replace universal_region with adding entries to region_live_at

There aren't that many universal regions. This was a premature
optimization and it makes the code much messier.

Author: nikomatsakis

src/librustc_mir/borrow_check/location.rs

@@ -23,6 +23,7 @@ use rustc_data_structures::indexed_vec::{Idx, IndexVec};
 /// table serves another purpose: it compresses locations from
 /// multiple words into a single u32.
 crate struct LocationTable {
+    num_points: usize,
     statements_before_block: IndexVec<BasicBlock, usize>,
 }
 
@@ -53,10 +54,15 @@ impl LocationTable {
         debug!("LocationTable: num_points={:#?}", num_points);
 
         Self {
+            num_points,
             statements_before_block,
         }
     }
 
+    crate fn all_points(&self) -> impl Iterator<Item = LocationIndex> {
+        (0..self.num_points).map(LocationIndex::new)
+    }
+
     crate fn start_index(&self, location: Location) -> LocationIndex {
         let Location {
             block,

src/librustc_mir/borrow_check/nll/mod.rs

@@ -111,9 +111,14 @@ pub(in borrow_check) fn compute_regions<'cx, 'gcx, 'tcx>(
     };
 
     if let Some(all_facts) = &mut all_facts {
-        all_facts
-            .universal_region
-            .extend(universal_regions.universal_regions());
+        // Declare that each universal region is live at every point.
+        for ur in universal_regions.universal_regions() {
+            all_facts.region_live_at.extend(
+                location_table
+                    .all_points()
+                    .map(|p| (ur, p))
+            );
+        }
     }
 
     // Create the region inference context, taking ownership of the region inference