Fixing type piracy is becoming more urgent

[KristofferC]

The type piracy in

Convex.jl/src/atoms/affine/stack.jl

Lines 111 to 120 in c6a21df

	# TODO: fix piracy!
	# * `Value` is not owned by Convex.jl
	# * splatting creates zero-argument functions, which again are not owned by Convex.jl
	hcat(args::AbstractExpr...) = HcatAtom(args...)
	function hcat(args::AbstractExprOrValue...)
	return HcatAtom(map(arg -> convert(AbstractExpr, arg), args)...)
	end
	hcat(args::Value...) = Base.cat(args..., dims = Val(2))

causes the package to now error on the 1.10 backport branch https://s3.amazonaws.com/julialang-reports/nanosoldier/pkgeval/by_hash/4e1759c_vs_0ba6ec2/EnsembleKalmanProcesses.primary.log

Failed to precompile Convex [f65535da-76fb-5f13-bab9-19810c17039a] to "/home/pkgeval/.julia/compiled/v1.10/Convex/jl_CmPZEd".
WARNING: Method definition hcat(Union{Number, AbstractArray{T, N} where N where T}...) in module Base at abstractarray.jl:1995 overwritten in module Convex at /home/pkgeval/.julia/packages/Convex/tSTAW/src/atoms/affine/stack.jl:120.
ERROR: LoadError: Method overwriting is not permitted during Module precompile.
Stacktrace:
 [1] top-level scope
   @ ~/.julia/packages/Convex/tSTAW/src/atoms/affine/stack.jl:120

[odow]

Method overwriting is not permitted during Module precompile.

This seems like it is a breaking change to Julia then?

[KristofferC]

Hm, I don't think so because this should have already printed that this type of method overwriting already is a fatal error, it just didn't hard error for it.

[odow]

One issue with fixing this is that it would likely require a breaking change to Convex.jl (e.g., replacing Base.hcat with Convex.hcat), but https://github.com/jump-dev/Convex.jl#please-read-convexjl-needs-a-new-maintainer.

I guess we have no choice though.

[KristofferC]

But isn't the solution here to instead of writing

 hcat(args::Value...) = Base.cat(args..., dims = Val(2)) 

to write something like

 hcat(arg::Value, args::Value...) = Base.cat((arg, args...)..., dims = Val(2)) 

or?

[odow]

The issue is:

Convex.jl/src/expressions.jl

Line 93 in c6a21df

const Value = Union{Number,AbstractArray}

hcat(arg::Value, args::Value...) might fix that exact method, but it's still piracy.

[odow]

@blegat asks: why is hcat(args::Value...) = Base.cat(args..., dims = Val(2)) even needed?