >,
1100         fn_traits: &mut FxIndexMap<ty::PolyTraitRef<'tcx>, OpaqueFnEntry<'tcx>>,
1101     ) {
1102         let trait_def_id = trait_ref.def_id();
1103
1104         // If our trait_ref is FnOnce or any of its children, project it onto the parent FnOnce
1105         // super-trait ref and record it there.
1106         if let Some(fn_once_trait) = self.tcx().lang_items().fn_once_trait() {
1107             // If we have a FnOnce, then insert it into
1108             if trait_def_id == fn_once_trait {
1109                 let entry = fn_traits.entry(trait_ref).or_default();
1110                 // Optionally insert the return_ty as well.
1111                 if let Some((_, ty)) = proj_ty {
1112                     entry.return_ty = Some(ty);
1113                 }
1114                 entry.has_fn_once = true;
1115                 return;
1116             } else if Some(trait_def_id) == self.tcx().lang_items().fn_mut_trait() {
1117                 let super_trait_ref = crate::traits::util::supertraits(self.tcx(), trait_ref)
1118                     .find(|super_trait_ref| super_trait_ref.def_id() == fn_once_trait)
1119                     .unwrap();
1120
1121                 fn_traits.entry(super_trait_ref).or_default().fn_mut_trait_ref = Some(trait_ref);
1122                 return;
1123             } else if Some(trait_def_id) == self.tcx().lang_items().fn_trait() {
1124                 let super_trait_ref = crate::traits::util::supertraits(self.tcx(), trait_ref)
1125                     .find(|super_trait_ref| super_trait_ref.def_id() == fn_once_trait)
1126                     .unwrap();
1127
1128                 fn_traits.entry(super_trait_ref).or_default().fn_trait_ref = Some(trait_ref);
1129                 return;
1130             }
1131         }
1132
1133         // Otherwise, just group our traits and projection types.
1134         traits.entry(trait_ref).or_default().extend(proj_ty);
1135     }
1136
1137     fn pretty_print_bound_var(
1138         &mut self,
1139         debruijn: ty::DebruijnIndex,
1140         var: ty::BoundVar,
1141     ) -> Result<(), Self::Error> {
1142         if debruijn == ty::INNERMOST {
1143             write!(self, "^{}", var.index())
1144         } else {
1145             write!(self, "^{}_{}", debruijn.index(), var.index())
1146         }
1147     }
1148
1149     fn ty_infer_name(&self, _: ty::TyVid) -> Option<Symbol> {
1150         None
1151     }
1152
1153     fn const_infer_name(&self, _: ty::ConstVid<'tcx>) -> Option<Symbol> {
1154         None
1155     }
1156
1157     fn pretty_print_dyn_existential(
1158         mut self,
1159         predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
1160     ) -> Result<Self::DynExistential, Self::Error> {
1161         // Generate the main trait ref, including associated types.
1162         let mut first = true;
1163
1164         if let Some(principal) = predicates.principal() {
1165             self = self.wrap_binder(&principal, |principal, mut cx| {
1166                 define_scoped_cx!(cx);
1167                 p!(print_def_path(principal.def_id, &[]));
1168
1169                 let mut resugared = false;
1170
1171                 // Special-case `Fn(...) -> ...` and re-sugar it.
1172                 let fn_trait_kind = cx.tcx().fn_trait_kind_from_def_id(principal.def_id);
1173                 if !cx.should_print_verbose() && fn_trait_kind.is_some() {
1174                     if let ty::Tuple(tys) = principal.substs.type_at(0).kind() {
1175                         let mut projections = predicates.projection_bounds();
1176                         if let (Some(proj), None) = (projections.next(), projections.next()) {
1177                             p!(pretty_fn_sig(
1178                                 tys,
1179                                 false,
1180                                 proj.skip_binder().term.ty().expect("Return type was a const")
1181                             ));
1182                             resugared = true;
1183                         }
1184                     }
1185                 }
1186
1187                 // HACK(eddyb) this duplicates `FmtPrinter`'s `path_generic_args`,
1188                 // in order to place the projections inside the `<...>`.
1189                 if !resugared {
1190                     // Use a type that can't appear in defaults of type parameters.
1191                     let dummy_cx = cx.tcx().mk_ty_infer(ty::FreshTy(0));
1192                     let principal = principal.with_self_ty(cx.tcx(), dummy_cx);
1193
1194                     let args = cx
1195                         .tcx()
1196                         .generics_of(principal.def_id)
1197                         .own_substs_no_defaults(cx.tcx(), principal.substs);
1198
1199                     let mut projections = predicates.projection_bounds();
1200
1201                     let mut args = args.iter().cloned();
1202                     let arg0 = args.next();
1203                     let projection0 = projections.next();
1204                     if arg0.is_some() || projection0.is_some() {
1205                         let args = arg0.into_iter().chain(args);
1206                         let projections = projection0.into_iter().chain(projections);
1207
1208                         p!(generic_delimiters(|mut cx| {
1209                             cx = cx.comma_sep(args)?;
1210                             if arg0.is_some() && projection0.is_some() {
1211                                 write!(cx, ", ")?;
1212                             }
1213                             cx.comma_sep(projections)
1214                         }));
1215                     }
1216                 }
1217                 Ok(cx)
1218             })?;
1219
1220             first = false;
1221         }
1222
1223         define_scoped_cx!(self);
1224
1225         // Builtin bounds.
1226         // FIXME(eddyb) avoid printing twice (needed to ensure
1227         // that the auto traits are sorted *and* printed via cx).
1228         let mut auto_traits: Vec<_> = predicates.auto_traits().collect();
1229
1230         // The auto traits come ordered by `DefPathHash`. While
1231         // `DefPathHash` is *stable* in the sense that it depends on
1232         // neither the host nor the phase of the moon, it depends
1233         // "pseudorandomly" on the compiler version and the target.
1234         //
1235         // To avoid causing instabilities in compiletest
1236         // output, sort the auto-traits alphabetically.
1237         auto_traits.sort_by_cached_key(|did| with_no_trimmed_paths!(self.tcx().def_path_str(*did)));
1238
1239         for def_id in auto_traits {
1240             if !first {
1241                 p!(" + ");
1242             }
1243             first = false;
1244
1245             p!(print_def_path(def_id, &[]));
1246         }
1247
1248         Ok(self)
1249     }
1250
1251     fn pretty_fn_sig(
1252         mut self,
1253         inputs: &[Ty<'tcx>],
1254         c_variadic: bool,
1255         output: Ty<'tcx>,
1256     ) -> Result<Self, Self::Error> {
1257         define_scoped_cx!(self);
1258
1259         p!("(", comma_sep(inputs.iter().copied()));
1260         if c_variadic {
1261             if !inputs.is_empty() {
1262                 p!(", ");
1263             }
1264             p!("...");
1265         }
1266         p!(")");
1267         if !output.is_unit() {
1268             p!(" -> ", print(output));
1269         }
1270
1271         Ok(self)
1272     }
1273
1274     fn pretty_print_const(
1275         mut self,
1276         ct: ty::Const<'tcx>,
1277         print_ty: bool,
1278     ) -> Result<Self::Const, Self::Error> {
1279         define_scoped_cx!(self);
1280
1281         if self.should_print_verbose() {
1282             p!(write("Const({:?}: {:?})", ct.kind(), ct.ty()));
1283             return Ok(self);
1284         }
1285
1286         macro_rules! print_underscore {
1287             () => {{
1288                 if print_ty {
1289                     self = self.typed_value(
1290                         |mut this| {
1291                             write!(this, "_")?;
1292                             Ok(this)
1293                         },
1294                         |this| this.print_type(ct.ty()),
1295                         ": ",
1296                     )?;
1297                 } else {
1298                     write!(self, "_")?;
1299                 }
1300             }};
1301         }
1302
1303         match ct.kind() {
1304             ty::ConstKind::Unevaluated(ty::UnevaluatedConst { def, substs }) => {
1305                 match self.tcx().def_kind(def.did) {
1306                     DefKind::Static(..) | DefKind::Const | DefKind::AssocConst => {
1307                         p!(print_value_path(def.did, substs))
1308                     }
1309                     _ => {
1310                         if def.is_local() {
1311                             let span = self.tcx().def_span(def.did);
1312                             if let Ok(snip) = self.tcx().sess.source_map().span_to_snippet(span) {
1313                                 p!(write("{}", snip))
1314                             } else {
1315                                 print_underscore!()
1316                             }
1317                         } else {
1318                             print_underscore!()
1319                         }
1320                     }
1321                 }
1322             }
1323             ty::ConstKind::Infer(infer_ct) => {
1324                 match infer_ct {
1325                     ty::InferConst::Var(ct_vid)
1326                         if let Some(name) = self.const_infer_name(ct_vid) =>
1327                             p!(write("{}", name)),
1328                     _ => print_underscore!(),
1329                 }
1330             }
1331             ty::ConstKind::Param(ParamConst { name, .. }) => p!(write("{}", name)),
1332             ty::ConstKind::Value(value) => {
1333                 return self.pretty_print_const_valtree(value, ct.ty(), print_ty);
1334             }
1335
1336             ty::ConstKind::Bound(debruijn, bound_var) => {
1337                 self.pretty_print_bound_var(debruijn, bound_var)?
