move code to util

packages/eslint-plugin/src/rules/no-for-in-array.ts

@@ -1,13 +1,12 @@
-import type { TSESTree } from '@typescript-eslint/utils';
 import * as ts from 'typescript';
 
 import {
   createRule,
   getConstrainedTypeAtLocation,
   getParserServices,
   isTypeArrayTypeOrUnionOfArrayTypes,
-  nullThrows,
 } from '../util';
+import { getForStatementHeadLoc } from '../util/getForStatementHeadLoc';
 
 export default createRule({
   name: 'no-for-in-array',
@@ -26,22 +25,6 @@ export default createRule({
   },
   defaultOptions: [],
   create(context) {
-    function getReportLoc(
-      forInNode: TSESTree.ForInStatement,
-    ): TSESTree.SourceLocation {
-      const closingParens = nullThrows(
-        context.sourceCode.getTokenBefore(
-          forInNode.body,
-          token => token.value === ')',
-        ),
-        'for-in must have a closing parenthesis.',
-      );
-      return {
-        start: structuredClone(forInNode.loc.start),
-        end: structuredClone(closingParens.loc.end),
-      };
-    }
-
     return {
       ForInStatement(node): void {
         const services = getParserServices(context);
@@ -54,7 +37,7 @@ export default createRule({
           (type.flags & ts.TypeFlags.StringLike) !== 0
         ) {
           context.report({
-            loc: getReportLoc(node),
+            loc: getForStatementHeadLoc(context.sourceCode, node),
             messageId: 'forInViolation',
           });
         }

packages/eslint-plugin/src/util/getForStatementHeadLoc.ts

@@ -0,0 +1,34 @@
+import type { TSESLint, TSESTree } from '@typescript-eslint/utils';
+import { nullThrows } from '@typescript-eslint/utils/eslint-utils';
+
+/**
+ * Gets the location of the head of the given for statement variant for reporting.
+ *
+ * - `for (const foo in bar) expressionOrBlock`
+ *    ^^^^^^^^^^^^^^^^^^^^^^
+ *
+ * - `for (const foo of bar) expressionOrBlock`
+ *    ^^^^^^^^^^^^^^^^^^^^^^
+ *
+ * - `for await (const foo of bar) expressionOrBlock`
+ *    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ *
+ * - `for (let i = 0; i < 10; i++) expressionOrBlock`
+ *    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ */
+export function getForStatementHeadLoc(
+  sourceCode: TSESLint.SourceCode,
+  node:
+    | TSESTree.ForInStatement
+    | TSESTree.ForOfStatement
+    | TSESTree.ForStatement,
+): TSESTree.SourceLocation {
+  const closingParens = nullThrows(
+    sourceCode.getTokenBefore(node.body, token => token.value === ')'),
+    'for statement must have a closing parenthesis.',
+  );
+  return {
+    start: structuredClone(node.loc.start),
+    end: structuredClone(closingParens.loc.end),
+  };
+}