fix: add ESLint v8 compatible built-in rule imports

src/rules/noUnusedExpressions.js

@@ -1,12 +1,16 @@
 // A wrapper around ESLint's core rule no-unused-expressions, additionally ignores type cast
 // expressions.
 
-import coreNOE from 'eslint/lib/rules/no-unused-expressions';
+import {
+  getBuiltinRule,
+} from '../utilities/getBuiltinRule';
 
-const meta = coreNOE.meta;
+const noUnusedExpressionsRule = getBuiltinRule('no-unused-expressions');
+
+const meta = noUnusedExpressionsRule.meta;
 
 const create = (context) => {
-  const coreChecks = coreNOE.create(context);
+  const coreChecks = noUnusedExpressionsRule.create(context);
 
   return {
     ExpressionStatement (node) {

src/utilities/getBuiltinRule.js

@@ -0,0 +1,15 @@
+/* eslint-disable import/no-dynamic-require */
+
+/**
+ * Adopted from https://github.com/sindresorhus/eslint-plugin-unicorn/blob/main/rules/utils/get-builtin-rule.js.
+ */
+export const getBuiltinRule = (id) => {
+  // TODO: Remove this when we drop support for ESLint 7
+  const eslintVersion = require('eslint/package.json').version;
+  /* istanbul ignore next */
+  if (eslintVersion.startsWith('7.')) {
+    return require(`eslint/lib/rules/${id}`);
+  }
+
+  return require('eslint/use-at-your-own-risk').builtinRules.get(id);
+};

tests/rules/assertions/defineFlowType.js

@@ -1,7 +1,11 @@
 import {
   RuleTester,
 } from 'eslint';
-import noUndefRule from 'eslint/lib/rules/no-undef';
+import {
+  getBuiltinRule,
+} from '../../../src/utilities/getBuiltinRule';
+
+const noUndefRule = getBuiltinRule('no-undef');
 
 const VALID_WITH_DEFINE_FLOW_TYPE = [
   {

tests/rules/assertions/useFlowType.js

@@ -1,8 +1,12 @@
 import {
   RuleTester,
 } from 'eslint';
-import noUnusedVarsRule from 'eslint/lib/rules/no-unused-vars';
 import useFlowType from '../../../src/rules/useFlowType';
+import {
+  getBuiltinRule,
+} from '../../../src/utilities/getBuiltinRule';
+
+const noUnusedVarsRule = getBuiltinRule('no-unused-vars');
 
 const VALID_WITH_USE_FLOW_TYPE = [
   {