Correctly indent with tabs when whitespace starts from the column not divisible by TabWidth.

Summary:
The width of the first inserted tab character depends on the initial
column, so we need to handle the first tab in a special manner.

Reviewers: klimek, djasper

Reviewed By: klimek

CC: cfe-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D1763

llvm-svn: 191497

2 files changed, 12 insertions, 3 deletions

diff --git a/clang/lib/Format/WhitespaceManager.cpp b/clang/lib/Format/WhitespaceManager.cpp
index c0a3f5d60bd..50ff8582d39 100644
--- a/clang/lib/Format/WhitespaceManager.cpp
+++ b/clang/lib/Format/WhitespaceManager.cpp
@@ -225,7 +225,7 @@ void WhitespaceManager::generateChanges() {
                           C.PreviousEndOfTokenColumn, C.EscapedNewlineColumn);
       else
         appendNewlineText(ReplacementText, C.NewlinesBefore);
-      appendIndentText(ReplacementText, C.Spaces);
+      appendIndentText(ReplacementText, C.Spaces, C.StartOfTokenColumn - C.Spaces);
       ReplacementText.append(C.CurrentLinePrefix);
       storeReplacement(C.OriginalWhitespaceRange, ReplacementText);
     }
@@ -264,10 +264,18 @@ void WhitespaceManager::appendNewlineText(std::string &Text, unsigned Newlines,
   }
 }
 
-void WhitespaceManager::appendIndentText(std::string &Text, unsigned Spaces) {
+void WhitespaceManager::appendIndentText(std::string &Text, unsigned Spaces,
+                                         unsigned WhitespaceStartColumn) {
   if (!Style.UseTab) {
     Text.append(std::string(Spaces, ' '));
   } else {
+    unsigned FirstTabWidth =
+        Style.TabWidth - WhitespaceStartColumn % Style.TabWidth;
+    // Indent with tabs only when there's at least one full tab.
+    if (FirstTabWidth + Style.TabWidth <= Spaces) {
+      Spaces -= FirstTabWidth;
+      Text.append("\t");
+    }
     Text.append(std::string(Spaces / Style.TabWidth, '\t'));
     Text.append(std::string(Spaces % Style.TabWidth, ' '));
   }
diff --git a/clang/lib/Format/WhitespaceManager.h b/clang/lib/Format/WhitespaceManager.h
index 2c58216d1cd..642b5b682bd 100644
--- a/clang/lib/Format/WhitespaceManager.h
+++ b/clang/lib/Format/WhitespaceManager.h
@@ -157,7 +157,8 @@ private:
   void appendNewlineText(std::string &Text, unsigned Newlines,
                          unsigned PreviousEndOfTokenColumn,
                          unsigned EscapedNewlineColumn);
-  void appendIndentText(std::string &Text, unsigned Spaces);
+  void appendIndentText(std::string &Text, unsigned Spaces,
+                        unsigned WhitespaceStartColumn);
 
   SmallVector<Change, 16> Changes;
   SourceManager &SourceMgr;