1338             }
1339             ty::ConstKind::Placeholder(placeholder) => p!(write("Placeholder({:?})", placeholder)),
1340             // FIXME(generic_const_exprs):
1341             // write out some legible representation of an abstract const?
1342             ty::ConstKind::Expr(_) => p!("[Const Expr]"),
1343             ty::ConstKind::Error(_) => p!("[const error]"),
1344         };
1345         Ok(self)
1346     }
1347
1348     fn pretty_print_const_scalar(
1349         self,
1350         scalar: Scalar,
1351         ty: Ty<'tcx>,
1352         print_ty: bool,
1353     ) -> Result<Self::Const, Self::Error> {
1354         match scalar {
1355             Scalar::Ptr(ptr, _size) => self.pretty_print_const_scalar_ptr(ptr, ty, print_ty),
1356             Scalar::Int(int) => self.pretty_print_const_scalar_int(int, ty, print_ty),
1357         }
1358     }
1359
1360     fn pretty_print_const_scalar_ptr(
1361         mut self,
1362         ptr: Pointer,
1363         ty: Ty<'tcx>,
1364         print_ty: bool,
1365     ) -> Result<Self::Const, Self::Error> {
1366         define_scoped_cx!(self);
1367
1368         let (alloc_id, offset) = ptr.into_parts();
1369         match ty.kind() {
1370             // Byte strings (&[u8; N])
1371             ty::Ref(_, inner, _) => {
1372                 if let ty::Array(elem, len) = inner.kind() {
1373                     if let ty::Uint(ty::UintTy::U8) = elem.kind() {
1374                         if let ty::ConstKind::Value(ty::ValTree::Leaf(int)) = len.kind() {
1375                             match self.tcx().try_get_global_alloc(alloc_id) {
1376                                 Some(GlobalAlloc::Memory(alloc)) => {
1377                                     let len = int.assert_bits(self.tcx().data_layout.pointer_size);
1378                                     let range =
1379                                         AllocRange { start: offset, size: Size::from_bytes(len) };
1380                                     if let Ok(byte_str) =
1381                                         alloc.inner().get_bytes_strip_provenance(&self.tcx(), range)
1382                                     {
1383                                         p!(pretty_print_byte_str(byte_str))
1384                                     } else {
1385                                         p!("<too short allocation>")
1386                                     }
1387                                 }
1388                                 // FIXME: for statics, vtables, and functions, we could in principle print more detail.
1389                                 Some(GlobalAlloc::Static(def_id)) => {
1390                                     p!(write("<static({:?})>", def_id))
1391                                 }
1392                                 Some(GlobalAlloc::Function(_)) => p!("<function>"),
1393                                 Some(GlobalAlloc::VTable(..)) => p!("<vtable>"),
1394                                 None => p!("<dangling pointer>"),
1395                             }
1396                             return Ok(self);
1397                         }
1398                     }
1399                 }
1400             }
1401             ty::FnPtr(_) => {
1402                 // FIXME: We should probably have a helper method to share code with the "Byte strings"
1403                 // printing above (which also has to handle pointers to all sorts of things).
1404                 if let Some(GlobalAlloc::Function(instance)) =
1405                     self.tcx().try_get_global_alloc(alloc_id)
1406                 {
1407                     self = self.typed_value(
1408                         |this| this.print_value_path(instance.def_id(), instance.substs),
1409                         |this| this.print_type(ty),
1410                         " as ",
1411                     )?;
1412                     return Ok(self);
1413                 }
1414             }
1415             _ => {}
1416         }
1417         // Any pointer values not covered by a branch above
1418         self = self.pretty_print_const_pointer(ptr, ty, print_ty)?;
1419         Ok(self)
1420     }
1421
1422     fn pretty_print_const_scalar_int(
1423         mut self,
1424         int: ScalarInt,
1425         ty: Ty<'tcx>,
1426         print_ty: bool,
1427     ) -> Result<Self::Const, Self::Error> {
1428         define_scoped_cx!(self);
1429
1430         match ty.kind() {
1431             // Bool
1432             ty::Bool if int == ScalarInt::FALSE => p!("false"),
1433             ty::Bool if int == ScalarInt::TRUE => p!("true"),
1434             // Float
1435             ty::Float(ty::FloatTy::F32) => {
1436                 p!(write("{}f32", Single::try_from(int).unwrap()))
1437             }
1438             ty::Float(ty::FloatTy::F64) => {
1439                 p!(write("{}f64", Double::try_from(int).unwrap()))
1440             }
1441             // Int
1442             ty::Uint(_) | ty::Int(_) => {
1443                 let int =
1444                     ConstInt::new(int, matches!(ty.kind(), ty::Int(_)), ty.is_ptr_sized_integral());
1445                 if print_ty { p!(write("{:#?}", int)) } else { p!(write("{:?}", int)) }
1446             }
1447             // Char
1448             ty::Char if char::try_from(int).is_ok() => {
1449                 p!(write("{:?}", char::try_from(int).unwrap()))
1450             }
1451             // Pointer types
1452             ty::Ref(..) | ty::RawPtr(_) | ty::FnPtr(_) => {
1453                 let data = int.assert_bits(self.tcx().data_layout.pointer_size);
1454                 self = self.typed_value(
1455                     |mut this| {
1456                         write!(this, "0x{:x}", data)?;
1457                         Ok(this)
1458                     },
1459                     |this| this.print_type(ty),
1460                     " as ",
1461                 )?;
1462             }
1463             // Nontrivial types with scalar bit representation
1464             _ => {
1465                 let print = |mut this: Self| {
1466                     if int.size() == Size::ZERO {
1467                         write!(this, "transmute(())")?;
1468                     } else {
1469                         write!(this, "transmute(0x{:x})", int)?;
1470                     }
1471                     Ok(this)
1472                 };
1473                 self = if print_ty {
1474                     self.typed_value(print, |this| this.print_type(ty), ": ")?
1475                 } else {
1476                     print(self)?
1477                 };
1478             }
1479         }
1480         Ok(self)
1481     }
1482
1483     /// This is overridden for MIR printing because we only want to hide alloc ids from users, not
1484     /// from MIR where it is actually useful.
1485     fn pretty_print_const_pointer<Prov: Provenance>(
1486         mut self,
1487         _: Pointer<Prov>,
1488         ty: Ty<'tcx>,
1489         print_ty: bool,
1490     ) -> Result<Self::Const, Self::Error> {
1491         if print_ty {
1492             self.typed_value(
1493                 |mut this| {
1494                     this.write_str("&_")?;
1495                     Ok(this)
1496                 },
1497                 |this| this.print_type(ty),
1498                 ": ",
1499             )
1500         } else {
1501             self.write_str("&_")?;
1502             Ok(self)
1503         }
1504     }
1505
1506     fn pretty_print_byte_str(mut self, byte_str: &'tcx [u8]) -> Result<Self::Const, Self::Error> {
1507         write!(self, "b\"{}\"", byte_str.escape_ascii())?;
1508         Ok(self)
1509     }
1510
1511     fn pretty_print_const_valtree(
1512         mut self,
1513         valtree: ty::ValTree<'tcx>,
1514         ty: Ty<'tcx>,
1515         print_ty: bool,
1516     ) -> Result<Self::Const, Self::Error> {
1517         define_scoped_cx!(self);
1518
1519         if self.should_print_verbose() {
1520             p!(write("ValTree({:?}: ", valtree), print(ty), ")");
1521             return Ok(self);
1522         }
1523
1524         let u8_type = self.tcx().types.u8;
1525         match (valtree, ty.kind()) {
1526             (ty::ValTree::Branch(_), ty::Ref(_, inner_ty, _)) => match inner_ty.kind() {
1527                 ty::Slice(t) if *t == u8_type => {
1528                     let bytes = valtree.try_to_raw_bytes(self.tcx(), ty).unwrap_or_else(|| {
1529                         bug!(
1530                             "expected to convert valtree {:?} to raw bytes for type {:?}",
1531                             valtree,
1532                             t
1533                         )
1534                     });
1535                     return self.pretty_print_byte_str(bytes);
1536                 }
1537                 ty::Str => {
1538                     let bytes = valtree.try_to_raw_bytes(self.tcx(), ty).unwrap_or_else(|| {
1539                         bug!("expected to convert valtree to raw bytes for type {:?}", ty)
1540                     });
1541                     p!(write("{:?}", String::from_utf8_lossy(bytes)));
1542                     return Ok(self);
1543                 }
1544                 _ => {
1545                     p!("&");
1546                     p!(pretty_print_const_valtree(valtree, *inner_ty, print_ty));
1547                     return Ok(self);
1548                 }
1549             },
1550             (ty::ValTree::Branch(_), ty::Array(t, _)) if *t == u8_type => {
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 {:?}", t)
1553                 });
1554                 p!("*");
1555                 p!(pretty_print_byte_str(bytes));
1556                 return Ok(self);
1557             }
1558             // Aggregates, printed as array/tuple/struct/variant construction syntax.
