Function reveal_actual_level_spec 

pub fn reveal_actual_level_spec<Id: Copy>(
    sess: &Session,
    lint: LintId,
    probe_for_lint_level_spec: impl Fn(LintId) -> Option<LevelSpec<Id>>,
) -> LevelSpec<Id>

Verify the effect of special annotations: warnings lint level and lint caps.

The return of this function is suitable for diagnostics.