compiler/rustc_symbol_mangling/src/v0.rs

   1 use rustc_ast::{FloatTy, IntTy, UintTy};
   2 use rustc_data_structures::base_n;
   3 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
   4 use rustc_hir as hir;
   5 use rustc_hir::def_id::{CrateNum, DefId};
   6 use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
   7 use rustc_middle::ty::print::{Print, Printer};
   8 use rustc_middle::ty::subst::{GenericArg, GenericArgKind, Subst};
   9 use rustc_middle::ty::{self, Instance, Ty, TyCtxt, TypeFoldable};
  10 use rustc_target::spec::abi::Abi;
  11
  12 use std::fmt::Write;
  13 use std::ops::Range;
  14
  15 pub(super) fn mangle(
  16     tcx: TyCtxt<'tcx>,
  17     instance: Instance<'tcx>,
  18     instantiating_crate: Option<CrateNum>,
  19 ) -> String {
  20     let def_id = instance.def_id();
  21     // FIXME(eddyb) this should ideally not be needed.
  22     let substs = tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), instance.substs);
  23
  24     let prefix = "_R";
  25     let mut cx = SymbolMangler {
  26         tcx,
  27         compress: Some(Box::new(CompressionCaches {
  28             start_offset: prefix.len(),
  29
  30             paths: FxHashMap::default(),
  31             types: FxHashMap::default(),
  32             consts: FxHashMap::default(),
  33         })),
  34         binders: vec![],
  35         out: String::from(prefix),
  36     };
  37
  38     // Append `::{shim:...#0}` to shims that can coexist with a non-shim instance.
  39     let shim_kind = match instance.def {
  40         ty::InstanceDef::VtableShim(_) => Some("vtable"),
  41         ty::InstanceDef::ReifyShim(_) => Some("reify"),
  42
  43         _ => None,
  44     };
  45
  46     cx = if let Some(shim_kind) = shim_kind {
  47         cx.path_append_ns(|cx| cx.print_def_path(def_id, substs), 'S', 0, shim_kind).unwrap()
  48     } else {
  49         cx.print_def_path(def_id, substs).unwrap()
  50     };
  51     if let Some(instantiating_crate) = instantiating_crate {
  52         cx = cx.print_def_path(instantiating_crate.as_def_id(), &[]).unwrap();
  53     }
  54     cx.out
  55 }
  56
  57 struct CompressionCaches<'tcx> {
  58     // The length of the prefix in `out` (e.g. 2 for `_R`).
  59     start_offset: usize,
  60
  61     // The values are start positions in `out`, in bytes.
  62     paths: FxHashMap<(DefId, &'tcx [GenericArg<'tcx>]), usize>,
  63     types: FxHashMap<Ty<'tcx>, usize>,
  64     consts: FxHashMap<&'tcx ty::Const<'tcx>, usize>,
  65 }
  66
  67 struct BinderLevel {
  68     /// The range of distances from the root of what's
  69     /// being printed, to the lifetimes in a binder.
  70     /// Specifically, a `BrAnon(i)` lifetime has depth
  71     /// `lifetime_depths.start + i`, going away from the
  72     /// the root and towards its use site, as `i` increases.
  73     /// This is used to flatten rustc's pairing of `BrAnon`
  74     /// (intra-binder disambiguation) with a `DebruijnIndex`
  75     /// (binder addressing), to "true" de Bruijn indices,
  76     /// by subtracting the depth of a certain lifetime, from
  77     /// the innermost depth at its use site.
  78     lifetime_depths: Range<u32>,
  79 }
  80
  81 struct SymbolMangler<'tcx> {
  82     tcx: TyCtxt<'tcx>,
  83     compress: Option<Box<CompressionCaches<'tcx>>>,
  84     binders: Vec<BinderLevel>,
  85     out: String,
  86 }
  87
  88 impl SymbolMangler<'tcx> {
  89     fn push(&mut self, s: &str) {
  90         self.out.push_str(s);
  91     }
  92
  93     /// Push a `_`-terminated base 62 integer, using the format
  94     /// specified in the RFC as `<base-62-number>`, that is:
  95     /// * `x = 0` is encoded as just the `"_"` terminator
  96     /// * `x > 0` is encoded as `x - 1` in base 62, followed by `"_"`,
  97     ///   e.g. `1` becomes `"0_"`, `62` becomes `"Z_"`, etc.
