From 85119d744162792a2ff81fda26f34340a7d7eb24 Mon Sep 17 00:00:00 2001
From: Eliza Weisman <eliza@buoyant.io>
Date: Mon, 16 Aug 2021 10:20:55 -0700
Subject: [PATCH] chore: don't check benches on MSRV

Currently, CI runs `cargo check --all --bins --tests --benches` on our
MSRV. This is failing, because the latest `criterion` version now
depends on a revision of `bitflags` that doesn't build on Rust 1.42.0
(due to `const fn`s not being const on 1.42.0).

We *could* solve this by bumping our MSRV to a version where the
appropriate functions are `const fn`, or we could use a `=` dependency
to pin to a specific older version of `bitflags` that compiles on
1.42.0. However, both of these solutions seem kind of unfortunate.

This commit just removes the `--benches` from the MSRV `cargo check`
run. The benchmarks are an internal development tool, not an officially
supported part of `tracing`. Users on 1.42.0 can still depend on
`tracing` and use it in their code even if the benchmarks don't compile
on their (fairly old) Rust version. Therefore, it should be fine to just
remove the benchmarks from the MSRV check.

I split the MSRV and stable `cargo check` jobs into separate jobs, so we
still check that commits don't break the benchmarks on stable Rust.

Signed-off-by: Eliza Weisman <eliza@buoyant.io>
---
 .github/workflows/CI.yml | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index a7a77b62a7..a5ff6b6f45 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -7,17 +7,32 @@ on:
   pull_request: {}
 
 jobs:
+  check-msrv:
+    # Run `cargo check` on our minimum supported Rust version (1.42.0).
+    runs-on: ubuntu-latest
+    rust: 1.42.0
+    steps:
+    - uses: actions/checkout@main
+    - uses: actions-rs/toolchain@v1
+      with:
+        toolchain: 1.42.0
+        profile: minimal
+        override: true
+    - name: Check
+      uses: actions-rs/cargo@v1
+      with:
+        command: check
+        args: --all --bins --tests
+
   check:
     # Run `cargo check` first to ensure that the pushed code at least compiles.
     runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        rust: [stable, 1.42.0]
+    rust: stable
     steps:
     - uses: actions/checkout@main
     - uses: actions-rs/toolchain@v1
       with:
-        toolchain: ${{ matrix.rust }}
+        toolchain: stable
         profile: minimal
         override: true
     - name: Check