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 p: V0SymbolMangler<'_> = V0SymbolMangler {
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        p.print_def_path(def_id, tcx.mk_args(&[GenericArg::from(drop_ty)])).unwrap()
73    } else if let Some(shim_kind) = shim_kind {
74        p.path_append_ns(|p| p.print_def_path(def_id, args), 'S', 0, shim_kind).unwrap()
75    } else {
76        p.print_def_path(def_id, args).unwrap()
77    };
78    if let Some(instantiating_crate) = instantiating_crate {
79        p.print_def_path(instantiating_crate.as_def_id(), &[]).unwrap();
80    }
81    std::mem::take(&mut p.out)
82}
83
84pub fn mangle_internal_symbol<'tcx>(tcx: TyCtxt<'tcx>, item_name: &str) -> String {
85    match item_name {
86        // rust_eh_personality must not be renamed as LLVM hard-codes the name
87        "rust_eh_personality" => return item_name.to_owned(),
88        // Apple availability symbols need to not be mangled to be usable by
89        // C/Objective-C code.
90        "__isPlatformVersionAtLeast" | "__isOSVersionAtLeast" => return item_name.to_owned(),
91        _ => {}
92    }
93
94    let prefix = "_R";
95    let mut p: V0SymbolMangler<'_> = V0SymbolMangler {
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    p.path_append_ns(
107        |p| {
108            p.push("C");
109            p.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            p.push_ident("__rustc");
122            Ok(())
123        },
124        'v',
125        0,
126        item_name,
127    )
128    .unwrap();
129
130    std::mem::take(&mut p.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 p = V0SymbolMangler {
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    p.print_def_path(trait_ref.def_id, &[]).unwrap();
149    std::mem::take(&mut p.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 V0SymbolMangler<'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> V0SymbolMangler<'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                self.push("R");
266                self.print_const(start)?;
267                self.print_const(end)?;
268            }
269            ty::PatternKind::Or(patterns) => {
270                self.push("O");
271                for pat in patterns {
272                    self.print_pat(pat)?;
273                }
274                self.push("E");
275            }
276        })
277    }
278}
279
280impl<'tcx> Printer<'tcx> for V0SymbolMangler<'tcx> {
281    fn tcx(&self) -> TyCtxt<'tcx> {
282        self.tcx
283    }
284
285    fn print_def_path(
286        &mut self,
287        def_id: DefId,
288        args: &'tcx [GenericArg<'tcx>],
289    ) -> Result<(), PrintError> {
290        if let Some(&i) = self.paths.get(&(def_id, args)) {
291            return self.print_backref(i);
292        }
293        let start = self.out.len();
294
295        self.default_print_def_path(def_id, args)?;
296
297        // Only cache paths that do not refer to an enclosing
298        // binder (which would change depending on context).
299        if !args.iter().any(|k| k.has_escaping_bound_vars()) {
300            self.paths.insert((def_id, args), start);
301        }
302        Ok(())
303    }
304
305    fn print_impl_path(
306        &mut self,
307        impl_def_id: DefId,
308        args: &'tcx [GenericArg<'tcx>],
309    ) -> Result<(), PrintError> {
310        let key = self.tcx.def_key(impl_def_id);
311        let parent_def_id = DefId { index: key.parent.unwrap(), ..impl_def_id };
312
313        let self_ty = self.tcx.type_of(impl_def_id);
314        let impl_trait_ref = self.tcx.impl_trait_ref(impl_def_id);
315        let generics = self.tcx.generics_of(impl_def_id);
316        // We have two cases to worry about here:
317        // 1. We're printing a nested item inside of an impl item, like an inner
318        // function inside of a method. Due to the way that def path printing works,
319        // we'll render this something like `<Ty as Trait>::method::inner_fn`
320        // but we have no substs for this impl since it's not really inheriting
321        // generics from the outer item. We need to use the identity substs, and
322        // to normalize we need to use the correct param-env too.
323        // 2. We're mangling an item with identity substs. This seems to only happen
324        // when generating coverage, since we try to generate coverage for unused
325        // items too, and if something isn't monomorphized then we necessarily don't
326        // have anything to substitute the instance with.