  98     fn push_integer_62(&mut self, x: u64) {
  99         if let Some(x) = x.checked_sub(1) {
 100             base_n::push_str(x as u128, 62, &mut self.out);
 101         }
 102         self.push("_");
 103     }
 104
 105     /// Push a `tag`-prefixed base 62 integer, when larger than `0`, that is:
 106     /// * `x = 0` is encoded as `""` (nothing)
 107     /// * `x > 0` is encoded as the `tag` followed by `push_integer_62(x - 1)`
 108     ///   e.g. `1` becomes `tag + "_"`, `2` becomes `tag + "0_"`, etc.
 109     fn push_opt_integer_62(&mut self, tag: &str, x: u64) {
 110         if let Some(x) = x.checked_sub(1) {
 111             self.push(tag);
 112             self.push_integer_62(x);
 113         }
 114     }
 115
 116     fn push_disambiguator(&mut self, dis: u64) {
 117         self.push_opt_integer_62("s", dis);
 118     }
 119
 120     fn push_ident(&mut self, ident: &str) {
 121         let mut use_punycode = false;
 122         for b in ident.bytes() {
 123             match b {
 124                 b'_' | b'a'..=b'z' | b'A'..=b'Z' | b'0'..=b'9' => {}
 125                 0x80..=0xff => use_punycode = true,
 126                 _ => bug!("symbol_names: bad byte {} in ident {:?}", b, ident),
 127             }
 128         }
 129
 130         let punycode_string;
 131         let ident = if use_punycode {
 132             self.push("u");
 133
 134             // FIXME(eddyb) we should probably roll our own punycode implementation.
 135             let mut punycode_bytes = match ::punycode::encode(ident) {
 136                 Ok(s) => s.into_bytes(),
 137                 Err(()) => bug!("symbol_names: punycode encoding failed for ident {:?}", ident),
 138             };
 139
 140             // Replace `-` with `_`.
 141             if let Some(c) = punycode_bytes.iter_mut().rfind(|&&mut c| c == b'-') {
 142                 *c = b'_';
 143             }
 144
 145             // FIXME(eddyb) avoid rechecking UTF-8 validity.
 146             punycode_string = String::from_utf8(punycode_bytes).unwrap();
 147             &punycode_string
 148         } else {
 149             ident
 150         };
 151
 152         let _ = write!(self.out, "{}", ident.len());
 153
 154         // Write a separating `_` if necessary (leading digit or `_`).
 155         if let Some('_' | '0'..='9') = ident.chars().next() {
 156             self.push("_");
 157         }
 158
 159         self.push(ident);
 160     }
 161
 162     fn path_append_ns(
 163         mut self,
 164         print_prefix: impl FnOnce(Self) -> Result<Self, !>,
 165         ns: char,
 166         disambiguator: u64,
 167         name: &str,
 168     ) -> Result<Self, !> {
 169         self.push("N");
 170         self.out.push(ns);
 171         self = print_prefix(self)?;
 172         self.push_disambiguator(disambiguator as u64);
 173         self.push_ident(name);
 174         Ok(self)
 175     }
 176
 177     fn print_backref(mut self, i: usize) -> Result<Self, !> {
 178         self.push("B");
 179         self.push_integer_62((i - self.compress.as_ref().unwrap().start_offset) as u64);
 180         Ok(self)
 181     }
 182
 183     fn in_binder<T>(
 184         mut self,
 185         value: &ty::Binder<T>,
 186         print_value: impl FnOnce(Self, &T) -> Result<Self, !>,
 187     ) -> Result<Self, !>
 188     where
 189         T: TypeFoldable<'tcx>,
 190     {
 191         let regions = if value.has_late_bound_regions() {
 192             self.tcx.collect_referenced_late_bound_regions(value)
 193         } else {
 194             FxHashSet::default()
 195         };
 196
 197         let mut lifetime_depths =
 198             self.binders.last().map(|b| b.lifetime_depths.end).map_or(0..0, |i| i..i);
 199
 200         let lifetimes = regions
 201             .into_iter()
 202             .map(|br| {
 203                 match br {
 204                     ty::BrAnon(i) => {
 205                         // FIXME(eddyb) for some reason, `anonymize_late_bound_regions` starts at `1`.
