diff options
| -rw-r--r-- | src/librustc_typeck/astconv.rs | 13 | ||||
| -rw-r--r-- | src/librustc_typeck/collect.rs | 2 |
2 files changed, 13 insertions, 2 deletions
diff --git a/src/librustc_typeck/astconv.rs b/src/librustc_typeck/astconv.rs index 881f66afc91..7d275e48a29 100644 --- a/src/librustc_typeck/astconv.rs +++ b/src/librustc_typeck/astconv.rs @@ -42,8 +42,17 @@ pub struct PathSeg(pub DefId, pub usize); pub trait AstConv<'tcx> { fn tcx<'a>(&'a self) -> TyCtxt<'tcx>; - /// Returns the set of bounds in scope for the type parameter with - /// the given id. + /// Returns predicates in scope of the form `X: Foo`, where `X` is + /// a type parameter `X` with the given id `def_id`. This is a + /// subset of the full set of predicates. + /// + /// This is used for one specific purpose: resolving "short-hand" + /// associated type references like `T::Item`. In principle, we + /// would do that by first getting the full set of predicates in + /// scope and then filtering down to find those that apply to `T`, + /// but this can lead to cycle errors. The problem is that we have + /// to do this resolution *in order to create the predicates in + /// the first place*. Hence, we have this "special pass". fn get_type_parameter_bounds(&self, span: Span, def_id: DefId) -> &'tcx ty::GenericPredicates<'tcx>; diff --git a/src/librustc_typeck/collect.rs b/src/librustc_typeck/collect.rs index 357dcd878f5..0f0568907c6 100644 --- a/src/librustc_typeck/collect.rs +++ b/src/librustc_typeck/collect.rs @@ -250,6 +250,8 @@ impl AstConv<'tcx> for ItemCtxt<'tcx> { } } +/// Returns the predicates defined on `item_def_id` of the form +/// `X: Foo` where `X` is the type parameter `def_id`. fn type_param_predicates( tcx: TyCtxt<'_>, (item_def_id, def_id): (DefId, DefId), |