Deduce template arguments from return value?

[Yuxuan Shui via Digitalmars-d]

For example:
import std.conv;
T a(T)(int a) {
        return to!T(a);
}
void main(){
        string x = a(2);
}
D is not able to deduce T. Can we make it possible to deduce 
template arguments from where the return value is assigned to?

Rust is able to do this:
fn main() {
        let a : Vec<i32> = Vec::new();
}

(In fact, you can even do this is Rust:
fn main() {
        let mut a = Vec::new();
        a[0] = 0i32;
})