A typesafe FreeAndNil a Cast with more descriptive error in a TObjectHelper that limits the generics to class references.

ObjectHelperUnit.pas

unit ObjectHelperUnit;

interface

type
  TObjectHelper = record
    class function Cast<T: class>(const aValue: TObject): T; static;
    class procedure FreeAndNil<T: class>(var Value: T); static;
  end;

implementation

uses
  System.SysConst,
  System.SysUtils;

class function TObjectHelper.Cast<T>(const aValue: TObject): T;
var
  lException: Exception;
begin
  if Assigned(aValue) then
  begin
    if aValue is T then
      Result := T(aValue)
    else
    begin
      lException := EInvalidCast.CreateFmt('%s; actual type %s but expected %s.',
        [SInvalidCast, aValue.QualifiedClassName, T.QualifiedClassName]);
      raise lException;
    end;
  end
  else
    Result := nil;
end;

class procedure TObjectHelper.FreeAndNil<T>(var Value: T);
begin
  System.SysUtils.FreeAndNil(Value);
end;

end.