add typescript generic type to functions to ensure type check

[amir-khoshbakht]

Description

as you can see there is a union type which consists of two strings "aaa" and "bbb".
I need to get sure that class property is one of allowed values. This is done in three ways in the following section.
The first method: does not have the necessary efficiency and even though there is no "bad" option in the type, it does not show an error

the second method: In this case, all the options should be available in the type ((unionType)), and this case is desirable

import { IsEnum} from 'class-validator';

type unionType = 'aaa' | 'bbb';

const as = <T>(option: T) => option;

class ForTest{
  // method 1
  @IsEnum(['aaa', 'bad'] as unionType[])
  test: string;

  // method 2
  // typescript dosnt allow "bad" string which is not available in type
  @IsEnum(as<unionType[]>(['aaa', 'bad']))
  test2: string;
}

References

the expected method :

// typescript will show error for "bad" value
@IsEnum<unionType[]>(['aaa', 'bad'])
test3: string;

If the generic type is added to these functions, the correctness of the type can be ensured directly without defining the secondary function.

note: function "as" is custom function above

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[typestack-ci]

@dependabot squash and merge

[typestack-ci]

@dependabot squash and merge

[typestack-ci]

@dependabot squash and merge

[typestack-ci]

@dependabot squash and merge

[typestack-ci]

@dependabot squash and merge