Basic Local Variables

After this morning's work, Tangent now supports the most basic of local variables. Yes, the language had user defined syntax, delegates, generics, type-class style interfaces, and... no variable support. But now as I move my focus more from building cool stuff to using cool stuff to build other cool stuff, I need to fill in the gaps. That means fixing the inevitable bugs I find, and basic usability stuff like local variables, which are still going to cause trouble since there wasn't any mutable state at all in the language before today.

I wanted local variables to be able to be phrases, just like parameters and types and everything else in the language. Yet I needed them to be clear both to the compiler and the user that they were declarations and not statements, and I didn't have a lot of tokens to work with, since I want most of them to be available for users to build their own phrases with. Let's look at the test code:

entrypoint => void {
  :x:int := 42;
  print x;
  x = x + 1;
  print x;
}

So local variable declarations start with a colon, and then work like (I hope) you'd expect them to - you declare a phrase and its type. Right now, locals require initialization, which uses pascal-style assignment to differentiate it from `=`, which helps the parser (and user) avoid ambiguity. This code works as of today.

What does not work is capturing locals in lambdas. That will just throw you an exception right off. Nested scopes probably don't work. Variable hiding probably works, but is untested. And due to implementation details, this code probably compiles, but will do unknown and terrible things:

entrypoint => void {
  print x;
  :x:int := 42;
}

Because while the code is smart enough to initialize the locals at the right time, it isn't smart enough to only make them available to the scope when declared, mostly because the scope is immutable and I didn't want to rabbit hole it. 

I have not yet decided if I hate this enough to fix it.

In other usability news, I added support to the command line compiler and test suite to support multiple input files. This should let me reuse code for different programs. I expect that I'm not going to want to reimplement conditionals and loops for every program I write...