From 5f21aa8734d7d120ad2e09b2b3d7db6e313b3a63 Mon Sep 17 00:00:00 2001
From: David Wood <david@davidtw.co>
Date: Thu, 1 Mar 2018 14:31:14 +0000
Subject: [PATCH] Added initial processing of UserAssertTy statements.

---
 .../borrow_check/nll/type_check/mod.rs        | 17 ++++++++-
 .../transform/cleanup_post_borrowck.rs        | 35 ++++++++++++-------
 src/librustc_mir/transform/mod.rs             |  5 ++-
 3 files changed, 40 insertions(+), 17 deletions(-)

diff --git a/src/librustc_mir/borrow_check/nll/type_check/mod.rs b/src/librustc_mir/borrow_check/nll/type_check/mod.rs
index f070691a5cf8..147952d86719 100644
--- a/src/librustc_mir/borrow_check/nll/type_check/mod.rs
+++ b/src/librustc_mir/borrow_check/nll/type_check/mod.rs
@@ -761,12 +761,27 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
                     );
                 };
             }
+            StatementKind::UserAssertTy(ref ty, ref local) => {
+                let local_ty = mir.local_decls()[*local].ty;
+                debug!("check_stmt: user_assert_ty ty={:?} local_ty={:?}", ty, local_ty);
+                if let Err(terr) =
+                    self.eq_types(ty, local_ty, location.at_successor_within_block())
+                {
+                    span_mirbug!(
+                        self,
+                        stmt,
+                        "bad type assert ({:?} = {:?}): {:?}",
+                        ty,
+                        local_ty,
+                        terr
+                    );
+                }
+            }
             StatementKind::StorageLive(_)
             | StatementKind::StorageDead(_)
             | StatementKind::InlineAsm { .. }
             | StatementKind::EndRegion(_)
             | StatementKind::Validate(..)
-            | StatementKind::UserAssertTy(..)
             | StatementKind::Nop => {}
         }
     }
diff --git a/src/librustc_mir/transform/cleanup_post_borrowck.rs b/src/librustc_mir/transform/cleanup_post_borrowck.rs
index 5fdadc32a767..256b1fd66e9a 100644
--- a/src/librustc_mir/transform/cleanup_post_borrowck.rs
+++ b/src/librustc_mir/transform/cleanup_post_borrowck.rs
@@ -38,7 +38,7 @@ use rustc::mir::visit::{MutVisitor, Visitor, TyContext};
 use rustc::ty::{Ty, RegionKind, TyCtxt};
 use transform::{MirPass, MirSource};
 
-pub struct CleanupPostBorrowck;
+pub struct CleanEndRegions;
 
 struct GatherBorrowedRegions {
     seen_regions: FxHashSet<region::Scope>,
@@ -48,24 +48,19 @@ struct DeleteTrivialEndRegions<'a> {
     seen_regions: &'a FxHashSet<region::Scope>,
 }
 
-pub struct DeleteUserAssertTy;
-
-impl MirPass for CleanupPostBorrowck {
+impl MirPass for CleanEndRegions {
     fn run_pass<'a, 'tcx>(&self,
                           tcx: TyCtxt<'a, 'tcx, 'tcx>,
                           _source: MirSource,
                           mir: &mut Mir<'tcx>) {
-        if tcx.emit_end_regions() {
-            let mut gather = GatherBorrowedRegions {
-                seen_regions: FxHashSet()
-            };
-            gather.visit_mir(mir);
+        if !tcx.emit_end_regions() { return; }
 
-            let mut delete = DeleteTrivialEndRegions { seen_regions: &mut gather.seen_regions };
-            delete.visit_mir(mir);
-        }
+        let mut gather = GatherBorrowedRegions {
+            seen_regions: FxHashSet()
+        };
+        gather.visit_mir(mir);
 
-        let mut delete = DeleteUserAssertTy;
+        let mut delete = DeleteTrivialEndRegions { seen_regions: &mut gather.seen_regions };
         delete.visit_mir(mir);
     }
 }
@@ -115,6 +110,20 @@ impl<'a, 'tcx> MutVisitor<'tcx> for DeleteTrivialEndRegions<'a> {
     }
 }
 
+pub struct CleanUserAssertTy;
+
+pub struct DeleteUserAssertTy;
+
+impl MirPass for CleanUserAssertTy {
+    fn run_pass<'a, 'tcx>(&self,
+                          _tcx: TyCtxt<'a, 'tcx, 'tcx>,
+                          _source: MirSource,
+                          mir: &mut Mir<'tcx>) {
+        let mut delete = DeleteUserAssertTy;
+        delete.visit_mir(mir);
+    }
+}
+
 impl<'tcx> MutVisitor<'tcx> for DeleteUserAssertTy {
     fn visit_statement(&mut self,
                        block: BasicBlock,
diff --git a/src/librustc_mir/transform/mod.rs b/src/librustc_mir/transform/mod.rs
index 427528c4f6d9..63ca35aa0e7b 100644
--- a/src/librustc_mir/transform/mod.rs
+++ b/src/librustc_mir/transform/mod.rs
@@ -192,9 +192,8 @@ fn mir_const<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> &'tcx Stea
 
     let mut mir = tcx.mir_built(def_id).steal();
     run_passes![tcx, mir, def_id, 0;
-        // Remove all `UserAssertTy` statements and all `EndRegion` statements that are not
-        // involved in borrows.
-        cleanup_post_borrowck::CleanupPostBorrowck,
+        // Remove all `EndRegion` statements that are not involved in borrows.
+        cleanup_post_borrowck::CleanEndRegions,
 
         // What we need to do constant evaluation.
         simplify::SimplifyCfg::new("initial"),