[Issue 5363] const + alias this = wrong code

Jul 22, 2014

Marc Schütz

Mar 24, 2016

Sep 18, 2018

Oct 06, 2018

Oct 06, 2018

Oct 08, 2018

Oct 09, 2018

Oct 19, 2018

Dec 17, 2022

5 days ago

dlangBugzillaToGithub

3 days ago

Vladimir Panteleev

https://issues.dlang.org/show_bug.cgi?id=5363 Marc Schütz <schuetzm@gmx.net> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |schuetzm@gmx.net --- Comment #6 from Marc Schütz <schuetzm@gmx.net> --- Just tested with latest DMD git. Jens Mueller's example passes now, but the other ones still fail. --

https://issues.dlang.org/show_bug.cgi?id=5363 taylorh140@gmail.com changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |taylorh140@gmail.com --- Comment #7 from taylorh140@gmail.com --- Still fails on DMD 2.070.2 ( 2.070.2 ) http://dpaste.dzfl.pl/1da91ec34a86 --

https://issues.dlang.org/show_bug.cgi?id=5363 RazvanN <razvan.nitu1305@gmail.com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |nilsbossung@googlemail.com --- Comment #8 from RazvanN <razvan.nitu1305@gmail.com> --- *** Issue 9354 has been marked as a duplicate of this issue. *** --

https://issues.dlang.org/show_bug.cgi?id=5363 Walter Bright <bugzilla@digitalmars.com> changed: What |Removed |Added ---------------------------------------------------------------------------- See Also| |https://issues.dlang.org/sh | |ow_bug.cgi?id=6777 --

October 06, 2018

[Issue 5363] const + alias this = wrong code

Posted by Walter Bright

Permalink

Walter Bright

Permalink

https://issues.dlang.org/show_bug.cgi?id=5363

--- Comment #9 from Walter Bright <bugzilla@digitalmars.com> ---
I simplified it a bit more, so it happens at compile time:

  struct S {
    int dummy;
    alias dummy this;
  }
  int foo(int){ return 1; }
  int foo(const(S)){ return 2; }

  void test() {
    static assert(foo(cast(const)S.init) == 2); // pass
    static assert(foo(S.init) == 2); // fail
  }

Here's the trouble. With alias this, the conversion of S to int is considered an 'exact' match, while the conversion of S to const is considered a 'constant' match, which is not as good as 'exact'. Hence, the 'exact' is selected and foo(int) is called.

The levels of conversion are:

    nomatch
    convert
    constant
    exact

We could change an alias this conversion to a 'convert' match, but it is unknown how much breakage this will cause. It seems to be a rather drastic change.

The compiler source code is the TypeStruct.implicitConvTo() function in
mtype.d.

--

https://issues.dlang.org/show_bug.cgi?id=5363 RazvanN <razvan.nitu1305@gmail.com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |razvan.nitu1305@gmail.com --- Comment #10 from RazvanN <razvan.nitu1305@gmail.com> --- PR : https://github.com/dlang/dmd/pull/8810 --

https://issues.dlang.org/show_bug.cgi?id=5363 calex <calex+bugzilla-mail@aristoweb.net> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |calex+bugzilla-mail@aristow | |eb.net --

https://issues.dlang.org/show_bug.cgi?id=5363 Iain Buclaw <ibuclaw@gdcproject.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Priority|P2 |P1 --

https://issues.dlang.org/show_bug.cgi?id=5363 --- Comment #11 from dlangBugzillaToGithub <robert.schadek@posteo.de> --- THIS ISSUE HAS BEEN MOVED TO GITHUB https://github.com/dlang/dmd/issues/18323 DO NOT COMMENT HERE ANYMORE, NOBODY WILL SEE IT, THIS ISSUE HAS BEEN MOVED TO GITHUB --

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