rustc_symbol_mangling/
v0.rs

1use std::fmt::Write;
2use std::hash::Hasher;
3use std::iter;
4use std::ops::Range;
5
6use rustc_abi::{ExternAbi, Integer};
7use rustc_data_structures::base_n::ToBaseN;
8use rustc_data_structures::fx::FxHashMap;
9use rustc_data_structures::intern::Interned;
10use rustc_data_structures::stable_hasher::StableHasher;
11use rustc_hashes::Hash64;
12use rustc_hir as hir;
13use rustc_hir::def::CtorKind;
14use rustc_hir::def_id::{CrateNum, DefId};
15use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
16use rustc_middle::bug;
17use rustc_middle::ty::layout::IntegerExt;
18use rustc_middle::ty::print::{Print, PrintError, Printer};
19use rustc_middle::ty::{
20    self, FloatTy, GenericArg, GenericArgKind, Instance, IntTy, ReifyReason, Ty, TyCtxt,
21    TypeVisitable, TypeVisitableExt, UintTy,
22};
23use rustc_span::sym;
24
25pub(super) fn mangle<'tcx>(
26    tcx: TyCtxt<'tcx>,
27    instance: Instance<'tcx>,
28    instantiating_crate: Option<CrateNum>,
29    is_exportable: bool,
30) -> String {
31    let def_id = instance.def_id();
32    // FIXME(eddyb) this should ideally not be needed.
33    let args = tcx.normalize_erasing_regions(ty::TypingEnv::fully_monomorphized(), instance.args);
34
35    let prefix = "_R";
36    let mut cx: SymbolMangler<'_> = SymbolMangler {
37        tcx,
38        start_offset: prefix.len(),
39        is_exportable,
40        paths: FxHashMap::default(),
41        types: FxHashMap::default(),
42        consts: FxHashMap::default(),
43        binders: vec![],
44        out: String::from(prefix),
45    };
46
47    // Append `::{shim:...#0}` to shims that can coexist with a non-shim instance.
48    let shim_kind = match instance.def {
49        ty::InstanceKind::ThreadLocalShim(_) => Some("tls"),
50        ty::InstanceKind::VTableShim(_) => Some("vtable"),
51        ty::InstanceKind::ReifyShim(_, None) => Some("reify"),
52        ty::InstanceKind::ReifyShim(_, Some(ReifyReason::FnPtr)) => Some("reify_fnptr"),
53        ty::InstanceKind::ReifyShim(_, Some(ReifyReason::Vtable)) => Some("reify_vtable"),
54
55        // FIXME(async_closures): This shouldn't be needed when we fix
56        // `Instance::ty`/`Instance::def_id`.
57        ty::InstanceKind::ConstructCoroutineInClosureShim { receiver_by_ref: true, .. } => {
58            Some("by_move")
59        }
60        ty::InstanceKind::ConstructCoroutineInClosureShim { receiver_by_ref: false, .. } => {
61            Some("by_ref")
62        }
63        ty::InstanceKind::FutureDropPollShim(_, _, _) => Some("drop"),
64        _ => None,
65    };
66
67    if let ty::InstanceKind::AsyncDropGlue(_, ty) = instance.def {
68        let ty::Coroutine(_, cor_args) = ty.kind() else {
69            bug!();
70        };
71        let drop_ty = cor_args.first().unwrap().expect_ty();
72        cx.print_def_path(def_id, tcx.mk_args(&[GenericArg::from(drop_ty)])).unwrap()
73    } else if let Some(shim_kind) = shim_kind {
74        cx.path_append_ns(|cx| cx.print_def_path(def_id, args), 'S', 0, shim_kind).unwrap()
75    } else {
76        cx.print_def_path(def_id, args).unwrap()
77    };
78    if let Some(instantiating_crate) = instantiating_crate {
79        cx.print_def_path(instantiating_crate.as_def_id(), &[]).unwrap();
80    }
81    std::mem::take(&mut cx.out)
82}
83
84pub fn mangle_internal_symbol<'tcx>(tcx: TyCtxt<'tcx>, item_name: &str) -> String {
85    if item_name == "rust_eh_personality" {
86        // rust_eh_personality must not be renamed as LLVM hard-codes the name
87        return "rust_eh_personality".to_owned();
88    } else if item_name == "__rust_no_alloc_shim_is_unstable" {
89        // Temporary back compat hack to give people the chance to migrate to
90        // include #[rustc_std_internal_symbol].
91        return "__rust_no_alloc_shim_is_unstable".to_owned();
92    }
93
94    let prefix = "_R";
95    let mut cx: SymbolMangler<'_> = SymbolMangler {
96        tcx,
97        start_offset: prefix.len(),
98        is_exportable: false,
99        paths: FxHashMap::default(),
100        types: FxHashMap::default(),
101        consts: FxHashMap::default(),
102        binders: vec![],
103        out: String::from(prefix),
104    };
105
106    cx.path_append_ns(
107        |cx| {
108            cx.push("C");
109            cx.push_disambiguator({
110                let mut hasher = StableHasher::new();
111                // Incorporate the rustc version to ensure #[rustc_std_internal_symbol] functions
112                // get a different symbol name depending on the rustc version.
