Allow KtEnumEntry...RefExpression.referencedElement be nullable

This commit fixes KNPE provoked by RemoveExplicitTypeArgumentsIntention
#KT-29735 Fixed

compiler/psi/src/org/jetbrains/kotlin/psi/KtEnumEntrySuperclassReferenceExpression.kt

@@ -36,8 +36,8 @@ class KtEnumEntrySuperclassReferenceExpression :
             super(stub, KtStubElementTypes.ENUM_ENTRY_SUPERCLASS_REFERENCE_EXPRESSION)
 
     // It is the owner enum class (not an enum entry but the whole enum)
-    private val referencedElement: KtClass
-        get() = calcReferencedElement()!!
+    private val referencedElement: KtClass?
+        get() = calcReferencedElement()
 
     private fun calcReferencedElement(): KtClass? {
         val owner = this.getStrictParentOfType<KtEnumEntry>()
@@ -54,15 +54,15 @@ class KtEnumEntrySuperclassReferenceExpression :
     }
 
     override fun getReferencedNameAsName(): Name {
-        return referencedElement.name?.let { Name.identifier(it) } ?: SpecialNames.NO_NAME_PROVIDED
+        return referencedElement?.name?.let { Name.identifier(it) } ?: SpecialNames.NO_NAME_PROVIDED
     }
 
     override fun getReferencedNameElement(): PsiElement {
-        return referencedElement
+        return referencedElement!!
     }
 
     override fun getIdentifier(): PsiElement? {
-        return referencedElement.nameIdentifier
+        return referencedElement?.nameIdentifier
     }
 
     override fun getReferencedNameElementType(): IElementType {

idea/testData/intentions/removeExplicitTypeArguments/inspectionData/expected.xml

@@ -223,4 +223,14 @@
     <problem_class severity="WARNING" attribute_key="NOT_USED_ELEMENT_ATTRIBUTES">Unnecessary type argument</problem_class>
     <description>Remove explicit type arguments</description>
   </problem>
+
+  <problem>
+    <file>kt29735.kt</file>
+    <line>4</line>
+    <module>light_idea_test_case</module>
+    <package>kt29735</package>
+    <entry_point TYPE="file" FQNAME="kt29735.kt" />
+    <problem_class severity="WARNING" attribute_key="NOT_USED_ELEMENT_ATTRIBUTES">Unnecessary type argument</problem_class>
+    <description>Remove explicit type arguments</description>
+  </problem>
 </problems>

idea/testData/intentions/removeExplicitTypeArguments/kt29735.kt

@@ -0,0 +1,5 @@
+// WITH_RUNTIME
+
+enum class A(val strings: List<String>) {
+    B(listOf<Str<caret>ing>(""))
+}

idea/testData/intentions/removeExplicitTypeArguments/kt29735.kt.after

@@ -0,0 +1,5 @@
+// WITH_RUNTIME
+
+enum class A(val strings: List<String>) {
+    B(listOf(""))
+}

idea/tests/org/jetbrains/kotlin/idea/intentions/IntentionTestGenerated.java

@@ -14492,6 +14492,11 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
             runTest("idea/testData/intentions/removeExplicitTypeArguments/insideOtherCall.kt");
         }
 
+        @TestMetadata("kt29735.kt")
+        public void testKt29735() throws Exception {
+            runTest("idea/testData/intentions/removeExplicitTypeArguments/kt29735.kt");
+        }
+
         @TestMetadata("kt31441.kt")
         public void testKt31441() throws Exception {
             runTest("idea/testData/intentions/removeExplicitTypeArguments/kt31441.kt");