I see typed global variables as replacement for writing

  const x = Ref{Int}(1)

and then mutating it as `x[] += 1`. With the type annotated globals, we'll be able to simply write

  x::Int = 1

and rebind it as `x += 1`. Besides the syntactic advantage, this way is threadsafe by default whereas mutating a constant global `Ref` is not threadsafe.