integer overflow

Can anyone explain me why ModelSim Intel Starter Edition 10.5b does not complain about integer overflows, i.e. why the following code

process
    variable n : integer;
begin
    n := 0;
    report integer'image(n);
    for i in 1 to 1000 loop
        n := ((10 * n) + 3);
        report integer'image(n);
    end loop;
    wait;
end process;

generates that:

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0

3

33

333

3333

33333

333333

3333333

33333333

333333333

-961633963

-1026405035

-1674115755

438711637

92149077

921490773

624973141

1954764117

-1927195307

-2092083883

553997653

1245009237

-434809515

-53127851

-531278507

-1017817771

-1588243115

1297438037

89478485

894784853

357913941

-715827883

1431655765

1431655765

1431655765

...

--- Quote End ---

Thanks,

- Julien