[TypeChecker] NFC: Add a test-case for rdar://110847476

Author: xedin

test/Constraints/pack-expansion-expressions.swift

@@ -722,3 +722,15 @@ do {
     _ = value.data.key // Ok
   }
 }
+
+// rdar://110847476 - unrelated assignment and raw representable diagnostics
+do {
+  struct Test<each Base: AsyncSequence> {
+    let base: (repeat each Base)
+
+    init(base: repeat each Base) {
+      self.base = base
+      // expected-error@-1 {{pack reference 'each Base' can only appear in pack expansion}}
+    }
+  }
+}