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refactor has_dtor_of_interest
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@arielb1
arielb1 committed Jul 24, 2015
1 parent bfbc7bc commit 7f9953b
Showing 1 changed file with 75 additions and 130 deletions.
205 changes: 75 additions & 130 deletions src/librustc_typeck/check/dropck.rs
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Expand Up @@ -258,16 +258,20 @@ pub fn check_safety_of_destructor_if_necessary<'a, 'tcx>(rcx: &mut Rcx<'a, 'tcx>
debug!("check_safety_of_destructor_if_necessary typ: {:?} scope: {:?}",
typ, scope);

// types that have been traversed so far by `traverse_type_if_unseen`
let mut breadcrumbs: Vec<Ty<'tcx>> = Vec::new();
let parent_scope = rcx.tcx().region_maps.opt_encl_scope(scope).unwrap_or_else(|| {
rcx.tcx().sess.span_bug(
span, &format!("no enclosing scope found for scope: {:?}", scope))
});

let result = iterate_over_potentially_unsafe_regions_in_type(
rcx,
&mut breadcrumbs,
&mut DropckContext {
rcx: rcx,
span: span,
parent_scope: parent_scope,
breadcrumbs: vec![]
},
TypeContext::Root,
typ,
span,
scope,
0);
match result {
Ok(()) => {}
Expand Down Expand Up @@ -324,55 +328,49 @@ enum TypeContext {
}
}

// The `depth` counts the number of calls to this function;
// the `xref_depth` counts the subset of such calls that go
// across a `Box<T>` or `PhantomData<T>`.
fn iterate_over_potentially_unsafe_regions_in_type<'a, 'tcx>(
rcx: &mut Rcx<'a, 'tcx>,
breadcrumbs: &mut Vec<Ty<'tcx>>,
struct DropckContext<'a, 'b: 'a, 'tcx: 'b> {
rcx: &'a mut Rcx<'b, 'tcx>,
/// types that have already been traversed
breadcrumbs: Vec<Ty<'tcx>>,
/// span for error reporting
span: Span,
/// the scope reachable dtorck types must outlive
parent_scope: region::CodeExtent
}

// `context` is used for reporting overflow errors
fn iterate_over_potentially_unsafe_regions_in_type<'a, 'b, 'tcx>(
cx: &mut DropckContext<'a, 'b, 'tcx>,
context: TypeContext,
ty: Ty<'tcx>,
span: Span,
scope: region::CodeExtent,
depth: usize) -> Result<(), Error<'tcx>>
{
let tcx = cx.rcx.tcx();
// Issue #22443: Watch out for overflow. While we are careful to
// handle regular types properly, non-regular ones cause problems.
let recursion_limit = rcx.tcx().sess.recursion_limit.get();
let recursion_limit = tcx.sess.recursion_limit.get();
if depth / 4 >= recursion_limit {
// This can get into rather deep recursion, especially in the
// presence of things like Vec<T> -> Unique<T> -> PhantomData<T> -> T.
// use a higher recursion limit to avoid errors.
return Err(Error::Overflow(context, ty))
}

let opt_phantom_data_def_id = rcx.tcx().lang_items.phantom_data();
let opt_phantom_data_def_id = tcx.lang_items.phantom_data();

// FIXME(arielb1): don't be O(n^2)
if breadcrumbs.contains(&ty) {
if cx.breadcrumbs.contains(&ty) {
debug!("iterate_over_potentially_unsafe_regions_in_type \
{}ty: {} scope: {:?} - cached",
(0..depth).map(|_| ' ').collect::<String>(),
ty, scope);
ty, cx.parent_scope);
return Ok(()); // we already visited this type
}
breadcrumbs.push(ty);
cx.breadcrumbs.push(ty);
debug!("iterate_over_potentially_unsafe_regions_in_type \
{}ty: {} scope: {:?}",
(0..depth).map(|_| ' ').collect::<String>(),
ty, scope);

// FIXME(arielb1): move into has_dtor_of_interest
let dtor_kind = match ty.sty {
ty::TyEnum(def_id, _) |
ty::TyStruct(def_id, _) => {
let destructor_for_type = rcx.tcx().destructor_for_type.borrow();
match destructor_for_type.get(&def_id) {
Some(def_id) => DtorKind::KnownDropMethod(*def_id),
None => DtorKind::PureRecur,
}
}
ty::TyTrait(..) | ty::TyProjection(..) => DtorKind::Unknown,
_ => DtorKind::PureRecur,
};

ty, cx.parent_scope);

