new inference: initial tests

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/genericsHighlighting8/IDEA18425.java

@@ -0,0 +1,15 @@
+public abstract class BiFunction<A,B> {
+    public abstract B apply(A a);
+    public abstract A unapply(B b);
+    public BiFunction<B,A> flip() {
+        return new BiFunction<B, A>() {
+            public A apply(B b) {
+                return BiFunction.this.unapply(b);
+            }
+
+            public B unapply(A a) {
+                return BiFunction.this.apply(a);
+            }
+        };
+    }
+}