fix(controller-utils): use overload signatures where appropriate

packages/controller-utils/src/util.ts

@@ -70,7 +70,7 @@ export function isSafeChainId(chainId: Hex): boolean {
  */
 // TODO: Either fix this lint violation or explain why it's necessary to ignore.
 // eslint-disable-next-line @typescript-eslint/naming-convention
-export function BNToHex(inputBn: BN | BN4 | BigNumber) {
+export function BNToHex(inputBn: BN | BN4 | BigNumber): string {
   return add0x(inputBn.toString(16));
 }
 
@@ -79,6 +79,8 @@ export function BNToHex(inputBn: BN | BN4 | BigNumber) {
  * @param targetBN - A BN instance
  * @returns A bn.js instance
  */
+function getBNImplementation(targetBN: BN4): typeof BN4;
+function getBNImplementation(targetBN: BN): typeof BN;
 function getBNImplementation(targetBN: BN | BN4): typeof BN4 | typeof BN {
   return Object.keys(targetBN).includes('_strip') ? BN4 : BN;
 }
@@ -91,17 +93,27 @@ function getBNImplementation(targetBN: BN | BN4): typeof BN4 | typeof BN {
  * @param denominator - Denominator of the fraction multiplier.
  * @returns Product of the multiplication.
  */
+export function fractionBN(
+  targetBN: BN,
+  numerator: number | string,
+  denominator: number | string,
+): BN;
+export function fractionBN(
+  targetBN: BN4,
+  numerator: number | string,
+  denominator: number | string,
+): BN4;
 export function fractionBN(
   targetBN: BN | BN4,
   numerator: number | string,
   denominator: number | string,
-) {
+): BN | BN4 {
+  // @ts-expect-error - Signature overload confusion
   const BNImplementation = getBNImplementation(targetBN);
 
-  // @ts-expect-error - Incompatible constructor signatures are actually compatible here
   const numBN = new BNImplementation(numerator);
-  // @ts-expect-error - Incompatible constructor signatures are actually compatible here
   const denomBN = new BNImplementation(denominator);
+  // @ts-expect-error - BNImplementation gets unexpected typed
   return targetBN.mul(numBN).div(denomBN);
 }
 
@@ -213,6 +225,8 @@ export function hexToText(hex: string) {
  * @param value - A base-16 number encoded as a string.
  * @returns The number as a BN object in base-16 mode.
  */
+export function fromHex(value: string | BN): BN;
+export function fromHex(value: BN4): BN4;
 export function fromHex(value: string | BN | BN4): BN | BN4 {
   if (BN.isBN(value)) {
     return value;