Initial node implementation (#4)

Reviewed-on: #4
Co-authored-by: Zack <zack@bfpower.io>
Co-committed-by: Zack <zack@bfpower.io>

macros/node-poll-variants/tests/generate.rs

@@ -0,0 +1,31 @@
+#![feature(async_fn_in_trait, impl_trait_projections, never_type)]
+
+use node_poll_variants::PollVariants;
+use physical_node::transducer::input::Poll;
+
+#[derive(PollVariants)]
+#[value_type = "SecondT"]
+#[error_type = "!"]
+struct ExamplePoll<'a, FirstT, SecondT>
+where
+    SecondT: Copy,
+{
+    a: &'a i32,
+    b: i32,
+    first: FirstT,
+    second: SecondT,
+}
+
+impl<'a, FirstT, SecondT> Poll for ExamplePoll<'a, FirstT, SecondT>
+where
+    SecondT: Copy,
+{
+    type Value = SecondT;
+    type Error = !;
+
+    async fn poll(&self) -> Result<Self::Value, Self::Error> {
+        Ok(self.second)
+    }
+}
+
+fn main() {}