Function stable_impl_name 

fn stable_impl_name(tcx: TyCtxt<'_>, impl_id: DefId) -> String

A name for an impl block derived from its header: SelfTy_as_Trait for trait impls and SelfTy for inherent impls. In the rare case where several impls in the same parent get the same name, e.g., because their generic parameters are named differently, they are suffixed with their index among those impls.