Support keyword args in anonymous functions with optional positional args

[AndiMD]

The following behavior seems erroneous, or at least confusing to me:

These work:
f(x=1;y=2)=x+y
(x;y=2)->x+y
(x=1,y=2)->x+y

This errors:
(x=1;y=2)->x+y

ERROR: syntax: invalid assignment location "begin
x=1
y=2
end"

versioninfo()
Julia Version 0.6.2
Commit d386e40 (2017-12-13 18:08 UTC)
Platform Info:
OS: Linux (x86_64-pc-linux-gnu)
CPU: Intel(R) Core(TM) i7-6820HQ CPU @ 2.70GHz
WORD_SIZE: 64
BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY Haswell)
LAPACK: libopenblas64_
LIBM: libopenlibm
LLVM: libLLVM-3.9.1 (ORCJIT, skylake)

[mbauman]

For reference, anonymous functions created with the function keyword were fixed in #19744. Looks like we still need to fix this case.

[AndiMD]

@mbaumann: Unfortunately, there still seems to be an issue when the first parameter has a default value:

f = function(x=1; kwargs...) return x; end
f = function(x=1; y=2) return x+y; end

[mbauman]

Ah, I see now. Thanks for the correction.