Function const_item_rhs_to_expr 

pub fn const_item_rhs_to_expr<'tcx>(
    tcx: TyCtxt<'tcx>,
    ct_rhs: ConstItemRhs<'tcx>,
) -> Option<&'tcx Expr<'tcx>>

Extracts the [Expr] backing a const item’s right-hand side, if it has one.