[Lexer] Remove the public Lexer constructor that accepts a StringRef.

Replace uses of it with the newly introduced constructor that accepts a buffer ID.
The StringRef constructor was rather unsafe since it had the implicit requirement that the StringRef
was null-terminated.

Swift SVN r6942

include/swift/Parse/Lexer.h

@@ -76,12 +76,6 @@ class Lexer {
   void primeLexer();
 
 public:
-  Lexer(llvm::StringRef Buffer, SourceManager &SourceMgr,
-        DiagnosticEngine *Diags, bool InSILMode, bool KeepComments = false)
-      : Lexer(SourceMgr, Buffer, Diags, Buffer.begin(), InSILMode,
-              KeepComments, /*Prime=*/true) {
-  }
-
   Lexer(SourceManager &SourceMgr, unsigned BufferID,
         DiagnosticEngine *Diags, bool InSILMode, bool KeepComments = false,
         unsigned Offset = 0, unsigned EndOffset = 0);

lib/Parse/Parser.cpp

@@ -243,9 +243,8 @@ Parser::Parser(Lexer *Lex, TranslationUnit *TU,
 Parser::Parser(unsigned BufferID, TranslationUnit *TU,
                bool IsMainModule, SILParserState *SIL,
                PersistentParserState *PersistentState)
-  : Parser(new Lexer(TU->getASTContext().SourceMgr
-                         ->getMemoryBuffer(BufferID)->getBuffer(),
-                     TU->getASTContext().SourceMgr, &TU->getASTContext().Diags,
+  : Parser(new Lexer(TU->getASTContext().SourceMgr, BufferID,
+                     &TU->getASTContext().Diags,
                      /*InSILMode=*/SIL != nullptr, /*KeepComments=*/false),
            TU, TU->getASTContext().Diags, SIL, PersistentState) {
   this->IsMainModule = IsMainModule;

tools/swift/Immediate.cpp

@@ -1060,10 +1060,10 @@ class REPLEnvironment {
       case REPLInputKind::REPLDirective: {
         auto Buffer =
             llvm::MemoryBuffer::getMemBufferCopy(Line, "<REPL Input>");
-        TU->getASTContext().SourceMgr->AddNewSourceBuffer(Buffer,
-                                                          llvm::SMLoc());
-        Lexer L(Buffer->getBuffer(), CI.getSourceMgr(), nullptr,
-                false /*not SIL*/);
+        unsigned BufferID =
+            TU->getASTContext().SourceMgr->AddNewSourceBuffer(Buffer,
+                                                              llvm::SMLoc());
+        Lexer L(CI.getSourceMgr(), BufferID, nullptr, false /*not SIL*/);
         Token Tok;
         L.lex(Tok);
         assert(Tok.is(tok::colon));

unittests/Parse/LexerTests.cpp

@@ -14,9 +14,7 @@ class LexerTest : public ::testing::Test {
 public:
 
   std::vector<Token> tokenizeAndKeepEOF(unsigned BufferID) {
-    const llvm::MemoryBuffer *Buffer = SourceMgr->getMemoryBuffer(BufferID);
-    Lexer L(Buffer->getBuffer(), SourceMgr, /*Diags=*/nullptr,
-            /*InSILMode=*/false);
+    Lexer L(SourceMgr, BufferID, /*Diags=*/nullptr, /*InSILMode=*/false);
     std::vector<Token> Tokens;
     do {
       Tokens.emplace_back();