Change the parser to build and AST and then run the program

[thygesteffensen]

Configure the Parser to build an AST instead of during it all in once.

This gives the ability to:

• Change tokens (nodes) with new nodes
• Better error handling. I.e. record errors and report later
• Lookup function is defined, maybe have som pre-validation if input is correct, and if the return type is known (it typically is - add as meta data?)
• Build a light version which can be used real time to type check?

[thygesteffensen]

Constructing AST nodes gives os the ability to record which token generated the node, e.g. having alias can be recorded (and the position) and having the handler (i.e. the function implementation) class given to the AST node for later constructing and invocation

[thygesteffensen]

Functions implements abstract class and only provide protected function, to the abstract class can do something before execution, which the implementer shouldn't worry about

[thygesteffensen]

Typecheck with return type
Return from error -> Skip to next ) and try to keep parsing, to find alle errors

[thygesteffensen]

Consider going to a parser generator instead and use time on error recovery

[thygesteffensen]

Depends on the grammar, sometimes the handwritten parser is the way forward, if the grammar is too weird.