From 076095b04907091f20ed6a915dbdbb23652d1520 Mon Sep 17 00:00:00 2001
From: Oliver Middleton <olliemail27@gmail.com>
Date: Tue, 7 Jan 2020 23:21:24 +0000
Subject: [PATCH] rustdoc: Don't allow `#![feature(...)]` on stable or beta

(cherry picked from commit 40571995984a0f2c466f77955e7d147887c2179b)
---
 src/librustdoc/core.rs | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index a524801bea6bf..dd2e1144301ec 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -318,8 +318,7 @@ pub fn run_core(options: RustdocOptions) -> (clean::Crate, RenderInfo, RenderOpt
         cg: codegen_options,
         externs,
         target_triple: target,
-        // Ensure that rustdoc works even if rustc is feature-staged
-        unstable_features: UnstableFeatures::Allow,
+        unstable_features: UnstableFeatures::from_environment(),
         actually_rustdoc: true,
         debugging_opts: debugging_options,
         error_format,