Add support for syntax blocks.

src/syntax/validate.rs

@@ -177,6 +177,13 @@ impl Statement {
             Statement::Print(loc, var) => {
                 errors.push(Error::UnboundVariable(loc.clone(), var.to_string()))
             }
+
+            Statement::Expression(e) => {
+                let (mut exp_errors, mut exp_warnings) = e.validate(bound_variables);
+
+                errors.append(&mut exp_errors);
+                warnings.append(&mut exp_warnings);
+            }
         }
 
         (errors, warnings)