327        // NOTE: We don't support mangling partially substituted but still polymorphic
328        // instances, like `impl<A> Tr<A> for ()` where `A` is substituted w/ `(T,)`.
329        let (typing_env, mut self_ty, mut impl_trait_ref) = if generics.count() > args.len()
330            || &args[..generics.count()]
331                == self
332                    .tcx
333                    .erase_and_anonymize_regions(ty::GenericArgs::identity_for_item(
334                        self.tcx,
335                        impl_def_id,
336                    ))
337                    .as_slice()
338        {
339            (
340                ty::TypingEnv::post_analysis(self.tcx, impl_def_id),
341                self_ty.instantiate_identity(),
342                impl_trait_ref.map(|impl_trait_ref| impl_trait_ref.instantiate_identity()),
343            )
344        } else {
345            assert!(
346                !args.has_non_region_param() && !args.has_free_regions(),
347                "should not be mangling partially substituted \
348                polymorphic instance: {impl_def_id:?} {args:?}"
349            );
350            (
351                ty::TypingEnv::fully_monomorphized(),
352                self_ty.instantiate(self.tcx, args),
353                impl_trait_ref.map(|impl_trait_ref| impl_trait_ref.instantiate(self.tcx, args)),
354            )
355        };
356
357        match &mut impl_trait_ref {
358            Some(impl_trait_ref) => {
359                assert_eq!(impl_trait_ref.self_ty(), self_ty);
360                *impl_trait_ref = self.tcx.normalize_erasing_regions(typing_env, *impl_trait_ref);
361                self_ty = impl_trait_ref.self_ty();
362            }
363            None => {
364                self_ty = self.tcx.normalize_erasing_regions(typing_env, self_ty);
365            }
366        }
367
368        self.push(match impl_trait_ref {
369            Some(_) => "X",
370            None => "M",
371        });
372
373        // Encode impl generic params if the generic parameters contain non-region parameters
374        // and this isn't an inherent impl.
375        if impl_trait_ref.is_some() && args.iter().any(|a| a.has_non_region_param()) {
376            self.print_path_with_generic_args(
377                |this| {
378                    this.path_append_ns(
379                        |p| p.print_def_path(parent_def_id, &[]),
380                        'I',
381                        key.disambiguated_data.disambiguator as u64,
382                        "",
383                    )
384                },
385                args,
386            )?;
387        } else {
388            let exported_impl_order = self.tcx.stable_order_of_exportable_impls(impl_def_id.krate);
389            let disambiguator = match self.is_exportable {
390                true => exported_impl_order[&impl_def_id] as u64,
391                false => {
392                    exported_impl_order.len() as u64 + key.disambiguated_data.disambiguator as u64
393                }
394            };
395            self.push_disambiguator(disambiguator);
396            self.print_def_path(parent_def_id, &[])?;
397        }
398
399        self_ty.print(self)?;
400
401        if let Some(trait_ref) = impl_trait_ref {
402            self.print_def_path(trait_ref.def_id, trait_ref.args)?;
403        }
404
405        Ok(())
406    }
407
408    fn print_region(&mut self, region: ty::Region<'_>) -> Result<(), PrintError> {
409        let i = match region.kind() {
410            // Erased lifetimes use the index 0, for a
411            // shorter mangling of `L_`.
412            ty::ReErased => 0,
413
414            // Bound lifetimes use indices starting at 1,
415            // see `BinderLevel` for more details.
416            ty::ReBound(debruijn, ty::BoundRegion { var, kind: ty::BoundRegionKind::Anon }) => {
417                let binder = &self.binders[self.binders.len() - 1 - debruijn.index()];
418                let depth = binder.lifetime_depths.start + var.as_u32();
419
420                1 + (self.binders.last().unwrap().lifetime_depths.end - 1 - depth)
421            }
422
423            _ => bug!("symbol_names: non-erased region `{:?}`", region),
424        };
425        self.push("L");
426        self.push_integer_62(i as u64);
427        Ok(())
428    }
429
430    fn print_type(&mut self, ty: Ty<'tcx>) -> Result<(), PrintError> {
431        // Basic types, never cached (single-character).
