diff --git a/cpp/ql/lib/semmle/code/cpp/dataflow/internal/DataFlowPrivate.qll b/cpp/ql/lib/semmle/code/cpp/dataflow/internal/DataFlowPrivate.qll
index 364359dc9fd..b14979470b0 100644
--- a/cpp/ql/lib/semmle/code/cpp/dataflow/internal/DataFlowPrivate.qll
+++ b/cpp/ql/lib/semmle/code/cpp/dataflow/internal/DataFlowPrivate.qll
@@ -215,19 +215,16 @@ predicate typeStrongerThan(DataFlowType t1, DataFlowType t2) { none() }
 predicate localMustFlowStep(Node node1, Node node2) { none() }
 
 /** Gets the type of `n` used for type pruning. */
-Type getNodeType(Node n) {
+DataFlowType getNodeType(Node n) {
   exists(n) and
   result instanceof VoidType // stub implementation
 }
 
-/** Gets a string representation of a type returned by `getNodeType`. */
-string ppReprType(Type t) { none() } // stub implementation
-
 /**
  * Holds if `t1` and `t2` are compatible, that is, whether data can flow from
  * a node of type `t1` to a node of type `t2`.
  */
-predicate compatibleTypes(Type t1, Type t2) {
+predicate compatibleTypes(DataFlowType t1, DataFlowType t2) {
   t1 instanceof VoidType and t2 instanceof VoidType // stub implementation
 }
 
@@ -243,7 +240,11 @@ class DataFlowCallable extends Function { }
 
 class DataFlowExpr = Expr;
 
-class DataFlowType = Type;
+final private class TypeFinal = Type;
+
+class DataFlowType extends TypeFinal {
+  string toString() { result = "" }
+}
 
 /** A function call relevant for data flow. */
 class DataFlowCall extends Expr instanceof Call {
diff --git a/cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/DataFlowPrivate.qll b/cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/DataFlowPrivate.qll
index 9381eb7f645..ac6e898748a 100644
--- a/cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/DataFlowPrivate.qll
+++ b/cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/DataFlowPrivate.qll
@@ -994,9 +994,6 @@ DataFlowType getNodeType(Node n) {
   result instanceof VoidType // stub implementation
 }
 
-/** Gets a string representation of a type returned by `getNodeType`. */
-string ppReprType(DataFlowType t) { none() } // stub implementation
-
 /**
  * Holds if `t1` and `t2` are compatible, that is, whether data can flow from
  * a node of type `t1` to a node of type `t2`.
@@ -1097,7 +1094,11 @@ class SummarizedCallable extends DataFlowCallable, TSummarizedCallable {
 
 class DataFlowExpr = Expr;
 
-class DataFlowType = Type;
+final private class TypeFinal = Type;
+
+class DataFlowType extends TypeFinal {
+  string toString() { result = "" }
+}
 
 cached
 private newtype TDataFlowCall =
diff --git a/csharp/ql/lib/semmle/code/csharp/dataflow/internal/DataFlowPrivate.qll b/csharp/ql/lib/semmle/code/csharp/dataflow/internal/DataFlowPrivate.qll
index 4ad804e5049..d2307d62fe9 100644
--- a/csharp/ql/lib/semmle/code/csharp/dataflow/internal/DataFlowPrivate.qll
+++ b/csharp/ql/lib/semmle/code/csharp/dataflow/internal/DataFlowPrivate.qll
@@ -2444,9 +2444,6 @@ DataFlowType getNodeType(Node n) {
   ] = result.getADelegateCreation()
 }
 
-/** Gets a string representation of a `DataFlowType`. */
-string ppReprType(DataFlowType t) { result = t.toString() }
-
 private class DataFlowNullType extends Gvn::GvnType {
   DataFlowNullType() { this = Gvn::getGlobalValueNumber(any(NullType nt)) }
 
