Dataflow: Add empty type strengthening predicate for languages without type pruning.

Author: aschackmull

cpp/ql/lib/semmle/code/cpp/dataflow/internal/DataFlowPrivate.qll

@@ -205,6 +205,8 @@ predicate clearsContent(Node n, Content c) {
  */
 predicate expectsContent(Node n, ContentSet c) { none() }
 
+predicate typeStrongerThan(DataFlowType t1, DataFlowType t2) { none() }
+
 /** Gets the type of `n` used for type pruning. */
 Type getNodeType(Node n) {
   suppressUnusedNode(n) and

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/DataFlowPrivate.qll

@@ -753,6 +753,8 @@ predicate clearsContent(Node n, Content c) {
  */
 predicate expectsContent(Node n, ContentSet c) { none() }
 
+predicate typeStrongerThan(DataFlowType t1, DataFlowType t2) { none() }
+
 /** Gets the type of `n` used for type pruning. */
 DataFlowType getNodeType(Node n) {
   suppressUnusedNode(n) and

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

@@ -200,6 +200,8 @@ predicate expectsContent(Node n, ContentSet c) {
   FlowSummaryImpl::Private::Steps::summaryExpectsContent(n, c)
 }
 
+predicate typeStrongerThan(DataFlowType t1, DataFlowType t2) { none() }
+
 /** Gets the type of `n` used for type pruning. */
 DataFlowType getNodeType(Node n) { result = TTodoDataFlowType() and exists(n) }
 

python/ql/lib/semmle/python/dataflow/new/internal/DataFlowPrivate.qll

@@ -502,6 +502,8 @@ class CastNode extends Node {
 pragma[inline]
 predicate compatibleTypes(DataFlowType t1, DataFlowType t2) { any() }
 
+predicate typeStrongerThan(DataFlowType t1, DataFlowType t2) { none() }
+
 /**
  * Gets the type of `node`.
  */

ruby/ql/lib/codeql/ruby/dataflow/internal/DataFlowPrivate.qll

@@ -1231,6 +1231,8 @@ class DataFlowType extends TDataFlowType {
   string toString() { result = "" }
 }
 
+predicate typeStrongerThan(DataFlowType t1, DataFlowType t2) { none() }
+
 /** Gets the type of `n` used for type pruning. */
 DataFlowType getNodeType(NodeImpl n) { result = TTodoDataFlowType() and exists(n) }
 

swift/ql/lib/codeql/swift/dataflow/internal/DataFlowPrivate.qll

@@ -793,6 +793,8 @@ class DataFlowType extends TDataFlowType {
   string toString() { result = "" }
 }
 
+predicate typeStrongerThan(DataFlowType t1, DataFlowType t2) { none() }
+
 /** Gets the type of `n` used for type pruning. */
 DataFlowType getNodeType(NodeImpl n) {
   any() // return the singleton DataFlowType until we support type pruning for Swift