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use rustc_data_structures::base_n;
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::intern::Interned;
use rustc_hir as hir;
use rustc_hir::def::CtorKind;
use rustc_hir::def_id::{CrateNum, DefId};
use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
use rustc_middle::ty::layout::IntegerExt;
use rustc_middle::ty::print::{Print, Printer};
use rustc_middle::ty::{
self, EarlyBinder, FloatTy, Instance, IntTy, Ty, TyCtxt, TypeVisitable, TypeVisitableExt,
UintTy,
};
use rustc_middle::ty::{GenericArg, GenericArgKind};
use rustc_span::symbol::kw;
use rustc_target::abi::Integer;
use rustc_target::spec::abi::Abi;
use std::fmt::Write;
use std::iter;
use std::ops::Range;
pub(super) fn mangle<'tcx>(
tcx: TyCtxt<'tcx>,
instance: Instance<'tcx>,
instantiating_crate: Option<CrateNum>,
) -> String {
let def_id = instance.def_id();
// FIXME(eddyb) this should ideally not be needed.
let args = tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), instance.args);
let prefix = "_R";
let mut cx = &mut SymbolMangler {
tcx,
start_offset: prefix.len(),
paths: FxHashMap::default(),
types: FxHashMap::default(),
consts: FxHashMap::default(),
binders: vec![],
out: String::from(prefix),
};
// Append `::{shim:...#0}` to shims that can coexist with a non-shim instance.
let shim_kind = match instance.def {
ty::InstanceDef::ThreadLocalShim(_) => Some("tls"),
ty::InstanceDef::VTableShim(_) => Some("vtable"),
ty::InstanceDef::ReifyShim(_) => Some("reify"),
_ => None,
};
cx = if let Some(shim_kind) = shim_kind {
cx.path_append_ns(|cx| cx.print_def_path(def_id, args), 'S', 0, shim_kind).unwrap()
} else {
cx.print_def_path(def_id, args).unwrap()
};
if let Some(instantiating_crate) = instantiating_crate {
cx = cx.print_def_path(instantiating_crate.as_def_id(), &[]).unwrap();
}
std::mem::take(&mut cx.out)
}
pub(super) fn mangle_typeid_for_trait_ref<'tcx>(
tcx: TyCtxt<'tcx>,
trait_ref: ty::PolyExistentialTraitRef<'tcx>,
) -> String {
// FIXME(flip1995): See comment in `mangle_typeid_for_fnabi`.
let mut cx = &mut SymbolMangler {
tcx,
start_offset: 0,
paths: FxHashMap::default(),
types: FxHashMap::default(),
consts: FxHashMap::default(),
binders: vec![],
out: String::new(),
};
cx = cx.print_def_path(trait_ref.def_id(), &[]).unwrap();
std::mem::take(&mut cx.out)
}
struct BinderLevel {
/// The range of distances from the root of what's
/// being printed, to the lifetimes in a binder.
/// Specifically, a `BrAnon` lifetime has depth
/// `lifetime_depths.start + index`, going away from the
/// the root and towards its use site, as the var index increases.
/// This is used to flatten rustc's pairing of `BrAnon`
/// (intra-binder disambiguation) with a `DebruijnIndex`
/// (binder addressing), to "true" de Bruijn indices,
/// by subtracting the depth of a certain lifetime, from
/// the innermost depth at its use site.
lifetime_depths: Range<u32>,
}
struct SymbolMangler<'tcx> {
tcx: TyCtxt<'tcx>,
binders: Vec<BinderLevel>,
out: String,
/// The length of the prefix in `out` (e.g. 2 for `_R`).
start_offset: usize,
/// The values are start positions in `out`, in bytes.
