Function rustc_typeck::check::check_opaque_for_cycles

fn check_opaque_for_cycles<'tcx>(
    tcx: TyCtxt<'tcx>, 
    def_id: LocalDefId, 
    substs: SubstsRef<'tcx>, 
    span: Span, 
    origin: &OpaqueTyOrigin
)

Checks that an opaque type does not contain cycles.