Disable parsing of single quoted character literals, enabling under a flag.

I didn't want to rip this logic out wholesale.  There is a possibility
the character lexing can be reborn/revisited later, and
disabling it in the parser was easy.

Swift SVN r18102

include/swift/Basic/LangOptions.h

@@ -30,6 +30,9 @@ namespace swift {
   class LangOptions {
   public:
 
+    /// \brief Enable legacy character literals.
+    bool EnableCharacterLiterals = false;
+    
     /// \brief Whether we are debugging the constraint solver.
     ///
     /// This option enables verbose debugging output from the constraint

include/swift/Driver/FrontendOptions.td

@@ -120,6 +120,9 @@ def enable_dynamic_value_type_layout :
 def enable_experimental_patterns : Flag<["-"], "enable-experimental-patterns">,
   HelpText<"Enable experimental 'switch' pattern matching features">;
 
+def enable_character_literals : Flag<["-"], "enable-character-literals">,
+HelpText<"Enable legacy character literals">;
+
 def enable_objc_implicit_properties :
   Flag<["-"], "enable-objc-implicit-properties">,
   HelpText<"Import Objective-C \"implicit properties\" as properties">;

lib/Frontend/CompilerInvocation.cpp

@@ -534,6 +534,8 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
 
   Opts.EnableExperimentalPatterns |= Args.hasArg(OPT_enable_experimental_patterns);
 
+  Opts.EnableCharacterLiterals |= Args.hasArg(OPT_enable_character_literals);
+
   Opts.DebugConstraintSolver |= Args.hasArg(OPT_debug_constraints);
 
   Opts.DebuggerSupport |= Args.hasArg(OPT_debugger_support);

lib/Parse/Lexer.cpp

@@ -1371,6 +1371,11 @@ Restart:
   const char *TokStart = CurPtr;
   
   switch (*CurPtr++) {
+    case '\'':
+      if (LangOpts.EnableCharacterLiterals)
+        return lexCharacterLiteral();
+    SWIFT_FALLTHROUGH;
+
     default: {
     char const *tmp = CurPtr-1;
     if (advanceIfValidStartOfIdentifier(tmp, BufferEnd))
@@ -1542,8 +1547,6 @@ Restart:
   case '5': case '6': case '7': case '8': case '9':
     return lexNumber();
 
-  case '\'':
-    return lexCharacterLiteral();
   case '"':
     return lexStringLiteral();
       

test/Constraints/super_constructor.swift

@@ -1,4 +1,4 @@
-// RUN: %swift %s -parse-as-library -verify
+// RUN: %swift %s -parse-as-library -verify -enable-character-literals
 
 struct S {
   init() {

test/IDE/coloring.swift

@@ -105,10 +105,10 @@ class Attributes {
 }
 
 func stringLikeLiterals() {
-// CHECK: <kw>var</kw> us1: <type>UnicodeScalar</type> = <char>'a'</char>
-  var us1: UnicodeScalar = 'a'
-// CHECK: <kw>var</kw> us2: <type>UnicodeScalar</type> = <char>'ы'</char>
-  var us2: UnicodeScalar = 'ы'
+// CHECK: <kw>var</kw> us1: <type>UnicodeScalar</type> = <str>"a"</str>
+  var us1: UnicodeScalar = "a"
+// CHECK: <kw>var</kw> us2: <type>UnicodeScalar</type> = <str>"ы"</str>
+  var us2: UnicodeScalar = "ы"
 
 // CHECK: <kw>var</kw> ch1: <type>Character</type> = <str>"a"</str>
   var ch1: Character = "a"

test/IRGen/expressions.swift

@@ -1,4 +1,4 @@
-// RUN: %swift -target x86_64-apple-darwin10 %s -emit-ir -parse-stdlib | FileCheck %s
+// RUN: %swift -target x86_64-apple-darwin10 %s -emit-ir -parse-stdlib -enable-character-literals | FileCheck %s
 
 import Swift
 

test/Parse/EOF/unterminated-character-literal-1.swift

@@ -1,4 +1,4 @@
-// RUN: %swift %s -verify -parse
+// RUN: %swift %s -verify -parse -enable-character-literals
 
 // Check that we correctly process an unterminated character literal right near
 // EOF.

test/Parse/EOF/unterminated-character-literal-2.swift

@@ -1,4 +1,4 @@
-// RUN: %swift %s -verify -parse
+// RUN: %swift %s -verify -parse -enable-character-literals
 
 // Check that we correctly process an unterminated character literal right near
 // EOF.

test/Parse/EOF/unterminated-character-literal-missing-newline.swift

@@ -1,4 +1,4 @@
-// RUN: %swift %s -verify -parse
+// RUN: %swift %s -verify -parse -enable-character-literals
 
 // Check that we correctly process an unterminated character literal right near
 // EOF.

test/SILGen/expressions.swift

@@ -1,4 +1,4 @@
-// RUN: %swift -parse-stdlib -emit-silgen %s | FileCheck %s
+// RUN: %swift -parse-stdlib -emit-silgen %s -enable-character-literals | FileCheck %s
 import Swift
 
 typealias CharacterLiteralType = SillyCharacter

test/expr/character_literals.swift

@@ -1,4 +1,4 @@
-// RUN: %swift %s -verify -parse-stdlib
+// RUN: %swift %s -verify -parse-stdlib -enable-character-literals
 
 import Swift
 

test/expr/expressions.swift

@@ -1,4 +1,4 @@
-// RUN: %swift %s -verify
+// RUN: %swift %s -verify -enable-character-literals
 
 //===----------------------------------------------------------------------===//
 // Tests and samples.

test/stdlib/CharacterTypes.swift

@@ -1,4 +1,4 @@
-// RUN: %swift %s -verify
+// RUN: %swift %s -verify -enable-character-literals
 
 func testTypeInference() {
   func isUnicodeScalar(inout _: UnicodeScalar) {}

test/stmt/statements.swift

@@ -1,4 +1,4 @@
-// RUN: %swift %s -verify
+// RUN: %swift %s -verify -enable-character-literals
 
 /* block comments */
 /* /* nested too */ */

unittests/Parse/LexerTests.cpp

@@ -121,6 +121,7 @@ TEST_F(LexerTest, CharacterLiterals) {
 
   MemoryBuffer *Buf = MemoryBuffer::getMemBuffer(Source);
   LangOptions LangOpts;
+  LangOpts.EnableCharacterLiterals = true;
   SourceManager SourceMgr;
   unsigned BufferID = SourceMgr.addNewSourceBuffer(Buf);