[rs] impl std error for Error

Relies more on the source() of error for informative messages

wgpu/src/backend/direct.rs

@@ -1410,7 +1410,9 @@ where
     fn unwrap_error_sink(self, error_sink: &ErrorSink, fallback: impl FnOnce() -> T) -> T {
         self.unwrap_or_else(|err| {
             let error_sink = error_sink.lock();
-            error_sink.handle_error(crate::Error::from(err));
+            error_sink.handle_error(crate::Error::ValidationError {
+                source: Box::new(err),
+            });
             fallback()
         })
     }
@@ -1418,12 +1420,6 @@ where
 
 type ErrorSink = Arc<Mutex<ErrorSinkRaw>>;
 
-impl<E: Error + Send + Sync + 'static> From<E> for crate::Error {
-    fn from(err: E) -> Self {
-        crate::Error::ValidationError { source: err.into() }
-    }
-}
-
 struct ErrorSinkRaw {
     uncaptured_handler: Box<dyn crate::UncapturedErrorHandler>,
 }
@@ -1446,6 +1442,17 @@ impl Debug for ErrorSinkRaw {
 }
 
 fn default_error_handler(err: crate::Error) {
-    eprintln!("WGPU Error: {}", err);
+    eprintln!("wgpu error: {}\n", err);
+
+    if err.source().is_some() {
+        eprintln!("Caused by:");
+        let mut source_opt = err.source();
+        while let Some(source) = source_opt {
+            eprintln!("    {}", source);
+            source_opt = source.source();
+        }
+        eprintln!();
+    }
+
     panic!("Handling wgpu errors as fatal by default");
 }

wgpu/src/lib.rs

@@ -2636,11 +2636,21 @@ pub enum Error {
         source: Box<dyn error::Error + Send + Sync + 'static>,
     },
 }
+
+impl error::Error for Error {
+    fn source(&self) -> Option<&(dyn error::Error + 'static)> {
+        match self {
+            Error::OutOfMemoryError => None,
+            Error::ValidationError { source } => Some(source.as_ref()),
+        }
+    }
+}
+
 impl Display for Error {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
             Error::OutOfMemoryError => f.write_str("Out of Memory"),
-            Error::ValidationError { source } => std::fmt::Display::fmt(source, f),
+            Error::ValidationError { .. } => f.write_str("Validation error"),
         }
     }
 }