I accidentally found that I was implicitly casting in my code a const vibed Json type to a mutable Json type.

I thought "that can't be right, how does that even work? Especially if the Json is an object or an array!".

But it does. At least since 2014.

See https://issues.dlang.org/show_bug.cgi?id=12885

Enjoy a nice cast-free way to use sumtype to unconstify references in @safe code!

import std.sumtype;

void main() @safe
{
    alias MyType = SumType!(int, char[]);
    auto mt = const(MyType)("hello");
    MyType m2 = mt;
    char[] result = m2.tryMatch!((char[] a) => a);
    result[0] = 'j'; // segfault
}

-Steve

On Sunday, 15 May 2022 at 02:41:34 UTC, Steven Schveighoffer wrote:

import std.sumtype;

void main() @safe
{
    alias MyType = SumType!(int, char[]);
    auto mt = const(MyType)("hello");
    MyType m2 = mt;
    char[] result = m2.tryMatch!((char[] a) => a);
    result[0] = 'j'; // segfault
}

And the one pull request that should've fixed it has been closed (not merged) and with no further update or explanation.

https://github.com/dlang/dmd/pull/9061