Assert Send/Sync/Unpin for all public types (#2323)

Author: taiki-e

.github/workflows/ci.yml

@@ -94,14 +94,27 @@ jobs:
       # Check thread-pool feature (futures, futures-executor)
       - run: cargo hack build -p futures -p futures-executor --no-default-features --features std,thread-pool
 
-  build:
+  async-await-msrv:
     name: cargo +${{ matrix.rust }} build
     strategy:
       matrix:
         rust:
           # This is the minimum Rust version supported by `async-await` feature.
           # When updating this, the reminder to update the minimum required version of `async-await` feature in README.md.
           - 1.39.0
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install Rust
+        run: rustup update ${{ matrix.rust }} && rustup default ${{ matrix.rust }}
+      - run: cargo install cargo-hack
+      - run: cargo hack build --workspace --no-dev-deps
+
+  build:
+    name: cargo +${{ matrix.rust }} build
+    strategy:
+      matrix:
+        rust:
           - stable
           - beta
           - nightly

futures/Cargo.toml

@@ -25,12 +25,13 @@ futures-sink = { path = "../futures-sink", version = "0.3.12", default-features
 futures-util = { path = "../futures-util", version = "0.3.12", default-features = false, features = ["sink"] }
 
 [dev-dependencies]
-pin-utils = "0.1.0"
 futures-executor = { path = "../futures-executor", features = ["thread-pool"] }
 futures-test = { path = "../futures-test" }
-tokio = "0.1.11"
 assert_matches = "1.3.0"
 pin-project = "1.0.1"
+pin-utils = "0.1.0"
+static_assertions = "1"
+tokio = "0.1.11"
 
 [features]
 default = ["std", "async-await", "executor"]