Add error reporting to language

[miningape]

This will involve adding an error class or functions or something to make error reporting sexy. This will also mean looking through the tokeniser and adding error reporting where needed.

For example
"a string should produce a nice short error like on line 1: Expected '"' character before newline for example rather than what we have now lmao

[miningape]

Take a look here for inspiration.

I think we should leverage python's raise not being a return value (which is a problem in java/example link)

[spralja]

@miningape

I think we should leverage python's raise not being a return value (which is a problem in java/example link)

Can you clarify what you mean by that, I'm not sure I understand.

[miningape]

If you look at the example I sent. You can see that he uses very roundablout ways to call the error function, and he never just raises errors... That's because of how java requires the exceptions thrown to be included in the return type of a method. In python we don't have that problem so we can make our code neater / better than his

[spralja]

@miningape

Okay I understand now.

So you are saying that we should just raise the errors in the normal python way, and catch them somewhere up the stack.

I'm thinking that implementing our own stack trace wouldn't be trivial, but I assume that every scope would have access to the stack trace so we could append it to the exception?

[miningape]

@spralja Yeah I kinda imagine we throw something like this

else:
    raise ParseError(token, "Unexpected token")

Then we do sth like this

except OurBaseError as e:
   print(str(e))

Then we can also make nice functions that make errors for us

def expect(token):
   if next != token:
      raise ParseError("Expected ", token, " Got", next)