# How is it that new Julia programmers tend to abuse type annotations?

**URL:** https://discourse.julialang.org/t/how-is-it-that-new-julia-programmers-tend-to-abuse-type-annotations/108465
**Category:** Teaching & Outreach
**Created:** [January 7, 2024, 1:40pm UTC](https://discourse.julialang.org/t/how-is-it-that-new-julia-programmers-tend-to-abuse-type-annotations/108465 "2024-01-07T13:40:01Z")
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### Author: ![stevengj](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stevengj/32/71_2.png) [@stevengj](https://discourse.julialang.org/u/stevengj)
#### Post date: [January 12, 2024, 10:52pm UTC](https://discourse.julialang.org/t/how-is-it-that-new-julia-programmers-tend-to-abuse-type-annotations/108465/82 "2024-01-12T22:52:38Z")

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> [@FHell](#):
>
> I really don’t want anyone to be able to create a method for map that does not have this signature.  
> The fact that the Julia type system does not allow these things, which many other type systems do, means people who want to do these things end up “misusing” it in the sense discussed here.

\* “many other type systems” in static languages. Julia is not a statically typed language. If you want every function call to be checked statically, you maybe don’t want a dynamically typed language at all. Which is fine!

> [@FHell](#):
>
> Callable[T,T’],

For discussion of this kind of thing in Julia, see also [Towards typed lambdas by carnaval · Pull Request #10269 · JuliaLang/julia · GitHub](https://github.com/JuliaLang/julia/pull/10269) and @JeffBezanson’s [thesis](https://dspace.mit.edu/handle/1721.1/74897) discussion of [arrow types](https://en.wikipedia.org/wiki/Arrow_%28computer_science%29) in chapter 4.

See also the many past discussions of things like [Why doesn't Julia allow multiple inheritance? - #4 by andyferris](https://discourse.julialang.org/t/why-doesnt-julia-allow-multiple-inheritance/14342/4) and [Interfaces for Abstract Types · Issue #6975 · JuliaLang/julia · GitHub](https://github.com/JuliaLang/julia/issues/6975)

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