Destructor call

[n0fun via Digitalmars-d-learn]

import std.stdio;

struct S(alias n) {
    this(int) {
        throw new Exception("Exception");
    }
    ~this() {
        writeln("destructor " ~ n);
    }
}
void main() {
    writeln("--- 1 ---");
    try {
        auto s = S!"1"(0);
    } catch (Exception) {}
    writeln("--- 2 ---");
    try {
        auto s = new S!"2"(0);
    } catch (Exception) {}
}

Output:
--- 1 ---
--- 2 ---
destructor 2

Why the destructor is called in the second case and why not in 
the first?
How to design structs with such different behavior?