Repace the CI script with one I'm more familiar with.

.github/actions/install-rust/README.md

@@ -0,0 +1,18 @@
+# install-rust
+
+A small github action to install `rustup` and a Rust toolchain. This is
+generally expressed inline, but it was repeated enough in this repository it
+seemed worthwhile to extract.
+
+Some gotchas:
+
+* Can't `--self-update` on Windows due to permission errors (a bug in Github
+  Actions)
+* `rustup` isn't installed on macOS (a bug in Github Actions)
+
+When the above are fixed we should delete this action and just use this inline:
+
+```yml
+- run: rustup update $toolchain && rustup default $toolchain
+  shell: bash
+```

.github/actions/install-rust/action.yml

@@ -0,0 +1,12 @@
+name: 'Install Rust toolchain'
+description: 'Install both `rustup` and a Rust toolchain'
+
+inputs:
+  toolchain:
+    description: 'Default toolchan to install'
+    required: false
+    default: 'stable'
+
+runs:
+  using: node16
+  main: 'main.js'

.github/actions/install-rust/main.js

@@ -0,0 +1,36 @@
+const child_process = require('child_process');
+const toolchain = process.env.INPUT_TOOLCHAIN;
+const fs = require('fs');
+
+function set_env(name, val) {
+  fs.appendFileSync(process.env['GITHUB_ENV'], `${name}=${val}\n`)
+}
+
+// Needed for now to get 1.24.2 which fixes a bug in 1.24.1 that causes issues
+// on Windows.
+if (process.platform === 'win32') {
+  child_process.execFileSync('rustup', ['self', 'update']);
+}
+
+child_process.execFileSync('rustup', ['set', 'profile', 'minimal']);
+child_process.execFileSync('rustup', ['update', toolchain, '--no-self-update']);
+child_process.execFileSync('rustup', ['default', toolchain]);
+
+// Deny warnings on CI to keep our code warning-free as it lands in-tree. Don't
+// do this on nightly though since there's a fair amount of warning churn there.
+if (!toolchain.startsWith('nightly')) {
+  set_env("RUSTFLAGS", "-D warnings");
+}
+
+// Save disk space by avoiding incremental compilation, and also we don't use
+// any caching so incremental wouldn't help anyway.
+set_env("CARGO_INCREMENTAL", "0");
+
+// Turn down debuginfo from 2 to 1 to help save disk space
+set_env("CARGO_PROFILE_DEV_DEBUG", "1");
+set_env("CARGO_PROFILE_TEST_DEBUG", "1");
+
+if (process.platform === 'darwin') {
+  set_env("CARGO_PROFILE_DEV_SPLIT_DEBUGINFO", "unpacked");
+  set_env("CARGO_PROFILE_TEST_SPLIT_DEBUGINFO", "unpacked");
+}

.github/workflows/main.yml

@@ -1,83 +1,107 @@
-on: [push, pull_request]
-
 name: CI
 
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+
 jobs:
+  rustfmt:
+    name: Rustfmt
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+      with:
+        submodules: true
+    - uses: ./.github/actions/install-rust
+      with:
+        toolchain: stable
+    - run: cargo fmt --all -- --check
+
   check:
     name: Check
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        build: [ubuntu-latest, windows-latest, macos-latest]
+        build: [stable, nightly]
         include:
-          - build: ubuntu-latest
+          - build: stable
             os: ubuntu-latest
-          - build: windows-latest
-            os: windows-latest
-          - build: macos-latest
-            os: macos-latest
-        rust:
-          - stable
-    steps:
-      - uses: actions/checkout@v3
-      - uses: actions-rs/toolchain@v1
-        with:
-          profile: minimal
-          toolchain: ${{ matrix.rust }}
-          override: true
-      - uses: actions-rs/cargo@v1
-        with:
-          command: check
+            rust: stable
+          - build: nightly
+            os: ubuntu-latest
+            rust: nightly
 
-  test:
-    name: Test Suite
+    env:
+      # -D warnings is commented out in our install-rust action; re-add it here.
+      RUSTFLAGS: -D warnings
+    steps:
+    - uses: actions/checkout@v3
+      with:
+        submodules: true
+    - uses: ./.github/actions/install-rust
+      with:
+        toolchain: ${{ matrix.rust }}
+
+    - run: rustup target add x86_64-apple-darwin wasm32-unknown-unknown
+    - run: cargo check --workspace --release -vv --target=x86_64-apple-darwin
+    - run: cargo check --workspace --release -vv --target=wasm32-unknown-unknown
+
+  check_nightly:
+    name: Check on Rust nightly
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        build: [ubuntu-latest, ubuntu-18.04, windows-latest, macos-latest]
+        build: [nightly]
         include:
-          - build: ubuntu-latest
+          - build: nightly
             os: ubuntu-latest
-          - build: ubuntu-18.04
-            os: ubuntu-18.04
-          - build: windows-latest
-            os: windows-latest
-          - build: macos-latest
-            os: macos-latest
-        rust:
-          - nightly
-          - stable
-          - 1.48.0
-        exclude:
-          - build: macos-latest
-            rust: 1.48.0
-    steps:
-      - uses: actions/checkout@v3
-      - uses: actions-rs/toolchain@v1
-        with:
-          profile: minimal
-          toolchain: ${{ matrix.rust }}
-          override: true
-      - uses: actions-rs/cargo@v1
-        with:
-          command: test
+            rust: nightly
 
-  fmt:
-    name: Rustfmt
-    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+      with:
+        submodules: true
+    - uses: ./.github/actions/install-rust
+      with:
+        toolchain: ${{ matrix.rust }}
+    - run: >
+        rustup target add
+        wasm32-wasi
+    - run: cargo check --workspace --release -vv --target=wasm32-wasi
+
+  test:
+    name: Test
+    runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        rust:
-          - stable
+        build: [ubuntu-nightly, windows-nightly, ubuntu-stable, windows-stable, macos-nightly, macos-stable]
+        include:
+          - build: ubuntu-nightly
+            os: ubuntu-latest
+            rust: nightly
+          - build: windows-nightly
+            os: windows-latest
+            rust: nightly
+          - build: macos-nightly
+            os: macos-latest
+            rust: nightly
+          - build: ubuntu-stable
+            os: ubuntu-latest
+            rust: stable
+          - build: windows-stable
+            os: windows-latest
+            rust: stable
+          - build: macos-stable
+            os: macos-latest
+            rust: stable
+
     steps:
-      - uses: actions/checkout@v3
-      - uses: actions-rs/toolchain@v1
-        with:
-          profile: minimal
-          toolchain: ${{ matrix.rust }}
-          override: true
-      - run: rustup component add rustfmt
-      - uses: actions-rs/cargo@v1
-        with:
-          command: fmt
-          args: --all -- --check
+    - uses: actions/checkout@v3
+      with:
+        submodules: true
+    - uses: ./.github/actions/install-rust
+      with:
+        toolchain: ${{ matrix.rust }}
+    - run: cargo test --workspace