Remove the unused 'visited' field from the parser state.

The parser state is not exposed by this module. Considering that nothing
in the parser relies on it, we can safely omit it.

src/Url/Parser.elm

@@ -61,8 +61,7 @@ type Parser a b =
 
 
 type alias State value =
-  { visited : List String
-  , unvisited : List String
+  { unvisited : List String
   , params : Dict String (List String)
   , frag : Maybe String
   , value : value
@@ -111,14 +110,14 @@ The path segment must be an exact match!
 -}
 s : String -> Parser a a
 s str =
-  Parser <| \{ visited, unvisited, params, frag, value } ->
+  Parser <| \{ unvisited, params, frag, value } ->
     case unvisited of
       [] ->
         []
 
       next :: rest ->
         if next == str then
-          [ State (next :: visited) rest params frag value ]
+          [ State rest params frag value ]
 
         else
           []
@@ -143,15 +142,15 @@ You can use it to define something like “only CSS files” like this:
 -}
 custom : String -> (String -> Maybe a) -> Parser (a -> b) b
 custom tipe stringToSomething =
-  Parser <| \{ visited, unvisited, params, frag, value } ->
+  Parser <| \{ unvisited, params, frag, value } ->
     case unvisited of
       [] ->
         []
 
       next :: rest ->
         case stringToSomething next of
           Just nextValue ->
-            [ State (next :: visited) rest params frag (value nextValue) ]
+            [ State rest params frag (value nextValue) ]
 
           Nothing ->
             []
@@ -205,14 +204,14 @@ slash (Parser parseBefore) (Parser parseAfter) =
 -}
 map : a -> Parser a b -> Parser (b -> c) c
 map subValue (Parser parseArg) =
-  Parser <| \{ visited, unvisited, params, frag, value } ->
+  Parser <| \{ unvisited, params, frag, value } ->
     List.map (mapState value) <| parseArg <|
-      State visited unvisited params frag subValue
+      State unvisited params frag subValue
 
 
 mapState : (a -> b) -> State a -> State b
-mapState func { visited, unvisited, params, frag, value } =
-  State visited unvisited params frag (func value)
+mapState func { unvisited, params, frag, value } =
+  State unvisited params frag (func value)
 
 
 {-| Try a bunch of different path parsers.
@@ -321,8 +320,8 @@ segments.
 -}
 query : Query.Parser query -> Parser (query -> a) a
 query (Q.Parser queryParser) =
-  Parser <| \{ visited, unvisited, params, frag, value } ->
-    [ State visited unvisited params frag (value (queryParser params))
+  Parser <| \{ unvisited, params, frag, value } ->
+    [ State unvisited params frag (value (queryParser params))
     ]
 
 
@@ -350,8 +349,8 @@ be handy for handling links to DOM elements within a page. Pages like this one!
 -}
 fragment : (Maybe String -> fragment) -> Parser (fragment -> a) a
 fragment toFrag =
-  Parser <| \{ visited, unvisited, params, frag, value } ->
-    [ State visited unvisited params frag (value (toFrag frag))
+  Parser <| \{ unvisited, params, frag, value } ->
+    [ State unvisited params frag (value (toFrag frag))
     ]
 
 
@@ -402,7 +401,7 @@ the initial URL and any changes.
 parse : Parser (a -> a) a -> Url -> Maybe a
 parse (Parser parser) url =
   getFirstMatch <| parser <|
-    State [] (preparePath url.path) (prepareQuery url.query) url.fragment identity
+    State (preparePath url.path) (prepareQuery url.query) url.fragment identity
 
 
 getFirstMatch : List (State a) -> Maybe a