Revert r197496, as it broke REVERTIBLE_TYPE_TRAITs from PCH files.

Also add a test to make sure that this doesn't break again. Fixes PR21036.

llvm-svn: 218292

1 files changed, 42 insertions, 5 deletions

diff --git a/clang/lib/Parse/ParseExpr.cpp b/clang/lib/Parse/ParseExpr.cpp
index 0e4dfb91ad5..2b0daad60f7 100644
--- a/clang/lib/Parse/ParseExpr.cpp
+++ b/clang/lib/Parse/ParseExpr.cpp
@@ -708,11 +708,48 @@ ExprResult Parser::ParseCastExpression(bool isUnaryExpression,
       // If this identifier was reverted from a token ID, and the next token
       // is a parenthesis, this is likely to be a use of a type trait. Check
       // those tokens.
-      if (Next.is(tok::l_paren) && Tok.is(tok::identifier) &&
-          Tok.getIdentifierInfo()->hasRevertedTokenIDToIdentifier() &&
-          TryIdentKeywordUpgrade())
-        return ParseCastExpression(isUnaryExpression, isAddressOfOperand,
-                                   NotCastExpr, isTypeCast);
+      if (Next.is(tok::l_paren) &&
+          Tok.is(tok::identifier) &&
+          Tok.getIdentifierInfo()->hasRevertedTokenIDToIdentifier()) {
+        IdentifierInfo *II = Tok.getIdentifierInfo();
+        // Build up the mapping of revertible type traits, for future use.
+        if (RevertibleTypeTraits.empty()) {
+#define RTT_JOIN(X,Y) X##Y
+#define REVERTIBLE_TYPE_TRAIT(Name)                         \
+          RevertibleTypeTraits[PP.getIdentifierInfo(#Name)] \
+            = RTT_JOIN(tok::kw_,Name)
+
+          REVERTIBLE_TYPE_TRAIT(__is_arithmetic);
+          REVERTIBLE_TYPE_TRAIT(__is_convertible);
+          REVERTIBLE_TYPE_TRAIT(__is_empty);
+          REVERTIBLE_TYPE_TRAIT(__is_floating_point);
+          REVERTIBLE_TYPE_TRAIT(__is_function);
+          REVERTIBLE_TYPE_TRAIT(__is_fundamental);
+          REVERTIBLE_TYPE_TRAIT(__is_integral);
+          REVERTIBLE_TYPE_TRAIT(__is_member_function_pointer);
+          REVERTIBLE_TYPE_TRAIT(__is_member_pointer);
+          REVERTIBLE_TYPE_TRAIT(__is_pod);
+          REVERTIBLE_TYPE_TRAIT(__is_pointer);
+          REVERTIBLE_TYPE_TRAIT(__is_same);
+          REVERTIBLE_TYPE_TRAIT(__is_scalar);
+          REVERTIBLE_TYPE_TRAIT(__is_signed);
+          REVERTIBLE_TYPE_TRAIT(__is_unsigned);
+          REVERTIBLE_TYPE_TRAIT(__is_void);
+#undef REVERTIBLE_TYPE_TRAIT
+#undef RTT_JOIN
+        }
+
+        // If we find that this is in fact the name of a type trait,
+        // update the token kind in place and parse again to treat it as
+        // the appropriate kind of type trait.
+        llvm::SmallDenseMap<IdentifierInfo *, tok::TokenKind>::iterator Known
+          = RevertibleTypeTraits.find(II);
+        if (Known != RevertibleTypeTraits.end()) {
+          Tok.setKind(Known->second);
+          return ParseCastExpression(isUnaryExpression, isAddressOfOperand,
+                                     NotCastExpr, isTypeCast);
+        }
+      }
 
       if (Next.is(tok::coloncolon) ||
           (!ColonIsSacred && Next.is(tok::colon)) ||