digitalmars.D.bugs - [Issue 3282] New: The overload and override issue of const/immutable member functions
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http://d.puremagic.com/issues/show_bug.cgi?id=3282
Summary: The overload and override issue of const/immutable
member functions
Product: D
Version: 2.031
Platform: Other
OS/Version: Windows
Status: NEW
Severity: normal
Priority: P2
Component: DMD
AssignedTo: nobody puremagic.com
ReportedBy: rayerd.wiz gmail.com
import std.stdio;
class Base
{
string f()
{
return "Base.f()";
}
}
class Derived : Base
{
string f()
{
return "Derived.f()";
}
string f() const // or immutable
{
return "Derived.f() const";
}
}
void main()
{
auto x = new Base;
writeln(x.f());
auto y = new Derived;
writeln(y.f());
auto z = new const(Derived); // or immutable
writeln(z.f()); //object.Error: Access Violation
}
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Sep 03 2009
d-bugmail puremagic.com http://d.puremagic.com/issues/show_bug.cgi?id=3282 PDT --- This problem occurs when "const" is "shared". -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Oct 19 2009
http://d.puremagic.com/issues/show_bug.cgi?id=3282
Rainer Schuetze <r.sagitario gmx.de> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |r.sagitario gmx.de
PST ---
This kind of works now with changeset 344. But both "f()" and "f() const"
overload "f()" in the base class, and the last one wins. I think dmd should
either issue an error or add another entry to the vtbl for the non-exact but
covariant match.
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Jan 22 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3282
PST ---
This problem's characteristics changed at dmd2.040.
import std.stdio;
class Base
{
string f()
{
return "Base.f()";
}
}
class Derived : Base
{
string f()
{
return "Derived.f()";
}
string f() immutable
{
return "Derived.f() immutable";
}
string f() shared
{
return "Derived.f() shared";
}
}
void main()
{
auto x = new Base;
writeln(x.f());
auto y = new Derived;
writeln(y.f());
auto z = new immutable(Derived);
//main.d(15): Error: function main.Derived.f of type immutable string()
overrides but is not covariant with main.Base.f of type string()
writeln(z.f());
auto w = new shared(Derived);
//main.d(19): Error: function main.Derived.f of type shared string()
overrides but is not covariant with main.Base.f of type string()
writeln(w.f());
}
Are both errors correctly?
I expected that z.f() calls "Derived.f() immutable" and w.f() calls
"Derived.f() shared".
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Jan 30 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3282
Walter Bright <bugzilla digitalmars.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
CC| |bugzilla digitalmars.com
Resolution| |FIXED
01:28:50 PST ---
I believe the errors are correct.
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Jan 23 2012
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Walter Bright <bugzilla digitalmars.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|FIXED |WORKSFORME
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Jan 23 2012
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timon.gehr gmx.ch changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |REOPENED
CC| |timon.gehr gmx.ch
Resolution|WORKSFORME |
I think it is a bug. The derived class introduces two additional overloads. The
compiler claims that all three overloads override the same function.
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Jan 23 2012
http://d.puremagic.com/issues/show_bug.cgi?id=3282
Walter Bright <bugzilla digitalmars.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|REOPENED |RESOLVED
Resolution| |INVALID
15:47:44 PST ---
I think it is a bug. The derived class introduces two additional overloads. The
compiler claims that all three overloads override the same function.
The error messages are deliberate.
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Jan 23 2012
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timon.gehr gmx.ch changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |REOPENED
Resolution|INVALID |
If so, why is this code accepted?
class A{
void f(int){}
}
class B: A{
override void f(int){}
void f(immutable int){}
void f(shared int){}
}
What is the point of deliberately treating the hidden this pointer special
regarding overloading?
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Jan 23 2012
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Furthermore, this works, of course:
class B{
void f(int){}
void f(int)immutable{}
void f(int)shared{}
}
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Jan 23 2012
http://d.puremagic.com/issues/show_bug.cgi?id=3282
Walter Bright <bugzilla digitalmars.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|REOPENED |RESOLVED
Resolution| |INVALID
19:36:45 PST ---
The return types are the issue. You cannot, for example, override a function
that returns a mutable array with one that returns an immutable one. It would
be a giant hole in the type system.
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Jan 23 2012
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timon.gehr gmx.ch changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |REOPENED
Resolution|INVALID |
The signature of the overriding function is identical to the overridden one in
all cases discussed here.
class A{
void f(){} // note: return type void
}
class B: A{
override void f(){} // overrides base f
void f()immutable{} // new overload
void f()shared{} // new overload
}
It is impossible to break the type system (even if the return types would be
different): the new overloads are not even reachable through a base class
reference. The bug is that the compiler does not take into account the storage
class of the hidden this pointer while deciding what overrides what.
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Jan 24 2012
http://d.puremagic.com/issues/show_bug.cgi?id=3282
Kenji Hara <k.hara.pg gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |pull
---
https://github.com/D-Programming-Language/dmd/pull/779
I also think this never breaks type systems, and additional overloads is
useful.
e.g. http://d.puremagic.com/issues/show_bug.cgi?id=7534#c6
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Mar 03 2012
http://d.puremagic.com/issues/show_bug.cgi?id=3282
Kenji Hara <k.hara.pg gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|REOPENED |RESOLVED
Resolution| |FIXED
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Jun 06 2012