Don't break line comments with escaped newlines.

Summary:
These can appear when comments contain command lines with quoted line
breaks. As the text (including escaped newlines and '//' from consecutive lines)
is a single line comment, we used to break it even when it didn't exceed column
limit. This is a temporary solution, in the future we may want to support this
case completely - at least adjust leading whitespace when changing indentation
of the first line.

Reviewers: djasper

Reviewed By: djasper

CC: cfe-commits, klimek

Differential Revision: http://llvm-reviews.chandlerc.com/D1146

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@186456 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Format/Format.cpp b/lib/Format/Format.cpp
index c6927ec..11ab58c 100644
--- a/lib/Format/Format.cpp
+++ b/lib/Format/Format.cpp
@@ -905,6 +905,11 @@
       // Only break up default narrow strings.
       if (!Current.TokenText.startswith("\""))
         return 0;
+      // Don't break string literals with escaped newlines. As clang-format must
+      // not change the string's content, it is unlikely that we'll end up with
+      // a better format.
+      if (Current.TokenText.find("\\\n") != StringRef::npos)
+        return 0;
       // Exempts unterminated string literals from line breaking. The user will
       // likely want to terminate the string before any line breaking is done.
       if (Current.IsUnterminatedLiteral)
@@ -919,6 +924,23 @@
     } else if (Current.Type == TT_LineComment &&
                (Current.Previous == NULL ||
                 Current.Previous->Type != TT_ImplicitStringLiteral)) {
+      // Don't break line comments with escaped newlines. These look like
+      // separate line comments, but in fact contain a single line comment with
+      // multiple lines including leading whitespace and the '//' markers.
+      //
+      // FIXME: If we want to handle them correctly, we'll need to adjust
+      // leading whitespace in consecutive lines when changing indentation of
+      // the first line similar to what we do with block comments.
+      StringRef::size_type EscapedNewlinePos = Current.TokenText.find("\\\n");
+      if (EscapedNewlinePos != StringRef::npos) {
+        State.Column =
+            StartColumn +
+            encoding::getCodePointCount(
+                Current.TokenText.substr(0, EscapedNewlinePos), Encoding) +
+            1;
+        return 0;
+      }
+
       Token.reset(new BreakableLineComment(Current, StartColumn,
                                            Line.InPPDirective, Encoding));
     } else {
diff --git a/lib/Format/TokenAnnotator.cpp b/lib/Format/TokenAnnotator.cpp
index 6f6f468..67a0fa8 100644
--- a/lib/Format/TokenAnnotator.cpp
+++ b/lib/Format/TokenAnnotator.cpp
@@ -967,8 +967,9 @@
                Current->is(tok::string_literal) &&
                Current->Previous->isNot(tok::lessless) &&
                Current->Previous->Type != TT_InlineASMColon &&
-               Current->getNextNonComment() &&
-               Current->getNextNonComment()->is(tok::string_literal)) {
+               ((Current->getNextNonComment() &&
+                 Current->getNextNonComment()->is(tok::string_literal)) ||
+                (Current->TokenText.find("\\\n") != StringRef::npos))) {
       Current->MustBreakBefore = true;
     }
     Current->CanBreakBefore =