FE: add test for KT-55251

compiler/testData/diagnostics/tests/enum/entries/entriesUnsupported.fir.kt

@@ -0,0 +1,11 @@
+// !LANGUAGE: -EnumEntries
+// WITH_STDLIB
+// ISSUE: KT-55251
+
+enum class Foo {
+    BAR;
+}
+
+fun main() {
+    Foo.<!OPT_IN_USAGE_ERROR!>entries<!>
+}

compiler/testData/diagnostics/tests/enum/entries/entriesUnsupported.kt

@@ -0,0 +1,11 @@
+// !LANGUAGE: -EnumEntries
+// WITH_STDLIB
+// ISSUE: KT-55251
+
+enum class Foo {
+    BAR;
+}
+
+fun main() {
+    Foo.<!UNRESOLVED_REFERENCE!>entries<!>
+}

compiler/testData/diagnostics/tests/enum/entries/entriesUnsupported.txt

@@ -0,0 +1,23 @@
+package
+
+public fun main(): kotlin.Unit
+
+public final enum class Foo : kotlin.Enum<Foo> {
+    enum entry BAR
+
+    private constructor Foo()
+    @kotlin.internal.IntrinsicConstEvaluation public final override /*1*/ /*fake_override*/ val name: kotlin.String
+    public final override /*1*/ /*fake_override*/ val ordinal: kotlin.Int
+    protected final override /*1*/ /*fake_override*/ fun clone(): kotlin.Any
+    public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: Foo): kotlin.Int
+    public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    protected/*protected and package*/ final override /*1*/ /*fake_override*/ /*isHiddenForResolutionEverywhereBesideSupercalls*/ fun finalize(): kotlin.Unit
+    public final override /*1*/ /*fake_override*/ /*isHiddenForResolutionEverywhereBesideSupercalls*/ fun getDeclaringClass(): java.lang.Class<Foo!>!
+    public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    // Static members
+    public final /*synthesized*/ val entries: kotlin.enums.EnumEntries<Foo>
+    public final /*synthesized*/ fun valueOf(/*0*/ value: kotlin.String): Foo
+    public final /*synthesized*/ fun values(): kotlin.Array<Foo>
+}