113                //
114                // RUSTC_FORCE_RUSTC_VERSION is ignored here as otherwise different we would get an
115                // abi incompatibility with the standard library.
116                hasher.write(tcx.sess.cfg_version.as_bytes());
117
118                let hash: Hash64 = hasher.finish();
119                hash.as_u64()
120            });
121            cx.push_ident("__rustc");
122            Ok(())
123        },
124        'v',
125        0,
126        item_name,
127    )
128    .unwrap();
129
130    std::mem::take(&mut cx.out)
131}
132
133pub(super) fn mangle_typeid_for_trait_ref<'tcx>(
134    tcx: TyCtxt<'tcx>,
135    trait_ref: ty::ExistentialTraitRef<'tcx>,
136) -> String {
137    // FIXME(flip1995): See comment in `mangle_typeid_for_fnabi`.
138    let mut cx = SymbolMangler {
139        tcx,
140        start_offset: 0,
141        is_exportable: false,
142        paths: FxHashMap::default(),
143        types: FxHashMap::default(),
144        consts: FxHashMap::default(),
145        binders: vec![],
146        out: String::new(),
147    };
148    cx.print_def_path(trait_ref.def_id, &[]).unwrap();
149    std::mem::take(&mut cx.out)
150}
151
152struct BinderLevel {
153    /// The range of distances from the root of what's
154    /// being printed, to the lifetimes in a binder.
155    /// Specifically, a `BrAnon` lifetime has depth
156    /// `lifetime_depths.start + index`, going away from the
157    /// the root and towards its use site, as the var index increases.
158    /// This is used to flatten rustc's pairing of `BrAnon`
159    /// (intra-binder disambiguation) with a `DebruijnIndex`
160    /// (binder addressing), to "true" de Bruijn indices,
161    /// by subtracting the depth of a certain lifetime, from
162    /// the innermost depth at its use site.
163    lifetime_depths: Range<u32>,
164}
165
166struct SymbolMangler<'tcx> {
167    tcx: TyCtxt<'tcx>,
168    binders: Vec<BinderLevel>,
169    out: String,
170    is_exportable: bool,
171
172    /// The length of the prefix in `out` (e.g. 2 for `_R`).
173    start_offset: usize,
174    /// The values are start positions in `out`, in bytes.
175    paths: FxHashMap<(DefId, &'tcx [GenericArg<'tcx>]), usize>,
176    types: FxHashMap<Ty<'tcx>, usize>,
177    consts: FxHashMap<ty::Const<'tcx>, usize>,
178}
179
180impl<'tcx> SymbolMangler<'tcx> {
181    fn push(&mut self, s: &str) {
182        self.out.push_str(s);
183    }
184
185    /// Push a `_`-terminated base 62 integer, using the format
186    /// specified in the RFC as `<base-62-number>`, that is:
187    /// * `x = 0` is encoded as just the `"_"` terminator
188    /// * `x > 0` is encoded as `x - 1` in base 62, followed by `"_"`,
189    ///   e.g. `1` becomes `"0_"`, `62` becomes `"Z_"`, etc.
190    fn push_integer_62(&mut self, x: u64) {
191        push_integer_62(x, &mut self.out)
192    }
193
194    /// Push a `tag`-prefixed base 62 integer, when larger than `0`, that is:
195    /// * `x = 0` is encoded as `""` (nothing)
196    /// * `x > 0` is encoded as the `tag` followed by `push_integer_62(x - 1)`
197    ///   e.g. `1` becomes `tag + "_"`, `2` becomes `tag + "0_"`, etc.
198    fn push_opt_integer_62(&mut self, tag: &str, x: u64) {
199        if let Some(x) = x.checked_sub(1) {
200            self.push(tag);
201            self.push_integer_62(x);
202        }
203    }
204
205    fn push_disambiguator(&mut self, dis: u64) {
206        self.push_opt_integer_62("s", dis);
207    }
208
209    fn push_ident(&mut self, ident: &str) {
210        push_ident(ident, &mut self.out)
211    }
212
213    fn path_append_ns(
214        &mut self,
215        print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
216        ns: char,
217        disambiguator: u64,
218        name: &str,
219    ) -> Result<(), PrintError> {
220        self.push("N");
221        self.out.push(ns);
222        print_prefix(self)?;
223        self.push_disambiguator(disambiguator);
224        self.push_ident(name);
225        Ok(())
226    }
227
228    fn print_backref(&mut self, i: usize) -> Result<(), PrintError> {
229        self.push("B");
230        self.push_integer_62((i - self.start_offset) as u64);
231        Ok(())
232    }
233
234    fn wrap_binder<T>(
235        &mut self,
236        value: &ty::Binder<'tcx, T>,
237        print_value: impl FnOnce(&mut Self, &T) -> Result<(), PrintError>,
238    ) -> Result<(), PrintError>
239    where
240        T: TypeVisitable<TyCtxt<'tcx>>,
241    {
242        let mut lifetime_depths =
243            self.binders.last().map(|b| b.lifetime_depths.end).map_or(0..0, |i| i..i);
244
245        // FIXME(non-lifetime-binders): What to do here?
