Merge pull request #271 from dtolnay/provider

impl std::any::Provider for anyhow::Error

Author: dtolnay

build.rs

@@ -17,7 +17,7 @@ compile_error! {
 const PROBE: &str = r#"
     #![feature(error_generic_member_access, provide_any)]
 
-    use std::any::Demand;
+    use std::any::{Demand, Provider};
     use std::backtrace::{Backtrace, BacktraceStatus};
     use std::error::Error;
     use std::fmt::{self, Display};
@@ -39,6 +39,12 @@ const PROBE: &str = r#"
         }
     }
 
+    struct P;
+
+    impl Provider for P {
+        fn provide<'a>(&'a self, _demand: &mut Demand<'a>) {}
+    }
+
     const _: fn() = || {
         let backtrace: Backtrace = Backtrace::capture();
         let status: BacktraceStatus = backtrace.status();

src/error.rs

@@ -522,15 +522,16 @@ impl Error {
             Some(addr.cast::<E>().deref_mut())
         }
     }
+}
 
+#[cfg(backtrace)]
+impl std::any::Provider for Error {
     // Called by thiserror when you have `#[source] anyhow::Error`. This provide
     // implementation includes the anyhow::Error's Backtrace if any, unlike
     // deref'ing to dyn Error where the provide implementation would include
     // only the original error's Backtrace from before it got wrapped into an
     // anyhow::Error.
-    #[cfg(backtrace)]
-    #[doc(hidden)]
-    pub fn provide<'a>(&'a self, demand: &mut Demand<'a>) {
+    fn provide<'a>(&'a self, demand: &mut Demand<'a>) {
         unsafe { ErrorImpl::provide(self.inner.by_ref(), demand) }
     }
 }