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.

llvm-svn: 62407
diff --git a/clang/lib/Basic/SourceLocation.cpp b/clang/lib/Basic/SourceLocation.cpp
index 2b7584e..84fac86 100644
--- a/clang/lib/Basic/SourceLocation.cpp
+++ b/clang/lib/Basic/SourceLocation.cpp
@@ -105,7 +105,7 @@
 
 const llvm::MemoryBuffer* FullSourceLoc::getBuffer() const {
   assert(isValid());
-  return SrcMgr->getBuffer(getFileID());
+  return SrcMgr->getBuffer(*this);
 }
 
 void FullSourceLoc::dump() const {