246        let lifetimes = value
247            .bound_vars()
248            .iter()
249            .filter(|var| matches!(var, ty::BoundVariableKind::Region(..)))
250            .count() as u32;
251
252        self.push_opt_integer_62("G", lifetimes as u64);
253        lifetime_depths.end += lifetimes;
254
255        self.binders.push(BinderLevel { lifetime_depths });
256        print_value(self, value.as_ref().skip_binder())?;
257        self.binders.pop();
258
259        Ok(())
260    }
261
262    fn print_pat(&mut self, pat: ty::Pattern<'tcx>) -> Result<(), std::fmt::Error> {
263        Ok(match *pat {
264            ty::PatternKind::Range { start, end } => {
265                let consts = [start, end];
266                for ct in consts {
267                    Ty::new_array_with_const_len(self.tcx, self.tcx.types.unit, ct).print(self)?;
268                }
269            }
270            ty::PatternKind::Or(patterns) => {
271                for pat in patterns {
272                    self.print_pat(pat)?;
273                }
274            }
275        })
276    }
277}
278
279impl<'tcx> Printer<'tcx> for SymbolMangler<'tcx> {
280    fn tcx(&self) -> TyCtxt<'tcx> {
281        self.tcx
282    }
283
284    fn print_def_path(
285        &mut self,
286        def_id: DefId,
287        args: &'tcx [GenericArg<'tcx>],
288    ) -> Result<(), PrintError> {
289        if let Some(&i) = self.paths.get(&(def_id, args)) {
290            return self.print_backref(i);
291        }
292        let start = self.out.len();
293
294        self.default_print_def_path(def_id, args)?;
295
296        // Only cache paths that do not refer to an enclosing
297        // binder (which would change depending on context).
298        if !args.iter().any(|k| k.has_escaping_bound_vars()) {
299            self.paths.insert((def_id, args), start);
300        }
301        Ok(())
302    }
303
304    fn print_impl_path(
305        &mut self,
306        impl_def_id: DefId,
307        args: &'tcx [GenericArg<'tcx>],
308    ) -> Result<(), PrintError> {
309        let key = self.tcx.def_key(impl_def_id);
310        let parent_def_id = DefId { index: key.parent.unwrap(), ..impl_def_id };
311
312        let self_ty = self.tcx.type_of(impl_def_id);
313        let impl_trait_ref = self.tcx.impl_trait_ref(impl_def_id);
314        let generics = self.tcx.generics_of(impl_def_id);
315        // We have two cases to worry about here:
316        // 1. We're printing a nested item inside of an impl item, like an inner
317        // function inside of a method. Due to the way that def path printing works,
318        // we'll render this something like `<Ty as Trait>::method::inner_fn`
319        // but we have no substs for this impl since it's not really inheriting
320        // generics from the outer item. We need to use the identity substs, and
321        // to normalize we need to use the correct param-env too.
322        // 2. We're mangling an item with identity substs. This seems to only happen
323        // when generating coverage, since we try to generate coverage for unused
324        // items too, and if something isn't monomorphized then we necessarily don't
325        // have anything to substitute the instance with.
326        // NOTE: We don't support mangling partially substituted but still polymorphic
327        // instances, like `impl<A> Tr<A> for ()` where `A` is substituted w/ `(T,)`.
328        let (typing_env, mut self_ty, mut impl_trait_ref) = if generics.count() > args.len()
329            || &args[..generics.count()]
330                == self
331                    .tcx
332                    .erase_regions(ty::GenericArgs::identity_for_item(self.tcx, impl_def_id))
333                    .as_slice()
334        {
335            (
336                ty::TypingEnv::post_analysis(self.tcx, impl_def_id),
337                self_ty.instantiate_identity(),
338                impl_trait_ref.map(|impl_trait_ref| impl_trait_ref.instantiate_identity()),
339            )
340        } else {
341            assert!(
342                !args.has_non_region_param(),
343                "should not be mangling partially substituted \
344                polymorphic instance: {impl_def_id:?} {args:?}"
345            );
346            (
347                ty::TypingEnv::fully_monomorphized(),
348                self_ty.instantiate(self.tcx, args),
349                impl_trait_ref.map(|impl_trait_ref| impl_trait_ref.instantiate(self.tcx, args)),
350            )
351        };
352
353        match &mut impl_trait_ref {
354            Some(impl_trait_ref) => {
355                assert_eq!(impl_trait_ref.self_ty(), self_ty);
356                *impl_trait_ref = self.tcx.normalize_erasing_regions(typing_env, *impl_trait_ref);
357                self_ty = impl_trait_ref.self_ty();
358            }
359            None => {
360                self_ty = self.tcx.normalize_erasing_regions(typing_env, self_ty);
361            }
362        }
363
364        self.push(match impl_trait_ref {
365            Some(_) => "X",
366            None => "M",
367        });
368
369        // Encode impl generic params if the generic parameters contain non-region parameters
370        // and this isn't an inherent impl.
