added a few comments

This commit is contained in:
Niko Matsakis 2019-05-08 15:58:42 -04:00 committed by Alexander Regueiro
parent 2cdd7f8387
commit 963e22c38c

View File

@ -571,6 +571,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx> + 'o {
/// Given the type/lifetime/const arguments provided to some path (along with
/// an implicit `Self`, if this is a trait reference), returns the complete
/// set of substitutions. This may involve applying defaulted type parameters.
/// Also returns back constriants on associated types.
///
/// Note that the type listing given here is *exactly* what the user provided.
fn create_substs_for_ast_path<'a>(&self,
@ -1091,6 +1092,10 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx> + 'o {
}), binding.span));
}
ConvertedBindingKind::Constraint(ref ast_bounds) => {
// "Desugar" a constraint like `T: Iterator<Item: Debug>` to
//
// `<T as Iterator>::Item: Debug`
//
// Calling `skip_binder` is okay, because the predicates are re-bound later by
// `instantiate_poly_trait_ref`.
let param_ty = tcx.mk_projection(assoc_ty.def_id, candidate.skip_binder().substs);