Union all Types

General Usage
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1 
Pair{Symbol,Number}

Would be a nice short-hand for

Pair{Symbol,T} where T<:Number

is there a reason it can’t be written like this?
it would be nice to write


f(x::Pair{Symbol,Number}) = 1

instead of

f(x::Pair{Symbol,T}) where T<:Number = 1
2

One can’t be a shorthand for the other because they mean different things. It comes down to the same thing that’s explained here: Types · The Julia Language where Point{Real} is not the same as Point{T} where {T <: Real} because a Point{Int} is not a subtype of Point{Real}. LIkewise a Pair{Symbol, Float64} is not a subtype of Point{Symbol, Number}; they’re actually distinct types.

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3

Thanks. That link gives a shorthand:

f(x::Pair{Symbol,<:Number}) = 1
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