# Scrut::type-mismatch


**Key:** `Scrut::type-mismatch`

**Category:** elimination · **Severity:** error

**Source:** [`src/diag/hints.nix:866`](https://github.com/kleisli-io/nix-effects/blob/main/src/diag/hints.nix#L866)

the scrutinee's type must match the eliminator's expected shape. Annotate the scrutinee via `ann`, or switch to the eliminator that matches its inferred type.

## Example

`Hint::Scrut::type-mismatch` means the `Scrut` position supplies a term whose type does not match the expected type. The example shows the failing form first, then one way to give the checker the missing structure.

```nix
# Bad: the eliminator is used on a scrutinee of the wrong type.
natElim motive zero succCase true_

# Better: use a scrutinee with the eliminator's type.
natElim motive zero succCase (natLit 3)

```


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