• d-bugmail puremagic.com (30/31) Nov 12 2021 https://issues.dlang.org/show_bug.cgi?id=22507

d-bugmail puremagic.com writes:

https://issues.dlang.org/show_bug.cgi?id=22507

          Issue ID: 22507
           Summary: Struct destructors must enjoy special status with
                    regard to  safe/ trusted/ system
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody puremagic.com
          Reporter: andrei erdani.com

From https://forum.dlang.org/post/vjptvzqpaobvadnofzht forum.dlang.org:

In order to create an automatic object of type T in a safe function, T's
destructor must be safe or trusted.

Currently the destructor is embodied by the __dtor member function, i.e. the
attributes on the destructor's declaration are identical to those on the
generated __dtor member function.

Some types need to define a destructor that does unsafe things, mainly
deallocating memory that is carefully confined within the object. 

This creates the following conundrum:

1. If such types make the destructor  trusted, it means safe code is also free
to call __dtor() manually. Subsequent use of such objects is liable to break
safetu.

2. If such types choose to make the destructor  system, it means safe code
cannot create objects of those types at all.

At first blush, there needs to be a way to tell the compiler "destructor is to
be trusted but only when called implicitly".

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