1559             (ty::ValTree::Branch(_), ty::Array(..) | ty::Tuple(..) | ty::Adt(..)) => {
1560                 let contents = self.tcx().destructure_const(self.tcx().mk_const(valtree, ty));
1561                 let fields = contents.fields.iter().copied();
1562                 match *ty.kind() {
1563                     ty::Array(..) => {
1564                         p!("[", comma_sep(fields), "]");
1565                     }
1566                     ty::Tuple(..) => {
1567                         p!("(", comma_sep(fields));
1568                         if contents.fields.len() == 1 {
1569                             p!(",");
1570                         }
1571                         p!(")");
1572                     }
1573                     ty::Adt(def, _) if def.variants().is_empty() => {
1574                         self = self.typed_value(
1575                             |mut this| {
1576                                 write!(this, "unreachable()")?;
1577                                 Ok(this)
1578                             },
1579                             |this| this.print_type(ty),
1580                             ": ",
1581                         )?;
1582                     }
1583                     ty::Adt(def, substs) => {
1584                         let variant_idx =
1585                             contents.variant.expect("destructed const of adt without variant idx");
1586                         let variant_def = &def.variant(variant_idx);
1587                         p!(print_value_path(variant_def.def_id, substs));
1588                         match variant_def.ctor_kind() {
1589                             Some(CtorKind::Const) => {}
1590                             Some(CtorKind::Fn) => {
1591                                 p!("(", comma_sep(fields), ")");
1592                             }
1593                             None => {
1594                                 p!(" {{ ");
1595                                 let mut first = true;
1596                                 for (field_def, field) in iter::zip(&variant_def.fields, fields) {
1597                                     if !first {
1598                                         p!(", ");
1599                                     }
1600                                     p!(write("{}: ", field_def.name), print(field));
1601                                     first = false;
1602                                 }
1603                                 p!(" }}");
1604                             }
1605                         }
1606                     }
1607                     _ => unreachable!(),
1608                 }
1609                 return Ok(self);
1610             }
1611             (ty::ValTree::Leaf(leaf), ty::Ref(_, inner_ty, _)) => {
1612                 p!(write("&"));
1613                 return self.pretty_print_const_scalar_int(leaf, *inner_ty, print_ty);
1614             }
1615             (ty::ValTree::Leaf(leaf), _) => {
1616                 return self.pretty_print_const_scalar_int(leaf, ty, print_ty);
1617             }
1618             // FIXME(oli-obk): also pretty print arrays and other aggregate constants by reading
1619             // their fields instead of just dumping the memory.
1620             _ => {}
1621         }
1622
1623         // fallback
1624         if valtree == ty::ValTree::zst() {
1625             p!(write("<ZST>"));
1626         } else {
1627             p!(write("{:?}", valtree));
1628         }
1629         if print_ty {
1630             p!(": ", print(ty));
1631         }
1632         Ok(self)
1633     }
1634
1635     fn pretty_closure_as_impl(
1636         mut self,
1637         closure: ty::ClosureSubsts<'tcx>,
1638     ) -> Result<Self::Const, Self::Error> {
1639         let sig = closure.sig();
1640         let kind = closure.kind_ty().to_opt_closure_kind().unwrap_or(ty::ClosureKind::Fn);
1641
1642         write!(self, "impl ")?;
1643         self.wrap_binder(&sig, |sig, mut cx| {
1644             define_scoped_cx!(cx);
1645
1646             p!(print(kind), "(");
1647             for (i, arg) in sig.inputs()[0].tuple_fields().iter().enumerate() {
1648                 if i > 0 {
1649                     p!(", ");
1650                 }
1651                 p!(print(arg));
1652             }
1653             p!(")");
1654
1655             if !sig.output().is_unit() {
1656                 p!(" -> ", print(sig.output()));
1657             }
1658
1659             Ok(cx)
1660         })
1661     }
1662
1663     fn should_print_verbose(&self) -> bool {
1664         self.tcx().sess.verbose()
1665     }
1666 }
1667
1668 // HACK(eddyb) boxed to avoid moving around a large struct by-value.
1669 pub struct FmtPrinter<'a, 'tcx>(Box<FmtPrinterData<'a, 'tcx>>);
1670
1671 pub struct FmtPrinterData<'a, 'tcx> {
1672     tcx: TyCtxt<'tcx>,
1673     fmt: String,
1674
1675     empty_path: bool,
1676     in_value: bool,
1677     pub print_alloc_ids: bool,
1678
1679     // set of all named (non-anonymous) region names
1680     used_region_names: FxHashSet<Symbol>,
1681
1682     region_index: usize,
1683     binder_depth: usize,
1684     printed_type_count: usize,
1685     type_length_limit: Limit,
1686     truncated: bool,
1687
1688     pub region_highlight_mode: RegionHighlightMode<'tcx>,
1689
1690     pub ty_infer_name_resolver: Option<Box<dyn Fn(ty::TyVid) -> Option<Symbol> + 'a>>,
1691     pub const_infer_name_resolver: Option<Box<dyn Fn(ty::ConstVid<'tcx>) -> Option<Symbol> + 'a>>,
1692 }
1693
1694 impl<'a, 'tcx> Deref for FmtPrinter<'a, 'tcx> {
1695     type Target = FmtPrinterData<'a, 'tcx>;
1696     fn deref(&self) -> &Self::Target {
1697         &self.0
1698     }
1699 }
1700
1701 impl DerefMut for FmtPrinter<'_, '_> {
1702     fn deref_mut(&mut self) -> &mut Self::Target {
1703         &mut self.0
1704     }
1705 }
1706
1707 impl<'a, 'tcx> FmtPrinter<'a, 'tcx> {
1708     pub fn new(tcx: TyCtxt<'tcx>, ns: Namespace) -> Self {
1709         Self::new_with_limit(tcx, ns, tcx.type_length_limit())
1710     }
1711
1712     pub fn new_with_limit(tcx: TyCtxt<'tcx>, ns: Namespace, type_length_limit: Limit) -> Self {
1713         FmtPrinter(Box::new(FmtPrinterData {
1714             tcx,
1715             // Estimated reasonable capacity to allocate upfront based on a few
1716             // benchmarks.
1717             fmt: String::with_capacity(64),
1718             empty_path: false,
1719             in_value: ns == Namespace::ValueNS,
1720             print_alloc_ids: false,
1721             used_region_names: Default::default(),
1722             region_index: 0,
1723             binder_depth: 0,
1724             printed_type_count: 0,
1725             type_length_limit,
1726             truncated: false,
1727             region_highlight_mode: RegionHighlightMode::new(tcx),
1728             ty_infer_name_resolver: None,
1729             const_infer_name_resolver: None,
1730         }))
1731     }
1732
1733     pub fn into_buffer(self) -> String {
1734         self.0.fmt
1735     }
1736 }
1737
1738 // HACK(eddyb) get rid of `def_path_str` and/or pass `Namespace` explicitly always
1739 // (but also some things just print a `DefId` generally so maybe we need this?)
1740 fn guess_def_namespace(tcx: TyCtxt<'_>, def_id: DefId) -> Namespace {
1741     match tcx.def_key(def_id).disambiguated_data.data {
1742         DefPathData::TypeNs(..) | DefPathData::CrateRoot | DefPathData::ImplTrait => {
1743             Namespace::TypeNS
1744         }
1745
1746         DefPathData::ValueNs(..)
1747         | DefPathData::AnonConst
1748         | DefPathData::ClosureExpr
1749         | DefPathData::Ctor => Namespace::ValueNS,
1750
1751         DefPathData::MacroNs(..) => Namespace::MacroNS,
1752
1753         _ => Namespace::TypeNS,
1754     }
1755 }
1756
1757 impl<'t> TyCtxt<'t> {
1758     /// Returns a string identifying this `DefId`. This string is
1759     /// suitable for user output.
1760     pub fn def_path_str(self, def_id: DefId) -> String {
1761         self.def_path_str_with_substs(def_id, &[])
1762     }
1763
1764     pub fn def_path_str_with_substs(self, def_id: DefId, substs: &'t [GenericArg<'t>]) -> String {
1765         let ns = guess_def_namespace(self, def_id);
1766         debug!("def_path_str: def_id={:?}, ns={:?}", def_id, ns);
1767         FmtPrinter::new(self, ns).print_def_path(def_id, substs).unwrap().into_buffer()
1768     }
1769
1770     pub fn value_path_str_with_substs(self, def_id: DefId, substs: &'t [GenericArg<'t>]) -> String {
1771         let ns = guess_def_namespace(self, def_id);
1772         debug!("value_path_str: def_id={:?}, ns={:?}", def_id, ns);
1773         FmtPrinter::new(self, ns).print_value_path(def_id, substs).unwrap().into_buffer()
1774     }
1775 }
1776
1777 impl fmt::Write for FmtPrinter<'_, '_> {
1778     fn write_str(&mut self, s: &str) -> fmt::Result {
1779         self.fmt.push_str(s);
1780         Ok(())
1781     }
1782 }
1783
1784 impl<'tcx> Printer<'tcx> for FmtPrinter<'_, 'tcx> {
1785     type Error = fmt::Error;
1786
1787     type Path = Self;
1788     type Region = Self;
1789     type Type = Self;
1790     type DynExistential = Self;
1791     type Const = Self;
1792
1793     fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
1794         self.tcx
1795     }
1796
1797     fn print_def_path(
1798         mut self,
1799         def_id: DefId,
1800         substs: &'tcx [GenericArg<'tcx>],
1801     ) -> Result<Self::Path, Self::Error> {
1802         define_scoped_cx!(self);
1803
1804         if substs.is_empty() {
1805             match self.try_print_trimmed_def_path(def_id)? {
1806                 (cx, true) => return Ok(cx),
1807                 (cx, false) => self = cx,
1808             }
1809
1810             match self.try_print_visible_def_path(def_id)? {
1811                 (cx, true) => return Ok(cx),
1812                 (cx, false) => self = cx,
1813             }
1814         }
1815
1816         let key = self.tcx.def_key(def_id);
1817         if let DefPathData::Impl = key.disambiguated_data.data {
1818             // Always use types for non-local impls, where types are always
1819             // available, and filename/line-number is mostly uninteresting.
