Vendor dependencies

Let's see how I like this workflow.

vendor/tokio/tests/macros_test.rs

@@ -0,0 +1,88 @@
+#![cfg(all(feature = "full", not(tokio_wasi)))] // Wasi doesn't support threading
+
+use tokio::test;
+
+#[test]
+async fn test_macro_can_be_used_via_use() {
+    tokio::spawn(async {}).await.unwrap();
+}
+
+#[tokio::test]
+async fn test_macro_is_resilient_to_shadowing() {
+    tokio::spawn(async {}).await.unwrap();
+}
+
+// https://github.com/tokio-rs/tokio/issues/3403
+#[rustfmt::skip] // this `rustfmt::skip` is necessary because unused_braces does not warn if the block contains newline.
+#[tokio::main]
+pub async fn unused_braces_main() { println!("hello") }
+#[rustfmt::skip] // this `rustfmt::skip` is necessary because unused_braces does not warn if the block contains newline.
+#[tokio::test]
+async fn unused_braces_test() { assert_eq!(1 + 1, 2) }
+
+// https://github.com/tokio-rs/tokio/pull/3766#issuecomment-835508651
+#[std::prelude::v1::test]
+fn trait_method() {
+    trait A {
+        fn f(self);
+    }
+    impl A for () {
+        #[tokio::main]
+        async fn f(self) {}
+    }
+    ().f()
+}
+
+// https://github.com/tokio-rs/tokio/issues/4175
+#[tokio::main]
+pub async fn issue_4175_main_1() -> ! {
+    panic!();
+}
+#[tokio::main]
+pub async fn issue_4175_main_2() -> std::io::Result<()> {
+    panic!();
+}
+#[allow(unreachable_code)]
+#[tokio::test]
+pub async fn issue_4175_test() -> std::io::Result<()> {
+    return Ok(());
+    panic!();
+}
+
+// https://github.com/tokio-rs/tokio/issues/4175
+#[allow(clippy::let_unit_value)]
+pub mod clippy_semicolon_if_nothing_returned {
+    #![deny(clippy::semicolon_if_nothing_returned)]
+
+    #[tokio::main]
+    pub async fn local() {
+        let _x = ();
+    }
+    #[tokio::main]
+    pub async fn item() {
+        fn _f() {}
+    }
+    #[tokio::main]
+    pub async fn semi() {
+        panic!();
+    }
+    #[tokio::main]
+    pub async fn empty() {
+        // To trigger clippy::semicolon_if_nothing_returned lint, the block needs to contain newline.
+    }
+}
+
+// https://github.com/tokio-rs/tokio/issues/5243
+pub mod issue_5243 {
+    macro_rules! mac {
+        (async fn $name:ident() $b:block) => {
+            #[::tokio::test]
+            async fn $name() {
+                $b
+            }
+        };
+    }
+    mac!(
+        async fn foo() {}
+    );
+}