Only use UnicodeSytanx pretty printing if the locale supports it

using the same check as for unicode quotes.

compiler/main/DynFlags.hs

@@ -777,7 +777,7 @@ data DynFlags = DynFlags {
   pprCols               :: Int,
   traceLevel            :: Int, -- Standard level is 1. Less verbose is 0.
 
-  useUnicodeQuotes      :: Bool,
+  useUnicode      :: Bool,
 
   -- | what kind of {-# SCC #-} to add automatically
   profAuto              :: ProfAuto,
@@ -1295,12 +1295,12 @@ initDynFlags dflags = do
  refRtldInfo <- newIORef Nothing
  refRtccInfo <- newIORef Nothing
  wrapperNum <- newIORef emptyModuleEnv
- canUseUnicodeQuotes <- do let enc = localeEncoding
-                               str = "‘’"
-                           (withCString enc str $ \cstr ->
-                                do str' <- peekCString enc cstr
-                                   return (str == str'))
-                               `catchIOError` \_ -> return False
+ canUseUnicode <- do let enc = localeEncoding
+                         str = "‘’"
+                     (withCString enc str $ \cstr ->
+                          do str' <- peekCString enc cstr
+                             return (str == str'))
+                         `catchIOError` \_ -> return False
  return dflags{
         canGenerateDynamicToo = refCanGenerateDynamicToo,
         nextTempSuffix = refNextTempSuffix,
@@ -1310,7 +1310,7 @@ initDynFlags dflags = do
         generatedDumps = refGeneratedDumps,
         llvmVersion    = refLlvmVersion,
         nextWrapperNum = wrapperNum,
-        useUnicodeQuotes = canUseUnicodeQuotes,
+        useUnicode    = canUseUnicode,
         rtldInfo      = refRtldInfo,
         rtccInfo      = refRtccInfo
         }
@@ -1449,7 +1449,7 @@ defaultDynFlags mySettings =
         flushErr = defaultFlushErr,
         pprUserLength = 5,
         pprCols = 100,
-        useUnicodeQuotes = False,
+        useUnicode = False,
         traceLevel = 1,
         profAuto = NoProfAuto,
         llvmVersion = panic "defaultDynFlags: No llvmVersion",

compiler/main/DynFlags.hs-boot

@@ -9,5 +9,5 @@ targetPlatform       :: DynFlags -> Platform
 pprUserLength        :: DynFlags -> Int
 pprCols              :: DynFlags -> Int
 unsafeGlobalDynFlags :: DynFlags
-useUnicodeQuotes     :: DynFlags -> Bool
+useUnicode     :: DynFlags -> Bool
 useUnicodeSyntax     :: DynFlags -> Bool

compiler/utils/Outputable.lhs

@@ -74,7 +74,7 @@ module Outputable (
 
 import {-# SOURCE #-}   DynFlags( DynFlags,
                                   targetPlatform, pprUserLength, pprCols,
-                                  useUnicodeQuotes, useUnicodeSyntax,
+                                  useUnicode, useUnicodeSyntax,
                                   unsafeGlobalDynFlags )
 import {-# SOURCE #-}   Module( Module, ModuleName, moduleName )
 import {-# SOURCE #-}   OccName( OccName )
@@ -459,7 +459,7 @@ cparen b d     = SDoc $ Pretty.cparen b . runSDoc d
 -- so that we don't get `foo''.  Instead we just have foo'.
 quotes d =
       sdocWithDynFlags $ \dflags ->
-      if useUnicodeQuotes dflags
+      if useUnicode dflags
       then char '‘' <> d <> char '’'
       else SDoc $ \sty ->
            let pp_d = runSDoc d sty
@@ -501,8 +501,9 @@ forAllLit = unicodeSyntax (char '∀') (ptext (sLit "forall"))
 
 unicodeSyntax :: SDoc -> SDoc -> SDoc
 unicodeSyntax unicode plain = sdocWithDynFlags $ \dflags ->
-    if useUnicodeSyntax dflags then unicode
-                               else plain
+    if useUnicode dflags && useUnicodeSyntax dflags
+    then unicode
+    else plain
 
 nest :: Int -> SDoc -> SDoc
 -- ^ Indent 'SDoc' some specified amount

testsuite/tests/driver/Makefile

@@ -556,6 +556,10 @@ T6037:
 T2507:
 	-LC_ALL=C "$(TEST_HC)" $(TEST_HC_OPTS_NO_RECOMP) -c T2507.hs
 
+.PHONY: T8959a
+T8959a:
+	-LC_ALL=C "$(TEST_HC)" $(TEST_HC_OPTS_NO_RECOMP) -c T8959a.hs -XUnicodeSyntax
+
 .PHONY: T703
 T703:
 	$(RM) -rf T703

testsuite/tests/driver/T8959a.hs

+{-# LANGUAGE UnicodeSyntax #-}
+module T8959a where
+
+foo :: Int -> Int
+foo = ()

testsuite/tests/driver/T8959a.stderr

+
+T8959a.hs:5:7:
+    Couldn't match expected type `Int -> Int' with actual type `()'
+    In the expression: ()
+    In an equation for `foo': foo = ()

testsuite/tests/driver/all.T

@@ -391,6 +391,11 @@ test('T2507',
      [when(opsys('mingw32'), expect_fail), when(opsys('darwin'), expect_fail)],
      run_command,
      ['$MAKE -s --no-print-directory T2507'])
+test('T8959a',
+     # The testsuite doesn't know how to set a non-Unicode locale on Windows or Mac OS X
+     [when(opsys('mingw32'), expect_fail), when(opsys('darwin'), expect_fail)],
+     run_command,
+     ['$MAKE -s --no-print-directory T8959a'])
 
 test('T703', normal, run_command, ['$MAKE -s --no-print-directory T703'])
 test('T8101', normal, compile, ['-Wall -fno-code'])