#2819: Bad example code in documentation of Control.Exception.catch
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Reporter: mafo | Owner:
Type: bug | Status: new
Priority: normal | Milestone: 6.10.2
Component: libraries/base | Version: 6.10.1
Severity: trivial | Resolution:
Keywords: | Difficulty: Unknown
Testcase: | Os: Unknown/Multiple
Architecture: Unknown/Multiple |
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Comment (by claus):
The `catchJust` example there also refers to `errorCalls`, which is in the
old exceptions module. Overall, that page could be more explicit about the
recent switch to extensible exception, just as it is still explicit about
the once new asynchronous exceptions. Perhaps a separate section, on that
page, with a brief history of changes, and references? All the examples
should be converted to the intended new style, whatever that is;-)
Summary, for those looking up this ticket: instead of a single, non-
extensible exception type, there are now many specialist exception types
and one extensible exception class. If your exception handler isn't
specific about which type of exceptions it wants to handle, a type error
about ambiguity results. See the instances of the `Exception` class for
specific types of exceptions,
http://www.haskell.org/ghc/docs/latest/html/libraries/base/Control-
Exception.html#1
and annotate the `e` in that example with the type of exception you want
(`IOException` here).
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2819#comment:2>
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