DCC allows the subj (provided that the class type is known at compile time), FPC does not.
The attached init_methptr_with_classmeth.patch implements this feature.
-------8<-------
type C = class
class procedure Foo;
end;
class procedure C.Foo; begin end;
type CC = class of C;
type H = class helper for C end;
type T = procedure of object;
//var aC: C = nil;
//var aCC: CC = nil;
// Still rejected:
//var ViaInstance: T = aC.Foo;
//var ViaClassRef: T = aCC.Foo;
const ViaClass: T = C.Foo;
// NB: This needs metaclass_meth_to_procvar-2.patch
// from https://lists.freepascal.org/pipermail/fpc-devel/2021-December/044249.html
// Otherwise: AV in FPC
var ViaMetaclass: T = CC.Foo;
// TODO: Currently, ICE 2021122302 -- needs to be fixed elsewhere.
// See https://lists.freepascal.org/pipermail/fpc-devel/2021-December/044251.html
//var ViaHelper: T = H.Foo;
procedure Report(const s: string; const X: T);
var Status: Boolean;
begin
Status := (TMethod(X).Code = @C.Foo) and (TMethod(X).Data = Pointer(C));
writeln(s, ': ', Status)
end;
begin
Report('via class', ViaClass);
Report('via metaclass', ViaMetaclass)
end.
-------8<-------Proposed new error message for parser_e_no_procvarobj_const: Cannot initialize a method pointer: Self pointer is not known at compile time In order to initialize a method pointer with a method, the value of the Self pointer for calling that method at run time must be known at compile time. Thus, a method pointer can be initialized either with NIL, or with a class method that is accessed via a class type or a class reference type.
βþ