# Reflections on an typo (getindex(::NamedTuple, ...))

**URL:** <https://discourse.julialang.org/t/reflections-on-an-typo-getindex-namedtuple/133331>\
**Category:** General Usage\
**Tags:** question, destructuring\
**Created:** [October 21, 2025, 1:20pm UTC](https://discourse.julialang.org/t/reflections-on-an-typo-getindex-namedtuple/133331 "2025-10-21T13:20:26Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Tamas\_Papp](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tamas_papp/32/25949_2.png) [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Post date:** [October 21, 2025, 1:20pm UTC](https://discourse.julialang.org/t/reflections-on-an-typo-getindex-namedtuple/133331/1 "2025-10-21T13:20:26Z")

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I have recently finished debugging some code, with an error deep inside a calculation that wasted me a few hours. I wish to emphasize that this is _not a bug in Julia_. **It is my error.**

But, as you will see below, I can envision it happening again as it is a simple typo, and I would appreciate advice on good practices that would help me avoid or at least notice it.

For an MWE, consider

```julia
calculate_intermediate(x) = (; a = x, b = x + 1, c = x + 2, d = x + 3)

function calculate_final(x)
    (c, d) = calculate_intermediate(x) # <= ERROR HERE
    c + d
end

```

Now what I meant to write is `(; c, d)`, not `(c, d)`, which gave me `(a, b)` instead.

My first reaction was that “`::NamedTuple` should not have `getindex`”. But that’s like blaming a knife for cutting your hand, and from a practical perspective, now it is like that, and it remains in the language, so that discussions avoid it are pretty pointless.

A destructuring macro (like various `@unpack` implementations) could refuse to use `getindex` on a rvalue that supports has nonempty `propertynames`, unless some special syntax is used to signal that the user really means it. But I am still not sure that it is the right way.

Comments welcome.

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**Author:** ![Sevi](https://avatars.discourse-cdn.com/v4/letter/s/c67d28/32.png) [@Sevi](https://discourse.julialang.org/u/Sevi)\
**Post date:** [October 21, 2025, 1:42pm UTC](https://discourse.julialang.org/t/reflections-on-an-typo-getindex-namedtuple/133331/2 "2025-10-21T13:42:42Z")

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It’s definitely an easy thing to overlook. I really like that NamedTuples can be unpacked with `(; ...)`, but it is a double-edged sword that “regular” unpacking of the ordered elements also works. For me this particular typo is right up there with forgetting a trailing comma when creating tuples with a single element (`(x)` instead of `(x,)`) and forgetting to iterate over a range instead of a single number (`for i in n ...` instead of `for i in 1:n`). They kind of look as though they mean the right thing and (mostly) don’t make the program complain immediately. But ultimately it’s something that my eyes get used to after making the mistake often enough.

Not sure if there is a way to avoid that kind of typo through some automatic checks… one heuristic for a linter might be that it’s unlikely someone wants to use the “un-named” destructuring with parentheses. E.g. in your example `(c, d) = mytuple` is likely a typo since it could have just been `c, d = mytuple`. But this criterion is probably too dependent on individual style preferences and in principle there’s nothing wrong with `(c, d) = mytuple`…

A macro sounds useful, but you still have to remember to use it, which to me is very similar to remembering the semicolon in the first place 🤷

PS: I wonder what NamedTuples would be without `getindex` – basically nothing more than anonymous structs?

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**Author:** ![abraunst](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/abraunst/32/6880_2.png) [@abraunst](https://discourse.julialang.org/u/abraunst)\
**Post date:** [October 22, 2025, 8:33am UTC](https://discourse.julialang.org/t/reflections-on-an-typo-getindex-namedtuple/133331/3 "2025-10-22T08:33:22Z")

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Maybe a linter could check if the variable names exist in the named tuple but in a different position…

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**Author:** ![Sevi](https://avatars.discourse-cdn.com/v4/letter/s/c67d28/32.png) [@Sevi](https://discourse.julialang.org/u/Sevi)\
**Post date:** [October 22, 2025, 8:36am UTC](https://discourse.julialang.org/t/reflections-on-an-typo-getindex-namedtuple/133331/4 "2025-10-22T08:36:41Z")

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But that would require runtime information, right? Not sure how the linter would figure out what comes out of `calculate_intermediate(x)` (unless there is only one method like in the example above). But I also don’t know much about linters and how they typically operate 😅

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**Author:** ![abraunst](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/abraunst/32/6880_2.png) [@abraunst](https://discourse.julialang.org/u/abraunst)\
**Post date:** [October 22, 2025, 8:38am UTC](https://discourse.julialang.org/t/reflections-on-an-typo-getindex-namedtuple/133331/5 "2025-10-22T08:38:57Z")

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yeah, you’re probably right (don’t know much about linters either 😅 )