I have three methods

```
julia> f(::T) where {T <: Int} = 2
f (generic function with 1 method)
julia> f(::T)::T where {T <: Float64} = 2.0
ERROR: UndefVarError: T not defined
Stacktrace:
[1] top-level scope at none:0
julia> f(::String)::T where {T <: String} = ""
f (generic function with 2 methods)
```

Why is the 2nd example not working? How can I fix it?

Julia version: 1.1.0