 206                         assert_ne!(i, 0);
 207                         i - 1
 208                     }
 209                     _ => bug!("symbol_names: non-anonymized region `{:?}` in `{:?}`", br, value),
 210                 }
 211             })
 212             .max()
 213             .map_or(0, |max| max + 1);
 214
 215         self.push_opt_integer_62("G", lifetimes as u64);
 216         lifetime_depths.end += lifetimes;
 217
 218         self.binders.push(BinderLevel { lifetime_depths });
 219         self = print_value(self, value.as_ref().skip_binder())?;
 220         self.binders.pop();
 221
 222         Ok(self)
 223     }
 224 }
 225
 226 impl Printer<'tcx> for SymbolMangler<'tcx> {
 227     type Error = !;
 228
 229     type Path = Self;
 230     type Region = Self;
 231     type Type = Self;
 232     type DynExistential = Self;
 233     type Const = Self;
 234
 235     fn tcx(&self) -> TyCtxt<'tcx> {
 236         self.tcx
 237     }
 238
 239     fn print_def_path(
 240         mut self,
 241         def_id: DefId,
 242         substs: &'tcx [GenericArg<'tcx>],
 243     ) -> Result<Self::Path, Self::Error> {
 244         if let Some(&i) = self.compress.as_ref().and_then(|c| c.paths.get(&(def_id, substs))) {
 245             return self.print_backref(i);
 246         }
 247         let start = self.out.len();
 248
 249         self = self.default_print_def_path(def_id, substs)?;
 250
 251         // Only cache paths that do not refer to an enclosing
 252         // binder (which would change depending on context).
 253         if !substs.iter().any(|k| k.has_escaping_bound_vars()) {
 254             if let Some(c) = &mut self.compress {
 255                 c.paths.insert((def_id, substs), start);
 256             }
 257         }
 258         Ok(self)
 259     }
 260
 261     fn print_impl_path(
 262         self,
 263         impl_def_id: DefId,
 264         substs: &'tcx [GenericArg<'tcx>],
 265         mut self_ty: Ty<'tcx>,
 266         mut impl_trait_ref: Option<ty::TraitRef<'tcx>>,
 267     ) -> Result<Self::Path, Self::Error> {
 268         let key = self.tcx.def_key(impl_def_id);
 269         let parent_def_id = DefId { index: key.parent.unwrap(), ..impl_def_id };
 270
 271         let mut param_env = self.tcx.param_env_reveal_all_normalized(impl_def_id);
 272         if !substs.is_empty() {
 273             param_env = param_env.subst(self.tcx, substs);
 274         }
 275
 276         match &mut impl_trait_ref {
 277             Some(impl_trait_ref) => {
 278                 assert_eq!(impl_trait_ref.self_ty(), self_ty);
 279                 *impl_trait_ref = self.tcx.normalize_erasing_regions(param_env, *impl_trait_ref);
 280                 self_ty = impl_trait_ref.self_ty();
 281             }
 282             None => {
 283                 self_ty = self.tcx.normalize_erasing_regions(param_env, self_ty);
 284             }
 285         }
 286
 287         self.path_append_impl(
 288             |cx| cx.print_def_path(parent_def_id, &[]),
 289             &key.disambiguated_data,
 290             self_ty,
 291             impl_trait_ref,
 292         )
 293     }
 294
 295     fn print_region(mut self, region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
 296         let i = match *region {
 297             // Erased lifetimes use the index 0, for a
 298             // shorter mangling of `L_`.
 299             ty::ReErased => 0,
 300
 301             // Late-bound lifetimes use indices starting at 1,
 302             // see `BinderLevel` for more details.
 303             ty::ReLateBound(debruijn, ty::BrAnon(i)) => {
 304                 // FIXME(eddyb) for some reason, `anonymize_late_bound_regions` starts at `1`.
 305                 assert_ne!(i, 0);
 306                 let i = i - 1;
 307
 308                 let binder = &self.binders[self.binders.len() - 1 - debruijn.index()];
 309                 let depth = binder.lifetime_depths.start + i;
 310
 311                 1 + (self.binders.last().unwrap().lifetime_depths.end - 1 - depth)
 312             }
 313
 314             _ => bug!("symbol_names: non-erased region `{:?}`", region),
 315         };
 316         self.push("L");
 317         self.push_integer_62(i as u64);
 318         Ok(self)
 319     }
 320
 321     fn print_type(mut self, ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
 322         // Basic types, never cached (single-character).
