rustc_symbol_mangling/
v0.rs

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

rustc_symbol_mangling/
v0.rs
