generated IDs in Repeater.SeparatorTemplate are not unique

[exyi]

see the AutomaticIdGeneration_Repeater test

<dot:Repeater DataSource={value: ...} id=myRepeater>
    <ItemTemplate> ... </ItemTemplate>
    <SeparatorTemplate> <span id=mySpan_sep></span> </SeparatorTemplate>
</dot:Repeater>

produces multiple mySpan_sep elements without trying to avoid the ID conflict. It is the same in client-side and server-side rendering.