Here is an example:

```
mm(::Type{Tuple{X,Y}}) where X where Y = Type[X,Y]
julia> mm(Tuple{Int,T} where T<:Float64)
ERROR: UndefVarError: Y not defined
Stacktrace:
[1] mm(::Type{Tuple{Int64,T} where T<:Float64}) at ./none:1
[2] top-level scope at none:0
```

You can also try it with Base.unwrap_all, the result is same.

Thanks