# Numba appears to ignore explicit type signature

**URL:** <https://numba.discourse.group/t/numba-appears-to-ignore-explicit-type-signature/1927>\
**Category:** Community Support\
**Created:** [May 8, 2023, 4:19pm UTC](https://numba.discourse.group/t/numba-appears-to-ignore-explicit-type-signature/1927 "2023-05-08T16:19:17Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![nelson2005](https://yyz2.discourse-cdn.com/free1/user_avatar/numba.discourse.group/nelson2005/32/47_2.png) [@nelson2005](https://numba.discourse.group/u/nelson2005)\
**Post date:** [May 8, 2023, 4:19pm UTC](https://numba.discourse.group/t/numba-appears-to-ignore-explicit-type-signature/1927/1 "2023-05-08T16:19:17Z")

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When I supply this explicit type signature, I’d expect an error instead of a silent conversion to a different signature. I understand the function definition can’t satisfy the signature, but why wouldn’t a compile error be raised?

```python
import numba
@numba.njit("i8()")
def demo():
    raise RuntimeError('')

print(demo.nopython_signatures)

```

> [() → none]

---

<div class="post-metadata">

**Author:** ![DannyWeitekamp](https://yyz2.discourse-cdn.com/free1/user_avatar/numba.discourse.group/dannyweitekamp/32/144_2.png) [@DannyWeitekamp](https://numba.discourse.group/u/DannyWeitekamp)\
**Post date:** [May 9, 2023, 3:22pm UTC](https://numba.discourse.group/t/numba-appears-to-ignore-explicit-type-signature/1927/2 "2023-05-09T15:22:38Z")

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The 0.57.0 release has been giving me similar issues, making a few things a little trickier to debug. For instance I needed to migrate the way **hash** was implemented from overload(hash) to overload\_method. In the meantime the error messages I was getting had me thinking my hash function was returning the type “none”, when in fact my hash function wasn’t even being called at all because the overload convention changed. Took a little longer than I would have liked to figure out.