[SPEED-3094] Support not having a Return or a Throw if an underlying function throws and is not caught

[Fladolcetta]

Problem:

The following code is legitimate; but guardrail doesn't think it is

function throwFunction () {
  throw Exception;
}

function anotherFunction(bool myBool): int {
  if (myBool) {
    return 1; 
  }
  throwFunction()
}

Solution:

Check if underlying functions throw.

• Added new tests
• Added a throwOnly option to several functions that previously checked for return or throw
• Add new functions to handle when a function calls a function / method / staticmethod

[jongardiner]

I'm sorry, but I don't think I can approve this. It won't cover a lot of real world scenerios where the body is in another file as is, and if we parse external files, we'll take a pretty significant performance hit.

We could maybe do something around methods that are documented to return "never" which is a new return type. (Although I'm not sure throwing counts as returning.)

[jongardiner]

I see what we're doing. We're trying to grab the body of the function that is being called in order to look up whether is contains a throw statement. That's going to work if the function is in the same file, but if it is a function in a different file then it won't be able to get the method body the way that we do here. There is a way to grab the file contents and parse it, but it is a pretty big performance hit. I have a branch where I do some work around declared throws where we don't have to have the method body handy to know if a function might throw. We don't have anything for a method that ALWAYS throws, which I think is what we're looking for here.