redefinition of typealias raises error


Hi all,

I am trying to define a type alias for a parametric type. Unfortuntately, when running the same line of code again, I get an error “invalid redefinition of constant …”. While that is generally okai (it’s constant so I don’t want o change it ^^) it’s a bit annoying when rerunning a script in the same itnerpreter to avoid the startup time of Julia (roughly 30 seconds for my particular script).

Here is a minimal not working example. How can I avoid that the second line raises and error?

julia> MyUnion{A, B} = Union{A,B}
Union{A, B} where B where A

julia> MyUnion{A, B} = Union{A,B}
ERROR: invalid redefinition of constant MyUnion



FWIW works on 0.7.

As a workaround, you can wrap your code in a module and then the inclusion should work fine.

When it comes to hotloading code, you definitely need to check out


ok, thanks. When is Julia 0.7 likely to come out? And is there a beta already for testing it? I used conda to install julia, so maybe there is a conda channel for that?

Thanks for the workaround, works like a charm. And Revise.jl looks awesome, I’ll be trying it out these days.


There are nightlies available to download from but you should know that not many packages support it and it is still changing a bit (not too big things right now though).

An alpha should be out in not too long time :wink:


haha, so asking for a beta was a bit too much (:

thanks anyway, I’ll stay with my safe 0.6 :sunny: