From cd642e18937e66ca66e00905a44514c6eba7e6cc Mon Sep 17 00:00:00 2001
From: bjorn3 <bjorn3@users.noreply.github.com>
Date: Thu, 5 Aug 2021 17:15:22 +0200
Subject: [PATCH] Update error message

Co-authored-by: Josh Triplett <josh@joshtriplett.org>
---
 src/cargo/util/toml/mod.rs | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/cargo/util/toml/mod.rs b/src/cargo/util/toml/mod.rs
index 618f5ff37..42851b9d4 100644
--- a/src/cargo/util/toml/mod.rs
+++ b/src/cargo/util/toml/mod.rs
@@ -566,10 +566,11 @@ impl TomlProfile {
 
         if let Some(codegen_backend) = &self.codegen_backend {
             features.require(Feature::codegen_backend())?;
-            if codegen_backend.contains('.') {
+            if codegen_backend.contains(|c| !c.is_ascii_alphanumeric() && c != '_') {
                 bail!(
-                    "`profile.{}.codegen-backend` is an external backend, but only builtin codegen \
-                    backends are allowed."
+                    "`profile.{}.codegen-backend` setting of `{}` is not a valid backend name.",
+                    name,
+                    codegen_backend,
                 );
             }
         }