propEq type definition does not guarantees type safety

[peterreisz]

The current definition accepts any as the last parameter

export function propEq<T>(propToFind: string | number, valueToMatch: T, obj: any): boolean;
export function propEq<T>(propToFind: string | number, valueToMatch: T): (obj: any) => boolean;
export function propEq(propToFind: string | number): {
  <T>(valueToMatch: T, obj: any): boolean;
  <T>(valueToMatch: T): (obj: any) => boolean;
};

The type safe solution would be something like this:

export function propEq<T, K extends keyof T>(propToFind: K, valueToMatch: T[K], obj: T): boolean;
export function propEq<T, K extends keyof T>(propToFind: K, valueToMatch: T[K]): (obj: T) => boolean;
export function propEq<T, K extends keyof T>(propToFind: K): {
   (valueToMatch: T[K], obj: T): boolean;
   (valueToMatch: T[K]): (obj: T) => boolean;
};

[selfrefactor]

Thank you @peterreisz for pointing this out.

I copied the definitions from @types/ramda and I created a dtslint test to confirm the change. You can see it in the referenced commit.

[selfrefactor]

Released with 5.6.1

[peterreisz]

@selfrefactor there is a problem with the Record solution when using optional properties.
When the type has optional property you cannot write code which compiles.
The built-in Record type constructs a new type, but in that type the prop will be required, which will not match with the given type.

interface MyType {
    optional?: string | number;
}

function propEqWithRecord<K extends string | number, V>
  (propToFind: K, valueToMatch: V, obj: Record<K, V>): boolean {
    return false;
}

function propEqWithoutRecord<K extends keyof T, T>
  (propToFind: K, valueToMatch: T[K], obj: T): boolean {
    return false;
}

const myObject: MyType = {};
const valueToFind = '1111';
const optionalValueToFind: string | number | undefined = '1111';

// These will not compile
propEqWithRecord('optional', valueToFind, myObject);
propEqWithRecord('optional', optionalValueToFind, myObject);

// These will compile
propEqWithoutRecord('optional', valueToFind, myObject);
propEqWithoutRecord('optional', optionalValueToFind, myObject);

[selfrefactor]

@peterreisz I will run dtslint test and most probably I will apply your suggestion.

[selfrefactor]

Released with 5.6.2