Issue 43717. Update UP(FunctionType, unrelated) to UP(Object, unrelated).

Bug: dart-lang/sdk#43717
Change-Id: Ib2fa861df24d010c768e4a06ba2bff175bbf88f4
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/166783
Reviewed-by: Samuel Rawlins <srawlins@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

Author: scheglov

pkg/analyzer/lib/src/dart/element/least_upper_bound.dart

@@ -667,10 +667,14 @@ class LeastUpperBoundHelper {
       return _functionType(T1, T2);
     }
 
-    // UP(T Function<...>(...), T2) = Object
-    // UP(T1, T Function<...>(...)) = Object
-    if (T1 is FunctionType || T2 is FunctionType) {
-      return _typeSystem.objectNone;
+    // UP(T Function<...>(...), T2) = UP(Object, T2)
+    if (T1 is FunctionType) {
+      return getLeastUpperBound(_typeSystem.objectNone, T2);
+    }
+
+    // UP(T1, T Function<...>(...)) = UP(T1, Object)
+    if (T2 is FunctionType) {
+      return getLeastUpperBound(T1, _typeSystem.objectNone);
     }
 
     // UP(T1, T2) = T2 if T1 <: T2

pkg/analyzer/test/src/dart/element/upper_lower_bound_test.dart

@@ -2000,6 +2000,20 @@ class UpperBound_FunctionTypes_Test extends _BoundsTestBase {
       );
     }
   }
+
+  test_unrelated() {
+    var T1 = functionTypeNone(returnType: intNone);
+
+    _checkLeastUpperBound(T1, intNone, objectNone);
+    _checkLeastUpperBound(T1, intQuestion, objectQuestion);
+    _checkLeastUpperBound(T1, intStar, objectStar);
+
+    _checkLeastUpperBound(
+      T1,
+      futureOrNone(functionQuestion),
+      objectQuestion,
+    );
+  }
 }
 
 @reflectiveTest