params within repeat aren't handled correctly

[kanitw]

In this spec, we get Duplicate signal name: "hoverhighlight_tuple" error.

[mattijn]

To add: this only happens when the repeat operator is defined using the layer property. Simplified example using a column repeater that works fine:

"repeat": {"column": ["US Gross", "Worldwide Gross"]}

Open the Chart in the Vega Editor

But after changing the repeater into a layer the error occurs:

"repeat": {"layer": ["US Gross", "Worldwide Gross"]}

Duplicate signal name: "HOVER_tuple"

Open the Chart in the Vega Editor