[Issue 24433] New: Array value assignment is incorrect for structs with destructors and copy constructors

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24433

          Issue ID: 24433
           Summary: Array value assignment is incorrect for structs with
                    destructors and copy constructors
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Severity: major
          Priority: P1
         Component: druntime
          Assignee: nobody at puremagic.com
          Reporter: artha at samerion.com

If a struct defines both (1) a destructor and (2) a postblit or copy
constructor, assigning it as a value to a slice will produce an invalid result:

```
import std.stdio;

struct Uncopiable {
    int value;

    ~this() {
    }

    @disable this(const ref Uncopiable);

}

void testCopy(Uncopiable unc) {}

void main() {

    auto a = Uncopiable(1);
    auto b = Uncopiable(2);    
    //testCopy(a);  // fails, alright

    auto c = [Uncopiable(3)];
    c[] = a;   
    writeln(c[0].value);  // Prints 3 instead of 1
    writeln(a.value); // Prints 3 instead of 1
}
```

Removing either the destructor or copy constructor fixes the above problem. The
issue also occurs if the copy constructor is replaced with a postblit.

The bug appears to have been introduced in #14382 
https://github.com/dlang/dmd/commit/d0a367e98cc31a2675a5fc41a150dd38089f1982#diff-c9a721f453e1e17d997f8603ca3e4e65c765f0ebf0dd1cfb972ddddc959bdbb1

--