From a611197f85a7e3b111aa358ad6a076121d5aa66e Mon Sep 17 00:00:00 2001
From: Wim Looman <wim@nemo157.com>
Date: Mon, 9 Dec 2019 17:30:47 +0100
Subject: [PATCH 1/2] Remove `-Z install-upgrade` for cargo-hack

This is now the default since
https://github.com/rust-lang/cargo/pull/7560
---
 .travis.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.travis.yml b/.travis.yml
index db964a30fd..c19dd2c310 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -129,7 +129,7 @@ matrix:
     - name: cargo check (features)
       rust: nightly
       install:
-        - cargo install -Z install-upgrade cargo-hack
+        - cargo install cargo-hack
       script:
         # Check each specified feature works properly
         # * `--each-feature` - run for each feature which includes --no-default-features and default features of package

From f57d91ae43ae9ad4e0cbcd32c9ba3e1cafdb7519 Mon Sep 17 00:00:00 2001
From: Wim Looman <wim@nemo157.com>
Date: Mon, 9 Dec 2019 18:00:36 +0100
Subject: [PATCH 2/2] Add allow(unreachable_code) for usage of try_join with
 the never type

Fixes #1992
---
 futures-macro/src/join.rs |  4 ++++
 futures/tests/try_join.rs | 23 +++++++++++++++++++++++
 2 files changed, 27 insertions(+)
 create mode 100644 futures/tests/try_join.rs

diff --git a/futures-macro/src/join.rs b/futures-macro/src/join.rs
index aaedc3e3ec..93b5a28cec 100644
--- a/futures-macro/src/join.rs
+++ b/futures-macro/src/join.rs
@@ -129,6 +129,8 @@ pub(crate) fn try_join(input: TokenStream) -> TokenStream {
             } else if unsafe { #futures_crate::core_reexport::pin::Pin::new_unchecked(&mut #fut) }.output_mut().unwrap().is_err() {
                 // `.err().unwrap()` rather than `.unwrap_err()` so that we don't introduce
                 // a `T: Debug` bound.
+                // Also, for an error type of ! any code after `err().unwrap()` is unreachable.
+                #[allow(unreachable_code)]
                 return #futures_crate::core_reexport::task::Poll::Ready(
                     #futures_crate::core_reexport::result::Result::Err(
                         unsafe { #futures_crate::core_reexport::pin::Pin::new_unchecked(&mut #fut) }.take_output().unwrap().err().unwrap()
@@ -141,6 +143,8 @@ pub(crate) fn try_join(input: TokenStream) -> TokenStream {
         quote! {
             // `.ok().unwrap()` rather than `.unwrap()` so that we don't introduce
             // an `E: Debug` bound.
+            // Also, for an ok type of ! any code after `ok().unwrap()` is unreachable.
+            #[allow(unreachable_code)]
             unsafe { #futures_crate::core_reexport::pin::Pin::new_unchecked(&mut #fut) }.take_output().unwrap().ok().unwrap(),
         }
     });
diff --git a/futures/tests/try_join.rs b/futures/tests/try_join.rs
new file mode 100644
index 0000000000..a148657288
--- /dev/null
+++ b/futures/tests/try_join.rs
@@ -0,0 +1,23 @@
+#![deny(unreachable_code)]
+
+use futures::{try_join, executor::block_on};
+
+#[test]
+fn try_join_never_error() {
+    block_on(async {
+        let future1 = async { Ok::<(), !>(()) };
+        let future2 = async { Ok::<(), !>(()) };
+        try_join!(future1, future2)
+    })
+    .unwrap();
+}
+
+#[test]
+fn try_join_never_ok() {
+    block_on(async {
+        let future1 = async { Err::<!, ()>(()) };
+        let future2 = async { Err::<!, ()>(()) };
+        try_join!(future1, future2)
+    })
+    .unwrap_err();
+}