Rust: Remove unnecessary edges.

Author: geoffw0

rust/ql/src/queries/security/CWE-696/BadCtorInitialization.ql

@@ -40,16 +40,17 @@ class StdCall extends Expr {
 class PathElement = AstNode;
 
 query predicate edges(PathElement pred, PathElement succ) {
-  // starting edge
+  // starting edge (`#[ctor]` / `#[dtor]` attribute to call)
   exists(CtorAttr ctor, Function f, CallExprBase call |
     f.getAnAttr() = ctor and
     call.getEnclosingCallable() = f and
-    pred = ctor and // source
-    succ = call // flow or sink node
+    pred = ctor and
+    succ = call
   )
   or
-  // transitive edge
+  // transitive edge (call to call)
   exists(Function f |
+    edges(_, pred) and
     pred.(CallExprBase).getStaticTarget() = f and
     succ.(CallExprBase).getEnclosingCallable() = f
   )

rust/ql/test/query-tests/security/CWE-696/BadCTorInitialization.expected

@@ -50,7 +50,5 @@ edges
 | test.rs:147:5:147:20 | call_target3_1(...) | test.rs:126:9:126:16 | stderr(...) |
 | test.rs:147:5:147:20 | call_target3_1(...) | test.rs:126:9:126:44 | ... .write_all(...) |
 | test.rs:151:1:151:7 | Attr | test.rs:153:5:153:12 | bad3_3(...) |
-| test.rs:157:5:157:20 | call_target3_1(...) | test.rs:126:9:126:16 | stderr(...) |
-| test.rs:157:5:157:20 | call_target3_1(...) | test.rs:126:9:126:44 | ... .write_all(...) |
 | test.rs:169:1:169:7 | Attr | test.rs:171:5:171:15 | ... .write(...) |
 | test.rs:169:1:169:7 | Attr | test.rs:171:5:171:15 | ...::stdout(...) |