diff --git a/.travis.yml b/.travis.yml
--- a/.travis.yml
+++ b/.travis.yml
@@ -15,25 +15,22 @@
   include:
     - env: CABALVER=1.18 GHCVER=7.4.2
       compiler: ": #GHC 7.4.2"
-      addons: {apt: {packages: [cabal-install-1.18,ghc-7.4.2,alex-3.1.4,happy-1.19.5], sources: [hvr-ghc]}}
+      addons: {apt: {packages: [cabal-install-1.18,ghc-7.4.2,alex-3.1.7,happy-1.19.5], sources: [hvr-ghc]}}
     - env: CABALVER=1.18 GHCVER=7.6.3
       compiler: ": #GHC 7.6.3"
-      addons: {apt: {packages: [cabal-install-1.18,ghc-7.6.3,alex-3.1.4,happy-1.19.5], sources: [hvr-ghc]}}
+      addons: {apt: {packages: [cabal-install-1.18,ghc-7.6.3,alex-3.1.7,happy-1.19.5], sources: [hvr-ghc]}}
     - env: CABALVER=1.18 GHCVER=7.8.4
       compiler: ": #GHC 7.8.4"
-      addons: {apt: {packages: [cabal-install-1.18,ghc-7.8.4,alex-3.1.4,happy-1.19.5], sources: [hvr-ghc]}}
-    - env: CABALVER=1.22 GHCVER=7.10.1
-      compiler: ": #GHC 7.10.1"
-      addons: {apt: {packages: [cabal-install-1.22,ghc-7.10.1,alex-3.1.4,happy-1.19.5], sources: [hvr-ghc]}}
-    - env: CABALVER=1.22 GHCVER=7.10.2
-      compiler: ": #GHC 7.10.2"
-      addons: {apt: {packages: [cabal-install-1.22,ghc-7.10.2,alex-3.1.4,happy-1.19.5], sources: [hvr-ghc]}}
+      addons: {apt: {packages: [cabal-install-1.18,ghc-7.8.4,alex-3.1.7,happy-1.19.5], sources: [hvr-ghc]}}
+    - env: CABALVER=1.22 GHCVER=7.10.3
+      compiler: ": #GHC 7.10.3"
+      addons: {apt: {packages: [cabal-install-1.22,ghc-7.10.3,alex-3.1.7,happy-1.19.5], sources: [hvr-ghc]}}
     - env: CABALVER=1.24 GHCVER=8.0.1
       compiler: ": #GHC 8.0.1"
-      addons: {apt: {packages: [cabal-install-1.24,ghc-8.0.1,alex-3.1.4,happy-1.19.5], sources: [hvr-ghc]}}
+      addons: {apt: {packages: [cabal-install-1.24,ghc-8.0.1,alex-3.1.7,happy-1.19.5], sources: [hvr-ghc]}}
     - env: CABALVER=1.24 GHCVER=head
       compiler: ": #GHC head"
-      addons: {apt: {packages: [cabal-install-1.24,ghc-head,alex-3.1.4,happy-1.19.5], sources: [hvr-ghc]}}
+      addons: {apt: {packages: [cabal-install-1.24,ghc-head,alex-3.1.7,happy-1.19.5], sources: [hvr-ghc]}}
 
   allow_failures:
    - env: CABALVER=1.24 GHCVER=head
@@ -41,7 +38,7 @@
 before_install:
  - unset CC
  - export HAPPYVER=1.19.5
- - export ALEXVER=3.1.4
+ - export ALEXVER=3.1.7
  - export PATH=~/.cabal/bin:/opt/ghc/$GHCVER/bin:/opt/cabal/$CABALVER/bin:/opt/happy/$HAPPYVER/bin:/opt/alex/$ALEXVER/bin:$PATH
 
 install:
@@ -72,7 +69,7 @@
      rm -rf $HOME/.cabsnap;
      mkdir -p $HOME/.ghc $HOME/.cabal/lib $HOME/.cabal/share $HOME/.cabal/bin;
      cabal install --only-dependencies --enable-tests lens.cabal reflection/;
-     if [ "$GHCVER" = "7.10.1" ]; then cabal install Cabal-1.22.4.0; fi;
+     if [ "$GHCVER" = "7.10.3" ]; then cabal install Cabal-1.22.4.0; fi;
    fi
 
