Rollup merge of #22383 - pnkfelix:pass-features-along-during-expansion, r=huonw

 Pass features along during expansion

Use the set of passed features to detect uses of feature-gated macros without the corresponding feature enabled.

Fix #22234.

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Also, the framework this add (passing along a reference to the features in the expansion context) is a necessary precursor for landing a properly feature-gated desugaring-based overloaded-`box` and placement-`in` (#22181).

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This is fixing a bug, but since there might be code out there that is unknowingly taking advantage of that bug, I feel obligated to mark this as a:

[breaking-change]

1 files changed, 2 insertions, 1 deletions

diff --git a/src/librustc_driver/driver.rs b/src/librustc_driver/driver.rs
index eb1dba7159c..728ff647599 100644
--- a/src/librustc_driver/driver.rs
+++ b/src/librustc_driver/driver.rs
@@ -471,9 +471,10 @@ pub fn phase_2_configure_and_expand(sess: &Session,
                 new_path.extend(env::split_paths(&_old_path));
                 env::set_var("PATH", &env::join_paths(new_path.iter()).unwrap());
             }
+            let features = sess.features.borrow();
             let cfg = syntax::ext::expand::ExpansionConfig {
                 crate_name: crate_name.to_string(),
-                enable_quotes: sess.features.borrow().quote,
+                features: Some(&features),
                 recursion_limit: sess.recursion_limit.get(),
             };
             let ret = syntax::ext::expand::expand_crate(&sess.parse_sess,