4 files changed, 83 insertions, 4 deletions

diff --git a/clang/lib/Format/BreakableToken.cpp b/clang/lib/Format/BreakableToken.cpp
index 09f17a35d07..e9dd253f3ec 100644
--- a/clang/lib/Format/BreakableToken.cpp
+++ b/clang/lib/Format/BreakableToken.cpp
@@ -695,7 +695,7 @@ BreakableLineCommentSection::BreakableLineCommentSection(
       Content[i] = Content[i].substr(0, EndOfLine);
     }
     LineTok = CurrentTok->Next;
-    if (CurrentTok->Next && CurrentTok->Next->NewlinesBefore > 1) {
+    if (CurrentTok->Next && !CurrentTok->Next->ContinuesLineCommentSection) {
       // A line comment section needs to broken by a line comment that is
       // preceded by at least two newlines. Note that we put this break here
       // instead of breaking at a previous stage during parsing, since that
diff --git a/clang/lib/Format/FormatToken.h b/clang/lib/Format/FormatToken.h
index c838cfbe1da..d6a2ff286ae 100644
--- a/clang/lib/Format/FormatToken.h
+++ b/clang/lib/Format/FormatToken.h
@@ -261,6 +261,11 @@ struct FormatToken {
   /// Only set if \c Type == \c TT_StartOfName.
   bool PartOfMultiVariableDeclStmt = false;
 
+  /// \brief Does this line comment continue a line comment section?
+  ///
+  /// Only set to true if \c Type == \c TT_LineComment.
+  bool ContinuesLineCommentSection = false;
+
   /// \brief If this is a bracket, this points to the matching one.
   FormatToken *MatchingParen = nullptr;
 
diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index a96d4d9be3e..2c7b87ee014 100644
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -2066,31 +2066,58 @@ static bool continuesLineComment(const FormatToken &FormatTok,
   // original start column of the min column token of the line.
   //
   // For example, the second line comment continues the first in these cases:
+  //
   // // first line
   // // second line
+  //
   // and:
+  //
   // // first line
   //  // second line
+  //
   // and:
+  //
   // int i; // first line
   //  // second line
+  //
   // and:
+  //
   // do { // first line
   //      // second line
   //   int i;
   // } while (true);
   //
+  // and:
+  //
+  // enum {
+  //   a, // first line
+  //    // second line
+  //   b
+  // };
+  //
   // The second line comment doesn't continue the first in these cases:
+  //
   //   // first line
   //  // second line
+  //
   // and:
+  //
   // int i; // first line
   // // second line
+  //
   // and:
+  //
   // do { // first line
   //   // second line
   //   int i;
   // } while (true);
+  //
+  // and:
+  //
+  // enum {
+  //   a, // first line
+  //   // second line
+  // };
   const FormatToken *MinColumnToken = Line.Tokens.front().Tok;
 
   // Scan for '{//'. If found, use the column of '{' as a min column for line
@@ -2103,6 +2130,11 @@ static bool continuesLineComment(const FormatToken &FormatTok,
       break;
     }
     PreviousToken = Node.Tok;
+
+    // Grab the last newline preceding a token in this unwrapped line.
+    if (Node.Tok->NewlinesBefore > 0) {
+      MinColumnToken = Node.Tok;
+    }
   }
   if (PreviousToken && PreviousToken->is(tok::l_brace)) {
     MinColumnToken = PreviousToken;
@@ -2130,7 +2162,8 @@ void UnwrappedLineParser::flushComments(bool NewlineBeforeNext) {
     //
     // FIXME: Consider putting separate line comment sections as children to the
     // unwrapped line instead.
-    if (isOnNewLine(**I) && JustComments && !continuesLineComment(**I, *Line))
+    (*I)->ContinuesLineCommentSection = continuesLineComment(**I, *Line);
+    if (isOnNewLine(**I) && JustComments && !(*I)->ContinuesLineCommentSection)
       addUnwrappedLine();
     pushToken(*I);
   }
@@ -2196,7 +2229,9 @@ void UnwrappedLineParser::readToken() {
 
     if (!FormatTok->Tok.is(tok::comment))
       return;
-    if (!continuesLineComment(*FormatTok, *Line) &&
+    FormatTok->ContinuesLineCommentSection =
+        continuesLineComment(*FormatTok, *Line);
+    if (!FormatTok->ContinuesLineCommentSection &&
         (isOnNewLine(*FormatTok) || FormatTok->IsFirst)) {
       CommentsInCurrentLine = false;
     }
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 497015bb095..1f81f5fbd2f 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -951,7 +951,46 @@ TEST_F(FormatTest, UnderstandsSingleLineComments) {
                    "  c\n"
                    "};",
                    getLLVMStyleWithColumns(20)));
-
+  EXPECT_EQ("enum A {\n"
+            "  a, // line 1\n"
+            "  // line 2\n"
+            "};",
+            format("enum A {\n"
+                   "  a, // line 1\n"
+                   "  // line 2\n"
+                   "};",
+                   getLLVMStyleWithColumns(20)));
+  EXPECT_EQ("enum A {\n"
+            "  a, // line 1\n"
+            "     // line 2\n"
+            "};",
+            format("enum A {\n"
+                   "  a, // line 1\n"
+                   "   // line 2\n"
+                   "};",
+                   getLLVMStyleWithColumns(20)));
+  EXPECT_EQ("enum A {\n"
+            "  a, // line 1\n"
+            "  // line 2\n"
+            "  b\n"
+            "};",
+            format("enum A {\n"
+                   "  a, // line 1\n"
+                   "  // line 2\n"
+                   "  b\n"
+                   "};",
+                   getLLVMStyleWithColumns(20)));
+  EXPECT_EQ("enum A {\n"
+            "  a, // line 1\n"
+            "     // line 2\n"
+            "  b\n"
+            "};",
+            format("enum A {\n"
+                   "  a, // line 1\n"
+                   "   // line 2\n"
+                   "  b\n"
+                   "};",
+                   getLLVMStyleWithColumns(20)));
   verifyFormat(
       "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa =\n"
       "    bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb; // Trailing comment");