Index: clang/lib/Rewrite/Rewriter.cpp
===================================================================
--- clang/lib/Rewrite/Rewriter.cpp
+++ clang/lib/Rewrite/Rewriter.cpp
@@ -168,10 +168,11 @@
   // start of the last token if this is a token range.
   if (Range.isTokenRange())
     EndOff += Lexer::MeasureTokenLength(Range.getEnd(), *SourceMgr, *LangOpts);
-
+// TODO: This means that CharSourceRange is half-open otherwise we're getting the wrong number here (think about a single character range).
   return EndOff-StartOff;
 }
 
+// TODO: This means that "the input SourceRange" is half-open token range which is conflicting with how we use SourceRange in translateCXSourceRange.
 int Rewriter::getRangeSize(SourceRange Range, RewriteOptions opts) const {
   return getRangeSize(CharSourceRange::getTokenRange(Range), opts);
 }
@@ -299,6 +300,7 @@
   unsigned StartOffs = getLocationOffsetAndFileID(Loc, FID);
   RewriteOptions rangeOpts;
   rangeOpts.IncludeInsertsAtBeginOfRange = false;
+  // TODO: This means getRangeSize(SourceRange&) really expects half-closed token range.
   StartOffs += getRangeSize(SourceRange(Loc, Loc), rangeOpts);
   getEditBuffer(FID).InsertText(StartOffs, Str, /*InsertAfter*/true);
   return false;
Index: clang/tools/libclang/CIndex.cpp
===================================================================
--- clang/tools/libclang/CIndex.cpp
+++ clang/tools/libclang/CIndex.cpp
@@ -158,7 +158,7 @@
         Lexer::MeasureTokenLength(SM.getSpellingLoc(EndLoc), SM, LangOpts);
     EndLoc = EndLoc.getLocWithOffset(Length);
   }
-
+  // TODO: This means that CharSourceRange is half-open even when not token range because the return type is half-open (per doxygen) and for non-token ranges we're not converting the end in any way.
   CXSourceRange Result = {
       {&SM, &LangOpts}, R.getBegin().getRawEncoding(), EndLoc.getRawEncoding()};
   return Result;
@@ -6827,6 +6827,7 @@
             Buffer.data() + BeginLocInfo.second, Buffer.end());
   Lex.SetCommentRetentionState(true);
 
+  // TODO: This means SourceRange is half-open as we stop before the end.
   // Lex tokens until we hit the end of the range.
   const char *EffectiveBufferEnd = Buffer.data() + EndLocInfo.second;
   Token Tok;
Index: clang/tools/libclang/CXSourceLocation.h
===================================================================
--- clang/tools/libclang/CXSourceLocation.h
+++ clang/tools/libclang/CXSourceLocation.h
@@ -66,6 +66,7 @@
   return SourceLocation::getFromRawEncoding(L.int_data);
 }
 
+// TODO: This means that SourceRange is just a half-open interval of chars because that's the semantics we specify in libclang API.
 static inline SourceRange translateCXSourceRange(CXSourceRange R) {
   return SourceRange(SourceLocation::getFromRawEncoding(R.begin_int_data),
                      SourceLocation::getFromRawEncoding(R.end_int_data));
Index: clang/unittests/Rewrite/RewriterTest.cpp
===================================================================
--- clang/unittests/Rewrite/RewriterTest.cpp
+++ clang/unittests/Rewrite/RewriterTest.cpp
@@ -75,6 +75,21 @@
   EXPECT_EQ(T.Rewrite.getRewrittenText(T.makeCharRange(42, 47)), "bar;");
   T.Rewrite.ReplaceText(T.SRange, "0");
   EXPECT_EQ(T.Rewrite.getRewrittenText(T.makeCharRange(42, 47)), "0;");
+
+TEST(Rewriter, RangeSize) {
+  StringRef Code = "void foo(){ }";
+
+  RangeTypeTest T(Code, 0, 13);
+  const auto Len = T.Rewrite.getRangeSize(T.makeCharRange(5, 8).getAsRange(), Rewriter::RewriteOptions{});
+  EXPECT_EQ(Len, 3);
+}
+
+TEST(Rewriter, RewriteRegression) {
+  StringRef Code = "void foo(){ }";
+
+  RangeTypeTest T(Code, 0, 13);
+  T.Rewrite.ReplaceText(T.makeCharRange(5, 8).getAsRange(), "bar");
+  EXPECT_EQ(T.Rewrite.getRewrittenText(T.makeCharRange(0, 13)), "void bar(){ }");
 }
 
 } // anonymous namespace
Index: clang/unittests/libclang/LibclangTest.cpp
===================================================================
--- clang/unittests/libclang/LibclangTest.cpp
+++ clang/unittests/libclang/LibclangTest.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang-c/Index.h"
+#include "clang/Basic/SourceLocation.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/FileSystem.h"
@@ -736,3 +737,21 @@
 
   CheckTokenKinds();
 }
+
+TEST_F(LibclangParseTest, TranslateSourceRange) {
+  std::string Main = "main.c";
+  WriteFile(Main, "int main(void);\n");
+
+  ClangTU = clang_parseTranslationUnit(Index, Main.c_str(), nullptr, 0, nullptr, 0, TUFlags);
+
+  CXFile File = clang_getFile(ClangTU, Main.c_str());
+  CXSourceLocation B = clang_getLocation(ClangTU, File, 1, 4);
+  CXSourceLocation E = clang_getLocation(ClangTU, File, 1, 8);
+
+  CXSourceRange Rng	= clang_getRange(B, E);
+
+  CXToken *Tokens;
+  unsigned int NumTokens;
+  clang_tokenize(ClangTU, Rng, &Tokens, &NumTokens);
+  ASSERT_EQ(NumTokens, 1);
+}