refac(errors): Unify code structure and improve types (#5278)

* refac(errors): Unify code structure and improve types

* refac: fixed type

Author: ssi02014

packages/zod/src/v4/core/errors.ts

@@ -226,9 +226,9 @@ type _FlattenedError<T, U = string> = {
 
 export function flattenError<T>(error: $ZodError<T>): _FlattenedError<T>;
 export function flattenError<T, U>(error: $ZodError<T>, mapper?: (issue: $ZodIssue) => U): _FlattenedError<T, U>;
-export function flattenError(error: $ZodError, mapper = (issue: $ZodIssue) => issue.message): any {
-  const fieldErrors: any = {};
-  const formErrors: any[] = [];
+export function flattenError<T, U>(error: $ZodError<T>, mapper = (issue: $ZodIssue) => issue.message as U) {
+  const fieldErrors: Record<PropertyKey, any> = {};
+  const formErrors: U[] = [];
   for (const sub of error.issues) {
     if (sub.path.length > 0) {
       fieldErrors[sub.path[0]!] = fieldErrors[sub.path[0]!] || [];
@@ -254,12 +254,7 @@ export type $ZodFormattedError<T, U = string> = {
 
 export function formatError<T>(error: $ZodError<T>): $ZodFormattedError<T>;
 export function formatError<T, U>(error: $ZodError<T>, mapper?: (issue: $ZodIssue) => U): $ZodFormattedError<T, U>;
-export function formatError<T>(error: $ZodError, _mapper?: any) {
-  const mapper: (issue: $ZodIssue) => any =
-    _mapper ||
-    function (issue: $ZodIssue) {
-      return issue.message;
-    };
+export function formatError<T, U>(error: $ZodError<T>, mapper = (issue: $ZodIssue) => issue.message as U) {
   const fieldErrors: $ZodFormattedError<T> = { _errors: [] } as any;
   const processError = (error: { issues: $ZodIssue[] }) => {
     for (const issue of error.issues) {
@@ -307,13 +302,8 @@ export type $ZodErrorTree<T, U = string> = T extends util.Primitive
 
 export function treeifyError<T>(error: $ZodError<T>): $ZodErrorTree<T>;
 export function treeifyError<T, U>(error: $ZodError<T>, mapper?: (issue: $ZodIssue) => U): $ZodErrorTree<T, U>;
-export function treeifyError<T>(error: $ZodError, _mapper?: any) {
-  const mapper: (issue: $ZodIssue) => any =
-    _mapper ||
-    function (issue: $ZodIssue) {
-      return issue.message;
-    };
-  const result: $ZodErrorTree<T> = { errors: [] } as any;
+export function treeifyError<T, U>(error: $ZodError<T>, mapper = (issue: $ZodIssue) => issue.message as U) {
+  const result: $ZodErrorTree<T, U> = { errors: [] } as any;
   const processError = (error: { issues: $ZodIssue[] }, path: PropertyKey[] = []) => {
     for (const issue of error.issues) {
       if (issue.code === "invalid_union" && issue.errors.length) {