Rust: Make fixes in data flow based on PR feedback

Author: paldepind

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

@@ -96,7 +96,7 @@ module Node {
   final class ArgumentNode = NaNode;
 
   /** An SSA node. */
-  abstract class SsaNode extends Node, TSsaNode {
+  class SsaNode extends Node, TSsaNode {
     SsaImpl::DataFlowIntegration::SsaNode node;
     SsaImpl::DefinitionExt def;
 

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

@@ -469,10 +469,7 @@ private module DataFlowIntegrationInput implements Impl::DataFlowIntegrationInpu
 
   /** Holds if SSA definition `def` assigns `value` to the underlying variable. */
   predicate ssaDefAssigns(WriteDefinition def, Expr value) {
-    exists(BasicBlock bb, int i |
-      def.definesAt(_, bb, i) and
-      value.getAstNode() = bb.getNode(i).getAstNode().(AssignmentExpr).getRhs()
-    )
+    exists(BasicBlock bb, int i | def.definesAt(_, bb, i) and value = bb.getNode(i))
   }
 
   class Parameter = Param;

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

@@ -1,12 +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: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: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: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: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 |