Merge pull request github#16819 from owen-mc/go/remove-dataflowtype-optimizer-bug-workaround

Go: Make DataFlowType a singleton (remove workaround)

Author: owen-mc

go/ql/lib/semmle/go/dataflow/internal/DataFlowPrivate.qll

@@ -246,9 +246,7 @@ predicate neverSkipInPathGraph(Node n) {
 
 class DataFlowExpr = Expr;
 
-private newtype TDataFlowType =
-  TTodoDataFlowType() or
-  TTodoDataFlowType2() // Add a dummy value to prevent bad functionality-induced joins arising from a type of size 1.
+private newtype TDataFlowType = TTodoDataFlowType()
 
 class DataFlowType extends TDataFlowType {
   /** Gets a textual representation of this element. */