371        if impl_trait_ref.is_some() && args.iter().any(|a| a.has_non_region_param()) {
372            self.path_generic_args(
373                |this| {
374                    this.path_append_ns(
375                        |cx| cx.print_def_path(parent_def_id, &[]),
376                        'I',
377                        key.disambiguated_data.disambiguator as u64,
378                        "",
379                    )
380                },
381                args,
382            )?;
383        } else {
384            let exported_impl_order = self.tcx.stable_order_of_exportable_impls(impl_def_id.krate);
385            let disambiguator = match self.is_exportable {
386                true => exported_impl_order[&impl_def_id] as u64,
387                false => {
388                    exported_impl_order.len() as u64 + key.disambiguated_data.disambiguator as u64
389                }
390            };
391            self.push_disambiguator(disambiguator);
392            self.print_def_path(parent_def_id, &[])?;
393        }
394
395        self_ty.print(self)?;
396
397        if let Some(trait_ref) = impl_trait_ref {
398            self.print_def_path(trait_ref.def_id, trait_ref.args)?;
399        }
400
401        Ok(())
402    }
403
404    fn print_region(&mut self, region: ty::Region<'_>) -> Result<(), PrintError> {
405        let i = match region.kind() {
406            // Erased lifetimes use the index 0, for a
407            // shorter mangling of `L_`.
408            ty::ReErased => 0,
409
410            // Bound lifetimes use indices starting at 1,
411            // see `BinderLevel` for more details.
412            ty::ReBound(debruijn, ty::BoundRegion { var, kind: ty::BoundRegionKind::Anon }) => {
413                let binder = &self.binders[self.binders.len() - 1 - debruijn.index()];
414                let depth = binder.lifetime_depths.start + var.as_u32();
415
416                1 + (self.binders.last().unwrap().lifetime_depths.end - 1 - depth)
417            }
418
419            _ => bug!("symbol_names: non-erased region `{:?}`", region),
420        };
421        self.push("L");
422        self.push_integer_62(i as u64);
423        Ok(())
424    }
425
426    fn print_type(&mut self, ty: Ty<'tcx>) -> Result<(), PrintError> {
427        // Basic types, never cached (single-character).
428        let basic_type = match ty.kind() {
429            ty::Bool => "b",
430            ty::Char => "c",
431            ty::Str => "e",
432            ty::Tuple(_) if ty.is_unit() => "u",
433            ty::Int(IntTy::I8) => "a",
434            ty::Int(IntTy::I16) => "s",
435            ty::Int(IntTy::I32) => "l",
436            ty::Int(IntTy::I64) => "x",
437            ty::Int(IntTy::I128) => "n",
438            ty::Int(IntTy::Isize) => "i",
439            ty::Uint(UintTy::U8) => "h",
440            ty::Uint(UintTy::U16) => "t",
441            ty::Uint(UintTy::U32) => "m",
442            ty::Uint(UintTy::U64) => "y",
443            ty::Uint(UintTy::U128) => "o",
444            ty::Uint(UintTy::Usize) => "j",
445            ty::Float(FloatTy::F16) => "C3f16",
446            ty::Float(FloatTy::F32) => "f",
447            ty::Float(FloatTy::F64) => "d",
448            ty::Float(FloatTy::F128) => "C4f128",
449            ty::Never => "z",
450
451            // Should only be encountered within the identity-substituted
452            // impl header of an item nested within an impl item.
453            ty::Param(_) => "p",
454
455            ty::Bound(..) | ty::Placeholder(_) | ty::Infer(_) | ty::Error(_) => bug!(),
456
457            _ => "",
458        };
459        if !basic_type.is_empty() {
460            self.push(basic_type);
461            return Ok(());
462        }
463
464        if let Some(&i) = self.types.get(&ty) {
465            return self.print_backref(i);
466        }
467        let start = self.out.len();
468
469        match *ty.kind() {
470            // Basic types, handled above.
471            ty::Bool | ty::Char | ty::Str | ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::Never => {
472                unreachable!()
473            }
474            ty::Tuple(_) if ty.is_unit() => unreachable!(),
475
476            // Placeholders, also handled as part of basic types.
