Apply suggested changes

Author: BinderDavid

message-index/messages/GHC-54540/constructorsNotInScope/after/ConstructorsNotInScope.hs

@@ -3,4 +3,4 @@ module ConstructorsNotInScope where
 
 import System.IO( Handle )
 
--- It is not possible to derive an instance for the typeclass in this module.
+-- It is not possible to derive an instance for the type class in this module.

message-index/messages/GHC-93557/illegalSynonymInstance/index.md

@@ -2,8 +2,8 @@
 title: Cannot implement a typeclass for type synonyms by default
 ---
 
-The programmer defined a data type `RGB`, and a type synonym `T`, and then tried to implement an instance of the typeclass `Eq` for `T`.
-In the language version Haskell2010 this is not allowed, since all typeclass instances have to start with a type constructor.
+The programmer defined a data type `RGB`, and a type synonym `T`, and then tried to implement an instance of the type class `Eq` for `T`.
+In the language version Haskell 2010 this is not allowed, since all type class instances have to start with a type constructor.
 This problem can be fixed by implementing the typeclass instance directly for the type `RGB` instead of the type synonym `T`.
 
 ```

message-index/messages/GHC-93557/index.md

@@ -5,11 +5,12 @@ severity: error
 introduced: 9.8.1
 ---
 
-Using the language version Haskell2010, only certain types are allowed as instances of a typeclass.
-Every typeclass instance in Haskell2010 has the following form:
+Using the language version Haskell 2010, only certain types are allowed as instances of a type class.
+Every type class instance in Haskell 2010 has the following form:
 ```
 instance C t where
 ````
-Here, `C` is the name of a typeclass, such as `Eq`, `Show` or `Read`, and `t` is a type.
+Here, `C` is the name of a type class, such as `Eq`, `Show`, `Read` or `Functor`, and `t` is a type.
 But only a subset of types `t` is allowed to appear in typeclass instances.
 These types must all have the form `T` or `T a ... b`, where `T` has to be the name of a type introduced by a data or newtype declaration, and the arguments `a` to `b` all have to be type variables.
+For example, `Maybe a` is allowed as a type in an instance, because the data type `Maybe` instantiates `T` and `a` is a type variable`, but `Maybe Int` is not allowed, since `Int` is not a type variable.