remove the at_location from Locations

We are not currently using it for anything; even polonius just uses
the `from_location`.

Author: nikomatsakis

src/librustc_mir/borrow_check/nll/constraint_generation.rs

@@ -315,7 +315,6 @@ impl<'cx, 'cg, 'gcx, 'tcx> ConstraintGeneration<'cx, 'cg, 'gcx, 'tcx> {
                                 span,
                                 ref_region.to_region_vid(),
                                 borrow_region.to_region_vid(),
-                                location.successor_within_block(),
                             );
 
                             if let Some(all_facts) = self.all_facts {

src/librustc_mir/borrow_check/nll/constraint_set.rs

@@ -8,7 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use rustc::mir::Location;
 use rustc::ty::RegionVid;
 use rustc_data_structures::indexed_vec::{Idx, IndexVec};
 
@@ -24,8 +23,8 @@ crate struct ConstraintSet {
 impl ConstraintSet {
     pub fn push(&mut self, constraint: OutlivesConstraint) {
         debug!(
-            "add_outlives({:?}: {:?} @ {:?}",
-            constraint.sup, constraint.sub, constraint.point
+            "add_outlives({:?}: {:?})",
+            constraint.sup, constraint.sub
         );
         if constraint.sup == constraint.sub {
             // 'a: 'a is pretty uninteresting
@@ -86,9 +85,6 @@ pub struct OutlivesConstraint {
     /// Region that must be outlived.
     pub sub: RegionVid,
 
-    /// At this location.
-    pub point: Location,
-
     /// Later on, we thread the constraints onto a linked list
     /// grouped by their `sub` field. So if you had:
     ///
@@ -107,8 +103,8 @@ impl fmt::Debug for OutlivesConstraint {
     fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
         write!(
             formatter,
-            "({:?}: {:?} @ {:?}) due to {:?}",
-            self.sup, self.sub, self.point, self.span
+            "({:?}: {:?}) due to {:?}",
+            self.sup, self.sub, self.span
         )
     }
 }

src/librustc_mir/borrow_check/nll/region_infer/dump_mir.rs

@@ -82,15 +82,13 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             let OutlivesConstraint {
                 sup,
                 sub,
-                point,
                 span,
                 next: _,
             } = constraint;
             with_msg(&format!(
-                "{:?}: {:?} @ {:?} due to {:?}",
+                "{:?}: {:?} due to {:?}",
                 sup,
                 sub,
-                point,
                 span
             ))?;
         }

src/librustc_mir/borrow_check/nll/region_infer/graphviz.rs

@@ -44,7 +44,7 @@ impl<'this, 'tcx> dot::Labeller<'this> for RegionInferenceContext<'tcx> {
         dot::LabelText::LabelStr(format!("{:?}", n).into_cow())
     }
     fn edge_label(&'this self, e: &OutlivesConstraint) -> dot::LabelText<'this> {
-        dot::LabelText::LabelStr(format!("{:?}", e.point).into_cow())
+        dot::LabelText::LabelStr(format!("{:?}", e.span).into_cow())
     }
 }
 

src/librustc_mir/borrow_check/nll/region_infer/mod.rs

@@ -359,14 +359,12 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         span: Span,
         sup: RegionVid,
         sub: RegionVid,
-        point: Location,
     ) {
         assert!(self.inferred_values.is_none(), "values already inferred");
         self.constraints.push(OutlivesConstraint {
             span,
             sup,
             sub,
-            point,
             next: None,
         })
     }
@@ -503,7 +501,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         for type_test in &self.type_tests {
             debug!("check_type_test: {:?}", type_test);
 
-            if self.eval_region_test(mir, type_test.point, type_test.lower_bound, &type_test.test) {
+            if self.eval_region_test(mir, type_test.lower_bound, &type_test.test) {
                 continue;
             }
 
@@ -765,31 +763,30 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     fn eval_region_test(
         &self,
         mir: &Mir<'tcx>,
-        point: Location,
         lower_bound: RegionVid,
         test: &RegionTest,
     ) -> bool {
         debug!(
-            "eval_region_test(point={:?}, lower_bound={:?}, test={:?})",
-            point, lower_bound, test
+            "eval_region_test(lower_bound={:?}, test={:?})",
+            lower_bound, test
         );
 
         match test {
             RegionTest::IsOutlivedByAllRegionsIn(regions) => regions
                 .iter()
-                .all(|&r| self.eval_outlives(mir, r, lower_bound, point)),
+                .all(|&r| self.eval_outlives(mir, r, lower_bound)),
 
             RegionTest::IsOutlivedByAnyRegionIn(regions) => regions
                 .iter()
-                .any(|&r| self.eval_outlives(mir, r, lower_bound, point)),
+                .any(|&r| self.eval_outlives(mir, r, lower_bound)),
 
             RegionTest::Any(tests) => tests
                 .iter()
-                .any(|test| self.eval_region_test(mir, point, lower_bound, test)),
+                .any(|test| self.eval_region_test(mir, lower_bound, test)),
 
             RegionTest::All(tests) => tests
                 .iter()
-                .all(|test| self.eval_region_test(mir, point, lower_bound, test)),
+                .all(|test| self.eval_region_test(mir, lower_bound, test)),
         }
     }
 
