From edecb26ff325e1c905022e0f27dcfe1cb6187c07 Mon Sep 17 00:00:00 2001
From: Greg Wiley <aztec.rex@jammm.com>
Date: Sat, 5 Nov 2022 20:34:08 -0700
Subject: [PATCH] Fix compile issues in wasm-beep example (#723)

Fixes #721

Changes to a dependency library broke compilation of the example. Changes needed to get the example working and warning-free include:

1. specifying additional type constraints in local implementations
2. using the `FromSample` trait to convert samples in the handler
3. adding a default matcher in response to the non-exhaustive attribute on `SampleFormat`

Also adds a github action to ensure the wasm-beep example compiles.
---
 .github/workflows/cpal.yml    | 14 ++++++++++++++
 examples/wasm-beep/src/lib.rs |  8 +++++---
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/cpal.yml b/.github/workflows/cpal.yml
index eaf606e..c39eeef 100644
--- a/.github/workflows/cpal.yml
+++ b/.github/workflows/cpal.yml
@@ -313,3 +313,17 @@ jobs:
     - name: Build iphonesimulator feedback example
       run: cd examples/ios-feedback && xcodebuild -scheme cpal-ios-example -configuration Debug -derivedDataPath build -sdk iphonesimulator
 
+  wasm-beep-build:
+    # this only confirms that the Rust source builds
+    # and checks to prevent regressions like #721.
+    #
+    # It does not test the javascript/web integration
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install Target
+        run: rustup target add wasm32-unknown-unknown
+      - name: Cargo Build
+        working-directory: ./examples/wasm-beep
+        run: cargo build --target wasm32-unknown-unknown
+
diff --git a/examples/wasm-beep/src/lib.rs b/examples/wasm-beep/src/lib.rs
index 0308650..301329d 100644
--- a/examples/wasm-beep/src/lib.rs
+++ b/examples/wasm-beep/src/lib.rs
@@ -38,12 +38,13 @@ pub fn beep() -> Handle {
         cpal::SampleFormat::F32 => run::<f32>(&device, &config.into()),
         cpal::SampleFormat::I16 => run::<i16>(&device, &config.into()),
         cpal::SampleFormat::U16 => run::<u16>(&device, &config.into()),
+        _ => panic!("unsupported sample format"),
     })
 }
 
 fn run<T>(device: &cpal::Device, config: &cpal::StreamConfig) -> Stream
 where
-    T: cpal::Sample,
+    T: cpal::Sample + cpal::SizedSample + cpal::FromSample<f32>,
 {
     let sample_rate = config.sample_rate.0 as f32;
     let channels = config.channels as usize;
@@ -71,10 +72,11 @@ where
 
 fn write_data<T>(output: &mut [T], channels: usize, next_sample: &mut dyn FnMut() -> f32)
 where
-    T: cpal::Sample,
+    T: cpal::Sample + cpal::FromSample<f32>,
 {
     for frame in output.chunks_mut(channels) {
-        let value: T = cpal::Sample::from::<f32>(&next_sample());
+        let sample = next_sample();
+        let value = T::from_sample::<f32>(sample);
         for sample in frame.iter_mut() {
             *sample = value;
         }