XtextRule now requires that all embedded proto code specify 'proto2'
syntax.

com.google.eclipse.protobuf.test/src/com/google/eclipse/protobuf/junit/core/XtextRule.java

diff --git a/com.google.eclipse.protobuf.test/src/com/google/eclipse/protobuf/junit/core/XtextRule.java b/com.google.eclipse.protobuf.test/src/com/google/eclipse/protobuf/junit/core/XtextRule.java
index 14340fb..4ab24d0 100644
--- a/com.google.eclipse.protobuf.test/src/com/google/eclipse/protobuf/junit/core/XtextRule.java
+++ b/com.google.eclipse.protobuf.test/src/com/google/eclipse/protobuf/junit/core/XtextRule.java
@@ -74,6 +74,9 @@
     IParseResult parseResult = resource.getParseResult();
     if (!parseResult.hasSyntaxErrors()) {
       root = (Protobuf) parseResult.getRootASTElement();
+      if (root.getSyntax() == null) {
+        throw new IllegalStateException("Please specify 'proto2' syntax");
+      }
       return;
     }
     StringBuilder builder = new StringBuilder();