[Haskell-cafe] GHC 7.4 and TypeSynonymInstances

[Simon Peyton-Jones]

It's deliberate. 

As the user manual says (http://www.haskell.org/ghc/docs/latest/html/users_guide/flag-reference.html#id3101511), FlexibleInstances implies TypeSynonymInstances.
See Trac http://hackage.haskell.org/trac/ghc/ticket/4841

I'll clarify the docs a bit.

Simon

| -----Original Message-----
| From: haskell-cafe-bounces at haskell.org [mailto:haskell-cafe-
| bounces at haskell.org] On Behalf Of Ivan Lazar Miljenovic
| Sent: 06 June 2012 23:34
| To: Haskell Cafe
| Subject: Re: [Haskell-cafe] GHC 7.4 and TypeSynonymInstances
| 
| *Bump*
| 
| Especially as there is now a version of the Haskell Platform based
| around GHC-7.4.1, I would appreciate it if this behaviour could be
| clarified.
| 
| On 20 April 2012 15:25, Ivan Lazar Miljenovic
| <ivan.miljenovic at gmail.com> wrote:
| > Has there been a change in the behaviour/requirement of
| > TypeSynonymInstances as of GHC-7.4.1? (Not sure if this behaviour
| > occurs with 7.2.1 as I don't have it installed)
| >
| > I had an instance for String for a class which ghc accepted whilst
| > using FlexibleInstances; however, when trying to load it in 7.0.* it
| > stated that TypeSynonymInstances was needed (which I forgot to add
| > since it didn't seem to need it).
| >
| > All I could find in the release notes was that as of 7.2.1, both
| > extensions were needed, not that one implied the other:
| > http://www.haskell.org/ghc/docs/7.4.1/html/users_guide/release-7-2-1.h
| > tml#id3003826
| >
| > Is this behaviour deliberate, or a bug?
| >
| > --
| > Ivan Lazar Miljenovic
| > Ivan.Miljenovic at gmail.com
| > http://IvanMiljenovic.wordpress.com
| 
| 
| 
| --
| Ivan Lazar Miljenovic
| Ivan.Miljenovic at gmail.com
| http://IvanMiljenovic.wordpress.com
| 
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