paths: FxHashMap<(DefId, &'tcx [GenericArg<'tcx>]), usize>,
types: FxHashMap<Ty<'tcx>, usize>,
consts: FxHashMap<ty::Const<'tcx>, usize>,
}
impl<'tcx> SymbolMangler<'tcx> {
fn push(&mut self, s: &str) {
self.out.push_str(s);
}
/// Push a `_`-terminated base 62 integer, using the format
/// specified in the RFC as `<base-62-number>`, that is:
/// * `x = 0` is encoded as just the `"_"` terminator
/// * `x > 0` is encoded as `x - 1` in base 62, followed by `"_"`,
/// e.g. `1` becomes `"0_"`, `62` becomes `"Z_"`, etc.
fn push_integer_62(&mut self, x: u64) {
if let Some(x) = x.checked_sub(1) {
base_n::push_str(x as u128, 62, &mut self.out);
}
self.push("_");
}
/// Push a `tag`-prefixed base 62 integer, when larger than `0`, that is:
/// * `x = 0` is encoded as `""` (nothing)
/// * `x > 0` is encoded as the `tag` followed by `push_integer_62(x - 1)`
/// e.g. `1` becomes `tag + "_"`, `2` becomes `tag + "0_"`, etc.
fn push_opt_integer_62(&mut self, tag: &str, x: u64) {
if let Some(x) = x.checked_sub(1) {
self.push(tag);
self.push_integer_62(x);
}
}
fn push_disambiguator(&mut self, dis: u64) {
self.push_opt_integer_62("s", dis);
}
fn push_ident(&mut self, ident: &str) {
let mut use_punycode = false;
for b in ident.bytes() {
match b {
b'_' | b'a'..=b'z' | b'A'..=b'Z' | b'0'..=b'9' => {}
0x80..=0xff => use_punycode = true,
_ => bug!("symbol_names: bad byte {} in ident {:?}", b, ident),
}
}
let punycode_string;
let ident = if use_punycode {
self.push("u");
// FIXME(eddyb) we should probably roll our own punycode implementation.
let mut punycode_bytes = match punycode::encode(ident) {
Ok(s) => s.into_bytes(),
Err(()) => bug!("symbol_names: punycode encoding failed for ident {:?}", ident),
};
// Replace `-` with `_`.
if let Some(c) = punycode_bytes.iter_mut().rfind(|&&mut c| c == b'-') {
*c = b'_';
}
// FIXME(eddyb) avoid rechecking UTF-8 validity.
punycode_string = String::from_utf8(punycode_bytes).unwrap();
&punycode_string
} else {
ident
};
let _ = write!(self.out, "{}", ident.len());
// Write a separating `_` if necessary (leading digit or `_`).
if let Some('_' | '0'..='9') = ident.chars().next() {
self.push("_");
}
self.push(ident);
}
fn path_append_ns<'a>(
mut self: &'a mut Self,
print_prefix: impl FnOnce(&'a mut Self) -> Result<&'a mut Self, !>,
ns: char,
disambiguator: u64,
name: &str,
) -> Result<&'a mut Self, !> {
self.push("N");
self.out.push(ns);
self = print_prefix(self)?;
self.push_disambiguator(disambiguator as u64);
self.push_ident(name);
Ok(self)
}
fn print_backref(&mut self, i: usize) -> Result<&mut Self, !> {
self.push("B");
self.push_integer_62((i - self.start_offset) as u64);
Ok(self)
}
fn in_binder<'a, T>(
mut self: &'a mut Self,
value: &ty::Binder<'tcx, T>,
print_value: impl FnOnce(&'a mut Self, &T) -> Result<&'a mut Self, !>,
) -> Result<&'a mut Self, !>
where
T: TypeVisitable<TyCtxt<'tcx>>,
{
let mut lifetime_depths =
self.binders.last().map(|b| b.lifetime_depths.end).map_or(0..0, |i| i..i);
// FIXME(non-lifetime-binders): What to do here?
let lifetimes = value
.bound_vars()
.iter()
.filter(|var| matches!(var, ty::BoundVariableKind::Region(..)))
