[clang-format] Fix an ObjC regression introduced with new [[likely]][[unlikely]] support in if/else clauses

Summary:
{D80144} introduce an ObjC regression

Only parse the `[]` if what follows is really an attribute

Reviewers: krasimir, JakeMerdichAMD

Reviewed By: krasimir

Subscribers: rdwampler, aaron.ballman, curdeius, cfe-commits

Tags: #clang, #clang-format

Differential Revision: https://reviews.llvm.org/D80547

clang/lib/Format/UnwrappedLineParser.cpp

@@ -1962,7 +1962,7 @@ void UnwrappedLineParser::parseIfThenElse() {
   if (FormatTok->Tok.is(tok::l_paren))
     parseParens();
   // handle [[likely]] / [[unlikely]]
-  if (FormatTok->is(tok::l_square))
+  if (FormatTok->is(tok::l_square) && tryToParseSimpleAttribute())
     parseSquare();
   bool NeedsUnwrappedLine = false;
   if (FormatTok->Tok.is(tok::l_brace)) {
@@ -1981,7 +1981,7 @@ void UnwrappedLineParser::parseIfThenElse() {
   if (FormatTok->Tok.is(tok::kw_else)) {
     nextToken();
     // handle [[likely]] / [[unlikely]]
-    if (FormatTok->is(tok::l_square))
+    if (FormatTok->Tok.is(tok::l_square) && tryToParseSimpleAttribute())
       parseSquare();
     if (FormatTok->Tok.is(tok::l_brace)) {
       CompoundStatementIndenter Indenter(this, Style, Line->Level);
@@ -2343,6 +2343,51 @@ bool UnwrappedLineParser::parseEnum() {
   // "} n, m;" will end up in one unwrapped line.
 }
 
+namespace {
+// A class used to set and restore the Token position when peeking
+// ahead in the token source.
+class ScopedTokenPosition {
+  unsigned StoredPosition;
+  FormatTokenSource *Tokens;
+
+public:
+  ScopedTokenPosition(FormatTokenSource *Tokens) : Tokens(Tokens) {
+    assert(Tokens && "Tokens expected to not be null");
+    StoredPosition = Tokens->getPosition();
+  }
+
+  ~ScopedTokenPosition() { Tokens->setPosition(StoredPosition); }
+};
+} // namespace
+
+// Look to see if we have [[ by looking ahead, if
+// its not then rewind to the original position.
+bool UnwrappedLineParser::tryToParseSimpleAttribute() {
+  ScopedTokenPosition AutoPosition(Tokens);
+  FormatToken *Tok = Tokens->getNextToken();
+  // We already read the first [ check for the second.
+  if (Tok && !Tok->is(tok::l_square)) {
+    return false;
+  }
+  // Double check that the attribute is just something
+  // fairly simple.
+  while (Tok) {
+    if (Tok->is(tok::r_square)) {
+      break;
+    }
+    Tok = Tokens->getNextToken();
+  }
+  Tok = Tokens->getNextToken();
+  if (Tok && !Tok->is(tok::r_square)) {
+    return false;
+  }
+  Tok = Tokens->getNextToken();
+  if (Tok && Tok->is(tok::semi)) {
+    return false;
+  }
+  return true;
+}
+
 void UnwrappedLineParser::parseJavaEnumBody() {
   // Determine whether the enum is simple, i.e. does not have a semicolon or
   // constants with class bodies. Simple enums can be formatted like braced

clang/lib/Format/UnwrappedLineParser.h

@@ -134,6 +134,7 @@ private:
   bool tryToParseLambdaIntroducer();
   bool tryToParsePropertyAccessor();
   void tryToParseJSFunction();
+  bool tryToParseSimpleAttribute();
   void addUnwrappedLine();
   bool eof() const;
   // LevelDifference is the difference of levels after and before the current

clang/unittests/Format/FormatTest.cpp

@@ -16513,6 +16513,11 @@ TEST_F(FormatTest, LikelyUnlikely) {
                "  return 42;\n"
                "}\n",
                Style);
+
+  verifyFormat("if (argc > 5) [[gnu::unused]] {\n"
+               "  return 29;\n"
+               "}",
+               Style);
 }
 
 TEST_F(FormatTest, LLVMDefaultStyle) {

clang/unittests/Format/FormatTestObjC.cpp

@@ -1434,6 +1434,25 @@ TEST_F(FormatTestObjC, BreakLineBeforeNestedBlockParam) {
       "           }]");
 }
 
+TEST_F(FormatTestObjC, IfNotUnlikely) {
+  Style = getGoogleStyle(FormatStyle::LK_ObjC);
+
+  verifyFormat("if (argc < 5) [obj func:arg];");
+  verifyFormat("if (argc < 5) [[obj1 method1:arg1] method2:arg2];");
+  verifyFormat("if (argc < 5) [[foo bar] baz:i[0]];");
+  verifyFormat("if (argc < 5) [[foo bar] baz:i[0]][1];");
+
+  verifyFormat("if (argc < 5)\n"
+               "  [obj func:arg];\n"
+               "else\n"
+               "  [obj func:arg2];");
+
+  verifyFormat("if (argc < 5) [[unlikely]]\n"
+               "  [obj func:arg];\n"
+               "else [[likely]]\n"
+               "  [obj func:arg2];");
+}
+
 } // end namespace
 } // end namespace format
 } // end namespace clang