Using Plots.jl before LinearAlgebra affects `hasmethod` for `norm`

[frankwswang]

julia> using LinearAlgebra # v1.11.5

julia> hasmethod(LinearAlgebra.norm, NTuple{1, T} where {T<:Union{}})
true

Restart Julia REPL:

julia> using Plots # v1.40.10
                                                                 
julia> using LinearAlgebra # v1.11.5                                 

julia> hasmethod(LinearAlgebra.norm, NTuple{1, T} where {T<:Union{}})
false  

System info:

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: 18 × 12th Gen Intel(R) Core(TM) i9-12900HK
  WORD_SIZE: 64
  LLVM: libLLVM-16.0.6 (ORCJIT, alderlake)
Threads: 1 default, 0 interactive, 1 GC (on 18 virtual cores)

[vtjnash]

We could probably also make this throw ERROR: Tuple field type cannot be Union{} since there isn't really a way to implement this to return correct answers for hasmethod

[frankwswang]

I'm curious why importing another library will change the result of hasmethod. Was there some global pseudo-random number generator altered during that process?

[nsajko]

using Plots loads some norm methods defined by dependencies of the Plots package. I guess that's the reason.