diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,13 @@
+# 1.6.1
+
+- Use an export list in `Data.Text.Prettyprint.Doc.Internal`.
+- Improve `group` for `Union` and `FlatAlt`.
+- Speed up `removeTrailingWhitespace`.
+- Improve generating spaces for indentation and `spaces`.
+- Simplify some `Doc` constants by defining them as `Doc` literals.
+- Enable `-O2`.
+- Various documentation fixes and improvements.
+
 # 1.6.0
 
 ## Breaking changes
diff --git a/bench/LargeOutput.hs b/bench/LargeOutput.hs
--- a/bench/LargeOutput.hs
+++ b/bench/LargeOutput.hs
@@ -183,12 +183,27 @@
         (progLines, progWidth) = let l = TL.lines renderedProg in (length l, maximum (map TL.length l))
     putDoc ("Program size:" <+> pretty progLines <+> "lines, maximum width:" <+> pretty progWidth)
 
-    rnf prog `seq` T.putStrLn "Staring benchmark…"
+    let renderWith :: (Doc ann -> SimpleDocStream ann) -> Program -> TL.Text
+        renderWith f = renderLazy . f . pretty
+
+    let _80ColumnsLayoutOptions = defaultLayoutOptions { layoutPageWidth = AvailablePerLine 80 0.5 }
+        unboundedLayoutOptions  = defaultLayoutOptions { layoutPageWidth = Unbounded }
+
+    rnf prog `seq` T.putStrLn "Starting benchmark…"
+
     defaultMain
         [ bgroup "80 characters, 50% ribbon"
-            [ bench "prettyprinter" (nf (renderLazy . layoutPretty defaultLayoutOptions { layoutPageWidth = AvailablePerLine 80 0.5 } . pretty) prog)
+            [ bgroup "prettyprinter"
+                [ bench "layoutPretty"  (nf (renderWith (layoutPretty _80ColumnsLayoutOptions)) prog)
+                , bench "layoutSmart"   (nf (renderWith (layoutSmart  _80ColumnsLayoutOptions)) prog)
+                , bench "layoutCompact" (nf (renderWith layoutCompact                         ) prog)
+                ]
             , bench "ansi-wl-pprint" (nf (($ "") . WL.displayS . WL.renderPretty 0.5 80 . WL.pretty) prog) ]
         , bgroup "Infinite/large page width"
-            [ bench "prettyprinter" (nf (renderLazy . layoutPretty defaultLayoutOptions { layoutPageWidth = Unbounded } . pretty) prog)
+            [ bgroup "prettyprinter"
+                [ bench "layoutPretty"  (nf (renderWith (layoutPretty unboundedLayoutOptions)) prog)
+                , bench "layoutSmart"   (nf (renderWith (layoutSmart  unboundedLayoutOptions)) prog)
+                , bench "layoutCompact" (nf (renderWith layoutCompact                        ) prog)
+                ]
             , bench "ansi-wl-pprint" (nf (($ "") . WL.displayS . WL.renderPretty 1 (fromIntegral progWidth + 10) . WL.pretty) prog) ]
         ]
diff --git a/prettyprinter.cabal b/prettyprinter.cabal
--- a/prettyprinter.cabal
+++ b/prettyprinter.cabal
@@ -1,5 +1,5 @@
 name:                prettyprinter
-version:             1.6.0
+version:             1.6.1
 cabal-version:       >= 1.10
 category:            User Interfaces, Text
 synopsis:            A modern, easy to use, well-documented, extensible pretty-printer.
@@ -44,7 +44,7 @@
         -- Deprecated
         , Data.Text.Prettyprint.Doc.Render.ShowS
 
-    ghc-options: -Wall
+    ghc-options: -Wall -O2
     hs-source-dirs: src
     include-dirs: misc
     default-language: Haskell2010
diff --git a/src/Data/Text/Prettyprint/Doc/Internal.hs b/src/Data/Text/Prettyprint/Doc/Internal.hs
--- a/src/Data/Text/Prettyprint/Doc/Internal.hs
+++ b/src/Data/Text/Prettyprint/Doc/Internal.hs
@@ -15,10 +15,68 @@
 -- For a stable API, use the non-internal modules. For the special case of
 -- writing adaptors to this library’s @'Doc'@ type, see
 -- "Data.Text.Prettyprint.Doc.Internal.Type".
-module Data.Text.Prettyprint.Doc.Internal where
+module Data.Text.Prettyprint.Doc.Internal (
+    -- * Documents
+    Doc(..),
 
+    -- * Basic functionality
+    Pretty(..),
+    viaShow, unsafeViaShow, unsafeTextWithoutNewlines,
+    emptyDoc, nest, line, line', softline, softline', hardline, group, flatAlt,
 
+    -- * Alignment functions
+    align, hang, indent, encloseSep, list, tupled,
 
