From ccadb6075d6977c4921ffc09fa40f515f4d497c5 Mon Sep 17 00:00:00 2001
From: Josh Goldberg <me@joshuakgoldberg.com>
Date: Fri, 22 Apr 2022 14:15:40 -0400
Subject: [PATCH] fix(eslint-plugin): [no-misused-promises] prioritize false
 returns when checking whether a function returns only void (#4841)

* fix(eslint-plugin): prioritize false returns when checking whether a function returns only void

* Update packages/eslint-plugin/tests/rules/no-misused-promises.test.ts

Co-authored-by: Brad Zacher <brad.zacher@gmail.com>

Co-authored-by: Brad Zacher <brad.zacher@gmail.com>
---
 .../eslint-plugin/src/rules/no-misused-promises.ts   |  9 +++++----
 .../tests/rules/no-misused-promises.test.ts          | 12 ++++++++++++
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/packages/eslint-plugin/src/rules/no-misused-promises.ts b/packages/eslint-plugin/src/rules/no-misused-promises.ts
index 5ef86bff0a8..03b166ec49b 100644
--- a/packages/eslint-plugin/src/rules/no-misused-promises.ts
+++ b/packages/eslint-plugin/src/rules/no-misused-promises.ts
@@ -537,6 +537,8 @@ function isVoidReturningFunctionType(
   node: ts.Node,
   type: ts.Type,
 ): boolean {
+  let hadVoidReturn = false;
+
   for (const subType of tsutils.unionTypeParts(type)) {
     for (const signature of subType.getCallSignatures()) {
       const returnType = signature.getReturnType();
@@ -547,12 +549,11 @@ function isVoidReturningFunctionType(
         return false;
       }
 
-      if (tsutils.isTypeFlagSet(returnType, ts.TypeFlags.Void)) {
-        return true;
-      }
+      hadVoidReturn ||= tsutils.isTypeFlagSet(returnType, ts.TypeFlags.Void);
     }
   }
-  return false;
+
+  return hadVoidReturn;
 }
 
 /**
diff --git a/packages/eslint-plugin/tests/rules/no-misused-promises.test.ts b/packages/eslint-plugin/tests/rules/no-misused-promises.test.ts
index f643f4d91e1..518b7c1d6b5 100644
--- a/packages/eslint-plugin/tests/rules/no-misused-promises.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-misused-promises.test.ts
@@ -304,6 +304,18 @@ declare const it: ItLike;
 it('', async () => {});
       `,
     },
+    {
+      code: `
+interface Props {
+  onEvent: (() => void) | (() => Promise<void>);
+}
+
+declare function Component(props: Props): any;
+
+const _ = <Component onEvent={async () => {}} />;
+      `,
+      filename: 'react.tsx',
+    },
   ],
 
   invalid: [