 323         let basic_type = match ty.kind() {
 324             ty::Bool => "b",
 325             ty::Char => "c",
 326             ty::Str => "e",
 327             ty::Tuple(_) if ty.is_unit() => "u",
 328             ty::Int(IntTy::I8) => "a",
 329             ty::Int(IntTy::I16) => "s",
 330             ty::Int(IntTy::I32) => "l",
 331             ty::Int(IntTy::I64) => "x",
 332             ty::Int(IntTy::I128) => "n",
 333             ty::Int(IntTy::Isize) => "i",
 334             ty::Uint(UintTy::U8) => "h",
 335             ty::Uint(UintTy::U16) => "t",
 336             ty::Uint(UintTy::U32) => "m",
 337             ty::Uint(UintTy::U64) => "y",
 338             ty::Uint(UintTy::U128) => "o",
 339             ty::Uint(UintTy::Usize) => "j",
 340             ty::Float(FloatTy::F32) => "f",
 341             ty::Float(FloatTy::F64) => "d",
 342             ty::Never => "z",
 343
 344             // Placeholders (should be demangled as `_`).
 345             ty::Param(_) | ty::Bound(..) | ty::Placeholder(_) | ty::Infer(_) | ty::Error(_) => "p",
 346
 347             _ => "",
 348         };
 349         if !basic_type.is_empty() {
 350             self.push(basic_type);
 351             return Ok(self);
 352         }
 353
 354         if let Some(&i) = self.compress.as_ref().and_then(|c| c.types.get(&ty)) {
 355             return self.print_backref(i);
 356         }
 357         let start = self.out.len();
 358
 359         match *ty.kind() {
 360             // Basic types, handled above.
 361             ty::Bool | ty::Char | ty::Str | ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::Never => {
 362                 unreachable!()
 363             }
 364             ty::Tuple(_) if ty.is_unit() => unreachable!(),
 365
 366             // Placeholders, also handled as part of basic types.
 367             ty::Param(_) | ty::Bound(..) | ty::Placeholder(_) | ty::Infer(_) | ty::Error(_) => {
 368                 unreachable!()
 369             }
 370
 371             ty::Ref(r, ty, mutbl) => {
 372                 self.push(match mutbl {
 373                     hir::Mutability::Not => "R",
 374                     hir::Mutability::Mut => "Q",
 375                 });
 376                 if *r != ty::ReErased {
 377                     self = r.print(self)?;
 378                 }
 379                 self = ty.print(self)?;
 380             }
 381
 382             ty::RawPtr(mt) => {
 383                 self.push(match mt.mutbl {
 384                     hir::Mutability::Not => "P",
 385                     hir::Mutability::Mut => "O",
 386                 });
 387                 self = mt.ty.print(self)?;
 388             }
 389
 390             ty::Array(ty, len) => {
 391                 self.push("A");
 392                 self = ty.print(self)?;
 393                 self = self.print_const(len)?;
 394             }
 395             ty::Slice(ty) => {
 396                 self.push("S");
 397                 self = ty.print(self)?;
 398             }
 399
 400             ty::Tuple(tys) => {
 401                 self.push("T");
 402                 for ty in tys.iter().map(|k| k.expect_ty()) {
 403                     self = ty.print(self)?;
 404                 }
 405                 self.push("E");
 406             }
 407
 408             // Mangle all nominal types as paths.
