E2570 Local procedure in generic method or method of generic type is not supported (Delphi)

Go Up to Error and Warning Messages (Delphi)

This happens when you use a local function or procedure inside a generic type.

program E2570;
{E2570 Local procedure in generic method or method of generic type is not supported}

{$APPTYPE CONSOLE}

type
  TMyClass = class
  public
    procedure MyMethod<T>(A: T);
  end;

procedure TMyClass.MyMethod<T>(A: T);

  procedure NotAllowed(B: T); //E2570
  begin
  end;

begin
  NotAllowed(A);
end;

begin
end.