JS: Add ssaDefHasSource.

Author: aschackmull

javascript/ql/lib/semmle/javascript/dataflow/internal/sharedlib/Ssa.qll

@@ -56,6 +56,11 @@ module SsaDataflowInput implements DataFlowIntegrationInputSig {
     predicate hasCfgNode(js::BasicBlock bb, int i) { this = bb.getNode(i) }
   }
 
+  predicate ssaDefHasSource(WriteDefinition def) {
+    // This library only handles use-use flow after a post-update, there are no definitions, only uses.
+    none()
+  }
+
   predicate ssaDefAssigns(WriteDefinition def, Expr value) {
     // This library only handles use-use flow after a post-update, there are no definitions, only uses.
     none()