.count() as u32;
self.push_opt_integer_62("G", lifetimes as u64);
lifetime_depths.end += lifetimes;
self.binders.push(BinderLevel { lifetime_depths });
self = print_value(self, value.as_ref().skip_binder())?;
self.binders.pop();
Ok(self)
}
}
impl<'tcx> Printer<'tcx> for &mut SymbolMangler<'tcx> {
type Error = !;
type Path = Self;
type Region = Self;
type Type = Self;
type DynExistential = Self;
type Const = Self;
fn tcx(&self) -> TyCtxt<'tcx> {
self.tcx
}
fn print_def_path(
mut self,
def_id: DefId,
args: &'tcx [GenericArg<'tcx>],
) -> Result<Self::Path, Self::Error> {
if let Some(&i) = self.paths.get(&(def_id, args)) {
return self.print_backref(i);
}
let start = self.out.len();
self = self.default_print_def_path(def_id, args)?;
// Only cache paths that do not refer to an enclosing
// binder (which would change depending on context).
if !args.iter().any(|k| k.has_escaping_bound_vars()) {
self.paths.insert((def_id, args), start);
}
Ok(self)
}
fn print_impl_path(
mut self,
impl_def_id: DefId,
args: &'tcx [GenericArg<'tcx>],
mut self_ty: Ty<'tcx>,
mut impl_trait_ref: Option<ty::TraitRef<'tcx>>,
) -> Result<Self::Path, Self::Error> {
let key = self.tcx.def_key(impl_def_id);
let parent_def_id = DefId { index: key.parent.unwrap(), ..impl_def_id };
let mut param_env = self.tcx.param_env_reveal_all_normalized(impl_def_id);
if !args.is_empty() {
param_env = EarlyBinder::bind(param_env).instantiate(self.tcx, args);
}
match &mut impl_trait_ref {
Some(impl_trait_ref) => {
assert_eq!(impl_trait_ref.self_ty(), self_ty);
*impl_trait_ref = self.tcx.normalize_erasing_regions(param_env, *impl_trait_ref);
self_ty = impl_trait_ref.self_ty();
}
None => {
self_ty = self.tcx.normalize_erasing_regions(param_env, self_ty);
}
}
self.push(match impl_trait_ref {
Some(_) => "X",
None => "M",
});
// Encode impl generic params if the substitutions contain parameters (implying
// polymorphization is enabled) and this isn't an inherent impl.
if impl_trait_ref.is_some() && args.iter().any(|a| a.has_non_region_param()) {
self = self.path_generic_args(
|this| {
this.path_append_ns(
|cx| cx.print_def_path(parent_def_id, &[]),
'I',
key.disambiguated_data.disambiguator as u64,
"",
)
},
args,
)?;
} else {
self.push_disambiguator(key.disambiguated_data.disambiguator as u64);
self = self.print_def_path(parent_def_id, &[])?;
}
self = self_ty.print(self)?;
if let Some(trait_ref) = impl_trait_ref {
self = self.print_def_path(trait_ref.def_id, trait_ref.args)?;
}
Ok(self)
}
fn print_region(self, region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
let i = match *region {
// Erased lifetimes use the index 0, for a
// shorter mangling of `L_`.
ty::ReErased => 0,
// Late-bound lifetimes use indices starting at 1,
// see `BinderLevel` for more details.
ty::ReLateBound(debruijn, ty::BoundRegion { var, kind: ty::BrAnon }) => {
let binder = &self.binders[self.binders.len() - 1 - debruijn.index()];
let depth = binder.lifetime_depths.start + var.as_u32();
1 + (self.binders.last().unwrap().lifetime_depths.end - 1 - depth)
}
_ => bug!("symbol_names: non-erased region `{:?}`", region),
};
self.push("L");
self.push_integer_62(i as u64);
Ok(self)
}
fn print_type(mut self, ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
// Basic types, never cached (single-character).