// If `typ` has a destructor, then we must ensure that all
// borrowed data reachable via `typ` must outlive the parent
Expand Down Expand Up @@ -402,38 +400,24 @@ fn iterate_over_potentially_unsafe_regions_in_type<'a, 'tcx>(
// type parameters are unbounded. If both conditions hold, we
// simply skip the `type_must_outlive` call entirely (but
// resume the recursive checking of the type-substructure).
if has_dtor_of_interest(rcx.tcx(), dtor_kind, ty, span) {
if has_dtor_of_interest(tcx, ty, cx.span) {
debug!("iterate_over_potentially_unsafe_regions_in_type \
{}ty: {} - is a dtorck type!",
(0..depth).map(|_| ' ').collect::<String>(),
ty);

// If `ty` is a dtorck type, then we must ensure that all
// borrowed data reachable via `ty` must outlive the
// parent of `scope`. (It does not suffice for it to
// outlive `scope` because that could imply that the
// borrowed data is torn down in between the end of
// `scope` and when the destructor itself actually runs.)
let parent_region =
match rcx.tcx().region_maps.opt_encl_scope(scope) {
Some(parent_scope) => ty::ReScope(parent_scope),
None => rcx.tcx().sess.span_bug(
span, &format!("no enclosing scope found for scope: {:?}",
scope)),
};

regionck::type_must_outlive(rcx,
infer::SubregionOrigin::SafeDestructor(span),
regionck::type_must_outlive(cx.rcx,
infer::SubregionOrigin::SafeDestructor(cx.span),
ty,
parent_region);
ty::ReScope(cx.parent_scope));

return Ok(());
}

debug!("iterate_over_potentially_unsafe_regions_in_type \
{}ty: {} scope: {:?} - checking interior",
(0..depth).map(|_| ' ').collect::<String>(),
ty, scope);
ty, cx.parent_scope);

// We still need to ensure all referenced data is safe.
match ty.sty {
Expand All @@ -446,55 +430,48 @@ fn iterate_over_potentially_unsafe_regions_in_type<'a, 'tcx>(
ty::TyBox(ity) | ty::TyArray(ity, _) | ty::TySlice(ity) => {
// single-element containers, behave like their element
iterate_over_potentially_unsafe_regions_in_type(
rcx, breadcrumbs, context, ity, span, scope, depth+1)
cx, context, ity, depth+1)
}

ty::TyStruct(did, substs) if Some(did) == opt_phantom_data_def_id => {
// PhantomData<T> - behaves identically to T
let ity = *substs.types.get(subst::TypeSpace, 0);
iterate_over_potentially_unsafe_regions_in_type(
rcx, breadcrumbs, context, ity, span, scope, depth+1)
cx, context, ity, depth+1)
}

ty::TyStruct(did, substs) => {
let fields = rcx.tcx().lookup_struct_fields(did);
let fields = tcx.lookup_struct_fields(did);
for field in &fields {
let field_type = rcx.tcx().lookup_field_type(did,
field.id,
substs);
let fty = tcx.lookup_field_type(did, field.id, substs);
let fty = cx.rcx.fcx.resolve_type_vars_if_possible(
cx.rcx.fcx.normalize_associated_types_in(cx.span, &fty));
try!(iterate_over_potentially_unsafe_regions_in_type(
rcx,
breadcrumbs,
cx,
TypeContext::Struct {
def_id: did,
field: field.name,
},
rcx.fcx.resolve_type_vars_if_possible(
rcx.fcx.normalize_associated_types_in(span, &field_type)),
span,
scope,
fty,
depth+1))
}
Ok(())
}

ty::TyEnum(did, substs) => {
let all_variant_info =
rcx.tcx().substd_enum_variants(did, substs);
let all_variant_info = tcx.substd_enum_variants(did, substs);
for variant_info in &all_variant_info {
for (i, arg_type) in variant_info.args.iter().enumerate() {
for (i, fty) in variant_info.args.iter().enumerate() {
let fty = cx.rcx.fcx.resolve_type_vars_if_possible(
cx.rcx.fcx.normalize_associated_types_in(cx.span, &fty));
try!(iterate_over_potentially_unsafe_regions_in_type(
rcx,
breadcrumbs,
cx,
TypeContext::EnumVariant {
def_id: did,
variant: variant_info.name,
arg_index: i,
},
rcx.fcx.resolve_type_vars_if_possible(
rcx.fcx.normalize_associated_types_in(span, arg_type)),
span,
scope,
fty,
depth+1));
}
}
Expand All @@ -505,7 +482,7 @@ fn iterate_over_potentially_unsafe_regions_in_type<'a, 'tcx>(
ty::TyClosure(_, box ty::ClosureSubsts { upvar_tys: ref tys, .. }) => {
for ty in tys {
try!(iterate_over_potentially_unsafe_regions_in_type(
rcx, breadcrumbs, context, ty, span, scope, depth+1))
cx, context, ty, depth+1))
}
Ok(())
}
Expand All @@ -524,7 +501,7 @@ fn iterate_over_potentially_unsafe_regions_in_type<'a, 'tcx>(
}

