Invalid

with Ada.Text_IO; use  Ada.Text_IO;

procedure Array_Test is
   From_Array : array (1 .. 3) of Integer;
   To_Array   : array (1 .. 3) of Integer;
begin
   From_Array := (1, 2, 3);
   To_Array   := From_Array;
   From_Array := (others => 0);

   for I in From_Array'Range loop
      Put(Integer'Image(From_Array(I)));
   end loop;

   for I in To_Array'Range loop
      Put(Integer'Image(To_Array(I)));
   end loop;
end Array_Test;

Valid

with Ada.Text_IO; use  Ada.Text_IO;

procedure Array_Test is
   type Sample_Array_Type is array (1 .. 3) of Integer;
   From_Array : Sample_Array_Type;
   To_Array   : Sample_Array_Type;
begin
   From_Array := (1, 2, 3);
   To_Array   := From_Array;
   From_Array := (others => 0);

   for I in Sample_Array_Type'Range loop
      Put_Line(Integer'Image(From_Array(I)));
   end loop;

   for I in Sample_Array_Type'Range loop
      Put_Line(Integer'Image(To_Array(I)));
   end loop;
end Array_Test;

Result:
0
0
0
1
2
3