#5377: TypeSynonymInstances dysfunctional in ghc-7.2.1-rc1?
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Reporter: hvr | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 7.1 | Keywords:
Testcase: | Blockedby:
Os: Linux | Blocking:
Architecture: x86_64 (amd64) | Failure: GHC rejects valid program
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Comment(by hvr):
For completeness:
{{{
$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 7.2.0.20110728
$ ghc -c ghc_ticket_5377.hs
ghc_ticket_5377.hs:9:10:
Illegal instance declaration for `Bar Foo'
(All instance types must be of the form (T t1 ... tn)
where T is not a synonym.
Use -XTypeSynonymInstances if you want to disable this.)
In the instance declaration for `Bar Foo'
$ ghc -XTypeSynonymInstances -c ghc_ticket_5377.hs
ghc_ticket_5377.hs:9:10:
Illegal instance declaration for `Bar Foo'
(All instance types must be of the form (T a1 ... an)
where a1 ... an are *distinct type variables*,
and each type variable appears at most once in the instance head.
Use -XFlexibleInstances if you want to disable this.)
In the instance declaration for `Bar Foo'
$ ghc -XFlexibleInstances -c ghc_ticket_5377.hs
ghc_ticket_5377.hs:1:1:
The function `main' is not defined in module `Main'
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5377#comment:1>
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