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digitalmars.D.bugs - [Issue 2889] New: Alias this properties don't overload with non-alias this properties.

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=2889

           Summary: Alias this properties don't overload with non-alias this
                    properties.
           Product: D
           Version: 2.029
          Platform: PC
        OS/Version: Windows
            Status: NEW
          Keywords: rejects-valid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla digitalmars.com
        ReportedBy: dsimcha yahoo.com


struct ArrayWrapper {
    uint[] arr;

    alias arr this;

    void length(uint l) {};
}

void main() {
    ArrayWrapper aw;
    auto len = aw.length;
}

Errors:
C:\home\dsimcha\bin\test.d(10): Error: function test.ArrayWrapper.length (uint
l) does not match parameter types ()
C:\home\dsimcha\bin\test.d(10): Error: expected 1 function arguments, not 0
C:\home\dsimcha\bin\test.d(10): Error: variable test.main.len voids have no
value
C:\home\dsimcha\bin\test.d(10): Error: expression aw.length() is void and has
no value

If I comment out the length property in the ArrayWrapper struct, length gets
forwarded properly to arr and the code compiles.


-- 
Apr 24 2009
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=2889


Trass3r <mrmocool gmx.de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mrmocool gmx.de
           Platform|x86                         |All
         OS/Version|Windows                     |All


--- Comment #1 from Trass3r <mrmocool gmx.de> 2011-08-14 15:01:37 PDT ---
This is also critical for proper simulation of struct inheritance.

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Aug 14 2011
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=2889


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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |k.hara.pg gmail.com


--- Comment #2 from Kenji Hara <k.hara.pg gmail.com> 2011-08-14 15:30:58 PDT ---
I think this is a language design, not a bug.

In normal class inheritance, derived class method doesn't overload with base
class methods that have same names.

class Array  // the synonym of uint[]
{
    size_t length(){ return 0; }
    void length(size_t n){  }
    // built-in length property (getter and setter)
}
class ArrayWrapper : Array
{
    void length(uint l) {}
    // length overrides Array.length, not overloads
}

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Aug 14 2011
prev sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=2889


Trass3r <mrmocool gmx.de> changed:

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


--- Comment #3 from Trass3r <mrmocool gmx.de> 2011-11-03 04:04:51 PDT ---
Yeah, you're right.
See http://www.digitalmars.com/d/2.0/hijack.html for the rationale.
Overloading is done explicitly with alias just like you use using in C++ for
this purpose.

Unfortunately you can't alias arr.length length; in this particular case
though:
Error: alias test.ArrayWrapper.length cannot alias an expression arr.length

The only option is to use a small function that wraps arr.length I guess.

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Nov 03 2011