feat: improve type specificity by converting to generic

Author: kgryte

lib/node_modules/@stdlib/array/base/filled-by/docs/types/index.d.ts

@@ -23,23 +23,23 @@
 *
 * @returns fill value
 */
-type Nullary = () => any;
+type Nullary<T, U> = ( this: U ) => T;
 
 /**
 * Unary callback function.
 *
 * @param i - current array index
 * @returns fill value
 */
-type Unary = ( i: number ) => any;
+type Unary<T, U> = ( this: U, i: number ) => T;
 
 /**
 * Callback function.
 *
 * @param i - current array index
 * @returns fill value
 */
-type Callback = Nullary | Unary;
+type Callback<T, U> = Nullary<T, U> | Unary<T, U>;
 
 /**
 * Returns a filled "generic" array according to a provided callback function.
@@ -55,7 +55,7 @@ type Callback = Nullary | Unary;
 * var arr = filledBy( 5, constantFunction( 1.0 ) );
 * // returns [ 1.0, 1.0, 1.0, 1.0, 1.0 ]
 */
-declare function filledBy( len: number, clbk: Callback, thisArg?: any ): Array<any>; // tslint:disable-line:max-line-length
+declare function filledBy<T = unknown, U = unknown>( len: number, clbk: Callback<T, U>, thisArg?: ThisParameterType<Callback<T, U>> ): Array<T>;
 
 
 // EXPORTS //

lib/node_modules/@stdlib/array/base/filled-by/docs/types/test.ts

@@ -33,8 +33,8 @@ function clbk( i: number ): number {
 
 // The function returns an array...
 {
-	filledBy( 3, clbk ); // $ExpectType any[]
-	filledBy( 3, clbk, {} ); // $ExpectType any[]
+	filledBy( 3, clbk ); // $ExpectType number[]
+	filledBy( 3, clbk, {} ); // $ExpectType number[]
 }
 
 // The compiler throws an error if the function is provided a first argument which is not a number...