[Issue 23556] New: Array append ignores copy constructor

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23556

          Issue ID: 23556
           Summary: Array append ignores copy constructor
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: druntime
          Assignee: nobody at puremagic.com
          Reporter: snarwin+bugzilla at gmail.com

As of DMD 2.101.0, the following program compiles and runs successfully to
completion:

---
struct S
{
    this(ref S)
    {
        assert(0);
    }
}

void main()
{
    S[] a = [ S() ];
    auto p = a.ptr;
    // append until reallocation
    while (a.ptr == p)
        a ~= S(); // no assert
}
---

This program should assert at runtime when the array is reallocated, but does
not, because the copy constructors of the array's elements are not called.

If the copy constructor is changed to a postblit (`this(this)`), the program
asserts at runtime, as expected.

See also issue 20879, which affected .dup and .idup.

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