From a7598fa4de47e5077361f9981b088632343833d2 Mon Sep 17 00:00:00 2001
From: Eliza Weisman <eliza@buoyant.io>
Date: Mon, 17 Aug 2020 10:32:51 -0700
Subject: [PATCH 1/2] attributes: remove use of non-MSRV-compliant
 `Option::flatten`

PR #875 added code to `tracing-attributes` that uses `Option::flatten`,
which was only added to the standard library in Rust 1.40. This broke
our MSRV, but we missed it because the MSRV CI checks weren't working
correctly (fixed in #934).

This commit removes the use of `Option::flatten`, and replaces it with a
manual implementation. It's a little less pretty, but it builds on our
MSRV (1.39.0).
---
 tracing-attributes/src/lib.rs | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/tracing-attributes/src/lib.rs b/tracing-attributes/src/lib.rs
index c40afe374b..18181c9aad 100644
--- a/tracing-attributes/src/lib.rs
+++ b/tracing-attributes/src/lib.rs
@@ -929,8 +929,11 @@ fn get_async_trait_info(block: &Block, block_is_async: bool) -> Option<AsyncTrai
 
             None
         })
-        .next()
-        .flatten();
+        .next();
+    let self_type = match self_type {
+        Some(x) => x,
+        None => None,
+    };
 
     Some(AsyncTraitInfo {
         name: fun.sig.ident.to_string(),

From f9861b708b49522713154fd432cf74eede7b71fd Mon Sep 17 00:00:00 2001
From: Eliza Weisman <eliza@buoyant.io>
Date: Mon, 17 Aug 2020 10:36:37 -0700
Subject: [PATCH 2/2] examples: disable `opentelemetry`'s default features

The `opentelemetry` crate depends on `prometheus`, which depends on
`protobuf`, a crate which doesn't compile on our MSRV (Rust 1.39). This
was missed due to issues with the MSRV CI checks, which will be fixed
fixed in #934. Therefore, once the MSRV checks work properly, the
`protobuf` dependency will break our builds.

We don't _need_ the `opentelemetry/metrics` feature, which is what
enables the `prometheus` (and thus `protobuf`) dependency.
`tracing-opentelemetry` already has a `default-features = false`
dependency on `opentelemetry`, but the examples don't. Therefore, I've
changed the examples crate to disable `opentelemetry`'s default features
as well.
---
 examples/Cargo.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/examples/Cargo.toml b/examples/Cargo.toml
index 80d5405ce5..7c9cb0be6b 100644
--- a/examples/Cargo.toml
+++ b/examples/Cargo.toml
@@ -52,5 +52,5 @@ inferno = "0.10.0"
 tempdir = "0.3.7"
 
 # opentelemetry example
-opentelemetry = "0.8"
+opentelemetry = { version = "0.8", default-features = false, features = ["trace"] }
 opentelemetry-jaeger = "0.7"