diff --git a/docs/ql-libraries/dataflow/dataflow.md b/docs/ql-libraries/dataflow/dataflow.md
index 106c055eae0..ff7c71abfae 100644
--- a/docs/ql-libraries/dataflow/dataflow.md
+++ b/docs/ql-libraries/dataflow/dataflow.md
@@ -548,12 +548,9 @@ DataFlowType getNodeType(Node n)
 ```
 and every `Node` should have a type.
 
-One also needs to define the string representation of a `DataFlowType`:
-```ql
-string ppReprType(DataFlowType t)
-```
-The `ppReprType` predicate is used for printing a type in the labels of
-`PathNode`s, this can be defined as `none()` if type pruning is not used.
+One also needs to define the string representation of a `DataFlowType`.
+The `DataFlowType.toString` predicate is used for printing a type in the labels of
+`PathNode`s, this should be defined as `result = ""` if type pruning is not used.
 
 Finally, one must define `CastNode` as a subclass of `Node` as those nodes
 where types should be checked. Usually this will be things like explicit casts.
diff --git a/go/ql/lib/semmle/go/dataflow/internal/DataFlowPrivate.qll b/go/ql/lib/semmle/go/dataflow/internal/DataFlowPrivate.qll
index 2145fc41a05..2fcbf2d350f 100644
--- a/go/ql/lib/semmle/go/dataflow/internal/DataFlowPrivate.qll
+++ b/go/ql/lib/semmle/go/dataflow/internal/DataFlowPrivate.qll
@@ -215,9 +215,6 @@ predicate localMustFlowStep(Node node1, Node node2) { none() }
 /** Gets the type of `n` used for type pruning. */
 DataFlowType getNodeType(Node n) { result = TTodoDataFlowType() and exists(n) }
 
-/** Gets a string representation of a type returned by `getNodeType()`. */
-string ppReprType(DataFlowType t) { none() }
-
 /**
  * Holds if `t1` and `t2` are compatible, that is, whether data can flow from
  * a node of type `t1` to a node of type `t2`.
diff --git a/java/ql/lib/semmle/code/java/dataflow/internal/DataFlowPrivate.qll b/java/ql/lib/semmle/code/java/dataflow/internal/DataFlowPrivate.qll
index e455b8cdb4d..84b31f14e98 100644
--- a/java/ql/lib/semmle/code/java/dataflow/internal/DataFlowPrivate.qll
+++ b/java/ql/lib/semmle/code/java/dataflow/internal/DataFlowPrivate.qll
@@ -356,8 +356,12 @@ RefType getErasedRepr(Type t) {
   t instanceof NullType and result instanceof TypeObject
 }
 
-class DataFlowType extends SrcRefType {
+final private class SrcRefTypeFinal = SrcRefType;
+
+class DataFlowType extends SrcRefTypeFinal {
   DataFlowType() { this = getErasedRepr(_) }
+
+  string toString() { result = ppReprType(this) }
 }
 
 pragma[nomagic]
@@ -371,7 +375,7 @@ DataFlowType getNodeType(Node n) {
 }
 
 /** Gets a string representation of a type returned by `getErasedRepr`. */
-string ppReprType(DataFlowType t) {
+private string ppReprType(SrcRefType t) {
   if t.(BoxedType).getPrimitiveType().getName() = "double"
   then result = "Number"
   else result = t.toString()
diff --git a/python/ql/lib/semmle/python/dataflow/new/internal/DataFlowPrivate.qll b/python/ql/lib/semmle/python/dataflow/new/internal/DataFlowPrivate.qll
index 38436d99e14..218dbdae302 100644
--- a/python/ql/lib/semmle/python/dataflow/new/internal/DataFlowPrivate.qll
+++ b/python/ql/lib/semmle/python/dataflow/new/internal/DataFlowPrivate.qll
@@ -534,7 +534,7 @@ newtype TDataFlowType = TAnyFlow()
 
 class DataFlowType extends TDataFlowType {
   /** Gets a textual representation of this element. */
-  string toString() { result = "DataFlowType" }
+  string toString() { result = "" }
 }
 
 /** A node that performs a type cast. */
@@ -578,9 +578,6 @@ DataFlowType getNodeType(Node node) {
   exists(node)
 }
 
-/** Gets a string representation of a type returned by `getErasedRepr`. */
-string ppReprType(DataFlowType t) { none() }
-
 //--------
 // Extra flow
 //--------
diff --git a/ruby/ql/lib/codeql/ruby/dataflow/internal/DataFlowPrivate.qll b/ruby/ql/lib/codeql/ruby/dataflow/internal/DataFlowPrivate.qll
index 7bde4c8f9ac..6fef4d1222c 100644
--- a/ruby/ql/lib/codeql/ruby/dataflow/internal/DataFlowPrivate.qll
+++ b/ruby/ql/lib/codeql/ruby/dataflow/internal/DataFlowPrivate.qll
@@ -2077,9 +2077,6 @@ DataFlowType getNodeType(Node n) {
   result = TUnknownDataFlowType()
 }
 
-/** Gets a string representation of a `DataFlowType`. */
-string ppReprType(DataFlowType t) { none() }
-
 pragma[inline]
 private predicate compatibleTypesNonSymRefl(DataFlowType t1, DataFlowType t2) {
