Ambiguous methods for supports_constraint

[matbesancon]

The following happened when testing Dualization with MOI v0.9:

structures: Error During Test at /home/mbesancon/.julia/dev/Dualization/test/Tests/test_structures.jl:1
  Got exception outside of a @test
  MethodError: supports_constraint(::TestModel{Float64}, ::Type{MathOptInterface.SingleVariable}, ::Type{MathOptInterface.GreaterThan{Float64}}) is ambiguous. Candidates:
    supports_constraint(model::TestModel{#13#T}, ::Type{#s915} where #s915<:Union{MathOptInterface.SingleVariable, MathOptInterface.ScalarAffineFunction{#13#T}, MathOptInterface.ScalarQuadraticFunction{#13#T}}, ::Type{#s916} where #s916<:Union{MathOptInterface.Integer, MathOptInterface.ZeroOne, MathOptInterface.EqualTo{#13#T}, MathOptInterface.GreaterThan{#13#T}, MathOptInterface.Interval{#13#T}, MathOptInterface.LessThan{#13#T}, MathOptInterface.Semicontinuous{#13#T}, MathOptInterface.Semiinteger{#13#T}}) where #13#T in Main at /home/mbesancon/.julia/packages/MathOptInterface/016Ol/src/Utilities/model.jl:997
    supports_constraint(::MathOptInterface.Utilities.AbstractModel{T}, ::Type{MathOptInterface.SingleVariable}, ::Type{#s109} where #s109<:Union{MathOptInterface.Integer, MathOptInterface.ZeroOne, MathOptInterface.EqualTo{T}, MathOptInterface.GreaterThan{T}, MathOptInterface.Interval{T}, MathOptInterface.LessThan{T}}) where T in MathOptInterface.Utilities at /home/mbesancon/.julia/packages/MathOptInterface/016Ol/src/Utilities/model.jl:469
  Possible fix, define
    supports_constraint(::TestModel{T}, ::Type{MathOptInterface.SingleVariable}, ::Type{#s109} where #s109<:Union{MathOptInterface.Integer, MathOptInterface.ZeroOne, MathOptInterface.EqualTo{T}, MathOptInterface.GreaterThan{T}, MathOptInterface.Interval{T}, MathOptInterface.LessThan{T}})
  Stacktrace:
   [1] add_constraint(::TestModel{Float64}, ::MathOptInterface.SingleVariable, ::MathOptInterface.GreaterThan{Float64}) at /home/mbesancon/.julia/packages/MathOptInterface/016Ol/src/Utilities/model.jl:473
   [2] lp1_test() at /home/mbesancon/.julia/dev/Dualization/test/Problems/Linear/linear_problems.jl:18
   [3] top-level scope at /home/mbesancon/.julia/dev/Dualization/test/Tests/test_structures.jl:8
   [4] top-level scope at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.2/Test/src/Test.jl:1113
   [5] top-level scope at /home/mbesancon/.julia/dev/Dualization/test/Tests/test_structures.jl:2

[matbesancon]

Status:

(Dualization) pkg> st
Project Dualization v0.1.0
    Status `~/.julia/dev/Dualization/Project.toml`
  [4076af6c] + JuMP v0.20.0
  [b8f27783] + MathOptInterface v0.9.1
    Status `~/.julia/dev/Dualization/Manifest.toml`
  [4076af6c] + JuMP v0.20.0
  [b8f27783] + MathOptInterface v0.9.1

[ericphanson]

I am no MOI expert, but I had a similar ambiguity error, and @blegat directed me to #736, saying to remove MOI.SingleVariable from the @model macro, or just use MOI.Utilities.Model instead of the @model macro. I ended up going for MOI.Utilities.Model, seems to work well.

[matbesancon]

Thanks I'll try this

[KristofferC]

This came up when testing this package for 1.3:

Unslack: Error During Test at /root/.julia/packages/MathOptInterface/WXD0G/test/Bridges/lazy_bridge_optimizer.jl:472
  Test threw exception
  Expression: MOI.supports_constraint(full_bridged_no_variable, MOI.SingleVariable, S)
  MethodError: supports_constraint(::NoVariableModel{Float64}, ::Type{MathOptInterface.SingleVariable}, ::Type{MathOptInterface.LessThan{Float64}}) is ambiguous. Candidates:
    supports_constraint(::MathOptInterface.Utilities.AbstractModel{T}, ::Type{MathOptInterface.SingleVariable}, ::Type{#s110} where #s110<:Union{MathOptInterface.Integer, MathOptInterface.ZeroOne, MathOptInterface.EqualTo{T}, MathOptInterface.GreaterThan{T}, MathOptInterface.Interval{T}, MathOptInterface.LessThan{T}, MathOptInterface.Semicontinuous{T}, MathOptInterface.Semiinteger{T}}) where T in MathOptInterface.Utilities at /root/.julia/packages/MathOptInterface/WXD0G/src/Utilities/model.jl:482
    supports_constraint(::NoVariableModel, ::Type{MathOptInterface.SingleVariable}, ::Type{#s958} where #s958<:MathOptInterface.AbstractScalarSet) in Main at /root/.julia/packages/MathOptInterface/WXD0G/test/Bridges/lazy_bridge_optimizer.jl:256
  Possible fix, define
    supports_constraint(::NoVariableModel{T}, ::Type{MathOptInterface.SingleVariable}, ::Type{#s958} where #s958<:MathOptInterface.AbstractScalarSet)

[blegat]

@matbesancon I believe this is indeed because you included MOI.SingleVariable in MOIU.Model.
@KristofferC Indeed, that's an ambiguity, good to see improvements in the Julia type system.