Ambiguity error for DynamicalDDEProblem

[SebastianM-C]

Running

using Test
using SciMLBase

problems = detect_ambiguities(SciMLBase)

gives

8-element Vector{Tuple{Method, Method}}:
 (DynamicalDDEProblem(f::DynamicalDDEFunction, h, tspan) in SciMLBase at C:\Users\sebastian\.julia\dev\SciMLBase\src\problems\dde_problems.jl:77, DynamicalDDEProblem(f1::Function, f2::Function, args...; kwargs...) in SciMLBase at C:\Users\sebastian\.julia\dev\SciMLBase\src\problems\dde_problems.jl:80)
 (DynamicalDDEProblem(f::DynamicalDDEFunction, h, tspan, p; kwargs...) in SciMLBase at C:\Users\sebastian\.julia\dev\SciMLBase\src\problems\dde_problems.jl:77, DynamicalDDEProblem(f1::Function, f2::Function, args...; kwargs...) in SciMLBase at C:\Users\sebastian\.julia\dev\SciMLBase\src\problems\dde_problems.jl:80)
 ((var"#s255"::Core.var"#Type##kw")(::Any, ::Type{DynamicalDDEProblem}, f::DynamicalDDEFunction, h, tspan, p) in SciMLBase at C:\Users\sebastian\.julia\dev\SciMLBase\src\problems\dde_problems.jl:77, (::Core.var"#Type##kw")(::Any, ::Type{DynamicalDDEProblem}, f1::Function, f2::Function, args...) in SciMLBase at C:\Users\sebastian\.julia\dev\SciMLBase\src\problems\dde_problems.jl:80)
 (DynamicalDDEProblem(f::DynamicalDDEFunction, v0, u0, h, tspan, p; dependent_lags, kwargs...) in SciMLBase at C:\Users\sebastian\.julia\dev\SciMLBase\src\problems\dde_problems.jl:71, DynamicalDDEProblem(f1::Function, f2::Function, args...; kwargs...) in SciMLBase at C:\Users\sebastian\.julia\dev\SciMLBase\src\problems\dde_problems.jl:80)
 (DynamicalDDEProblem(f::DynamicalDDEFunction, v0, u0, h, tspan) in SciMLBase at C:\Users\sebastian\.julia\dev\SciMLBase\src\problems\dde_problems.jl:71, DynamicalDDEProblem(f1::Function, f2::Function, args...; kwargs...) in SciMLBase at C:\Users\sebastian\.julia\dev\SciMLBase\src\problems\dde_problems.jl:80)
 ((var"#s255"::Core.var"#Type##kw")(::Any, ::Type{DynamicalDDEProblem}, f::DynamicalDDEFunction, v0, u0, h, tspan) in SciMLBase at C:\Users\sebastian\.julia\dev\SciMLBase\src\problems\dde_problems.jl:71, (::Core.var"#Type##kw")(::Any, ::Type{DynamicalDDEProblem}, f1::Function, f2::Function, args...) in SciMLBase at C:\Users\sebastian\.julia\dev\SciMLBase\src\problems\dde_problems.jl:80)
 ((var"#s255"::Core.var"#Type##kw")(::Any, ::Type{DynamicalDDEProblem}, f::DynamicalDDEFunction, v0, u0, h, tspan, p) in SciMLBase at C:\Users\sebastian\.julia\dev\SciMLBase\src\problems\dde_problems.jl:71, (::Core.var"#Type##kw")(::Any, ::Type{DynamicalDDEProblem}, f1::Function, f2::Function, args...) in SciMLBase at C:\Users\sebastian\.julia\dev\SciMLBase\src\problems\dde_problems.jl:80)
 ((var"#s255"::Core.var"#Type##kw")(::Any, ::Type{DynamicalDDEProblem}, f::DynamicalDDEFunction, h, tspan) in SciMLBase at C:\Users\sebastian\.julia\dev\SciMLBase\src\problems\dde_problems.jl:77, (::Core.var"#Type##kw")(::Any, ::Type{DynamicalDDEProblem}, f1::Function, f2::Function, args...) in SciMLBase at C:\Users\sebastian\.julia\dev\SciMLBase\src\problems\dde_problems.jl:80)

The above ambiguities refer only to two function definitions:
https://github.com/SciML/SciMLBase.jl/blob/v1.9.0/src/problems/dde_problems.jl#L77-L82

As a MWE:

using SciMLBase

f1(u,t,h) = u
f2(v,h) = v
f = DynamicalDDEFunction(f1, f2)
h(p,t) = (1,1)

DynamicalDDEProblem(f, h, (0,1))

which gives

ERROR: MethodError: DynamicalDDEProblem(::DynamicalDDEFunction{false, DDEFunction{false, typeof(f1), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, DDEFunction{false, typeof(f2), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, ::typeof(h), ::Tuple{Int64, Int64}) is ambiguous. Candidates:
  DynamicalDDEProblem(f1::Function, f2::Function, args...; kwargs...) in SciMLBase at C:\Users\sebastian\.julia\dev\SciMLBase\src\problems\dde_problems.jl:80
  DynamicalDDEProblem(f::DynamicalDDEFunction, h, tspan) in SciMLBase at C:\Users\sebastian\.julia\dev\SciMLBase\src\problems\dde_problems.jl:77
Possible fix, define
  DynamicalDDEProblem(::DynamicalDDEFunction, ::Function, ::Any)
Stacktrace:
 [1] top-level scope

The problem appears due to the fact that DynamicalDDEFunction <: Function and the commit c555ead removed the restriction on the h argument and thus in both

function DynamicalDDEProblem(f::DynamicalDDEFunction,h,tspan,p=NullParameters();kwargs...)

and

function DynamicalDDEProblem(f1::Function,f2::Function,args...;kwargs...)

the first argument fits the method, but for the second argument we have Any in the first case (which was more specific) and Function in the second (which is more specific than Any).

One option would be to revert the suggestion by @devmotion in c555ead
The other would be to replace

function DynamicalDDEProblem(f1::Function,f2::Function,args...;kwargs...)

with two separate methods, but this would result in code duplication as mentioned in #14 (comment)

I can open a PR to fix this if you would like, just let me know what approach do you think is best.

[ChrisRackauckas]

I think that could work.

[devmotion]

In general, the history function h does not have to be a subtype of Function, so adding a type constraint on h seems wrong.

Would it be possible to remove the type constraints on f1 and f2 in

SciMLBase.jl/src/problems/dde_problems.jl

Line 80 in d67b76e

function DynamicalDDEProblem(f1::Function,f2::Function,args...;kwargs...)

and

SciMLBase.jl/src/problems/dde_problems.jl

Line 100 in d67b76e

function DynamicalDDEProblem{iip}(f1::Function,f2::Function,args...;kwargs...) where iip

? Would that work? IMO it seems also unnecessarily restrictive to impose these constraints on f1 and f2.

[SebastianM-C]

Closed by #43