432        let basic_type = match ty.kind() {
433            ty::Bool => "b",
434            ty::Char => "c",
435            ty::Str => "e",
436            ty::Int(IntTy::I8) => "a",
437            ty::Int(IntTy::I16) => "s",
438            ty::Int(IntTy::I32) => "l",
439            ty::Int(IntTy::I64) => "x",
440            ty::Int(IntTy::I128) => "n",
441            ty::Int(IntTy::Isize) => "i",
442            ty::Uint(UintTy::U8) => "h",
443            ty::Uint(UintTy::U16) => "t",
444            ty::Uint(UintTy::U32) => "m",
445            ty::Uint(UintTy::U64) => "y",
446            ty::Uint(UintTy::U128) => "o",
447            ty::Uint(UintTy::Usize) => "j",
448            ty::Float(FloatTy::F16) => "C3f16",
449            ty::Float(FloatTy::F32) => "f",
450            ty::Float(FloatTy::F64) => "d",
451            ty::Float(FloatTy::F128) => "C4f128",
452            ty::Never => "z",
453
454            ty::Tuple(_) if ty.is_unit() => "u",
455
456            // Should only be encountered within the identity-substituted
457            // impl header of an item nested within an impl item.
458            ty::Param(_) => "p",
459
460            _ => "",
461        };
462        if !basic_type.is_empty() {
463            self.push(basic_type);
464            return Ok(());
465        }
466
467        if let Some(&i) = self.types.get(&ty) {
468            return self.print_backref(i);
469        }
470        let start = self.out.len();
471
472        match *ty.kind() {
473            // Basic types, handled above.
474            ty::Bool | ty::Char | ty::Str | ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::Never => {
475                unreachable!()
476            }
477            ty::Tuple(_) if ty.is_unit() => unreachable!(),
478            ty::Param(_) => unreachable!(),
479
480            ty::Bound(..) | ty::Placeholder(_) | ty::Infer(_) | ty::Error(_) => bug!(),
481
482            ty::Ref(r, ty, mutbl) => {
483                self.push(match mutbl {
484                    hir::Mutability::Not => "R",
485                    hir::Mutability::Mut => "Q",
486                });
487                if !r.is_erased() {
488                    r.print(self)?;
489                }
490                ty.print(self)?;
491            }
492
493            ty::RawPtr(ty, mutbl) => {
494                self.push(match mutbl {
495                    hir::Mutability::Not => "P",
496                    hir::Mutability::Mut => "O",
497                });
498                ty.print(self)?;
499            }
500
501            ty::Pat(ty, pat) => {
502                self.push("W");
503                ty.print(self)?;
504                self.print_pat(pat)?;
505            }
506
507            ty::Array(ty, len) => {
508                self.push("A");
509                ty.print(self)?;
510                self.print_const(len)?;
511            }
512            ty::Slice(ty) => {
513                self.push("S");
514                ty.print(self)?;
515            }
516
517            ty::Tuple(tys) => {
518                self.push("T");
519                for ty in tys.iter() {
520                    ty.print(self)?;
521                }
522                self.push("E");
523            }
524
525            // Mangle all nominal types as paths.
526            ty::Adt(ty::AdtDef(Interned(&ty::AdtDefData { did: def_id, .. }, _)), args)
527            | ty::FnDef(def_id, args)
528            | ty::Closure(def_id, args)
529            | ty::CoroutineClosure(def_id, args)
530            | ty::Coroutine(def_id, args) => {
531                self.print_def_path(def_id, args)?;
532            }
533
534            // We may still encounter projections here due to the printing
535            // logic sometimes passing identity-substituted impl headers.