let basic_type = match ty.kind() {
ty::Bool => "b",
ty::Char => "c",
ty::Str => "e",
ty::Tuple(_) if ty.is_unit() => "u",
ty::Int(IntTy::I8) => "a",
ty::Int(IntTy::I16) => "s",
ty::Int(IntTy::I32) => "l",
ty::Int(IntTy::I64) => "x",
ty::Int(IntTy::I128) => "n",
ty::Int(IntTy::Isize) => "i",
ty::Uint(UintTy::U8) => "h",
ty::Uint(UintTy::U16) => "t",
ty::Uint(UintTy::U32) => "m",
ty::Uint(UintTy::U64) => "y",
ty::Uint(UintTy::U128) => "o",
ty::Uint(UintTy::Usize) => "j",
ty::Float(FloatTy::F32) => "f",
ty::Float(FloatTy::F64) => "d",
ty::Never => "z",
// Placeholders (should be demangled as `_`).
ty::Param(_) | ty::Bound(..) | ty::Placeholder(_) | ty::Infer(_) | ty::Error(_) => "p",
_ => "",
};
if !basic_type.is_empty() {
self.push(basic_type);
return Ok(self);
}
if let Some(&i) = self.types.get(&ty) {
return self.print_backref(i);
}
let start = self.out.len();
match *ty.kind() {
// Basic types, handled above.
ty::Bool | ty::Char | ty::Str | ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::Never => {
unreachable!()
}
ty::Tuple(_) if ty.is_unit() => unreachable!(),
// Placeholders, also handled as part of basic types.
ty::Param(_) | ty::Bound(..) | ty::Placeholder(_) | ty::Infer(_) | ty::Error(_) => {
unreachable!()
}
ty::Ref(r, ty, mutbl) => {
self.push(match mutbl {
hir::Mutability::Not => "R",
hir::Mutability::Mut => "Q",
});
if !r.is_erased() {
self = r.print(self)?;
}
self = ty.print(self)?;
}
ty::RawPtr(mt) => {
self.push(match mt.mutbl {
hir::Mutability::Not => "P",
hir::Mutability::Mut => "O",
});
self = mt.ty.print(self)?;
}
ty::Array(ty, len) => {
self.push("A");
self = ty.print(self)?;
self = self.print_const(len)?;
}
ty::Slice(ty) => {
self.push("S");
self = ty.print(self)?;
}
ty::Tuple(tys) => {
self.push("T");
for ty in tys.iter() {
self = ty.print(self)?;
}
self.push("E");
}
// Mangle all nominal types as paths.
ty::Adt(ty::AdtDef(Interned(&ty::AdtDefData { did: def_id, .. }, _)), args)
| ty::FnDef(def_id, args)
| ty::Alias(ty::Projection | ty::Opaque, ty::AliasTy { def_id, args, .. })
| ty::Closure(def_id, args)
| ty::Generator(def_id, args, _) => {
self = self.print_def_path(def_id, args)?;
}
ty::Foreign(def_id) => {
self = self.print_def_path(def_id, &[])?;
}
ty::FnPtr(sig) => {
self.push("F");
self = self.in_binder(&sig, |mut cx, sig| {
if sig.unsafety == hir::Unsafety::Unsafe {
cx.push("U");
}
match sig.abi {
Abi::Rust => {}
Abi::C { unwind: false } => cx.push("KC"),
abi => {
cx.push("K");
let name = abi.name();
if name.contains('-') {
cx.push_ident(&name.replace('-', "_"));
} else {
cx.push_ident(name);
}
}
}
for &ty in sig.inputs() {
cx = ty.print(cx)?;
}
if sig.c_variadic {
cx.push("v");
}
cx.push("E");
sig.output().print(cx)
})?;
}
ty::Dynamic(predicates, r, kind) => {
self.push(match kind {
ty::Dyn => "D",
// FIXME(dyn-star): need to update v0 mangling docs
ty::DynStar => "D*",
});
self = self.print_dyn_existential(predicates)?;
self = r.print(self)?;
}
ty::Alias(ty::Inherent, _) => bug!("symbol_names: unexpected inherent projection"),
ty::Alias(ty::Weak, _) => bug!("symbol_names: unexpected weak projection"),
ty::GeneratorWitness(..) => bug!("symbol_names: unexpected `GeneratorWitness`"),
}
// Only cache types that do not refer to an enclosing
// binder (which would change depending on context).
