#5642: Deriving Generic of a big type takes a long time and lots of space
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Reporter: basvandijk | Owner: dreixel
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 7.2.1 | Keywords:
Testcase: | Blockedby:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: Compile-time performance bug
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Comment(by basvandijk):
Replying to [comment:2 clintm]:
> Came to report this sort of thing too. I can't actually get this code
to completely run as my machine runs out of memory (12g) almost
immediately.
> ...
This doesn't have anything to do with generics. You just forgot to give a
definition for either `show` or `showsPrec`. Since these methods have
default implementations which are defined in terms of each other you get
an infinite loop which apparently overflows the stack.
Also note that the `Show` type class does not use `DefaultSignatures` and
so does not have default generic implementations.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5642#comment:5>
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