Add static variable resolution with scope tracking

- Add distance-based get_at on EnvironmentStack
- Add distance-based assign_at on EnvironmentStack
- Introduce ErrorSink to accumulate diagnostics across passes
- Implement Resolver with a ScopeStack and per-node distance map
- Extend interpreter to store locals distances for runtime lookup
- Add tests for resolution behavior and error accumulation
  Add static variable resolution with scope tracking

src/main.rs

@@ -15,6 +15,7 @@ use crate::{
         parser::Parser,
         source_registry::{SourceId, SourceRegistry},
     },
+    middleend::variable_resolution::Resolver,
 };
 use std::env;
 use std::fs;
@@ -185,7 +186,11 @@ impl LoxInterpreter {
 
     // Funzione per eseguire l'AST
     fn execute_ast(&self, ast: Vec<AstNode<Stmt>>, debug: bool) -> LoxResult<String> {
+        // Static resolution pass: compute variable scope distances and report
+        // any resolution errors before executing.
+        let locals = self.resolve(&ast)?;
         let mut interpreter = Interpreter::new();
+        interpreter.set_locals(locals);
         let mut result = None;
 
         for (index, stmt) in ast.iter().enumerate() {
@@ -204,6 +209,19 @@ impl LoxInterpreter {
         }
     }
 
+    // Static variable resolution; prints and returns the first error, if any.
+    fn resolve(
+        &self,
+        ast: &[AstNode<Stmt>],
+    ) -> LoxResult<std::collections::HashMap<crate::common::ast::NodeId, usize>> {
+        Resolver::resolve_program(ast).map_err(|errors| {
+            for err in &errors {
+                err.print_with_context(&self.source_registry);
+            }
+            errors.into_iter().next().unwrap()
+        })
+    }
+
     fn process_source(
         &self,
         source_id: SourceId,
@@ -245,8 +263,10 @@ impl LoxInterpreter {
             return Ok(format_ast(&ast));
         }
 
-        // Stage 3: Interpretation
+        // Stage 3: Resolution + Interpretation
+        let locals = self.resolve(&ast)?;
         let mut interpreter = Interpreter::new();
+        interpreter.set_locals(locals);
         let mut result = None;
 
         for (index, stmt) in ast.iter().enumerate() {