Add check for binding non-writable variables

src/compiler/compile/nodes/Binding.ts

@@ -72,6 +72,11 @@ export default class Binding extends Node {
 			});
 
 			variable[this.expression.node.type === 'MemberExpression' ? 'mutated' : 'reassigned'] = true;
+
+			if (!variable.writable) component.error(this.expression.node, {
+				code: 'invalid-binding',
+				message: 'Cannot bind to a variable which is not writable',
+			});
 		}
 
 		const type = parent.get_static_attribute_value('type');