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use super::supertraits;
use super::elaborate_predicates;
use middle::subst::{self, SelfSpace, TypeSpace};
use middle::traits;
use middle::ty::{self, ToPolyTraitRef, Ty};
use std::rc::Rc;
use syntax::ast;
use util::ppaux::Repr;
pub enum ObjectSafetyViolation<'tcx> {
SizedSelf,
SupertraitSelf,
Method(Rc<ty::Method<'tcx>>, MethodViolationCode),
}
#[derive(Copy,Clone,Debug)]
pub enum MethodViolationCode {
StaticMethod,
ReferencesSelf,
Generic,
}
pub fn is_object_safe<'tcx>(tcx: &ty::ctxt<'tcx>,
trait_def_id: ast::DefId)
-> bool
{
let cached_result =
tcx.object_safety_cache.borrow().get(&trait_def_id).cloned();
let result =
cached_result.unwrap_or_else(|| {
let result = object_safety_violations(tcx, trait_def_id).is_empty();
tcx.object_safety_cache.borrow_mut().insert(trait_def_id, result);
result
});
debug!("is_object_safe({}) = {}", trait_def_id.repr(tcx), result);
result
}
pub fn object_safety_violations<'tcx>(tcx: &ty::ctxt<'tcx>,
trait_def_id: ast::DefId)
-> Vec<ObjectSafetyViolation<'tcx>>
{
traits::supertrait_def_ids(tcx, trait_def_id)
.flat_map(|def_id| object_safety_violations_for_trait(tcx, def_id).into_iter())
.collect()
}
fn object_safety_violations_for_trait<'tcx>(tcx: &ty::ctxt<'tcx>,
trait_def_id: ast::DefId)
-> Vec<ObjectSafetyViolation<'tcx>>
{
let mut violations: Vec<_> =
ty::trait_items(tcx, trait_def_id).iter()
.flat_map(|item| {
match *item {
ty::MethodTraitItem(ref m) => {
object_safety_violation_for_method(tcx, trait_def_id, &**m)
.map(|code| ObjectSafetyViolation::Method(m.clone(), code))
.into_iter()
}
ty::TypeTraitItem(_) => {
None.into_iter()
}
}
})
.collect();
if trait_has_sized_self(tcx, trait_def_id) {
violations.push(ObjectSafetyViolation::SizedSelf);
}
if supertraits_reference_self(tcx, trait_def_id) {
violations.push(ObjectSafetyViolation::SupertraitSelf);
}
debug!("object_safety_violations_for_trait(trait_def_id={}) = {}",
trait_def_id.repr(tcx),
violations.repr(tcx));
violations
}
fn supertraits_reference_self<'tcx>(tcx: &ty::ctxt<'tcx>,
trait_def_id: ast::DefId)
-> bool
{
let trait_def = ty::lookup_trait_def(tcx, trait_def_id);
let trait_ref = trait_def.trait_ref.clone();
let trait_ref = trait_ref.to_poly_trait_ref();
let predicates = ty::lookup_super_predicates(tcx, trait_def_id);
predicates
.predicates
.into_iter()
.map(|predicate| predicate.subst_supertrait(tcx, &trait_ref))
.any(|predicate| {
match predicate {
ty::Predicate::Trait(ref data) => {
data.0.trait_ref.substs.types.get_slice(TypeSpace)
.iter()
.cloned()
.any(is_self)
}
ty::Predicate::Projection(..) |
ty::Predicate::TypeOutlives(..) |
ty::Predicate::RegionOutlives(..) |
ty::Predicate::Equate(..) => {
false
}
}
})
}
fn trait_has_sized_self<'tcx>(tcx: &ty::ctxt<'tcx>,
trait_def_id: ast::DefId)
-> bool
{
let trait_def = ty::lookup_trait_def(tcx, trait_def_id);
let trait_predicates = ty::lookup_predicates(tcx, trait_def_id);
generics_require_sized_self(tcx, &trait_def.generics, &trait_predicates)
}
fn generics_require_sized_self<'tcx>(tcx: &ty::ctxt<'tcx>,
generics: &ty::Generics<'tcx>,
predicates: &ty::GenericPredicates<'tcx>)
-> bool
{
let sized_def_id = match tcx.lang_items.sized_trait() {
Some(def_id) => def_id,
