Better error needed for misuse of keyword args

[jdlangs]

I had a mental lapse and forgot to use the keyword argument name when invoking a function. I ended being baffled for a good five minutes before realizing what happened.

julia> f(;x=1) = x+1
f (generic function with 1 method)

julia> f(;x=3)
4

julia> f(;3)
ERROR: BoundsError
 in anonymous at no file

This seems like something the parser should be able to pick up instantly.

[ivarne]

+1 for making this a parser error.

Note that the ; is optional for calling a function with keyword arguments.

[JeffBezanson]

Note the following is valid:

julia> f(;x=1) = x+1
f (generic function with 1 method)

julia> p = :x=>1
:x=>1

julia> f(;p)
2

[jdlangs]

That does complicate it. Then maybe a couple runtime asserts can be added to check that whatever is passed is iterable with at least 2 elements, and the first is a symbol?

I realize it's probably a rarely seen case but the current error really does confuse way more than help to debug.

[jaboatman]

I just ran into this when generating function calls with named arguments from a macro.

A minimal example:

julia> f(;x=1) = x+1
f (generic function with 1 method)

julia> macro m(named...)
           esc(:(f(;$(named...))))
       end

julia> @m x=1
ERROR: BoundsError
 in anonymous at no file

julia> @m :x=>1
2

julia> macroexpand(:(@m x=1))
:(f(; x = 1))

What makes the BoundsError particularly confusing is the apparently correct output from macroexpand.

[rofinn]

+1. I guess a parsing error makes the most sense. Mostly, I'd just like the error to remind me what the signature is vs what it received, cause I'm dumb and have been confused by this a couple times.