From 547b4bed87bf12c87f22c793b4995b9fe486b984 Mon Sep 17 00:00:00 2001
From: pipopotamasu <ec0156hx@gmail.com>
Date: Tue, 27 Feb 2024 21:54:36 -0500
Subject: [PATCH] improve return statement type

---
 rules/helper.ts                                   |  6 +++---
 .../return-statement/index.spec.ts                |  9 ++-------
 rules/no-implicit-any/return-statement/index.ts   | 15 +++++++++++++--
 3 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/rules/helper.ts b/rules/helper.ts
index a2bdf21..77c84fa 100644
--- a/rules/helper.ts
+++ b/rules/helper.ts
@@ -1,15 +1,15 @@
 import { type TSESTree, AST_NODE_TYPES } from '@typescript-eslint/types';
 import type { CompilerOptions } from 'typescript';
 
-function isNull(node: TSESTree.Expression) {
+export function isNull(node: TSESTree.Expression) {
   return node.type === AST_NODE_TYPES.Literal && node.value === null;
 }
 
-function isUndefined(node: TSESTree.Expression) {
+export function isUndefined(node: TSESTree.Expression) {
   return node.type === AST_NODE_TYPES.Identifier && node.name === 'undefined';
 }
 
-function isVoid(node: TSESTree.Expression) {
+export function isVoid(node: TSESTree.Expression) {
   return node.type === AST_NODE_TYPES.UnaryExpression && node.operator === 'void';
 }
 
diff --git a/rules/no-implicit-any/return-statement/index.spec.ts b/rules/no-implicit-any/return-statement/index.spec.ts
index d6852ef..daa02ce 100644
--- a/rules/no-implicit-any/return-statement/index.spec.ts
+++ b/rules/no-implicit-any/return-statement/index.spec.ts
@@ -128,17 +128,12 @@ ruleTester.run('return-statement', rule, {
   invalid: [
     {
       code: 'const foo = () => { return null }',
-      output: 'const foo = () => { return null as any }',
-      errors: [{ messageId: 'missingAnyType' }],
-    },
-    {
-      code: 'const foo = () => { return null; }',
-      output: 'const foo = () => { return null as any; }',
+      output: 'const foo = () => { return null as null }',
       errors: [{ messageId: 'missingAnyType' }],
     },
     {
       code: 'const foo = () => { return undefined }',
-      output: 'const foo = () => { return undefined as any }',
+      output: 'const foo = () => { return undefined as undefined }',
       errors: [{ messageId: 'missingAnyType' }],
     },
     {
diff --git a/rules/no-implicit-any/return-statement/index.ts b/rules/no-implicit-any/return-statement/index.ts
index 7d4a99f..fac7d4e 100644
--- a/rules/no-implicit-any/return-statement/index.ts
+++ b/rules/no-implicit-any/return-statement/index.ts
@@ -1,6 +1,11 @@
 import { ESLintUtils, type TSESLint } from '@typescript-eslint/utils';
 import { type TSESTree, AST_NODE_TYPES } from '@typescript-eslint/types';
-import { isNullOrUndefinedOrVoid, enabledStrictNullChecks } from '../../helper';
+import {
+  isNullOrUndefinedOrVoid,
+  isNull,
+  isUndefined,
+  enabledStrictNullChecks,
+} from '../../helper';
 
 function hasTypeAnnotationInAncestors(node: TSESTree.Node) {
   if (node === null) {
@@ -74,6 +79,12 @@ function getReturnStatementNodes(nodes: TSESTree.Statement[]) {
   return returnStatementNodes.flat(Infinity).filter(Boolean);
 }
 
+function getCastType(node: TSESTree.Expression) {
+  if (isNull(node)) return 'null';
+  if (isUndefined(node)) return 'undefined';
+  return 'any';
+}
+
 function isAllNullOrUndefinedOrVoid(node: TSESTree.LogicalExpression) {
   const { left, right } = node;
   if (left.type === AST_NODE_TYPES.LogicalExpression) {
@@ -120,7 +131,7 @@ export const lintReturnStatement = (
       node: node,
       messageId: 'missingAnyType',
       fix(fixer) {
-        return fixer.insertTextAfter(node.argument, ' as any');
+        return fixer.insertTextAfter(node.argument, ` as ${getCastType(node.argument)}`);
       },
     });
   }