# AnnType::not-a-type


**Key:** `AnnType::not-a-type`

**Category:** sort · **Severity:** error

**Source:** [`src/diag/hints.nix:862`](https://github.com/kleisli-io/nix-effects/blob/main/src/diag/hints.nix#L862)

the annotation position must be a type (live in some U(k)), not a term. Write a type expression such as `nat`, `bool`, `u 0`, or a user-defined datatype.

## Example

`Hint::AnnType::not-a-type` means the `AnnType` position uses a term or value where the checker needs a type. The example shows the failing form first, then one way to give the checker the missing structure.

```nix
# Bad: the annotation is a term.
ann (natLit 0) (natLit 1)

# Better: annotate with a type.
ann (natLit 0) nat

```


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