Rust: Add test with wrong generated model

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

@@ -31,6 +31,20 @@ enum MyPosEnum {
     B(i64),
 }
 
+// has a manual flow model with flow from second argument to the return value
+// and a wrong generated model with flow from first argument to the return value
+fn snd(a: i64, b: i64) -> i64 {
+    0
+}
+
+fn test_snd() {
+    let s1 = source(99);
+    sink(snd(0, s1)); // $ hasValueFlow=99
+
+    let s2 = source(88);
+    sink(snd(s2, 0)); // $ SPURIOUS: hasValueFlow=88
+}
+
 // has a flow model
 fn get_var_pos(e: MyPosEnum) -> i64 {
     0

rust/ql/test/library-tests/dataflow/models/models.ext.yml

@@ -20,6 +20,9 @@ extensions:
       extensible: summaryModel
     data:
       - ["main::coerce", "Argument[0]", "ReturnValue", "taint", "manual"]
+      - ["main::snd", "Argument[1]", "ReturnValue", "value", "manual"]
+      # Wrong generated model which should not take effect due to the manual model above
+      - ["main::snd", "Argument[0]", "ReturnValue", "value", "dfc-generated"]
       - ["main::get_var_pos", "Argument[0].Field[main::MyPosEnum::A(0)]", "ReturnValue", "value", "manual"]
       - ["main::set_var_pos", "Argument[0]", "ReturnValue.Field[main::MyPosEnum::B(0)]", "value", "manual"]
       - ["main::get_var_field", "Argument[0].Field[main::MyFieldEnum::C::field_c]", "ReturnValue", "value", "manual"]