Function check_invariant

fn check_invariant(
    genv: GlobalEnv<'_, '_>,
    cache: &mut FixQueryCache,
    def_id: MaybeExternId,
    adt_def: &AdtDef,
    span: Span,
    invariant: &Invariant,
    opts: InferOpts,
) -> Result<(), ErrorGuaranteed>