# \[ANN\] DispatchDoctor.jl 🩺 – offers you a prescription for type stability

**URL:** https://discourse.julialang.org/t/ann-dispatchdoctor-jl-offers-you-a-prescription-for-type-stability/114837
**Category:** Package Announcements
**Created:** [May 28, 2024, 1:07pm UTC](https://discourse.julialang.org/t/ann-dispatchdoctor-jl-offers-you-a-prescription-for-type-stability/114837 "2024-05-28T13:07:16Z")
**Posts on this page:** 1
**Showing post:** 4

<div class="post-metadata">

### Author: ![MilesCranmer](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/milescranmer/32/21070_2.png) [@MilesCranmer](https://discourse.julialang.org/u/MilesCranmer)
#### Post date: [May 28, 2024, 3:17pm UTC](https://discourse.julialang.org/t/ann-dispatchdoctor-jl-offers-you-a-prescription-for-type-stability/114837/4 "2024-05-28T15:17:41Z")

</div>

For example:

```julia
julia> @stable function f(x)
           function inner()
               x = x
               x
           end
           inner()
       end
f (generic function with 1 method)

julia> f(1)
ERROR: TypeInstabilityError: Instability detected in `f`
defined at REPL[4]:1 with arguments `(Int64,)`. Inferred
to be `Any`, which is not a concrete type.

```

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