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January 27, 2013
[Issue 9410] New: Wrong selection for function overload
http://d.puremagic.com/issues/show_bug.cgi?id=9410

          Summary: Wrong selection for function overload
          Product: D
          Version: D2
         Platform: All
       OS/Version: All
           Status: NEW
         Severity: major
         Priority: P2
        Component: DMD
       AssignedTo: nobody@puremagic.com
       ReportedBy: rswhite4@googlemail.com


--- Comment #0 from rswhite4@googlemail.com 2013-01-27 05:11:22 PST ---
This code:

[code]
import std.stdio;

struct Vec2(T) {
public:
   T x;
   T y;

   this(T x, T y) {

   }
}

alias Vec2f = Vec2!(float);

class Foo {
public:
   static Foo make(float i, ref const Vec2f a) {
       return new Foo();
   }

   static Foo make(float i, const Vec2f a) {
       return Foo.make(i, a);
   }
}

void main() {
   Foo f = Foo.make(42, Vec2f(4, 2));
}
[/code]

prints:

Error: (Vec2!(float) __ctmp1173 = _D4c42511__T4Vec2TfZ4Vec26__initZ;
, __ctmp1173).this(4F, 2F) is not an lvalue

But IMO it should compile.
Also this code:

[code]
import std.stdio;

struct Rect(T) {
private:
   T x, y, w, h;

public:
   this(T x, T y, T w, T h) {

   }
}

alias FloatRect = Rect!(float);

class A { }
class B : A { }

class C {
public:
   this(A a, ref const FloatRect sr) {

   }

   this(A a, const FloatRect sr) {
       this(a, sr);
   }
}

void main() {
   // new C(new A(), FloatRect(0, 1, 2, 3)); // works
   new C(new B(), FloatRect(0, 1, 2, 3));
}
[/code]

seems to have the same problem. It prints:

Error: (Rect!(float) __ctmp1173 = _D4c84111__T4RectTfZ4Rect6__initZ;
, __ctmp1173).this(0F, 1F, 2F, 3F) is not an lvalue

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January 27, 2013
[Issue 9410] Wrong selection for function overload
http://d.puremagic.com/issues/show_bug.cgi?id=9410


Maxim Fomin <maxim@maxim-fomin.ru> changed:

          What    |Removed                     |Added
----------------------------------------------------------------------------
          Keywords|                            |diagnostic, rejects-valid
                CC|                            |maxim@maxim-fomin.ru


--- Comment #1 from Maxim Fomin <maxim@maxim-fomin.ru> 2013-01-27 05:35:11 PST ---
Reduced (Error: S() is not an lvalue)

import std.stdio;

struct S {}

void foo(float f, ref const S s)
{
   writeln("const");
}

void foo(float f, const S s)
{
   writeln("ref const");
}

void main()
{
   foo(1, S()); // 1f fixes code and calls ref const version
}


If overloaded functions have several parameters, one of which is
const-qualified used-defined type and functions differer only in refness of
that parameter, supplying implicitly convertible arguments (like int to float)
to other parameters breaks compiler. 

Passing 1f results in calling ref const version which contradicts to recent
revertion of passing struct literals by ref (however that was without const).
It is unclear what should happen in presence of const.

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January 27, 2013
[Issue 9410] Wrong selection for function overload
http://d.puremagic.com/issues/show_bug.cgi?id=9410



--- Comment #2 from rswhite4@googlemail.com 2013-01-27 09:31:13 PST ---
This also fails.

Error: A() is not an lvalue

[code]
import std.stdio;

struct A { }

void foo(const A a, float r) {

}

void foo(ref A a, float r) {

}

void main()
{
   foo(A(), 12);
}
[/code]

_That_ is strange.

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January 28, 2013
[Issue 9410] Wrong selection for function overload
http://d.puremagic.com/issues/show_bug.cgi?id=9410



--- Comment #3 from rswhite4@googlemail.com 2013-01-28 02:40:36 PST ---
(In reply to comment #1)
> Reduced (Error: S() is not an lvalue)
> 
> import std.stdio;
> 
> struct S {}
> 
> void foo(float f, ref const S s)
> {
>     writeln("const");
> }
> 
> void foo(float f, const S s)
> {
>     writeln("ref const");
> }
> 
> void main()
> {
>     foo(1, S()); // 1f fixes code and calls ref const version
> }
> 
> 
> If overloaded functions have several parameters, one of which is
> const-qualified used-defined type and functions differer only in refness of
> that parameter, supplying implicitly convertible arguments (like int to float)
> to other parameters breaks compiler. 
> 
> Passing 1f results in calling ref const version which contradicts to recent
> revertion of passing struct literals by ref (however that was without const).
> It is unclear what should happen in presence of const.

The problem isn't the presence of const.
This code fails, also:

[code]
import std.stdio;

struct S {}

void foo(float f, ref S s)
{
  writeln("ref");
}

void foo(float f, S s)
{
  writeln("without ref");
}

void main()
{
   S s;
      foo(1, s); // works fine. Print: ref
   //foo(1, S()); // Fails with: Error: S() is not an lvalue
}
[/code]

IMO the problem is, that the compiler cannot convert 1 (int) to 1f (float).
He found the correct match: foo(float f, S s).
But the compiler could not convert int to float, so he tried another "match",
which is wrong because S() is not an lvalue.
That recognize the compiler and print an error. But IMO he should convert int
to float by his first match, which was the only correct match.
I believe the problem comes from the change that structs aren't handled as
lvalues anymore. Something of the old behaviour interfere with the new
behaviour.

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January 28, 2013
[Issue 9410] [Regression 2.061] Wrong selection for function overload
http://d.puremagic.com/issues/show_bug.cgi?id=9410


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

          What    |Removed                     |Added
----------------------------------------------------------------------------
          Keywords|                            |pull
           Summary|Wrong selection for         |[Regression 2.061] Wrong
                  |function overload           |selection for function
                  |                            |overload
          Severity|major                       |regression


--- Comment #4 from Kenji Hara <k.hara.pg@gmail.com> 2013-01-28 04:27:54 PST ---
This is a regression from 2.061.

https://github.com/D-Programming-Language/dmd/pull/1571

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January 28, 2013
[Issue 9410] [Regression 2.061] Wrong selection for function overload
http://d.puremagic.com/issues/show_bug.cgi?id=9410



--- Comment #5 from github-bugzilla@puremagic.com 2013-01-28 13:27:17 PST ---
Commits pushed to master at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/ee8cf8344602a113185a7f489f2b3b1988510615
fix Issue 9410 - Wrong selection for function overload

https://github.com/D-Programming-Language/dmd/commit/e7d4abc28f77ba7a2771003fe13f56efa94e0f3f
Merge pull request #1571 from 9rnsr/fix9410

[Regression 2.061] Issue 9410 - Wrong selection for function overload

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January 28, 2013
[Issue 9410] [Regression 2.061] Wrong selection for function overload
http://d.puremagic.com/issues/show_bug.cgi?id=9410


Walter Bright <bugzilla@digitalmars.com> changed:

          What    |Removed                     |Added
----------------------------------------------------------------------------
            Status|NEW                         |RESOLVED
                CC|                            |bugzilla@digitalmars.com
        Resolution|                            |FIXED


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