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digitalmars.D.bugs - [Issue 9410] New: Wrong selection for function overload

reply d-bugmail puremagic.com writes:
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



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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next sibling parent d-bugmail puremagic.com writes:
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



---
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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prev sibling next sibling parent d-bugmail puremagic.com writes:
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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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prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=9410






 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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Jan 28 2013
prev sibling next sibling parent d-bugmail puremagic.com writes:
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



This is a regression from 2.061.

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

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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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


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

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prev sibling parent d-bugmail puremagic.com writes:
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Walter Bright <bugzilla digitalmars.com> changed:

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


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