mikros/rust
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

2229: Early exit when we see an insigificant drop

Browse Source
This commit is contained in:
Aman Arora 2021-09-21 04:04:21 -04:00
parent e7958d35ca
commit 95cfbe43d2
1 changed files with 33 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

42
compiler/rustc_ty_utils/src/needs_drop.rs
View File

@ -171,6 +171,16 @@ where
}
}
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,
}
// 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
@ -178,15 +188,23 @@ where
fn adt_drop_tys_helper(
tcx: TyCtxt<'_>,
def_id: DefId,
adt_has_dtor: impl Fn(&ty::AdtDef) -> bool,
adt_has_dtor: impl Fn(&ty::AdtDef) -> Option<DtorType>,
) -> Result<&ty::List<Ty<'_>>, AlwaysRequiresDrop> {
let adt_components = move |adt_def: &ty::AdtDef| {
if adt_def.is_manually_drop() {
debug!("adt_drop_tys: `{:?}` is manually drop", adt_def);
return Ok(Vec::new().into_iter());
} else if adt_has_dtor(adt_def) {
debug!("adt_drop_tys: `{:?}` implements `Drop`", adt_def);
return Err(AlwaysRequiresDrop);
} 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);
return Ok(Vec::new().into_iter());
}
}
} else if adt_def.is_union() {
debug!("adt_drop_tys: `{:?}` is a union", adt_def);
return Ok(Vec::new().into_iter());
@ -204,7 +222,10 @@ fn adt_drop_tys_helper(
}
fn adt_drop_tys(tcx: TyCtxt<'_>, def_id: DefId) -> Result<&ty::List<Ty<'_>>, AlwaysRequiresDrop> {
let adt_has_dtor = |adt_def: &ty::AdtDef| adt_def.destructor(tcx).is_some();
// This is for the "needs_drop" 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);
adt_drop_tys_helper(tcx, def_id, adt_has_dtor)
}
@ -213,10 +234,13 @@ fn adt_significant_drop_tys(
def_id: DefId,
) -> Result<&ty::List<Ty<'_>>, AlwaysRequiresDrop> {
let adt_has_dtor = |adt_def: &ty::AdtDef| {
adt_def
.destructor(tcx)
.map(|dtor| !tcx.has_attr(dtor.did, sym::rustc_insignificant_dtor))
.unwrap_or(false)
adt_def.destructor(tcx).map(|dtor| {
if tcx.has_attr(dtor.did, sym::rustc_insignificant_dtor) {
DtorType::Insignificant
} else {
DtorType::Significant
}
})
};
adt_drop_tys_helper(tcx, def_id, adt_has_dtor)
}