feat: Add StaticType and type checking

This commit introduces `StaticType` and enhances the `Binder` to perform
basic type checking during the binding phase.

Key changes include:

- **`StaticType` enum:** Represents static types such as `Any`, `Void`,
  `Bool`, `Int`, `Float`, `Text`, `List`, `Record`, and `Function`.
- **`Node<K, T>`:** The generic `Node` now includes a `ty` field to
  store its inferred static type.
- **Binder enhancements:**
    - `CompilerScope` now stores `LocalInfo` containing the variable's
      slot and `StaticType`.
    - `FunctionCompiler` stores upvalues with their associated
      `StaticType`.
    - `Binder::bind` now returns `Node<BoundKind, StaticType>`,
      propagating type information.
    - Type checking is added for `If` conditions and `Assign`
      operations.
    - `Def` nodes now infer and store the type of the defined variable.
- **`Value::static_type()`:** A new method to determine the `StaticType`
  of a `Value`.
- **Environment modifications:** `global_names` now stores `(u32,
  StaticType)` to associate global variables with their types.
- **Parser modifications:** The `ty` field of nodes is initialized to
  `()` by default.
- **VM modifications:** `VM::run` and `VM::eval` now operate on
  `Node<BoundKind, StaticType>`.
- **Tests:** Added basic evaluation and type error tests.
  feat: Add StaticType and type checking

Introduces `StaticType` enum and integrates it into the AST. The binder
now performs type checking during compilation, ensuring that expressions
conform to expected types, especially for control flow structures like
`if`. This lays the groundwork for static type analysis and error
reporting.

src/ast/vm.rs

@@ -2,11 +2,11 @@ use std::sync::{Arc, Mutex};
 use std::any::Any;
 use crate::ast::compiler::bound_nodes::{Address, BoundKind};
 use crate::ast::nodes::Node;
-use crate::ast::types::{Value, Object};
+use crate::ast::types::{Value, Object, StaticType};
 
 #[derive(Debug, Clone)]
 pub struct Closure {
-    pub function_node: Arc<Node<BoundKind>>,
+    pub function_node: Arc<Node<BoundKind, StaticType>>,
     pub upvalues: Vec<Value>,
 }
 
@@ -40,7 +40,7 @@ impl VM {
         }
     }
 
-    pub fn run(&mut self, root: &Node<BoundKind>) -> Result<Value, String> {
+    pub fn run(&mut self, root: &Node<BoundKind, StaticType>) -> Result<Value, String> {
         self.stack.clear();
         self.frames.clear();
 
@@ -56,7 +56,7 @@ impl VM {
         result
     }
 
-    fn eval(&mut self, node: &Node<BoundKind>) -> Result<Value, String> {
+    fn eval(&mut self, node: &Node<BoundKind, StaticType>) -> Result<Value, String> {
         match &node.kind {
             BoundKind::Nop => Ok(Value::Void),
             BoundKind::Constant(v) => Ok(v.clone()),