477            ty::Param(_) | ty::Bound(..) | ty::Placeholder(_) | ty::Infer(_) | ty::Error(_) => {
478                unreachable!()
479            }
480
481            ty::Ref(r, ty, mutbl) => {
482                self.push(match mutbl {
483                    hir::Mutability::Not => "R",
484                    hir::Mutability::Mut => "Q",
485                });
486                if !r.is_erased() {
487                    r.print(self)?;
488                }
489                ty.print(self)?;
490            }
491
492            ty::RawPtr(ty, mutbl) => {
493                self.push(match mutbl {
494                    hir::Mutability::Not => "P",
495                    hir::Mutability::Mut => "O",
496                });
497                ty.print(self)?;
498            }
499
500            ty::Pat(ty, pat) => {
501                // HACK: Represent as tuple until we have something better.
502                // HACK: constants are used in arrays, even if the types don't match.
503                self.push("T");
504                ty.print(self)?;
505                self.print_pat(pat)?;
506                self.push("E");
507            }
508
509            ty::Array(ty, len) => {
510                self.push("A");
511                ty.print(self)?;
512                self.print_const(len)?;
513            }
514            ty::Slice(ty) => {
515                self.push("S");
516                ty.print(self)?;
517            }
518
519            ty::Tuple(tys) => {
520                self.push("T");
521                for ty in tys.iter() {
522                    ty.print(self)?;
523                }
524                self.push("E");
525            }
526
527            // Mangle all nominal types as paths.
528            ty::Adt(ty::AdtDef(Interned(&ty::AdtDefData { did: def_id, .. }, _)), args)
529            | ty::FnDef(def_id, args)
530            | ty::Closure(def_id, args)
531            | ty::CoroutineClosure(def_id, args)
532            | ty::Coroutine(def_id, args) => {
533                self.print_def_path(def_id, args)?;
534            }
535
536            // We may still encounter projections here due to the printing
537            // logic sometimes passing identity-substituted impl headers.
538            ty::Alias(ty::Projection, ty::AliasTy { def_id, args, .. }) => {
539                self.print_def_path(def_id, args)?;
540            }
541
542            ty::Foreign(def_id) => {
543                self.print_def_path(def_id, &[])?;
544            }
545
546            ty::FnPtr(sig_tys, hdr) => {
547                let sig = sig_tys.with(hdr);
548                self.push("F");
549                self.wrap_binder(&sig, |cx, sig| {
550                    if sig.safety.is_unsafe() {
551                        cx.push("U");
552                    }
553                    match sig.abi {
554                        ExternAbi::Rust => {}
555                        ExternAbi::C { unwind: false } => cx.push("KC"),
556                        abi => {
557                            cx.push("K");
558                            let name = abi.as_str();
559                            if name.contains('-') {
560                                cx.push_ident(&name.replace('-', "_"));
561                            } else {
562                                cx.push_ident(name);
563                            }
564                        }
565                    }
566                    for &ty in sig.inputs() {
567                        ty.print(cx)?;
568                    }
569                    if sig.c_variadic {
570                        cx.push("v");
571                    }
572                    cx.push("E");
573                    sig.output().print(cx)
574                })?;
575            }
576
577            // FIXME(unsafe_binder):
578            ty::UnsafeBinder(..) => todo!(),
579
580            ty::Dynamic(predicates, r, kind) => {
581                self.push(match kind {
582                    ty::Dyn => "D",
583                    // FIXME(dyn-star): need to update v0 mangling docs
584                    ty::DynStar => "D*",
585                });
586                self.print_dyn_existential(predicates)?;
587                r.print(self)?;
588            }
589
590            ty::Alias(..) => bug!("symbol_names: unexpected alias"),
591            ty::CoroutineWitness(..) => bug!("symbol_names: unexpected `CoroutineWitness`"),
592        }
593
594        // Only cache types that do not refer to an enclosing
595        // binder (which would change depending on context).
596        if !ty.has_escaping_bound_vars() {
597            self.types.insert(ty, start);
598        }
599        Ok(())
600    }
601
602    fn print_dyn_existential(
603        &mut self,
604        predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
605    ) -> Result<(), PrintError> {
606        // Okay, so this is a bit tricky. Imagine we have a trait object like
607        // `dyn for<'a> Foo<'a, Bar = &'a ()>`. When we mangle this, the
608        // output looks really close to the syntax, where the `Bar = &'a ()` bit
609        // is under the same binders (`['a]`) as the `Foo<'a>` bit. However, we
610        // actually desugar these into two separate `ExistentialPredicate`s. We
611        // can't enter/exit the "binder scope" twice though, because then we
612        // would mangle the binders twice. (Also, side note, we merging these
613        // two is kind of difficult, because of potential HRTBs in the Projection
614        // predicate.)
