Add benchmark highlighting the costs of failed calls to FromPyObject:…

…:extract.

benches/bench_frompyobject.rs

@@ -1,6 +1,6 @@
-use criterion::{criterion_group, criterion_main, Bencher, Criterion};
+use criterion::{black_box, criterion_group, criterion_main, Bencher, Criterion};
 
-use pyo3::{prelude::*, types::PyString};
+use pyo3::{prelude::*, types::{PyList, PyString}};
 
 #[derive(FromPyObject)]
 enum ManyTypes {
@@ -18,8 +18,73 @@ fn enum_from_pyobject(b: &mut Bencher<'_>) {
     })
 }
 
+fn list_via_cast_as(b: &mut Bencher<'_>) {
+    Python::with_gil(|py| {
+        let any: &PyAny = PyList::empty(py).into();
+
+        b.iter(|| {
+            let _list: &PyList = black_box(any).cast_as().unwrap();
+        });
+    })
+}
+
+fn list_via_extract(b: &mut Bencher<'_>) {
+    Python::with_gil(|py| {
+        let any: &PyAny = PyList::empty(py).into();
+
+        b.iter(|| {
+            let _list: &PyList = black_box(any).extract().unwrap();
+        });
+    })
+}
+
+fn not_a_list_via_cast_as(b: &mut Bencher<'_>) {
+    Python::with_gil(|py| {
+        let any: &PyAny = PyString::new(py, "foobar").into();
+
+        b.iter(|| {
+            black_box(any).cast_as::<PyList>().unwrap_err();
+        });
+    })
+}
+
+fn not_a_list_via_extract(b: &mut Bencher<'_>) {
+    Python::with_gil(|py| {
+        let any: &PyAny = PyString::new(py, "foobar").into();
+
+        b.iter(|| {
+            black_box(any).extract::<&PyList>().unwrap_err();
+        });
+    })
+}
+
+#[derive(FromPyObject)]
+enum ListOrNotList<'a> {
+    List(&'a PyList),
+    NotList(&'a PyAny),
+}
+
+fn not_a_list_via_extract_enum(b: &mut Bencher<'_>) {
+    Python::with_gil(|py| {
+        let any: &PyAny = PyString::new(py, "foobar").into();
+
+        b.iter(|| {
+            match black_box(any).extract::<ListOrNotList<'_>>() {
+                Ok(ListOrNotList::List(_list)) => panic!(),
+                Ok(ListOrNotList::NotList(_any)) => (),
+                Err(_) => panic!(),
+            }
+        });
+    })
+}
+
 fn criterion_benchmark(c: &mut Criterion) {
     c.bench_function("enum_from_pyobject", enum_from_pyobject);
+    c.bench_function("list_via_cast_as", list_via_cast_as);
+    c.bench_function("list_via_extract", list_via_extract);
+    c.bench_function("not_a_list_via_cast_as", not_a_list_via_cast_as);
+    c.bench_function("not_a_list_via_extract", not_a_list_via_extract);
+    c.bench_function("not_a_list_via_extract_enum", not_a_list_via_extract_enum);
 }
 
 criterion_group!(benches, criterion_benchmark);