[UX]: "Given expression is not a function call or definition" for short-form function definition

[jariji]

What happened?

julia> Supposition.@check checkassociativeinstance(a,b,c) = (a + b) + c == a + (b + c)
ERROR: LoadError: ArgumentError: Given expression is not a function call or definition!
in expression starting at REPL[2]:1

How could this be communicated better?

It says it's not a function definition but it is one, so it shouldn't say that it isn't.

Julia Version

julia> versioninfo()
Julia Version 1.10.0
Commit 3120989f39b (2023-12-25 18:01 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 24 × AMD Ryzen 9 3900XT 12-Core Processor
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, znver2)
  Threads: 17 on 24 virtual cores
Environment:
  JULIA_NUM_THREADS = 12

Package Environment

(@main) pkg> st Supposition
Status `~/.julia/environments/main/Project.toml`
  [5a0628fe] Supposition v0.3.1