Add environment variable tracking in places where it was convenient

This won't work with Cargo's change tracking, but it should work with incremental.

Author: madsmtm

compiler/rustc_borrowck/src/nll.rs

@@ -1,9 +1,9 @@
 //! The entry point of the NLL borrow checker.
 
+use std::io;
 use std::path::PathBuf;
 use std::rc::Rc;
 use std::str::FromStr;
-use std::{env, io};
 
 use polonius_engine::{Algorithm, Output};
 use rustc_index::IndexSlice;
@@ -163,8 +163,8 @@ pub(crate) fn compute_regions<'a, 'tcx>(
 
         if polonius_output {
             let algorithm =
-                env::var("POLONIUS_ALGORITHM").unwrap_or_else(|_| String::from("Hybrid"));
-            let algorithm = Algorithm::from_str(&algorithm).unwrap();
+                infcx.tcx.env_var("POLONIUS_ALGORITHM").unwrap_or_else(|_| "Hybrid".as_ref());
+            let algorithm = Algorithm::from_str(algorithm).unwrap();
             debug!("compute_regions: using polonius algorithm {:?}", algorithm);
             let _prof_timer = infcx.tcx.prof.generic_activity("polonius_analysis");
             Some(Box::new(Output::compute(polonius_facts, algorithm, false)))

compiler/rustc_lint/src/non_local_def.rs

@@ -104,8 +104,10 @@ impl<'tcx> LateLintPass<'tcx> for NonLocalDefinitions {
         // determining if we are in a doctest context can't currently be determined
         // by the code itself (there are no specific attributes), but fortunately rustdoc
         // sets a perma-unstable env var for libtest so we just reuse that for now
-        let is_at_toplevel_doctest =
-            || self.body_depth == 2 && std::env::var("UNSTABLE_RUSTDOC_TEST_PATH").is_ok();
+        let is_at_toplevel_doctest = || {
+            self.body_depth == 2
+                && cx.tcx.env_var_os("UNSTABLE_RUSTDOC_TEST_PATH".as_ref()).is_some()
+        };
 
         match item.kind {
             ItemKind::Impl(impl_) => {