1820             let use_types = !def_id.is_local() || {
1821                 // Otherwise, use filename/line-number if forced.
1822                 let force_no_types = FORCE_IMPL_FILENAME_LINE.with(|f| f.get());
1823                 !force_no_types
1824             };
1825
1826             if !use_types {
1827                 // If no type info is available, fall back to
1828                 // pretty printing some span information. This should
1829                 // only occur very early in the compiler pipeline.
1830                 let parent_def_id = DefId { index: key.parent.unwrap(), ..def_id };
1831                 let span = self.tcx.def_span(def_id);
1832
1833                 self = self.print_def_path(parent_def_id, &[])?;
1834
1835                 // HACK(eddyb) copy of `path_append` to avoid
1836                 // constructing a `DisambiguatedDefPathData`.
1837                 if !self.empty_path {
1838                     write!(self, "::")?;
1839                 }
1840                 write!(
1841                     self,
1842                     "<impl at {}>",
1843                     // This may end up in stderr diagnostics but it may also be emitted
1844                     // into MIR. Hence we use the remapped path if available
1845                     self.tcx.sess.source_map().span_to_embeddable_string(span)
1846                 )?;
1847                 self.empty_path = false;
1848
1849                 return Ok(self);
1850             }
1851         }
1852
1853         self.default_print_def_path(def_id, substs)
1854     }
1855
1856     fn print_region(self, region: ty::Region<'tcx>) -> Result<Self::Region, Self::Error> {
1857         self.pretty_print_region(region)
1858     }
1859
1860     fn print_type(mut self, ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
1861         if self.type_length_limit.value_within_limit(self.printed_type_count) {
1862             self.printed_type_count += 1;
1863             self.pretty_print_type(ty)
1864         } else {
1865             self.truncated = true;
1866             write!(self, "...")?;
1867             Ok(self)
1868         }
1869     }
1870
1871     fn print_dyn_existential(
1872         self,
1873         predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
1874     ) -> Result<Self::DynExistential, Self::Error> {
1875         self.pretty_print_dyn_existential(predicates)
1876     }
1877
1878     fn print_const(self, ct: ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
1879         self.pretty_print_const(ct, false)
1880     }
1881
1882     fn path_crate(mut self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
1883         self.empty_path = true;
1884         if cnum == LOCAL_CRATE {
1885             if self.tcx.sess.rust_2018() {
1886                 // We add the `crate::` keyword on Rust 2018, only when desired.
1887                 if SHOULD_PREFIX_WITH_CRATE.with(|flag| flag.get()) {
1888                     write!(self, "{}", kw::Crate)?;
1889                     self.empty_path = false;
1890                 }
1891             }
1892         } else {
1893             write!(self, "{}", self.tcx.crate_name(cnum))?;
1894             self.empty_path = false;
1895         }
1896         Ok(self)
1897     }
1898
1899     fn path_qualified(
1900         mut self,
1901         self_ty: Ty<'tcx>,
1902         trait_ref: Option<ty::TraitRef<'tcx>>,
1903     ) -> Result<Self::Path, Self::Error> {
1904         self = self.pretty_path_qualified(self_ty, trait_ref)?;
1905         self.empty_path = false;
1906         Ok(self)
1907     }
1908
1909     fn path_append_impl(
1910         mut self,
1911         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1912         _disambiguated_data: &DisambiguatedDefPathData,
1913         self_ty: Ty<'tcx>,
1914         trait_ref: Option<ty::TraitRef<'tcx>>,
1915     ) -> Result<Self::Path, Self::Error> {
1916         self = self.pretty_path_append_impl(
1917             |mut cx| {
1918                 cx = print_prefix(cx)?;
1919                 if !cx.empty_path {
1920                     write!(cx, "::")?;
1921                 }
1922
1923                 Ok(cx)
1924             },
1925             self_ty,
1926             trait_ref,
1927         )?;
1928         self.empty_path = false;
1929         Ok(self)
1930     }
1931
1932     fn path_append(
1933         mut self,
1934         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1935         disambiguated_data: &DisambiguatedDefPathData,
1936     ) -> Result<Self::Path, Self::Error> {
1937         self = print_prefix(self)?;
1938
1939         // Skip `::{{extern}}` blocks and `::{{constructor}}` on tuple/unit structs.
1940         if let DefPathData::ForeignMod | DefPathData::Ctor = disambiguated_data.data {
1941             return Ok(self);
1942         }
1943
1944         let name = disambiguated_data.data.name();
1945         if !self.empty_path {
1946             write!(self, "::")?;
1947         }
1948
1949         if let DefPathDataName::Named(name) = name {
1950             if Ident::with_dummy_span(name).is_raw_guess() {
1951                 write!(self, "r#")?;
1952             }
1953         }
1954
1955         let verbose = self.should_print_verbose();
1956         disambiguated_data.fmt_maybe_verbose(&mut self, verbose)?;
1957
1958         self.empty_path = false;
1959
1960         Ok(self)
1961     }
1962
1963     fn path_generic_args(
1964         mut self,
1965         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1966         args: &[GenericArg<'tcx>],
1967     ) -> Result<Self::Path, Self::Error> {
1968         self = print_prefix(self)?;
1969
1970         if args.first().is_some() {
1971             if self.in_value {
1972                 write!(self, "::")?;
1973             }
1974             self.generic_delimiters(|cx| cx.comma_sep(args.iter().cloned()))
1975         } else {
1976             Ok(self)
1977         }
1978     }
1979 }
1980
1981 impl<'tcx> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx> {
1982     fn ty_infer_name(&self, id: ty::TyVid) -> Option<Symbol> {
1983         self.0.ty_infer_name_resolver.as_ref().and_then(|func| func(id))
1984     }
1985
1986     fn reset_type_limit(&mut self) {
1987         self.printed_type_count = 0;
1988     }
1989
1990     fn const_infer_name(&self, id: ty::ConstVid<'tcx>) -> Option<Symbol> {
1991         self.0.const_infer_name_resolver.as_ref().and_then(|func| func(id))
1992     }
1993
1994     fn print_value_path(
1995         mut self,
1996         def_id: DefId,
1997         substs: &'tcx [GenericArg<'tcx>],
1998     ) -> Result<Self::Path, Self::Error> {
1999         let was_in_value = std::mem::replace(&mut self.in_value, true);
2000         self = self.print_def_path(def_id, substs)?;
2001         self.in_value = was_in_value;
2002
2003         Ok(self)
2004     }
2005
2006     fn in_binder<T>(self, value: &ty::Binder<'tcx, T>) -> Result<Self, Self::Error>
2007     where
2008         T: Print<'tcx, Self, Output = Self, Error = Self::Error> + TypeFoldable<'tcx>,
2009     {
2010         self.pretty_in_binder(value)
2011     }
2012
2013     fn wrap_binder<T, C: FnOnce(&T, Self) -> Result<Self, Self::Error>>(
2014         self,
2015         value: &ty::Binder<'tcx, T>,
2016         f: C,
2017     ) -> Result<Self, Self::Error>
2018     where
2019         T: Print<'tcx, Self, Output = Self, Error = Self::Error> + TypeFoldable<'tcx>,
2020     {
2021         self.pretty_wrap_binder(value, f)
2022     }
2023
2024     fn typed_value(
2025         mut self,
2026         f: impl FnOnce(Self) -> Result<Self, Self::Error>,
2027         t: impl FnOnce(Self) -> Result<Self, Self::Error>,
2028         conversion: &str,
2029     ) -> Result<Self::Const, Self::Error> {
2030         self.write_str("{")?;
2031         self = f(self)?;
2032         self.write_str(conversion)?;
2033         let was_in_value = std::mem::replace(&mut self.in_value, false);
2034         self = t(self)?;
2035         self.in_value = was_in_value;
2036         self.write_str("}")?;
2037         Ok(self)
2038     }
2039
2040     fn generic_delimiters(
2041         mut self,
2042         f: impl FnOnce(Self) -> Result<Self, Self::Error>,
2043     ) -> Result<Self, Self::Error> {
2044         write!(self, "<")?;
2045
2046         let was_in_value = std::mem::replace(&mut self.in_value, false);
2047         let mut inner = f(self)?;
2048         inner.in_value = was_in_value;
2049
2050         write!(inner, ">")?;
2051         Ok(inner)
2052     }
2053
2054     fn should_print_region(&self, region: ty::Region<'tcx>) -> bool {
2055         let highlight = self.region_highlight_mode;
2056         if highlight.region_highlighted(region).is_some() {
2057             return true;
2058         }
2059
2060         if self.should_print_verbose() {
2061             return true;
2062         }
2063
2064         let identify_regions = self.tcx.sess.opts.unstable_opts.identify_regions;
2065
2066         match *region {
2067             ty::ReEarlyBound(ref data) => data.has_name(),
2068
2069             ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
2070             | ty::ReFree(ty::FreeRegion { bound_region: br, .. })
2071             | ty::RePlaceholder(ty::Placeholder { name: br, .. }) => {
2072                 if br.is_named() {
2073                     return true;
2074                 }
2075
2076                 if let Some((region, _)) = highlight.highlight_bound_region {
2077                     if br == region {
2078                         return true;
2079                     }
2080                 }
2081
2082                 false
2083             }
2084
2085             ty::ReVar(_) if identify_regions => true,
2086
2087             ty::ReVar(_) | ty::ReErased => false,
2088
2089             ty::ReStatic => true,
2090         }
2091     }
2092
2093     fn pretty_print_const_pointer<Prov: Provenance>(
2094         self,
2095         p: Pointer<Prov>,
2096         ty: Ty<'tcx>,
2097         print_ty: bool,
2098     ) -> Result<Self::Const, Self::Error> {
2099         let print = |mut this: Self| {
2100             define_scoped_cx!(this);
2101             if this.print_alloc_ids {
2102                 p!(write("{:?}", p));
2103             } else {
2104                 p!("&_");
2105             }
2106             Ok(this)
2107         };
2108         if print_ty {
2109             self.typed_value(print, |this| this.print_type(ty), ": ")
2110         } else {
2111             print(self)
2112         }
2113     }
2114 }
2115
2116 // HACK(eddyb) limited to `FmtPrinter` because of `region_highlight_mode`.
