Rust: Mark SSA data flow nodes in output and hide them in paths

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

@@ -180,12 +180,9 @@ module Node {
 
     SsaImpl::DefinitionExt getDefinitionExt() { result = def }
 
-    /** Holds if this node should be hidden from path explanations. */
-    abstract predicate isHidden();
-
     override Location getLocation() { result = node.getLocation() }
 
-    override string toString() { result = node.toString() }
+    override string toString() { result = "[SSA] " + node.toString() }
   }
 
   /** A data flow node that represents a value returned by a callable. */
@@ -318,7 +315,7 @@ module RustDataFlow implements InputSig<Location> {
 
   DataFlowType getNodeType(Node node) { any() }
 
-  predicate nodeIsHidden(Node node) { none() }
+  predicate nodeIsHidden(Node node) { node instanceof Node::SsaNode }
 
   class DataFlowExpr = ExprCfgNode;
 

rust/ql/test/library-tests/dataflow/local/DataFlowStep.expected

@@ -1,24 +1,24 @@
-| main.rs:2:9:2:9 | s | main.rs:3:33:3:33 | s |
-| main.rs:6:18:6:21 | cond | main.rs:9:16:9:19 | cond |
-| main.rs:7:9:7:9 | a | main.rs:10:9:10:9 | a |
-| main.rs:8:9:8:9 | b | main.rs:12:9:12:9 | b |
-| main.rs:9:9:9:9 | c | main.rs:14:5:14:5 | c |
+| main.rs:2:9:2:9 | [SSA] s | main.rs:3:33:3:33 | s |
+| main.rs:6:18:6:21 | [SSA] cond | main.rs:9:16:9:19 | cond |
+| main.rs:7:9:7:9 | [SSA] a | main.rs:10:9:10:9 | a |
+| main.rs:8:9:8:9 | [SSA] b | main.rs:12:9:12:9 | b |
+| main.rs:9:9:9:9 | [SSA] c | main.rs:14:5:14:5 | c |
 | main.rs:9:21:11:5 | BlockExpr | main.rs:9:13:13:5 | IfExpr |
 | main.rs:10:9:10:9 | a | main.rs:9:21:11:5 | BlockExpr |
 | main.rs:11:12:13:5 | BlockExpr | main.rs:9:13:13:5 | IfExpr |
 | main.rs:12:9:12:9 | b | main.rs:11:12:13:5 | BlockExpr |
 | main.rs:14:5:14:5 | c | main.rs:6:37:15:1 | BlockExpr |
-| main.rs:18:9:18:9 | a | main.rs:20:15:20:15 | a |
-| main.rs:19:9:19:9 | b | main.rs:22:5:22:5 | b |
+| main.rs:18:9:18:9 | [SSA] a | main.rs:20:15:20:15 | a |
+| main.rs:19:9:19:9 | [SSA] b | main.rs:22:5:22:5 | b |
 | main.rs:20:9:20:15 | BreakExpr | main.rs:19:13:21:5 | LoopExpr |
 | main.rs:20:15:20:15 | a | main.rs:20:9:20:15 | BreakExpr |
 | main.rs:22:5:22:5 | b | main.rs:17:29:23:1 | BlockExpr |
-| main.rs:27:5:27:5 | i | main.rs:27:5:27:5 | i |
-| main.rs:27:5:27:5 | i | main.rs:28:5:28:5 | i |
+| main.rs:27:5:27:5 | [SSA] i | main.rs:28:5:28:5 | i |
+| main.rs:27:5:27:5 | i | main.rs:27:5:27:5 | [SSA] i |
 | main.rs:28:5:28:5 | i | main.rs:25:24:29:1 | BlockExpr |
-| main.rs:31:21:31:21 | a | main.rs:33:20:33:20 | a |
-| main.rs:31:29:31:29 | b | main.rs:34:17:34:17 | b |
-| main.rs:31:37:31:37 | c | main.rs:32:11:32:11 | c |
+| main.rs:31:21:31:21 | [SSA] a | main.rs:33:20:33:20 | a |
+| main.rs:31:29:31:29 | [SSA] b | main.rs:34:17:34:17 | b |
+| main.rs:31:37:31:37 | [SSA] c | main.rs:32:11:32:11 | c |
 | main.rs:32:5:35:5 | MatchExpr | main.rs:31:60:36:1 | BlockExpr |
 | main.rs:33:20:33:20 | a | main.rs:32:5:35:5 | MatchExpr |
 | main.rs:34:17:34:17 | b | main.rs:32:5:35:5 | MatchExpr |