Error in computing cartesian product with @relation

[kris-brown]

I'm noticing an error message when I evaluate certain queries - I suspect that it's related to not having any foreign keys, but I'd appreciate any insight you have into why this is happening.

MWE

using Catlab.Programs
using Catlab.Theories
using Catlab.Present
using Catlab.CategoricalAlgebra
using Catlab.WiringDiagrams

@present T(FreeSchema) begin
    V::Ob
end

T_inst = ACSetType(T)()
add_parts!(T_inst,:V, 2)

rel = @relation (V=v1,V=v2) begin
 V(_id=v1)
 V(_id=v2)
end

query(T_inst, rel)

Error

LoadError: MethodError: no method matching Limit(::Catlab.CSetDataStructures.AttributedCSet{Catlab.Theories.CatDesc{(:V₁, :V₂, :E), (:src, :tgt), (3, 3), (1, 2)}, Catlab.Theories.AttrDesc{Catlab.Theories.CatDesc{(:V₁, :V₂, :E), (:src, :tgt), (3, 3), (1, 2)}, (:Ob, :Hom), (:ob₁, :ob₂, :hom), (1, 2, 3), (1, 1, 2)}, Tuple{Catlab.CategoricalAlgebra.Sets.SetOb, Catlab.CategoricalAlgebra.Sets.SetFunction{Dom, Codom} where {Dom<:(Catlab.CategoricalAlgebra.FinSets.FinSet{Int64, T} where T), Codom}}, (:src, :tgt), (), NamedTuple{(:V₁, :V₂, :E), Tuple{TypedTables.Table{NamedTuple{(:ob₁,), Tuple{Catlab.CategoricalAlgebra.Sets.SetOb}}, 1, NamedTuple{(:ob₁,), Tuple{Vector{Catlab.CategoricalAlgebra.Sets.SetOb}}}}, TypedTables.Table{NamedTuple{(:ob₂,), Tuple{Catlab.CategoricalAlgebra.Sets.SetOb}}, 1, NamedTuple{(:ob₂,), Tuple{Vector{Catlab.CategoricalAlgebra.Sets.SetOb}}}}, TypedTables.Table{NamedTuple{(:src, :tgt, :hom), Tuple{Int64, Int64, Catlab.CategoricalAlgebra.Sets.SetFunction{Dom, Codom} where {Dom<:(Catlab.CategoricalAlgebra.FinSets.FinSet{Int64, T} where T), Codom}}}, 1, NamedTuple{(:src, :tgt, :hom), Tuple{Vector{Int64}, Vector{Int64}, Vector{Catlab.CategoricalAlgebra.Sets.SetFunction{Dom, Codom} where {Dom<:(Catlab.CategoricalAlgebra.FinSets.FinSet{Int64, T} where T), Codom}}}}}}}, NamedTuple{(:src, :tgt), Tuple{Vector{Vector{Int64}}, Vector{Vector{Int64}}}}}, ::StaticArrays.SVector{2, Catlab.CategoricalAlgebra.Sets.SetFunctionCallable{Int64, Int64, Catlab.CategoricalAlgebra.FinSets.FinSet{Int64, Int64}, Catlab.CategoricalAlgebra.FinSets.FinSet{Int64, Int64}}})
Closest candidates are:
  Limit(::Diagram, ::Cone) where {Ob, Diagram, Cone<:(Multispan{Ob, Hom, Legs} where {Hom, Legs<:AbstractVector{Hom}})} at /Users/ksb/Catlab.jl/src/categorical_algebra/Limits.jl:48

[epatters]

Thanks for the report Kris. Note that the @relation should be:

rel = @relation (v1=v1,v2=v2) begin
 V(_id=v1)
 V(_id=v2)
end

However, there is definitely still a bug here!