private modifier in interfaces: check for modifier combinations, body (IDEA-164596)

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/advHighlighting9/PrivateInInterfaces.java

@@ -1,3 +1,15 @@
 interface A {
     private void m() {}
+}
+
+interface B {
+    <error descr="Private methods in interfaces should have a body">private void m()</error>;
+}
+
+interface C {
+    private <error descr="Illegal combination of modifiers: 'default' and 'private'">default</error> void m() {}
+}
+
+interface D {
+    private static void m() {}
 }