[Bug]: test failures about beam

[dahlbaek]

Following the stack trace, the issue appears to be incorrectly specified typing related to TypedKeyExtractor. The empty option occurs at a call to downcast_ref

beam/sdks/rust/src/internals/serialize.rs

Line 108 in 4bfdd26

let typed_kv = kv.downcast_ref::<(String, V)>().unwrap();

It seems the type of V is expected to be inferred by the compiler here

beam/sdks/rust/src/tests/primitives_test.rs

Line 88 in 4bfdd26

.apply(GroupByKey::default())

I'll be happy to look into this.

[laysakura]

@dahlbaek I assigned this issue to you!

[dahlbaek]

The immediate issue was downcasting to tuple in a few places where the actual type was KV. On top of that, incorrect use of Mutex in

beam/sdks/rust/src/internals/serialize.rs

Lines 15 to 16 in 4bfdd26

	let name = format!("object{}", SERIALIZED_FNS.lock().unwrap().len());
	SERIALIZED_FNS.lock().unwrap().insert(name.to_string(), obj);

caused tests to fail spuriously.

[laysakura]

Closed via #7