Stronger respect the input codes line breaks wrt. comments.

clang-format should not change whether or not there is a line break
before a line comment as this strongly influences the percieved binding.

User input: void f(int a,
                   // b is awesome
		   int b);
            void g(int a, // a is awesome
		   int b);
Before:     void f(int a, // b is awesome
                   int b);
            void g(int a, // a is awesome
		   int b);
After:      <unchanged from input>

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172361 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 18 insertions, 4 deletions

diff --git a/lib/Format/Format.cpp b/lib/Format/Format.cpp
index 727e85fa4f..67a5b8c4cd 100644
--- a/lib/Format/Format.cpp
+++ b/lib/Format/Format.cpp
@@ -901,9 +901,12 @@ public:
     if (Current.FormatTok.MustBreakBefore) {
       Current.MustBreakBefore = true;
     } else {
-      if (Current.Type == TT_CtorInitializerColon || Current.Parent->Type ==
-          TT_LineComment || (Current.is(tok::string_literal) &&
-                             Current.Parent->is(tok::string_literal))) {
+      if (Current.Type == TT_LineComment) {
+        Current.MustBreakBefore = Current.FormatTok.NewlinesBefore > 0;
+      } else if (Current.Type == TT_CtorInitializerColon ||
+                 Current.Parent->Type == TT_LineComment ||
+                 (Current.is(tok::string_literal) &&
+                  Current.Parent->is(tok::string_literal))) {
         Current.MustBreakBefore = true;
       } else {
         Current.MustBreakBefore = false;
@@ -1219,7 +1222,10 @@ private:
       return false;
 
     if (Right.is(tok::comment))
-      return !Right.Children.empty();
+      // We rely on MustBreakBefore being set correctly here as we should not
+      // change the "binding" behavior of a comment.
+      return false;
+
     if (Right.is(tok::r_paren) || Right.is(tok::l_brace) ||
         Right.is(tok::greater))
       return false;
diff --git a/unittests/Format/FormatTest.cpp b/unittests/Format/FormatTest.cpp
index f3da5061f2..a8417f1efd 100644
--- a/unittests/Format/FormatTest.cpp
+++ b/unittests/Format/FormatTest.cpp
@@ -285,6 +285,14 @@ TEST_F(FormatTest, UnderstandsSingleLineComments) {
   verifyFormat("void f() {\n"
                "  // Doesn't do anything\n"
                "}");
+  verifyFormat("void f(int i, // some comment (probably for i)\n"
+               "       int j, // some comment (probably for j)\n"
+               "       int k); // some comment (probably for k)");
+  verifyFormat("void f(int i,\n"
+               "       // some comment (probably for j)\n"
+               "       int j,\n"
+               "       // some comment (probably for k)\n"
+               "       int k);");
 
   verifyFormat("int i // This is a fancy variable\n"
                "    = 5;");