fn const_vars_since_snapshot<'db>(
table: &mut UnificationTable<InPlace<ConstVidKey<'db>, &'_ mut UnificationStorage<ConstVidKey<'db>>, &'_ mut InferCtxtUndoLogs<'db>>>,
snapshot_var_len: usize,
) -> (Range<ConstVid>, Vec<Span>)fn const_vars_since_snapshot<'db>(
table: &mut UnificationTable<InPlace<ConstVidKey<'db>, &'_ mut UnificationStorage<ConstVidKey<'db>>, &'_ mut InferCtxtUndoLogs<'db>>>,
snapshot_var_len: usize,
) -> (Range<ConstVid>, Vec<Span>)