2020-01-30 14:28:16 -06:00
|
|
|
//! Check whether a type has (potentially) non-trivial drop glue.
|
|
|
|
|
2020-03-29 10:19:48 -05:00
|
|
|
use rustc_data_structures::fx::FxHashSet;
|
|
|
|
use rustc_hir::def_id::DefId;
|
2020-03-29 09:41:09 -05:00
|
|
|
use rustc_middle::ty::subst::Subst;
|
2021-09-21 04:06:19 -05:00
|
|
|
use rustc_middle::ty::subst::SubstsRef;
|
2020-03-29 09:41:09 -05:00
|
|
|
use rustc_middle::ty::util::{needs_drop_components, AlwaysRequiresDrop};
|
|
|
|
use rustc_middle::ty::{self, Ty, TyCtxt};
|
2020-05-26 13:48:08 -05:00
|
|
|
use rustc_session::Limit;
|
2021-04-13 02:43:11 -05:00
|
|
|
use rustc_span::{sym, DUMMY_SP};
|
2020-01-30 14:28:16 -06:00
|
|
|
|
|
|
|
type NeedsDropResult<T> = Result<T, AlwaysRequiresDrop>;
|
|
|
|
|
2021-09-02 06:04:29 -05:00
|
|
|
fn needs_drop_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
|
2020-02-09 04:16:57 -06:00
|
|
|
// If we don't know a type doesn't need drop, for example if it's a type
|
|
|
|
// parameter without a `Copy` bound, then we conservatively return that it
|
|
|
|
// needs drop.
|
2021-10-23 05:47:17 -05:00
|
|
|
let adt_has_dtor =
|
|
|
|
|adt_def: &ty::AdtDef| adt_def.destructor(tcx).map(|_| DtorType::Significant);
|
|
|
|
let res = drop_tys_helper(tcx, query.value, query.param_env, adt_has_dtor).next().is_some();
|
2021-09-01 06:06:15 -05:00
|
|
|
|
2020-01-30 14:28:16 -06:00
|
|
|
debug!("needs_drop_raw({:?}) = {:?}", query, res);
|
|
|
|
res
|
|
|
|
}
|
|
|
|
|
2021-04-13 02:43:11 -05:00
|
|
|
fn has_significant_drop_raw<'tcx>(
|
|
|
|
tcx: TyCtxt<'tcx>,
|
|
|
|
query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>,
|
|
|
|
) -> bool {
|
2021-10-23 05:47:17 -05:00
|
|
|
let res =
|
|
|
|
drop_tys_helper(tcx, query.value, query.param_env, adt_consider_insignificant_dtor(tcx))
|
|
|
|
.next()
|
|
|
|
.is_some();
|
2021-04-13 02:43:11 -05:00
|
|
|
debug!("has_significant_drop_raw({:?}) = {:?}", query, res);
|
|
|
|
res
|
|
|
|
}
|
|
|
|
|
2020-01-30 14:28:16 -06:00
|
|
|
struct NeedsDropTypes<'tcx, F> {
|
|
|
|
tcx: TyCtxt<'tcx>,
|
|
|
|
param_env: ty::ParamEnv<'tcx>,
|
|
|
|
query_ty: Ty<'tcx>,
|
|
|
|
seen_tys: FxHashSet<Ty<'tcx>>,
|
2020-02-09 04:16:57 -06:00
|
|
|
/// A stack of types left to process, and the recursion depth when we
|
|
|
|
/// pushed that type. Each round, we pop something from the stack and check
|
|
|
|
/// if it needs drop. If the result depends on whether some other types
|
|
|
|
/// need drop we push them onto the stack.
