The following example demonstrates Delphi's new Strong type checking types, allowing you to define types that require stronger type checking at compile time. Example:

type TStrongType = type Double;
type TWeakType = Double;
procedure AddWeakType(var d : TWeakType);
begin
  d := d +  ;
end;
procedure AddStrongType(var d : TStrongType);
begin
  d := d +  ;
end;
procedure AddDoubleType(var d : Double);
begin
  d := d +  ;
end;
procedure TForm .Button Click(Sender: TObject);
var
  d : Double;
  s : TStrongType;
  w : TWeakType;
begin
  AddDoubleType(d);              { compiles fine }
  AddDoubleType(w);              { compiles fine }
  AddDoubleType(s);              { <- compile error }
  AddDoubleType(double(s));      { compiles fine }
  AddWeakType(d);                { compiles fine }
  AddWeakType(w);                { compiles fine }
  AddWeakType(s);                { <- compile error }
  AddWeakType(TWeakType(s));     { compiles fine }
  AddStrongType(d);              { <- compile error }
  AddStrongType(TStrongType(d)); { compiles fine }
  AddStrongType(w);              { <- compile error }
  AddStrongType(TStrongType(w)); { compiles fine }
  AddStrongType(s);              { compiles fine }
end;