[Parser][ObjC++] Improve diagnostics and recovery when C++ keywords are used

as identifiers in Objective-C++

This commit improves the 'expected identifier' errors that are presented when a
C++ keyword is used as an identifier in Objective-C++ by mentioning that this is
a C++ keyword in the diagnostic message. It also improves the error recovery:
the parser will now treat the C++ keywords as identifiers to prevent unrelated
parsing errors.

rdar://20626062

Differential Revision: https://reviews.llvm.org/D26503

llvm-svn: 299950

4 files changed, 68 insertions, 52 deletions

diff --git a/clang/lib/Basic/IdentifierTable.cpp b/clang/lib/Basic/IdentifierTable.cpp
index 5caa8a6fb21..74c85376c7d 100644
--- a/clang/lib/Basic/IdentifierTable.cpp
+++ b/clang/lib/Basic/IdentifierTable.cpp
@@ -244,7 +244,7 @@ static KeywordStatus getTokenKwStatus(const LangOptions &LangOpts,
 
 /// \brief Returns true if the identifier represents a keyword in the
 /// specified language.
-bool IdentifierInfo::isKeyword(const LangOptions &LangOpts) {
+bool IdentifierInfo::isKeyword(const LangOptions &LangOpts) const {
   switch (getTokenKwStatus(LangOpts, getTokenID())) {
   case KS_Enabled:
   case KS_Extension:
@@ -254,6 +254,19 @@ bool IdentifierInfo::isKeyword(const LangOptions &LangOpts) {
   }
 }
 
+/// \brief Returns true if the identifier represents a C++ keyword in the
+/// specified language.
+bool IdentifierInfo::isCPlusPlusKeyword(const LangOptions &LangOpts) const {
+  if (!LangOpts.CPlusPlus || !isKeyword(LangOpts))
+    return false;
+  // This is a C++ keyword if this identifier is not a keyword when checked
+  // using LangOptions without C++ support.
+  LangOptions LangOptsNoCPP = LangOpts;
+  LangOptsNoCPP.CPlusPlus = false;
+  LangOptsNoCPP.CPlusPlus11 = false;
+  return !isKeyword(LangOptsNoCPP);
+}
+
 tok::PPKeywordKind IdentifierInfo::getPPKeywordID() const {
   // We use a perfect hash function here involving the length of the keyword,
   // the first and third character.  For preprocessor ID's there are no
diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index 85ac71f296c..1465d21ac5e 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -5580,6 +5580,21 @@ void Parser::ParseDirectDeclarator(Declarator &D) {
     if (Tok.is(tok::l_square))
       return ParseMisplacedBracketDeclarator(D);
     if (D.getContext() == Declarator::MemberContext) {
+      // Objective-C++: Detect C++ keywords and try to prevent further errors by
+      // treating these keyword as valid member names.
+      if (getLangOpts().ObjC1 && getLangOpts().CPlusPlus &&
+          Tok.getIdentifierInfo() &&
+          Tok.getIdentifierInfo()->isCPlusPlusKeyword(getLangOpts())) {
+        Diag(getMissingDeclaratorIdLoc(D, Tok.getLocation()),
+             diag::err_expected_member_name_or_semi_objcxx_keyword)
+            << Tok.getIdentifierInfo()
+            << (D.getDeclSpec().isEmpty() ? SourceRange()
+                                          : D.getDeclSpec().getSourceRange());
+        D.SetIdentifier(Tok.getIdentifierInfo(), Tok.getLocation());
+        D.SetRangeEnd(Tok.getLocation());
+        ConsumeToken();
+        goto PastIdentifier;
+      }
       Diag(getMissingDeclaratorIdLoc(D, Tok.getLocation()),
            diag::err_expected_member_name_or_semi)
           << (D.getDeclSpec().isEmpty() ? SourceRange()
diff --git a/clang/lib/Parse/ParseObjc.cpp b/clang/lib/Parse/ParseObjc.cpp
index 9a677d1b40e..77e63efc065 100644
--- a/clang/lib/Parse/ParseObjc.cpp
+++ b/clang/lib/Parse/ParseObjc.cpp
@@ -137,8 +137,7 @@ Parser::ParseObjCAtClassDeclaration(SourceLocation atLoc) {
 
   while (1) {
     MaybeSkipAttributes(tok::objc_class);
-    if (Tok.isNot(tok::identifier)) {
-      Diag(Tok, diag::err_expected) << tok::identifier;
+    if (expectIdentifier()) {
       SkipUntil(tok::semi);
       return Actions.ConvertDeclToDeclGroup(nullptr);
     }
@@ -229,11 +228,8 @@ Decl *Parser::ParseObjCAtInterfaceDeclaration(SourceLocation AtLoc,
 
