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digitalmars.D.bugs - [Issue 8118] New: Impossible to initialize a member struct without default constructor or assigment

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8118

           Summary: Impossible to initialize a member struct without
                    default constructor or assigment
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: critical
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: wfunction hotmail.com



struct S
{
     disable this();
    this(int) { }
     disable void opAssign(typeof(this));
}

class Test
{
    S s = void;      // I *EXPLICITLY* told it not to be initialized, but...
    this() { s = S(to!int("1")); }
}

void main() { new Test(); }


Error: function S.opAssign is not callable because it is annotated with
 disable
Error: default construction is disabled for type Test



Structs without default constructors are pretty much impossible to use.

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May 18 2012
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8118




Possibly related:
http://d.puremagic.com/issues/show_bug.cgi?id=8117

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May 18 2012
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8118


Dmitry Olshansky <dmitry.olsh gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dmitry.olsh gmail.com



03:44:28 PDT ---


 struct S
 {
      disable this();
     this(int) { }
      disable void opAssign(typeof(this));
 }
 
 class Test
 {
     S s = void;      // I *EXPLICITLY* told it not to be initialized, but...
     this() { s = S(to!int("1")); }
 }
 
 void main() { new Test(); }
 
 
 Error: function S.opAssign is not callable because it is annotated with
  disable
 Error: default construction is disabled for type Test
 
 
 
 Structs without default constructors are pretty much impossible to use.


No bug here you just diabled too much. Undisable opAssign.

It's opAssign that gets called whne a = ... is seen:
this() { s = S(to!int("1")); }
If opAssign is trivial it replaced with bitblit. (that is disable comes first!)

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May 19 2012
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8118






 No bug here you just diabled too much. Undisable opAssign.
 
 It's opAssign that gets called whne a = ... is seen:
 this() { s = S(to!int("1")); }
 If opAssign is trivial it replaced with bitblit. (that is disable comes first!)


Uh, no, it's a bug IMO.


I never asked for an assignment. I want to CONSTRUCT the object manually.

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prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8118








 No bug here you just diabled too much. Undisable opAssign.
 
 It's opAssign that gets called whne a = ... is seen:
 this() { s = S(to!int("1")); }
 If opAssign is trivial it replaced with bitblit. (that is disable comes first!)


 
 Uh, no, it's a bug IMO.
 
 
 I never asked for an assignment. I want to CONSTRUCT the object manually.


For example, pretend this is the Scoped struct. I *obviously* wouldn't want to
assign anything, but I'd want to construct the object.

The fact that it's **impossible** to call the constructor directly without an
assignment getting in the way (as far as I see) is a bug.

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May 19 2012
prev sibling parent d-bugmail puremagic.com writes:
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Marco Leise <Marco.Leise gmx.de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |Marco.Leise gmx.de





 The fact that it's **impossible** to call the constructor directly without an
 assignment getting in the way (as far as I see) is a bug.


I agree with you. I have a struct that is not supposed to be copied. Now I
cannot use it as a field in any other struct/class.

In some cases a work-around may be to allow assignments, but check that the
receiver is S.init.

Also I tried "= void" first. So it may be the most intuitive to use for the bug
fix.

I haven't checked, but it could allow code like this if not currently possible:

S s = void;
if (xyz) {
  s = S(3);
} else {
  s = S(7);
}

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Feb 15 2013