Argument of type 'string[]' is not assignable to parameter of type '"value" | "value"[]'.

[ahagelstein]

TypeScript Version: 2.7.0-dev.20171116
Code

const func1 = <T extends (string | number)>(key: string, data: T | T[]): void => {};
const func2 = <T extends (string | number | boolean)>(key: string, data: T | T[]): void => {};

func1("data", ["value"]);
// OK

func2("data", [123, 345]);
// OK

func2("data", [false, true]);
// OK

func2("data", ["123", true]);
// OK

func2("data", ["123"]);
// Argument of type 'string[]' is not assignable to parameter of type '"value" | "value"[]'.
//   Type 'string[]' is not assignable to type '"value"[]'.
//     Type 'string' is not assignable to type '"value"'.

Expected behavior:

Code compiles without errors.

Actual behavior:

Code compiles with error.

BUT: with typescript@2.6.1 there is no error.

Duplicate of #19837

[typescript-bot]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.