2117 impl<'tcx> FmtPrinter<'_, 'tcx> {
2118     pub fn pretty_print_region(mut self, region: ty::Region<'tcx>) -> Result<Self, fmt::Error> {
2119         define_scoped_cx!(self);
2120
2121         // Watch out for region highlights.
2122         let highlight = self.region_highlight_mode;
2123         if let Some(n) = highlight.region_highlighted(region) {
2124             p!(write("'{}", n));
2125             return Ok(self);
2126         }
2127
2128         if self.should_print_verbose() {
2129             p!(write("{:?}", region));
2130             return Ok(self);
2131         }
2132
2133         let identify_regions = self.tcx.sess.opts.unstable_opts.identify_regions;
2134
2135         // These printouts are concise. They do not contain all the information
2136         // the user might want to diagnose an error, but there is basically no way
2137         // to fit that into a short string. Hence the recommendation to use
2138         // `explain_region()` or `note_and_explain_region()`.
2139         match *region {
2140             ty::ReEarlyBound(ref data) => {
2141                 if data.name != kw::Empty {
2142                     p!(write("{}", data.name));
2143                     return Ok(self);
2144                 }
2145             }
2146             ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
2147             | ty::ReFree(ty::FreeRegion { bound_region: br, .. })
2148             | ty::RePlaceholder(ty::Placeholder { name: br, .. }) => {
2149                 if let ty::BrNamed(_, name) = br && br.is_named() {
2150                     p!(write("{}", name));
2151                     return Ok(self);
2152                 }
2153
2154                 if let Some((region, counter)) = highlight.highlight_bound_region {
2155                     if br == region {
2156                         p!(write("'{}", counter));
2157                         return Ok(self);
2158                     }
2159                 }
2160             }
2161             ty::ReVar(region_vid) if identify_regions => {
2162                 p!(write("{:?}", region_vid));
2163                 return Ok(self);
2164             }
2165             ty::ReVar(_) => {}
2166             ty::ReErased => {}
2167             ty::ReStatic => {
2168                 p!("'static");
2169                 return Ok(self);
2170             }
2171         }
2172
2173         p!("'_");
2174
2175         Ok(self)
2176     }
2177 }
2178
2179 /// Folds through bound vars and placeholders, naming them
2180 struct RegionFolder<'a, 'tcx> {
2181     tcx: TyCtxt<'tcx>,
2182     current_index: ty::DebruijnIndex,
2183     region_map: BTreeMap<ty::BoundRegion, ty::Region<'tcx>>,
2184     name: &'a mut (
2185                 dyn FnMut(
2186         Option<ty::DebruijnIndex>, // Debruijn index of the folded late-bound region
2187         ty::DebruijnIndex,         // Index corresponding to binder level
2188         ty::BoundRegion,
2189     ) -> ty::Region<'tcx>
2190                     + 'a
2191             ),
2192 }
2193
2194 impl<'a, 'tcx> ty::TypeFolder<'tcx> for RegionFolder<'a, 'tcx> {
2195     fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
2196         self.tcx
2197     }
2198
2199     fn fold_binder<T: TypeFoldable<'tcx>>(
2200         &mut self,
2201         t: ty::Binder<'tcx, T>,
2202     ) -> ty::Binder<'tcx, T> {
2203         self.current_index.shift_in(1);
2204         let t = t.super_fold_with(self);
2205         self.current_index.shift_out(1);
2206         t
2207     }
2208
2209     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
2210         match *t.kind() {
2211             _ if t.has_vars_bound_at_or_above(self.current_index) || t.has_placeholders() => {
2212                 return t.super_fold_with(self);
2213             }
2214             _ => {}
2215         }
2216         t
2217     }
2218
2219     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
2220         let name = &mut self.name;
2221         let region = match *r {
2222             ty::ReLateBound(db, br) if db >= self.current_index => {
2223                 *self.region_map.entry(br).or_insert_with(|| name(Some(db), self.current_index, br))
2224             }
2225             ty::RePlaceholder(ty::PlaceholderRegion { name: kind, .. }) => {
2226                 // If this is an anonymous placeholder, don't rename. Otherwise, in some
2227                 // async fns, we get a `for<'r> Send` bound
2228                 match kind {
2229                     ty::BrAnon(..) | ty::BrEnv => r,
2230                     _ => {
2231                         // Index doesn't matter, since this is just for naming and these never get bound
2232                         let br = ty::BoundRegion { var: ty::BoundVar::from_u32(0), kind };
2233                         *self
2234                             .region_map
2235                             .entry(br)
2236                             .or_insert_with(|| name(None, self.current_index, br))
2237                     }
2238                 }
2239             }
2240             _ => return r,
2241         };
2242         if let ty::ReLateBound(debruijn1, br) = *region {
2243             assert_eq!(debruijn1, ty::INNERMOST);
2244             self.tcx.mk_region(ty::ReLateBound(self.current_index, br))
2245         } else {
2246             region
2247         }
2248     }
2249 }
2250
2251 // HACK(eddyb) limited to `FmtPrinter` because of `binder_depth`,
2252 // `region_index` and `used_region_names`.
2253 impl<'tcx> FmtPrinter<'_, 'tcx> {
2254     pub fn name_all_regions<T>(
2255         mut self,
2256         value: &ty::Binder<'tcx, T>,
2257     ) -> Result<(Self, T, BTreeMap<ty::BoundRegion, ty::Region<'tcx>>), fmt::Error>
2258     where
2259         T: Print<'tcx, Self, Output = Self, Error = fmt::Error> + TypeFoldable<'tcx>,
2260     {
2261         fn name_by_region_index(
2262             index: usize,
2263             available_names: &mut Vec<Symbol>,
2264             num_available: usize,
2265         ) -> Symbol {
2266             if let Some(name) = available_names.pop() {
2267                 name
2268             } else {
2269                 Symbol::intern(&format!("'z{}", index - num_available))
2270             }
2271         }
2272
2273         debug!("name_all_regions");
2274
2275         // Replace any anonymous late-bound regions with named
2276         // variants, using new unique identifiers, so that we can
2277         // clearly differentiate between named and unnamed regions in
2278         // the output. We'll probably want to tweak this over time to
2279         // decide just how much information to give.
2280         if self.binder_depth == 0 {
2281             self.prepare_region_info(value);
2282         }
2283
2284         debug!("self.used_region_names: {:?}", &self.used_region_names);
2285
2286         let mut empty = true;
2287         let mut start_or_continue = |cx: &mut Self, start: &str, cont: &str| {
2288             let w = if empty {
2289                 empty = false;
2290                 start
2291             } else {
2292                 cont
2293             };
2294             let _ = write!(cx, "{}", w);
2295         };
2296         let do_continue = |cx: &mut Self, cont: Symbol| {
2297             let _ = write!(cx, "{}", cont);
2298         };
2299
2300         define_scoped_cx!(self);
2301
2302         let possible_names = ('a'..='z').rev().map(|s| Symbol::intern(&format!("'{s}")));
2303
2304         let mut available_names = possible_names
2305             .filter(|name| !self.used_region_names.contains(&name))
2306             .collect::<Vec<_>>();
2307         debug!(?available_names);
2308         let num_available = available_names.len();
2309
2310         let mut region_index = self.region_index;
2311         let mut next_name = |this: &Self| {
2312             let mut name;
2313
2314             loop {
2315                 name = name_by_region_index(region_index, &mut available_names, num_available);
2316                 region_index += 1;
2317
2318                 if !this.used_region_names.contains(&name) {
2319                     break;
2320                 }
2321             }
2322
2323             name
2324         };
2325
2326         // If we want to print verbosely, then print *all* binders, even if they
2327         // aren't named. Eventually, we might just want this as the default, but
2328         // this is not *quite* right and changes the ordering of some output
2329         // anyways.
