1 files changed, 31 insertions, 32 deletions

diff --git a/crates/project_model/src/rustc_cfg.rs b/crates/project_model/src/rustc_cfg.rs
index 6de40cfe2..012eab256 100644
--- a/crates/project_model/src/rustc_cfg.rs
+++ b/crates/project_model/src/rustc_cfg.rs
@@ -2,6 +2,7 @@
 
 use std::process::Command;
 
+use anyhow::Result;
 use paths::AbsPath;
 
 use crate::{cfg_flag::CfgFlag, utf8_stdout};
@@ -18,41 +19,39 @@ pub(crate) fn get(cargo_toml: Option<&AbsPath>, target: Option<&str>) -> Vec<Cfg
         }
     }
 
-    let rustc_cfgs = {
-        cargo_toml
-            .and_then(|cargo_toml| {
-                let mut cargo_config = Command::new(toolchain::cargo());
-                cargo_config.current_dir(cargo_toml.parent().unwrap()).args(&[
-                    "+nightly",
-                    "-Z",
-                    "unstable-options",
-                    "rustc",
-                    "--print",
-                    "cfg",
-                ]);
-                if let Some(target) = target {
-                    cargo_config.args(&["--target", target]);
-                }
-                utf8_stdout(cargo_config).ok()
-            })
-            .map_or_else(
-                || {
-                    // using unstable cargo features failed, fall back to using plain rustc
-                    let mut cmd = Command::new(toolchain::rustc());
-                    cmd.args(&["--print", "cfg", "-O"]);
-                    if let Some(target) = target {
-                        cmd.args(&["--target", target]);
-                    }
-                    utf8_stdout(cmd)
-                },
-                Ok,
-            )
-    };
-
-    match rustc_cfgs {
+    match get_rust_cfgs(cargo_toml, target) {
         Ok(rustc_cfgs) => res.extend(rustc_cfgs.lines().map(|it| it.parse().unwrap())),
         Err(e) => log::error!("failed to get rustc cfgs: {:#}", e),
     }
 
     res
 }
+
+fn get_rust_cfgs(cargo_toml: Option<&AbsPath>, target: Option<&str>) -> Result<String> {
+    let cargo_rust_cfgs = match cargo_toml {
+        Some(cargo_toml) => {
+            let mut cargo_config = Command::new(toolchain::cargo());
+            cargo_config
+                .current_dir(cargo_toml.parent().unwrap())
+                .args(&["-Z", "unstable-options", "rustc", "--print", "cfg"])
+                .env("RUSTC_BOOTSTRAP", "1");
+            if let Some(target) = target {
+                cargo_config.args(&["--target", target]);
+            }
+            utf8_stdout(cargo_config).ok()
+        }
+        None => None,
+    };
+    match cargo_rust_cfgs {
+        Some(stdout) => Ok(stdout),
+        None => {
+            // using unstable cargo features failed, fall back to using plain rustc
+            let mut cmd = Command::new(toolchain::rustc());
+            cmd.args(&["--print", "cfg", "-O"]);
+            if let Some(target) = target {
+                cmd.args(&["--target", target]);
+            }
+            utf8_stdout(cmd)
+        }
+    }
+}