+    -- * Binary functions
+    (<+>),
+
+    -- * List functions
+    concatWith,
+
+    -- ** 'sep' family
+    hsep, vsep, fillSep, sep,
+    -- ** 'cat' family
+    hcat, vcat, fillCat, cat,
+    -- ** Others
+    punctuate,
+
+    -- * Reactive/conditional layouts
+    column, nesting, width, pageWidth,
+
+    -- * Filler functions
+    fill, fillBreak,
+
+    -- * General convenience
+    plural, enclose, surround,
+
+    -- ** Annotations
+    annotate,
+    unAnnotate,
+    reAnnotate,
+    alterAnnotations,
+    unAnnotateS,
+    reAnnotateS,
+    alterAnnotationsS,
+
+    -- * Optimization
+    fuse, FusionDepth(..),
+
+    -- * Layout
+    SimpleDocStream(..),
+    PageWidth(..), defaultPageWidth,
+    LayoutOptions(..), defaultLayoutOptions,
+    layoutPretty, layoutCompact, layoutSmart,
+    removeTrailingWhitespace,
+
+    -- * Rendering
+    renderShowS,
+
+    -- * Internal helpers
+    textSpaces
+) where
+
+
+
 import           Control.Applicative
 import           Data.Int
 import           Data.List.NonEmpty  (NonEmpty (..))
@@ -46,10 +104,6 @@
 import Prelude          hiding (foldr, foldr1)
 #endif
 
-#if !(MONOID_IN_PRELUDE)
-import Data.Monoid hiding ((<>))
-#endif
-
 #if FUNCTOR_IDENTITY_IN_BASE
 import Data.Functor.Identity
 #endif
@@ -475,7 +529,7 @@
 -- 'softline' = 'group' 'line'
 -- @
 softline :: Doc ann
-softline = group line
+softline = Union (Char ' ') Line
 
 -- | @'softline''@ is like @'softline'@, but behaves like @'mempty'@ if the
 -- resulting output does not fit on the page (instead of @'space'@). In other
@@ -497,7 +551,7 @@
 -- 'softline'' = 'group' 'line''
 -- @
 softline' :: Doc ann
-softline' = group line'
+softline' = Union mempty Line
 
 -- | A @'hardline'@ is /always/ laid out as a line break, even when 'group'ed or
 -- when there is plenty of space. Note that it might still be simply discarded
@@ -523,10 +577,16 @@
 -- use of it.
 group :: Doc ann -> Doc ann
 -- See note [Group: special flattening]
-group x = case changesUponFlattening x of
-    Flattened x' -> Union x' x
-    AlreadyFlat  -> x
-    NeverFlat    -> x
+group x = case x of
+    Union{} -> x
+    FlatAlt a b -> case changesUponFlattening b of
+        Flattened b' -> Union b' a
+        AlreadyFlat  -> Union b a
+        NeverFlat    -> a
+    _ -> case changesUponFlattening x of
+        Flattened x' -> Union x' x
+        AlreadyFlat  -> x
+        NeverFlat    -> x
 
 -- Note [Group: special flattening]
 --
@@ -1136,7 +1196,10 @@
 
 -- | Insert a number of spaces. Negative values count as 0.
 spaces :: Int -> Doc ann
-spaces n = unsafeTextWithoutNewlines (T.replicate n " ")
+spaces n
+  | n <= 0    = Empty
+  | n == 1    = Char ' '
+  | otherwise = Text n (textSpaces n)
 
 -- $
 -- prop> \(NonNegative n) -> length (show (spaces n)) == n
@@ -1481,14 +1544,16 @@
         -> Int -- Withheld spaces
         -> SimpleDocStream ann
         -> SimpleDocStream ann
-    commitWhitespace is0 n0 = commitLines is0 . commitSpaces n0
-      where
-        commitLines [] = id
-        commitLines (i:is) = foldr (\_ f -> SLine 0 . f) (SLine i) is
+    commitWhitespace is !n sds = case is of
+        []      -> case n of
+                       0 -> sds
+                       1 -> SChar ' ' sds
+                       _ -> SText n (textSpaces n) sds
+        (i:is') -> let !end = SLine (i + n) sds
+                   in prependEmptyLines is' end
 
-        commitSpaces 0 = id
-        commitSpaces 1 = SChar ' '
-        commitSpaces n = SText n (T.replicate n " ")
+    prependEmptyLines :: [Int] -> SimpleDocStream ann -> SimpleDocStream ann
+    prependEmptyLines is sds0 = foldr (\_ sds -> SLine 0 sds) sds0 is
 
     go :: WhitespaceStrippingState -> SimpleDocStream ann -> SimpleDocStream ann
     -- We do not strip whitespace inside annotated documents, since it might
@@ -1509,7 +1574,7 @@
     -- release only the necessary ones.
     go (RecordedWhitespace withheldLines withheldSpaces) = \sds -> case sds of
         SFail -> SFail
-        SEmpty -> foldr (\_i sds' -> SLine 0 sds') SEmpty withheldLines
+        SEmpty -> prependEmptyLines withheldLines SEmpty
         SChar c rest
             | c == ' ' -> go (RecordedWhitespace withheldLines (withheldSpaces+1)) rest
             | otherwise -> commitWhitespace
@@ -1543,15 +1608,7 @@
   deriving Typeable
 
 
--- | Test whether a docstream starts with a linebreak, ignoring any annotations.
-startsWithLine :: SimpleDocStream ann -> Bool
-startsWithLine sds = case sds of
-    SLine{}      -> True
-    SAnnPush _ s -> startsWithLine s
-    SAnnPop s    -> startsWithLine s
-    _            -> False
 
