[Haskell-cafe] Confused about type seen in the wild

[Alexander Solla]

I'm using the yesod-markdown package as a "template" for making my own
yesod-mathjax package.  I'm pretty much done, and it does compile now, but
I'm just really confused by a type that looks like bad syntax.  In fact, I
ended up trying to "fix" it, which lead to errors:

mathJaxField :: Monad m

             => RenderMessage (HandlerSite m) FormMessage

             => Field m MathJax


Notice that there are two type arrows (=>).  Interestingly,


mathJaxField :: ( Monad m

                , RenderMessage (HandlerSite m) FormMessage

                ) => Field m MathJax


compiles too.  So it looks like currying/uncurrying, at the type
level.  But when did this start?  I'm using GHC 7.6.3
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