[Issue 24798] New: std.algorithm.substitute appears to be destroying an already destroyed value

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24798

          Issue ID: 24798
           Summary: std.algorithm.substitute appears to be destroying an
                    already destroyed value
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: phobos
          Assignee: nobody at puremagic.com
          Reporter: issues.dlang at jmdavisProg.com

This code fails the assertion in the destructor:

---
void main()
{
    import std.algorithm.comparison : equal;
    import std.algorithm.iteration : substitute;

    static struct S
    {
        int val;
        ~this()
        {
            assert(val != 99);
            val = 99;
        }
    }

    auto arr = [S(0), S(1), S(2), S(3)];
    assert(equal(arr.substitute(S(1), S(42)),
                 [S(0), S(42), S(2), S(3)]));
}
---

So, it would appear that substitute is somehow destroying an already destroyed
value.

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