Fix build on wasm32-unknown-unknown

Rust only allows an empty match statement in code that will not be run,
that is when matching something that is not inhabited.

References to enums are always considered inhabited, because it may
avoid some undefined behaviour in unsafe code. See
rust-lang/rust#78123

The solution in this PR is to match the enum rather than the reference
to the enum.

I also added CI for wasm32-unknown-unknown to combat regression.

.github/workflows/ci_test.yml

@@ -47,6 +47,26 @@ jobs:
         with:
           command: test
 
+  wasm32_build:
+    name: Build on wasm32-unknown-unknown
+    steps:
+      - name: Checkout sources
+        uses: actions/checkout@v2
+
+      - name: Install stable toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: stable
+          target: wasm32-unknown-unknown
+          override: true
+
+      - name: Run cargo test
+        uses: actions-rs/cargo@v1
+        with:
+          command: build
+          args: --target wasm32-unknown-unknown
+
   lints:
     name: Lints
     runs-on: ubuntu-latest

src/error.rs

@@ -21,7 +21,7 @@ pub enum CpuFeature {
 impl CpuFeature {
     /// Test if the given CPU feature is detected.
     pub fn is_detected(&self) -> bool {
-        match self {
+        match *self {
             #[cfg(target_arch = "x86_64")]
             CpuFeature::Sse3 => {
                 is_x86_feature_detected!("sse3")
@@ -44,7 +44,7 @@ impl CpuFeature {
 
 impl fmt::Display for CpuFeature {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self {
+        match *self {
             #[cfg(target_arch = "x86_64")]
             CpuFeature::Sse3 => {
                 write!(f, "sse3")