tests/cases/compiler/noErrorsInCallback.ts(4,19): error TS2345: Argument of type '{}' is not assignable to parameter of type 'string'. tests/cases/compiler/noErrorsInCallback.ts(6,23): error TS2345: Argument of type '{}' is not assignable to parameter of type 'string'. ==== tests/cases/compiler/noErrorsInCallback.ts (2 errors) ==== class Bar { constructor(public foo: string) { } } var one = new Bar({}); // Error ~~ !!! error TS2345: Argument of type '{}' is not assignable to parameter of type 'string'. [].forEach(() => { var two = new Bar({}); // No error? ~~ !!! error TS2345: Argument of type '{}' is not assignable to parameter of type 'string'. });