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digitalmars.D.bugs - [Issue 8161] New: -property should give an error for invalid property functions

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8161

           Summary: -property should give an error for invalid property
                    functions
           Product: D
           Version: unspecified
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: jmdavisProg gmx.com


--- Comment #0 from Jonathan M Davis <jmdavisProg gmx.com> 2012-05-29 22:36:00
PDT ---
This code compiles with -property:

struct S
{
     property void prop()
    {
    }
}

void main()
{
}


It makes no sense that it would. prop returns nothing, so it can't be used as a
getter, and it takes nothing, so it can't be used as a setter. Neither

S s;
auto a = s.prop;

nor

s.prop = a;

would compile, so there's no point in letting prop compile with  property.
Another example would be a function like

struct S
{
     property void prop(int a, int b)
    {
    }
}

It can't possibly be used as a property function either. I'd argue that any
such function should be considered an error as long as it's marked as  property
and the -property flag is used.

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--- Comment #1 from Kenji Hara <k.hara.pg gmail.com> 2012-05-29 23:24:13 PDT ---
(In reply to comment #0)

 This code compiles with -property:
 
 struct S
 {
      property void prop()
     {
     }
 }
 
 void main()
 {
 }
 
 
 It makes no sense that it would.


I can agree.


 Another example would be a function like
 
 struct S
 {
      property void prop(int a, int b)
     {
     }
 }
 
 It can't possibly be used as a property function either. I'd argue that any
 such function should be considered an error as long as it's marked as  property
 and the -property flag is used.


A  property function has two parameters is now allowed for UFCS property
setter.

 property foo(T)(T obj, int val) { ... }
void main() {
   S s;
   s.foo = 1;  // translated to .foo(s, 1), it's valid.
}

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--- Comment #2 from Jonathan M Davis <jmdavisProg gmx.com> 2012-05-29 23:30:30
PDT ---

 A  property function has two parameters is now allowed for UFCS property
 setter.



  property foo(T)(T obj, int val) { ... }
 void main() {
    S s;
    s.foo = 1;  // translated to .foo(s, 1), it's valid.
 }


Yeah, because that's a free function. It's valid to use it as a property, so it
makes sense for it to compile with  property. The example that I gave with two
arguments was a member function, which already has the invisible this
parameter, so it won't work as a property.

The point is that any function which cannot be legally used as a property
function should not compile when marked with  property and compiled with
-property.

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--- Comment #3 from Kenji Hara <k.hara.pg gmail.com> 2012-05-29 23:38:53 PDT ---
(In reply to comment #2)

 A  property function has two parameters is now allowed for UFCS property
 setter.


 

  property foo(T)(T obj, int val) { ... }
 void main() {
    S s;
    s.foo = 1;  // translated to .foo(s, 1), it's valid.
 }


 
 Yeah, because that's a free function. It's valid to use it as a property, so it
 makes sense for it to compile with  property. The example that I gave with two
 arguments was a member function, which already has the invisible this
 parameter, so it won't work as a property.
 
 The point is that any function which cannot be legally used as a property
 function should not compile when marked with  property and compiled with
 -property.


OK. I got an understanding.

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