Format a line if a range in its leading whitespace was selected.

With [] marking the selected range, clang-format invoked on

    [  ]   int a;

Would so far not reformat anything. With this patch, it formats a
line if its leading whitespace is touched.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@176435 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Format/Format.cpp b/lib/Format/Format.cpp
index a3c5e50..f7702cb 100644
--- a/lib/Format/Format.cpp
+++ b/lib/Format/Format.cpp
@@ -995,6 +995,9 @@
     // Consume and record whitespace until we find a significant token.
     while (FormatTok.Tok.is(tok::unknown)) {
       unsigned Newlines = Text.count('\n');
+      if (Newlines > 0)
+        FormatTok.LastNewlineOffset =
+            FormatTok.WhiteSpaceLength + Text.rfind('\n') + 1;
       unsigned EscapedNewlines = Text.count("\\\n");
       FormatTok.NewlinesBefore += Newlines;
       FormatTok.HasUnescapedNewline |= EscapedNewlines != Newlines;
@@ -1371,7 +1374,8 @@
     const FormatToken *First = &TheLine.First.FormatTok;
     const FormatToken *Last = &TheLine.Last->FormatTok;
     CharSourceRange LineRange = CharSourceRange::getTokenRange(
-        First->Tok.getLocation(), Last->Tok.getLocation());
+        First->WhiteSpaceStart.getLocWithOffset(First->LastNewlineOffset),
+        Last->Tok.getLocation());
     for (unsigned i = 0, e = Ranges.size(); i != e; ++i) {
       if (!SourceMgr.isBeforeInTranslationUnit(LineRange.getEnd(),
                                                Ranges[i].getBegin()) &&
diff --git a/lib/Format/UnwrappedLineParser.h b/lib/Format/UnwrappedLineParser.h
index 5db5e7b..f4fecc5 100644
--- a/lib/Format/UnwrappedLineParser.h
+++ b/lib/Format/UnwrappedLineParser.h
@@ -33,8 +33,8 @@
 struct FormatToken {
   FormatToken()
       : NewlinesBefore(0), HasUnescapedNewline(false), WhiteSpaceLength(0),
-        TokenLength(0), IsFirst(false), MustBreakBefore(false) {
-  }
+        LastNewlineOffset(0), TokenLength(0), IsFirst(false),
+        MustBreakBefore(false) {}
 
   /// \brief The \c Token.
   Token Tok;
@@ -59,6 +59,10 @@
   /// the \c Token.
   unsigned WhiteSpaceLength;
 
+  /// \brief The offset just past the last '\n' in this token's leading
+  /// whitespace (relative to \c WhiteSpaceStart). 0 if there is no '\n'.
+  unsigned LastNewlineOffset;
+
   /// \brief The length of the non-whitespace parts of the token. This is
   /// necessary because we need to handle escaped newlines that are stored
   /// with the token.