MIR: lexical scoping + builder vars modules

src/mir/builder/stmts.rs

@@ -170,6 +170,8 @@ impl super::MirBuilder {
         // Scope hint for bare block (Program)
         let scope_id = self.current_block.map(|bb| bb.as_u32()).unwrap_or(0);
         self.hint_scope_enter(scope_id);
+        let _lex_scope = super::vars::lexical_scope::LexicalScopeGuard::new(self);
+
         let mut last_value = None;
         let total = statements.len();
         eprintln!("[DEBUG/build_block] Processing {} statements", total);
@@ -336,7 +338,7 @@ impl super::MirBuilder {
                     var_name, var_id
                 );
             }
-            self.variable_map.insert(var_name.clone(), var_id);
+            self.declare_local_in_current_scope(var_name, var_id)?;
             // SlotRegistry にもローカル変数スロットを登録しておくよ（観測専用）
             if let Some(reg) = self.current_slot_registry.as_mut() {
                 let ty = self.value_types.get(&var_id).cloned();