[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

1 files changed, 14 insertions, 1 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