# Chained keyword assignment in function call leaks scope

**URL:** https://discourse.julialang.org/t/chained-keyword-assignment-in-function-call-leaks-scope/126531
**Category:** General Usage
**Tags:** function, chain, assignment
**Created:** [March 4, 2025, 2:51pm UTC](https://discourse.julialang.org/t/chained-keyword-assignment-in-function-call-leaks-scope/126531 "2025-03-04T14:51:34Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![ncxst](https://avatars.discourse-cdn.com/v4/letter/n/e47774/32.png) [@ncxst](https://discourse.julialang.org/u/ncxst)
#### Post date: [March 4, 2025, 2:51pm UTC](https://discourse.julialang.org/t/chained-keyword-assignment-in-function-call-leaks-scope/126531/1 "2025-03-04T14:51:34Z")

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I tried to do a chained keyword assignment in a function call and got the following behavior

```julia
julia> function params(;kwargs...)
           for kw in kwargs
               println(kw)
           end
       end
params (generic function with 1 method)

julia> params(a=b=1)
:a => 1

julia> a
ERROR: UndefVarError: `a` not defined in `Main`
Suggestion: check for spelling errors or missing imports.

julia> b
1

```

I would have expected the `paprams`-function to print `a` and `b` or julia giving an error when called that way. The reason why I expeted this behavior is that I think of `a=b=1` to be equivalent to `a=1; b=1`.  
But what actually happens, is that the variable `b` now lives in the scope in which the function was called and only `a` is passed as a keyword argument to the function.  
Can someone please explain why this is happening.

---

<div class="post-metadata">

### Author: ![StefanKarpinski](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stefankarpinski/32/24_2.png) [@StefanKarpinski](https://discourse.julialang.org/u/StefanKarpinski)
#### Post date: [March 4, 2025, 3:29pm UTC](https://discourse.julialang.org/t/chained-keyword-assignment-in-function-call-leaks-scope/126531/2 "2025-03-04T15:29:08Z")

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There is no chained keyword argument syntax. When you write `params(a=b=1)` it means `params(a=(b=1))` which is equivalent to doing `b=1; params(a=1)`. There is no syntax error because the value of a keyword can be an arbitrary expression and since Julia is an [expression-oriented language](https://en.wikipedia.org/wiki/Expression-oriented_programming_language), everything is an expression, including assignments like `b=1`. This is the kind of thing a syntax linting tool could warn you about though.