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digitalmars.D.bugs - [Issue 3438] New: constructor with defaulted parameters ignored

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=3438

           Summary: constructor with defaulted parameters ignored
           Product: D
           Version: unspecified
          Platform: Other
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: andrei metalanguage.com


--- Comment #0 from Andrei Alexandrescu <andrei metalanguage.com> 2009-10-23
07:44:31 PDT ---
struct foo {
       this(int dummy = 0) { writeln("Default constructor");}
}

void main() {
    foo x = foo(); 
}

does not print anything. The code should either not compile or print something.

I think at some point we'll need to support default constructors that execute
code.

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Oct 23 2009
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=3438


Eldar Insafutdinov <e.insafutdinov gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |e.insafutdinov gmail.com


--- Comment #1 from Eldar Insafutdinov <e.insafutdinov gmail.com> 2009-11-09
13:18:26 PST ---
I would also like to have default struct constructors implemented. So I give a
vote to this one.

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Nov 09 2009
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=3438



--- Comment #2 from Eldar Insafutdinov <e.insafutdinov gmail.com> 2009-11-10
22:39:12 PST ---
To add a point, by default constructor should be invoked if present. There may
be some reasons to keep a way to create an uninitialized struct(yeah, D is a
systems language), but it should be done explicitly. Now we have an opposite
situation, where by default struct is not initialized, and if you want to, you
can define static opCall like in D1(what an ugly hack!) and call it manually.

I have the real word example for that as well. I am porting Qt container
classes to D. They are value types with Copy on Write semantics and atomic
reference counting. They need some initialization (reference increment) when
constructed. So basically if I write something like this:

QList!int a;

It would not be a valid code. So I have to do

auto a = QList!int();

That is annoying, unsafe(I would have write something in the docs: always
initialize with static opCall!) and not consistent with other value types.

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Nov 10 2009
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=3438


Jonathan M Davis <jmdavisProg gmx.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jmdavisProg gmx.com


--- Comment #3 from Jonathan M Davis <jmdavisProg gmx.com> 2012-01-22 16:16:31
PST ---
At this point, I don't think that the situation with default constructors and
structs is going to change. It's a result of requiring init properties for all
types, and is thus a "forced fault" in the language. From discussions on it in
the newsgroup, it seems likely that if we were to create a restricted default
constructor (one which didn't do the things that we can't let it do, because it
woludn't work with init), it would too restrictive to really be of much use
anyway. So, I think that all of that strays from the point of this bug.

Having a default argument for all of the parameters of a struct's constructor
should result in a compilation error. It's illegal. The language doesn't
support it. But rather than giving an error, the compiler currently just
ignores it.

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Jan 22 2012
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=3438


Andrej Mitrovic <andrej.mitrovich gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|wrong-code                  |accepts-invalid, pull
                 CC|                            |andrej.mitrovich gmail.com
           Platform|Other                       |All
            Version|2.000                       |D2
         AssignedTo|nobody puremagic.com        |andrej.mitrovich gmail.com
            Summary|constructor with defaulted  |struct ctor with defaulted
                   |parameters ignored          |parameters should be
                   |                            |rejected
         OS/Version|Linux                       |All


--- Comment #4 from Andrej Mitrovic <andrej.mitrovich gmail.com> 2012-12-21
15:52:48 PST ---
Changed what was basically an enhancement request into an accepts-invalid bug.
If the state of things change we can work on it later (if Walter green-lights
default ctors for structs), but for now all forms of default ctors in structs
must be rejected by the compiler.

https://github.com/D-Programming-Language/dmd/pull/1397

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Dec 21 2012
prev sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=3438



--- Comment #5 from Andrej Mitrovic <andrej.mitrovich gmail.com> 2013-09-17
12:15:54 PDT ---
*** Issue 10952 has been marked as a duplicate of this issue. ***

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Sep 17 2013