Dataflow: Address review comments.

Author: aschackmull

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

@@ -1369,6 +1369,12 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
 
         CcCall ccSomeCall();
 
+        /*
+         * The following `instanceof` predicates are necessary for proper
+         * caching, since we're able to cache predicates, but not the underlying
+         * types.
+         */
+
         predicate instanceofCc(Cc cc);
 
         predicate instanceofCcCall(CcCall cc);

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

@@ -502,7 +502,7 @@ module MakeImplCommon<LocationSig Location, InputSig<Location> Lang> {
       )
     }
 
-    private module CallSetsInput implements MkSetsInp {
+    private module CallSetsInput implements MkSetsInputSig {
       class Key = TCallEdge;
 
       class Value = DataFlowCall;
@@ -523,7 +523,7 @@ module MakeImplCommon<LocationSig Location, InputSig<Location> Lang> {
 
     private class CallSet = CallSetOption::Option;
 
-    private module DispatchSetsInput implements MkSetsInp {
+    private module DispatchSetsInput implements MkSetsInputSig {
       class Key = TCallEdge;
 
       class Value = TCallEdge;
@@ -585,10 +585,11 @@ module MakeImplCommon<LocationSig Location, InputSig<Location> Lang> {
      *
      * There are four cases:
      * - `TAnyCallContext()` : No restrictions on method flow.
-     * - `TSpecificCall(DataFlowCall call)` : Flow entered through the
-     *    given `call`. This call improves the set of viable
-     *    dispatch targets for at least one method call in the current callable
-     *    or helps prune unreachable nodes in the current callable.
+     * - `TSpecificCall(CallSet calls, DispatchSet tgts, UnreachableSetOption unreachable)` :
+     *    Flow entered through a specific call that improves the set of viable
+     *    dispatch targets for all of `calls` to the set of dispatch targets in
+     *    `tgts`, and/or the specific call prunes unreachable nodes in the
+     *    current callable as given by `unreachable`.
      * - `TSomeCall()` : Flow entered through a parameter. The
      *    originating call does not improve the set of dispatch targets for any
      *    method call in the current callable and was therefore not recorded.
@@ -1498,7 +1499,7 @@ module MakeImplCommon<LocationSig Location, InputSig<Location> Lang> {
     cached
     int callOrder(DataFlowCall call) { result = call.totalorder() }
 
-    private module UnreachableSetsInput implements MkSetsInp {
+    private module UnreachableSetsInput implements MkSetsInputSig {
       class Key = TCallEdge;
 
       class Value = NodeRegion;

shared/util/codeql/util/internal/MakeSets.qll

@@ -5,7 +5,7 @@
  */
 
 /** The input signature for `MakeSets`. */
-signature module MkSetsInp {
+signature module MkSetsInputSig {
   class Key;
 
   class Value;
@@ -31,7 +31,7 @@ signature module MkSetsInp {
  * reasonable fallback where `getValueSet(k).contains(v)` remains equivalent to
  * `v = getAValue(k)`.
  */
-module MakeSets<MkSetsInp Inp> {
+module MakeSets<MkSetsInputSig Inp> {
   private import Inp
 
   private int totalorderExt(Value v) {
@@ -53,7 +53,7 @@ module MakeSets<MkSetsInp Inp> {
   private newtype TValList =
     TValListNil() or
     TValListCons(Value head, int r, TValList tail) { hasValListCons(_, head, r, tail) } or
-    TValListUnordered(Key k) { exists(getAValue(k)) and unordered(k) }
+    TValListUnordered(Key k) { unordered(k) }
 
   private predicate hasValListCons(Key k, Value head, int r, TValList tail) {
     rankedValue(k, head, r) and