if !ty.has_escaping_bound_vars() {
self.types.insert(ty, start);
}
Ok(self)
}
fn print_dyn_existential(
mut self,
predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
) -> Result<Self::DynExistential, Self::Error> {
// Okay, so this is a bit tricky. Imagine we have a trait object like
// `dyn for<'a> Foo<'a, Bar = &'a ()>`. When we mangle this, the
// output looks really close to the syntax, where the `Bar = &'a ()` bit
// is under the same binders (`['a]`) as the `Foo<'a>` bit. However, we
// actually desugar these into two separate `ExistentialPredicate`s. We
// can't enter/exit the "binder scope" twice though, because then we
// would mangle the binders twice. (Also, side note, we merging these
// two is kind of difficult, because of potential HRTBs in the Projection
// predicate.)
//
// Also worth mentioning: imagine that we instead had
// `dyn for<'a> Foo<'a, Bar = &'a ()> + Send`. In this case, `Send` is
// under the same binders as `Foo`. Currently, this doesn't matter,
// because only *auto traits* are allowed other than the principal trait
// and all auto traits don't have any generics. Two things could
// make this not an "okay" mangling:
// 1) Instead of mangling only *used*
// bound vars, we want to mangle *all* bound vars (`for<'b> Send` is a
// valid trait predicate);
// 2) We allow multiple "principal" traits in the future, or at least
// allow in any form another trait predicate that can take generics.
//
// Here we assume that predicates have the following structure:
// [<Trait> [{<Projection>}]] [{<Auto>}]
// Since any predicates after the first one shouldn't change the binders,
// just put them all in the binders of the first.
self = self.in_binder(&predicates[0], |mut cx, _| {
for predicate in predicates.iter() {
// It would be nice to be able to validate bound vars here, but
// projections can actually include bound vars from super traits
// because of HRTBs (only in the `Self` type). Also, auto traits
// could have different bound vars *anyways*.
match predicate.as_ref().skip_binder() {
ty::ExistentialPredicate::Trait(trait_ref) => {
// Use a type that can't appear in defaults of type parameters.
let dummy_self = Ty::new_fresh(cx.tcx, 0);
let trait_ref = trait_ref.with_self_ty(cx.tcx, dummy_self);
cx = cx.print_def_path(trait_ref.def_id, trait_ref.args)?;
}
ty::ExistentialPredicate::Projection(projection) => {
let name = cx.tcx.associated_item(projection.def_id).name;
cx.push("p");
cx.push_ident(name.as_str());
cx = match projection.term.unpack() {
ty::TermKind::Ty(ty) => ty.print(cx),
ty::TermKind::Const(c) => c.print(cx),
}?;
}
ty::ExistentialPredicate::AutoTrait(def_id) => {
cx = cx.print_def_path(*def_id, &[])?;
}
}
}
Ok(cx)
})?;
self.push("E");
Ok(self)
}
fn print_const(mut self, ct: ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
// We only mangle a typed value if the const can be evaluated.
let ct = ct.normalize(self.tcx, ty::ParamEnv::reveal_all());
match ct.kind() {
ty::ConstKind::Value(_) => {}
// Placeholders (should be demangled as `_`).
