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While discussing a syntax question, I wanted to say "you first look up all the fixity information" but then I got:

Prelude> :i ($)
($) :: (a -> b) -> a -> b 	-- Defined in ‘GHC.Base’
infixr 0 $

Prelude> foo # bar = undefined
Prelude> :i (#)
(#) :: p1 -> p2 -> a 	-- Defined at <interactive>:1:5

So what fixity does # have? Of course, every-one knows it's infixl 9 (https://www.haskell.org/onlinereport/haskell2010/haskellch4.html#x10-820004.4.2) (NB: and it's easy to find, too - just scroll down to the very end of https://www.haskell.org/documentation/ because that's obviously where the most important documents are)

Well anyway, could ghci perhaps print a line

-- lacking a fixity declaration, assumed to be infixl 9 

or

infixl 9 #  -- assumed, since a fixity declaration is lacking

where I'm trying to use language of the standard verbally.