Rust: Hide internal implementation details from DataFlow::Node

Author: hvitved

rust/ql/lib/codeql/rust/dataflow/DataFlow.qll

@@ -4,6 +4,7 @@
  */
 
 private import rust
+private import codeql.rust.controlflow.CfgNodes
 private import codeql.dataflow.DataFlow
 private import internal.DataFlowImpl as DataFlowImpl
 private import DataFlowImpl::Node as Node
@@ -13,7 +14,24 @@ private import DataFlowImpl::Node as Node
  * (inter-procedural) data flow analyses.
  */
 module DataFlow {
-  final class Node = Node::Node;
+  /** An element, viewed as a node in a data flow graph. */
+  final class Node instanceof Node::Node {
+    /** Gets the location of this node. */
+    Location getLocation() { result = super.getLocation() }
+
+    /** Gets a textual representation of this node. */
+    string toString() { result = super.toString() }
+
+    /**
+     * Gets the expression that corresponds to this node, if any.
+     */
+    ExprCfgNode asExpr() { result = super.asExpr() }
+
+    /**
+     * Gets the pattern that corresponds to this node, if any.
+     */
+    PatCfgNode asPat() { result = super.asPat() }
+  }
 
   /**
    * The value of a parameter at function entry, viewed as a node in a data
@@ -24,7 +42,18 @@ module DataFlow {
     ParamBase getParameter() { result = super.getParameter().getParamBase() }
   }
 
-  final class PostUpdateNode = Node::PostUpdateNode;
+  /**
+   * A node associated with an object after an operation that might have
+   * changed its state.
+   *
+   * This can be either the argument to a callable after the callable returns
+   * (which might have mutated the argument), or the qualifier of a field after
+   * an update to the field.
+   */
+  final class PostUpdateNode extends Node instanceof Node::PostUpdateNode {
+    /** Gets the node before the state update. */
+    Node getPreUpdateNode() { result = super.getPreUpdateNode() }
+  }
 
   final class Content = DataFlowImpl::Content;
 

rust/ql/lib/codeql/rust/dataflow/internal/DataFlowImpl.qll

@@ -129,10 +129,7 @@ private predicate isArgumentForCall(ExprCfgNode arg, CallExprBaseCfgNode call, P
 }
 
 module Node {
-  /**
-   * An element, viewed as a node in a data flow graph. Either an expression
-   * (`ExprNode`) or a parameter (`ParameterNode`).
-   */
+  /** An element, viewed as a node in a data flow graph. */
   abstract class Node extends TNode {
     /** Gets the location of this node. */
     abstract Location getLocation();
@@ -150,6 +147,11 @@ module Node {
      */
     PatCfgNode asPat() { none() }
 
+    /**
+     * Gets the SSA definition that corresponds to this node, if any.
+     */
+    Ssa::Definition asDefinition() { none() }
+
     /** Gets the enclosing callable. */
     DataFlowCallable getEnclosingCallable() { result = TCfgScope(this.getCfgScope()) }
 
@@ -160,11 +162,6 @@ module Node {
      * Gets the control flow node that corresponds to this data flow node.
      */
     CfgNode getCfgNode() { none() }
-
-    /**
-     * Gets this node's underlying SSA definition, if any.
-     */
-    Ssa::Definition asDefinition() { none() }
   }
 
   /** A node type that is not implemented. */

rust/ql/lib/utils/test/InlineFlowTest.qll

@@ -22,9 +22,9 @@ private predicate callTargetName(CallExprCfgNode call, string name) {
 }
 
 private module FlowTestImpl implements InputSig<Location, RustDataFlow> {
-  predicate defaultSource(DataFlow::Node source) { callTargetName(source.asExpr(), "source") }
+  predicate defaultSource(RustDataFlow::Node source) { callTargetName(source.asExpr(), "source") }
 
-  predicate defaultSink(DataFlow::Node sink) {
+  predicate defaultSink(RustDataFlow::Node sink) {
     any(CallExprCfgNode call | callTargetName(call, "sink")).getArgument(_) = sink.asExpr()
   }
 
@@ -40,7 +40,7 @@ private module FlowTestImpl implements InputSig<Location, RustDataFlow> {
   }
 
   bindingset[src, sink]
-  string getArgString(DataFlow::Node src, DataFlow::Node sink) {
+  string getArgString(RustDataFlow::Node src, RustDataFlow::Node sink) {
     (
       result = getSourceArgString(src)
       or