As an alternative or addition to the notion of having hover-based auto visualization, have a way to enable a mode where all possible autos will reveal their deduced types.
This could either be done by replacing the 'auto' with a stylized representation of the actual type which would have a "solidify" the type by replacing the underlying "auto" with the actual type.
Or it could be tooltip-like boxes appearing above/below the type.
Ultimately, when it's 3am in the morning and I'm trying to fix some crazy dense complex uber-algorithm, "auto" needs to go away for a bit, and having to mouse over every line of code is not a great solution in that scenario.
We are considering adding a refactoring command to replace "auto" with the actual type, so if this was applied to a block of code, it would achieve the same result, but at the cost of editing the code: