www.digitalmars.com         C & C++   DMDScript  

digitalmars.D.bugs - [Issue 6288] New: std.conv.to removes const/immutable when converting a class

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6288

           Summary: std.conv.to removes const/immutable when converting a
                    class
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Phobos
        AssignedTo: nobody puremagic.com
        ReportedBy: schveiguy yahoo.com


--- Comment #0 from Steven Schveighoffer <schveiguy yahoo.com> 2011-07-11
10:19:14 PDT ---
The code in std.conv.to looks like this for converting to base/derived class:

/**
Object-to-object conversions throw exception when the source is
non-null and the target is null.
 */
T toImpl(T, S)(S value) if (is(S : Object) && is(T : Object))
{
    auto result = cast(T) value;
    if (!result && value)
    {
        throw new ConvException("Cannot convert object of static type "
                ~S.classinfo.name~" and dynamic type "~value.classinfo.name
                ~" to type "~T.classinfo.name);
    }
    return result;
}

This does not take into account that cast can easily remove const or immutable
decorations.

For example:

import std.conv;

class C {}
class D : C {}

void main()
{
    const(C) c = new D;
    D d = to!D(c);
    assert(d !is null);
}

This compiles as of 2.054, and clearly is removing const without requiring a
cast.

Unfortunately, cast() is the mechanism to do dynamic conversions, so the logic
to allow compilation needs to check that const is not being removed or
immutable is not being removed/added.

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
Jul 11 2011
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6288


Kenji Hara <k.hara.pg gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch


--- Comment #1 from Kenji Hara <k.hara.pg gmail.com> 2011-09-20 05:44:35 PDT ---
https://github.com/D-Programming-Language/phobos/pull/271

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
Sep 20 2011
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6288


Steven Schveighoffer <schveiguy yahoo.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


--- Comment #2 from Steven Schveighoffer <schveiguy yahoo.com> 2011-09-22
08:00:36 PDT ---
https://github.com/D-Programming-Language/phobos/commit/8b6ef3b46be8ea50b9aef96b2b2d12c378315189

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
Sep 22 2011
prev sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6288


Kenji Hara <k.hara.pg gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |Jesse.K.Phillips+D gmail.co
                   |                            |m


--- Comment #3 from Kenji Hara <k.hara.pg gmail.com> 2011-10-09 03:47:02 PDT ---
*** Issue 5307 has been marked as a duplicate of this issue. ***

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
Oct 09 2011