Rust: Add test for missing flow through captured variables

Author: hvitved

rust/ql/lib/codeql/rust/controlflow/internal/Scope.qll

@@ -35,7 +35,8 @@ final class CallableScope extends CfgScopeImpl, Callable {
   CallableScope() {
     // A function without a body corresponds to a trait method signature and
     // should not have a CFG scope.
-    this.hasBody()
+    this.hasBody() and
+    this.fromSource() // exclude stubs in tests defined using `additionalExternalFile`
   }
 
   override predicate scopeFirst(AstNode first) {

rust/ql/test/library-tests/dataflow/lambdas/external_file.rs

@@ -0,0 +1,5 @@
+pub fn may_invoke_callback1<F: Fn(i64)>(f: F) {}
+
+pub fn may_invoke_callback2<F: FnOnce(i64)>(f: F) {}
+
+pub fn may_invoke_callback3(f: impl Fn(i64)) {}

rust/ql/test/library-tests/dataflow/lambdas/inline-flow.ext.yml

@@ -0,0 +1,6 @@
+extensions:
+  - addsTo:
+      pack: codeql/rust-all
+      extensible: additionalExternalFile
+    data:
+      - ["external_file.rs"]

rust/ql/test/library-tests/dataflow/lambdas/main.rs

@@ -102,6 +102,16 @@ fn test_apply_wrap() {
     apply_wrap(|x| sink(x), 0);
 }
 
+mod external_file;
+use external_file::*;
+
+fn test_external_call() {
+    let a = source(81);
+    may_invoke_callback1(|x| sink(a)); // $ MISSING: hasValueFlow=81
+    may_invoke_callback2(|x| sink(a)); // $ MISSING: hasValueFlow=81
+    may_invoke_callback3(|x| sink(a)); // $ MISSING: hasValueFlow=81
+}
+
 fn main() {
     closure_flow_out();
     closure_flow_in();