digitalmars.D.bugs - [Issue 3731] New: Immutable class may be changed when inherits from mutable parent
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http://d.puremagic.com/issues/show_bug.cgi?id=3731
Summary: Immutable class may be changed when inherits from
mutable parent
Product: D
Version: 2.039
Platform: x86
OS/Version: Windows
Status: NEW
Severity: normal
Priority: P2
Component: DMD
AssignedTo: nobody puremagic.com
ReportedBy: tomeksowi gmail.com
PST ---
This merrily compiles:
class Zmienna {
int a;
this(int a) {
this.a = a;
}
}
immutable class Stala : Zmienna {
this(int a) {
super(a);
}
}
void main() {
auto st = new Stala(5);
Zmienna zm = st;
zm.a = 666;
// st.a = 666; // fails
assert (st.a == 666);
}
The above shows that an immutable class shouldn't be allowed to derive from
mutable classes. Unfortunately it won't work because Object is not (and can't
be) immutable. Not sure how to bite this one, perhaps make an opt out that says
mutable parents with no fields are OK? Or an exception only for Object?
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Jan 20 2010
d-bugmail puremagic.com
http://d.puremagic.com/issues/show_bug.cgi?id=3731
Steven Schveighoffer <schveiguy yahoo.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |schveiguy yahoo.com
05:43:28 PST ---
The solution would be to make it illegal to have a mutable class reference to
the base class.
In your example, this line should be an error:
Zmienna zm = st; // error, must use immutable(Zmienna) or const(Zmienna)
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Jan 21 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3731 PST ---The solution would be to make it illegal to have a mutable class reference to the base class. In your example, this line should be an error: Zmienna zm = st; // error, must use immutable(Zmienna) or const(Zmienna)Thanks, that makes sense. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Jan 21 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3731
yebblies <yebblies gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |accepts-invalid, patch
CC| |yebblies gmail.com
Summary|Immutable class may be |Can implicitly cast an
|changed when inherits from |immutable reference to a
|mutable parent |derived class
https://github.com/D-Programming-Language/dmd/pull/125
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Jun 13 2011
http://d.puremagic.com/issues/show_bug.cgi?id=3731 I think issue 3731 is same as issue 5080, and the yebblies patch is a bit better than mine. See also Don and Steven's comments in 5080. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Sep 16 2011
http://d.puremagic.com/issues/show_bug.cgi?id=3731
yebblies <yebblies gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |rayerd.wiz gmail.com
*** Issue 6863 has been marked as a duplicate of this issue. ***
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Dec 12 2011
http://d.puremagic.com/issues/show_bug.cgi?id=3731 Commits pushed to master at https://github.com/D-Programming-Language/phobos https://github.com/D-Programming-Language/phobos/commit/7bed81961aefc5327b57be0862514b78d84355db The fix for issue 3731 shows a couple of places in phobos that rely on this bug. std.xml is going away, so work around the issue for now (all problems are caused by opEquals and opCmp not being const correct) and in std.datetime, AA values must be rebindable. https://github.com/D-Programming-Language/phobos/commit/472c2a984391a97fd6fda5b77d082e184b828c87 Remove implicit casts to mutable super class -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Jan 27 2012
http://d.puremagic.com/issues/show_bug.cgi?id=3731
yebblies <yebblies gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |k.hara.pg gmail.com
*** Issue 5080 has been marked as a duplicate of this issue. ***
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Jan 30 2012
http://d.puremagic.com/issues/show_bug.cgi?id=3731
dawg dawgfoto.de changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |dawg dawgfoto.de
*** Issue 7636 has been marked as a duplicate of this issue. ***
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Mar 04 2012
http://d.puremagic.com/issues/show_bug.cgi?id=3731
Stewart Gordon <smjg iname.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|Can implicitly cast an |Derived class implicitly
|immutable reference to a |convertible to base class
|derived class |with arbitrary change of
| |constancy
The solution would be to make it illegal to have a mutable class reference to
the base class.
No, because a Zmienna is perfectly allowed to be mutable. It's Stala that
isn't.
In your example, this line should be an error:
Zmienna zm = st; // error, must use immutable(Zmienna) or const(Zmienna)
Correct, since because Stala is immutable, any object reference of type Stala
is actually of type immutable(Stala).
The bug is that constancy is ignored when converting from a derived class to a
base class, as this code shows (DMD 2.058, Win32):
----------
class Base { int x; }
class Derived : Base { int y; }
void main() {
Derived md;
const(Derived) cd;
immutable(Derived) id;
Base mb_md = md;
const(Base) cb_md = md;
immutable(Base) ib_md = md; // accepts-invalid
Base mb_cd = cd; // accepts-invalid
const(Base) cb_cd = cd;
immutable(Base) ib_cd = cd; // accepts-invalid
Base mb_id = id; // accepts-invalid
const(Base) cb_id = id;
immutable(Base) ib_id = id;
}
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Mar 25 2012
http://d.puremagic.com/issues/show_bug.cgi?id=3731 03:11:50 PDT ---I think you misunderstand. I don't mean because Stala exists, Zmienna should be prevented from being mutable, even for cases where Stala is not involved. I mean, it should be illegal to have a mutable Stala reference point at a Zmienna. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------The solution would be to make it illegal to have a mutable class reference to the base class.No, because a Zmienna is perfectly allowed to be mutable. It's Stala that isn't.
Mar 26 2012
http://d.puremagic.com/issues/show_bug.cgi?id=3731I think you misunderstand. I don't mean because Stala exists, Zmienna should be prevented from being mutable, even for cases where Stala is not involved. I mean, it should be illegal to have a mutable Stala reference point at a Zmienna.I haven't misunderstood. There's no such thing as a mutable Stala reference. Because Stala is an immutable class, any reference to a Stala is automatically immutable. See for yourself: ----- void main() { Stala st = new Stala(5); pragma(msg, typeof(st)); // immutable(Stala) st = new Stala(4); // errors, because st is immutable Zmienna zm = st; // accepts-invalid } ----- The bug is that DMD allows the implicit conversion of immutable(Stala) to Zmienna. It's just mb_id in my last example. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Mar 26 2012
http://d.puremagic.com/issues/show_bug.cgi?id=3731
Steven Schveighoffer <schveiguy yahoo.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |doob me.com
05:30:03 PDT ---
*** Issue 7920 has been marked as a duplicate of this issue. ***
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Apr 16 2012
http://d.puremagic.com/issues/show_bug.cgi?id=3731
Steven Schveighoffer <schveiguy yahoo.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jmdavisProg gmx.com
04:52:11 PDT ---
*** Issue 7939 has been marked as a duplicate of this issue. ***
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Apr 19 2012
http://d.puremagic.com/issues/show_bug.cgi?id=3731 Commits pushed to master at https://github.com/D-Programming-Language/dmd https://github.com/D-Programming-Language/dmd/commit/65f12c80d383bd655aec1f53510fd4ae201b3b79 Fix Issue 3731 - Can implicitly cast an immutable reference to a derived class to a mutable reference to a base class. Ensure the modifier conversion is valid before allowing an implicit conversion to a base class. https://github.com/D-Programming-Language/dmd/commit/bf982fac38051e34d365d972ff847983cb73848a Issue 3731 - Can implicitly cast an immutable reference to a derived class -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Jul 18 2012
http://d.puremagic.com/issues/show_bug.cgi?id=3731
Don <clugdbug yahoo.com.au> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
CC| |clugdbug yahoo.com.au
Resolution| |FIXED
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Jul 18 2012