Non-sensical destructuring fails with surprising error message

Not sure what my expected behaviour here would be, but if an error is to be raised, I'd expect an error message saying something like 'It doesn't make sense to destructure a number'

For info, this is caused by applying the type-hint here

which is no longer needed, since we call `seq` on `gmap` here

FWIW the same code runs and compiles without errors in Clojurescript