v6 Parsing: typed declarations and signatures

What changes in v6

• Type annotations are parsed as AST nodes, not strings.
• Every function parameter requires IDENT : type.
• Function declarations require -> return type.
• Types are recursive (fn(...) -> ..., map<k, v>, array<elem>).

Type parser contract

• primitives: number, bool, string, nil
• array<type>: exactly one element type
• map<key, value>: exactly two type arguments
• function type: fn(typeList?) -> type

AST outputs

• Stmt.TypeAnn for variable declarations
• Stmt.ParamTypes for each function parameter
• Stmt.ReturnType for function return
• Type nodes with Elem, Key, Value, Params, Return

Parser mechanics

• parseFnDecl sequence is strict:
  • fn name ( params ) -> returnType block
• parameter parser returns both names and types in parallel arrays
• parseType is called from both var declarations and function params

Practice focus

1) parse missing return type errors 2) nested type nesting (fn inside map/array) 3) map type arity and delimiter validation 4) unknown named type rejection 5) keep v5 declaration behavior for assignments and for-inits