FIR: handle varargs properly during annotation serialization

compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/constant/FirToConstantValueTransformer.kt

@@ -8,9 +8,8 @@ package org.jetbrains.kotlin.fir.serialization.constant
 import org.jetbrains.kotlin.fir.FirElement
 import org.jetbrains.kotlin.fir.declarations.FirEnumEntry
 import org.jetbrains.kotlin.fir.expressions.*
-import org.jetbrains.kotlin.fir.types.classId
-import org.jetbrains.kotlin.fir.types.coneType
-import org.jetbrains.kotlin.fir.types.coneTypeUnsafe
+import org.jetbrains.kotlin.fir.render
+import org.jetbrains.kotlin.fir.types.*
 import org.jetbrains.kotlin.fir.visitors.FirDefaultVisitor
 import org.jetbrains.kotlin.types.ConstantValueKind
 
@@ -21,7 +20,7 @@ internal object FirToConstantValueTransformer : FirDefaultVisitor<ConstantValue<
         element: FirElement,
         data: Nothing?
     ): ConstantValue<*>? {
-        error("Illegal element as annotation argument: ${element::class.qualifiedName}")
+        error("Illegal element as annotation argument: ${element::class.qualifiedName} -> ${element.render()}")
     }
 
     @OptIn(ExperimentalUnsignedTypes::class)
@@ -76,8 +75,22 @@ internal object FirToConstantValueTransformer : FirDefaultVisitor<ConstantValue<
     ): ConstantValue<*>? {
         val symbol = qualifiedAccessExpression.toResolvedCallableSymbol() ?: return null
         val enumEntry = symbol.fir as? FirEnumEntry ?: return null
-        val classId = enumEntry.returnTypeRef.coneType.classId ?: return null
+        val classId = enumEntry.returnTypeRef.coneTypeSafe<ConeClassLikeType>()?.classId ?: return null
         val outerClassId = classId.outerClassId ?: return null
         return EnumValue(outerClassId, enumEntry.name)
     }
+
+    override fun visitFunctionCall(
+        functionCall: FirFunctionCall,
+        data: Nothing?
+    ): ConstantValue<*>? {
+        return visitQualifiedAccessExpression(functionCall, data)
+    }
+
+    override fun visitVarargArgumentsExpression(
+        varargArgumentsExpression: FirVarargArgumentsExpression,
+        data: Nothing?
+    ): ConstantValue<*> {
+        return ArrayValue(varargArgumentsExpression.arguments.mapNotNull { it.accept(this, null) })
+    }
 }