bjoernager/rust
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Re-introduce cycle-check in assoc. item resolution.

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This commit is contained in:
Michael Woerister 2017-05-15 12:21:28 +02:00
parent 8da2fe8ed7
commit 40a6734ae1
1 changed files with 32 additions and 6 deletions
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34
src/librustc/traits/project.rs
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@ -29,6 +29,7 @@ use infer::type_variable::TypeVariableOrigin;
use rustc_data_structures::snapshot_map::{Snapshot, SnapshotMap};
use syntax::ast;
use syntax::symbol::Symbol;
use syntax_pos::DUMMY_SP;
use ty::subst::Subst;
use ty::{self, ToPredicate, ToPolyTraitRef, Ty, TyCtxt};
use ty::fold::{TypeFoldable, TypeFolder};
@ -1317,14 +1318,39 @@ fn assoc_ty_def<'cx, 'gcx, 'tcx>(
assoc_ty_name: ast::Name)
-> Option<specialization_graph::NodeItem<ty::AssociatedItem>>
{
let trait_def_id = selcx.tcx().impl_trait_ref(impl_def_id).unwrap().def_id;
let trait_def = selcx.tcx().trait_def(trait_def_id);
let tcx = selcx.tcx();
let trait_def_id = tcx.impl_trait_ref(impl_def_id).unwrap().def_id;
let trait_def = tcx.trait_def(trait_def_id);
// This function may be called while we are still building the
// specialization graph that is queried below (via TraidDef::ancestors()),
// so, in order to avoid infinite recursion, we detect this case by
// seeing if a query of the specialization graph fails with a cycle error.
// If we are in cycle, and thus still building the graph, we perform a
// reduced version of the associated item lookup that does not need the
// specialization graph.
let specialization_graph_complete =
ty::queries::specialization_graph_of::try_get(tcx,
DUMMY_SP,
trait_def_id).is_ok();
if !specialization_graph_complete {
let impl_node = specialization_graph::Node::Impl(impl_def_id);
for item in impl_node.items(tcx) {
if item.kind == ty::AssociatedKind::Type && item.name == assoc_ty_name {
return Some(specialization_graph::NodeItem {
node: specialization_graph::Node::Impl(impl_def_id),
item: item,
});
}
}
None
} else {
trait_def
.ancestors(selcx.tcx(), impl_def_id)
.defs(selcx.tcx(), assoc_ty_name, ty::AssociatedKind::Type)
.ancestors(tcx, impl_def_id)
.defs(tcx, assoc_ty_name, ty::AssociatedKind::Type)
.next()
}
}
// # Cache