   t1 != TUnknownDataFlowType() and
diff --git a/shared/dataflow/codeql/dataflow/DataFlow.qll b/shared/dataflow/codeql/dataflow/DataFlow.qll
index 6d6a08d3718..bbde158b8a6 100644
--- a/shared/dataflow/codeql/dataflow/DataFlow.qll
+++ b/shared/dataflow/codeql/dataflow/DataFlow.qll
@@ -124,8 +124,6 @@ signature module InputSig<LocationSig Location> {
     string toString();
   }
 
-  string ppReprType(DataFlowType t);
-
   /**
    * Holds if `t1` and `t2` are compatible types.
    *
diff --git a/shared/dataflow/codeql/dataflow/internal/DataFlowImpl.qll b/shared/dataflow/codeql/dataflow/internal/DataFlowImpl.qll
index df081d02175..f293834d3d7 100644
--- a/shared/dataflow/codeql/dataflow/internal/DataFlowImpl.qll
+++ b/shared/dataflow/codeql/dataflow/internal/DataFlowImpl.qll
@@ -3445,9 +3445,11 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
 
       AccessPathApproxConsNil() { this = TConsNil(c, t) }
 
+      private string ppTyp() { result = t.toString() and result != "" }
+
       override string toString() {
-        // The `concat` becomes "" if `ppReprType` has no result.
-        result = "[" + c.toString() + "]" + concat(" : " + ppReprType(t))
+        // The `concat` becomes "" if `ppTyp` has no result.
+        result = "[" + c.toString() + "]" + concat(" : " + this.ppTyp())
       }
 
       override Content getHead() { result = c }
@@ -3668,7 +3670,9 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
 
       ParamNodeEx getParamNode() { result = p }
 
-      override string toString() { result = p + concat(" : " + ppReprType(t)) + " " + ap }
+      private string ppTyp() { result = t.toString() and result != "" }
+
+      override string toString() { result = p + concat(" : " + this.ppTyp()) + " " + ap }
 
       Location getLocation() { result = p.getLocation() }
     }
@@ -3935,10 +3939,12 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
 
       override int length() { result = 1 + tail_.length() }
 
+      private string ppTyp() { result = t.toString() and result != "" }
+
       private string toStringImpl(boolean needsSuffix) {
         tail_ = TAccessPathNil() and
         needsSuffix = false and
-        result = head_.toString() + "]" + concat(" : " + ppReprType(t))
+        result = head_.toString() + "]" + concat(" : " + this.ppTyp())
         or
         result = head_ + ", " + tail_.(AccessPathCons).toStringImpl(needsSuffix)
         or
@@ -4087,9 +4093,8 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
       private string ppType() {
         this instanceof PathNodeSink and result = ""
         or
-        exists(DataFlowType t | t = this.(PathNodeMid).getType() |
-          // The `concat` becomes "" if `ppReprType` has no result.
-          result = concat(" : " + ppReprType(t))
+        exists(string t | t = this.(PathNodeMid).getType().toString() |
+          if t = "" then result = "" else result = " : " + t
         )
       }
 
@@ -5402,9 +5407,8 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
           private string ppType() {
             this instanceof PartialPathNodeRev and result = ""
             or
-            exists(DataFlowType t | t = this.(PartialPathNodeFwd).getType() |
-              // The `concat` becomes "" if `ppReprType` has no result.
-              result = concat(" : " + ppReprType(t))
+            exists(string t | t = this.(PartialPathNodeFwd).getType().toString() |
+              if t = "" then result = "" else result = " : " + t
             )
           }
 
diff --git a/swift/ql/lib/codeql/swift/dataflow/internal/DataFlowPrivate.qll b/swift/ql/lib/codeql/swift/dataflow/internal/DataFlowPrivate.qll
index 5abc652b3b4..c84298771fb 100644
--- a/swift/ql/lib/codeql/swift/dataflow/internal/DataFlowPrivate.qll
+++ b/swift/ql/lib/codeql/swift/dataflow/internal/DataFlowPrivate.qll
@@ -1310,9 +1310,6 @@ DataFlowType getNodeType(Node n) {
   any() // return the singleton DataFlowType until we support type pruning for Swift
 }
 
-/** Gets a string representation of a `DataFlowType`. */
-string ppReprType(DataFlowType t) { none() }
-
 /**
  * Holds if `t1` and `t2` are compatible, that is, whether data can flow from
  * a node of type `t1` to a node of type `t2`.