-
 -- $
 -- >>> import qualified Data.Text.IO as T
 -- >>> doc = "lorem" <> hardline <> hardline <> pretty "ipsum"
@@ -1704,7 +1761,7 @@
 -- >>> let hr = pipe <> pretty (replicate (26-2) '-') <> pipe
 -- >>> let go layouter x = (T.putStrLn . renderStrict . layouter (LayoutOptions (AvailablePerLine 26 1))) (vsep [hr, x, hr])
 --
--- If we render this using @'layoutPretty'@ with a page width of 26 characters
+-- If we render this using 'layoutPretty' with a page width of 26 characters
 -- per line, all the @fun@ calls fit into the first line so they will be put
 -- there,
 --
@@ -1729,22 +1786,38 @@
 --           , ghijklm ])))))
 -- |------------------------|
 --
--- The key difference between @'layoutPretty'@ and @'layoutSmart'@ is that the
--- latter will check the potential document up to the end of the current
--- indentation level, instead of just having one element lookahead.
+-- The key difference between 'layoutPretty' and 'layoutSmart' is that the
+-- latter will check the potential document until it encounters a line with the
+-- same indentation or less than the start of the document. Any line encountered
+-- earlier is assumed to belong to the same syntactic structure.
+-- 'layoutPretty' checks only the first line.
+--
+-- Consider for example the question of whether the @A@s fit into the document
+-- below:
+--
+-- > 1 A
+-- > 2   A
+-- > 3  A
+-- > 4 B
+-- > 5   B
+--
+-- 'layoutPretty' will check only line 1, ignoring whether e.g. line 2 might
+-- already be too wide.
+-- By contrast, 'layoutSmart' stops only once it reaches line 4, where the @B@
+-- has the same indentation as the first @A@.
 layoutSmart
     :: LayoutOptions
     -> Doc ann
     -> SimpleDocStream ann
 layoutSmart = layoutWadlerLeijen (FittingPredicate fits)
   where
-    -- Search with more lookahead: assuming that nesting roughly corresponds to
-    -- syntactic depth, @fits@ checks that not only the current line fits, but
-    -- the entire syntactic structure being formatted at this level of
-    -- indentation fits. If we were to remove the second case for @SLine@, we
-    -- would check that not only the current structure fits, but also the rest
-    -- of the document, which would be slightly more intelligent but would have
-    -- exponential runtime (and is prohibitively expensive in practice).
+    -- Why doesn't layoutSmart simply check the entire document?
+    --
+    -- 1. That would be very expensive.
+    -- 2. In that case the layout of a particular part of a document would
+    --    depend on the fit of completely unrelated parts of the same document.
+    --    See https://github.com/quchen/prettyprinter/issues/83 for a related
+    --    bug.
     fits :: PageWidth
          -> Int -- ^ Minimum nesting level to fit in
          -> Int -- ^ Width in which to fit the first line
@@ -1800,26 +1873,37 @@
         Nesting f       -> best nl cc (Cons i (f i) ds)
         Annotated ann x -> SAnnPush ann (best nl cc (Cons i x (UndoAnn ds)))
 
+    -- Select the better fitting of two documents:
+    -- Choice A if it fits, otherwise choice B.
+    --
+    -- The fit of choice B is /not/ checked! It is ultimately the user's
+    -- responsibility to provide an alternative that can fit the page even when
+    -- choice A doesn't.
     selectNicer
         :: Int           -- ^ Current nesting level
         -> Int           -- ^ Current column
-        -> SimpleDocStream ann -- ^ Choice A. Invariant: first lines should not be longer than B's.
-        -> SimpleDocStream ann -- ^ Choice B.
+        -> SimpleDocStream ann -- ^ Choice A.
+        -> SimpleDocStream ann -- ^ Choice B. Should fit more easily
+                               --   (== be less wide) than choice A.
         -> SimpleDocStream ann -- ^ Choice A if it fits, otherwise B.
     selectNicer lineIndent currentColumn x y = case pWidth of
         AvailablePerLine lineLength ribbonFraction
           | fits pWidth minNestingLevel availableWidth x -> x
           where
             minNestingLevel =
-                -- See https://github.com/quchen/prettyprinter/issues/83.
-                if startsWithLine y
-                    -- y might be a (more compact) hanging layout. Let's check x
-                    -- thoroughly with the smaller lineIndent.
-                    then lineIndent
-                    -- y definitely isn't a hanging layout. Let's allow the first
-                    -- line of x to be checked on its own and format it consistently
-                    -- with subsequent lines with the same indentation.
-                    else currentColumn
+                -- See the Note
+                -- [Choosing the right minNestingLevel for consistent smart layouts]
+                case initialIndentation y of
+                    Just i ->
+                        -- y could be a (less wide) hanging layout. If so, let's
+                        -- check x a bit more thoroughly so we don't miss a potentially
+                        -- better fitting y.
+                        min i currentColumn
+                    Nothing ->
+                        -- y definitely isn't a hanging layout. Let's check x with the
+                        -- same minNestingLevel that any subsequent lines with the same
+                        -- indentation use.
+                        currentColumn
             availableWidth = min columnsLeftInLine columnsLeftInRibbon
               where
                 columnsLeftInLine = lineLength - currentColumn
@@ -1832,6 +1916,13 @@
           | not (failsOnFirstLine x) -> x
         _ -> y
 
