# Inference on field types?

**URL:** <https://discourse.julialang.org/t/inference-on-field-types/53448>\
**Category:** Performance\
**Tags:** inference\
**Created:** [January 16, 2021, 7:55pm UTC](https://discourse.julialang.org/t/inference-on-field-types/53448 "2021-01-16T19:55:12Z")\
**Posts on this page:** 1\
**Showing post:** 11

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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:** [January 18, 2021, 12:47am UTC](https://discourse.julialang.org/t/inference-on-field-types/53448/11 "2021-01-18T00:47:38Z")

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I looked it up, [`Symbol` and `Tuple`s of `Symbol`s are](https://discourse.julialang.org/t/how-to-use-a-type-wrapping-a-symbol-as-a-type-parameter/19628/6) [_hard-coded exceptions_ to the isbitstype parameter rule](https://github.com/JuliaLang/julia/blob/7772486a6942c9a9b52849b6ffe690a7da5861cd/src/builtins.c#L825-L843), very interesting.

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