[clang-format] Separate line comment sections after a right brace from comment sections in the scope.

Summary:
The following two comment lines form a single comment section:
```
if (1) { // line 1
   // line 2
}
```
This is because the break of a comment section was based on the original column
of the first token of the previous line (in this case, the 'if').
This patch splits these two comment lines into different sections by taking into
account the original column of the right brace preceding the first line comment
where applicable.

Reviewers: djasper

Reviewed By: djasper

Subscribers: cfe-commits, klimek

Differential Revision: https://reviews.llvm.org/D29291

llvm-svn: 293539

1 files changed, 39 insertions, 7 deletions

diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index 5e67bde1f24..c10a13f39e0 100644
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -2051,14 +2051,19 @@ static bool continuesLineComment(const FormatToken &FormatTok,
                                  const UnwrappedLine &Line) {
   if (Line.Tokens.empty())
     return false;
-  const FormatToken &FirstLineTok = *Line.Tokens.front().Tok;
+
   // If Line starts with a line comment, then FormatTok continues the comment
-  // section if its original column is greater or equal to the  original start
+  // section if its original column is greater or equal to the original start
   // column of the line.
   //
-  // If Line starts with a a different token, then FormatTok continues the
-  // comment section if its original column greater than the original start
-  // column of the line.
+  // Define the min column token of a line as follows: if a line ends in '{' or
+  // contains a '{' followed by a line comment, then the min column token is
+  // that '{'. Otherwise, the min column token of the line is the first token of
+  // the line.
+  //
+  // If Line starts with a token other than a line comment, then FormatTok
+  // continues the comment section if its original column is greater than the
+  // 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
@@ -2069,6 +2074,11 @@ static bool continuesLineComment(const FormatToken &FormatTok,
   // and:
   // int i; // first line
   //  // second line
+  // and:
+  // do { // first line
+  //      // second line
+  //   int i;
+  // } while (true);
   //
   // The second line comment doesn't continue the first in these cases:
   //   // first line
@@ -2076,9 +2086,31 @@ static bool continuesLineComment(const FormatToken &FormatTok,
   // and:
   // int i; // first line
   // // second line
+  // and:
+  // do { // first line
+  //   // second line
+  //   int i;
+  // } while (true);
+  const FormatToken *MinColumnToken = Line.Tokens.front().Tok;
+
+  // Scan for '{//'. If found, use the column of '{' as a min column for line
+  // comment section continuation.
+  const FormatToken *PreviousToken = nullptr;
+  for (const UnwrappedLineNode Node : Line.Tokens) {
+    if (PreviousToken && PreviousToken->is(tok::l_brace) &&
+        isLineComment(*Node.Tok)) {
+      MinColumnToken = PreviousToken;
+      break;
+    }
+    PreviousToken = Node.Tok;
+  }
+  if (PreviousToken && PreviousToken->is(tok::l_brace)) {
+    MinColumnToken = PreviousToken;
+  }
+
   unsigned MinContinueColumn =
-      FirstLineTok.OriginalColumn +
-      ((isLineComment(FirstLineTok) && !FirstLineTok.Next) ? 0 : 1);
+      MinColumnToken->OriginalColumn +
+      (isLineComment(*MinColumnToken) ? 0 : 1);
   return isLineComment(FormatTok) && FormatTok.NewlinesBefore == 1 &&
          isLineComment(*(Line.Tokens.back().Tok)) &&
          FormatTok.OriginalColumn >= MinContinueColumn;