2330         let (new_value, map) = if self.should_print_verbose() {
2331             for var in value.bound_vars().iter() {
2332                 start_or_continue(&mut self, "for<", ", ");
2333                 write!(self, "{:?}", var)?;
2334             }
2335             start_or_continue(&mut self, "", "> ");
2336             (value.clone().skip_binder(), BTreeMap::default())
2337         } else {
2338             let tcx = self.tcx;
2339
2340             // Closure used in `RegionFolder` to create names for anonymous late-bound
2341             // regions. We use two `DebruijnIndex`es (one for the currently folded
2342             // late-bound region and the other for the binder level) to determine
2343             // whether a name has already been created for the currently folded region,
2344             // see issue #102392.
2345             let mut name = |lifetime_idx: Option<ty::DebruijnIndex>,
2346                             binder_level_idx: ty::DebruijnIndex,
2347                             br: ty::BoundRegion| {
2348                 let (name, kind) = match br.kind {
2349                     ty::BrAnon(..) | ty::BrEnv => {
2350                         let name = next_name(&self);
2351
2352                         if let Some(lt_idx) = lifetime_idx {
2353                             if lt_idx > binder_level_idx {
2354                                 let kind = ty::BrNamed(CRATE_DEF_ID.to_def_id(), name);
2355                                 return tcx.mk_region(ty::ReLateBound(
2356                                     ty::INNERMOST,
2357                                     ty::BoundRegion { var: br.var, kind },
2358                                 ));
2359                             }
2360                         }
2361
2362                         (name, ty::BrNamed(CRATE_DEF_ID.to_def_id(), name))
2363                     }
2364                     ty::BrNamed(def_id, kw::UnderscoreLifetime | kw::Empty) => {
2365                         let name = next_name(&self);
2366
2367                         if let Some(lt_idx) = lifetime_idx {
2368                             if lt_idx > binder_level_idx {
2369                                 let kind = ty::BrNamed(def_id, name);
2370                                 return tcx.mk_region(ty::ReLateBound(
2371                                     ty::INNERMOST,
2372                                     ty::BoundRegion { var: br.var, kind },
2373                                 ));
2374                             }
2375                         }
2376
2377                         (name, ty::BrNamed(def_id, name))
2378                     }
2379                     ty::BrNamed(_, name) => {
2380                         if let Some(lt_idx) = lifetime_idx {
2381                             if lt_idx > binder_level_idx {
2382                                 let kind = br.kind;
2383                                 return tcx.mk_region(ty::ReLateBound(
2384                                     ty::INNERMOST,
2385                                     ty::BoundRegion { var: br.var, kind },
2386                                 ));
2387                             }
2388                         }
2389
2390                         (name, br.kind)
2391                     }
2392                 };
2393
2394                 start_or_continue(&mut self, "for<", ", ");
2395                 do_continue(&mut self, name);
2396                 tcx.mk_region(ty::ReLateBound(ty::INNERMOST, ty::BoundRegion { var: br.var, kind }))
2397             };
2398             let mut folder = RegionFolder {
2399                 tcx,
2400                 current_index: ty::INNERMOST,
2401                 name: &mut name,
2402                 region_map: BTreeMap::new(),
2403             };
2404             let new_value = value.clone().skip_binder().fold_with(&mut folder);
2405             let region_map = folder.region_map;
2406             start_or_continue(&mut self, "", "> ");
2407             (new_value, region_map)
2408         };
2409
2410         self.binder_depth += 1;
2411         self.region_index = region_index;
2412         Ok((self, new_value, map))
2413     }
2414
2415     pub fn pretty_in_binder<T>(self, value: &ty::Binder<'tcx, T>) -> Result<Self, fmt::Error>
2416     where
2417         T: Print<'tcx, Self, Output = Self, Error = fmt::Error> + TypeFoldable<'tcx>,
2418     {
2419         let old_region_index = self.region_index;
2420         let (new, new_value, _) = self.name_all_regions(value)?;
2421         let mut inner = new_value.print(new)?;
2422         inner.region_index = old_region_index;
2423         inner.binder_depth -= 1;
2424         Ok(inner)
2425     }
2426
2427     pub fn pretty_wrap_binder<T, C: FnOnce(&T, Self) -> Result<Self, fmt::Error>>(
2428         self,
2429         value: &ty::Binder<'tcx, T>,
2430         f: C,
2431     ) -> Result<Self, fmt::Error>
2432     where
2433         T: Print<'tcx, Self, Output = Self, Error = fmt::Error> + TypeFoldable<'tcx>,
2434     {
2435         let old_region_index = self.region_index;
2436         let (new, new_value, _) = self.name_all_regions(value)?;
2437         let mut inner = f(&new_value, new)?;
2438         inner.region_index = old_region_index;
2439         inner.binder_depth -= 1;
2440         Ok(inner)
2441     }
2442
2443     fn prepare_region_info<T>(&mut self, value: &ty::Binder<'tcx, T>)
2444     where
2445         T: TypeVisitable<'tcx>,
2446     {
2447         struct RegionNameCollector<'tcx> {
2448             used_region_names: FxHashSet<Symbol>,
2449             type_collector: SsoHashSet<Ty<'tcx>>,
2450         }
2451
2452         impl<'tcx> RegionNameCollector<'tcx> {
2453             fn new() -> Self {
2454                 RegionNameCollector {
2455                     used_region_names: Default::default(),
2456                     type_collector: SsoHashSet::new(),
2457                 }
2458             }
2459         }
2460
2461         impl<'tcx> ty::visit::TypeVisitor<'tcx> for RegionNameCollector<'tcx> {
2462             type BreakTy = ();
2463
2464             fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
2465                 trace!("address: {:p}", r.0.0);
2466
2467                 // Collect all named lifetimes. These allow us to prevent duplication
2468                 // of already existing lifetime names when introducing names for
2469                 // anonymous late-bound regions.
2470                 if let Some(name) = r.get_name() {
2471                     self.used_region_names.insert(name);
2472                 }
2473
2474                 r.super_visit_with(self)
2475             }
2476
2477             // We collect types in order to prevent really large types from compiling for
2478             // a really long time. See issue #83150 for why this is necessary.
2479             fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
2480                 let not_previously_inserted = self.type_collector.insert(ty);
2481                 if not_previously_inserted {
2482                     ty.super_visit_with(self)
2483                 } else {
2484                     ControlFlow::CONTINUE
2485                 }
2486             }
2487         }
2488
2489         let mut collector = RegionNameCollector::new();
2490         value.visit_with(&mut collector);
2491         self.used_region_names = collector.used_region_names;
2492         self.region_index = 0;
2493     }
2494 }
2495
2496 impl<'tcx, T, P: PrettyPrinter<'tcx>> Print<'tcx, P> for ty::Binder<'tcx, T>
2497 where
2498     T: Print<'tcx, P, Output = P, Error = P::Error> + TypeFoldable<'tcx>,
2499 {
2500     type Output = P;
2501     type Error = P::Error;
2502
2503     fn print(&self, cx: P) -> Result<Self::Output, Self::Error> {
2504         cx.in_binder(self)
2505     }
2506 }
2507
2508 impl<'tcx, T, U, P: PrettyPrinter<'tcx>> Print<'tcx, P> for ty::OutlivesPredicate<T, U>
2509 where
2510     T: Print<'tcx, P, Output = P, Error = P::Error>,
2511     U: Print<'tcx, P, Output = P, Error = P::Error>,
2512 {
2513     type Output = P;
2514     type Error = P::Error;
2515     fn print(&self, mut cx: P) -> Result<Self::Output, Self::Error> {
2516         define_scoped_cx!(cx);
2517         p!(print(self.0), ": ", print(self.1));
2518         Ok(cx)
2519     }
2520 }
2521
2522 macro_rules! forward_display_to_print {
2523     ($($ty:ty),+) => {
2524         // Some of the $ty arguments may not actually use 'tcx
2525         $(#[allow(unused_lifetimes)] impl<'tcx> fmt::Display for $ty {
2526             fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2527                 ty::tls::with(|tcx| {
2528                     let cx = tcx.lift(*self)
2529                         .expect("could not lift for printing")
2530                         .print(FmtPrinter::new(tcx, Namespace::TypeNS))?;
2531                     f.write_str(&cx.into_buffer())?;
2532                     Ok(())
2533                 })
2534             }
2535         })+
2536     };
2537 }
2538
2539 macro_rules! define_print_and_forward_display {
2540     (($self:ident, $cx:ident): $($ty:ty $print:block)+) => {
2541         $(impl<'tcx, P: PrettyPrinter<'tcx>> Print<'tcx, P> for $ty {
2542             type Output = P;
2543             type Error = fmt::Error;
2544             fn print(&$self, $cx: P) -> Result<Self::Output, Self::Error> {
2545                 #[allow(unused_mut)]
2546                 let mut $cx = $cx;
2547                 define_scoped_cx!($cx);
2548                 let _: () = $print;
2549                 #[allow(unreachable_code)]
2550                 Ok($cx)
2551             }
2552         })+
2553
2554         forward_display_to_print!($($ty),+);
2555     };
2556 }
2557
2558 /// Wrapper type for `ty::TraitRef` which opts-in to pretty printing only
2559 /// the trait path. That is, it will print `Trait<U>` instead of
2560 /// `<T as Trait<U>>`.
