Re: UDAs and no complaints about "need 'this'"

[Maxim Fomin via Digitalmars-d]

On Thursday, 9 April 2015 at 09:53:15 UTC, John Colvin wrote:

struct BigLongStructName
{
int evenLongerMemberName;
}

struct QN{}

unittest
{
BigLongStructName bigLongStructName;

@(bigLongStructName.evenLongerMemberName)
QN quickName;

__traits(getAttributes, quickName)[0]++;
}

Is it just me or is it weird that this works? Once you pull the 
UDA out from being a storage class and attempt to alias it, you 
get the usual "need 'this' for 'evenLongerMemberName' of type 
'int'" error messages on use.


Why are UDAs so special? I don't believe there's any other way 
to achieve this sort of effective renaming.


For me it seems to fit into D type system (which is not 
necessarily is a good idea).


struct S
{
int i;
}

alias S.i si;

void main(){ /*si++;*/}

Behavior of D depends sometimes on it internals, not on 
programmers' expectations. Since D has never been stabilized, the 
boundary between WAT and bugs is partially undefined.

Re: UDAs and no complaints about "need 'this'"

[jkpl via Digitalmars-d]

On Thursday, 9 April 2015 at 09:53:15 UTC, John Colvin wrote:

struct BigLongStructName
{
int evenLongerMemberName;
}

struct QN{}

unittest
{
BigLongStructName bigLongStructName;

@(bigLongStructName.evenLongerMemberName)
QN quickName;

__traits(getAttributes, quickName)[0]++;
}

Is it just me or is it weird that this works? Once you pull the 
UDA out from being a storage class and attempt to alias it, you 
get the usual "need 'this' for 'evenLongerMemberName' of type 
'int'" error messages on use.


Why are UDAs so special? I don't believe there's any other way 
to achieve this sort of effective renaming.


I think it's an error. When the attribute is a struct, it looks 
like the member is processed as a static variable. But the 
equivalent with a class raises an AV:


---
class BigLongStructName
{
int evenLongerMemberName;
}

struct QN{}

unittest
{
import std.stdio;

BigLongStructName bigLongStructName;

@(bigLongStructName.evenLongerMemberName)
QN quickName;

__traits(getAttributes, quickName)[0]++;
}
---

which is a totally expected behaviour.

UDAs and no complaints about "need 'this'"

[John Colvin via Digitalmars-d]

struct BigLongStructName
{
int evenLongerMemberName;
}

struct QN{}

unittest
{
BigLongStructName bigLongStructName;

@(bigLongStructName.evenLongerMemberName)
QN quickName;

__traits(getAttributes, quickName)[0]++;
}

Is it just me or is it weird that this works? Once you pull the 
UDA out from being a storage class and attempt to alias it, you 
get the usual "need 'this' for 'evenLongerMemberName' of type 
'int'" error messages on use.


Why are UDAs so special? I don't believe there's any other way to 
achieve this sort of effective renaming.