// NOTE(eddyb) despite `Unevaluated` having a `DefId` (and therefore
// a path), even for it we still need to encode a placeholder, as
// the path could refer back to e.g. an `impl` using the constant.
ty::ConstKind::Unevaluated(_)
| ty::ConstKind::Expr(_)
| ty::ConstKind::Param(_)
| ty::ConstKind::Infer(_)
| ty::ConstKind::Bound(..)
| ty::ConstKind::Placeholder(_)
| ty::ConstKind::Error(_) => {
// Never cached (single-character).
self.push("p");
return Ok(self);
}
}
if let Some(&i) = self.consts.get(&ct) {
return self.print_backref(i);
}
let start = self.out.len();
let ty = ct.ty();
match ty.kind() {
ty::Uint(_) | ty::Int(_) | ty::Bool | ty::Char => {
self = ty.print(self)?;
let mut bits = ct.eval_bits(self.tcx, ty::ParamEnv::reveal_all());
// Negative integer values are mangled using `n` as a "sign prefix".
if let ty::Int(ity) = ty.kind() {
let val =
Integer::from_int_ty(&self.tcx, *ity).size().sign_extend(bits) as i128;
if val < 0 {
self.push("n");
}
bits = val.unsigned_abs();
}
let _ = write!(self.out, "{bits:x}_");
}
// FIXME(valtrees): Remove the special case for `str`
// here and fully support unsized constants.
ty::Ref(_, inner_ty, mutbl) => {
self.push(match mutbl {
hir::Mutability::Not => "R",
hir::Mutability::Mut => "Q",
});
match inner_ty.kind() {
ty::Str if mutbl.is_not() => {
match ct.kind() {
ty::ConstKind::Value(valtree) => {
let slice =
valtree.try_to_raw_bytes(self.tcx(), ty).unwrap_or_else(|| {
bug!(
"expected to get raw bytes from valtree {:?} for type {:}",
valtree, ty
)
});
let s = std::str::from_utf8(slice)
.expect("non utf8 str from MIR interpreter");
self.push("e");
// FIXME(eddyb) use a specialized hex-encoding loop.
for byte in s.bytes() {
let _ = write!(self.out, "{byte:02x}");
}
self.push("_");
}
_ => {
bug!("symbol_names: unsupported `&str` constant: {:?}", ct);
}
}
}
_ => {
let pointee_ty = ct
.ty()
.builtin_deref(true)
.expect("tried to dereference on non-ptr type")
.ty;
// FIXME(const_generics): add an assert that we only do this for valtrees.
let dereferenced_const = self.tcx.mk_ct_from_kind(ct.kind(), pointee_ty);
self = dereferenced_const.print(self)?;
}
}
}
ty::Array(..) | ty::Tuple(..) | ty::Adt(..) | ty::Slice(_) => {
let contents = self.tcx.destructure_const(ct);
let fields = contents.fields.iter().copied();
let print_field_list = |mut this: Self| {
for field in fields.clone() {
this = field.print(this)?;
}
this.push("E");
Ok(this)
};
match *ct.ty().kind() {
ty::Array(..) | ty::Slice(_) => {
self.push("A");
self = print_field_list(self)?;
}
ty::Tuple(..) => {
self.push("T");
self = print_field_list(self)?;
}
ty::Adt(def, args) => {
let variant_idx =
contents.variant.expect("destructed const of adt without variant idx");
let variant_def = &def.variant(variant_idx);
self.push("V");
self = self.print_def_path(variant_def.def_id, args)?;
match variant_def.ctor_kind() {
Some(CtorKind::Const) => {
self.push("U");
}
Some(CtorKind::Fn) => {
self.push("T");
self = print_field_list(self)?;
}
None => {
self.push("S");
for (field_def, field) in iter::zip(&variant_def.fields, fields) {
// HACK(eddyb) this mimics `path_append`,
// instead of simply using `field_def.ident`,
// just to be able to handle disambiguators.