|
2020-01-30 14:28:16 -06:00
|
|
|
unchecked_tys: Vec<(Ty<'tcx>, usize)>,
|
2020-05-26 13:48:08 -05:00
|
|
|
recursion_limit: Limit,
|
2020-01-30 14:28:16 -06:00
|
|
|
adt_components: F,
|
|
|
|
}
|
|
|
|
|
|
|
|
impl<'tcx, F> NeedsDropTypes<'tcx, F> {
|
|
|
|
fn new(
|
|
|
|
tcx: TyCtxt<'tcx>,
|
|
|
|
param_env: ty::ParamEnv<'tcx>,
|
|
|
|
ty: Ty<'tcx>,
|
|
|
|
adt_components: F,
|
|
|
|
) -> Self {
|
|
|
|
let mut seen_tys = FxHashSet::default();
|
|
|
|
seen_tys.insert(ty);
|
|
|
|
Self {
|
|
|
|
tcx,
|
|
|
|
param_env,
|
|
|
|
seen_tys,
|
|
|
|
query_ty: ty,
|
|
|
|
unchecked_tys: vec![(ty, 0)],
|
2021-07-04 13:02:51 -05:00
|
|
|
recursion_limit: tcx.recursion_limit(),
|
2020-01-30 14:28:16 -06:00
|
|
|
adt_components,
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
impl<'tcx, F, I> Iterator for NeedsDropTypes<'tcx, F>
|
|
|
|
where
|
2021-09-21 04:06:19 -05:00
|
|
|
F: Fn(&ty::AdtDef, SubstsRef<'tcx>) -> NeedsDropResult<I>,
|
2020-01-30 14:28:16 -06:00
|
|
|
I: Iterator<Item = Ty<'tcx>>,
|
|
|
|
{
|
|
|
|
type Item = NeedsDropResult<Ty<'tcx>>;
|
|
|
|
|
|
|
|
fn next(&mut self) -> Option<NeedsDropResult<Ty<'tcx>>> {
|
|
|
|
let tcx = self.tcx;
|
|
|
|
|
|
|
|
while let Some((ty, level)) = self.unchecked_tys.pop() {
|
2020-05-26 13:48:08 -05:00
|
|
|
if !self.recursion_limit.value_within_limit(level) {
|
2020-01-30 14:28:16 -06:00
|
|
|
// Not having a `Span` isn't great. But there's hopefully some other
|
|
|
|
// recursion limit error as well.
|
|
|
|
tcx.sess.span_err(
|
|
|
|
DUMMY_SP,
|
|
|
|
&format!("overflow while checking whether `{}` requires drop", self.query_ty),
|
|
|
|
);
|
|
|
|
return Some(Err(AlwaysRequiresDrop));
|
|
|
|
}
|
|
|
|
|
2020-01-31 16:22:30 -06:00
|
|
|
let components = match needs_drop_components(ty, &tcx.data_layout) {
|
2020-01-30 14:28:16 -06:00
|
|
|
Err(e) => return Some(Err(e)),
|
|
|
|
Ok(components) => components,
|
|
|
|
};
|
|
|
|
debug!("needs_drop_components({:?}) = {:?}", ty, components);
|
|
|
|
|
2020-01-31 16:22:30 -06:00
|
|
|
let queue_type = move |this: &mut Self, component: Ty<'tcx>| {
|
|
|
|
if this.seen_tys.insert(component) {
|
|
|
|
this.unchecked_tys.push((component, level + 1));
|
|
|
|
}
|
|
|
|
};
|
|
|
|
|
2020-01-30 14:28:16 -06:00
|
|
|
for component in components {
|
2020-08-02 17:49:11 -05:00
|
|
|
match *component.kind() {
|
2020-06-21 04:20:48 -05:00
|
|
|
_ if component.is_copy_modulo_regions(tcx.at(DUMMY_SP), self.param_env) => (),
|
2020-01-30 14:28:16 -06:00
|
|
|
|
2020-03-12 20:23:38 -05:00
|
|
|
ty::Closure(_, substs) => {
|
2020-11-07 00:04:27 -06:00
|
|
|
queue_type(self, substs.as_closure().tupled_upvars_ty());
|
2020-01-30 14:28:16 -06:00
|
|
|
}
|
|
|
|
|
2020-05-29 20:04:15 -05:00
|
|
|
ty::Generator(def_id, substs, _) => {
|
2020-03-14 18:24:47 -05:00
|
|
