How to know what type is a var?

Question

TypeInfo(Type) returns the info about the specified type, is there any way to know the typeinfo of a var?

var
  S: string;
  Instance: IObjectType;
  Obj: TD         


        

Answer 1

With generics, it is now possible to get the type info without specifying it. Certain users indicated the following code doesn't compile without errors. As of Delphi 10 Seattle, version 23.0.20618.2753, it compiles without errors, as seen below in the screenshot.

program TypeInfos;
{$APPTYPE CONSOLE}
{$R *.res}

uses
  System.SysUtils, System.TypInfo;

type
  TTypeInfo = class
    class procedure ShowTypeInfo(const X: T);
  end;

{ TTypeInfo }

class procedure TTypeInfo.ShowTypeInfo(const X: T);
var
  LTypeInfo: PTypeInfo;
begin
  LTypeInfo := TypeInfo(T);
  WriteLn(LTypeInfo.Name);
end;

var
  L: Exception;
  B: Boolean;
begin
                             // Console output
  TTypeInfo.ShowTypeInfo(L); // Exception
  TTypeInfo.ShowTypeInfo(B); // Boolean
end.