Function rustc_typeck::collect::type_of::opt_const_param_of

pub(in collect) fn opt_const_param_of(
    tcx: TyCtxt<'_>, 
    def_id: LocalDefId
) -> Option<DefId>

Computes the relevant generic parameter for a potential generic const argument.

This should be called using the query tcx.opt_const_param_of.