   MaybeSkipAttributes(tok::objc_interface);
 
-  if (Tok.isNot(tok::identifier)) {
-    Diag(Tok, diag::err_expected)
-        << tok::identifier; // missing class or category name.
-    return nullptr;
-  }
+  if (expectIdentifier())
+    return nullptr; // missing class or category name.
 
   // We have a class or category name - consume it.
   IdentifierInfo *nameId = Tok.getIdentifierInfo();
@@ -319,11 +315,8 @@ Decl *Parser::ParseObjCAtInterfaceDeclaration(SourceLocation AtLoc,
       return nullptr;
     }
 
-    if (Tok.isNot(tok::identifier)) {
-      Diag(Tok, diag::err_expected)
-          << tok::identifier; // missing super class name.
-      return nullptr;
-    }
+    if (expectIdentifier())
+      return nullptr; // missing super class name.
     superClassId = Tok.getIdentifierInfo();
     superClassLoc = ConsumeToken();
 
@@ -1438,12 +1431,9 @@ Decl *Parser::ParseObjCMethodDecl(SourceLocation mLoc,
       cutOffParsing();
       return nullptr;
     }
-    
-    if (Tok.isNot(tok::identifier)) {
-      Diag(Tok, diag::err_expected)
-          << tok::identifier; // missing argument name.
-      break;
-    }
+
+    if (expectIdentifier())
+      break; // missing argument name.
 
     ArgInfo.Name = Tok.getIdentifierInfo();
     ArgInfo.NameLoc = Tok.getLocation();
@@ -1552,8 +1542,7 @@ ParseObjCProtocolReferences(SmallVectorImpl<Decl *> &Protocols,
       return true;
     }
 
-    if (Tok.isNot(tok::identifier)) {
-      Diag(Tok, diag::err_expected) << tok::identifier;
+    if (expectIdentifier()) {
       SkipUntil(tok::greater, StopAtSemi);
       return true;
     }
@@ -2035,10 +2024,8 @@ Parser::ParseObjCAtProtocolDeclaration(SourceLocation AtLoc,
 
   MaybeSkipAttributes(tok::objc_protocol);
 
-  if (Tok.isNot(tok::identifier)) {
-    Diag(Tok, diag::err_expected) << tok::identifier; // missing protocol name.
-    return nullptr;
-  }
+  if (expectIdentifier())
+    return nullptr; // missing protocol name.
   // Save the protocol name, then consume it.
   IdentifierInfo *protocolName = Tok.getIdentifierInfo();
   SourceLocation nameLoc = ConsumeToken();
@@ -2058,8 +2045,7 @@ Parser::ParseObjCAtProtocolDeclaration(SourceLocation AtLoc,
     // Parse the list of forward declarations.
     while (1) {
       ConsumeToken(); // the ','
-      if (Tok.isNot(tok::identifier)) {
-        Diag(Tok, diag::err_expected) << tok::identifier;
+      if (expectIdentifier()) {
         SkipUntil(tok::semi);
         return nullptr;
       }
@@ -2126,11 +2112,8 @@ Parser::ParseObjCAtImplementationDeclaration(SourceLocation AtLoc) {
 
   MaybeSkipAttributes(tok::objc_implementation);
 
