Add NamedRoutes instance for IsElem

Author: RaoulHC

changelog.d/1699

@@ -0,0 +1,7 @@
+synopsis: Add NamedRoutes instance to IsElem
+prs: #1699
+issues: #1674
+description: {
+Add missing IsElem instance for NamedRoutes, this allows links to be checked
+with `safeLink`.
+}

servant/src/Servant/API/TypeLevel.hs

@@ -64,6 +64,10 @@ import           Servant.API.QueryParam
                  (QueryFlag, QueryParam, QueryParams)
 import           Servant.API.ReqBody
                  (ReqBody)
+import           Servant.API.NamedRoutes
+                 (NamedRoutes)
+import           Servant.API.Generic
+                 (ToServantApi)
 import           Servant.API.Sub
                  (type (:>))
 import           Servant.API.Verbs
@@ -142,6 +146,7 @@ type family IsElem endpoint api :: Constraint where
   IsElem (Verb m s ct typ) (Verb m s ct' typ)
                                           = IsSubList ct ct'
   IsElem e e                              = ()
+  IsElem e (NamedRoutes rs)               = IsElem e (ToServantApi rs)
   IsElem e a                              = IsElem' e a
 
 -- | Check whether @sub@ is a sub-API of @api@.