Ensure that loading testfiles produces at least one diagnostic.

completion/Context.hs used to generate a diagnostic for the unused "x", but no
longer does so without -Wunused-binds.

completion/Completion.hs used to generate a diagnostic for the unused import of
Data.Maybe, but no longer does so without -Wunused-imports.

We could add these flags like:
    {-# OPTIONS_GHC -Wunused-binds #-}

But that would force us to update all the hardcoded line numbers in the unit tests.

Instead we just add a redundant id, carefully positioned to avoid disturbing any
hardcoded positions.

Author: peterwicksstringfield

test/testdata/completion/Completion.hs

@@ -6,4 +6,4 @@ main :: IO ()
 main = putStrLn "hello"
 
 foo :: Either a b -> Either a b
-foo = id
+foo = id id

test/testdata/completion/Context.hs

@@ -1,4 +1,4 @@
 module Context where
 import Control.Concurrent as Conc
 foo :: Int -> Int
-foo x = abs 42
+foo x = abs $ id 42