From f9386d9c996093f209cf0637cbf1e3e93d87d048 Mon Sep 17 00:00:00 2001
From: Eric Huss <eric@huss.org>
Date: Sat, 8 Apr 2023 10:54:43 -0700
Subject: [PATCH] Check for toolchains names with slashes and use the slow path
 in that case.

---
 src/cargo/util/config/mod.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/cargo/util/config/mod.rs b/src/cargo/util/config/mod.rs
index c93699c33637..79b11e74e0b8 100644
--- a/src/cargo/util/config/mod.rs
+++ b/src/cargo/util/config/mod.rs
@@ -1664,6 +1664,11 @@ impl Config {
                 //
                 // First, we must be running under rustup in the first place.
                 let toolchain = self.get_env_os("RUSTUP_TOOLCHAIN")?;
+                // This currently does not support toolchain paths.
+                // This also enforces UTF-8.
+                if toolchain.to_str()?.contains(&['/', '\\']) {
+                    return None;
+                }
                 // If the tool on PATH is the same as `rustup` on path, then
                 // there is pretty good evidence that it will be a proxy.
                 let tool_resolved = paths::resolve_executable(Path::new(tool)).ok()?;