From e5dc4ba2808ac81d7b3a1abab303e6d9eda5d9d6 Mon Sep 17 00:00:00 2001
From: Niko Matsakis <niko@alum.mit.edu>
Date: Wed, 22 Nov 2017 17:29:55 -0500
Subject: [PATCH] renumber types in `ty::Const` and relate them to
 `mir::Constant`

---
 src/librustc_mir/borrow_check/nll/mod.rs      |  5 ++
 src/librustc_mir/borrow_check/nll/renumber.rs |  5 ++
 .../nll/subtype_constraint_generation.rs      |  5 +-
 src/librustc_mir/transform/type_check.rs      | 47 +++++++++++++++++++
 4 files changed, 61 insertions(+), 1 deletion(-)

diff --git a/src/librustc_mir/borrow_check/nll/mod.rs b/src/librustc_mir/borrow_check/nll/mod.rs
index 804f5e26875..6d9e24bbb87 100644
--- a/src/librustc_mir/borrow_check/nll/mod.rs
+++ b/src/librustc_mir/borrow_check/nll/mod.rs
@@ -43,12 +43,17 @@ pub(in borrow_check) fn replace_regions_in_mir<'cx, 'gcx, 'tcx>(
     def_id: DefId,
     mir: &mut Mir<'tcx>,
 ) -> UniversalRegions<'tcx> {
+    debug!("replace_regions_in_mir(def_id={:?})", def_id);
+
     // Compute named region information.
     let universal_regions = universal_regions::universal_regions(infcx, def_id);
 
     // Replace all regions with fresh inference variables.
     renumber::renumber_mir(infcx, &universal_regions, mir);
 
+    let source = MirSource::item(def_id);
+    mir_util::dump_mir(infcx.tcx, None, "renumber", &0, source, mir, |_, _| Ok(()));
+
     universal_regions
 }
 
diff --git a/src/librustc_mir/borrow_check/nll/renumber.rs b/src/librustc_mir/borrow_check/nll/renumber.rs
index 371419da024..bb32cf88c75 100644
--- a/src/librustc_mir/borrow_check/nll/renumber.rs
+++ b/src/librustc_mir/borrow_check/nll/renumber.rs
@@ -138,6 +138,11 @@ impl<'a, 'gcx, 'tcx> MutVisitor<'tcx> for NLLVisitor<'a, 'gcx, 'tcx> {
         debug!("visit_region: region={:?}", region);
     }
 
+    fn visit_const(&mut self, constant: &mut &'tcx ty::Const<'tcx>, location: Location) {
+        let ty_context = TyContext::Location(location);
+        *constant = self.renumber_regions(ty_context, &*constant);
+    }
+
     fn visit_closure_substs(&mut self, substs: &mut ClosureSubsts<'tcx>, location: Location) {
         debug!(
             "visit_closure_substs(substs={:?}, location={:?})",
diff --git a/src/librustc_mir/borrow_check/nll/subtype_constraint_generation.rs b/src/librustc_mir/borrow_check/nll/subtype_constraint_generation.rs
index dbae40be6fe..e93f29f9bc8 100644
--- a/src/librustc_mir/borrow_check/nll/subtype_constraint_generation.rs
+++ b/src/librustc_mir/borrow_check/nll/subtype_constraint_generation.rs
@@ -106,7 +106,10 @@ impl<'cx, 'tcx> SubtypeConstraintGenerator<'cx, 'tcx> {
         if let ty::ReVar(vid) = r {
             *vid
         } else {
-            self.universal_regions.indices[&r]
+            *self.universal_regions
+                 .indices
+                 .get(&r)
+                 .unwrap_or_else(|| bug!("to_region_vid: bad region {:?}", r))
         }
     }
 }
diff --git a/src/librustc_mir/transform/type_check.rs b/src/librustc_mir/transform/type_check.rs
index f0b62e28a0d..f24aa51eb25 100644
--- a/src/librustc_mir/transform/type_check.rs
+++ b/src/librustc_mir/transform/type_check.rs
@@ -110,6 +110,7 @@ impl<'a, 'b, 'gcx, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'gcx, 'tcx> {
 
     fn visit_constant(&mut self, constant: &Constant<'tcx>, location: Location) {
         self.super_constant(constant, location);
+        self.sanitize_constant(constant, location);
         self.sanitize_type(constant, constant.ty);
     }
 
@@ -159,6 +160,52 @@ impl<'a, 'b, 'gcx, 'tcx> TypeVerifier<'a, 'b, 'gcx, 'tcx> {
         }
     }
 
+    /// Checks that the constant's `ty` field matches up with what
+    /// would be expected from its literal.
+    fn sanitize_constant(&mut self, constant: &Constant<'tcx>, location: Location) {
+        debug!(
+            "sanitize_constant(constant={:?}, location={:?})",
+            constant,
+            location
+        );
+
+        let expected_ty = match constant.literal {
+            Literal::Value { value } => value.ty,
+            Literal::Promoted { .. } => {
+                // FIXME -- promoted MIR return types reference
+                // various "free regions" (e.g., scopes and things)
+                // that they ought not to do. We have to figure out
+                // how best to handle that -- probably we want treat
+                // promoted MIR much like closures, renumbering all
+                // their free regions and propagating constraints
+                // upwards. We have the same acyclic guarantees, so
+                // that should be possible. But for now, ignore them.
+                //
+                // let promoted_mir = &self.mir.promoted[index];
+                // promoted_mir.return_ty()
+                return;
+            }
+        };
+
+        debug!("sanitize_constant: expected_ty={:?}", expected_ty);
+
+        if let Err(terr) = self.cx
+            .eq_types(expected_ty, constant.ty, location.at_self())
+        {
+            span_mirbug!(
+                self,
+                constant,
+                "constant {:?} should have type {:?} but has {:?} ({:?})",
+                constant,
+                expected_ty,
+                constant.ty,
+                terr,
+            );
+        }
+    }
+
+    /// Checks that the types internal to the `place` match up with
+    /// what would be expected.
     fn sanitize_place(
         &mut self,
         place: &Place<'tcx>,