Update error diagnostics.

Change-Id: I8415450504f95cc3ad35866ed884fafc7ee24c90
diff --git a/slang_rs_backend.cpp b/slang_rs_backend.cpp
index 7c749b9..1c03fc9 100644
--- a/slang_rs_backend.cpp
+++ b/slang_rs_backend.cpp
@@ -156,13 +156,13 @@
   int version = mContext->getVersion();
   if (version == 0) {
     // Not setting a version is an error
-    mDiagEngine.Report(mDiagEngine.getCustomDiagID(
-      clang::DiagnosticsEngine::Error,
-      "Missing pragma for version in source file"));
-  } else if (version > 1) {
-    mDiagEngine.Report(mDiagEngine.getCustomDiagID(
-      clang::DiagnosticsEngine::Error,
-      "Pragma for version in source file must be set to 1"));
+    mDiagEngine.Report(
+        mSourceMgr.getLocForEndOfFile(mSourceMgr.getMainFileID()),
+        mDiagEngine.getCustomDiagID(
+            clang::DiagnosticsEngine::Error,
+            "missing pragma for version in source file"));
+  } else {
+    slangAssert(version == 1);
   }
 
   // Create a static global destructor if necessary (to handle RS object