[Issue 23681] New: Generated copy constructors failing to generate

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23681

          Issue ID: 23681
           Summary: Generated copy constructors failing to generate
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: minor
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: alphaglosined at gmail.com

Copy constructors are failing to generate and be callable if a field is another
struct that does define a copy constructor.

This is quite frustrating for using reference counted types, resulting in more
boiler plate than required.

DMD32 D Compiler v2.101.0-dirty

```d
void main() {
    Depender a, b;
    b = a;
}

struct Dependency {
    this(ref Dependency other) {
        this.tupleof = other.tupleof;
    }

    ~this() {
    }
}

struct Depender {
    Dependency dependency;
}
```


Error:

buggycopyctr.d(3): Error: generated function
`buggycopyctr.Depender.opAssign(Depender p)` is not callable using argument
types `(Depender)`
buggycopyctr.d(3):        generating a copy constructor for `struct Depender`
failed, therefore instances of it are uncopyable


Removing destructor from Dependency makes it compile.

Adding an opAssign that takes Depender by ref also works:

```d
    void opAssign(ref Depender other) {
        this.tupleof = other.tupleof;
    }
```

I suspect this issue is strongly related to another issue with copy
constructors I'm having:

Error: generating an `inout` copy constructor for `struct
sidero.base.logger.FileTarget` failed, therefore instances of it are uncopyable

However I wasn't able to reproduce that error message, but I did come up with
the above so it might be helpful to hunt it down.

--