[erlang-bugs] Dialyzer unmatched_returns generates false positives
Tue Apr 12 10:34:54 CEST 2011
Using the option unmatched_returns in dialyzer seems to generate false
positives inside list comprehensions. Consider the following code:
f() -> ok.
g() -> [f() || _E <- lists:seq(1,3)], ok.
It generates the following warning:
Expression produces a value of type ['ok'], but this value is unmatched.
This is okay, because we don't actually match on the return from f(). I
would think that the following fix removes the warning, but it does not:
g() -> [ok = f() || E <- lists:seq(1,3)], ok.
For a list of variable length, the only alternative would be the
following (which dialyzer does not complain about):
g() -> lists:all(fun(ok) -> true end, [ok = f() || _E <-
But it doesn't have the same behavior (will generate a function clause
error instead of a badmatch error if something fails).
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