Parse: Don't reorder tokens using ConsumeToken

ConsumeToken doesn't work with special tokens.  Instead, just use PP.Lex
to eat the token.

This fixes PR21817.

llvm-svn: 224232

clang/include/clang/Parse/Parser.h

@@ -339,7 +339,7 @@ private:
   void UnconsumeToken(Token &Consumed) {
       Token Next = Tok;
       PP.EnterToken(Consumed);
-      ConsumeToken();
+      PP.Lex(Tok);
       PP.EnterToken(Next);
   }
 

clang/test/SemaCXX/typo-correction.cpp

@@ -4,6 +4,11 @@
 // afoul the hard-coded limit (escape hatch) of 20 different typos whose
 // correction was attempted by Sema::CorrectTypo
 
+namespace PR21817{
+int a(-rsing[2]); // expected-error {{undeclared identifier 'rsing'; did you mean 'using'?}}
+                  // expected-error@-1 {{expected expression}}
+}
+
 struct errc {
   int v_;
   operator int() const {return v_;}