Fix comment in union type get duplicated (#18393)

changelog_unreleased/typescript/18393.md

@@ -0,0 +1,13 @@
+#### Fix comment inside union type get duplicated (#18393 by @fisker)
+
+<!-- prettier-ignore -->
+```tsx
+// Input
+type Foo = (/** comment */ a | b) | c;
+
+// Prettier stable
+type Foo = /** comment */ (/** comment */ a | b) | c;
+
+// Prettier main
+type Foo = /** comment */ (a | b) | c;
+```