tests/cases/compiler/optionalFunctionArgAssignability.ts(7,1): error TS2322: Type '<U>(onFulFill?: (value: number) => U, onReject?: (reason: any) => U) => Promise<U>' is not assignable to type '<U>(onFulfill?: (value: string) => U, onReject?: (reason: any) => U) => Promise<U>'.
!!! error TS2322: Type '<U>(onFulFill?: (value: number) => U, onReject?: (reason: any) => U) => Promise<U>' is not assignable to type '<U>(onFulfill?: (value: string) => U, onReject?: (reason: any) => U) => Promise<U>'.
!!! error TS2322: Types of parameters 'onFulFill' and 'onFulfill' are incompatible.
!!! error TS2322: Type '(value: number) => any' is not assignable to type '(value: string) => any'.
!!! error TS2322: Types of parameters 'value' and 'value' are incompatible.
!!! error TS2322: Type 'number' is not assignable to type 'string'.