Allow call to get_body_with_borrowck_facts without -Z polonius

compiler/rustc_borrowck/src/consumers.rs

@@ -14,7 +14,9 @@ pub use super::{
 };
 
 /// This function computes Polonius facts for the given body. It makes a copy of
-/// the body because it needs to regenerate the region identifiers.
+/// the body because it needs to regenerate the region identifiers. This function
+/// should never be invoked during a typical compilation session due to performance
+/// issues with Polonius.
 ///
 /// Note:
 /// *   This function will panic if the required body was already stolen. This
@@ -22,8 +24,6 @@ pub use super::{
 ///     because they are evaluated during typechecking. The panic can be avoided
 ///     by overriding the `mir_borrowck` query. You can find a complete example
 ///     that shows how to do this at `src/test/run-make/obtain-borrowck/`.
-/// *   This function will also panic if computation of Polonius facts
-///     (`-Zpolonius` flag) is not enabled.
 ///
 /// *   Polonius is highly unstable, so expect regular changes in its signature or other details.
 pub fn get_body_with_borrowck_facts<'tcx>(

compiler/rustc_borrowck/src/lib.rs

@@ -154,11 +154,6 @@ fn do_mir_borrowck<'a, 'tcx>(
 
     debug!("do_mir_borrowck(def = {:?})", def);
 
-    assert!(
-        !return_body_with_facts || infcx.tcx.sess.opts.debugging_opts.polonius,
-        "borrowck facts can be requested only when Polonius is enabled"
-    );
-
     let tcx = infcx.tcx;
     let param_env = tcx.param_env(def.did);
     let id = tcx.hir().local_def_id_to_hir_id(def.did);
@@ -235,6 +230,8 @@ fn do_mir_borrowck<'a, 'tcx>(
     let borrow_set =
         Rc::new(BorrowSet::build(tcx, body, locals_are_invalidated_at_exit, &mdpe.move_data));
 
+    let use_polonius = return_body_with_facts || infcx.tcx.sess.opts.debugging_opts.polonius;
+
     // Compute non-lexical lifetimes.
     let nll::NllOutput {
         regioncx,
@@ -254,6 +251,7 @@ fn do_mir_borrowck<'a, 'tcx>(
         &mdpe.move_data,
         &borrow_set,
         &upvars,
+        use_polonius,
     );
 
     // Dump MIR results into a file, if that is enabled. This let us

compiler/rustc_borrowck/src/nll.rs

@@ -164,8 +164,10 @@ pub(crate) fn compute_regions<'cx, 'tcx>(
     move_data: &MoveData<'tcx>,
     borrow_set: &BorrowSet<'tcx>,
     upvars: &[Upvar<'tcx>],
+    use_polonius: bool,
 ) -> NllOutput<'tcx> {
-    let mut all_facts = AllFacts::enabled(infcx.tcx).then_some(AllFacts::default());
+    let mut all_facts =
+        (use_polonius || AllFacts::enabled(infcx.tcx)).then_some(AllFacts::default());
 
     let universal_regions = Rc::new(universal_regions);
 
@@ -281,7 +283,7 @@ pub(crate) fn compute_regions<'cx, 'tcx>(
             all_facts.write_to_dir(dir_path, location_table).unwrap();
         }
 
-        if infcx.tcx.sess.opts.debugging_opts.polonius {
+        if use_polonius {
             let algorithm =
                 env::var("POLONIUS_ALGORITHM").unwrap_or_else(|_| String::from("Hybrid"));
             let algorithm = Algorithm::from_str(&algorithm).unwrap();