Generic function to double a value

Mojo
1

See the following functions. dbl2 works with SIMD inputs, but dbl does not compile: error: expected a type, not a value.
How can I implement this generic dbl without using SIMD types?

fn dbl[T: DType](x: T) -> T:
    return 2*x

fn dbl2[T: DType](x: Scalar[T]) -> Scalar[T]:
    return 2*x

fn main():
    var x = 4
    var y = dbl(x)
    print(y)

    var x2 = SIMD[DType.float32, 1](4)
    var y2 = dbl2(x2)
    print(y2)