Fixed a false positive "await has no effect on the type" diagnostic w…

…ith mixed generic union (#50833)
microsoft · Oct 18, 2022 · 85d405a · 85d405a
1 parent 1f8959f
commit 85d405a
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Showing 2 changed files with 13 additions and 1 deletion.
diff --git 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
@@ -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([]);