@@ -799,11 +796,10 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         _mir: &Mir<'tcx>,
         sup_region: RegionVid,
         sub_region: RegionVid,
-        point: Location,
     ) -> bool {
         debug!(
-            "eval_outlives({:?}: {:?} @ {:?})",
-            sup_region, sub_region, point
+            "eval_outlives({:?}: {:?})",
+            sup_region, sub_region
         );
 
         let inferred_values = self

src/librustc_mir/borrow_check/nll/type_check/constraint_conversion.rs

@@ -146,7 +146,7 @@ impl<'a, 'gcx, 'tcx> ConstraintConversion<'a, 'gcx, 'tcx> {
     ) -> TypeTest<'tcx> {
         let lower_bound = self.to_region_vid(region);
 
-        let point = self.locations.at_location().unwrap_or(Location::START);
+        let point = self.locations.from_location().unwrap_or(Location::START);
 
         let test = self.verify_bound_to_region_test(&bound);
 
@@ -197,13 +197,11 @@ impl<'a, 'gcx, 'tcx> ConstraintConversion<'a, 'gcx, 'tcx> {
 
     fn add_outlives(&mut self, sup: ty::RegionVid, sub: ty::RegionVid) {
         let span = self.span();
-        let point = self.locations.at_location().unwrap_or(Location::START);
 
         self.outlives_constraints.push(OutlivesConstraint {
             span,
             sub,
             sup,
-            point,
             next: None,
         });
     }

src/librustc_mir/borrow_check/nll/type_check/mod.rs

@@ -671,11 +671,6 @@ pub enum Locations {
         /// This is intended for error reporting and diagnosis; the
         /// constraints may *take effect* at a distinct spot.
         from_location: Location,
-
-        /// The constraints must be met at this location. In terms of the
-        /// NLL RFC, when you have a constraint `R1: R2 @ P`, this field
-        /// is the `P` value.
-        at_location: Location,
     },
 }
 
@@ -686,13 +681,6 @@ impl Locations {
             Locations::Pair { from_location, .. } => Some(*from_location),
         }
     }
-
-    pub fn at_location(&self) -> Option<Location> {
-        match self {
-            Locations::All => None,
-            Locations::Pair { at_location, .. } => Some(*at_location),
-        }
-    }
 }
 
 impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
@@ -799,9 +787,7 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
             StatementKind::Assign(ref place, ref rv) => {
                 let place_ty = place.ty(mir, tcx).to_ty(tcx);
                 let rv_ty = rv.ty(mir, tcx);
-                if let Err(terr) =
-                    self.sub_types(rv_ty, place_ty, location.at_successor_within_block())
-                {
+                if let Err(terr) = self.sub_types(rv_ty, place_ty, location.at_self()) {
                     span_mirbug!(
                         self,
                         stmt,
@@ -897,15 +883,14 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
             TerminatorKind::DropAndReplace {
                 ref location,
                 ref value,
-                target,
-                unwind,
+                target: _,
+                unwind: _,
             } => {
                 let place_ty = location.ty(mir, tcx).to_ty(tcx);
                 let rv_ty = value.ty(mir, tcx);
 
                 let locations = Locations::Pair {
                     from_location: term_location,
-                    at_location: target.start_location(),
                 };
                 if let Err(terr) = self.sub_types(rv_ty, place_ty, locations) {
                     span_mirbug!(
@@ -917,26 +902,6 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
                         terr
                     );
                 }
-
-                // Subtle: this assignment occurs at the start of
-                // *both* blocks, so we need to ensure that it holds
-                // at both locations.
-                if let Some(unwind) = unwind {
-                    let locations = Locations::Pair {
-                        from_location: term_location,
-                        at_location: unwind.start_location(),
-                    };
-                    if let Err(terr) = self.sub_types(rv_ty, place_ty, locations) {
-                        span_mirbug!(
-                            self,
-                            term,
-                            "bad DropAndReplace ({:?} = {:?}): {:?}",
-                            place_ty,
-                            rv_ty,
-                            terr
-                        );
-                    }
-                }
             }
             TerminatorKind::SwitchInt {
                 ref discr,
@@ -1052,11 +1017,10 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
     ) {
         let tcx = self.tcx();
         match *destination {
-            Some((ref dest, target_block)) => {
+            Some((ref dest, _target_block)) => {
                 let dest_ty = dest.ty(mir, tcx).to_ty(tcx);
                 let locations = Locations::Pair {
                     from_location: term_location,
-                    at_location: target_block.start_location(),
                 };
                 if let Err(terr) = self.sub_types(sig.output(), dest_ty, locations) {
                     span_mirbug!(
@@ -1674,29 +1638,12 @@ trait AtLocation {
     /// indicated by `self`. This is typically used when processing
     /// "inputs" to the given location.
     fn at_self(self) -> Locations;
-
-    /// Creates a `Locations` where `self` is the from-location and
-    /// its successor within the block is the at-location. This means
-    /// that any required region relationships must hold only upon
-    /// **exiting** the statement/terminator indicated by `self`. This
-    /// is for example used when you have a `place = rv` statement: it
-    /// indicates that the `typeof(rv) <: typeof(place)` as of the
-    /// **next** statement.
-    fn at_successor_within_block(self) -> Locations;
 }
 
 impl AtLocation for Location {
     fn at_self(self) -> Locations {
         Locations::Pair {
             from_location: self,
-            at_location: self,
-        }
-    }
-
-    fn at_successor_within_block(self) -> Locations {
-        Locations::Pair {
-            from_location: self,
-            at_location: self.successor_within_block(),
         }
     }
 }