From f277b394af03284bea7fad45838f7dbc570cf634 Mon Sep 17 00:00:00 2001
From: Niko Matsakis <niko@alum.mit.edu>
Date: Mon, 23 Jul 2018 22:10:18 +0300
Subject: [PATCH] generate extra liveness constraints before regioncx is
 created

---
 .../borrow_check/nll/constraint_generation.rs | 15 +++++++------
 src/librustc_mir/borrow_check/nll/mod.rs      | 21 +++++++++++--------
 2 files changed, 21 insertions(+), 15 deletions(-)

diff --git a/src/librustc_mir/borrow_check/nll/constraint_generation.rs b/src/librustc_mir/borrow_check/nll/constraint_generation.rs
index f274f8e9189..3074782c867 100644
--- a/src/librustc_mir/borrow_check/nll/constraint_generation.rs
+++ b/src/librustc_mir/borrow_check/nll/constraint_generation.rs
@@ -12,7 +12,7 @@ use borrow_check::borrow_set::BorrowSet;
 use borrow_check::location::LocationTable;
 use borrow_check::nll::ToRegionVid;
 use borrow_check::nll::facts::AllFacts;
-use borrow_check::nll::region_infer::RegionInferenceContext;
+use borrow_check::nll::region_infer::values::{RegionValueElements, RegionValues};
 use rustc::infer::InferCtxt;
 use rustc::mir::visit::TyContext;
 use rustc::mir::visit::Visitor;
@@ -20,11 +20,12 @@ use rustc::mir::{BasicBlock, BasicBlockData, Location, Mir, Place, Rvalue};
 use rustc::mir::{Local, Statement, Terminator};
 use rustc::ty::fold::TypeFoldable;
 use rustc::ty::subst::Substs;
-use rustc::ty::{self, CanonicalTy, ClosureSubsts, GeneratorSubsts};
+use rustc::ty::{self, CanonicalTy, ClosureSubsts, GeneratorSubsts, RegionVid};
 
 pub(super) fn generate_constraints<'cx, 'gcx, 'tcx>(
     infcx: &InferCtxt<'cx, 'gcx, 'tcx>,
-    regioncx: &mut RegionInferenceContext<'tcx>,
+    elements: &RegionValueElements,
+    liveness_constraints: &mut RegionValues<RegionVid>,
     all_facts: &mut Option<AllFacts>,
     location_table: &LocationTable,
     mir: &Mir<'tcx>,
@@ -33,9 +34,10 @@ pub(super) fn generate_constraints<'cx, 'gcx, 'tcx>(
     let mut cg = ConstraintGeneration {
         borrow_set,
         infcx,
-        regioncx,
+        liveness_constraints,
         location_table,
         all_facts,
+        elements,
     };
 
     for (bb, data) in mir.basic_blocks().iter_enumerated() {
@@ -48,8 +50,9 @@ struct ConstraintGeneration<'cg, 'cx: 'cg, 'gcx: 'tcx, 'tcx: 'cx> {
     infcx: &'cg InferCtxt<'cx, 'gcx, 'tcx>,
     all_facts: &'cg mut Option<AllFacts>,
     location_table: &'cg LocationTable,
-    regioncx: &'cg mut RegionInferenceContext<'tcx>,
+    liveness_constraints: &'cg mut RegionValues<RegionVid>,
     borrow_set: &'cg BorrowSet<'tcx>,
+    elements: &'cg RegionValueElements,
 }
 
 impl<'cg, 'cx, 'gcx, 'tcx> Visitor<'tcx> for ConstraintGeneration<'cg, 'cx, 'gcx, 'tcx> {
@@ -202,7 +205,7 @@ impl<'cx, 'cg, 'gcx, 'tcx> ConstraintGeneration<'cx, 'cg, 'gcx, 'tcx> {
             .tcx
             .for_each_free_region(&live_ty, |live_region| {
                 let vid = live_region.to_region_vid();
-                self.regioncx.add_live_element(vid, location);
+                self.liveness_constraints.add_element(&self.elements, vid, location);
             });
     }
 }
diff --git a/src/librustc_mir/borrow_check/nll/mod.rs b/src/librustc_mir/borrow_check/nll/mod.rs
index edc701bad1e..b9967c2be43 100644
--- a/src/librustc_mir/borrow_check/nll/mod.rs
+++ b/src/librustc_mir/borrow_check/nll/mod.rs
@@ -136,10 +136,21 @@ pub(in borrow_check) fn compute_regions<'cx, 'gcx, 'tcx>(
     // base constraints generated by the type-check.
     let var_origins = infcx.take_region_var_origins();
     let MirTypeckRegionConstraints {
-        liveness_constraints,
+        mut liveness_constraints,
         outlives_constraints,
         type_tests,
     } = constraint_sets;
+
+    constraint_generation::generate_constraints(
+        infcx,
+        &elements,
+        &mut liveness_constraints,
+        &mut all_facts,
+        location_table,
+        &mir,
+        borrow_set,
+    );
+
     let mut regioncx = RegionInferenceContext::new(
         var_origins,
         universal_regions,
@@ -151,14 +162,6 @@ pub(in borrow_check) fn compute_regions<'cx, 'gcx, 'tcx>(
     );
 
     // Generate various additional constraints.
-    constraint_generation::generate_constraints(
-        infcx,
-        &mut regioncx,
-        &mut all_facts,
-        location_table,
-        &mir,
-        borrow_set,
-    );
     invalidation::generate_invalidates(
         infcx,
         &mut all_facts,