https://issues.dlang.org/show_bug.cgi?id=23382

          Issue ID: 23382
           Summary: Non-template requirement for copy constructors is
                    undocumented
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dlang.org
          Assignee: nobody@puremagic.com
          Reporter: snarwin+bugzilla@gmail.com

Constructor templates are never considered to be copy constructors by the compiler:

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

void main()
{
    S original;
    S copy = original; // no assert
}
---

However, this is not documented in the language spec's section on copy constructors:

https://dlang.org/spec/struct.html#struct-copy-constructor

--