moreSpecific: use site info to check assignability, prefer concrete to abstract methods (IDEA-57569)

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/advHighlighting7/ambiguousIDEA57569/pck/AmbiguousMethodCall.java

@@ -0,0 +1,11 @@
+package pck;
+abstract class C<T>  {
+    abstract Object foo(T x);
+    String foo(String x) { return null; }
+}
+
+class D extends C<String>{
+    {
+        foo("");
+    }
+}