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

1 files changed, 3 insertions, 4 deletions

diff --git a/compiler/main/ErrUtils.hs b/compiler/main/ErrUtils.hs
index 11b30fd13c..eafe4e802f 100644
--- a/compiler/main/ErrUtils.hs
+++ b/compiler/main/ErrUtils.hs
@@ -53,7 +53,6 @@ import Bag
 import Exception
 import Outputable
 import Panic
-import FastString
 import SrcLoc
 import DynFlags
 
@@ -174,9 +173,9 @@ mkLocMessage severity locn msg
     -- Add prefixes, like    Foo.hs:34: warning:
     --                           <the warning message>
     sev_info = case severity of
-                 SevWarning -> ptext (sLit "warning:")
-                 SevError -> ptext (sLit "error:")
-                 SevFatal -> ptext (sLit "fatal:")
+                 SevWarning -> text "warning:"
+                 SevError -> text "error:"
+                 SevFatal -> text "fatal:"
                  _ -> empty
 
 makeIntoWarning :: ErrMsg -> ErrMsg