Re: PropertyType

[Steven Schveighoffer via Digitalmars-d]

On 5/17/16 1:36 PM, Timon Gehr wrote:

On 17.05.2016 16:24, Steven Schveighoffer wrote:


But of course, if I want to know what type the expression x.foo will
yield, I have to do the above.


typeof((()=>x.foo)())


Well, that is likely a valid solution for implementation of 
PropertyType, but I'd never want to have to type that wherever I wanted 
the property return type :)



(Arguably, function types should not even exist and typeof(x.foo) should
give you what you want.)


Yes, absolutely. I'm not sure if that's fixable at this point, however.

-Steve

Re: PropertyType

[Timon Gehr via Digitalmars-d]

On 17.05.2016 16:24, Steven Schveighoffer wrote:


But of course, if I want to know what type the expression x.foo will
yield, I have to do the above.


typeof((()=>x.foo)())


(Arguably, function types should not even exist and typeof(x.foo) should 
give you what you want.)

Re: PropertyType

[Steven Schveighoffer via Digitalmars-d]

On 5/17/16 10:50 AM, Edwin van Leeuwen wrote:

On Tuesday, 17 May 2016 at 14:24:09 UTC, Steven Schveighoffer wrote:

I have this little helper in my iopipe library:

template PropertyType(alias x)
{
static if(is(typeof(x) == function))
alias PropertyType = typeof(x());
else
alias PropertyType = typeof(x);
}



FYI: In painlesstraits we use a different approach, where we test
whether it is a function (with isSomeFunction) and then test for the
property attribute:

https://github.com/msoucy/painlesstraits/blob/master/source/painlesstraits.d#L173

```
static if (isSomeFunction!(T))
 {
 return (functionAttributes!(T) & FunctionAttribute.property);
 } else
 return false;
```



My code is less concerned as to whether it is a property or not. I just 
want to know the type of the expression :)


-Steve

Re: PropertyType

[Edwin van Leeuwen via Digitalmars-d]

On Tuesday, 17 May 2016 at 14:24:09 UTC, Steven Schveighoffer 
wrote:

I have this little helper in my iopipe library:

template PropertyType(alias x)
{
static if(is(typeof(x) == function))
alias PropertyType = typeof(x());
else
alias PropertyType = typeof(x);
}



FYI: In painlesstraits we use a different approach, where we test 
whether it is a function (with isSomeFunction) and then test for 
the property attribute:


https://github.com/msoucy/painlesstraits/blob/master/source/painlesstraits.d#L173
```
static if (isSomeFunction!(T))
{
return (functionAttributes!(T) & 
FunctionAttribute.property);

} else
return false;
```

PropertyType

[Steven Schveighoffer via Digitalmars-d]

I have this little helper in my iopipe library:

template PropertyType(alias x)
{
static if(is(typeof(x) == function))
alias PropertyType = typeof(x());
else
alias PropertyType = typeof(x);
}

This is because when you have code like this:

x.foo

And you are introspecting some type, you can't tell whether this is a 
property function or a field.


If foo is a field, or a function marked as a @property, then 
typeof(x.foo) will be whatever x.foo returns. But if foo is a straight 
function, then typeof(x.foo) will be a function type.


As we all know, @property is not exactly popular, and having to mark 
functions @property just for introspection purposes (applying the tag 
actually has zero impact otherwise) seems incorrect.


But of course, if I want to know what type the expression x.foo will 
yield, I have to do the above.


Is there a use for this in Phobos? Is it already present somewhere? 
Where should it go if it's not there already?


-Steve