615        //
616        // Also worth mentioning: imagine that we instead had
617        // `dyn for<'a> Foo<'a, Bar = &'a ()> + Send`. In this case, `Send` is
618        // under the same binders as `Foo`. Currently, this doesn't matter,
619        // because only *auto traits* are allowed other than the principal trait
620        // and all auto traits don't have any generics. Two things could
621        // make this not an "okay" mangling:
622        // 1) Instead of mangling only *used*
623        // bound vars, we want to mangle *all* bound vars (`for<'b> Send` is a
624        // valid trait predicate);
625        // 2) We allow multiple "principal" traits in the future, or at least
626        // allow in any form another trait predicate that can take generics.
627        //
628        // Here we assume that predicates have the following structure:
629        // [<Trait> [{<Projection>}]] [{<Auto>}]
630        // Since any predicates after the first one shouldn't change the binders,
631        // just put them all in the binders of the first.
632        self.wrap_binder(&predicates[0], |cx, _| {
633            for predicate in predicates.iter() {
634                // It would be nice to be able to validate bound vars here, but
635                // projections can actually include bound vars from super traits
636                // because of HRTBs (only in the `Self` type). Also, auto traits
637                // could have different bound vars *anyways*.
638                match predicate.as_ref().skip_binder() {
639                    ty::ExistentialPredicate::Trait(trait_ref) => {
640                        // Use a type that can't appear in defaults of type parameters.
641                        let dummy_self = Ty::new_fresh(cx.tcx, 0);
642                        let trait_ref = trait_ref.with_self_ty(cx.tcx, dummy_self);
643                        cx.print_def_path(trait_ref.def_id, trait_ref.args)?;
644                    }
645                    ty::ExistentialPredicate::Projection(projection) => {
646                        let name = cx.tcx.associated_item(projection.def_id).name();
647                        cx.push("p");
648                        cx.push_ident(name.as_str());
649                        match projection.term.kind() {
650                            ty::TermKind::Ty(ty) => ty.print(cx),
651                            ty::TermKind::Const(c) => c.print(cx),
652                        }?;
653                    }
654                    ty::ExistentialPredicate::AutoTrait(def_id) => {
655                        cx.print_def_path(*def_id, &[])?;
656                    }
657                }
658            }
659            Ok(())
660        })?;
661
662        self.push("E");
663        Ok(())
664    }
665
666    fn print_const(&mut self, ct: ty::Const<'tcx>) -> Result<(), PrintError> {
667        // We only mangle a typed value if the const can be evaluated.
668        let cv = match ct.kind() {
669            ty::ConstKind::Value(cv) => cv,
670
671            // Should only be encountered within the identity-substituted
672            // impl header of an item nested within an impl item.
673            ty::ConstKind::Param(_) => {
674                // Never cached (single-character).
675                self.push("p");
676                return Ok(());
677            }
678
679            // We may still encounter unevaluated consts due to the printing
680            // logic sometimes passing identity-substituted impl headers.
681            ty::ConstKind::Unevaluated(ty::UnevaluatedConst { def, args, .. }) => {
682                return self.print_def_path(def, args);
683            }
684
685            ty::ConstKind::Expr(_)
686            | ty::ConstKind::Infer(_)
687            | ty::ConstKind::Bound(..)
688            | ty::ConstKind::Placeholder(_)
689            | ty::ConstKind::Error(_) => bug!(),
690        };
691
692        if let Some(&i) = self.consts.get(&ct) {
693            self.print_backref(i)?;
694            return Ok(());
695        }
696
697        let ty::Value { ty: ct_ty, valtree } = cv;
698        let start = self.out.len();
699
700        match ct_ty.kind() {
701            ty::Uint(_) | ty::Int(_) | ty::Bool | ty::Char => {
702                ct_ty.print(self)?;
703
704                let mut bits = cv
705                    .try_to_bits(self.tcx, ty::TypingEnv::fully_monomorphized())
706                    .expect("expected const to be monomorphic");
707
708                // Negative integer values are mangled using `n` as a "sign prefix".
709                if let ty::Int(ity) = ct_ty.kind() {
710                    let val =
711                        Integer::from_int_ty(&self.tcx, *ity).size().sign_extend(bits) as i128;
712                    if val < 0 {
713                        self.push("n");
714                    }
715                    bits = val.unsigned_abs();
716                }
717
718                let _ = write!(self.out, "{bits:x}_");
719            }
720
721            // Handle `str` as partial support for unsized constants
722            ty::Str => {
723                let tcx = self.tcx();
724                // HACK(jaic1): hide the `str` type behind a reference
725                // for the following transformation from valtree to raw bytes
726                let ref_ty = Ty::new_imm_ref(tcx, tcx.lifetimes.re_static, ct_ty);
727                let cv = ty::Value { ty: ref_ty, valtree };
728                let slice = cv.try_to_raw_bytes(tcx).unwrap_or_else(|| {
729                    bug!("expected to get raw bytes from valtree {:?} for type {:}", valtree, ct_ty)
730                });
731                let s = std::str::from_utf8(slice).expect("non utf8 str from MIR interpreter");
732
733                // "e" for str as a basic type
734                self.push("e");
735
736                // FIXME(eddyb) use a specialized hex-encoding loop.
