Rust: Add type inference test

Author: hvitved

rust/ql/test/library-tests/type-inference/main.rs

@@ -2740,6 +2740,7 @@ mod blanket_impl;
 mod closure;
 mod dereference;
 mod dyn_type;
+mod regressions;
 
 fn main() {
     field_access::f(); // $ target=f

rust/ql/test/library-tests/type-inference/regressions.rs

@@ -0,0 +1,34 @@
+mod regression1 {
+
+    pub struct S<T>(T);
+
+    pub enum E {
+        V { vec: Vec<E> },
+    }
+
+    impl<T> From<S<T>> for Option<T> {
+        fn from(s: S<T>) -> Self {
+            Some(s.0) // $ fieldof=S
+        }
+    }
+
+    pub fn f() -> E {
+        let mut vec_e = Vec::new(); // $ target=new
+        let mut opt_e = None;
+
+        let e = E::V { vec: Vec::new() }; // $ target=new
+
+        if let Some(e) = opt_e {
+            vec_e.push(e); // $ target=push
+        }
+        opt_e = e.into(); // $ target=into
+
+        #[rustfmt::skip]
+        let _ = if let Some(last) = vec_e.pop() // $ target=pop
+        {
+            opt_e = last.into(); // $ target=into
+        };
+
+        opt_e.unwrap() // $ target=unwrap
+    }
+}