RTL: Implementation of TList<T>.List property

In TList<T> there is no direct access to array items, which will give a big overhead when working with the list in the case of T = record. When accessing through TList<T>.Items[I] there will be a full copying of the record, and also there is no possibility to modify the items, except for full copying of the record, changing its field and reverse assignment.

var
  A: TList<TRect>;
  R: TRect;
...
    // modify list
    for I := 0 to A.Count - 1 do
    begin
      R := A[I];
      R.Left := 123;
      A[I] := R;
    end;  

In Delphi this is solved by an additional property TList<T>.List giving direct access to the elements and reading/modifying is done as when working with a regular array of records.

    // modify list
    for I := 0 to A.Count - 1 do    
      A.List[I].Left := 123;

I would suggest the following patch: fpc_40642.patch