`Method overwritten` warnings, take 2

[mauro3]

PR #5 fixed most of the method overwritten warnings, but not all:

julia> @traitfn g{X; Tr{X}}(x::X) = 1
g (generic function with 2 methods)

julia> @traitfn g{X; !Tr{X}}(::X) = 2
WARNING: Method definition g(#X<:Any) in module Main at /home/mauro/.julia/v0.5/SimpleTraits/src/SimpleTraits.jl:160 overwritten at /home/mauro/.julia/v0.5/SimpleTraits/src/SimpleTraits.jl:160.
g (generic function with 3 methods)

julia> g(5)
1

julia> g(5.0)
2

If this becomes fixable at some stage without too much effort/code, then fix.

[mauro3]

With the traitor syntax this will be hit more often as the type often gets gensym'ed:

julia> @traitfn f(a::::Tr) = a
f (generic function with 2 methods)

julia> @traitfn f(a::::(!Tr)) = -a
WARNING: Method definition f(###272<:Any) in module Main at /home/mauro/.julia/v0.5/SimpleTraits/src/SimpleTraits.jl:239 overwritten at /home/mauro/.julia/v0.5/SimpleTraits/src/SimpleTraits.jl:239.
f (generic function with 3 methods)

Edit: this is now fixed but above still not.

[juliohm]

We are hitting this issue in Meshes.jl, any idea on how to solve it in Julia v1.5 and beyond?

[juliohm]

@mauro3 is there another way to express the same thing that would avoid the warning? I was assuming that this was a quite common pattern.

[timholy]

The way to fix this is to clearly separate the "trait depot" function from the dispatched handlers. Create the depot only once. That means folks have to agree on the traits they want.

[juliohm]

I am not sure I understand the comment @timholy can you clarify with an example? This is the code that is producing the warning in our case: https://github.com/JuliaGeometry/Meshes.jl/blob/11e2ba938b2bfb6cb4e3d74bddab2752917e8f54/src/viewing.jl#L62-L64

We agreed on the IsGrid as a temporary trait while we refine the traits in the package. It indicates domains that behave like a CartesianGrid, Image, etc. How to modify that code to avoid the warning?

[juliohm]

The solution consisted of giving the argument the same name: JuliaGeometry/Meshes.jl#110