536            ty::Alias(ty::Projection, ty::AliasTy { def_id, args, .. }) => {
537                self.print_def_path(def_id, args)?;
538            }
539
540            ty::Foreign(def_id) => {
541                self.print_def_path(def_id, &[])?;
542            }
543
544            ty::FnPtr(sig_tys, hdr) => {
545                let sig = sig_tys.with(hdr);
546                self.push("F");
547                self.wrap_binder(&sig, |p, sig| {
548                    if sig.safety.is_unsafe() {
549                        p.push("U");
550                    }
551                    match sig.abi {
552                        ExternAbi::Rust => {}
553                        ExternAbi::C { unwind: false } => p.push("KC"),
554                        abi => {
555                            p.push("K");
556                            let name = abi.as_str();
557                            if name.contains('-') {
558                                p.push_ident(&name.replace('-', "_"));
559                            } else {
560                                p.push_ident(name);
561                            }
562                        }
563                    }
564                    for &ty in sig.inputs() {
565                        ty.print(p)?;
566                    }
567                    if sig.c_variadic {
568                        p.push("v");
569                    }
570                    p.push("E");
571                    sig.output().print(p)
572                })?;
573            }
574
575            // FIXME(unsafe_binder):
576            ty::UnsafeBinder(..) => todo!(),
577
578            ty::Dynamic(predicates, r) => {
579                self.push("D");
580                self.print_dyn_existential(predicates)?;
581                r.print(self)?;
582            }
583
584            ty::Alias(..) => bug!("symbol_names: unexpected alias"),
585            ty::CoroutineWitness(..) => bug!("symbol_names: unexpected `CoroutineWitness`"),
586        }
587
588        // Only cache types that do not refer to an enclosing
589        // binder (which would change depending on context).
590        if !ty.has_escaping_bound_vars() {
591            self.types.insert(ty, start);
592        }
593        Ok(())
594    }
595
596    fn print_dyn_existential(
597        &mut self,
598        predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
599    ) -> Result<(), PrintError> {
600        // Okay, so this is a bit tricky. Imagine we have a trait object like
601        // `dyn for<'a> Foo<'a, Bar = &'a ()>`. When we mangle this, the
602        // output looks really close to the syntax, where the `Bar = &'a ()` bit
603        // is under the same binders (`['a]`) as the `Foo<'a>` bit. However, we
604        // actually desugar these into two separate `ExistentialPredicate`s. We
605        // can't enter/exit the "binder scope" twice though, because then we
606        // would mangle the binders twice. (Also, side note, we merging these
607        // two is kind of difficult, because of potential HRTBs in the Projection
608        // predicate.)
609        //
610        // Also worth mentioning: imagine that we instead had
611        // `dyn for<'a> Foo<'a, Bar = &'a ()> + Send`. In this case, `Send` is
612        // under the same binders as `Foo`. Currently, this doesn't matter,
613        // because only *auto traits* are allowed other than the principal trait
614        // and all auto traits don't have any generics. Two things could
615        // make this not an "okay" mangling:
616        // 1) Instead of mangling only *used*
617        // bound vars, we want to mangle *all* bound vars (`for<'b> Send` is a
618        // valid trait predicate);
619        // 2) We allow multiple "principal" traits in the future, or at least
620        // allow in any form another trait predicate that can take generics.
621        //
622        // Here we assume that predicates have the following structure:
623        // [<Trait> [{<Projection>}]] [{<Auto>}]
624        // Since any predicates after the first one shouldn't change the binders,
625        // just put them all in the binders of the first.
626        self.wrap_binder(&predicates[0], |p, _| {
627            for predicate in predicates.iter() {
628                // It would be nice to be able to validate bound vars here, but
629                // projections can actually include bound vars from super traits
630                // because of HRTBs (only in the `Self` type). Also, auto traits
631                // could have different bound vars *anyways*.
632                match predicate.as_ref().skip_binder() {
633                    ty::ExistentialPredicate::Trait(trait_ref) => {
634                        // Use a type that can't appear in defaults of type parameters.
635                        let dummy_self = Ty::new_fresh(p.tcx, 0);
636                        let trait_ref = trait_ref.with_self_ty(p.tcx, dummy_self);
637                        p.print_def_path(trait_ref.def_id, trait_ref.args)?;
638                    }
639                    ty::ExistentialPredicate::Projection(projection) => {
640                        let name = p.tcx.associated_item(projection.def_id).name();
641                        p.push("p");
642                        p.push_ident(name.as_str());
643                        match projection.term.kind() {
644                            ty::TermKind::Ty(ty) => ty.print(p),
645                            ty::TermKind::Const(c) => c.print(p),
646                        }?;
647                    }
648                    ty::ExistentialPredicate::AutoTrait(def_id) => {
649                        p.print_def_path(*def_id, &[])?;
650                    }
651                }
652            }
653            Ok(())
654        })?;
655
656        self.push("E");
657        Ok(())
658    }
659
660    fn print_const(&mut self, ct: ty::Const<'tcx>) -> Result<(), PrintError> {
661        // We only mangle a typed value if the const can be evaluated.