 # snapshot package-db on cache miss
diff --git a/CHANGELOG.markdown b/CHANGELOG.markdown
--- a/CHANGELOG.markdown
+++ b/CHANGELOG.markdown
@@ -1,3 +1,9 @@
+4.13.2
+------
+* Restore default signature for `Control.Lens.At.at`
+* Improve operations for `Data.Sequence.Seq`
+* Fix `declarePrisms` behavior on GHC 8 using GADT record syntax
+
 4.13.1
 ------
 * Modified to enable the `doctests` to build with `stack`.
diff --git a/lens.cabal b/lens.cabal
--- a/lens.cabal
+++ b/lens.cabal
@@ -1,6 +1,6 @@
 name:          lens
 category:      Data, Lenses, Generics
-version:       4.13.1
+version:       4.13.2
 license:       BSD3
 cabal-version: >= 1.8
 license-file:  LICENSE
@@ -423,7 +423,7 @@
   else
     build-depends:
       base,
-      hlint >= 1.7
+      hlint >= 1.9.27
 
 -- Basic benchmarks for the uniplate-style combinators
 benchmark plated
diff --git a/src/Control/Lens/At.hs b/src/Control/Lens/At.hs
--- a/src/Control/Lens/At.hs
+++ b/src/Control/Lens/At.hs
@@ -52,6 +52,7 @@
 import Control.Lens.Traversal
 import Control.Lens.Lens
 import Control.Lens.Setter
+import Control.Lens.Type
 import Control.Lens.Indexed
 import Data.Array.IArray as Array
 import Data.Array.Unboxed
@@ -198,11 +199,9 @@
   -- >>> Seq.fromList [] ^? ix 2
   -- Nothing
   ix :: Index m -> Traversal' m (IxValue m)
-#ifdef DEFAULT_SIGNATURES
   default ix :: (Applicative f, At m) => Index m -> LensLike' f m (IxValue m)
   ix = ixAt
   {-# INLINE ix #-}
-#endif
 
 -- | An indexed version of 'ix'.
 --
diff --git a/src/Control/Lens/Each.hs b/src/Control/Lens/Each.hs
--- a/src/Control/Lens/Each.hs
+++ b/src/Control/Lens/Each.hs
@@ -83,11 +83,9 @@
 -- ("HELLO","WORLD")
 class Each s t a b | s -> a, t -> b, s b -> t, t a -> s where
   each :: Traversal s t a b
-#ifndef HLINT
   default each :: (Traversable g, s ~ g a, t ~ g b) => Traversal s t a b
   each = traverse
   {-# INLINE each #-}
-#endif
 
 -- | @'each' :: 'Traversal' (a,a) (b,b) a b@
 instance (a~a', b~b') => Each (a,a') (b,b') a b where
diff --git a/src/Control/Lens/Empty.hs b/src/Control/Lens/Empty.hs
--- a/src/Control/Lens/Empty.hs
+++ b/src/Control/Lens/Empty.hs
@@ -63,11 +63,9 @@
   -- >>> isn't _Empty [1,2,3]
   -- True
   _Empty :: Prism' a ()
-#ifndef HLINT
   default _Empty :: (Monoid a, Eq a) => Prism' a ()
   _Empty = only mempty
   {-# INLINE _Empty #-}
-#endif
 
 #if __GLASGOW_HASKELL__ >= 710
 pattern Empty <- (has _Empty -> True) where
diff --git a/src/Control/Lens/Fold.hs b/src/Control/Lens/Fold.hs
--- a/src/Control/Lens/Fold.hs
+++ b/src/Control/Lens/Fold.hs
@@ -200,6 +200,7 @@
 {-# ANN module "HLint: ignore Eta reduce" #-}
 {-# ANN module "HLint: ignore Use camelCase" #-}
 {-# ANN module "HLint: ignore Use curry" #-}
+{-# ANN module "HLint: ignore Use fmap" #-}
 #endif
 
 infixl 8 ^.., ^?, ^?!, ^@.., ^@?, ^@?!
diff --git a/src/Control/Lens/Indexed.hs b/src/Control/Lens/Indexed.hs
--- a/src/Control/Lens/Indexed.hs
+++ b/src/Control/Lens/Indexed.hs
@@ -16,6 +16,10 @@
 {-# OPTIONS_GHC -fno-warn-redundant-constraints #-}
 #endif
 
+#ifndef MIN_VERSION_base
+#define MIN_VERSION_base(x,y,z) 1
+#endif
+
 #ifndef MIN_VERSION_containers
 #define MIN_VERSION_containers(x,y,z) 1
 #endif
@@ -116,15 +120,20 @@
 import Data.Profunctor.Unsafe
 import Data.Reflection
 import Data.Sequence hiding ((:<), index)
-#if !(MIN_VERSION_containers(0,5,0))
-import Data.Traversable (sequenceA)
-#endif
 import Data.Tree
 import Data.Tuple (swap)
 import Data.Vector (Vector)
 import qualified Data.Vector as V
 import Prelude
 
