# A question about co/countervariance: \`f((x, y)::Tuple{Int, Any}) = 1\`

**URL:** <https://discourse.julialang.org/t/a-question-about-co-countervariance-f-x-y-tuple-int-any-1/56332>\
**Category:** General Usage\
**Created:** [March 2, 2021, 1:25pm UTC](https://discourse.julialang.org/t/a-question-about-co-countervariance-f-x-y-tuple-int-any-1/56332 "2021-03-02T13:25:33Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![BridgeBot](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/bridgebot/32/21491_2.png) [@BridgeBot](https://discourse.julialang.org/u/BridgeBot)\
**Post date:** [March 2, 2021, 1:25pm UTC](https://discourse.julialang.org/t/a-question-about-co-countervariance-f-x-y-tuple-int-any-1/56332/1 "2021-03-02T13:25:33Z")

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A question about co/countervariance:

```julia
julia> f((x, y)::Tuple{Int, Any}) = 1
f (generic function with 1 method)

julia> f((1,1))
1

julia> f((x, y)::Pair{Int, Any}) = 1
f (generic function with 2 methods)

julia> f((1=>1))
ERROR: MethodError: no method matching f(::Pair{Int64,Int64})

```

Are tuples special in this regard?

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**Author:** ![mschauer](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mschauer/32/13946_2.png) [@mschauer](https://discourse.julialang.org/u/mschauer)\
**Post date:** [March 2, 2021, 1:27pm UTC](https://discourse.julialang.org/t/a-question-about-co-countervariance-f-x-y-tuple-int-any-1/56332/2 "2021-03-02T13:27:34Z")

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@jakobnissen

> Yes, they are

@mschauer

> Thanks, I think I just understood something important