[clean-list] questions about uniqueness

[Valery]

I'm a bit lost with uniqueness typing. Could anyone help me along ?

/1/
Start = (a,f 1 a,f 2 a)
where
    f :: !Int *{#Int} -> *{#Int}
    f i t
    #! t0 = t.[0]
    = {t & [0] = t0 + i}
a :: *{#Int}
a = {i \\ i <- [0..9]}
The code above produces ({0,1,2},{1,1,2},{2,1,2}), as if 'a' was not 
unique, but I expected it to be rejected by the compiler, because 'f' is 
supposed to update its unique argument in place, that is, 'a' should be 
destroyed by the first application of 'f, and the second one should fail.
Where am I wrong ? Does 'f' duplicate its array argument despite the 
uniqueness annotation ?

/2/
What I want actually is a struct that contains a unique array, because 
the array will be updated in place several time later. The struct itself 
will be copied, not updated.
When I try
:: Pos = {t :: *{Int}}
I get "inconsistent attribution of type definition", which is fine, 
since whatever contains something unique has to be unique, but when I try
:: Pos = *{t :: *{Int}}
I get "} expected instead of ::".
How to define this type ?

Valery