+    initialIndentation :: SimpleDocStream ann -> Maybe Int
+    initialIndentation sds = case sds of
+        SLine i _    -> Just i
+        SAnnPush _ s -> initialIndentation s
+        SAnnPop s    -> initialIndentation s
+        _            -> Nothing
+
     failsOnFirstLine :: SimpleDocStream ann -> Bool
     failsOnFirstLine = go
       where
@@ -1845,23 +1936,120 @@
             SAnnPop s    -> go s
 
 
--- Note [Detecting failure with Unbounded page width]
---
--- To understand why it is sufficient to check the first line of the
--- SimpleDocStream, trace how an SFail ends up there:
---
--- 1. We group a Doc containing a Line, producing a (Union x y) where
---    x contains Fail.
---
--- 2. In best, any Unions are handled recursively, rejecting any
---    alternatives that would result in SFail.
---
--- So once a SimpleDocStream reaches selectNicer, any SFail in it must
--- appear before the first linebreak – any other SFail would have been
--- detected and rejected in a previous iteration.
+{- Note [Choosing the right minNestingLevel for consistent smart layouts]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider this document:
 
+    doc =
+            "Groceries: "
+        <>  align
+                (cat
+                    [ sep ["pommes", "de", "terre"]
+                    , "apples"
+                    , "Donaudampfschifffahrtskapitänskajütenmülleimer"
+                    ]
+                )
 
+... and assume we want to fit it into 40 columns as nicely as possible:
 
+    opts = LayoutOptions (AvailablePerLine 40 1)
+
+We already have bad luck with the last item – it's longer than 40 characters
+on its own!
+
+We'd still like the first item, pommes de terre, to be laid out nicely, that is,
+on one line, since it's not too wide. This is what we'd like to see:
+
+    Groceries: pommes de terre
+               apples
+               Donaudampfschifffahrtskapitänskajütenmülleimer
+
+Before #83 was fixed, that wasn't what we got! Instead we got this:
+
+> renderIO stdout $ layoutSmart opts doc
+Groceries: pommes
+           de
+           terre
+           apples
+           Donaudampfschifffahrtskapitänskajütenmülleimer
+
+Why?
+
+minNestingLevel was effectively defined as
+
+    minNestingLevel = lineIndent
+
+The lineIndent for "pommes de terre" is 0.
+
+The FittingPredicate for layoutSmart will continue to check the rest of the
+document until it finds a line where the indentation <= minNestingLevel.
+In this case this meant that layoutSmart would traverse all the items,
+and note that the last item, Donaudampfschifffahrtskapitänskajütenmülleimer,
+doesn't fit into the available space! The "flatter" version of the document
+has failed, so "pommes de terre" gets spread over several lines!
+
+Obviously this would be an inconsistency with the layout of the other items.
+Their lineIndent is 11 each, so for them, the FittingPredicate stops already
+on the next line.
+
+The obvious solution is to change the definition of minNestingLevel:
+
+    minNestingLevel = currentColumn
+
+This however breaks the "python-ish" document from the documentation for
+layoutSmart:
+
+    expected: |------------------------|
+              fun(
+                fun(
+                  fun(
+                    fun(
+                      fun(
+                        [ abcdef
+                        , ghijklm ])))))
+              |------------------------|
+
+     but got: |------------------------|
+              fun(
+                fun(
+                  fun(
+                    fun(
+                      fun([ abcdef
+                          , ghijklm ])))))
+              |------------------------|
+
+We now accept the worse layout because the problematic last line has
+the same indentation as the current column of "[ abcdef", so we don't check it!
+
+The solution we went with in the end is a bit of a hack:
+
+We check whether the alternative, "high" layout is a (potentially less wide)
+hanging layout, and in that case pick its indentation as the minNestingLevel.
+
+This way we achieve the optimal layout in both scenarios.
+
+See https://github.com/quchen/prettyprinter/issues/83 for the bug that lead
+to the current solution.
+
+
+Note [Detecting failure with Unbounded page width]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+To understand why it is sufficient to check the first line of the
+SimpleDocStream, trace how an SFail ends up there:
+
+1. We group a Doc containing a Line, producing a (Union x y) where
+   x contains Fail.
+
+2. In best, any Unions are handled recursively, rejecting any
+   alternatives that would result in SFail.
+
+So once a SimpleDocStream reaches selectNicer, any SFail in it must
+appear before the first linebreak – any other SFail would have been
+detected and rejected in a previous iteration.
+-}
+
+
+
 -- | @(layoutCompact x)@ lays out the document @x@ without adding any
 -- indentation. Since no \'pretty\' printing is involved, this layouter is very
 -- fast. The resulting output contains fewer characters than a prettyprinted
@@ -1920,6 +2108,20 @@
     SLine i x    -> showString ('\n' : replicate i ' ') . renderShowS x
     SAnnPush _ x -> renderShowS x
     SAnnPop x    -> renderShowS x
+
+
+-- | A utility for producing indentation etc.
+--
+-- >>> textSpaces 3
+-- "   "
+--
+-- This produces much better Core than the equivalent
+--
+-- > T.replicate n " "
+--
+-- (See <https://github.com/quchen/prettyprinter/issues/131>.)
+textSpaces :: Int -> Text
+textSpaces n = T.replicate n (T.singleton ' ')
 
