Question: "assume", "type" and "if"

Can anyone tell me why "type" answers "false" and why do I get an error message, from the following simple code sequence (Maple 10)?

Thanks

restart;
> testp:=proc(m);
> if (m=0) then 0;
> elif (m>0) then 1;
> elif (m<0) then -1;
> end if;
> end proc;
> assume(n,posint);
> about(n);
> type(n,posint);
> is(n,posint);
> testp(n);
> testp(-1);

testp := proc(m)
if m = 0 then 0
elif 0 < m then 1
elif m < 0 then -1
end if
end proc

Originally n, renamed n~:
is assumed to be: AndProp(integer,RealRange(1,infinity))


false


true

Error, (in testp) cannot determine if this expression is true or false: 0 < n


-1
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