# MuPayload::type-mismatch


**Key:** `MuPayload::type-mismatch`

**Category:** indexing · **Severity:** error

**Source:** [`src/diag/hints.nix:888`](https://github.com/kleisli-io/nix-effects/blob/main/src/diag/hints.nix#L888)

the payload of `con` must inhabit the description's interpretation at the given index

## Example

`Hint::MuPayload::type-mismatch` means the `MuPayload` 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 payload does not match the constructor description.
con expectedIndex wrongPayload

# Better: build a payload matching the description at that index.
con expectedIndex expectedPayload

```


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