build: vendor Rust crate dependencies

third_party/crates/anyhow-1.0.104/src/nightly.rs

@@ -0,0 +1,58 @@
+// This code exercises the surface area that we expect of the Error generic
+// member access API. If the current toolchain is able to compile it, then
+// anyhow is able to provide backtrace support.
+
+#![cfg_attr(anyhow_build_probe, feature(error_generic_member_access))]
+
+use core::error::{self, Error};
+use std::backtrace::Backtrace;
+
+pub use core::error::Request;
+
+#[cfg(anyhow_build_probe)]
+const _: () = {
+    use core::fmt::{self, Debug, Display};
+
+    struct MyError(Backtrace);
+
+    impl Debug for MyError {
+        fn fmt(&self, _formatter: &mut fmt::Formatter) -> fmt::Result {
+            unimplemented!()
+        }
+    }
+
+    impl Display for MyError {
+        fn fmt(&self, _formatter: &mut fmt::Formatter) -> fmt::Result {
+            unimplemented!()
+        }
+    }
+
+    impl Error for MyError {
+        fn provide<'a>(&'a self, request: &mut Request<'a>) {
+            provide_ref_backtrace(request, &self.0);
+        }
+    }
+};
+
+// Include in sccache cache key.
+#[cfg(anyhow_build_probe)]
+const _: Option<&str> = option_env!("RUSTC_BOOTSTRAP");
+
+pub fn request_ref_backtrace(err: &dyn Error) -> Option<&Backtrace> {
+    request_ref::<Backtrace>(err)
+}
+
+fn request_ref<'a, T>(err: &'a (impl Error + ?Sized)) -> Option<&'a T>
+where
+    T: 'static + ?Sized,
+{
+    error::request_ref::<T>(err)
+}
+
+pub fn provide_ref_backtrace<'a>(request: &mut Request<'a>, backtrace: &'a Backtrace) {
+    Request::provide_ref(request, backtrace);
+}
+
+pub fn provide<'a>(err: &'a (impl Error + ?Sized), request: &mut Request<'a>) {
+    Error::provide(err, request);
+}