Fix a crash-on-valid where a block capture copy expression was
picking up cleanups from earlier in the statement.  Also fix a
crash-on-invalid where a reference to an invalid decl from an
enclosing scope was causing an expression to fail to build, but
only *after* a cleanup was registered from that statement,
causing an assertion downstream.

The crash-on-valid is rdar://13459289.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@177692 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 8213739..5597bf6 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -7916,6 +7916,7 @@
     // Regardless, we don't want to ignore array nesting when
     // constructing this copy.
     if (type->isStructureOrClassType()) {
+      EnterExpressionEvaluationContext scope(*this, PotentiallyEvaluated);
       SourceLocation poi = var->getLocation();
       Expr *varRef =new (Context) DeclRefExpr(var, false, type, VK_LValue, poi);
       ExprResult result