Algebraic replacement

[Freddy via Digitalmars-d]

On Wednesday, 8 July 2015 at 21:34:01 UTC, Andrei Alexandrescu 
wrote:
> What's unsafe about it?

peek returns a pointer to a stack variable

import std.variant;
import std.stdio;

void main()
{
     Algebraic!(int,string) a = "a";
     string* b = a.peek!string;
     a = 0;
     writeln(b.length);
}