15 lines
1 KiB
Plaintext
15 lines
1 KiB
Plaintext
==== tests/cases/compiler/optionalFunctionArgAssignability.ts (1 errors) ====
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interface Promise<T> {
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then<U>(onFulfill?: (value: T) => U, onReject?: (reason: any) => U): Promise<U>;
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}
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var a = function then<U>(onFulfill?: (value: string) => U, onReject?: (reason: any) => U): Promise<U> { return null };
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var b = function then<U>(onFulFill?: (value: number) => U, onReject?: (reason: any) => U): Promise<U> { return null };
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a = b; // error because number is not assignable to string
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~
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!!! 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>':
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!!! Types of parameters 'onFulFill' and 'onFulfill' are incompatible:
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!!! Type '(value: number) => any' is not assignable to type '(value: string) => any':
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!!! Types of parameters 'value' and 'value' are incompatible:
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!!! Type 'number' is not assignable to type 'string'.
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