typeintersect Vararg aborts

[vtjnash]

this is not good:

julia> typeintersect(Vararg{Int}, Int)
julia: /data/vtjnash/julia/src/subtype.c:1261: subtype: Assertion `!jl_is_vararg(x) && !jl_is_vararg(y)' failed.

signal (6): Aborted

and other mild oddities (I think these are correct, since they can appear as type parameters, they should be valid as arguments also)

julia> typeintersect(1, 2)
Union{}

julia> typeintersect(1, 1)
1

julia> typeintersect(1, Any)
1

julia> typeintersect(Any, 1)
1

[Keno]

Well, Vararg{Int} isn't really a type. We've been moving away from just allowing arbitrary values in typeintersect. I mean, it probably shouldn't abort, but passing in Vararg{Int} is probably a bug in the caller.

[aviatesk]

Maybe we want to do some assertions on Julia level?

[Moelf]

looks like it no longer crashes on master

julia> typeintersect(Vararg{Int}, Int)
Union{}

[aviatesk]

You need to have assert build to repro this.

[Moelf]

I see. as for adding checks on the Julia side, is this too naive/hacky?

function typeintersect(@nospecialize(a), @nospecialize(b))
    @_pure_meta
    if typeof(a) !== DataType
        throw(TypeError(:typeintersect, DataType, a))
    elseif typeof(b) !== DataType
        throw(TypeError(:typeintersect, DataType, b))
    end
    ccall(:jl_type_intersection, Any, (Any, Any), a, b)
emd

[JeffBezanson]

Checking a isa Type might be ok.

[Moelf]

😅 right; I see @aviatesk has done this on the C side in his branch so I won't make a PR.