[fpc-devel] generics with type-identifier "object" - documented yes, but ...?

Martin Frb lazarus at mfriebe.de
Fri Mar 4 18:31:36 CET 2022

According to  https://www.freepascal.org/docs-html/ref/refse53.html
the keyword "object" is allowed as a "type identifier" for identifiers 
in the "template list" of a generic definition.

Yet, the below does not compile (tested with 3.2.0 / 3.2.2 / 3.2.3 and 
3.3.1 from 2022-Feb-10)

program Project1; {$mode objfpc}{$H+}
   generic TFoo<X: object> = class   end;

Neither does this work (only tested 3.2.3)
   TX = object end;
   generic TFoo<X: TX> = class end;

Whereas each of the below does work fine:
   generic TFoo<X: record> = class   end;
   generic TFoo<X: class> = class   end;
   generic TFoo<X: TObject> = class   end;

The same applies for: "generic TFoo<X: ###> = record end;". So the type 
of the generic itself seems not to affect this.

Similar, the doc says that the keyword "interface" is allowed, but this 
does not work:
   generic TFoo<X: interface> = class   end;
However using IInterface (or any declared interface type) does work
   generic TFoo<X: IInterface> = class   end;


As a side note, the diagram for "identifier list" on the above doc page, 
seems to indicate that the "type identifier" after the colon can be a 
comma separated list.
Is that meant to be like that?

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