Error message "not in scope" on missing 'deriving'

[mirpa]

Incorrect definition like:

module Der where

data A = A { a :: Int 
           } (Show) -- missing deriving

gives error message:

der.hs:3:14: Not in scope: `a'

I had bigger data structure, where I concentrated on a :: Int part between parentheses trying to figure out why a is not defined. Missing deriving could easily escape your eye in such case.

I would like to get something like:

der.hs:4:14: Unexpected `('

For instance Hugs says:

ERROR "der.hs":4 - Syntax error in input (unexpected `(')

[monoidal]

In HEAD you get a bit better message

Der.hs:3:12: Record syntax is illegal here: {a :: Int}

Der.hs:3:14: Not in scope: ‛a’

It's not ideal, but IMO it gives a good hint that the specific part a::Int is not the issue.