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digitalmars.D.bugs - [Issue 6427] New: Templated ctor cannot set immutable member variables

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6427

           Summary: Templated ctor cannot set immutable member variables
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: simendsjo gmail.com


--- Comment #0 from simendsjo <simendsjo gmail.com> 2011-08-02 06:39:49 PDT ---
struct S {
    immutable int v;
    this()(int v) {
        this.v = v;
    }
}

void main() {
    S s = S(1);
}

Error: can only initialize const member v inside constructor
Error: template instance t.S.__ctor!(int) error instantiating

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next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6427


Jonathan M Davis <jmdavisProg gmx.com> changed:

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


--- Comment #1 from Jonathan M Davis <jmdavisProg gmx.com> 2011-08-02 11:06:42
PDT ---
1. This compiles with the current compiler on github.

2. I'm not even 100% sure this is supposed to compile, since the constructor
isn't immutable. That might only be necessary when the whole struct is
immutable though. I don't remember for sure and would have to check in TDPL
(which I don't have on me at the moment).

3. While this should certainly compile correctly based on the language spec (or
not compile depending on the spec). I would serious advise against having const
or immutable variables in a struct, since you can then never assign to them
even if they're not const or immutable. If they're on the heap, it's not as big
a deal, but a struct like S would be useless in arrays (since all of the values
would be stuck as S.init) and every instance of it would be effectively
immutable regardless of whether the object itself was typed as immutable or
not.

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prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6427



--- Comment #2 from Jonathan M Davis <jmdavisProg gmx.com> 2011-08-02 12:45:15
PDT ---
Okay. It looks like immutable constructors only apply to when the struct or
class itself that you're constructing is immutable. So, this should definitely
compile. And it does on the current version of the compiler. So, if it doesn't
compile on 2.054, then this it was fixed since the release. I'd close it, but
we might want it end the changelog, so it's probably better that someone who
actually works on the compiler closes the bug. Regardless, it works with the
latest version of the compiler, so 2.055 shouldn't have this bug.

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prev sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6427


yebblies <yebblies gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |yebblies gmail.com
         Resolution|                            |DUPLICATE


--- Comment #3 from yebblies <yebblies gmail.com> 2011-08-04 00:37:22 EST ---
*** This issue has been marked as a duplicate of issue 6355 ***

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Aug 03 2011