Replace calls to `ptext . sLit` with `text`

Summary:
In the past the canonical way for constructing an SDoc string literal was the
composition `ptext . sLit`.  But for some time now we have function `text` that
does the same.  Plus it has some rules that optimize its runtime behaviour.
This patch takes all uses of `ptext . sLit` in the compiler and replaces them
with calls to `text`.  The main benefits of this patch are clener (shorter) code
and less dependencies between module, because many modules now do not need to
import `FastString`.  I don't expect any performance benefits - we mostly use
SDocs to report errors and it seems there is little to be gained here.

Test Plan: ./validate

Reviewers: bgamari, austin, goldfire, hvr, alanz

Subscribers: goldfire, thomie, mpickering

Differential Revision: https://phabricator.haskell.org/D1784

4 files changed, 14 insertions, 13 deletions

diff --git a/compiler/vectorise/Vectorise/Builtins/Initialise.hs b/compiler/vectorise/Vectorise/Builtins/Initialise.hs
index 21de8dcb8b..69e00a0411 100644
--- a/compiler/vectorise/Vectorise/Builtins/Initialise.hs
+++ b/compiler/vectorise/Vectorise/Builtins/Initialise.hs
@@ -226,7 +226,7 @@ externalClass fs
   = do { tycon <- dsLookupDPHRdrEnv (mkClsOccFS fs) >>= dsLookupTyCon
        ; case tyConClass_maybe tycon of
            Nothing  -> pprPanic "Vectorise.Builtins.Initialise" $
-                         ptext (sLit "Data.Array.Parallel.Prim.") <>
-                         ftext fs <+> ptext (sLit "is not a type class")
+                         text "Data.Array.Parallel.Prim." <>
+                         ftext fs <+> text "is not a type class"
            Just cls -> return cls
        }
diff --git a/compiler/vectorise/Vectorise/Exp.hs b/compiler/vectorise/Vectorise/Exp.hs
index fd1db9a7f8..5f283c6d3a 100644
--- a/compiler/vectorise/Vectorise/Exp.hs
+++ b/compiler/vectorise/Vectorise/Exp.hs
@@ -592,7 +592,7 @@ vectDictExpr (Case e bndr ty alts)
     --
     vectDictAltCon (DataAlt datacon) = DataAlt <$> maybeV dataConErr (lookupDataCon datacon)
       where
-        dataConErr = ptext (sLit "Cannot vectorise data constructor:") <+> ppr datacon
+        dataConErr = text "Cannot vectorise data constructor:" <+> ppr datacon
     vectDictAltCon (LitAlt lit)      = return $ LitAlt lit
     vectDictAltCon DEFAULT           = return DEFAULT
 vectDictExpr (Let bnd body)
@@ -637,7 +637,8 @@ mkScalarFun arg_tys res_ty expr
        ; return (vExpr, unused)
        }
   | otherwise
-  = do { traceVt "mkScalarFun: " $ ppr expr $$ ptext (sLit "  ::") <+> ppr (mkFunTys arg_tys res_ty)
+  = do { traceVt "mkScalarFun: " $ ppr expr $$ text "  ::" <+>
+                                   ppr (mkFunTys arg_tys res_ty)
 
        ; fn_var  <- hoistExpr (fsLit "fn") expr DontInline
        ; zipf    <- zipScalars arg_tys res_ty
diff --git a/compiler/vectorise/Vectorise/Monad/Global.hs b/compiler/vectorise/Vectorise/Monad/Global.hs
index 2ad0059596..0d3e0c0c91 100644
--- a/compiler/vectorise/Vectorise/Monad/Global.hs
+++ b/compiler/vectorise/Vectorise/Monad/Global.hs
@@ -47,7 +47,6 @@ import Name
 import VarEnv
 import VarSet
 import Var as Var
-import FastString
 import Outputable
 
 
@@ -100,11 +99,11 @@ defGlobalVar v v'
        }
   where
     moduleOf var var' | var == var'
-                      = ptext (sLit "vectorises to itself")
+                      = text "vectorises to itself"
                       | Just mod <- nameModule_maybe (Var.varName var')
-                      = ptext (sLit "in module") <+> ppr mod
+                      = text "in module" <+> ppr mod
                       | otherwise
-                      = ptext (sLit "in the current module")
+                      = text "in the current module"
 
 -- |Remove the mapping of a variable in the vectorisation map.
 --
@@ -180,11 +179,11 @@ defTyConName tc nameOfTc' tc'
        }
   where
     moduleOf tc tc' | tc == tc'
-                    = ptext (sLit "vectorises to itself")
+                    = text "vectorises to itself"
                     | Just mod <- nameModule_maybe (tyConName tc')
-                    = ptext (sLit "in module") <+> ppr mod
+                    = text "in module" <+> ppr mod
                     | otherwise
-                    = ptext (sLit "in the current module")
+                    = text "in the current module"
 
 -- |Add a mapping between plain and vectorised `TyCon`s to the global environment.
 --
diff --git a/compiler/vectorise/Vectorise/Type/Env.hs b/compiler/vectorise/Vectorise/Type/Env.hs
index e4b538ac34..7b00a5c1ef 100644
--- a/compiler/vectorise/Vectorise/Type/Env.hs
+++ b/compiler/vectorise/Vectorise/Type/Env.hs
@@ -232,8 +232,9 @@ vectTypeEnv tycons vectTypeDecls vectClassDecls
        ; traceVt " convert        : " $ ppr conv_tcs
 
            -- warn the user about unvectorised type constructors
-       ; let explanation    = ptext (sLit "(They use unsupported language extensions") $$
-                              ptext (sLit "or depend on type constructors that are not vectorised)")
+       ; let explanation    = text "(They use unsupported language extensions"
+                          $$  text "or depend on type constructors that are" <+>
+                              text "not vectorised)"
              drop_tcs_nosyn = filter (not . isTypeFamilyTyCon) .
                               filter (not . isTypeSynonymTyCon) $ drop_tcs
        ; unless (null drop_tcs_nosyn) $