Check build with the MSRV declared in Cargo.toml

.github/workflows/test.yml

@@ -73,3 +73,24 @@ jobs:
           SNAPSHOT_DIR: rust-${{ matrix.toolchain }}
         with:
           command: test
+
+  msrv-build:
+    name: Build crate with documented MSRV
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout source code
+        uses: actions/checkout@v2
+
+      - name: Install Rust MSRV version
+        run: scripts/force-msrv-toolchain.sh
+
+      - name: Install Rust
+        uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+
+      - name: Build
+        uses: actions-rs/cargo@v1
+        with:
+          command: build

.gitignore

@@ -12,3 +12,6 @@ Cargo.lock
 .idea
 
 *.new
+
+# Ignore toolchain installed by script
+rust-toolchain

scripts/force-msrv-toolchain.sh

@@ -0,0 +1,16 @@
+#! /bin/sh
+#
+# Force the use of the MSRV toolchain (for use with the CI).
+# Since action-rs/toolchain@v1 uses rustup 1.21.x, only the
+# toolchain name can be given in the file.
+#
+# If you call this script in your working directory, do not
+# forget that it will create a "rust-toolchain" file there.
+
+set -e
+
+root=$(dirname "$0")/..
+
+version=$(sed -ne 's/rust-version *= *"\(.*\)"/\1/p' "$root"/Cargo.toml)
+echo $version > "$root"/rust-toolchain
+echo "Rust $version installed as the forced toolchain"