737                for byte in s.bytes() {
738                    let _ = write!(self.out, "{byte:02x}");
739                }
740
741                self.push("_");
742            }
743
744            // FIXME(valtrees): Remove the special case for `str`
745            // here and fully support unsized constants.
746            ty::Ref(_, _, mutbl) => {
747                self.push(match mutbl {
748                    hir::Mutability::Not => "R",
749                    hir::Mutability::Mut => "Q",
750                });
751
752                let pointee_ty =
753                    ct_ty.builtin_deref(true).expect("tried to dereference on non-ptr type");
754                let dereferenced_const = ty::Const::new_value(self.tcx, valtree, pointee_ty);
755                dereferenced_const.print(self)?;
756            }
757
758            ty::Array(..) | ty::Tuple(..) | ty::Adt(..) | ty::Slice(_) => {
759                let contents = self.tcx.destructure_const(ct);
760                let fields = contents.fields.iter().copied();
761
762                let print_field_list = |this: &mut Self| {
763                    for field in fields.clone() {
764                        field.print(this)?;
765                    }
766                    this.push("E");
767                    Ok(())
768                };
769
770                match *ct_ty.kind() {
771                    ty::Array(..) | ty::Slice(_) => {
772                        self.push("A");
773                        print_field_list(self)?;
774                    }
775                    ty::Tuple(..) => {
776                        self.push("T");
777                        print_field_list(self)?;
778                    }
779                    ty::Adt(def, args) => {
780                        let variant_idx =
781                            contents.variant.expect("destructed const of adt without variant idx");
782                        let variant_def = &def.variant(variant_idx);
783
784                        self.push("V");
785                        self.print_def_path(variant_def.def_id, args)?;
786
787                        match variant_def.ctor_kind() {
788                            Some(CtorKind::Const) => {
789                                self.push("U");
790                            }
791                            Some(CtorKind::Fn) => {
792                                self.push("T");
793                                print_field_list(self)?;
794                            }
795                            None => {
796                                self.push("S");
797                                for (field_def, field) in iter::zip(&variant_def.fields, fields) {
798                                    // HACK(eddyb) this mimics `path_append`,
799                                    // instead of simply using `field_def.ident`,
800                                    // just to be able to handle disambiguators.
801                                    let disambiguated_field =
802                                        self.tcx.def_key(field_def.did).disambiguated_data;
803                                    let field_name = disambiguated_field.data.get_opt_name();
804                                    self.push_disambiguator(
805                                        disambiguated_field.disambiguator as u64,
806                                    );
807                                    self.push_ident(field_name.unwrap().as_str());
808
809                                    field.print(self)?;
810                                }
811                                self.push("E");
812                            }
813                        }
814                    }
815                    _ => unreachable!(),
816                }
817            }
818            _ => {
819                bug!("symbol_names: unsupported constant of type `{}` ({:?})", ct_ty, ct);
820            }
821        }
822
823        // Only cache consts that do not refer to an enclosing
824        // binder (which would change depending on context).
825        if !ct.has_escaping_bound_vars() {
826            self.consts.insert(ct, start);
827        }
828        Ok(())
829    }
830
831    fn path_crate(&mut self, cnum: CrateNum) -> Result<(), PrintError> {
832        self.push("C");
833        if !self.is_exportable {
834            let stable_crate_id = self.tcx.def_path_hash(cnum.as_def_id()).stable_crate_id();
835            self.push_disambiguator(stable_crate_id.as_u64());
836        }
837        let name = self.tcx.crate_name(cnum);
838        self.push_ident(name.as_str());
839        Ok(())
840    }
841
842    fn path_qualified(
843        &mut self,
844        self_ty: Ty<'tcx>,
845        trait_ref: Option<ty::TraitRef<'tcx>>,
846    ) -> Result<(), PrintError> {
847        assert!(trait_ref.is_some());
848        let trait_ref = trait_ref.unwrap();
849
850        self.push("Y");
851        self_ty.print(self)?;
852        self.print_def_path(trait_ref.def_id, trait_ref.args)
853    }
854
855    fn path_append_impl(
856        &mut self,
857        _: impl FnOnce(&mut Self) -> Result<(), PrintError>,
858        _: &DisambiguatedDefPathData,
859        _: Ty<'tcx>,
860        _: Option<ty::TraitRef<'tcx>>,
861    ) -> Result<(), PrintError> {
862        // Inlined into `print_impl_path`
863        unreachable!()
864    }
865
866    fn path_append(
867        &mut self,
868        print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
869        disambiguated_data: &DisambiguatedDefPathData,
870    ) -> Result<(), PrintError> {
871        let ns = match disambiguated_data.data {
872            // Extern block segments can be skipped, names from extern blocks
873            // are effectively living in their parent modules.
