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Auto merge of #41319 - eddyb:demand-adt-sized-constraint, r=arielb1

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rustc: provide adt_sized_constraint as an on-demand query.

By using `queries::adt_sized_constraint::try_get`, we can detect cycles without a separate stack.
r? @nikomatsakis
This commit is contained in:
bors 2017-04-15 19:44:17 +00:00
commit d5cf1cb64c
2 changed files with 61 additions and 77 deletions
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137
src/librustc/ty/mod.rs
View File

@ -1695,85 +1695,21 @@ pub fn destructor(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Option<Destructor> {
/// Due to normalization being eager, this applies even if
/// the associated type is behind a pointer, e.g. issue #31299.
pub fn sized_constraint(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Ty<'tcx> {
self.calculate_sized_constraint_inner(tcx.global_tcx(), &mut Vec::new())
}
/// Calculates the Sized-constraint.
///
/// As the Sized-constraint of enums can be a *set* of types,
/// the Sized-constraint may need to be a set also. Because introducing
/// a new type of IVar is currently a complex affair, the Sized-constraint
/// may be a tuple.
///
/// In fact, there are only a few options for the constraint:
/// - `bool`, if the type is always Sized
/// - an obviously-unsized type
/// - a type parameter or projection whose Sizedness can't be known
/// - a tuple of type parameters or projections, if there are multiple
/// such.
/// - a TyError, if a type contained itself. The representability
/// check should catch this case.
fn calculate_sized_constraint_inner(&self,
tcx: TyCtxt<'a, 'tcx, 'tcx>,
stack: &mut Vec<DefId>)
-> Ty<'tcx>
{
if let Some(ty) = tcx.maps.adt_sized_constraint.borrow().get(&self.did) {
return ty;
}
// Follow the memoization pattern: push the computation of
// DepNode::SizedConstraint as our current task.
let _task = tcx.dep_graph.in_task(DepNode::SizedConstraint(self.did));
if stack.contains(&self.did) {
debug!("calculate_sized_constraint: {:?} is recursive", self);
// This should be reported as an error by `check_representable`.
//
// Consider the type as Sized in the meanwhile to avoid
// further errors.
tcx.maps.adt_sized_constraint.borrow_mut().insert(self.did, tcx.types.err);
return tcx.types.err;
}
stack.push(self.did);
let tys : Vec<_> =
self.variants.iter().flat_map(|v| {
v.fields.last()
}).flat_map(|f| {
let ty = tcx.item_type(f.did);
self.sized_constraint_for_ty(tcx, stack, ty)
}).collect();
let self_ = stack.pop().unwrap();
assert_eq!(self_, self.did);
let ty = match tys.len() {
_ if tys.references_error() => tcx.types.err,
0 => tcx.types.bool,
1 => tys[0],
_ => tcx.intern_tup(&tys[..], false)
};
let old = tcx.maps.adt_sized_constraint.borrow().get(&self.did).cloned();
match old {
Some(old_ty) => {
debug!("calculate_sized_constraint: {:?} recurred", self);
assert_eq!(old_ty, tcx.types.err);
old_ty
}
None => {
debug!("calculate_sized_constraint: {:?} => {:?}", self, ty);
tcx.maps.adt_sized_constraint.borrow_mut().insert(self.did, ty);
ty
match queries::adt_sized_constraint::try_get(tcx, DUMMY_SP, self.did) {
Ok(ty) => ty,
Err(_) => {
debug!("adt_sized_constraint: {:?} is recursive", self);
// This should be reported as an error by `check_representable`.
//
// Consider the type as Sized in the meanwhile to avoid
// further errors.
tcx.types.err
}
}
}
fn sized_constraint_for_ty(&self,
tcx: TyCtxt<'a, 'tcx, 'tcx>,
stack: &mut Vec<DefId>,
ty: Ty<'tcx>)
-> Vec<Ty<'tcx>> {
let result = match ty.sty {
@ -1791,23 +1727,23 @@ fn sized_constraint_for_ty(&self,
TyTuple(ref tys, _) => {
match tys.last() {
None => vec![],
Some(ty) => self.sized_constraint_for_ty(tcx, stack, ty)
Some(ty) => self.sized_constraint_for_ty(tcx, ty)
}
}
TyAdt(adt, substs) => {
// recursive case
let adt_ty =
adt.calculate_sized_constraint_inner(tcx, stack)
adt.sized_constraint(tcx)
.subst(tcx, substs);
debug!("sized_constraint_for_ty({:?}) intermediate = {:?}",
ty, adt_ty);
if let ty::TyTuple(ref tys, _) = adt_ty.sty {
tys.iter().flat_map(|ty| {
self.sized_constraint_for_ty(tcx, stack, ty)
self.sized_constraint_for_ty(tcx, ty)
}).collect()
} else {
self.sized_constraint_for_ty(tcx, stack, adt_ty)
self.sized_constraint_for_ty(tcx, adt_ty)
}
}
@ -2703,9 +2639,56 @@ fn associated_item<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId)
panic!("associated item not found for def_id: {:?}", def_id);
}
/// Calculates the Sized-constraint.
///
/// As the Sized-constraint of enums can be a *set* of types,
/// the Sized-constraint may need to be a set also. Because introducing
/// a new type of IVar is currently a complex affair, the Sized-constraint
/// may be a tuple.
///
/// In fact, there are only a few options for the constraint:
/// - `bool`, if the type is always Sized
/// - an obviously-unsized type
/// - a type parameter or projection whose Sizedness can't be known
/// - a tuple of type parameters or projections, if there are multiple
/// such.
/// - a TyError, if a type contained itself. The representability
/// check should catch this case.
fn adt_sized_constraint<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
def_id: DefId)
-> Ty<'tcx> {
let def = tcx.lookup_adt_def(def_id);
let tys: Vec<_> = def.variants.iter().flat_map(|v| {
v.fields.last()
}).flat_map(|f| {
let ty = tcx.item_type(f.did);
def.sized_constraint_for_ty(tcx, ty)
}).collect();
let ty = match tys.len() {
_ if tys.references_error() => tcx.types.err,
0 => tcx.types.bool,
1 => tys[0],
_ => tcx.intern_tup(&tys[..], false)
};
debug!("adt_sized_constraint: {:?} => {:?}", def, ty);
ty
}
pub fn provide(providers: &mut ty::maps::Providers) {
*providers = ty::maps::Providers {
associated_item,
adt_sized_constraint,
..*providers
};
}
pub fn provide_extern(providers: &mut ty::maps::Providers) {
*providers = ty::maps::Providers {
adt_sized_constraint,
..*providers
};
}

1
src/librustc_driver/driver.rs
View File

@ -898,6 +898,7 @@ macro_rules! try_with_f {
let mut extern_providers = ty::maps::Providers::default();
cstore::provide(&mut extern_providers);
ty::provide_extern(&mut extern_providers);
TyCtxt::create_and_enter(sess,
local_providers,