|
let substs = substs.as_generator();
|
2020-11-07 00:04:27 -06:00
|
|
|
queue_type(self, substs.tupled_upvars_ty());
|
2020-03-14 18:24:47 -05:00
|
|
|
|
2020-03-14 20:28:48 -05:00
|
|
|
let witness = substs.witness();
|
2020-08-02 17:49:11 -05:00
|
|
|
let interior_tys = match witness.kind() {
|
2020-10-23 19:21:18 -05:00
|
|
|
&ty::GeneratorWitness(tys) => tcx.erase_late_bound_regions(tys),
|
2020-05-29 20:04:15 -05:00
|
|
|
_ => {
|
|
|
|
tcx.sess.delay_span_bug(
|
|
|
|
tcx.hir().span_if_local(def_id).unwrap_or(DUMMY_SP),
|
|
|
|
&format!("unexpected generator witness type {:?}", witness),
|
|
|
|
);
|
|
|
|
return Some(Err(AlwaysRequiresDrop));
|
|
|
|
}
|
2020-03-14 18:24:47 -05:00
|
|
|
};
|
|
|
|
|
|
|
|
for interior_ty in interior_tys {
|
|
|
|
queue_type(self, interior_ty);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2020-01-30 14:28:16 -06:00
|
|
|
// Check for a `Drop` impl and whether this is a union or
|
|
|
|
// `ManuallyDrop`. If it's a struct or enum without a `Drop`
|
|
|
|
// impl then check whether the field types need `Drop`.
|
|
|
|
ty::Adt(adt_def, substs) => {
|
2021-10-23 05:47:17 -05:00
|
|
|
debug!("Got value {:?} with substs {:?}", adt_def, substs);
|
2021-09-21 04:06:19 -05:00
|
|
|
let tys = match (self.adt_components)(adt_def, substs) {
|
2020-01-30 14:28:16 -06:00
|
|
|
Err(e) => return Some(Err(e)),
|
|
|
|
Ok(tys) => tys,
|
|
|
|
};
|
|
|
|
for required_ty in tys {
|
2021-10-23 05:47:17 -05:00
|
|
|
let subst_ty =
|
|
|
|
tcx.normalize_erasing_regions(self.param_env, required_ty);
|
2020-01-31 16:22:30 -06:00
|
|
|
queue_type(self, subst_ty);
|
2020-01-30 14:28:16 -06:00
|
|
|
}
|
|
|
|
}
|
2020-01-31 16:22:30 -06:00
|
|
|
ty::Array(..) | ty::Opaque(..) | ty::Projection(..) | ty::Param(_) => {
|
2020-01-30 14:28:16 -06:00
|
|
|
if ty == component {
|
2020-01-31 16:22:30 -06:00
|
|
|
// Return the type to the caller: they may be able
|
|
|
|
// to normalize further than we can.
|
2020-01-30 14:28:16 -06:00
|
|
|
return Some(Ok(component));
|
2020-01-31 16:22:30 -06:00
|
|
|
} else {
|
2020-01-30 14:28:16 -06:00
|
|
|
// Store the type for later. We can't return here
|
|
|
|
// because we would then lose any other components
|
|
|
|
// of the type.
|
2020-01-31 16:22:30 -06:00
|
|
|
queue_type(self, component);
|
2020-01-30 14:28:16 -06:00
|
|
|
}
|
|
|
|
}
|
|
|
|
_ => return Some(Err(AlwaysRequiresDrop)),
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2020-03-20 09:03:11 -05:00
|
|
|
None
|
2020-01-30 14:28:16 -06:00
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2021-09-21 03:04:21 -05:00
|
|
|
enum DtorType {
|
|
|
|
/// Type has a `Drop` but it is considered insignificant.
|
|
|
|
/// Check the query `adt_significant_drop_tys` for understanding
|
|
|
|
/// "significant" / "insignificant".
