Improvements to requirements

[zsunberg]

If the requirements system turns out to be useful, the following improvements could be made

• [ ] Smartly and optionally print module names (easy)
• [ ] Allow parameters throughout (I think they will break some functions now) (medium)
• [ ] Print requirements even if there is an error in get_requirements. Currently, if there is an error in a @POMDP_require block, it will not show any @reqs that come after the error. A better way to fail would be to show the requirement (but possibly without all the type information). It is not clear how to handle cases when a @req is in an if statement or has some other conditionality (difficult)
• [ ] Use static analysis to determine the requirements instead of specifying them manually (difficult)
• [ ] One should also be able to specify requirements with a function call and have the types inferred, e.g

@POMDP_require f(a::A) begin
    @req f(a)
end

should work in addition to

@POMDP_require f(a::A) begin
    @req f(::typeof(a))
end

which already works. (easy)

• [ ] Might be able to unify @req and @subreq - do they need to be different? (meidum)

[etotheipluspi]

This is great, and the new requirements functionality is awesome! Can we merge the improvements checklist into the original post to make it easier to track.

[zsunberg]

Done. BTW, I personally don't ever expect to get around to doing any of these tasks, haha - it will only happen if someone else gets deeply involved with this.

[zsunberg]

Seems like code_typed works pretty well now, so it should be pretty easy to automate more things