-  if (Tok.isNot(tok::identifier)) {
-    Diag(Tok, diag::err_expected)
-        << tok::identifier; // missing class or category name.
-    return nullptr;
-  }
+  if (expectIdentifier())
+    return nullptr; // missing class or category name.
   // We have a class or category name - consume it.
   IdentifierInfo *nameId = Tok.getIdentifierInfo();
   SourceLocation nameLoc = ConsumeToken(); // consume class or category name
@@ -2200,11 +2183,8 @@ Parser::ParseObjCAtImplementationDeclaration(SourceLocation AtLoc) {
     IdentifierInfo *superClassId = nullptr;
     if (TryConsumeToken(tok::colon)) {
       // We have a super class
-      if (Tok.isNot(tok::identifier)) {
-        Diag(Tok, diag::err_expected)
-            << tok::identifier; // missing super class name.
-        return nullptr;
-      }
+      if (expectIdentifier())
+        return nullptr; // missing super class name.
       superClassId = Tok.getIdentifierInfo();
       superClassLoc = ConsumeToken(); // Consume super class name
     }
@@ -2304,16 +2284,12 @@ Decl *Parser::ParseObjCAtAliasDeclaration(SourceLocation atLoc) {
   assert(Tok.isObjCAtKeyword(tok::objc_compatibility_alias) &&
          "ParseObjCAtAliasDeclaration(): Expected @compatibility_alias");
   ConsumeToken(); // consume compatibility_alias
-  if (Tok.isNot(tok::identifier)) {
-    Diag(Tok, diag::err_expected) << tok::identifier;
+  if (expectIdentifier())
     return nullptr;
-  }
   IdentifierInfo *aliasId = Tok.getIdentifierInfo();
   SourceLocation aliasLoc = ConsumeToken(); // consume alias-name
-  if (Tok.isNot(tok::identifier)) {
-    Diag(Tok, diag::err_expected) << tok::identifier;
+  if (expectIdentifier())
     return nullptr;
-  }
   IdentifierInfo *classId = Tok.getIdentifierInfo();
   SourceLocation classLoc = ConsumeToken(); // consume class-name;
   ExpectAndConsume(tok::semi, diag::err_expected_after, "@compatibility_alias");
@@ -2361,11 +2337,9 @@ Decl *Parser::ParseObjCPropertySynthesize(SourceLocation atLoc) {
         cutOffParsing();
         return nullptr;
       }
-      
-      if (Tok.isNot(tok::identifier)) {
-        Diag(Tok, diag::err_expected) << tok::identifier;
+
+      if (expectIdentifier())
         break;
-      }
       propertyIvar = Tok.getIdentifierInfo();
       propertyIvarLoc = ConsumeToken(); // consume ivar-name
     }
@@ -2423,9 +2397,8 @@ Decl *Parser::ParseObjCPropertyDynamic(SourceLocation atLoc) {
       cutOffParsing();
       return nullptr;
     }
-    
-    if (Tok.isNot(tok::identifier)) {
-      Diag(Tok, diag::err_expected) << tok::identifier;
+
+    if (expectIdentifier()) {
       SkipUntil(tok::semi);
       return nullptr;
     }
@@ -3561,8 +3534,8 @@ Parser::ParseObjCProtocolExpression(SourceLocation AtLoc) {
   BalancedDelimiterTracker T(*this, tok::l_paren);
   T.consumeOpen();
 
-  if (Tok.isNot(tok::identifier))
-    return ExprError(Diag(Tok, diag::err_expected) << tok::identifier);
+  if (expectIdentifier())
+    return ExprError();
 
   IdentifierInfo *protocolId = Tok.getIdentifierInfo();
   SourceLocation ProtoIdLoc = ConsumeToken();
diff --git a/clang/lib/Parse/Parser.cpp b/clang/lib/Parse/Parser.cpp
index 81a4580e271..aa8ed91d382 100644
--- a/clang/lib/Parse/Parser.cpp
+++ b/clang/lib/Parse/Parser.cpp
@@ -211,6 +211,21 @@ void Parser::ConsumeExtraSemi(ExtraSemiKind Kind, unsigned TST) {
       << FixItHint::CreateRemoval(SourceRange(StartLoc, EndLoc));
 }
 
+bool Parser::expectIdentifier() {
+  if (Tok.is(tok::identifier))
+    return false;
+  if (const auto *II = Tok.getIdentifierInfo()) {
+    if (II->isCPlusPlusKeyword(getLangOpts())) {
+      Diag(Tok, diag::err_expected_token_instead_of_objcxx_keyword)
+          << tok::identifier << Tok.getIdentifierInfo();
+      // Objective-C++: Recover by treating this keyword as a valid identifier.
+      return false;
+    }
+  }
+  Diag(Tok, diag::err_expected) << tok::identifier;
+  return true;
+}
+
 //===----------------------------------------------------------------------===//
 // Error recovery.
 //===----------------------------------------------------------------------===//