[TypeChecker] NFC: Add a test-case for rdar://83666783

Author: xedin

validation-test/Sema/type_checker_crashers_fixed/rdar83666783.swift

@@ -0,0 +1,16 @@
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) %s -typecheck -verify
+// REQUIRES: objc_interop
+
+import Foundation
+
+struct S {
+  var test: CGFloat
+}
+
+func compute(_: Double?) -> Double? {
+  return 42
+}
+
+func test(s: S?) {
+  _ = compute(s?.test) // expected-error {{cannot implicitly convert value of type 'CGFloat?' to expected type 'Double?'}}
+}