Delphi 2006 - Assigning dynamic array function results

Delphi 2006 - Assigning dynamic array function results

I had code with the basic constructs illustrated by the following:
type
TDynamicArray = array of double ;
var
a : TDynamicArray ;
function Func : TDynamicArray ;
var
b : TDynamicArray ;
begin
SetLength (B, 3) ;
b [0] := 0.0 ;
b [1] := 1.0 ;
b [2] := 2.0 ;
Result := b ; // note 1 -- should use Result := Copy (b, 0, Length
(b))
end ;
begin
a := Func ; // note 2 -- should we (or could we) use a := Copy (Func, 0,
Length (Func))
end.
It had been working fine until lately when the function started returning
empty arrays. I then spot this which enlightens me to the fact that simple
assignment isn't correct, I need to use Copy.
Two questions:
I realise I need 'Copy' on the line marked Note 1 to assign to the
function result. Do I need to use Copy also on the assignment of the
function result to array a (line Note 2)?.
Why did the compiler allow my construct and what was the compiled code
actually doing?
I realise I could try these things and see, but I'm a little spooked by
the compiler letting questionable stuff through.