are patterns synonyms definable in GHCI?

[Roman Cheplyaka]

On 18/12/14 12:51, Dr. ERDI Gergo wrote:
> On Thu, 18 Dec 2014, Carter Schonwald wrote:
> 
>> Hey all,I was trying to define some pattern synonyms in ghci recently,
>> and that doesnt
>> seem to work. Is that something slated to be fix in 7.10 or something?
> 
> I thought GHCi accepts things that would be valid in a 'do' section? So
> e.g.
> 
> x = ()
> 
> doesn't work in GHCi, but
> 
> let x = ()
> 
> does.
> 
> Pattern synonyms don't work for the exact same reason: they are not
> valid inside a 'do' block.

That's not true. Since 7.6, IIRC, you can define data types and
instances in ghci.

See also https://ghc.haskell.org/trac/ghc/ticket/7253

Roman