function argument lowering inconsistency

[simeonschaub]

I don't think, this is actually a real problem, but it's a bit inconsistent that the following throws a syntax error:

julia> f(a, a[1]) = a
ERROR: syntax: "a[1]" is not a valid function argument name around REPL[16]:1
Stacktrace:
 [1] top-level scope
   @ REPL[16]:1

, whereas we allow this:

julia> f(a, (a[1],)) = a
f (generic function with 1 method)

julia> a = [1]
1-element Vector{Int64}:
 1

julia> f(a, 2)
1-element Vector{Int64}:
 2

julia> a
1-element Vector{Int64}:
 2

We could add a check for this when lowering destructed assignments, but it may not be worth it to bother.