[FIR] refactoring, extract KtUserType -> FirUserTypeRef to a separate function in RawFirBuilder

^KT-58125

compiler/fir/raw-fir/psi2fir/src/org/jetbrains/kotlin/fir/builder/RawFirBuilder.kt

@@ -1972,29 +1972,9 @@ open class RawFirBuilder(
                     isMarkedNullable = isNullable
                 }
                 is KtUserType -> {
-                    var referenceExpression = unwrappedElement.referenceExpression
+                    val referenceExpression = unwrappedElement.referenceExpression
                     if (referenceExpression != null) {
-                        FirUserTypeRefBuilder().apply {
+                        convertKtTypeElement(source, isNullable, unwrappedElement, referenceExpression)
-                            this.source = source
-                            isMarkedNullable = isNullable
-                            var ktQualifier: KtUserType? = unwrappedElement
-
-                            do {
-                                val firQualifier = FirQualifierPartImpl(
-                                    referenceExpression!!.toFirSourceElement(),
-                                    referenceExpression!!.getReferencedNameAsName(),
-                                    FirTypeArgumentListImpl(ktQualifier?.typeArgumentList?.toKtPsiSourceElement() ?: source).apply {
-                                        typeArguments.appendTypeArguments(ktQualifier!!.typeArguments)
-                                    }
-                                )
-                                qualifier.add(firQualifier)
-
-                                ktQualifier = ktQualifier!!.qualifier
-                                referenceExpression = ktQualifier?.referenceExpression
-                            } while (referenceExpression != null)
-
-                            qualifier.reverse()
-                        }
                     } else {
                         FirErrorTypeRefBuilder().apply {
                             this.source = source
@@ -2049,6 +2029,36 @@ open class RawFirBuilder(
             return firTypeBuilder.build()
         }
 
+        private fun convertKtTypeElement(
+            source: KtPsiSourceElement,
+            isNullable: Boolean,
+            ktUserType: KtUserType,
+            reference: KtSimpleNameExpression,
+        ): FirUserTypeRefBuilder {
+            var referenceExpression: KtSimpleNameExpression? = reference
+            return FirUserTypeRefBuilder().apply {
+                this.source = source
+                isMarkedNullable = isNullable
+                var ktQualifier: KtUserType? = ktUserType
+
+                do {
+                    val firQualifier = FirQualifierPartImpl(
+                        referenceExpression!!.toFirSourceElement(),
+                        referenceExpression!!.getReferencedNameAsName(),
+                        FirTypeArgumentListImpl(ktQualifier?.typeArgumentList?.toKtPsiSourceElement() ?: source).apply {
+                            typeArguments.appendTypeArguments(ktQualifier!!.typeArguments)
+                        }
+                    )
+                    qualifier.add(firQualifier)
+
+                    ktQualifier = ktQualifier!!.qualifier
+                    referenceExpression = ktQualifier?.referenceExpression
+                } while (referenceExpression != null)
+
+                qualifier.reverse()
+            }
+        }
+
         override fun visitAnnotationEntry(annotationEntry: KtAnnotationEntry, data: FirElement?): FirElement {
             return buildAnnotationCall {
                 source = annotationEntry.toFirSourceElement()