gradient(f,args...) not update when rewriting function

[johnnychen94]

julia> using Zygote
[ Info: Precompiling Zygote [e88e6eb3-aa80-5325-afca-941959d7151f]

julia> f(x) = 2x + 3
f (generic function with 1 method)

julia> Zygote.gradient(f,0)
(2,)

julia> f(x) = 0
f (generic function with 1 method)

julia> Zygote.gradient(f,0) # should be 0
(2,)

[chriselrod]

Duplicate of #22

Use Zygote.refresh().

[johnnychen94]

Thanks.