+#if !(MIN_VERSION_base(4,8,0))
+import Data.Traversable (sequenceA)
+#endif
+
+#ifdef HLINT
+{-# ANN module "HLint: ignore Use fmap" #-}
+#endif
+
 infixr 9 <.>, <., .>
 
 -- $setup
@@ -231,11 +240,9 @@
 class Functor f => FunctorWithIndex i f | f -> i where
   -- | Map with access to the index.
   imap :: (i -> a -> b) -> f a -> f b
-#ifndef HLINT
   default imap :: TraversableWithIndex i f => (i -> a -> b) -> f a -> f b
   imap = iover itraversed
   {-# INLINE imap #-}
-#endif
 
   -- | The 'IndexedSetter' for a 'FunctorWithIndex'.
   --
@@ -640,11 +647,17 @@
   {-# INLINE itraverse #-}
 
 -- | The position in the 'Seq' is available as the index.
-instance FunctorWithIndex Int Seq
-instance FoldableWithIndex Int Seq
+instance FunctorWithIndex Int Seq where
+  imap = mapWithIndex
+instance FoldableWithIndex Int Seq where
+  ifoldMap f = Data.Foldable.fold . mapWithIndex f
+  ifoldr = foldrWithIndex
+  ifoldl f = foldlWithIndex (flip f)
+  {-# INLINE ifoldl #-}
 instance TraversableWithIndex Int Seq where
-  itraversed = traversed
-  {-# INLINE itraversed #-}
+-- The next version of containers will probably offer traverseWithIndex;
+-- when that comes out, it should be used for this.
+  itraverse f = sequenceA . mapWithIndex f
 
 instance FunctorWithIndex Int Vector where
   imap = V.imap
diff --git a/src/Control/Lens/Internal/Instances.hs b/src/Control/Lens/Internal/Instances.hs
--- a/src/Control/Lens/Internal/Instances.hs
+++ b/src/Control/Lens/Internal/Instances.hs
@@ -20,21 +20,3 @@
 
 import Data.Orphans ()
 import Data.Traversable.Instances ()
-
-#if !(MIN_VERSION_semigroupoids(4,2,0))
-
-import Control.Applicative
-import Data.Semigroup.Foldable
-import Data.Semigroup.Traversable
-
--------------------------------------------------------------------------------
--- Orphan Instances
--------------------------------------------------------------------------------
-
-instance Foldable1 ((,) b) where
-  foldMap1 f (_, a) = f a
-
-instance Traversable1 ((,) b) where
-  traverse1 f (b, a) = (,) b <$> f a
-
-#endif
diff --git a/src/Control/Lens/Internal/PrismTH.hs b/src/Control/Lens/Internal/PrismTH.hs
--- a/src/Control/Lens/Internal/PrismTH.hs
+++ b/src/Control/Lens/Internal/PrismTH.hs
@@ -133,7 +133,7 @@
   convertTVBs = map (VarT . bndrName)
 
   next ty args cons =
-    makeConsPrisms (conAppsT ty args) (map normalizeCon cons) cls
+    makeConsPrisms (conAppsT ty args) (concatMap normalizeCon cons) cls
     where
     cls | normal    = Nothing
         | otherwise = Just ty
@@ -473,20 +473,22 @@
 nconTypes f x = fmap (\y -> x {_nconTypes = y}) (f (_nconTypes x))
 
 
--- | Normalize 'Con' to its constructor name and field types. For 'GadtC' and
--- 'RecGadtC', it takes the leftmost name.
-normalizeCon :: Con -> NCon
-normalizeCon (RecC    conName xs) = NCon conName Nothing (map (view _3) xs)
-normalizeCon (NormalC conName xs) = NCon conName Nothing (map (view _2) xs)
-normalizeCon (InfixC (_,x) conName (_,y)) = NCon conName Nothing [x,y]
+-- | Normalize a single 'Con' to its constructor name and field types.
+-- Because GADT syntax allows multiple constructors to be defined at
+-- the same time, this function can return multiple normalized results.
+normalizeCon :: Con -> [NCon]
+normalizeCon (RecC    conName xs) = [NCon conName Nothing (map (view _3) xs)]
+normalizeCon (NormalC conName xs) = [NCon conName Nothing (map (view _2) xs)]
+normalizeCon (InfixC (_,x) conName (_,y)) = [NCon conName Nothing [x,y]]
 normalizeCon (ForallC [] [] con) = normalizeCon con -- happens in GADTs
-normalizeCon (ForallC _ cx con) = NCon n (cx1 <> cx2) tys
-  where
-  cx1 = Just cx
-  NCon n cx2 tys = normalizeCon con
+normalizeCon (ForallC _ cx1 con) =
+  [NCon n (Just cx1 <> cx2) tys
+     | NCon n cx2 tys <- normalizeCon con ]
 #if MIN_VERSION_template_haskell(2,11,0)
-normalizeCon (GadtC conNames xs _)    = NCon (head conNames) Nothing (map (view _2) xs)
-normalizeCon (RecGadtC conNames xs _) = NCon (head conNames) Nothing (map (view _3) xs)
+normalizeCon (GadtC conNames xs _)    =
+  [ NCon conName Nothing (map (view _2) xs) | conName <- conNames ]
+normalizeCon (RecGadtC conNames xs _) =
+  [ NCon conName Nothing (map (view _3) xs) | conName <- conNames ]
 #endif
 
