Fix runtime assert when hashing module object (#522)

The blanket `std:#️⃣:Hash` impl for instances of `v8::Data` invokes
`v8::internal::Object::GetHash()` but that crashes for `v8::Module`
objects. Use a custom impl that calls `v8::Module::get_identity_hash()`.

Fixes the following runtime assertion:

    # Fatal error in ../../../v8/src/objects/objects-inl.h, line 1043
    # Debug check failed: object.IsJSReceiver().

Refs: https://github.com/denoland/deno/pull/8354#discussion_r522157813

src/data.rs

@@ -348,7 +348,6 @@ pub struct Module(Opaque);
 impl_deref! { Data for Module }
 impl_try_from! { Data for Module if d => d.is_module() }
 impl_eq! { for Module }
-impl_hash! { for Module }
 impl_partial_eq! { Data for Module use identity }
 impl_partial_eq! { Module for Module use identity }
 

src/module.rs

@@ -1,4 +1,6 @@
 use std::convert::TryInto;
+use std::hash::Hash;
+use std::hash::Hasher;
 use std::mem::MaybeUninit;
 use std::ptr::null;
 
@@ -371,3 +373,9 @@ impl Module {
     .into()
   }
 }
+
+impl Hash for Module {
+  fn hash<H: Hasher>(&self, state: &mut H) {
+    state.write_i32(self.get_identity_hash());
+  }
+}

tests/test_api.rs

@@ -4,8 +4,10 @@
 extern crate lazy_static;
 
 use std::any::type_name;
+use std::collections::hash_map::DefaultHasher;
 use std::convert::{Into, TryFrom, TryInto};
 use std::ffi::c_void;
+use std::hash::Hash;
 use std::ptr::NonNull;
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::Mutex;
@@ -1989,6 +1991,7 @@ fn module_evaluation() {
     assert!(module.is_source_text_module());
     assert!(!module.is_synthetic_module());
     assert_eq!(v8::ModuleStatus::Uninstantiated, module.get_status());
+    module.hash(&mut DefaultHasher::new()); // Should not crash.
 
     let result = module
       .instantiate_module(scope, compile_specifier_as_module_resolve_callback);