Ambiguity with Task.Run

Question

This line in main

Task.Run(f);

with this function in the same class Program

static int f() { return 0; }

causes this compile error (there are no other methods called f in Program):

CS0121 The call is ambiguous between the following methods or properties: 'Task.Run<TResult>(Func<TResult>)' and 'Task.Run(Func<Task>)'

Isn't it obviously Func<int> and not Func<Task>?

However, all of these work:

Task.Run(() => 0);
Task.Run(() => f());
Task.Run(async () => f());