Behaviour specs aren't used by check_specs

[puzza007]

Given the following behaviour

-module(bar).

-callback behaviour_spec(integer()) -> integer().

and module

-module(foo).

-behaviour(bar).

-export([normal_spec/1, behaviour_spec/1]).

-spec normal_spec(integer()) -> integer().
normal_spec(A) ->
    A + 1.

behaviour_spec(A) ->
    [A].

Dialyzer gives

~/src/pt $ dialyzer -r .
  Checking whether the PLT /Users/puzza/.dialyzer_plt is up-to-date... yes
  Proceeding with analysis...
foo.erl:11: The inferred return type of behaviour_spec/1 ([any(),...]) has nothing in common with integer(), which is the expected return type for the callback of bar behaviour
 done in 0m5.04s
done (warnings were emitted)

But PropEr gives:

~/src/pt $ erl -pa ../proper/ebin
Erlang R16B02 (erts-5.10.3) [source] [64-bit] [smp:4:4] [async-threads:10] [kernel-poll:false]

Eshell V5.10.3  (abort with ^G)
1> proper:check_specs(foo).
Testing foo:normal_spec/1
....................................................................................................
OK: Passed 100 test(s).

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