[Issue 15648] New: Destructor constness doesn't take member destructor attributes into account

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=15648

          Issue ID: 15648
           Summary: Destructor constness doesn't take member destructor
                    attributes into account
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Keywords: rejects-valid
          Severity: major
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: Marco.Leise at gmx.de

I'm unable to implement an @nogc hash table that has immutable keys that have
dtors and contain members with dtors. Here is the reduced version of such a
structure:

    struct HashTable
    {
        immutable(Key)* keys;

        ~this()
        {
            destroy( keys[0] );
        }
    }

    struct Key
    {
        KeyData data;
        ~this() const {}
    }

    struct KeyData
    {
        ~this() const {}
    }

The compiler will complain:
  Error: mutable method main.Key.~this is not callable using a immutable object
  Error: template instance object._destructRecurse!(immutable(Key)) error
instantiating

This seems to come from calling an aggregated non-const destructor and I don't
know of a feasible workaround. The ones I know of are:
 1) remove immutability from keys and const from dtors
 2) merge KeyData's dtor into that of Key (but Key is a generic templated
wrapper struct)

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