• Nick Sabalausky (15/16) Oct 22 2011 Is this a compiler bug?
• Timon Gehr (14/30) Oct 22 2011 alias has never worked for instance members, even if they are accessible...
• Nick Sabalausky (3/5) Oct 22 2011 Any idea if it's supposed to work?
• Timon Gehr (5/11) Oct 22 2011 I do not know. But if it was not supposed to work, the error message
• Nick Sabalausky (5/18) Oct 22 2011 I've filled a report. If it's invalid it can be closed or changed to "ba...
• Steven Schveighoffer (13/29) Oct 24 2011 alias works on *symbols* not data.

"Nick Sabalausky" <a a.a> writes:

Is this a compiler bug?

--------------------------------
struct Foo
{
    int a;
}

Foo foo;
alias foo.a b;

void main()
{
    b = 5;  // <-- Error
}
--------------------------------

dmd test.d

test.d(11): Error: need 'this' to access member a

I did this on DMD 2.055

Timon Gehr <timon.gehr gmx.ch> writes:

On 10/22/2011 09:28 AM, Nick Sabalausky wrote:
 Is this a compiler bug?

 --------------------------------
 struct Foo
 {
      int a;
 }

 Foo foo;
 alias foo.a b;

 void main()
 {
      b = 5;  //<-- Error
 }
 --------------------------------

 dmd test.d

 test.d(11): Error: need 'this' to access member a

 I did this on DMD 2.055

alias has never worked for instance members, even if they are accessible 
at compile time. The workaround for your example could be this:

ref  property b(){return foo.a;} // instead of alias foo.a b;

Another case where we currently have this meaningless error message:

struct Foo{
     int a;
     int foo(int res=a){return res;}
}

void main(){
     Foo x;
     x.foo();
}

I think that should work.

"Nick Sabalausky" <a a.a> writes:

"Timon Gehr" <timon.gehr gmx.ch> wrote in message 
news:j7u9ld$i8t$1 digitalmars.com...
 alias has never worked for instance members, even if they are accessible 
 at compile time.

Any idea if it's supposed to work?

Timon Gehr <timon.gehr gmx.ch> writes:

On 10/22/2011 11:03 PM, Nick Sabalausky wrote:
 "Timon Gehr"<timon.gehr gmx.ch>  wrote in message
 news:j7u9ld$i8t$1 digitalmars.com...
 alias has never worked for instance members, even if they are accessible
 at compile time.

 Any idea if it's supposed to work?

I do not know. But if it was not supposed to work, the error message 
could certainly be improved. It is odd that the alias compiles fine but 
cannot be used later on. That fact maybe indicates that it is supposed 
to work.

"Nick Sabalausky" <a a.a> writes:

"Timon Gehr" <timon.gehr gmx.ch> wrote in message 
news:j7ve1p$2rds$1 digitalmars.com...
 On 10/22/2011 11:03 PM, Nick Sabalausky wrote:
 "Timon Gehr"<timon.gehr gmx.ch>  wrote in message
 news:j7u9ld$i8t$1 digitalmars.com...
 alias has never worked for instance members, even if they are accessible
 at compile time.

 Any idea if it's supposed to work?

 I do not know. But if it was not supposed to work, the error message could 
 certainly be improved. It is odd that the alias compiles fine but cannot 
 be used later on. That fact maybe indicates that it is supposed to work.

I've filled a report. If it's invalid it can be closed or changed to "bad 
error message":

http://d.puremagic.com/issues/show_bug.cgi?id=6842

"Steven Schveighoffer" <schveiguy yahoo.com> writes:

On Sat, 22 Oct 2011 03:28:53 -0400, Nick Sabalausky <a a.a> wrote:

 Is this a compiler bug?

 --------------------------------
 struct Foo
 {
     int a;
 }

 Foo foo;
 alias foo.a b;

 void main()
 {
     b = 5;  // <-- Error
 }
 --------------------------------

 dmd test.d

 test.d(11): Error: need 'this' to access member a

 I did this on DMD 2.055

alias works on *symbols* not data.

For example, if Foo has a function bar(), aliasing foo.bar is equivalent  
to aliasing Foo.bar.  You are aliasing the *function* not the *delegate*.

So naturally, it would make sense that aliasing foo.a is equivalent to  
aliasing Foo.a, or the symbol that accesses the member 'a' in an instance  
of 'Foo'.

I would expect this may work:

void main()
{
    foo.b = 5;
}

-Steve