detect_unbound_args false positive

[nsajko]

julia> module M
           function f(::Vector{Union{Missing, T}}) where {T <: Real} end
       end
Main.M
 
julia> using Test
 
julia> detect_unbound_args(M)  # when is `T` unbound?
[1] f(::Array{Union{Missing, T}, 1}) where T<:Real @ Main.M REPL[1]:2
 
julia> versioninfo()
Julia Version 1.13.0-DEV.595
Commit 229a6984ee1 (2025-05-14 16:53 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 8 × AMD Ryzen 3 5300U with Radeon Graphics
  WORD_SIZE: 64
  LLVM: libLLVM-20.1.2 (ORCJIT, znver2)
  GC: Built with stock GC
Threads: 1 default, 1 interactive, 1 GC (on 8 virtual cores)
Environment:
  JULIA_NUM_PRECOMPILE_TASKS = 4
  JULIA_PKG_PRECOMPILE_AUTO = 0

vtjnash confirms this is a bug, and says:

currently there are some bugs in both directions with this function, both not detecting important cases and reporting some cases that are unnecessary

[nickrobinson251]

Especially now that Aqua.jl is somwhat widely used, and relies heavily on this function, i think it'd be useful to fix this

@vtjnash you mentioned in #59023 that various issues with this algorithm are know -- are there any proposed solutions already?