None => { return false; }
};
let free_substs = ty::construct_free_substs(tcx, generics, ast::DUMMY_NODE_ID);
let predicates = predicates.instantiate(tcx, &free_substs).predicates.into_vec();
elaborate_predicates(tcx, predicates)
.any(|predicate| {
match predicate {
ty::Predicate::Trait(ref trait_pred) if trait_pred.def_id() == sized_def_id => {
is_self(trait_pred.0.self_ty())
}
ty::Predicate::Projection(..) |
ty::Predicate::Trait(..) |
ty::Predicate::Equate(..) |
ty::Predicate::RegionOutlives(..) |
ty::Predicate::TypeOutlives(..) => {
false
}
}
})
}
fn object_safety_violation_for_method<'tcx>(tcx: &ty::ctxt<'tcx>,
trait_def_id: ast::DefId,
method: &ty::Method<'tcx>)
-> Option<MethodViolationCode>
{
if generics_require_sized_self(tcx, &method.generics, &method.predicates) {
return None;
}
virtual_call_violation_for_method(tcx, trait_def_id, method)
}
pub fn is_vtable_safe_method<'tcx>(tcx: &ty::ctxt<'tcx>,
trait_def_id: ast::DefId,
method: &ty::Method<'tcx>)
-> bool
{
virtual_call_violation_for_method(tcx, trait_def_id, method).is_none()
}
fn virtual_call_violation_for_method<'tcx>(tcx: &ty::ctxt<'tcx>,
trait_def_id: ast::DefId,
method: &ty::Method<'tcx>)
-> Option<MethodViolationCode>
{
match method.explicit_self {
ty::StaticExplicitSelfCategory => {
return Some(MethodViolationCode::StaticMethod);
}
ty::ByValueExplicitSelfCategory |
ty::ByReferenceExplicitSelfCategory(..) |
ty::ByBoxExplicitSelfCategory => {
}
}
let ref sig = method.fty.sig;
for &input_ty in &sig.0.inputs[1..] {
if contains_illegal_self_type_reference(tcx, trait_def_id, input_ty) {
return Some(MethodViolationCode::ReferencesSelf);
}
}
if let ty::FnConverging(result_type) = sig.0.output {
if contains_illegal_self_type_reference(tcx, trait_def_id, result_type) {
return Some(MethodViolationCode::ReferencesSelf);
}
}
if !method.generics.types.is_empty_in(subst::FnSpace) {
return Some(MethodViolationCode::Generic);
}
None
}
fn contains_illegal_self_type_reference<'tcx>(tcx: &ty::ctxt<'tcx>,
trait_def_id: ast::DefId,
ty: Ty<'tcx>)
-> bool
{
let mut supertraits: Option<Vec<ty::PolyTraitRef<'tcx>>> = None;
let mut error = false;
ty::maybe_walk_ty(ty, |ty| {
match ty.sty {
ty::ty_param(ref param_ty) => {
if param_ty.space == SelfSpace {
error = true;
}
false
}
ty::ty_projection(ref data) => {
if supertraits.is_none() {
let trait_def = ty::lookup_trait_def(tcx, trait_def_id);
let trait_ref = ty::Binder(trait_def.trait_ref.clone());
supertraits = Some(traits::supertraits(tcx, trait_ref).collect());
}
let projection_trait_ref = ty::Binder(data.trait_ref.clone());
let is_supertrait_of_current_trait =
supertraits.as_ref().unwrap().contains(&projection_trait_ref);
if is_supertrait_of_current_trait {
false
} else {
true
}
}
_ => true,
}
});
error
}
impl<'tcx> Repr<'tcx> for ObjectSafetyViolation<'tcx> {
fn repr(&self, tcx: &ty::ctxt<'tcx>) -> String {
match *self {
ObjectSafetyViolation::SizedSelf =>
format!("SizedSelf"),
ObjectSafetyViolation::SupertraitSelf =>
format!("SupertraitSelf"),
ObjectSafetyViolation::Method(ref m, code) =>
format!("Method({},{:?})", m.repr(tcx), code),
}
}
}
fn is_self<'tcx>(ty: Ty<'tcx>) -> bool {
match ty.sty {
ty::ty_param(ref data) => data.space == subst::SelfSpace,
_ => false,
}
}