Does Heck's "necessarily imply" standard bar a § 1983 suit only if, as some circuit courts have held, success would "necessarily require" plaintiff to negate the underlying conviction, or is it enough, as other circuits and California appellate courts have decided, that prevailing on the § 1983 claim would "impugn," "tend to undermine," or "cast a shadow over" the conviction?

Does Heck's 'necessarily imply' standard bar a § 1983 suit only if success would 'necessarily require' plaintiff to negate the underlying conviction, or is it enough that prevailing on the § 1983 claim would 'impugn,' 'tend to undermine,' or 'cast a shadow over' the conviction?