662        let cv = match ct.kind() {
663            ty::ConstKind::Value(cv) => cv,
664
665            // Should only be encountered within the identity-substituted
666            // impl header of an item nested within an impl item.
667            ty::ConstKind::Param(_) => {
668                // Never cached (single-character).
669                self.push("p");
670                return Ok(());
671            }
672
673            // We may still encounter unevaluated consts due to the printing
674            // logic sometimes passing identity-substituted impl headers.
675            ty::ConstKind::Unevaluated(ty::UnevaluatedConst { def, args, .. }) => {
676                return self.print_def_path(def, args);
677            }
678
679            ty::ConstKind::Expr(_)
680            | ty::ConstKind::Infer(_)
681            | ty::ConstKind::Bound(..)
682            | ty::ConstKind::Placeholder(_)
683            | ty::ConstKind::Error(_) => bug!(),
684        };
685
686        if let Some(&i) = self.consts.get(&ct) {
687            self.print_backref(i)?;
688            return Ok(());
689        }
690
691        let ty::Value { ty: ct_ty, valtree } = cv;
692        let start = self.out.len();
693
694        match ct_ty.kind() {
695            ty::Uint(_) | ty::Int(_) | ty::Bool | ty::Char => {
696                ct_ty.print(self)?;
697
698                let mut bits = cv
699                    .try_to_bits(self.tcx, ty::TypingEnv::fully_monomorphized())
700                    .expect("expected const to be monomorphic");
701
702                // Negative integer values are mangled using `n` as a "sign prefix".
703                if let ty::Int(ity) = ct_ty.kind() {
704                    let val =
705                        Integer::from_int_ty(&self.tcx, *ity).size().sign_extend(bits) as i128;
706                    if val < 0 {
707                        self.push("n");
708                    }
709                    bits = val.unsigned_abs();
710                }
711
712                let _ = write!(self.out, "{bits:x}_");
713            }
714
715            // Handle `str` as partial support for unsized constants
716            ty::Str => {
717                let tcx = self.tcx();
718                // HACK(jaic1): hide the `str` type behind a reference
719                // for the following transformation from valtree to raw bytes
720                let ref_ty = Ty::new_imm_ref(tcx, tcx.lifetimes.re_static, ct_ty);
721                let cv = ty::Value { ty: ref_ty, valtree };
722                let slice = cv.try_to_raw_bytes(tcx).unwrap_or_else(|| {
723                    bug!("expected to get raw bytes from valtree {:?} for type {:}", valtree, ct_ty)
724                });
725                let s = std::str::from_utf8(slice).expect("non utf8 str from MIR interpreter");
726
727                // "e" for str as a basic type
728                self.push("e");
729
730                // FIXME(eddyb) use a specialized hex-encoding loop.
731                for byte in s.bytes() {
732                    let _ = write!(self.out, "{byte:02x}");
733                }
734
735                self.push("_");
736            }
737
738            // FIXME(valtrees): Remove the special case for `str`
739            // here and fully support unsized constants.
