Add Env/GenericParams overloads to various methods. (#1408)
* Add Env/GenericParams overloads to various methods.
These are needed for genericsTake2. They simply forward to the old methods with null for now, which continue to exist (but deprecated), but the callers should all be updated, and so now have more time to upgrade before the genericsTake2 branch is merged in with the breaking changes. (commit: 07433a0)
Convert to an iterative eval loop instead of a recursive one (#1409)
* Convert to an iterative eval loop instead of a recursive one.
This is a major change in the script evaluation process, which changes how "special execution" functions work. Previously, functions could choose to implement execs instead of exec, which received a ParseTree, instead of Mixed. This allowed the individual function to decide how or even if the ParseTree nodes were further executed. This works in general, however it has several drawbacks.
In particular, the core evaluation loop loses control over the script once it decends into individual functions. Therefore features like Ctrl+C in command line scripts relied on each of these "flow" functions to implement that feature correctly, and only some of them did. This also prevents new features from being implemented as easily, like a debugger, since the evaluation loop would need to be modified, and every single flow function would need to make the same changes as well.
This also has several performance benefits. Using a recursive approach meant that each frame of MethodScript had about 3 Java frames, which is inefficient. The biggest performance change with this is moving away from exception based control flow. Previously, return, break, and continue were all implemented with Java exceptions. This is more expensive than it needs to be, especially for very unexceptional cases such as return(). Now, when a proc or closure returns, it triggers a different phase in the state machine, instead of throwing an exception.
This also unlocks future features that were not possible today. A debugger could have been implemented before (though it would have been difficult) but now an asynchronous debugger can be implemented. async/await is also possible now. Tail call optimizations can be done, execution time quotas, and the profiler can probably be improved.
* Use our own stack counter to determine when a StackOverflow happens.
* Add CallbackYield class for functions that execute callbacks.
Previously, callback invocations required re-entering the eval loop from the top, which defeats the iterative loop. In principal, the functions that call Callables need to become flow functions to behave correctly, but for basic yield-style invocations, this infrastructure is too heavy, so CallbackYield is a new class which puts the function in terms of an exec-like mechanism, only introducing the Yield object, which is just a queue of operations, effectively.
More functions need to convert to this, but as a first start, array_map has been converted. Some of the simpler FlowFunctions might be able to be simplified to this as well.
* Convert various function to CallbackYield functions.
These are the "easy" functions to convert.
* Finish converting CallbackYield and FlowFunctions (commit: b846e13)
