**TypeScript Version:** 3.5.1 **Search Terms:** index signature, property does not exist **Code** ```ts export class Test { [k: string]: any; someMethod() { this.age = 3; } } ``` **Expected behavior:** There should be no error, age assignment is correct according to index signature. It used to work in typescript 3.4.5 **Actual behavior:** Error "Property 'age' does not exist on type 'Test'"