Compiler not mapping a class method to an interface method - delphi

Question

I am using Delphi Pro 10.2.3 Tokyo. I want to create a TDataset wrapper class which I can use to enumerate through a list of IData descendants with a for-in loop. When I try to compile the code below, I get the following error message.
[dcc32 Error] Core.Data.DatasetAdapter.pas(25): E2291 Missing implementation of interface method IEnumerator.GetCurrent
Clearly, GetCurrent is implemented. Any idea how to fix this?
unit Core.Data.DatasetAdapter;
interface
uses
Data.Db
;
type
IData = interface
['{15D1CF4F-B9E1-4525-B035-24B9A6584325}']
end;
IDataList<T: IData> = interface
['{9FEE9BB1-A983-4FEA-AEBF-4D3AF5219444}']
function GetCount: Integer;
function GetCurrent: T;
procedure Load;
procedure Unload;
property Count: Integer read GetCount;
property Current: T read GetCurrent;
end;
TDatasetAdapter<T: IData> = class(
TInterfacedObject
, IData, IDataList<T>
, IEnumerator<T>
)
private
FBof: Boolean;
FDataset: TDataset;
FIntf: T;
function GetCount: Integer;
function GetCurrent: T;
function GetEof: Boolean;
function GetInterface: T;
function MoveNext: Boolean;
procedure Reset;
protected
function FieldByName(const FieldName: string): TField;
procedure MapFields; virtual;
property Dataset: TDataset read FDataset;
public
constructor Create(ADataset: TDataset); virtual;
function GetEnumerator: IEnumerator<T>;
procedure Cancel;
procedure Close;
procedure Delete;
procedure Edit;
procedure First;
procedure Insert;
procedure Load;
procedure Next;
procedure Open;
procedure Post;
procedure UnLoad;
property Count: Integer read GetCount;
property Eof: Boolean read GetEof;
end;
implementation
uses
System.SysUtils
, System.TypInfo
;
{ TDatasetAdapter<T> }
{
****************************** TDatasetAdapter<T> ******************************
}
constructor TDatasetAdapter<T>.Create(ADataset: TDataset);
begin
FDataset := ADataset;
FIntf := GetInterface;
end;
procedure TDatasetAdapter<T>.Cancel;
begin
FDataset.Cancel;
end;
procedure TDatasetAdapter<T>.Close;
begin
FDataset.Close;
end;
procedure TDatasetAdapter<T>.Delete;
begin
FDataset.Delete;
end;
procedure TDatasetAdapter<T>.Edit;
begin
FDataset.Edit;
end;
function TDatasetAdapter<T>.FieldByName(const FieldName: string): TField;
begin
Result := FDataset.FieldByName(FieldName);
end;
procedure TDatasetAdapter<T>.First;
begin
FDataset.First;
end;
function TDatasetAdapter<T>.GetCount: Integer;
begin
Result := FDataset.RecordCount;
end;
function TDatasetAdapter<T>.GetCurrent: T;
begin
Result := FIntf;
end;
function TDatasetAdapter<T>.GetEnumerator: IEnumerator<T>;
begin
Reset;
Result := Self;
end;
function TDatasetAdapter<T>.GetEof: Boolean;
begin
Result := FDataset.Eof;
end;
function TDatasetAdapter<T>.GetInterface: T;
var
LGuid: TGuid;
begin
LGuid := GetTypeData(TypeInfo(T))^.Guid;
if not Supports(Self, LGuid, Result) then
Result := nil;
end;
procedure TDatasetAdapter<T>.Insert;
begin
FDataset.Insert;
end;
procedure TDatasetAdapter<T>.Load;
begin
Open;
MapFields;
end;
procedure TDatasetAdapter<T>.MapFields;
begin
//Stub procedure
end;
function TDatasetAdapter<T>.MoveNext: Boolean;
begin
if FBof then FBof := False
else Next;
Result := not Eof;
end;
procedure TDatasetAdapter<T>.Next;
begin
FDataset.Next;
end;
procedure TDatasetAdapter<T>.Open;
begin
FDataset.Open;
end;
procedure TDatasetAdapter<T>.Post;
begin
FDataset.Post;
end;
procedure TDatasetAdapter<T>.Reset;
begin
FBof := True;
First;
end;
procedure TDatasetAdapter<T>.UnLoad;
begin
Close;
end;
end.

Answer 1

You need to resolve function GetCurrent: T twice: for IDataList<T> and for Enumerator<T>. But you also need one for the non-generic ancestor of IEnumerator<T>: IEnumerator. Apparently that is not hidden by the GetCurrent method of IEnumerator<T>.
Try method resolution clauses:
function GetGenericCurrent: T; // implement this
function IDataList<T>.GetCurrent = GetGenericCurrent;
function IEnumerator<T>.GetCurrent = GetGenericCurrent;
function GetCurrent: TObject; // implement this -- can return nil.
The implementation of both can be the same, but you will have to make two methods. The one for the non-generic IEnumerator can return nil.
Update
I had to modify the code above. Now it should work. It is not necessary to have two implementations for GetCurrent returning T, but you must have one returning TObject.