|
|
|
|
Insignificant,
|
|
|
|
|
|
|
|
/// Type has a `Drop` implentation.
|
|
|
|
Significant,
|
|
|
|
}
|
|
|
|
|
2021-04-13 02:43:11 -05:00
|
|
|
// This is a helper function for `adt_drop_tys` and `adt_significant_drop_tys`.
|
|
|
|
// Depending on the implentation of `adt_has_dtor`, it is used to check if the
|
|
|
|
// ADT has a destructor or if the ADT only has a significant destructor. For
|
|
|
|
// understanding significant destructor look at `adt_significant_drop_tys`.
|
2021-10-23 05:47:17 -05:00
|
|
|
fn drop_tys_helper<'tcx>(
|
2021-09-21 04:06:19 -05:00
|
|
|
tcx: TyCtxt<'tcx>,
|
2021-10-23 05:47:17 -05:00
|
|
|
ty: Ty<'tcx>,
|
|
|
|
param_env: rustc_middle::ty::ParamEnv<'tcx>,
|
2021-09-21 03:04:21 -05:00
|
|
|
adt_has_dtor: impl Fn(&ty::AdtDef) -> Option<DtorType>,
|
2021-10-23 05:47:17 -05:00
|
|
|
) -> impl Iterator<Item = NeedsDropResult<Ty<'tcx>>> {
|
2021-09-21 04:06:19 -05:00
|
|
|
let adt_components = move |adt_def: &ty::AdtDef, substs: SubstsRef<'tcx>| {
|
2020-01-30 14:28:16 -06:00
|
|
|
if adt_def.is_manually_drop() {
|
|
|
|
debug!("adt_drop_tys: `{:?}` is manually drop", adt_def);
|
|
|
|
return Ok(Vec::new().into_iter());
|
2021-09-21 03:04:21 -05:00
|
|
|
} else if let Some(dtor_info) = adt_has_dtor(adt_def) {
|
|
|
|
match dtor_info {
|
|
|
|
DtorType::Significant => {
|
|
|
|
debug!("adt_drop_tys: `{:?}` implements `Drop`", adt_def);
|
|
|
|
return Err(AlwaysRequiresDrop);
|
|
|
|
}
|
|
|
|
DtorType::Insignificant => {
|
|
|
|
debug!("adt_drop_tys: `{:?}` drop is insignificant", adt_def);
|
2021-09-21 04:06:19 -05:00
|
|
|
|
|
|
|
// Since the destructor is insignificant, we just want to make sure all of
|
|
|
|
// the passed in type parameters are also insignificant.
|
|
|
|
// Eg: Vec<T> dtor is insignificant when T=i32 but significant when T=Mutex.
|
|
|
|
return Ok(substs.types().collect::<Vec<Ty<'_>>>().into_iter());
|
2021-09-21 03:04:21 -05:00
|
|
|
}
|
|
|
|
}
|
2020-01-30 14:28:16 -06:00
|
|
|
} else if adt_def.is_union() {
|
|
|
|
debug!("adt_drop_tys: `{:?}` is a union", adt_def);
|
|
|
|
return Ok(Vec::new().into_iter());
|
|
|
|
}
|
2021-10-23 05:47:17 -05:00
|
|
|
debug!("Path");
|
|
|
|
Ok(adt_def
|
|
|
|
.all_fields()
|
|
|
|
.map(|field| {
|
|
|
|
let r = tcx.type_of(field.did).subst(tcx, substs);
|
|
|
|
debug!("Subst into {:?} with {:?} gettng {:?}", field, substs, r);
|
|
|
|
r
|
|
|
|
})
|
|
|
|
.collect::<Vec<_>>()
|
|
|
|
.into_iter())
|
2020-01-30 14:28:16 -06:00
|
|
|
};
|
|
|
|
|
2021-10-23 05:47:17 -05:00
|
|
|
NeedsDropTypes::new(tcx, param_env, ty, adt_components)
|
2020-01-30 14:28:16 -06:00
|
|
|
}
|
|
|
|
|
2021-10-23 05:47:17 -05:00
|
|
|
fn adt_consider_insignificant_dtor<'tcx>(
|
|
|
|
tcx: TyCtxt<'tcx>,
|
|
|
|
) -> impl Fn(&ty::AdtDef) -> Option<DtorType> + 'tcx {
|
|
|
|
move |adt_def: &ty::AdtDef| {
|
2021-09-22 04:17:30 -05:00
|
|
|
let is_marked_insig = tcx.has_attr(adt_def.did, sym::rustc_insignificant_dtor);
|
|
|
|
if is_marked_insig {
|
|
|
|
// In some cases like `std::collections::HashMap` where the struct is a wrapper around
|
|
|
|
// a type that is a Drop type, and the wrapped type (eg: `hashbrown::HashMap`) lies
|
|
|
|
// outside stdlib, we might choose to still annotate the the wrapper (std HashMap) with
|
|
|
|
// `rustc_insignificant_dtor`, even if the type itself doesn't have a `Drop` impl.