740            ty::Ref(_, _, mutbl) => {
741                self.push(match mutbl {
742                    hir::Mutability::Not => "R",
743                    hir::Mutability::Mut => "Q",
744                });
745
746                let pointee_ty =
747                    ct_ty.builtin_deref(true).expect("tried to dereference on non-ptr type");
748                let dereferenced_const = ty::Const::new_value(self.tcx, valtree, pointee_ty);
749                dereferenced_const.print(self)?;
750            }
751
752            ty::Array(..) | ty::Tuple(..) | ty::Adt(..) | ty::Slice(_) => {
753                let contents = self.tcx.destructure_const(ct);
754                let fields = contents.fields.iter().copied();
755
756                let print_field_list = |this: &mut Self| {
757                    for field in fields.clone() {
758                        field.print(this)?;
759                    }
760                    this.push("E");
761                    Ok(())
762                };
763
764                match *ct_ty.kind() {
765                    ty::Array(..) | ty::Slice(_) => {
766                        self.push("A");
767                        print_field_list(self)?;
768                    }
769                    ty::Tuple(..) => {
770                        self.push("T");
771                        print_field_list(self)?;
772                    }
773                    ty::Adt(def, args) => {
774                        let variant_idx =
775                            contents.variant.expect("destructed const of adt without variant idx");
776                        let variant_def = &def.variant(variant_idx);
777
778                        self.push("V");
779                        self.print_def_path(variant_def.def_id, args)?;
780
781                        match variant_def.ctor_kind() {
782                            Some(CtorKind::Const) => {
783                                self.push("U");
784                            }
785                            Some(CtorKind::Fn) => {
786                                self.push("T");
787                                print_field_list(self)?;
788                            }
789                            None => {
790                                self.push("S");
791                                for (field_def, field) in iter::zip(&variant_def.fields, fields) {
792                                    // HACK(eddyb) this mimics `print_path_with_simple`,
793                                    // instead of simply using `field_def.ident`,
794                                    // just to be able to handle disambiguators.
795                                    let disambiguated_field =
796                                        self.tcx.def_key(field_def.did).disambiguated_data;
797                                    let field_name = disambiguated_field.data.get_opt_name();
798                                    self.push_disambiguator(
799                                        disambiguated_field.disambiguator as u64,
800                                    );
801                                    self.push_ident(field_name.unwrap().as_str());
802
803                                    field.print(self)?;
804                                }
805                                self.push("E");
806                            }
807                        }
808                    }
809                    _ => unreachable!(),
810                }
811            }
812            _ => {
813                bug!("symbol_names: unsupported constant of type `{}` ({:?})", ct_ty, ct);
814            }
815        }
816
817        // Only cache consts that do not refer to an enclosing
818        // binder (which would change depending on context).
819        if !ct.has_escaping_bound_vars() {
820            self.consts.insert(ct, start);
821        }
822        Ok(())
823    }
824
825    fn print_crate_name(&mut self, cnum: CrateNum) -> Result<(), PrintError> {
826        self.push("C");
827        if !self.is_exportable {
828            let stable_crate_id = self.tcx.def_path_hash(cnum.as_def_id()).stable_crate_id();
829            self.push_disambiguator(stable_crate_id.as_u64());
830        }
831        let name = self.tcx.crate_name(cnum);
832        self.push_ident(name.as_str());
833        Ok(())
834    }
835
836    fn print_path_with_qualified(
837        &mut self,
838        self_ty: Ty<'tcx>,
839        trait_ref: Option<ty::TraitRef<'tcx>>,
840    ) -> Result<(), PrintError> {
841        assert!(trait_ref.is_some());
842        let trait_ref = trait_ref.unwrap();
843
844        self.push("Y");
845        self_ty.print(self)?;
846        self.print_def_path(trait_ref.def_id, trait_ref.args)
847    }
848
849    fn print_path_with_impl(
850        &mut self,
851        _: impl FnOnce(&mut Self) -> Result<(), PrintError>,
852        _: Ty<'tcx>,
853        _: Option<ty::TraitRef<'tcx>>,
854    ) -> Result<(), PrintError> {
855        // Inlined into `print_impl_path`
856        unreachable!()
857    }
858
859    fn print_path_with_simple(
860        &mut self,
861        print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
862        disambiguated_data: &DisambiguatedDefPathData,
863    ) -> Result<(), PrintError> {
864        let ns = match disambiguated_data.data {
865            // Extern block segments can be skipped, names from extern blocks
866            // are effectively living in their parent modules.
867            DefPathData::ForeignMod => return print_prefix(self),
868
869            // Uppercase categories are more stable than lowercase ones.
870            DefPathData::TypeNs(_) => 't',
871            DefPathData::ValueNs(_) => 'v',
872            DefPathData::Closure => 'C',
873            DefPathData::Ctor => 'c',
874            DefPathData::AnonConst => 'k',
875            DefPathData::OpaqueTy => 'i',
876            DefPathData::SyntheticCoroutineBody => 's',
877            DefPathData::NestedStatic => 'n',
878
879            // These should never show up as `print_path_with_simple` arguments.
