this massive patch introduces a simple new abstraction: it makes
"FileID" a concept that is now enforced by the compiler's type checker
instead of yet-another-random-unsigned floating around.

This is an important distinction from the "FileID" currently tracked by
SourceLocation.  *That* FileID may refer to the start of a file or to a
chunk within it.  The new FileID *only* refers to the file (and its 
#include stack and eventually #line data), it cannot refer to a chunk.

FileID is a completely opaque datatype to all clients, only SourceManager
is allowed to poke and prod it.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@62407 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/Driver/RewriteObjC.cpp b/Driver/RewriteObjC.cpp
index cee66f7..8af30f2 100644
--- a/Driver/RewriteObjC.cpp
+++ b/Driver/RewriteObjC.cpp
@@ -47,7 +47,7 @@
     ASTContext *Context;
     SourceManager *SM;
     TranslationUnitDecl *TUDecl;
-    unsigned MainFileID;
+    FileID MainFileID;
     const char *MainFileStart, *MainFileEnd;
     SourceLocation LastIncLoc;
     
@@ -597,7 +597,7 @@
 //===----------------------------------------------------------------------===//
 
 void RewriteObjC::RewriteInclude() {
-  SourceLocation LocStart = SourceLocation::getFileLoc(MainFileID, 0);
+  SourceLocation LocStart = SM->getLocForStartOfFile(MainFileID);
   std::pair<const char*, const char*> MainBuf = SM->getBufferData(MainFileID);
   const char *MainBufStart = MainBuf.first;
   const char *MainBufEnd = MainBuf.second;
@@ -645,8 +645,8 @@
     unsigned Spaces = 8-(VCol & 7);
     
     // Get the location of the tab.
-    SourceLocation TabLoc =
-      SourceLocation::getFileLoc(MainFileID, BufPtr-MainBufStart);
+    SourceLocation TabLoc = SM->getLocForStartOfFile(MainFileID);
+    TabLoc = TabLoc.getFileLocWithOffset(BufPtr-MainBufStart);
     
     // Rewrite the single tab character into a sequence of spaces.
     ReplaceText(TabLoc, 1, "        ", Spaces);
@@ -4501,7 +4501,7 @@
   
   RewriteInclude();
   
-  InsertText(SourceLocation::getFileLoc(MainFileID, 0), 
+  InsertText(SM->getLocForStartOfFile(MainFileID), 
              Preamble.c_str(), Preamble.size(), false);
   
   if (ClassImplementation.size() || CategoryImplementation.size())