Introduce reference counting for statements and expressions, using it
to allow sharing of nodes. Simplifies some aspects of template
instantiation, and fixes both PR3444 and <rdar://problem/6757457>.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@78450 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Frontend/PCHReaderStmt.cpp b/lib/Frontend/PCHReaderStmt.cpp
index 6b97e61..3040a52 100644
--- a/lib/Frontend/PCHReaderStmt.cpp
+++ b/lib/Frontend/PCHReaderStmt.cpp
@@ -194,6 +194,10 @@
       PrevSC->setNextSwitchCase(SC);
     else
       S->setSwitchCaseList(SC);
+    
+    // Retain this SwitchCase, since SwitchStmt::addSwitchCase() would
+    // normally retain it (but we aren't calling addSwitchCase).
+    SC->Retain();
     PrevSC = SC;
   }
   return 2;