Function interp_binding_is_locked 

fn interp_binding_is_locked(
    positional: &[RValue],
    _named: &[(String, RValue)],
    _context: &BuiltinContext<'_>,
) -> Result<RValue, RError>

Check whether a binding is locked in an environment.

@param sym name of the binding to check (character string) @param env environment containing the binding @return logical scalar: TRUE if the binding is locked, FALSE otherwise