Unable to use nullable reference with lookup

[Martmists-GH]

Definition:

object CommentTable : LongIdTable() {
    val post = reference("post", PostTable)
    val parent = reference("parent", CommentTable).nullable()
    val author = reference("author", UserTable)
    val content = text("content")
    val created = datetime("created")
    val updated = datetime("updated")
}

Code:

val comments = CommentTable.select { CommentTable.post eq id and (CommentTable.parent eq null) }

Error:

Overload resolution ambiguity: 
public open fun <T : Comparable<TypeVariable(T)>, E : EntityID<TypeVariable(T)>?> ExpressionWithColumnType<TypeVariable(E)>.eq(t: TypeVariable(T)?): Op<Boolean> defined in org.jetbrains.exposed.sql.SqlExpressionBuilder
public open fun <T> ExpressionWithColumnType<TypeVariable(T)>.eq(t: TypeVariable(T)): Op<Boolean> defined in org.jetbrains.exposed.sql.SqlExpressionBuilder

Additionally, when setting this field:

it[CommentTable.parent] = payload.parent

Type mismatch: inferred type is Long? but TypeVariable(S) was expected

[naftalmm]

As a workaround for select expression, you may use the following:

val comments = CommentTable.select { (CommentTable.post eq id) and CommentTable.parent.isNull() }

But it's not clear what's the problem with setting this field. What is payload? Could you provide a minimal reproducible example for this (preferably in a separate issue)?