From 85d405a1d74c0730a9d8d6307b26e8d6f3f75421 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20Burzy=C5=84ski?= <mateuszburzynski@gmail.com>
Date: Tue, 18 Oct 2022 23:10:03 +0200
Subject: [PATCH] Fixed a false positive "await has no effect on the type"
 diagnostic with mixed generic union (#50833)

---
 src/compiler/checker.ts                              |  2 +-
 .../codeFixRemoveUnnecessaryAwait_mixedUnion.ts      | 12 ++++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)
 create mode 100644 tests/cases/fourslash/codeFixRemoveUnnecessaryAwait_mixedUnion.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 94e891ea255a9..ee02a3532eb3a 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -37104,7 +37104,7 @@ namespace ts {
                 // We only need `Awaited<T>` if `T` is a type variable that has no base constraint, or the base constraint of `T` is `any`, `unknown`, `{}`, `object`,
                 // or is promise-like.
                 if (baseConstraint ?
-                    baseConstraint.flags & TypeFlags.AnyOrUnknown || isEmptyObjectType(baseConstraint) || isThenableType(baseConstraint) :
+                    baseConstraint.flags & TypeFlags.AnyOrUnknown || isEmptyObjectType(baseConstraint) || someType(baseConstraint, isThenableType) :
                     maybeTypeOfKind(type, TypeFlags.TypeVariable)) {
                     return true;
                 }
diff --git a/tests/cases/fourslash/codeFixRemoveUnnecessaryAwait_mixedUnion.ts b/tests/cases/fourslash/codeFixRemoveUnnecessaryAwait_mixedUnion.ts
new file mode 100644
index 0000000000000..605e5b97481aa
--- /dev/null
+++ b/tests/cases/fourslash/codeFixRemoveUnnecessaryAwait_mixedUnion.ts
@@ -0,0 +1,12 @@
+/// <reference path="fourslash.ts" />
+
+// @target: esnext
+//// async function fn1(a: Promise<void> | void) {
+////   await a;
+//// }
+////
+//// async function fn2<T extends Promise<void> | void>(a: T) {
+////   await a;
+//// }
+
+verify.getSuggestionDiagnostics([]);