|
|
|
|
Some(DtorType::Insignificant)
|
|
|
|
} else if adt_def.destructor(tcx).is_some() {
|
|
|
|
// There is a Drop impl and the type isn't marked insignificant, therefore Drop must be
|
|
|
|
// significant.
|
|
|
|
Some(DtorType::Significant)
|
|
|
|
} else {
|
|
|
|
// No destructor found nor the type is annotated with `rustc_insignificant_dtor`, we
|
|
|
|
// treat this as the simple case of Drop impl for type.
|
|
|
|
None
|
|
|
|
}
|
2021-10-23 05:47:17 -05:00
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
fn adt_drop_tys(tcx: TyCtxt<'_>, def_id: DefId) -> Result<&ty::List<Ty<'_>>, AlwaysRequiresDrop> {
|
|
|
|
// This is for the "adt_drop_tys" query, that considers all `Drop` impls, therefore all dtors are
|
|
|
|
// significant.
|
|
|
|
let adt_has_dtor =
|
|
|
|
|adt_def: &ty::AdtDef| adt_def.destructor(tcx).map(|_| DtorType::Significant);
|
|
|
|
drop_tys_helper(tcx, tcx.type_of(def_id), tcx.param_env(def_id), adt_has_dtor)
|
|
|
|
.collect::<Result<Vec<_>, _>>()
|
|
|
|
.map(|components| tcx.intern_type_list(&components))
|
|
|
|
}
|
|
|
|
|
|
|
|
fn adt_significant_drop_tys(
|
|
|
|
tcx: TyCtxt<'_>,
|
|
|
|
def_id: DefId,
|
|
|
|
) -> Result<&ty::List<Ty<'_>>, AlwaysRequiresDrop> {
|
|
|
|
drop_tys_helper(
|
|
|
|
tcx,
|
|
|
|
tcx.type_of(def_id),
|
|
|
|
tcx.param_env(def_id),
|
|
|
|
adt_consider_insignificant_dtor(tcx),
|
|
|
|
)
|
|
|
|
.collect::<Result<Vec<_>, _>>()
|
|
|
|
.map(|components| tcx.intern_type_list(&components))
|
2021-04-13 02:43:11 -05:00
|
|
|
}
|
|
|
|
|
2020-07-05 15:00:14 -05:00
|
|
|
pub(crate) fn provide(providers: &mut ty::query::Providers) {
|
2021-04-13 02:43:11 -05:00
|
|
|
*providers = ty::query::Providers {
|
2021-09-02 06:04:29 -05:00
|
|
|
needs_drop_raw,
|
2021-04-13 02:43:11 -05:00
|
|
|
has_significant_drop_raw,
|
|
|
|
adt_drop_tys,
|
|
|
|
adt_significant_drop_tys,
|
|
|
|
..*providers
|
|
|
|
};
|
2020-01-30 14:28:16 -06:00
|
|
|
}
|