SciMLOperators 0.3.13 ScalarOperator UniformScaling mulitplication stackoverflow

[LynBar]

Describe the bug 🐞
When multiplying a LinearAlgebra.UniformScaling operator with a ScalarOperator I get a stack overflow.

Expected behavior

Minimal Reproducible Example 👇

using SciMLOperators, LinearAlgebra
α = ScalarOperator(1.0)
x = I*(1.0)            
x*α

Error & Stacktrace ⚠️

ERROR: LoadError: StackOverflowError:
Stacktrace:
 [1] *(α::SciMLOperators.ScalarOperator{…}, x::LinearAlgebra.UniformScaling{…}) (repeats 79984 times)
   @ SciMLOperators C:\Users\barry.lynch\.julia\packages\SciMLOperators\2UPBq\src\scalar.jl:322

Environment (please complete the following information):

• Output of using Pkg; Pkg.status()

  [c0aeaf25] SciMLOperators v0.3.13
  [37e2e46d] LinearAlgebra v1.11.0

• Output of using Pkg; Pkg.status(; mode = PKGMODE_MANIFEST)

  [7d9f7c33] Accessors v0.1.42
  [79e6a3ab] Adapt v4.3.0
  [4fba245c] ArrayInterface v7.18.0
  [a33af91c] CompositionsBase v0.1.2
  [187b0558] ConstructionBase v1.5.8
  [ffbed154] DocStringExtensions v0.9.4
  [3587e190] InverseFunctions v0.1.17
  [1914dd2f] MacroTools v0.5.16
  [ae029012] Requires v1.3.1
  [c0aeaf25] SciMLOperators v0.3.13
  [56f22d72] Artifacts v1.11.0
  [ade2ca70] Dates v1.11.0
  [8f399da3] Libdl v1.11.0
  [37e2e46d] LinearAlgebra v1.11.0
  [de0858da] Printf v1.11.0
  [9a3f8284] Random v1.11.0
  [ea8e919c] SHA v0.7.0
  [cf7118a7] UUIDs v1.11.0
  [4ec0a83e] Unicode v1.11.0
  [e66e0078] CompilerSupportLibraries_jll v1.1.1+0
  [4536629a] OpenBLAS_jll v0.3.27+1
  [8e850b90] libblastrampoline_jll v5.11.0+0

• Output of versioninfo()

Julia Version 1.11.5
Commit 760b2e5b73 (2025-04-14 06:53 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Windows (x86_64-w64-mingw32)
  CPU: 14 × Intel(R) Core(TM) Ultra 5 125U
  WORD_SIZE: 64
  LLVM: libLLVM-16.0.6 (ORCJIT, alderlake)
Threads: 1 default, 0 interactive, 1 GC (on 14 virtual cores)

Additional context

The offending code is in the multiplication function in scalar.jl line 319;

T2 = promote_type($T, eltype(α))
return ScalarOperator(convert(T2, α) * x, α.update_func)

Here T2=Any with typeof(x) = UniformScaling, so that when convert(T2,α) is called, α remains a ScalarOperator resulting in a stackoverflow.

I'm not sure if I'm meant to able to multiply by UniformScaling, but it is in the SCALINGNUMBERTYPES array so I assume it should be.

[ChrisRackauckas]

I'm not sure if I'm meant to able to multiply by UniformScaling, but it is in the SCALINGNUMBERTYPES array so I assume it should be.

We probably need to add a bunch of methods so that multiplying by UniformScaling is a no-op and just returns the operator. That can probably be done with *(::UniformScaling, A::AbstractSciMLOperator) = A. But then it needs to check that the scaling factor is one if it does that, or else it needs to then make this into *(::UniformScaling, A::AbstractSciMLOperator) = ScalarOperator(I.lambda) * A which with #264 should now be a good way to handle your case and more generally it should handle all of the cases here.