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digitalmars.D - This doesn't make sense regarding alias this a static function

reply 12345swordy <alexanderheistermann gmail.com> writes:
```struct TIntStatic
{
     static int mX;

     static  property int x() { return mX; }
     static  property void x(int v) { mX = v; }

     alias x this;
}
```

It doesn't like the following code
```

alias t = TIntStatic;
t(5);
```
Yet is perfectly fine with this
```
alias t = TIntStatic;
t = 5;
```
What is with the inconsistency? If you allow t = 5 then surely 
you must allow t(5) as part of alias this a function.
-Alex
May 16 2021
parent reply Steven Schveighoffer <schveiguy yahoo.com> writes:
On Sunday, 16 May 2021 at 15:45:48 UTC, 12345swordy wrote:

 ```struct TIntStatic
 {
     static int mX;

     static  property int x() { return mX; }
     static  property void x(int v) { mX = v; }

     alias x this;
 }
 ```

 It doesn't like the following code
 ```

 alias t = TIntStatic;
 t(5);
 ```
 Yet is perfectly fine with this
 ```
 alias t = TIntStatic;
 t = 5;
 ```
 What is with the inconsistency? If you allow t = 5 then surely 
 you must allow t(5) as part of alias this a function.


That’s considered a constructor. And there’s no member to accept 
the 5.

-Steve
May 16 2021
parent reply 12345swordy <alexanderheistermann gmail.com> writes:
On Sunday, 16 May 2021 at 16:38:08 UTC, Steven Schveighoffer 
wrote:

 On Sunday, 16 May 2021 at 15:45:48 UTC, 12345swordy wrote:

 ```struct TIntStatic
 {
     static int mX;

     static  property int x() { return mX; }
     static  property void x(int v) { mX = v; }

     alias x this;
 }
 ```

 It doesn't like the following code
 ```

 alias t = TIntStatic;
 t(5);
 ```
 Yet is perfectly fine with this
 ```
 alias t = TIntStatic;
 t = 5;
 ```
 What is with the inconsistency? If you allow t = 5 then surely 
 you must allow t(5) as part of alias this a function.


 That’s considered a constructor. And there’s no member to 
 accept the 5.

 -Steve


You mean that this shouldn't work?
```
alias t = TIntStatic;
t = 5;
```

-Alex
May 16 2021
parent reply Steven Schveighoffer <schveiguy gmail.com> writes:
On 5/16/21 12:48 PM, 12345swordy wrote:

 On Sunday, 16 May 2021 at 16:38:08 UTC, Steven Schveighoffer wrote:

 On Sunday, 16 May 2021 at 15:45:48 UTC, 12345swordy wrote:

 ```struct TIntStatic
 {
     static int mX;

     static  property int x() { return mX; }
     static  property void x(int v) { mX = v; }

     alias x this;
 }
 ```

 It doesn't like the following code
 ```

 alias t = TIntStatic;
 t(5);
 ```
 Yet is perfectly fine with this
 ```
 alias t = TIntStatic;
 t = 5;
 ```
 What is with the inconsistency? If you allow t = 5 then surely you 
 must allow t(5) as part of alias this a function.


 That’s considered a constructor. And there’s no member to accept the 5.


 
 You mean that this shouldn't work?
 ```
 alias t = TIntStatic;
 t = 5;
 ```


Honestly, I'm not sure. `alias this` usually maps to a `this`, i.e. an 
instance, not the type. I'm sure it's some quirk in how the compiler 
treats alias this, but I wouldn't have expected it to work.

But the reason the constructor form doesn't work is straightforward -- 
the constructor t() exists. Therefore, it matches first, not using the 
alias this, and it's just a matter of parameter count mismatch that 
fails (this is well-trodden ground).

BTW, is there a reason you are using `alias t` instead of the real type? If:

```d
TIntStatic = 5;
```

doesn't work, but yours does, then that seems like a bug to me.

-Steve
May 16 2021
parent reply 12345swordy <alexanderheistermann gmail.com> writes:
On Sunday, 16 May 2021 at 17:11:23 UTC, Steven Schveighoffer 
wrote:

 On 5/16/21 12:48 PM, 12345swordy wrote:

 On Sunday, 16 May 2021 at 16:38:08 UTC, Steven Schveighoffer 
 wrote:

 On Sunday, 16 May 2021 at 15:45:48 UTC, 12345swordy wrote:

 ```struct TIntStatic
 {
     static int mX;

     static  property int x() { return mX; }
     static  property void x(int v) { mX = v; }

     alias x this;
 }
 ```

 It doesn't like the following code
 ```

 alias t = TIntStatic;
 t(5);
 ```
 Yet is perfectly fine with this
 ```
 alias t = TIntStatic;
 t = 5;
 ```
 What is with the inconsistency? If you allow t = 5 then 
 surely you must allow t(5) as part of alias this a function.


 That’s considered a constructor. And there’s no member to 
 accept the 5.


 
 You mean that this shouldn't work?
 ```
 alias t = TIntStatic;
 t = 5;
 ```


 Honestly, I'm not sure. `alias this` usually maps to a `this`, 
 i.e. an instance, not the type. I'm sure it's some quirk in how 
 the compiler treats alias this, but I wouldn't have expected it 
 to work.

 But the reason the constructor form doesn't work is 
 straightforward -- the constructor t() exists. Therefore, it 
 matches first, not using the alias this, and it's just a matter 
 of parameter count mismatch that fails (this is well-trodden 
 ground).

 BTW, is there a reason you are using `alias t` instead of the 
 real type? If:

 ```d
 TIntStatic = 5;
 ```

 doesn't work, but yours does, then that seems like a bug to me.

 -Steve


It part of the test suit that the user jinshill has created.
```d
TIntStatic = 5
```
Works fine. It is just that I am puzzled by this weird edge case.
May 16 2021
parent Steven Schveighoffer <schveiguy gmail.com> writes:
On 5/16/21 1:19 PM, 12345swordy wrote:

 It part of the test suit that the user jinshill has created.
 ```d
 TIntStatic = 5
 ```
 Works fine. It is just that I am puzzled by this weird edge case.


People can write tests that confirm invalid behavior. I wouldn't take 
the presence of a test as definitive confirmation that the feature 
should exist. Again, though, I'm not sure if it should.

-Steve
May 16 2021