[fpc-devel] Generics are still broken

[Anthony Walter]

Generics still have a lot of problems.  I know they've been in the works
for years but they still fail easily. Consider the Delphi mode below, I get
"Error: Generics without specialization cannot be used as a type for a
variable"

I could easily write up a whole bunch of test cases were generic still
fail, both in Fpc and Delphi modes. If someone is considering working on
the compiler to fix the problems with generics I can happily send them a
bunch of test cases where the compiler currently fails.

{$mode delphi}

{ TEnumerator<T> }

type
  TEnumerator<T> = class abstract
  protected
    function DoGetCurrent: T; virtual; abstract;
    function DoMoveNext: Boolean; virtual; abstract;
  public
    property Current: T read DoGetCurrent;
    function MoveNext: Boolean;
  end;

{ TEnumerable<T> }

  TEnumerable<T> = class abstract
  protected
    function DoGetEnumerator: TEnumerator<T>; virtual; abstract; // Error:
Generics without specialization cannot be used as a type for a variable
  public
    function GetEnumerator: TEnumerator<T>;
  end;
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