 
 -- $setup
diff --git a/src/Data/Text/Prettyprint/Doc/Internal/Debug.hs b/src/Data/Text/Prettyprint/Doc/Internal/Debug.hs
--- a/src/Data/Text/Prettyprint/Doc/Internal/Debug.hs
+++ b/src/Data/Text/Prettyprint/Doc/Internal/Debug.hs
@@ -7,19 +7,19 @@
 -- Use the @pretty-simple@ package to get a nicer layout for 'show'n
 -- 'Diag's:
 --
--- >>> Text.Pretty.Simple.pPrintNoColor . diag $ align (vcat ["foo", "bar"])
--- Column
---    [
---        ( 10
---        , Nesting
---            [
---                ( 10
---                , Cat ( Text 3 "foo" )
---                    ( Cat ( FlatAlt Line Empty ) ( Text 3 "bar" ) )
---                )
---            ]
---        )
---    ]
+-- > > Text.Pretty.Simple.pPrintNoColor . diag $ align (vcat ["foo", "bar"])
+-- > Column
+-- >    [
+-- >        ( 10
+-- >        , Nesting
+-- >            [
+-- >                ( 10
+-- >                , Cat ( Text 3 "foo" )
+-- >                    ( Cat ( FlatAlt Line Empty ) ( Text 3 "bar" ) )
+-- >                )
+-- >            ]
+-- >        )
+-- >    ]
 
 
 module Data.Text.Prettyprint.Doc.Internal.Debug where
@@ -59,7 +59,7 @@
 --
 -- Use `diag'` to control the function inputs yourself.
 --
--- >>> diag $ align (vcat ["foo", "bar"])
+-- >>> diag $ Doc.align (Doc.vcat ["foo", "bar"])
 -- Column [(10,Nesting [(10,Cat (Text 3 "foo") (Cat (FlatAlt Line Empty) (Text 3 "bar")))])]
 diag :: Doc ann -> Diag ann
 diag = diag' [10] [Doc.defaultPageWidth] [10]
diff --git a/src/Data/Text/Prettyprint/Doc/Render/Text.hs b/src/Data/Text/Prettyprint/Doc/Render/Text.hs
--- a/src/Data/Text/Prettyprint/Doc/Render/Text.hs
+++ b/src/Data/Text/Prettyprint/Doc/Render/Text.hs
@@ -18,13 +18,13 @@
 
 
 import           Data.Text              (Text)
-import qualified Data.Text              as T
 import qualified Data.Text.IO           as T
 import qualified Data.Text.Lazy         as TL
 import qualified Data.Text.Lazy.Builder as TLB
 import           System.IO
 
 import Data.Text.Prettyprint.Doc
+import Data.Text.Prettyprint.Doc.Internal
 import Data.Text.Prettyprint.Doc.Render.Util.Panic
 import Data.Text.Prettyprint.Doc.Render.Util.StackMachine
 
@@ -86,7 +86,7 @@
         SText _ t rest     -> do T.hPutStr h t
                                  go rest
         SLine n rest       -> do hPutChar h '\n'
-                                 T.hPutStr h (T.replicate n " ")
+                                 T.hPutStr h (textSpaces n)
                                  go rest
         SAnnPush _ann rest -> go rest
         SAnnPop rest       -> go rest
diff --git a/src/Data/Text/Prettyprint/Doc/Render/Tutorials/StackMachineTutorial.hs b/src/Data/Text/Prettyprint/Doc/Render/Tutorials/StackMachineTutorial.hs
--- a/src/Data/Text/Prettyprint/Doc/Render/Tutorials/StackMachineTutorial.hs
+++ b/src/Data/Text/Prettyprint/Doc/Render/Tutorials/StackMachineTutorial.hs
@@ -20,11 +20,11 @@
     {-# DEPRECATED "Writing your own stack machine is probably more efficient and customizable; also consider using »renderSimplyDecorated(A)« instead" #-}
     where
 
-import qualified Data.Text              as T
 import qualified Data.Text.Lazy         as TL
 import qualified Data.Text.Lazy.Builder as TLB
 
 import Data.Text.Prettyprint.Doc
+import Data.Text.Prettyprint.Doc.Internal
 import Data.Text.Prettyprint.Doc.Render.Util.Panic
 import Data.Text.Prettyprint.Doc.Render.Util.StackMachine
 
@@ -92,7 +92,7 @@
         renderStackMachine x
     SLine i x -> do
         writeOutput (TLB.singleton '\n')
-        writeOutput (TLB.fromText (T.replicate i " "))
+        writeOutput (TLB.fromText (textSpaces i))
         renderStackMachine x
     SAnnPush s x -> do
         pushStyle s
diff --git a/src/Data/Text/Prettyprint/Doc/Render/Tutorials/TreeRenderingTutorial.hs b/src/Data/Text/Prettyprint/Doc/Render/Tutorials/TreeRenderingTutorial.hs
--- a/src/Data/Text/Prettyprint/Doc/Render/Tutorials/TreeRenderingTutorial.hs
+++ b/src/Data/Text/Prettyprint/Doc/Render/Tutorials/TreeRenderingTutorial.hs
@@ -15,11 +15,11 @@
 -- source form.
 module Data.Text.Prettyprint.Doc.Render.Tutorials.TreeRenderingTutorial where
 
