method refs: turn highlighting on; check valid context

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/methodRef/ValidContext.java

@@ -0,0 +1,17 @@
+public class Test {
+  {
+    if (<error descr="Method reference expression is not expected here">Test::length instanceof String</error>) {
+    }
+    bar(Test::length);
+  }
+
+  public static Integer length(String s) {
+    return s.length();
+  }
+  
+  public static void bar(Bar bar) {}
+  
+  interface Bar {
+    Integer _(String s);
+  }
+}