880            DefPathData::CrateRoot
881            | DefPathData::Use
882            | DefPathData::GlobalAsm
883            | DefPathData::Impl
884            | DefPathData::MacroNs(_)
885            | DefPathData::LifetimeNs(_)
886            | DefPathData::OpaqueLifetime(_)
887            | DefPathData::AnonAssocTy(..) => {
888                bug!("symbol_names: unexpected DefPathData: {:?}", disambiguated_data.data)
889            }
890        };
891
892        let name = disambiguated_data.data.get_opt_name();
893
894        self.path_append_ns(
895            print_prefix,
896            ns,
897            disambiguated_data.disambiguator as u64,
898            name.unwrap_or(sym::empty).as_str(),
899        )
900    }
901
902    fn print_path_with_generic_args(
903        &mut self,
904        print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
905        args: &[GenericArg<'tcx>],
906    ) -> Result<(), PrintError> {
907        // Don't print any regions if they're all erased.
908        let print_regions = args.iter().any(|arg| match arg.kind() {
909            GenericArgKind::Lifetime(r) => !r.is_erased(),
910            _ => false,
911        });
912        let args = args.iter().cloned().filter(|arg| match arg.kind() {
913            GenericArgKind::Lifetime(_) => print_regions,
914            _ => true,
915        });
916
917        if args.clone().next().is_none() {
918            return print_prefix(self);
919        }
920
921        self.push("I");
922        print_prefix(self)?;
923        for arg in args {
924            match arg.kind() {
925                GenericArgKind::Lifetime(lt) => {
926                    lt.print(self)?;
927                }
928                GenericArgKind::Type(ty) => {
929                    ty.print(self)?;
930                }
931                GenericArgKind::Const(c) => {
932                    self.push("K");
933                    c.print(self)?;
934                }
935            }
936        }
937        self.push("E");
938
939        Ok(())
940    }
941}
942/// Push a `_`-terminated base 62 integer, using the format
943/// specified in the RFC as `<base-62-number>`, that is:
944/// * `x = 0` is encoded as just the `"_"` terminator
945/// * `x > 0` is encoded as `x - 1` in base 62, followed by `"_"`,
946///   e.g. `1` becomes `"0_"`, `62` becomes `"Z_"`, etc.
947pub(crate) fn push_integer_62(x: u64, output: &mut String) {
948    if let Some(x) = x.checked_sub(1) {
949        output.push_str(&x.to_base(62));
950    }
951    output.push('_');
952}
953
954pub(crate) fn encode_integer_62(x: u64) -> String {
955    let mut output = String::new();
956    push_integer_62(x, &mut output);
957    output
958}
959
960pub(crate) fn push_ident(ident: &str, output: &mut String) {
961    let mut use_punycode = false;
962    for b in ident.bytes() {
963        match b {
964            b'_' | b'a'..=b'z' | b'A'..=b'Z' | b'0'..=b'9' => {}
965            0x80..=0xff => use_punycode = true,
966            _ => bug!("symbol_names: bad byte {} in ident {:?}", b, ident),
967        }
968    }
969
970    let punycode_string;
971    let ident = if use_punycode {
972        output.push('u');
973
974        // FIXME(eddyb) we should probably roll our own punycode implementation.
975        let mut punycode_bytes = match punycode::encode(ident) {
976            Ok(s) => s.into_bytes(),
977            Err(()) => bug!("symbol_names: punycode encoding failed for ident {:?}", ident),
978        };
979
980        // Replace `-` with `_`.
981        if let Some(c) = punycode_bytes.iter_mut().rfind(|&&mut c| c == b'-') {
982            *c = b'_';
983        }
984
985        // FIXME(eddyb) avoid rechecking UTF-8 validity.
986        punycode_string = String::from_utf8(punycode_bytes).unwrap();
987        &punycode_string
988    } else {
989        ident
990    };
991
992    let _ = write!(output, "{}", ident.len());
993
994    // Write a separating `_` if necessary (leading digit or `_`).
995    if let Some('_' | '0'..='9') = ident.chars().next() {
996        output.push('_');
997    }
998
999    output.push_str(ident);
1000}
rustc_symbol_mangling/v0.rs

rustc_symbol_mangling/
v0.rs