-import qualified Data.Text              as T
 import qualified Data.Text.Lazy         as TL
 import qualified Data.Text.Lazy.Builder as TLB
 
 import Data.Text.Prettyprint.Doc
+import Data.Text.Prettyprint.Doc.Internal
 import Data.Text.Prettyprint.Doc.Render.Util.SimpleDocTree
 
 #if !(FOLDABLE_TRAVERSABLE_IN_PRELUDE)
@@ -87,7 +87,7 @@
     STEmpty -> mempty
     STChar c -> TLB.singleton c
     STText _ t -> TLB.fromText t
-    STLine i -> "\n" <> TLB.fromText (T.replicate i " ")
+    STLine i -> "\n" <> TLB.fromText (textSpaces i)
     STAnn ann content -> encloseInTagFor ann (renderTree content)
     STConcat contents -> foldMap renderTree contents
 
diff --git a/src/Data/Text/Prettyprint/Doc/Render/Util/SimpleDocTree.hs b/src/Data/Text/Prettyprint/Doc/Render/Util/SimpleDocTree.hs
--- a/src/Data/Text/Prettyprint/Doc/Render/Util/SimpleDocTree.hs
+++ b/src/Data/Text/Prettyprint/Doc/Render/Util/SimpleDocTree.hs
@@ -32,6 +32,7 @@
 import           GHC.Generics
 
 import Data.Text.Prettyprint.Doc
+import Data.Text.Prettyprint.Doc.Internal
 import Data.Text.Prettyprint.Doc.Render.Util.Panic
 
 import qualified Control.Monad.Fail as Fail
@@ -75,7 +76,7 @@
         STEmpty        -> mempty
         STChar c       -> text (T.singleton c)
         STText _ t     -> text t
-        STLine i       -> text (T.singleton '\n' <> T.replicate i " ")
+        STLine i       -> text (T.singleton '\n') `mappend` text (textSpaces i)
         STAnn ann rest -> renderAnn ann (go rest)
         STConcat xs    -> foldMap go xs
 {-# INLINE renderSimplyDecorated #-}
@@ -93,7 +94,7 @@
         STEmpty        -> pure mempty
         STChar c       -> text (T.singleton c)
         STText _ t     -> text t
-        STLine i       -> text (T.singleton '\n' <> T.replicate i " ")
+        STLine i       -> text (T.cons '\n' (textSpaces i))
         STAnn ann rest -> renderAnn ann (go rest)
         STConcat xs    -> fmap mconcat (traverse go xs)
 {-# INLINE renderSimplyDecoratedA #-}
diff --git a/src/Data/Text/Prettyprint/Doc/Render/Util/StackMachine.hs b/src/Data/Text/Prettyprint/Doc/Render/Util/StackMachine.hs
--- a/src/Data/Text/Prettyprint/Doc/Render/Util/StackMachine.hs
+++ b/src/Data/Text/Prettyprint/Doc/Render/Util/StackMachine.hs
@@ -1,6 +1,5 @@
 {-# LANGUAGE BangPatterns      #-}
 {-# LANGUAGE CPP               #-}
-{-# LANGUAGE OverloadedStrings #-}
 
 #include "version-compatibility-macros.h"
 
@@ -36,7 +35,7 @@
 import           Data.Text           (Text)
 import qualified Data.Text           as T
 
-import Data.Text.Prettyprint.Doc                   (SimpleDocStream (..))
+import Data.Text.Prettyprint.Doc.Internal
 import Data.Text.Prettyprint.Doc.Render.Util.Panic
 
 #if !(SEMIGROUP_MONOID_SUPERCLASS)
@@ -78,7 +77,7 @@
     go (_:_)       SEmpty              = panicInputNotFullyConsumed
     go stack       (SChar c rest)      = text (T.singleton c) <> go stack rest
     go stack       (SText _l t rest)   = text t <> go stack rest
-    go stack       (SLine i rest)      = text (T.singleton '\n') <> text (T.replicate i " ") <> go stack rest
+    go stack       (SLine i rest)      = text (T.singleton '\n') <> text (textSpaces i) <> go stack rest
     go stack       (SAnnPush ann rest) = push ann <> go (ann : stack) rest
     go (ann:stack) (SAnnPop rest)      = pop ann <> go stack rest
     go []          SAnnPop{}           = panicUnpairedPop
@@ -99,7 +98,7 @@
     go (_:_)       SEmpty              = panicInputNotFullyConsumed
     go stack       (SChar c rest)      = text (T.singleton c) <++> go stack rest
     go stack       (SText _l t rest)   = text t <++> go stack rest
-    go stack       (SLine i rest)      = text (T.singleton '\n') <++> text (T.replicate i " ") <++> go stack rest
+    go stack       (SLine i rest)      = text (T.singleton '\n') <++> text (textSpaces i) <++> go stack rest
     go stack       (SAnnPush ann rest) = push ann <++> go (ann : stack) rest
     go (ann:stack) (SAnnPop rest)      = pop ann <++> go stack rest
     go []          SAnnPop{}           = panicUnpairedPop
diff --git a/src/Data/Text/Prettyprint/Doc/Symbols/Ascii.hs b/src/Data/Text/Prettyprint/Doc/Symbols/Ascii.hs
--- a/src/Data/Text/Prettyprint/Doc/Symbols/Ascii.hs
+++ b/src/Data/Text/Prettyprint/Doc/Symbols/Ascii.hs
@@ -46,65 +46,65 @@
 -- | >>> squote
 -- '
 squote :: Doc ann
-squote = "'"
+squote = Char '\''
 
