# Understanding the output of @code\_warntype

**URL:** <https://discourse.julialang.org/t/understanding-the-output-of-code-warntype/123191>\
**Category:** New to Julia\
**Tags:** code\_warntype, type-stability\
**Created:** [November 27, 2024, 11:37pm UTC](https://discourse.julialang.org/t/understanding-the-output-of-code-warntype/123191 "2024-11-27T23:37:22Z")\
**Posts on this page:** 1\
**Showing post:** 4

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**Author:** ![Benny](https://avatars.discourse-cdn.com/v4/letter/b/49beb7/32.png) [@Benny](https://discourse.julialang.org/u/Benny)\
**Post date:** [November 28, 2024, 12:06am UTC](https://discourse.julialang.org/t/understanding-the-output-of-code-warntype/123191/4 "2024-11-28T00:06:35Z")

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That’s just an underlying iteration variable’s type inference. When the iterable runs out of elements, it has a value of `nothing`. In general you don’t have to worry about inferences of 2-3 element `Union`s, especially if they don’t propagate into larger ones or `Any` via multiple arguments in function calls. The compiler just duplicates the code into 2-3 type-stable branches if needed.

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