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

[owenpan]

Summary

Fixes https://github.com/llvm/llvm-project/issues/57805.

[MyDeveloperDay]

I love the little and often approach, its so much easier to review, LGTM...

clang/lib/Format/Format.cpp

for (AnnotatedLine *Line : Lines) {
         continue;
       for (FormatToken *Token = Line->First; Token && !Token->Finalized;
            Token = Token->Next) {
         if (Token->BraceCount == 0)
           continue;
         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, '}');
         }
         Token->BraceCount = 0;
         const auto Start = Token->Tok.getEndLoc();
         cantFail(Result.add(tooling::Replacement(SourceMgr, Start, 0, Brace)));
       }
     }

clang/unittests/Format/FormatTest.cpp

verifyFormat("do {\n"
                "#if 0\n"
                "#else\n"
                "  if (b) {\n"
                "#endif\n"
                "  }\n"
                "} while (0);",
                Style);
 
+  Style.RemoveBracesLLVM = true;
+  verifyFormat("if (a) //\n"
+               "  return b;",
+               Style);
+  Style.RemoveBracesLLVM = false;
+
   Style.ColumnLimit = 15;
 
   verifyFormat("#define A     \\\n"
                "  if (a)      \\\n"
                "    f();",
                Style);
 
   verifyFormat("if (a + b >\n"