Vendor dependencies

Let's see how I like this workflow.

vendor/tokio/tests/io_read_to_end.rs

@@ -0,0 +1,78 @@
+#![warn(rust_2018_idioms)]
+#![cfg(feature = "full")]
+
+use std::pin::Pin;
+use std::task::{Context, Poll};
+use tokio::io::{AsyncRead, AsyncReadExt, ReadBuf};
+use tokio_test::assert_ok;
+
+#[tokio::test]
+async fn read_to_end() {
+    let mut buf = vec![];
+    let mut rd: &[u8] = b"hello world";
+
+    let n = assert_ok!(rd.read_to_end(&mut buf).await);
+    assert_eq!(n, 11);
+    assert_eq!(buf[..], b"hello world"[..]);
+}
+
+#[derive(Copy, Clone, Debug)]
+enum State {
+    Initializing,
+    JustFilling,
+    Done,
+}
+
+struct UninitTest {
+    num_init: usize,
+    state: State,
+}
+
+impl AsyncRead for UninitTest {
+    fn poll_read(
+        self: Pin<&mut Self>,
+        _cx: &mut Context<'_>,
+        buf: &mut ReadBuf<'_>,
+    ) -> Poll<std::io::Result<()>> {
+        let me = Pin::into_inner(self);
+        let real_num_init = buf.initialized().len() - buf.filled().len();
+        assert_eq!(real_num_init, me.num_init, "{:?}", me.state);
+
+        match me.state {
+            State::Initializing => {
+                buf.initialize_unfilled_to(me.num_init + 2);
+                buf.advance(1);
+                me.num_init += 1;
+
+                if me.num_init == 24 {
+                    me.state = State::JustFilling;
+                }
+            }
+            State::JustFilling => {
+                buf.advance(1);
+                me.num_init -= 1;
+
+                if me.num_init == 15 {
+                    // The buffer is resized on next call.
+                    me.num_init = 0;
+                    me.state = State::Done;
+                }
+            }
+            State::Done => { /* .. do nothing .. */ }
+        }
+
+        Poll::Ready(Ok(()))
+    }
+}
+
+#[tokio::test]
+async fn read_to_end_uninit() {
+    let mut buf = Vec::with_capacity(64);
+    let mut test = UninitTest {
+        num_init: 0,
+        state: State::Initializing,
+    };
+
+    test.read_to_end(&mut buf).await.unwrap();
+    assert_eq!(buf.len(), 33);
+}