Weird parsing of quoted macro names?

[phipsgabler]

I stumbled upon this in 0.6.0 -- so maybe this has been changed in the mean time. Or maybe it's not weird at all, but it surprised me...

Basically, the following error came unexpectedly (I used it in actual syntax, the outer quoting is just for demonstration):

julia> :(simd ? :@simd : :@identity)
ERROR: syntax: space not allowed after ":" used for quoting

This can be fixed by using

julia> :(simd ? :(@simd) : :@identity)
:(if simd
        $(Expr(:quote, :(@simd)))
    else 
        $(Expr(:quote, :(@identity)))
    end)

I compared some other things, and the first one of these is definitely weird, too, but explains the above error:

julia> :(:@simd + 2)
:($(Expr(:quote, :(@simd +2))))

julia> :(:simd + 2)
:(:simd + 2)

julia> :(:(@simd) + 2)
:($(Expr(:quote, :(@simd))) + 2)

It seems that the @ makes the parsing of the following elements greedier?

---

Julia Version 0.6.0
Commit 9036443 (2017-06-19 13:05 UTC)
Platform Info:
OS: Linux (x86_64-pc-linux-gnu)
CPU: Intel(R) Core(TM) i5-6200U CPU @ 2.30GHz
WORD_SIZE: 64
BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY Haswell)
LAPACK: libopenblas64_
LIBM: libopenlibm
LLVM: libLLVM-3.9.1 (ORCJIT, skylake)

[bramtayl]

Your first statement is parsing as

(simd ? :(@simd : :@identity))

Which is why you need to specify the parens around :(@simd)