874            DefPathData::ForeignMod => return print_prefix(self),
875
876            // Uppercase categories are more stable than lowercase ones.
877            DefPathData::TypeNs(_) => 't',
878            DefPathData::ValueNs(_) => 'v',
879            DefPathData::Closure => 'C',
880            DefPathData::Ctor => 'c',
881            DefPathData::AnonConst => 'k',
882            DefPathData::OpaqueTy => 'i',
883            DefPathData::SyntheticCoroutineBody => 's',
884            DefPathData::NestedStatic => 'n',
885
886            // These should never show up as `path_append` arguments.
887            DefPathData::CrateRoot
888            | DefPathData::Use
889            | DefPathData::GlobalAsm
890            | DefPathData::Impl
891            | DefPathData::MacroNs(_)
892            | DefPathData::LifetimeNs(_)
893            | DefPathData::OpaqueLifetime(_)
894            | DefPathData::AnonAssocTy(..) => {
895                bug!("symbol_names: unexpected DefPathData: {:?}", disambiguated_data.data)
896            }
897        };
898
899        let name = disambiguated_data.data.get_opt_name();
900
901        self.path_append_ns(
902            print_prefix,
903            ns,
904            disambiguated_data.disambiguator as u64,
905            name.unwrap_or(sym::empty).as_str(),
906        )
907    }
908
909    fn path_generic_args(
910        &mut self,
911        print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
912        args: &[GenericArg<'tcx>],
913    ) -> Result<(), PrintError> {
914        // Don't print any regions if they're all erased.
915        let print_regions = args.iter().any(|arg| match arg.kind() {
916            GenericArgKind::Lifetime(r) => !r.is_erased(),
917            _ => false,
918        });
919        let args = args.iter().cloned().filter(|arg| match arg.kind() {
920            GenericArgKind::Lifetime(_) => print_regions,
921            _ => true,
922        });
923
924        if args.clone().next().is_none() {
925            return print_prefix(self);
926        }
927
928        self.push("I");
929        print_prefix(self)?;
930        for arg in args {
931            match arg.kind() {
932                GenericArgKind::Lifetime(lt) => {
933                    lt.print(self)?;
934                }
935                GenericArgKind::Type(ty) => {
936                    ty.print(self)?;
937                }
938                GenericArgKind::Const(c) => {
939                    self.push("K");
940                    c.print(self)?;
941                }
942            }
943        }
944        self.push("E");
945
946        Ok(())
947    }
948}
949/// Push a `_`-terminated base 62 integer, using the format
950/// specified in the RFC as `<base-62-number>`, that is:
951/// * `x = 0` is encoded as just the `"_"` terminator
952/// * `x > 0` is encoded as `x - 1` in base 62, followed by `"_"`,
953///   e.g. `1` becomes `"0_"`, `62` becomes `"Z_"`, etc.
954pub(crate) fn push_integer_62(x: u64, output: &mut String) {
955    if let Some(x) = x.checked_sub(1) {
956        output.push_str(&x.to_base(62));
957    }
958    output.push('_');
959}
960
961pub(crate) fn encode_integer_62(x: u64) -> String {
962    let mut output = String::new();
963    push_integer_62(x, &mut output);
964    output
965}
966
967pub(crate) fn push_ident(ident: &str, output: &mut String) {
968    let mut use_punycode = false;
969    for b in ident.bytes() {
970        match b {
971            b'_' | b'a'..=b'z' | b'A'..=b'Z' | b'0'..=b'9' => {}
972            0x80..=0xff => use_punycode = true,
973            _ => bug!("symbol_names: bad byte {} in ident {:?}", b, ident),
974        }
975    }
976
977    let punycode_string;
978    let ident = if use_punycode {
979        output.push('u');
980
981        // FIXME(eddyb) we should probably roll our own punycode implementation.
982        let mut punycode_bytes = match punycode::encode(ident) {
983            Ok(s) => s.into_bytes(),
984            Err(()) => bug!("symbol_names: punycode encoding failed for ident {:?}", ident),
985        };
986
987        // Replace `-` with `_`.
988        if let Some(c) = punycode_bytes.iter_mut().rfind(|&&mut c| c == b'-') {
989            *c = b'_';
990        }
991
992        // FIXME(eddyb) avoid rechecking UTF-8 validity.
993        punycode_string = String::from_utf8(punycode_bytes).unwrap();
994        &punycode_string
995    } else {
996        ident
997    };
998
999    let _ = write!(output, "{}", ident.len());
1000
1001    // Write a separating `_` if necessary (leading digit or `_`).
1002    if let Some('_' | '0'..='9') = ident.chars().next() {
1003        output.push('_');
1004    }
1005
1006    output.push_str(ident);
1007}
rustc_symbol_mangling/v0.rs

rustc_symbol_mangling/
v0.rs