 -- | Compute a prism's name by prefixing an underscore for normal
diff --git a/src/Control/Lens/Plated.hs b/src/Control/Lens/Plated.hs
--- a/src/Control/Lens/Plated.hs
+++ b/src/Control/Lens/Plated.hs
@@ -218,10 +218,8 @@
   -- 'plate' will default to 'uniplate' and you can choose to not override
   -- it with your own definition.
   plate :: Traversal' a a
-#ifndef HLINT
   default plate :: Data a => Traversal' a a
   plate = uniplate
-#endif
 
 instance Plated [a] where
   plate f (x:xs) = (x:) <$> f xs
diff --git a/src/Control/Lens/Setter.hs b/src/Control/Lens/Setter.hs
--- a/src/Control/Lens/Setter.hs
+++ b/src/Control/Lens/Setter.hs
@@ -100,6 +100,7 @@
 
 #ifdef HLINT
 {-# ANN module "HLint: ignore Avoid lambda" #-}
+{-# ANN module "HLint: ignore Use fmap" #-}
 #endif
 
 -- $setup
diff --git a/src/Control/Lens/Tuple.hs b/src/Control/Lens/Tuple.hs
--- a/src/Control/Lens/Tuple.hs
+++ b/src/Control/Lens/Tuple.hs
@@ -87,12 +87,10 @@
   -- '_1' :: 'Lens' (a,b,c,d,e,f,g,h,i) (a',b,c,d,e,f,g,h,i) a a'
   -- @
   _1 :: Lens s t a b
-#ifndef HLINT
   default _1 :: (Generic s, Generic t, GIxed N0 (Rep s) (Rep t) a b)
              => Lens s t a b
   _1 = ix proxyN0
   {-# INLINE _1 #-}
-#endif
 
 instance Field1 (Identity a) (Identity b) a b where
   _1 f (Identity a) = Identity <$> f a
@@ -158,12 +156,10 @@
   -- 'Control.Lens.Fold.foldMapOf' ('Data.Traversable.traverse' '.' '_2') :: ('Data.Traversable.Traversable' t, 'Data.Monoid.Monoid' m) => (s -> m) -> t (b, s) -> m
   -- @
   _2 :: Lens s t a b
-#ifndef HLINT
   default _2 :: (Generic s, Generic t, GIxed N1 (Rep s) (Rep t) a b)
              => Lens s t a b
   _2 = ix proxyN1
   {-# INLINE _2 #-}
-#endif
 
 instance Field2 (Product f g a) (Product f g' a) (g a) (g' a) where
   _2 f (Pair a b) = Pair a <$> f b
@@ -210,12 +206,10 @@
 class Field3 s t a b | s -> a, t -> b, s b -> t, t a -> s where
   -- | Access the 3rd field of a tuple.
   _3 :: Lens s t a b
-#ifndef HLINT
   default _3 :: (Generic s, Generic t, GIxed N2 (Rep s) (Rep t) a b)
              => Lens s t a b
   _3 = ix proxyN2
   {-# INLINE _3 #-}
-#endif
 
 instance Field3 (a,b,c) (a,b,c') c c' where
   _3 k ~(a,b,c) = k c <&> \c' -> (a,b,c')
@@ -249,12 +243,10 @@
 class Field4 s t a b | s -> a, t -> b, s b -> t, t a -> s where
   -- | Access the 4th field of a tuple.
   _4 :: Lens s t a b
-#ifndef HLINT
   default _4 :: (Generic s, Generic t, GIxed N3 (Rep s) (Rep t) a b)
              => Lens s t a b
   _4 = ix proxyN3
   {-# INLINE _4 #-}
-#endif
 
