# DPiSort::universe-mismatch


**Key:** `DPiSort::universe-mismatch`

**Category:** universe · **Severity:** error

**Source:** [`src/diag/hints.nix:848`](https://github.com/kleisli-io/nix-effects/blob/main/src/diag/hints.nix#L848)

the sort position of `pi` must live in U(0); `descPi` takes a small domain. Use `u 0`, or encode the dependency through an index instead of the Pi domain.

## Example

`Hint::DPiSort::universe-mismatch` means the `DPiSort` position uses a universe level that is too large for that slot. The example shows the failing form first, then one way to give the checker the missing structure.

```nix
# Bad: descPi's domain sort is too large.
descPi (u 1) f (_: descRet tt)

# Better: use a small domain sort.
descPi (u 0) f (_: descRet tt)

```


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