infer generic functional types by lambda's formal parameters and exact method refs

java/java-tests/testData/refactoring/introduceVariable/MethodRefNotInContextInferred.after.java

@@ -0,0 +1,7 @@
+import java.util.function.Consumer;
+
+class Foo {
+    void test() {
+        Consumer<Integer> l = System::exit;
+    }
+}