Introduce NodeId for AST and synthetic slices

src/middleend/visit_ast.rs

@@ -73,7 +73,6 @@ pub fn walk_stmt<V: Visitor>(visitor: &mut V, stmt: &AstNode<Stmt>) -> LoxResult
             }
             Ok(())
         }
-        Stmt::VarAssigment { value, .. } => visitor.visit_expr(value),
         Stmt::Return { expression, .. } => visitor.visit_expr(expression),
         Stmt::Block { statements, .. } => {
             for statement in statements.iter() {
@@ -137,6 +136,7 @@ pub fn walk_expr<V: Visitor>(visitor: &mut V, expr: &AstNode<Expr>) -> LoxResult
             visitor.visit_expr(right)
         }
         Expr::Unary { operand, .. } => visitor.visit_expr(operand),
+        Expr::Assign { value, .. } => visitor.visit_expr(value),
         Expr::Grouping { expression } => visitor.visit_expr(expression),
         Expr::Call {
             callee, arguments, ..