Articles [Delphi] Why the compiler generates a "E2018 Record, object or class type required" on typed types…

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Why the compiler generates a `”E2018 Record, object or class type required”` on typed types…
Posted by jpluimers on 2020/05/21

Спойлер: Content

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Why the compiler generates a `”E2018 Record, object or class type required”` on typed types…
Posted by jpluimers on 2020/05/21

Why would the compiler generate a "E2018 Record, object or class type required" when I use a ToUpperInvariant (or any TStringsHelper call) on the Text property of a TEdit?

Full failing code is at [WayBack] on GitHub

Failing line is this:

Edit1.Text := Edit1.Text.ToUpperInvariant;
// the above line generates this error:
// [dcc32 Error] MainFormUnit.pas(29): E2018 Record, object or class type required

This fails as well:

Edit1.Text := TStringHelper.ToUpperInvariant(Edit1.Text);

Why would the compiler (in this case XE8) throw this error?

Note the workaround is simple:

var
  lText: string;
begin
  lText := Edit1.Text;
  Edit1.Text := lText.ToUpperInvariant;

My suspicion is that the Edit property is of type TCaption which is type string.

Could it be that simple?

To which [ David Heffernan ] responded:

Yup, the issue is TCaption has no helper. Pretty distressing.

Typed types are indeed different types. They have been there for a long time (to facilitate generating different type information so you can for instance hook up different property editors to TCaption (a typed string) or TColor (a typed integer).

It is explained at [WayBack] Declaring Types. but has existed since Delphi 1 or Delphi 2. and E2018: Record, object or class type required (Delphi)

More on the implications is at [WayBack] pascal – Delphi Type equivalence and Type equality syntax – Stack Overflow.
–jeroen

Спойлер: Code

unit MainFormUnit;

interface

uses
  System.Classes,
  Vcl.Controls,
  Vcl.Forms,
  Vcl.StdCtrls;

type
  TForm1 = class(TForm)
    Edit1: TEdit;
    procedure Edit1Change(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

uses
  System.SysUtils;

{$R *.dfm}

procedure TForm1.Edit1Change(Sender: TObject);
begin
  Edit1.Text := Edit1.Text.ToUpperInvariant;
  // the above line generates this error:
  // [dcc32 Error] MainFormUnit.pas(29): E2018 Record, object or class type required
end;

end.

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