 -- | >>> dquote
 -- "
 dquote :: Doc ann
-dquote = "\""
+dquote = Char '"'
 
 -- | >>> lparen
 -- (
 lparen :: Doc ann
-lparen = "("
+lparen = Char '('
 
 -- | >>> rparen
 -- )
 rparen :: Doc ann
-rparen = ")"
+rparen = Char ')'
 
 -- | >>> langle
 -- <
 langle :: Doc ann
-langle = "<"
+langle = Char '<'
 
 -- | >>> rangle
 -- >
 rangle :: Doc ann
-rangle = ">"
+rangle = Char '>'
 
 -- | >>> lbracket
 -- [
 lbracket :: Doc ann
-lbracket = "["
+lbracket = Char '['
 -- | >>> rbracket
 -- ]
 rbracket :: Doc ann
-rbracket = "]"
+rbracket = Char ']'
 
 -- | >>> lbrace
 -- {
 lbrace :: Doc ann
-lbrace = "{"
+lbrace = Char '{'
 -- | >>> rbrace
 -- }
 rbrace :: Doc ann
-rbrace = "}"
+rbrace = Char '}'
 
 -- | >>> semi
 -- ;
 semi :: Doc ann
-semi = ";"
+semi = Char ';'
 
 -- | >>> colon
 -- :
 colon :: Doc ann
-colon = ":"
+colon = Char ':'
 
 -- | >>> comma
 -- ,
 comma :: Doc ann
-comma = ","
+comma = Char ','
 
 -- | >>> "a" <> space <> "b"
 -- a b
@@ -114,17 +114,17 @@
 -- >>> "a" <+> "b"
 -- a b
 space :: Doc ann
-space = " "
+space = Char ' '
 
 -- | >>> dot
 -- .
 dot :: Doc ann
-dot = "."
+dot = Char '.'
 
 -- | >>> slash
 -- /
 slash :: Doc ann
-slash = "/"
+slash = Char '/'
 
 -- | >>> backslash
 -- \\
@@ -135,12 +135,12 @@
 -- | >>> equals
 -- =
 equals :: Doc ann
-equals = "="
+equals = Char '='
 
 -- | >>> pipe
 -- |
 pipe :: Doc ann
-pipe = "|"
+pipe = Char '|'
 
 
 
diff --git a/src/Data/Text/Prettyprint/Doc/Symbols/Unicode.hs b/src/Data/Text/Prettyprint/Doc/Symbols/Unicode.hs
--- a/src/Data/Text/Prettyprint/Doc/Symbols/Unicode.hs
+++ b/src/Data/Text/Prettyprint/Doc/Symbols/Unicode.hs
@@ -1,5 +1,3 @@
-{-# LANGUAGE OverloadedStrings #-}
-
 -- | A collection of predefined Unicode values outside of ASCII range. For
 -- ASCII, see "Data.Text.Prettyprint.Doc.Symbols.Ascii".
 module Data.Text.Prettyprint.Doc.Symbols.Unicode (
@@ -41,7 +39,7 @@
 
 
 
-import Data.Text.Prettyprint.Doc
+import Data.Text.Prettyprint.Doc.Internal
 
 
 
@@ -106,100 +104,100 @@
 -- >>> putDoc b99dquote
 -- „
 b99dquote :: Doc ann
-b99dquote = "„"
+b99dquote = Char '„'
 
 -- | Top “66” style double quotes.
 --
 -- >>> putDoc t66dquote
 -- “
 t66dquote :: Doc ann
-t66dquote = "“"
+t66dquote = Char '“'
 
 -- | Top “99” style double quotes.
 --
 -- >>> putDoc t99dquote
 -- ”
 t99dquote :: Doc ann
-t99dquote = "”"
+t99dquote = Char '”'
 
 -- | Bottom ‚9‘ style single quote.
 --
 -- >>> putDoc b9quote
 -- ‚
 b9quote :: Doc ann
-b9quote = "‚"
+b9quote = Char '‚'
 
 -- | Top ‘66’ style single quote.
 --
 -- >>> putDoc t6quote
 -- ‘
 t6quote :: Doc ann
-t6quote = "‘"
+t6quote = Char '‘'
 
 -- | Top ‘9’ style single quote.
 --
 -- >>> putDoc t9quote
 -- ’
 t9quote :: Doc ann
-t9quote = "’"
+t9quote = Char '’'
 
 -- | Right-pointing double guillemets
 --
 -- >>> putDoc rdGuillemet
 -- »
 rdGuillemet :: Doc ann
-rdGuillemet = "»"
+rdGuillemet = Char '»'
 
 -- | Left-pointing double guillemets
 --
 -- >>> putDoc ldGuillemet
 -- «
 ldGuillemet :: Doc ann
-ldGuillemet = "«"
+ldGuillemet = Char '«'
 
 -- | Right-pointing single guillemets
 --
 -- >>> putDoc rsGuillemet
 -- ›
 rsGuillemet :: Doc ann
-rsGuillemet = "›"
+rsGuillemet = Char '›'
 