 409             ty::Adt(&ty::AdtDef { did: def_id, .. }, substs)
 410             | ty::FnDef(def_id, substs)
 411             | ty::Opaque(def_id, substs)
 412             | ty::Projection(ty::ProjectionTy { item_def_id: def_id, substs })
 413             | ty::Closure(def_id, substs)
 414             | ty::Generator(def_id, substs, _) => {
 415                 self = self.print_def_path(def_id, substs)?;
 416             }
 417             ty::Foreign(def_id) => {
 418                 self = self.print_def_path(def_id, &[])?;
 419             }
 420
 421             ty::FnPtr(sig) => {
 422                 self.push("F");
 423                 self = self.in_binder(&sig, |mut cx, sig| {
 424                     if sig.unsafety == hir::Unsafety::Unsafe {
 425                         cx.push("U");
 426                     }
 427                     match sig.abi {
 428                         Abi::Rust => {}
 429                         Abi::C => cx.push("KC"),
 430                         abi => {
 431                             cx.push("K");
 432                             let name = abi.name();
 433                             if name.contains('-') {
 434                                 cx.push_ident(&name.replace('-', "_"));
 435                             } else {
 436                                 cx.push_ident(name);
 437                             }
 438                         }
 439                     }
 440                     for &ty in sig.inputs() {
 441                         cx = ty.print(cx)?;
 442                     }
 443                     if sig.c_variadic {
 444                         cx.push("v");
 445                     }
 446                     cx.push("E");
 447                     sig.output().print(cx)
 448                 })?;
 449             }
 450
 451             ty::Dynamic(predicates, r) => {
 452                 self.push("D");
 453                 self = self.in_binder(&predicates, |cx, predicates| {
 454                     cx.print_dyn_existential(predicates)
 455                 })?;
 456                 self = r.print(self)?;
 457             }
 458
 459             ty::GeneratorWitness(_) => bug!("symbol_names: unexpected `GeneratorWitness`"),
 460         }
 461
 462         // Only cache types that do not refer to an enclosing
 463         // binder (which would change depending on context).
 464         if !ty.has_escaping_bound_vars() {
 465             if let Some(c) = &mut self.compress {
 466                 c.types.insert(ty, start);
 467             }
 468         }
 469         Ok(self)
 470     }
 471
 472     fn print_dyn_existential(
 473         mut self,
 474         predicates: &'tcx ty::List<ty::ExistentialPredicate<'tcx>>,
 475     ) -> Result<Self::DynExistential, Self::Error> {
 476         for predicate in predicates {
 477             match predicate {
 478                 ty::ExistentialPredicate::Trait(trait_ref) => {
 479                     // Use a type that can't appear in defaults of type parameters.
 480                     let dummy_self = self.tcx.mk_ty_infer(ty::FreshTy(0));
 481                     let trait_ref = trait_ref.with_self_ty(self.tcx, dummy_self);
 482                     self = self.print_def_path(trait_ref.def_id, trait_ref.substs)?;
 483                 }
 484                 ty::ExistentialPredicate::Projection(projection) => {
 485                     let name = self.tcx.associated_item(projection.item_def_id).ident;
 486                     self.push("p");
 487                     self.push_ident(&name.as_str());
 488                     self = projection.ty.print(self)?;
 489                 }
 490                 ty::ExistentialPredicate::AutoTrait(def_id) => {
 491                     self = self.print_def_path(def_id, &[])?;
 492                 }
 493             }
 494         }
 495         self.push("E");
 496         Ok(self)
 497     }
 498
 499     fn print_const(mut self, ct: &'tcx ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
 500         if let Some(&i) = self.compress.as_ref().and_then(|c| c.consts.get(&ct)) {
 501             return self.print_backref(i);
 502         }
 503         let start = self.out.len();
 504
 505         match ct.ty.kind() {
 506             ty::Uint(_) => {}
 507             ty::Bool => {}
 508             _ => {
 509                 bug!("symbol_names: unsupported constant of type `{}` ({:?})", ct.ty, ct);
 510             }
 511         }
 512         self = ct.ty.print(self)?;
 513
 514         if let Some(bits) = ct.try_eval_bits(self.tcx, ty::ParamEnv::reveal_all(), ct.ty) {
 515             let _ = write!(self.out, "{:x}_", bits);
 516         } else {
 517             // NOTE(eddyb) despite having the path, we need to
 518             // encode a placeholder, as the path could refer
 519             // back to e.g. an `impl` using the constant.
 520             self.push("p");
 521         }
 522
 523         // Only cache consts that do not refer to an enclosing
 524         // binder (which would change depending on context).
