[FIR2IR] Temporary fix of createIrEnumEntry

Check if a bound entry with the same signature is already exist

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrClassifierStorage.kt

@@ -535,6 +535,11 @@ class Fir2IrClassifierStorage(
     ): IrEnumEntry {
         return enumEntry.convertWithOffsets { startOffset, endOffset ->
             val signature = signatureComposer.composeSignature(enumEntry, forceTopLevelPrivate = forceTopLevelPrivate)
+            if (signature != null) {
+                // Compilation of kotlinx-serialization-protobuf fails with "already bound" exception if this check is removed
+                // TODO: get rid of this check
+                symbolTable.referenceEnumEntryIfAny(signature)?.let { if (it.isBound) return@convertWithOffsets it.owner }
+            }
             val result = declareIrEnumEntry(signature) { symbol ->
                 val origin = enumEntry.computeIrOrigin(predefinedOrigin)
                 irFactory.createEnumEntry(

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/SymbolTable.kt

@@ -664,6 +664,10 @@ open class SymbolTable(
             else IrEnumEntrySymbolImpl()
         }
 
+    fun referenceEnumEntryIfAny(sig: IdSignature): IrEnumEntrySymbol? {
+        return enumEntrySymbolTable.get(sig)
+    }
+
     val unboundEnumEntries: Set<IrEnumEntrySymbol> get() = enumEntrySymbolTable.unboundSymbols
 
     private fun createFieldSymbol(descriptor: PropertyDescriptor, signature: IdSignature?): IrFieldSymbol =