Add CI check for compile tests

Create a script `contrib/compile-tests.sh` the checks that all crates in
`tests/compiletests/` do compile if in `pass/` and fail to compile if in
`fail/`

Add a CI step to run the script

.github/workflows/README.md

@@ -24,3 +24,4 @@ Run from rust.yml unless stated otherwise. Unfortunately we are now exceeding th
 10. `Arch32bit`
 11. `Cross`
 12. `Format`
+13. `Compile tests`

.github/workflows/rust.yaml

@@ -218,3 +218,14 @@ jobs:
         run: rustup component add rustfmt
       - name: "Check formatting"
         run: cargo +nightly fmt --all -- --check
+
+  Compile:
+    name: Compile tests
+    runs-on: ubuntu-latest
+    steps:
+      - name: "Checkout repo"
+        uses: actions/checkout@v4
+      - name: "Select toolchain"
+        uses: dtolnay/rust-toolchain@stable
+      - name: "Run compile tests"
+        run: ./contrib/compile-tests.sh

contrib/compile-tests.sh

@@ -0,0 +1,51 @@
+#!/bin/bash
+
+should_pass() {
+    all_passed=true
+    # All crates in the subdirectory pass/ must compile
+    for dir in pass/*; do
+        if [ -d "$dir" ]; then
+            pushd "$dir" > /dev/null
+            if ! cargo run > /dev/null 2>&1; then
+                echo "compiletests/$dir/ failed to compile"
+                all_passed=false
+            fi
+            popd > /dev/null
+        fi
+    done
+    if [ "$all_passed" = true ]; then
+        return 0
+    else
+        return 1
+    fi
+}
+
+should_fail() {
+    all_failed=true
+    # All crates in the subdirectory fail/ must fail to compile
+    for dir in fail/*; do
+        if [ -d "$dir" ]; then
+            pushd "$dir" > /dev/null
+            if cargo run > /dev/null 2>&1; then
+                echo "compiletests/$dir/ compiled when it should not have"
+                all_failed=false
+            fi
+            popd > /dev/null
+        fi
+    done
+    if [ "$all_failed" = true ]; then
+        return 0
+    else
+        return 1
+    fi
+}
+
+# Check that all files in compiletests pass or fail as expected
+cd tests/compiletests
+if should_pass && should_fail; then
+    echo "Compile tests passed"
+    exit 0
+else
+    echo "Compile tests failed"
+    exit 1
+fi