Hello!
I'm hacking dmd compiler and trying to look on members array just after parse module.

for(uint i = 0; i < members.dim; i++)
{
     Dsymbol m = (*members)[i];

// It is good, but further:

    Import imp = cast(Import) m;
    if (imp !is null)
    {
        printf("++++ import %s.%s\n", imp.packages.toChars(), imp.id.toChars());
    }
// ...
}

For really imports casting doing well. But for not imports it again casts, imp not is null and  the compiler crashes.
What I'm doing wrong?

On 7/25/17 4:36 PM, unDEFER wrote:
> Hello!
> I'm hacking dmd compiler and trying to look on members array just after parse module.
> 
> for(uint i = 0; i < members.dim; i++)
> {
>       Dsymbol m = (*members)[i];
> 
> // It is good, but further:
> 
>      Import imp = cast(Import) m;
>      if (imp !is null)
>      {
>          printf("++++ import %s.%s\n", imp.packages.toChars(), imp.id.toChars());
>      }
> // ...
> }
> 
> For really imports casting doing well. But for not imports it again casts, imp not is null and  the compiler crashes.
> What I'm doing wrong?

I think it's likely that these are actually C++ classes, and probably there is no RTTI, so this is a reinterpret cast. This is a wild guess, but much of the compiler still needs to interface with C++ backend.

I would look elsewhere in the compiler to see how they handle this type of thing. Not sure of dynamic_cast support?

-Steve

I have found the answer in the code.
Right code is:

Import imp = m.isImport();
if (imp !is null)

Thank you.

On Tuesday, 25 July 2017 at 21:06:25 UTC, unDEFER wrote:
> I have found the answer in the code.
> Right code is:
>
> Import imp = m.isImport();
> if (imp !is null)
>
> Thank you.

grep for kluge in code, you'll find all the places it does its own RTTI.

On 2017-07-25 23:06, unDEFER wrote:
> I have found the answer in the code.
> Right code is:
> 
> Import imp = m.isImport();
> if (imp !is null)
> 
> Thank you.

That's the correct solution. For Expression, there's a field called "op" that indicates what kind of expression it is, which can used in combination with a cast.

-- 
/Jacob Carlborg

On Wednesday, 26 July 2017 at 06:50:21 UTC, Jacob Carlborg wrote:
> For Expression, there's a field called "op" that indicates what kind of expression it is, which can used in combination with a cast.

Thank you for hint!