wip

Author: hvitved

shared/dataflow/codeql/dataflow/internal/DataFlowImpl.qll

@@ -2860,7 +2860,8 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
 
       bindingset[c, tail]
       Ap apCons(Content c, Ap tail) {
-        exists(boolean isSingleton | result.getAHead(isSingleton) = c |
+        exists(boolean isSingleton |
+          result.getAHead(isSingleton) = c and
           if tail instanceof ApNil then isSingleton = true else isSingleton = false
         )
       }
@@ -3200,7 +3201,10 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
       override predicate isCons(Content head, AccessPathApprox tail) {
         head = c and
         (
-          exists(Content c2 | Stage4::consCand(c, TFrontHead(c2, _)) |
+          exists(Content c2, boolean isSingleton |
+            Stage4::consCand(c, TFrontHead(c2, isSingleton)) and
+            if len > 2 then isSingleton = false else isSingleton = true
+          |
             tail = TConsCons(c2, _, len - 1)
             or
             len = 2 and
@@ -3543,7 +3547,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
       override predicate isCons(Content head, AccessPath tail) { head = head_ and tail = tail_ }
 
       override AccessPathFrontHead getFront() {
-        if tail_.length() = 0
+        if this.length() = 1
         then result = TFrontHead(head_, true)
         else result = TFrontHead(head_, false)
       }

shared/dataflow/codeql/dataflow/internal/DataFlowImplCommon.qll

@@ -2521,10 +2521,13 @@ module MakeImplCommon<LocationSig Location, InputSig<Location> Lang> {
 
   class ApproxAccessPathFrontHead extends ApproxAccessPathFront, TApproxFrontHead {
     private ContentApprox c;
+    private boolean isSingleton;
 
-    ApproxAccessPathFrontHead() { this = TApproxFrontHead(c, _) }
+    ApproxAccessPathFrontHead() { this = TApproxFrontHead(c, isSingleton) }
 
-    override string toString() { result = c.toString() }
+    override string toString() {
+      if isSingleton = true then result = c.toString() + " (singleton)" else result = c.toString()
+    }
 
     override boolean toBoolNonEmpty() { result = true }
   }
@@ -2561,7 +2564,9 @@ module MakeImplCommon<LocationSig Location, InputSig<Location> Lang> {
 
     AccessPathFrontHead() { this = TFrontHead(c, isSingleton) }
 
-    override string toString() { result = c.toString() }
+    override string toString() {
+      if isSingleton = true then result = c.toString() + " (singleton)" else result = c.toString()
+    }
 
     override ApproxAccessPathFront toApprox() { result.getAHead(isSingleton) = c }
   }