Idea to solve a circular reference issue with classes.

[marcov]

    2.  IDEA 1:
           Forwarding a Class;
           Class Name = Class IS UnitNameThatHostIT.CLASSNAME;
           Maybe the compiler can just look there once for the Class definition?

In a circular dependency relation, the UnitNameThatHostIt is not be compiled yet, so you can't reference it.

     3. IDEA 2:
            Have the compiler look at the Uses List in the Implementation section and use that reference if one isn't declared in the interface section with maybe a special indicator or HINT ?

Declare before use is pretty big in Pascal, and such reference is a "use".

Interface and implementation and order of compilation in general is quite rigidly defined in a single pass compiler. You would need to change the whole compiler and language to a multi pass model to realistically do something so direct. 

There are other workarounds.

Factor one of the classes to a base class in a different unit, with virtual methods if needed. Yes, that is not you need to typecast if you need derivative properties.  Or if typecasting gets too much, use a type helper with an inline method that does the casts etc.

[creaothceann]

Maybe I'm not understanding the problem correctly, but again, what exactly is the problem with putting these classes into the same unit?

[marcov]

Maybe I'm not understanding the problem correctly, but again, what exactly is the problem with putting these classes into the same unit?

That's pretty much the default solution yes. I assumed that was not possible.

[PascalDragon]

IDEA 1: [...]
IDEA 2: [...]

IDEA3:
Allow an external declaration for the class. Then the class could only be used to define member variables (which normally is enough) and not to derive a class etc.

Code: Pascal  [Select][+][-]

1. Type
2.   TFoo = class; external;

(hypothetic code)

EDIT: No idea how to implement that. I guess at some point the unit where the class is expected has to be specified.

I had tried that some years ago considering that the JVM target supports that for external classes, but it blew up in various corner cases and I scraped the idea for the time being.

[jamie]

Maybe we can try again?
Jamie

[Thaddy]

With an instantiated class that works.. With the class type it doesn't.
But look at my last code example: that does work, but not without softcasts.

If you can provide me with some external code that you want to address, I would be happy to explore other solutions than interface or old school.

[jamie]

So that's it, fight with a stubborn compiler.