 instance Field4 (a,b,c,d) (a,b,c,d') d d' where
   _4 k ~(a,b,c,d) = k d <&> \d' -> (a,b,c,d')
@@ -284,12 +276,10 @@
 class Field5 s t a b | s -> a, t -> b, s b -> t, t a -> s where
   -- | Access the 5th field of a tuple.
   _5 :: Lens s t a b
-#ifndef HLINT
   default _5 :: (Generic s, Generic t, GIxed N4 (Rep s) (Rep t) a b)
              => Lens s t a b
   _5 = ix proxyN4
   {-# INLINE _5 #-}
-#endif
 
 instance Field5 (a,b,c,d,e) (a,b,c,d,e') e e' where
   _5 k ~(a,b,c,d,e) = k e <&> \e' -> (a,b,c,d,e')
@@ -315,12 +305,10 @@
 class Field6 s t a b | s -> a, t -> b, s b -> t, t a -> s where
   -- | Access the 6th field of a tuple.
   _6 :: Lens s t a b
-#ifndef HLINT
   default _6 :: (Generic s, Generic t, GIxed N5 (Rep s) (Rep t) a b)
              => Lens s t a b
   _6 = ix proxyN5
   {-# INLINE _6 #-}
-#endif
 
 instance Field6 (a,b,c,d,e,f) (a,b,c,d,e,f') f f' where
   _6 k ~(a,b,c,d,e,f) = k f <&> \f' -> (a,b,c,d,e,f')
@@ -342,12 +330,10 @@
 class Field7 s t a b | s -> a, t -> b, s b -> t, t a -> s where
   -- | Access the 7th field of a tuple.
   _7 :: Lens s t a b
-#ifndef HLINT
   default _7 :: (Generic s, Generic t, GIxed N6 (Rep s) (Rep t) a b)
              => Lens s t a b
   _7 = ix proxyN6
   {-# INLINE _7 #-}
-#endif
 
 instance Field7 (a,b,c,d,e,f,g) (a,b,c,d,e,f,g') g g' where
   _7 k ~(a,b,c,d,e,f,g) = k g <&> \g' -> (a,b,c,d,e,f,g')
@@ -365,12 +351,10 @@
 class Field8 s t a b | s -> a, t -> b, s b -> t, t a -> s where
   -- | Access the 8th field of a tuple.
   _8 :: Lens s t a b
-#ifndef HLINT
   default _8 :: (Generic s, Generic t, GIxed N7 (Rep s) (Rep t) a b)
              => Lens s t a b
   _8 = ix proxyN7
   {-# INLINE _8 #-}
-#endif
 
 instance Field8 (a,b,c,d,e,f,g,h) (a,b,c,d,e,f,g,h') h h' where
   _8 k ~(a,b,c,d,e,f,g,h) = k h <&> \h' -> (a,b,c,d,e,f,g,h')
@@ -384,12 +368,10 @@
 class Field9 s t a b | s -> a, t -> b, s b -> t, t a -> s where
   -- | Access the 9th field of a tuple.
   _9 :: Lens s t a b
-#ifndef HLINT
   default _9 :: (Generic s, Generic t, GIxed N8 (Rep s) (Rep t) a b)
              => Lens s t a b
   _9 = ix proxyN8
   {-# INLINE _9 #-}
-#endif
 
 instance Field9 (a,b,c,d,e,f,g,h,i) (a,b,c,d,e,f,g,h,i') i i' where
   _9 k ~(a,b,c,d,e,f,g,h,i) = k i <&> \i' -> (a,b,c,d,e,f,g,h,i')
diff --git a/src/Control/Lens/Zoom.hs b/src/Control/Lens/Zoom.hs
--- a/src/Control/Lens/Zoom.hs
+++ b/src/Control/Lens/Zoom.hs
@@ -54,6 +54,10 @@
 import Data.Profunctor.Unsafe
 import Prelude
 
+#ifdef HLINT
+{-# ANN module "HLint: ignore Use fmap" #-}
+#endif
+
 -- $setup
 -- >>> import Control.Lens
 -- >>> import Control.Monad.State
diff --git a/src/Control/Monad/Error/Lens.hs b/src/Control/Monad/Error/Lens.hs
--- a/src/Control/Monad/Error/Lens.hs
+++ b/src/Control/Monad/Error/Lens.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE ExistentialQuantification #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE FlexibleInstances #-}
@@ -36,6 +37,10 @@
 import qualified Data.Monoid as M
 import Data.Semigroup (Semigroup(..))
 import Prelude
+
+#ifdef HLINT
+{-# ANN module "HLint: ignore Use fmap" #-}
+#endif
 
 ------------------------------------------------------------------------------
 -- Catching