- renamed assembler_runner to just assembler

- implemented type parsing including custom types and generics (useless
  for now as we do no semantic analysis)
- implemented struct literal parsing
- implemented struct definition parsing (no generics yet)
- implemented tuple parsing
- registers are now allocated starting from zero
- updated to-dos

docs/todo.md

@@ -1,10 +1,26 @@
+# General TODO's
 
-# Compiler optimisations!
+# Bugfixes
+- [x] [EASY] Investigate logical and operator not compiling - either a lexer or parser issue.
+  - **note**: this was a parser issue.
 
+# Missing features
+- [x] [MEDIUM] Get shift operations working correctly.
+- [ ] [MEDIUM] proper prefix/postfix inc/dec implementation. slightly more complex as we need to check for a variable and modify it in place
+- [ ] [EASY] Add multiply and divide operations to code generation
+  - **note**: very easy to do but our division algorithm is hopelessly slow so not worth doing for now.
+
+# Performance Improvements
+- [ ] [MEDIUM] implement a proper div/mod library that's not slow af.
 - [ ] [HARD] Immediate operations for values that support it (up to +/- u16::max for addi and subi respectively) 
   - this requires significant complexity in code generation as we need to traverse down the tree when we come across these operations to prevent additional register allocations.
 
-- [ ] [EASY] Add multiply and divide operations to code generation
-- [ ] [MEDIUM] proper prefix/postfix inc/dec implementation. slightly more complex as we need to check for a variable and modify it in place
-- [ ] [EASY] Investigate logical and operator not compiling - either a lexer or parser issue.
-- [x] [MEDIUM] Get shift operations working correctly.
+# Compiler optimisations
+
+# Codegen improvements
+- [ ] [MEDIUM / time consuming] Add scoping to code generation
+- [ ] [MEDIUM / time consuming] Rewrite entire codegen to imrpove code quality and make the code more readable.
+  - [ ] type-safe instruction builder
+    - [ ] Instruction & Register enums
+    - [ ] Instruction builder helper fns eg `fn add(left: &Register, right: &Register, dest: &Register) -> Instruction`
+    - [ ] Instruction Block types.