Repro incorrect StarlarkTypeRepr::Canonical for StarlarkValue

Summary:
Because the implementation is incorrect, `ValueOfUnchecked::cast` does not work for `StarlarkValue` parameters.

`non_static_type_id`  is provided by David Tolnay [here](rrevenantt/better_any#8 (comment)).

Reviewed By: JakobDegen

Differential Revision: D59600076

fbshipit-source-id: 967de23f9690e0050c7c1854c13e590706833943

Author: stepancheg

starlark/src/util.rs

@@ -16,4 +16,5 @@
  */
 
 pub(crate) mod arc_or_static;
+pub(crate) mod non_static_type_id;
 pub(crate) mod rtabort;

starlark/src/util/non_static_type_id.rs

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2018 The Starlark in Rust Authors.
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#![cfg(test)]
+
+use std::any::TypeId;
+use std::marker::PhantomData;
+use std::mem;
+
+pub(crate) fn non_static_type_id<T: ?Sized>() -> TypeId {
+    trait NonStaticAny {
+        fn get_type_id(&self) -> TypeId
+        where
+            Self: 'static;
+    }
+
+    impl<T: ?Sized> NonStaticAny for PhantomData<T> {
+        fn get_type_id(&self) -> TypeId
+        where
+            Self: 'static,
+        {
+            TypeId::of::<T>()
+        }
+    }
+
+    let phantom_data = PhantomData::<T>;
+    NonStaticAny::get_type_id(unsafe {
+        mem::transmute::<&dyn NonStaticAny, &(dyn NonStaticAny + 'static)>(&phantom_data)
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use std::any::TypeId;
+
+    use crate::util::non_static_type_id::non_static_type_id;
+
+    #[test]
+    fn test_non_static_type_id() {
+        assert_eq!(non_static_type_id::<&str>(), TypeId::of::<&'static str>());
+    }
+}

starlark/src/values/type_repr.rs

@@ -138,3 +138,21 @@ pub fn type_repr_from_attr_impl<'v, T: StarlarkTypeRepr>(
 ) -> Ty {
     T::starlark_type_repr()
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::util::TestComplexValue;
+    use crate::util::non_static_type_id::non_static_type_id;
+    use crate::values::type_repr::StarlarkTypeRepr;
+    use crate::values::FrozenValue;
+    use crate::values::Value;
+
+    #[test]
+    fn test_canonical_for_complex_value() {
+        // TODO(nga): `StarlarkTypeRepr::Canonical` should be equal.
+        assert_ne!(
+            non_static_type_id::<<TestComplexValue<Value> as StarlarkTypeRepr>::Canonical>(),
+            non_static_type_id::<<TestComplexValue<FrozenValue> as StarlarkTypeRepr>::Canonical>(),
+        );
+    }
+}