Error when using RecordWildCards extension from GHCi - haskell

Question

I have created a function that uses the RecordWildCards syntax for pattern matching on a Haskell record type:
Pragmas
I have placed the pragmas at the top of the file. I have also tried adding it with :set -XRecordWildCards.
{-# LANGUAGE ViewPatterns #-}
{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE RecordWildCards #-}
Type definitions
data ClientR = GovOrgR { clientRName :: String }
| CompanyR { clientRName :: String,
companyId :: Integer,
person :: PersonR,
duty :: String
}
| IndividualR { person :: PersonR }
deriving Show
data PersonR = PersonR {
firstName :: String,
lastName :: String
} deriving Show
Function
greet2 :: ClientR -> String
greet2 IndividualR { person = PersonR { .. } } = "hi" ++ firstName ++ " " ++ lastName + " "
greet2 CompanyR { .. } = "hello " ++ firstName ++ " " ++ lastName ++ "who works as a " ++ duty ++ " " ++ clientRName + " "
greet2 GovOrgR {} = "Welcome"
Error
• Couldn't match expected type ‘[Char]’
with actual type ‘PersonR -> String’
• Probable cause: ‘lastName’ is applied to too few arguments
In the first argument of ‘(++)’, namely ‘lastName’
In the second argument of ‘(++)’, namely
‘lastName ++ "who works as a " ++ duty ++ " " ++ clientRName + " "’
In the second argument of ‘(++)’, namely
‘" "
++
lastName ++ "who works as a " ++ duty ++ " " ++ clientRName + " "’
Failed, modules loaded: none.
When I use this function on CompanyR to match the PersonR using as pattern, I get:
Function
greet2 c#(CompanyR { .. }) = "hello " ++ (firstName $ person c) ++ " " ++ (lastName $ person c)
Error
Couldn't match expected type ‘ClientR -> PersonR’
with actual type ‘PersonR’
• The function ‘person’ is applied to one argument,
but its type ‘PersonR’ has none
In the second argument of ‘($)’, namely ‘person c’
In the first argument of ‘(++)’, namely ‘(firstName $ person c)’
• Couldn't match expected type ‘ClientR -> PersonR’
with actual type ‘PersonR’
• The function ‘person’ is applied to one argument,
but its type ‘PersonR’ has none
In the second argument of ‘($)’, namely ‘person c’
In the second argument of ‘(++)’, namely ‘(lastName $ person c)’

Answer 1

You do it right in your first case here (although I fixed a ++ where you had +):
greet2 :: ClientR -> String
greet2 IndividualR { person = PersonR { .. } } = "hi" ++ firstName ++ " " ++ lastName ++ " "
But here firstName etc are not records in CompanyR so CompanyR { .. } does not bring them into scope:
greet2 CompanyR { .. } = "hello " ++ firstName ++ " " ++ lastName ++ "who works as a " ++ duty ++ " " ++ clientRName + " "
You have to do something like you did in the first case of greet2, just above:
greet2 CompanyR {person = PersonR { .. }, .. } = "hello " ++ firstName ++ " " ++ lastName ++ "who works as a " ++ duty ++ " " ++ clientRName ++ " "