fix #27382, tweak inference heuristic when we have no upper bound info

pkg/analyzer/test/src/task/strong/inferred_type_test.dart

Index: pkg/analyzer/test/src/task/strong/inferred_type_test.dart
diff --git a/pkg/analyzer/test/src/task/strong/inferred_type_test.dart b/pkg/analyzer/test/src/task/strong/inferred_type_test.dart
index 85ee428d6c14cad827bb593b7b1c9e934865174d..640ded44e484b9994cadb3e2a920fb6b5c0f6a76 100644
--- a/pkg/analyzer/test/src/task/strong/inferred_type_test.dart
+++ b/pkg/analyzer/test/src/task/strong/inferred_type_test.dart
@@ -1767,6 +1767,20 @@ class C extends A {}
     ''');
   }
 
+  void test_genericFunctions_returnTypedef() {
+    checkFile(r'''
+typedef void ToValue<T>(T value);
+
+main() {
+  ToValue/*<T>*/ f/*<T>*/(dynamic /*=T*/ x) => null;
+  var x = f/*<int>*/(42);
+  var y = f(42);
+  ToValue<int> takesInt = x;
+  takesInt = y;
+}
+    ''');
+  }
+
   void test_genericMethods_basicDownwardInference() {
     checkFile(r'''
 /*=T*/ f/*<S, T>*/(/*=S*/ s) => null;