Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Remove unification despite ambiguity in projection #33555

Merged
merged 1 commit into from
May 14, 2016
Merged

Remove unification despite ambiguity in projection #33555

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
58 changes: 1 addition & 57 deletions src/librustc/traits/project.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -218,10 +218,7 @@ fn project_and_unify_type<'cx, 'gcx, 'tcx>(
obligation.cause.clone(),
obligation.recursion_depth) {
Some(n) => n,
None => {
consider_unification_despite_ambiguity(selcx, obligation);
return Ok(None);
}
None => return Ok(None),
};

debug!("project_and_unify_type: normalized_ty={:?} obligations={:?}",
Expand All @@ -240,59 +237,6 @@ fn project_and_unify_type<'cx, 'gcx, 'tcx>(
}
}

fn consider_unification_despite_ambiguity<'cx, 'gcx, 'tcx>(
selcx: &mut SelectionContext<'cx, 'gcx, 'tcx>,
obligation: &ProjectionObligation<'tcx>)
{
debug!("consider_unification_despite_ambiguity(obligation={:?})",
obligation);

let def_id = obligation.predicate.projection_ty.trait_ref.def_id;
match selcx.tcx().lang_items.fn_trait_kind(def_id) {
Some(_) => { }
None => { return; }
}

let infcx = selcx.infcx();
let self_ty = obligation.predicate.projection_ty.trait_ref.self_ty();
let self_ty = infcx.shallow_resolve(self_ty);
debug!("consider_unification_despite_ambiguity: self_ty.sty={:?}",
self_ty.sty);
match self_ty.sty {
ty::TyClosure(closure_def_id, substs) => {
let closure_typer = selcx.closure_typer();
let closure_type = closure_typer.closure_type(closure_def_id, substs);
let ty::Binder((_, ret_type)) =
infcx.tcx.closure_trait_ref_and_return_type(def_id,
self_ty,
&closure_type.sig,
util::TupleArgumentsFlag::No);
// We don't have to normalize the return type here - this is only
// reached for TyClosure: Fn inputs where the closure kind is
// still unknown, which should only occur in typeck where the
// closure type is already normalized.
let (ret_type, _) =
infcx.replace_late_bound_regions_with_fresh_var(
obligation.cause.span,
infer::AssocTypeProjection(obligation.predicate.projection_ty.item_name),
&ty::Binder(ret_type));

debug!("consider_unification_despite_ambiguity: ret_type={:?}",
ret_type);
let origin = TypeOrigin::RelateOutputImplTypes(obligation.cause.span);
let obligation_ty = obligation.predicate.ty;
match infcx.eq_types(true, origin, obligation_ty, ret_type) {
Ok(InferOk { obligations, .. }) => {
// FIXME(#32730) propagate obligations
assert!(obligations.is_empty());
}
Err(_) => { /* ignore errors */ }
}
}
_ => { }
}
}

/// Normalizes any associated type projections in `value`, replacing
/// them with a fully resolved type where possible. The return value
/// combines the normalized result and any additional obligations that
Expand Down