let disambiguated_field =
self.tcx.def_key(field_def.did).disambiguated_data;
let field_name = disambiguated_field.data.get_opt_name();
self.push_disambiguator(
disambiguated_field.disambiguator as u64,
);
self.push_ident(field_name.unwrap_or(kw::Empty).as_str());
self = field.print(self)?;
}
self.push("E");
}
}
}
_ => unreachable!(),
}
}
_ => {
bug!("symbol_names: unsupported constant of type `{}` ({:?})", ct.ty(), ct);
}
}
// Only cache consts that do not refer to an enclosing
// binder (which would change depending on context).
if !ct.has_escaping_bound_vars() {
self.consts.insert(ct, start);
}
Ok(self)
}
fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
self.push("C");
let stable_crate_id = self.tcx.def_path_hash(cnum.as_def_id()).stable_crate_id();
self.push_disambiguator(stable_crate_id.as_u64());
let name = self.tcx.crate_name(cnum);
self.push_ident(name.as_str());
Ok(self)
}
fn path_qualified(
mut self,
self_ty: Ty<'tcx>,
trait_ref: Option<ty::TraitRef<'tcx>>,
) -> Result<Self::Path, Self::Error> {
assert!(trait_ref.is_some());
let trait_ref = trait_ref.unwrap();
self.push("Y");
self = self_ty.print(self)?;
self.print_def_path(trait_ref.def_id, trait_ref.args)
}
fn path_append_impl(
self,
_: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
_: &DisambiguatedDefPathData,
_: Ty<'tcx>,
_: Option<ty::TraitRef<'tcx>>,
) -> Result<Self::Path, Self::Error> {
// Inlined into `print_impl_path`
unreachable!()
}
fn path_append(
self,
print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
disambiguated_data: &DisambiguatedDefPathData,
) -> Result<Self::Path, Self::Error> {
let ns = match disambiguated_data.data {
// Extern block segments can be skipped, names from extern blocks
// are effectively living in their parent modules.
DefPathData::ForeignMod => return print_prefix(self),
// Uppercase categories are more stable than lowercase ones.
DefPathData::TypeNs(_) => 't',
DefPathData::ValueNs(_) => 'v',
DefPathData::ClosureExpr => 'C',
DefPathData::Ctor => 'c',
DefPathData::AnonConst => 'k',
DefPathData::ImplTrait => 'i',
// These should never show up as `path_append` arguments.
DefPathData::CrateRoot
| DefPathData::Use
| DefPathData::GlobalAsm
| DefPathData::Impl
| DefPathData::ImplTraitAssocTy
| DefPathData::MacroNs(_)
| DefPathData::LifetimeNs(_) => {
bug!("symbol_names: unexpected DefPathData: {:?}", disambiguated_data.data)
}
};
let name = disambiguated_data.data.get_opt_name();
self.path_append_ns(
print_prefix,
ns,
disambiguated_data.disambiguator as u64,
name.unwrap_or(kw::Empty).as_str(),
)
}
fn path_generic_args(
mut self,
print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
args: &[GenericArg<'tcx>],
) -> Result<Self::Path, Self::Error> {
// Don't print any regions if they're all erased.
let print_regions = args.iter().any(|arg| match arg.unpack() {
GenericArgKind::Lifetime(r) => !r.is_erased(),
_ => false,
});
let args = args.iter().cloned().filter(|arg| match arg.unpack() {
GenericArgKind::Lifetime(_) => print_regions,
_ => true,
});
if args.clone().next().is_none() {
return print_prefix(self);
}
self.push("I");
self = print_prefix(self)?;
for arg in args {
match arg.unpack() {
GenericArgKind::Lifetime(lt) => {
self = lt.print(self)?;
}
GenericArgKind::Type(ty) => {
self = ty.print(self)?;
}
GenericArgKind::Const(c) => {
self.push("K");
self = c.print(self)?;
}
}
}
self.push("E");
Ok(self)
}
}