On 22.12.20 04:56, 9il wrote:
6. Algebraic type subsets are supported by `get`, `trustedGet`, `_is`,
and `this` primitives. You can operate with algebraic subset as with the
type of the original typeset. [1]
"trustedGet" - That name smells of a safety violation. And indeed
(compile with `-release`):
----
import mir.algebraic;
import std.stdio;
void main() @safe
{
immutable int* x = new int(42);
Variant!(size_t, int*) v;
v = cast(size_t) x;
auto p = v.trustedGet!(int*); /* uh-oh */
*p = 13; /* mutating immutable */
writeln(*x); /* prints "13" */
}
----
The normal `get` also violates safety by giving out references into the
union (compile with `-preview=dip1000`):
----
import mir.algebraic;
import std.stdio;
T* ref_to_ptr(T)(ref T r) @safe { return &r; }
void main() @safe
{
immutable int* x = new int(42);
Variant!(size_t, int*) v;
int** p = ref_to_ptr(v.get!(int*)); /* uh-oh */
v = cast(size_t) x;
**p = 13; /* mutating immutable */
writeln(*x); /* prints "13" */
}
----
But that might be an issue with DIP1000. `ref_to_ptr` is a hint that
something isn't right in that area.