2561 #[derive(Copy, Clone, TypeFoldable, TypeVisitable, Lift)]
2562 pub struct TraitRefPrintOnlyTraitPath<'tcx>(ty::TraitRef<'tcx>);
2563
2564 impl<'tcx> fmt::Debug for TraitRefPrintOnlyTraitPath<'tcx> {
2565     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2566         fmt::Display::fmt(self, f)
2567     }
2568 }
2569
2570 /// Wrapper type for `ty::TraitRef` which opts-in to pretty printing only
2571 /// the trait name. That is, it will print `Trait` instead of
2572 /// `<T as Trait<U>>`.
2573 #[derive(Copy, Clone, TypeFoldable, TypeVisitable, Lift)]
2574 pub struct TraitRefPrintOnlyTraitName<'tcx>(ty::TraitRef<'tcx>);
2575
2576 impl<'tcx> fmt::Debug for TraitRefPrintOnlyTraitName<'tcx> {
2577     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2578         fmt::Display::fmt(self, f)
2579     }
2580 }
2581
2582 impl<'tcx> ty::TraitRef<'tcx> {
2583     pub fn print_only_trait_path(self) -> TraitRefPrintOnlyTraitPath<'tcx> {
2584         TraitRefPrintOnlyTraitPath(self)
2585     }
2586
2587     pub fn print_only_trait_name(self) -> TraitRefPrintOnlyTraitName<'tcx> {
2588         TraitRefPrintOnlyTraitName(self)
2589     }
2590 }
2591
2592 impl<'tcx> ty::Binder<'tcx, ty::TraitRef<'tcx>> {
2593     pub fn print_only_trait_path(self) -> ty::Binder<'tcx, TraitRefPrintOnlyTraitPath<'tcx>> {
2594         self.map_bound(|tr| tr.print_only_trait_path())
2595     }
2596 }
2597
2598 #[derive(Copy, Clone, TypeFoldable, TypeVisitable, Lift)]
2599 pub struct TraitPredPrintModifiersAndPath<'tcx>(ty::TraitPredicate<'tcx>);
2600
2601 impl<'tcx> fmt::Debug for TraitPredPrintModifiersAndPath<'tcx> {
2602     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2603         fmt::Display::fmt(self, f)
2604     }
2605 }
2606
2607 impl<'tcx> ty::TraitPredicate<'tcx> {
2608     pub fn print_modifiers_and_trait_path(self) -> TraitPredPrintModifiersAndPath<'tcx> {
2609         TraitPredPrintModifiersAndPath(self)
2610     }
2611 }
2612
2613 impl<'tcx> ty::PolyTraitPredicate<'tcx> {
2614     pub fn print_modifiers_and_trait_path(
2615         self,
2616     ) -> ty::Binder<'tcx, TraitPredPrintModifiersAndPath<'tcx>> {
2617         self.map_bound(TraitPredPrintModifiersAndPath)
2618     }
2619 }
2620
2621 #[derive(Debug, Copy, Clone, TypeFoldable, TypeVisitable, Lift)]
2622 pub struct PrintClosureAsImpl<'tcx> {
2623     pub closure: ty::ClosureSubsts<'tcx>,
2624 }
2625
2626 forward_display_to_print! {
2627     ty::Region<'tcx>,
2628     Ty<'tcx>,
2629     &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
2630     ty::Const<'tcx>,
2631
2632     // HACK(eddyb) these are exhaustive instead of generic,
2633     // because `for<'tcx>` isn't possible yet.
2634     ty::PolyExistentialPredicate<'tcx>,
2635     ty::Binder<'tcx, ty::TraitRef<'tcx>>,
2636     ty::Binder<'tcx, ty::ExistentialTraitRef<'tcx>>,
2637     ty::Binder<'tcx, TraitRefPrintOnlyTraitPath<'tcx>>,
2638     ty::Binder<'tcx, TraitRefPrintOnlyTraitName<'tcx>>,
2639     ty::Binder<'tcx, ty::FnSig<'tcx>>,
2640     ty::Binder<'tcx, ty::TraitPredicate<'tcx>>,
2641     ty::Binder<'tcx, TraitPredPrintModifiersAndPath<'tcx>>,
2642     ty::Binder<'tcx, ty::SubtypePredicate<'tcx>>,
2643     ty::Binder<'tcx, ty::ProjectionPredicate<'tcx>>,
2644     ty::Binder<'tcx, ty::OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>>,
2645     ty::Binder<'tcx, ty::OutlivesPredicate<ty::Region<'tcx>, ty::Region<'tcx>>>,
2646
2647     ty::OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>,
2648     ty::OutlivesPredicate<ty::Region<'tcx>, ty::Region<'tcx>>
2649 }
2650
2651 define_print_and_forward_display! {
2652     (self, cx):
2653
2654     &'tcx ty::List<Ty<'tcx>> {
2655         p!("{{", comma_sep(self.iter()), "}}")
2656     }
2657
2658     ty::TypeAndMut<'tcx> {
2659         p!(write("{}", self.mutbl.prefix_str()), print(self.ty))
2660     }
2661
2662     ty::ExistentialTraitRef<'tcx> {
2663         // Use a type that can't appear in defaults of type parameters.
2664         let dummy_self = cx.tcx().mk_ty_infer(ty::FreshTy(0));
2665         let trait_ref = self.with_self_ty(cx.tcx(), dummy_self);
2666         p!(print(trait_ref.print_only_trait_path()))
2667     }
2668
2669     ty::ExistentialProjection<'tcx> {
2670         let name = cx.tcx().associated_item(self.def_id).name;
2671         p!(write("{} = ", name), print(self.term))
2672     }
2673
2674     ty::ExistentialPredicate<'tcx> {
2675         match *self {
2676             ty::ExistentialPredicate::Trait(x) => p!(print(x)),
2677             ty::ExistentialPredicate::Projection(x) => p!(print(x)),
2678             ty::ExistentialPredicate::AutoTrait(def_id) => {
2679                 p!(print_def_path(def_id, &[]));
2680             }
2681         }
2682     }
2683
2684     ty::FnSig<'tcx> {
2685         p!(write("{}", self.unsafety.prefix_str()));
2686
2687         if self.abi != Abi::Rust {
2688             p!(write("extern {} ", self.abi));
2689         }
2690
2691         p!("fn", pretty_fn_sig(self.inputs(), self.c_variadic, self.output()));
2692     }
2693
2694     ty::TraitRef<'tcx> {
2695         p!(write("<{} as {}>", self.self_ty(), self.print_only_trait_path()))
2696     }
2697
2698     TraitRefPrintOnlyTraitPath<'tcx> {
2699         p!(print_def_path(self.0.def_id, self.0.substs));
2700     }
2701
2702     TraitRefPrintOnlyTraitName<'tcx> {
2703         p!(print_def_path(self.0.def_id, &[]));
2704     }
2705
2706     TraitPredPrintModifiersAndPath<'tcx> {
2707         if let ty::BoundConstness::ConstIfConst = self.0.constness {
2708             p!("~const ")
2709         }
2710
2711         if let ty::ImplPolarity::Negative = self.0.polarity {
2712             p!("!")
