Does not work with Symbol arguments

[essenciary]

julia> @pattern foo(:a) = println("aaaa")
ERROR: recode: unimplemented: ex = :a

julia> versioninfo()
Julia Version 0.4.6
Commit 2e358ce* (2016-06-19 17:16 UTC)
Platform Info:
  System: Darwin (x86_64-apple-darwin15.5.0)
  CPU: Intel(R) Core(TM) i7-3740QM CPU @ 2.70GHz
  WORD_SIZE: 64
  BLAS: libopenblas (DYNAMIC_ARCH NO_AFFINITY Sandybridge)
  LAPACK: libopenblas
  LIBM: libopenlibm
  LLVM: libLLVM-3.3