Prohibit callable references to object members

To be able to make them more useful in the future, i.e. bound to the object
instance

compiler/testData/diagnostics/tests/callableReference/objectMembersUnsupported.kt

@@ -0,0 +1,31 @@
+// !DIAGNOSTICS: -UNUSED_EXPRESSION
+
+import Obj.ext
+import A.Companion.ext2
+
+object Obj {
+    fun foo() {}
+    val bar = 2
+    val String.ext: String get() = this
+}
+
+class A {
+    companion object {
+        fun foo() {}
+        val bar = 2
+        val String.ext2: String get() = this
+    }
+}
+
+fun test() {
+    Obj::<!CALLABLE_REFERENCE_TO_OBJECT_MEMBER!>foo<!>
+    Obj::<!CALLABLE_REFERENCE_TO_OBJECT_MEMBER!>bar<!>
+    String::<!CALLABLE_REFERENCE_TO_OBJECT_MEMBER!>ext<!>
+
+    A.Companion::<!CALLABLE_REFERENCE_TO_OBJECT_MEMBER!>foo<!>
+    A.Companion::<!CALLABLE_REFERENCE_TO_OBJECT_MEMBER!>bar<!>
+    String::<!CALLABLE_REFERENCE_TO_OBJECT_MEMBER!>ext2<!>
+
+    A::<!UNRESOLVED_REFERENCE!>foo<!>
+    A::<!UNRESOLVED_REFERENCE!>bar<!>
+}