Bug 21692 – Non-mutable extern(D) scope class instances cannot be created.

stackConstD and stackImutD should be allowed in the program below, just like the other combinations. Alternatively, if there is some good reason for this restriction, a better error message is needed, because construction is not modification. extern(C++) class C { } extern(D) class D { } void main() { scope stackConstC = new const(C)(); scope stackConstD = new const(D)(); // Error: cannot modify const expression stackConstD auto gcConstD = new const(D)(); scope stackImutC = new immutable(C)(); scope stackImutD = new immutable(D)(); // Error: cannot modify immutable expression stackImutD auto gcImutD = new immutable(D)(); }

This seems caused by `scope` allocations for (D) classes getting an implicit `delete stackConstD`, while C++ classes don't. Which is probably a bug in its own right. The `delete` expression is deprecated; it resets the pointer to null, that's why it cannot be const. An updated lowering could use `destroy()` instead (it's only about calling the dtor/finalizer AFAICT), for C++ classes too, which should make it work with const as well (without dtor or with a const dtor).

(In reply to kinke from comment #1) > This seems caused by `scope` allocations for (D) classes getting an implicit > `delete stackConstD`, while C++ classes don't. Which is probably a bug in > its own right. Good catch! I filed a separate bug for that: https://issues.dlang.org/show_bug.cgi?id=21693 > The `delete` expression is deprecated; it resets the pointer to null, that's > why it cannot be const. An updated lowering could use `destroy()` instead > (it's only about calling the dtor/finalizer AFAICT), for C++ classes too, > which should make it work with const as well (without dtor or with a const > dtor). Yes, that is how it should work.

*** This issue has been marked as a duplicate of issue 19272 ***