[clang-format] Wrap inserted braces only if preceded by comments

Fixes #57805.

Differential Revision: https://reviews.llvm.org/D134233

clang/lib/Format/Format.cpp

@@ -1871,7 +1871,7 @@ private:
         std::string Brace;
         if (Token->BraceCount < 0) {
           assert(Token->BraceCount == -1);
-          Brace = "\n{";
+          Brace = Token->is(tok::comment) ? "\n{" : "{";
         } else {
           Brace = '\n' + std::string(Token->BraceCount, '}');
         }

clang/unittests/Format/FormatTest.cpp

@@ -25388,6 +25388,12 @@ TEST_F(FormatTest, InsertBraces) {
                "} while (0);",
                Style);
 
+  Style.RemoveBracesLLVM = true;
+  verifyFormat("if (a) //\n"
+               "  return b;",
+               Style);
+  Style.RemoveBracesLLVM = false;
+
   Style.ColumnLimit = 15;
 
   verifyFormat("#define A     \\\n"