# HARN-TYP-021 — variant type is used in an invalid position
**Category:** Type checker (TYP)
**Variant:** `Code::InvalidVariantUse` (invalid variant use)
## What it means
Harn's static type checker reports this when it cannot reconcile the types
involved at this position. Type errors block compilation — Harn refuses to run a
program whose types do not line up.
Specifically: variant type is used in an invalid position.
## How to fix
- Adjust the expression so its inferred type matches the surrounding context.
- Widen the declared type at the binding / parameter / return position to accept the actual type.
- Convert the value explicitly (`as`, a stdlib coercion, etc.) when a safe conversion exists.
## Stability
This code is stable. Its identifier, category, and meaning will not change
without a deprecation cycle. Cross-language tooling and IDE integrations can
dispatch on it directly.