add varargs nondiff rules

[niklasschmitz]

Addresses #253, following @oxinabox.

I left out the last three rand definitions in light of #263 (?)

@non_differentiable rand(::Any...)
@non_differentiable randn(::Any...)
@non_differentiable randexp(::Any...)

[codecov-io]

Codecov Report

Merging #339 (b74e3f7) into master (e11af5d) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #339   +/-   ##
=======================================
  Coverage   97.64%   97.64%           
=======================================
  Files          18       18           
  Lines        1018     1018           
=======================================
  Hits          994      994           
  Misses         24       24           

Impacted Files	Coverage Δ
src/rulesets/Random/random.jl	100.00% <ø> (ø)

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[mzgubic]

Hey, thanks for taking this on, we appreciate it! The changes look great, thanks for going through the all rules.

With regard to #263: The issue was that the rand function arguments were not constrained at all (i.e. were Any), meaning that the @non_differentiable macro would apply to all the methods, even those that were differentiable in some arguments. It is still possible to reduce the number of lines by replacing, for example:

@non_differentiable rand(::AbstractRNG, ::Integer)
@non_differentiable rand(::AbstractRNG, ::Integer, ::Integer)
@non_differentiable rand(::AbstractRNG, ::Integer, ::Integer, ::Integer)
@non_differentiable rand(::AbstractRNG, ::Integer, ::Integer, ::Integer, ::Integer)
@non_differentiable rand(::AbstractRNG, ::Integer, ::Integer, ::Integer, ::Integer, ::Integer)

with

@non_differentiable rand(::AbstractRNG, ::Integer...)

If you can bump the version number as well this PR is ready to merge.

[niklasschmitz]

I'm unsure about what this comment means, so I didn't replace it by rand!(::Any...)

[mzgubic]

The comment means that the function rand! has many different method definitions, which you can see by typing methods(rand!) in the REPL. However, if you look closely, none of them have a Vararg (or ...) in the arguments. So, it is correct not to replace it, as it would lead to incorrect results in case someone defined a differentiable rand! method with four arguments.

[niklasschmitz]

Now I see, thank you!

[mzgubic]

Great, thanks! Just a couple of minor things left

[mzgubic]

The comment means that the function rand! has many different method definitions, which you can see by typing methods(rand!) in the REPL. However, if you look closely, none of them have a Vararg (or ...) in the arguments. So, it is correct not to replace it, as it would lead to incorrect results in case someone defined a differentiable rand! method with four arguments.

[mzgubic]

Was this line removed by accident, or am I missing something?

[niklasschmitz]

I think it is covered already by randn(::Any...) above

[mzgubic]

Great, this was actually missing a randexp() before, which is now covered.

[niklasschmitz]

Thanks @mzgubic !