ty::TyInfer(..) | ty::TyError => {
rcx.tcx().sess.delay_span_bug(span, "unresolved type in regionck");
tcx.sess.delay_span_bug(cx.span, "unresolved type in regionck");
Ok(())
}

Expand All @@ -533,53 +510,18 @@ fn iterate_over_potentially_unsafe_regions_in_type<'a, 'tcx>(
}
}

enum DtorKind {
// Type has an associated drop method with this def id
KnownDropMethod(ast::DefId),

// Type has no destructor (or its dtor is known to be pure
// with respect to lifetimes), though its *substructure*
// may carry a destructor.
PureRecur,

// Type may have impure destructor that is unknown;
// e.g. `Box<Trait+'a>`
Unknown,
}

fn has_dtor_of_interest<'tcx>(tcx: &ty::ctxt<'tcx>,
dtor_kind: DtorKind,
typ: ty::Ty<'tcx>,
ty: ty::Ty<'tcx>,
span: Span) -> bool {
let has_dtor_of_interest: bool;

match dtor_kind {
DtorKind::PureRecur => {
has_dtor_of_interest = false;
debug!("typ: {:?} has no dtor, and thus is uninteresting",
typ);
}
DtorKind::Unknown => {
debug!("trait: {:?} is interesting", typ);
has_dtor_of_interest = true;
/*
match bounds.region_bound {
ty::ReStatic => {
debug!("trait: {:?} has 'static bound, and thus is uninteresting",
typ);
has_dtor_of_interest = false;
}
ty::ReEmpty => {
debug!("trait: {:?} has empty region bound, and thus is uninteresting",
typ);
has_dtor_of_interest = false;
}
r => {
match ty.sty {
ty::TyEnum(def_id, _) | ty::TyStruct(def_id, _) => {
let dtor_method_did = match tcx.destructor_for_type.borrow().get(&def_id) {
Some(def_id) => *def_id,
None => {
debug!("ty: {:?} has no dtor, and thus isn't a dropck type", ty);
return false;
}
}
*/
}
DtorKind::KnownDropMethod(dtor_method_did) => {
};
let impl_did = tcx.impl_of_method(dtor_method_did)
.unwrap_or_else(|| {
tcx.sess.span_bug(
Expand Down Expand Up @@ -631,8 +573,8 @@ fn has_dtor_of_interest<'tcx>(tcx: &ty::ctxt<'tcx>,

if result {
has_pred_of_interest = true;
debug!("typ: {:?} has interesting dtor due to generic preds, e.g. {:?}",
typ, pred);
debug!("ty: {:?} has interesting dtor due to generic preds, e.g. {:?}",
ty, pred);
break 'items;
}
}
Expand All @@ -651,22 +593,25 @@ fn has_dtor_of_interest<'tcx>(tcx: &ty::ctxt<'tcx>,
let has_region_param_of_interest =
dtor_generics.has_region_params(subst::TypeSpace);

has_dtor_of_interest =
let has_dtor_of_interest =
has_region_param_of_interest ||
has_pred_of_interest;

if has_dtor_of_interest {
debug!("typ: {:?} has interesting dtor, due to \
debug!("ty: {:?} has interesting dtor, due to \
region params: {} or pred: {}",
typ,
ty,
has_region_param_of_interest,
has_pred_of_interest);
} else {
debug!("typ: {:?} has dtor, but it is uninteresting",
typ);
debug!("ty: {:?} has dtor, but it is uninteresting", ty);
}
has_dtor_of_interest
}
ty::TyTrait(..) | ty::TyProjection(..) => {
debug!("ty: {:?} isn't known, and therefore is a dropck type", ty);
true
},
_ => false
}

return has_dtor_of_interest;
}

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