JS: Do not include type in path explanation

Author: asgerf

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

@@ -301,7 +301,7 @@ newtype TDataFlowType =
   TAnyType()
 
 class DataFlowType extends TDataFlowType {
-  string toString() {
+  string toDebugString() {
     this instanceof TFunctionType and
     result =
       "TFunctionType(" + this.asFunction().toString() + ") at line " +
@@ -310,6 +310,10 @@ class DataFlowType extends TDataFlowType {
     this instanceof TAnyType and result = "TAnyType"
   }
 
+  string toString() {
+    result = "" // Must be the empty string to prevent this from showing up in path explanations
+  }
+
   Function asFunction() { this = TFunctionType(result) }
 }