2713         }
2714
2715         p!(print(self.0.trait_ref.print_only_trait_path()));
2716     }
2717
2718     PrintClosureAsImpl<'tcx> {
2719         p!(pretty_closure_as_impl(self.closure))
2720     }
2721
2722     ty::ParamTy {
2723         p!(write("{}", self.name))
2724     }
2725
2726     ty::ParamConst {
2727         p!(write("{}", self.name))
2728     }
2729
2730     ty::SubtypePredicate<'tcx> {
2731         p!(print(self.a), " <: ");
2732         cx.reset_type_limit();
2733         p!(print(self.b))
2734     }
2735
2736     ty::CoercePredicate<'tcx> {
2737         p!(print(self.a), " -> ");
2738         cx.reset_type_limit();
2739         p!(print(self.b))
2740     }
2741
2742     ty::TraitPredicate<'tcx> {
2743         p!(print(self.trait_ref.self_ty()), ": ");
2744         if let ty::BoundConstness::ConstIfConst = self.constness && cx.tcx().features().const_trait_impl {
2745             p!("~const ");
2746         }
2747         p!(print(self.trait_ref.print_only_trait_path()))
2748     }
2749
2750     ty::ProjectionPredicate<'tcx> {
2751         p!(print(self.projection_ty), " == ");
2752         cx.reset_type_limit();
2753         p!(print(self.term))
2754     }
2755
2756     ty::Term<'tcx> {
2757       match self.unpack() {
2758         ty::TermKind::Ty(ty) => p!(print(ty)),
2759         ty::TermKind::Const(c) => p!(print(c)),
2760       }
2761     }
2762
2763     ty::AliasTy<'tcx> {
2764         p!(print_def_path(self.def_id, self.substs));
2765     }
2766
2767     ty::ClosureKind {
2768         match *self {
2769             ty::ClosureKind::Fn => p!("Fn"),
2770             ty::ClosureKind::FnMut => p!("FnMut"),
2771             ty::ClosureKind::FnOnce => p!("FnOnce"),
2772         }
2773     }
2774
2775     ty::Predicate<'tcx> {
2776         let binder = self.kind();
2777         p!(print(binder))
2778     }
2779
2780     ty::PredicateKind<'tcx> {
2781         match *self {
2782             ty::PredicateKind::Clause(ty::Clause::Trait(ref data)) => {
2783                 p!(print(data))
2784             }
2785             ty::PredicateKind::Subtype(predicate) => p!(print(predicate)),
2786             ty::PredicateKind::Coerce(predicate) => p!(print(predicate)),
2787             ty::PredicateKind::Clause(ty::Clause::RegionOutlives(predicate)) => p!(print(predicate)),
2788             ty::PredicateKind::Clause(ty::Clause::TypeOutlives(predicate)) => p!(print(predicate)),
2789             ty::PredicateKind::Clause(ty::Clause::Projection(predicate)) => p!(print(predicate)),
2790             ty::PredicateKind::WellFormed(arg) => p!(print(arg), " well-formed"),
2791             ty::PredicateKind::ObjectSafe(trait_def_id) => {
2792                 p!("the trait `", print_def_path(trait_def_id, &[]), "` is object-safe")
2793             }
2794             ty::PredicateKind::ClosureKind(closure_def_id, _closure_substs, kind) => {
2795                 p!("the closure `",
2796                 print_value_path(closure_def_id, &[]),
2797                 write("` implements the trait `{}`", kind))
2798             }
2799             ty::PredicateKind::ConstEvaluatable(ct) => {
2800                 p!("the constant `", print(ct), "` can be evaluated")
2801             }
2802             ty::PredicateKind::ConstEquate(c1, c2) => {
2803                 p!("the constant `", print(c1), "` equals `", print(c2), "`")
2804             }
2805             ty::PredicateKind::TypeWellFormedFromEnv(ty) => {
2806                 p!("the type `", print(ty), "` is found in the environment")
2807             }
2808             ty::PredicateKind::Ambiguous => p!("ambiguous"),
2809         }
2810     }
2811
2812     GenericArg<'tcx> {
2813         match self.unpack() {
2814             GenericArgKind::Lifetime(lt) => p!(print(lt)),
2815             GenericArgKind::Type(ty) => p!(print(ty)),
2816             GenericArgKind::Const(ct) => p!(print(ct)),
2817         }
2818     }
2819 }
2820
2821 fn for_each_def(tcx: TyCtxt<'_>, mut collect_fn: impl for<'b> FnMut(&'b Ident, Namespace, DefId)) {
2822     // Iterate all local crate items no matter where they are defined.
2823     let hir = tcx.hir();
2824     for id in hir.items() {
2825         if matches!(tcx.def_kind(id.owner_id), DefKind::Use) {
2826             continue;
2827         }
2828
2829         let item = hir.item(id);
2830         if item.ident.name == kw::Empty {
2831             continue;
2832         }
2833
2834         let def_id = item.owner_id.to_def_id();
2835         let ns = tcx.def_kind(def_id).ns().unwrap_or(Namespace::TypeNS);
2836         collect_fn(&item.ident, ns, def_id);
2837     }
2838
2839     // Now take care of extern crate items.
2840     let queue = &mut Vec::new();
2841     let mut seen_defs: DefIdSet = Default::default();
2842
2843     for &cnum in tcx.crates(()).iter() {
2844         let def_id = cnum.as_def_id();
2845
2846         // Ignore crates that are not direct dependencies.
2847         match tcx.extern_crate(def_id) {
2848             None => continue,
2849             Some(extern_crate) => {
2850                 if !extern_crate.is_direct() {
2851                     continue;
2852                 }
2853             }
2854         }
2855
2856         queue.push(def_id);
2857     }
2858
2859     // Iterate external crate defs but be mindful about visibility
2860     while let Some(def) = queue.pop() {
2861         for child in tcx.module_children(def).iter() {
2862             if !child.vis.is_public() {
2863                 continue;
2864             }
2865
2866             match child.res {
2867                 def::Res::Def(DefKind::AssocTy, _) => {}
2868                 def::Res::Def(DefKind::TyAlias, _) => {}
2869                 def::Res::Def(defkind, def_id) => {
2870                     if let Some(ns) = defkind.ns() {
2871                         collect_fn(&child.ident, ns, def_id);
2872                     }
2873
2874                     if matches!(defkind, DefKind::Mod | DefKind::Enum | DefKind::Trait)
2875                         && seen_defs.insert(def_id)
2876                     {
2877                         queue.push(def_id);
2878                     }
2879                 }
2880                 _ => {}
2881             }
2882         }
2883     }
2884 }
2885
2886 /// The purpose of this function is to collect public symbols names that are unique across all
2887 /// crates in the build. Later, when printing about types we can use those names instead of the
2888 /// full exported path to them.
2889 ///
2890 /// So essentially, if a symbol name can only be imported from one place for a type, and as
2891 /// long as it was not glob-imported anywhere in the current crate, we can trim its printed
2892 /// path and print only the name.
2893 ///
2894 /// This has wide implications on error messages with types, for example, shortening
2895 /// `std::vec::Vec` to just `Vec`, as long as there is no other `Vec` importable anywhere.
2896 ///
2897 /// The implementation uses similar import discovery logic to that of 'use' suggestions.
2898 ///
2899 /// See also [`DelayDm`](rustc_error_messages::DelayDm) and [`with_no_trimmed_paths`].
2900 fn trimmed_def_paths(tcx: TyCtxt<'_>, (): ()) -> FxHashMap<DefId, Symbol> {
2901     let mut map: FxHashMap<DefId, Symbol> = FxHashMap::default();
2902
2903     if let TrimmedDefPaths::GoodPath = tcx.sess.opts.trimmed_def_paths {
2904         // Trimming paths is expensive and not optimized, since we expect it to only be used for error reporting.
2905         //
2906         // For good paths causing this bug, the `rustc_middle::ty::print::with_no_trimmed_paths`
2907         // wrapper can be used to suppress this query, in exchange for full paths being formatted.
2908         tcx.sess.delay_good_path_bug(
2909             "trimmed_def_paths constructed but no error emitted; use `DelayDm` for lints or `with_no_trimmed_paths` for debugging",
2910         );
2911     }
2912
2913     let unique_symbols_rev: &mut FxHashMap<(Namespace, Symbol), Option<DefId>> =
2914         &mut FxHashMap::default();
2915
2916     for symbol_set in tcx.resolutions(()).glob_map.values() {
2917         for symbol in symbol_set {
2918             unique_symbols_rev.insert((Namespace::TypeNS, *symbol), None);
2919             unique_symbols_rev.insert((Namespace::ValueNS, *symbol), None);
2920             unique_symbols_rev.insert((Namespace::MacroNS, *symbol), None);
2921         }
2922     }
2923
2924     for_each_def(tcx, |ident, ns, def_id| {
2925         use std::collections::hash_map::Entry::{Occupied, Vacant};
2926
2927         match unique_symbols_rev.entry((ns, ident.name)) {
2928             Occupied(mut v) => match v.get() {
2929                 None => {}
2930                 Some(existing) => {
2931                     if *existing != def_id {
2932                         v.insert(None);
2933                     }
2934                 }
2935             },
2936             Vacant(v) => {
2937                 v.insert(Some(def_id));
2938             }
2939         }
2940     });
2941
2942     for ((_, symbol), opt_def_id) in unique_symbols_rev.drain() {
2943         use std::collections::hash_map::Entry::{Occupied, Vacant};
2944
2945         if let Some(def_id) = opt_def_id {
2946             match map.entry(def_id) {
2947                 Occupied(mut v) => {
2948                     // A single DefId can be known under multiple names (e.g.,
2949                     // with a `pub use ... as ...;`). We need to ensure that the
2950                     // name placed in this map is chosen deterministically, so
2951                     // if we find multiple names (`symbol`) resolving to the
2952                     // same `def_id`, we prefer the lexicographically smallest
2953                     // name.
2954                     //
2955                     // Any stable ordering would be fine here though.
2956                     if *v.get() != symbol {
2957                         if v.get().as_str() > symbol.as_str() {
2958                             v.insert(symbol);
2959                         }
2960                     }
2961                 }
2962                 Vacant(v) => {
2963                     v.insert(symbol);
2964                 }
2965             }
2966         }
2967     }
2968
2969     map
2970 }
2971
2972 pub fn provide(providers: &mut ty::query::Providers) {
2973     *providers = ty::query::Providers { trimmed_def_paths, ..*providers };
2974 }
2975
2976 #[derive(Default)]
2977 pub struct OpaqueFnEntry<'tcx> {
2978     // The trait ref is already stored as a key, so just track if we have it as a real predicate
2979     has_fn_once: bool,
2980     fn_mut_trait_ref: Option<ty::PolyTraitRef<'tcx>>,
2981     fn_trait_ref: Option<ty::PolyTraitRef<'tcx>>,
2982     return_ty: Option<ty::Binder<'tcx, Term<'tcx>>>,
2983 }