 525         if !ct.has_escaping_bound_vars() {
 526             if let Some(c) = &mut self.compress {
 527                 c.consts.insert(ct, start);
 528             }
 529         }
 530         Ok(self)
 531     }
 532
 533     fn path_crate(mut self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
 534         self.push("C");
 535         let fingerprint = self.tcx.crate_disambiguator(cnum).to_fingerprint();
 536         self.push_disambiguator(fingerprint.to_smaller_hash());
 537         let name = self.tcx.original_crate_name(cnum).as_str();
 538         self.push_ident(&name);
 539         Ok(self)
 540     }
 541     fn path_qualified(
 542         mut self,
 543         self_ty: Ty<'tcx>,
 544         trait_ref: Option<ty::TraitRef<'tcx>>,
 545     ) -> Result<Self::Path, Self::Error> {
 546         assert!(trait_ref.is_some());
 547         let trait_ref = trait_ref.unwrap();
 548
 549         self.push("Y");
 550         self = self_ty.print(self)?;
 551         self.print_def_path(trait_ref.def_id, trait_ref.substs)
 552     }
 553
 554     fn path_append_impl(
 555         mut self,
 556         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
 557         disambiguated_data: &DisambiguatedDefPathData,
 558         self_ty: Ty<'tcx>,
 559         trait_ref: Option<ty::TraitRef<'tcx>>,
 560     ) -> Result<Self::Path, Self::Error> {
 561         self.push(match trait_ref {
 562             Some(_) => "X",
 563             None => "M",
 564         });
 565         self.push_disambiguator(disambiguated_data.disambiguator as u64);
 566         self = print_prefix(self)?;
 567         self = self_ty.print(self)?;
 568         if let Some(trait_ref) = trait_ref {
 569             self = self.print_def_path(trait_ref.def_id, trait_ref.substs)?;
 570         }
 571         Ok(self)
 572     }
 573     fn path_append(
 574         self,
 575         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
 576         disambiguated_data: &DisambiguatedDefPathData,
 577     ) -> Result<Self::Path, Self::Error> {
 578         let ns = match disambiguated_data.data {
 579             // Uppercase categories are more stable than lowercase ones.
 580             DefPathData::TypeNs(_) => 't',
 581             DefPathData::ValueNs(_) => 'v',
 582             DefPathData::ClosureExpr => 'C',
 583             DefPathData::Ctor => 'c',
 584             DefPathData::AnonConst => 'k',
 585             DefPathData::ImplTrait => 'i',
 586
 587             // These should never show up as `path_append` arguments.
 588             DefPathData::CrateRoot
 589             | DefPathData::Misc
 590             | DefPathData::Impl
 591             | DefPathData::MacroNs(_)
 592             | DefPathData::LifetimeNs(_) => {
 593                 bug!("symbol_names: unexpected DefPathData: {:?}", disambiguated_data.data)
 594             }
 595         };
 596
 597         let name = disambiguated_data.data.get_opt_name().map(|s| s.as_str());
 598
 599         self.path_append_ns(
 600             print_prefix,
 601             ns,
 602             disambiguated_data.disambiguator as u64,
 603             name.as_ref().map_or("", |s| &s[..]),
 604         )
 605     }
 606     fn path_generic_args(
 607         mut self,
 608         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
 609         args: &[GenericArg<'tcx>],
 610     ) -> Result<Self::Path, Self::Error> {
 611         // Don't print any regions if they're all erased.
 612         let print_regions = args.iter().any(|arg| match arg.unpack() {
 613             GenericArgKind::Lifetime(r) => *r != ty::ReErased,
 614             _ => false,
 615         });
 616         let args = args.iter().cloned().filter(|arg| match arg.unpack() {
 617             GenericArgKind::Lifetime(_) => print_regions,
 618             _ => true,
 619         });
 620
 621         if args.clone().next().is_none() {
 622             return print_prefix(self);
 623         }
 624
 625         self.push("I");
 626         self = print_prefix(self)?;
 627         for arg in args {
 628             match arg.unpack() {
 629                 GenericArgKind::Lifetime(lt) => {
 630                     self = lt.print(self)?;
 631                 }
 632                 GenericArgKind::Type(ty) => {
 633                     self = ty.print(self)?;
 634                 }
 635                 GenericArgKind::Const(c) => {
 636                     self.push("K");
 637                     self = c.print(self)?;
 638                 }
 639             }
 640         }
 641         self.push("E");
 642
 643         Ok(self)
 644     }
 645 }