 -- | Left-pointing single guillemets
 --
 -- >>> putDoc lsGuillemet
 -- ‹
 lsGuillemet :: Doc ann
-lsGuillemet = "‹"
+lsGuillemet = Char '‹'
 
 -- | >>> putDoc bullet
 -- •
 bullet :: Doc ann
-bullet = "•"
+bullet = Char '•'
 
 -- | >>> putDoc endash
 -- –
 endash :: Doc ann
-endash = "–"
+endash = Char '–'
 
 -- | >>> putDoc euro
 -- €
 euro :: Doc ann
-euro = "€"
+euro = Char '€'
 
 -- | >>> putDoc cent
 -- ¢
 cent :: Doc ann
-cent = "¢"
+cent = Char '¢'
 
 -- | >>> putDoc yen
 -- ¥
 yen :: Doc ann
-yen = "¥"
+yen = Char '¥'
 
 -- | >>> putDoc pound
 -- £
 pound :: Doc ann
-pound = "£"
+pound = Char '£'
 
 
 
diff --git a/test/Testsuite/Main.hs b/test/Testsuite/Main.hs
--- a/test/Testsuite/Main.hs
+++ b/test/Testsuite/Main.hs
@@ -1,6 +1,6 @@
 {-# LANGUAGE CPP               #-}
 {-# LANGUAGE OverloadedStrings #-}
-{-# OPTIONS_GHC -Wno-orphans   #-}
+{-# OPTIONS_GHC -fno-warn-orphans   #-}
 
 #include "version-compatibility-macros.h"
 
@@ -16,7 +16,6 @@
 import           System.Timeout        (timeout)
 
 import           Data.Text.Prettyprint.Doc
-import           Data.Text.Prettyprint.Doc.Internal
 import           Data.Text.Prettyprint.Doc.Internal.Debug
 import           Data.Text.Prettyprint.Doc.Render.Text
 import           Data.Text.Prettyprint.Doc.Render.Util.StackMachine (renderSimplyDecorated)
@@ -199,12 +198,9 @@
     = LayoutPretty LayoutOptions
     | LayoutSmart LayoutOptions
     | LayoutCompact
-    | LayoutWadlerLeijen (FittingPredicate ann) LayoutOptions
+    -- LayoutWadlerLeijen (FittingPredicate ann) LayoutOptions
     deriving Show
 
-instance Show (FittingPredicate ann) where
-    show _ = "<fitting predicate>"
-
 instance Arbitrary (Layouter ann) where
     arbitrary = oneof
         [ LayoutPretty <$> arbitrary
@@ -214,11 +210,19 @@
         -- , LayoutWadlerLeijen <$> arbitrary <*> arbitrary
         ]
 
+{-
+instance Show (FittingPredicate ann) where
+    show _ = "<fitting predicate>"
+
+instance Arbitrary (FittingPredicate ann) where
+    arbitrary = FittingPredicate <$> arbitrary
+-}
+
 layout :: Layouter ann -> Doc ann -> SimpleDocStream ann
 layout (LayoutPretty opts) = layoutPretty opts
 layout (LayoutSmart opts) = layoutSmart opts
 layout LayoutCompact = layoutCompact
-layout (LayoutWadlerLeijen fp opts) = layoutWadlerLeijen fp opts
+-- layout (LayoutWadlerLeijen fp opts) = layoutWadlerLeijen fp opts
 
 instance Arbitrary LayoutOptions where
     arbitrary = LayoutOptions <$> oneof
@@ -226,9 +230,6 @@
         , pure Unbounded
         ]
 
-instance Arbitrary (FittingPredicate ann) where
-    arbitrary = FittingPredicate <$> arbitrary
-
 instance CoArbitrary (SimpleDocStream ann) where
     coarbitrary s0 = case s0 of
         SFail         -> variant' 0
@@ -302,19 +303,21 @@
 doNotRemoveLeadingWhitespaceText
   = let sdoc :: SimpleDocStream ()
         sdoc = SLine 0 (SText 2 "  " (SChar 'x' SEmpty))
-    in assertEqual "" sdoc (removeTrailingWhitespace sdoc)
+        sdoc' = SLine 2 (SChar 'x' SEmpty)
+    in assertEqual "" sdoc' (removeTrailingWhitespace sdoc)
 
 doNotRemoveLeadingWhitespaceChar :: Assertion
 doNotRemoveLeadingWhitespaceChar
   = let sdoc :: SimpleDocStream ()
         sdoc = SLine 0 (SChar ' ' (SChar 'x' SEmpty))
-    in assertEqual "" sdoc (removeTrailingWhitespace sdoc)
+        sdoc' = SLine 1 (SChar 'x' SEmpty)
+    in assertEqual "" sdoc' (removeTrailingWhitespace sdoc)
 
 doNotRemoveLeadingWhitespaceTextChar :: Assertion
 doNotRemoveLeadingWhitespaceTextChar
   = let sdoc :: SimpleDocStream ()
         sdoc = SLine 0 (SChar ' ' (SText 2 "  " (SChar 'x' SEmpty)))
-        sdoc' = SLine 0 (SText 3 "   " (SChar 'x' SEmpty))
+        sdoc' = SLine 3 (SChar 'x' SEmpty)
     in assertEqual "" sdoc' (removeTrailingWhitespace sdoc)
 
 removeTrailingWhitespaceKeepTrailingNewline :: Assertion