SumOfSquares error in inference

[vtjnash]

Looking at the segfault in https://s3.amazonaws.com/julialang-reports/nanosoldier/pkgeval/by_date/2025-03/18/SumOfSquares.primary.log, inference is coming to the wrong answer on master

julia> using MathOptInterface, MutableArithmetics, MultivariateMoments

julia> code_typed(MutableArithmetics.promote_operation, Tuple{typeof(MultivariateMoments.:+), Type{MathOptInterface.VariableIndex}, Type{MathOptInterface.ScalarAffineFunction{Complex{Float64}}} where _A}, optimize=false)
[ Warning: + is defined in Base and is not public in MultivariateMoments
1-element Vector{Any}:
 CodeInfo(
    @ /home/vtjnash/.julia/packages/MathOptInterface/jGuEH/src/Utilities/mutable_arithmetics.jl:90 within `unknown scope`
1 ─ %1 = MathOptInterface.Utilities.promote_operation::Core.Const(MathOptInterface.Utilities.promote_operation)
│   %2 = $(Expr(:static_parameter, 1))::Core.Const(ComplexF64)
│   %3 =   dynamic (%1)(op, %2, F, G)::Core.Const(MathOptInterface.ScalarAffineFunction{ComplexF64})
└──      return %3
) => Type{MathOptInterface.ScalarAffineFunction{ComplexF64}}

julia> code_typed(MutableArithmetics.promote_operation, Tuple{typeof(MultivariateMoments.:+), Type{MathOptInterface.VariableIndex}, Type{MathOptInterface.ScalarAffineFunction{Complex{_A}}} where _A}, optimize=false)
1-element Vector{Any}:
 CodeInfo(
    @ /home/vtjnash/.julia/packages/MathOptInterface/jGuEH/src/Utilities/mutable_arithmetics.jl:90 within `unknown scope`
1 ─ %1 = MathOptInterface.Utilities.promote_operation::Core.Const(MathOptInterface.Utilities.promote_operation)
│   %2 = $(Expr(:static_parameter, 1))::Type{T} where T<:(Complex{_A} where _A)
│          dynamic (%1)(op, %2, F, G)::Union{}
└──      Core.Const(:(return %3))::Union{}
) => Union{}

on v1.12 this was

julia> code_typed(MutableArithmetics.promote_operation, Tuple{typeof(MultivariateMoments.:+), Type{MathOptInterface.VariableIndex}, Type{MathOptInterface.ScalarAffineFunction{Complex{_A}}} where _A}, optimize=false)
1-element Vector{Any}:
 CodeInfo(
    @ /home/vtjnash/.julia/packages/MathOptInterface/jGuEH/src/Utilities/mutable_arithmetics.jl:90 within `unknown scope`
1 ─ %1 = MathOptInterface.Utilities.promote_operation::Core.Const(MathOptInterface.Utilities.promote_operation)
│   %2 = $(Expr(:static_parameter, 1))::Type{T} where T<:(Complex{_A} where _A)
│   %3 =   dynamic (%1)(op, %2, F, G)::Type{MathOptInterface.ScalarAffineFunction{Complex{_A}}} where _A
└──      return %3
) => Type{MathOptInterface.ScalarAffineFunction{Complex{_A}}} where _A

[vtjnash]

Actually, only a slight tweak is needed to the MWE to make it fail on v1.12 and v1.11 too. Somehow inference is reporting there are no possible methods to call, and so inlining is replacing the dynamic dispatch call with Core.throw_methoderror, even though there seems no sane reason for doing that (there is in fact exactly one method matching)

julia> code_typed(MutableArithmetics.promote_operation, Tuple{typeof(MultivariateMoments.:+), Type{Complex{T}} where T, Type{MathOptInterface.VariableIndex}}, optimize=false)
1-element Vector{Any}:
 CodeInfo(
    @ /home/vtjnash/.julia/packages/MathOptInterface/jGuEH/src/Utilities/mutable_arithmetics.jl:122 within `unknown scope`
1 ─ %1 = MathOptInterface.Utilities.promote_operation::Core.Const(MathOptInterface.Utilities.promote_operation)
│          dynamic (%1)(op, F, F, G)::Union{}
└──      Core.Const(:(return %2))::Union{}
) => Union{}

julia> code_typed(MutableArithmetics.promote_operation, Tuple{typeof(MultivariateMoments.:+), Type{Complex{T}} where T, Type{MathOptInterface.VariableIndex}}, optimize=true)
1-element Vector{Any}:
 CodeInfo(
    @ /home/vtjnash/.julia/packages/MathOptInterface/jGuEH/src/Utilities/mutable_arithmetics.jl:122 within `promote_operation`
1 ─       builtin Core.throw_methoderror(MathOptInterface.Utilities.promote_operation, op, F, F, G)::Union{}
└──     unreachable
) => Union{}

[vtjnash]

Oh, amazing, this packages uses two different functions of the same name in different modules and has them call into each other. Here's the real method call which failed in type-intersection:

julia> methods(MathOptInterface.Utilities.promote_operation, Tuple{typeof(+), Type{Complex{Float64}}, Type{Complex{Float64}} where T, Type{MathOptInterface.VariableIndex}})
# 1 method for generic function "promote_operation" from MathOptInterface.Utilities:
 [1] promote_operation(::Union{typeof(+), typeof(-)}, ::Type{T}, ::Type{<:F}, ::Type{<:F}) where {T, F<:Union{MathOptInterface.VariableIndex, MathOptInterface.ScalarAffineFunction{T}, T}}
     @ ~/.julia/packages/MathOptInterface/jGuEH/src/Utilities/promote_operation.jl:70

julia> methods(MathOptInterface.Utilities.promote_operation, Tuple{typeof(+), Type{Complex{T}} where T, Type{Complex{T}} where T, Type{MathOptInterface.VariableIndex}})
# 0 methods for generic function "promote_operation" from MathOptInterface.Utilities

This intersection mistake was introduced in v1.7:

julia> A = Tuple{Type{T}, Type{<:F}, Type{<:F}} where {T, F<:Union{String, T}}
Tuple{Type{T}, Type{<:F}, Type{<:F}} where {T, F<:Union{String, T}}

julia> typeintersect(A, Tuple{Type{Complex{T}} where T, Type{Complex{T}} where T, Type{String}})
Union{} # wrong
# previously correct answer was Tuple{Type{Complex{T}}, Type{Complex{T}}, Type{String}} where T

julia> typeintersect(A, Tuple{Type{Complex{Float64}} where T, Type{Complex{Float64}} where T, Type{String}})
Tuple{Type{ComplexF64}, Type{ComplexF64}, Type{String}} # proof-by-counter-example