Auto merge of #56638 - matthewjasper:remove-ref-region, r=nikomatsakis

Remove some `Region`s from HAIR

Use `ReErased` for any regions that need to be created in RValue::Ref
in MIR generation. We will change them to all to `ReVar` before borrow
checking anyway.

r? @nikomatsakis

6 files changed, 34 insertions, 55 deletions

diff --git a/src/librustc_mir/build/expr/as_rvalue.rs b/src/librustc_mir/build/expr/as_rvalue.rs
index a66da50c484..e0fc9093169 100644
--- a/src/librustc_mir/build/expr/as_rvalue.rs
+++ b/src/librustc_mir/build/expr/as_rvalue.rs
@@ -67,7 +67,6 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                 block.and(Rvalue::Repeat(value_operand, count))
             }
             ExprKind::Borrow {
-                region,
                 borrow_kind,
                 arg,
             } => {
@@ -75,7 +74,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                     BorrowKind::Shared => unpack!(block = this.as_read_only_place(block, arg)),
                     _ => unpack!(block = this.as_place(block, arg)),
                 };
-                block.and(Rvalue::Ref(region, borrow_kind, arg_place))
+                block.and(Rvalue::Ref(this.hir.tcx().types.re_erased, borrow_kind, arg_place))
             }
             ExprKind::Binary { op, lhs, rhs } => {
                 let lhs = unpack!(block = this.as_operand(block, scope, lhs));
@@ -249,11 +248,10 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                                             BorrowKind::Mut {
                                                 allow_two_phase_borrow: false,
                                             },
-                                        region,
                                         arg,
                                     } => unpack!(
                                         block = this.limit_capture_mutability(
-                                            upvar.span, upvar.ty, scope, block, arg, region,
+                                            upvar.span, upvar.ty, scope, block, arg,
                                         )
                                     ),
                                     _ => unpack!(block = this.as_operand(block, scope, upvar)),
@@ -500,7 +498,6 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
         temp_lifetime: Option<region::Scope>,
         mut block: BasicBlock,
         arg: ExprRef<'tcx>,
-        region: &'tcx ty::RegionKind,
     ) -> BlockAnd<Operand<'tcx>> {
         let this = self;
 
@@ -582,7 +579,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
             block,
             source_info,
             &Place::Local(temp),
-            Rvalue::Ref(region, borrow_kind, arg_place),
+            Rvalue::Ref(this.hir.tcx().types.re_erased, borrow_kind, arg_place),
         );
 
         // In constants, temp_lifetime is None. We should not need to drop
diff --git a/src/librustc_mir/build/matches/mod.rs b/src/librustc_mir/build/matches/mod.rs
index bc7bb485563..d52ce9a67d2 100644
--- a/src/librustc_mir/build/matches/mod.rs
+++ b/src/librustc_mir/build/matches/mod.rs
@@ -640,7 +640,7 @@ struct Binding<'tcx> {
     var_id: NodeId,
     var_ty: Ty<'tcx>,
     mutability: Mutability,
-    binding_mode: BindingMode<'tcx>,
+    binding_mode: BindingMode,
 }
 
 /// Indicates that the type of `source` must be a subtype of the
@@ -1369,7 +1369,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
         // Assign each of the bindings. Since we are binding for a
         // guard expression, this will never trigger moves out of the
         // candidate.
-        let re_empty = self.hir.tcx().types.re_empty;
+        let re_erased = self.hir.tcx().types.re_erased;
         for binding in bindings {
             let source_info = self.source_info(binding.span);
 
@@ -1385,11 +1385,11 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
             self.schedule_drop_for_binding(binding.var_id, binding.span, RefWithinGuard);
             match binding.binding_mode {
                 BindingMode::ByValue => {
-                    let rvalue = Rvalue::Ref(re_empty, BorrowKind::Shared, binding.source.clone());
+                    let rvalue = Rvalue::Ref(re_erased, BorrowKind::Shared, binding.source.clone());
                     self.cfg
                         .push_assign(block, source_info, &ref_for_guard, rvalue);
                 }
-                BindingMode::ByRef(region, borrow_kind) => {
+                BindingMode::ByRef(borrow_kind) => {
                     // Tricky business: For `ref id` and `ref mut id`
                     // patterns, we want `id` within the guard to
                     // correspond to a temp of type `& &T` or `& &mut
@@ -1429,10 +1429,10 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                             allow_two_phase_borrow: true,
                         },
                     };
-                    let rvalue = Rvalue::Ref(region, borrow_kind, binding.source.clone());
+                    let rvalue = Rvalue::Ref(re_erased, borrow_kind, binding.source.clone());
                     self.cfg
                         .push_assign(block, source_info, &val_for_guard, rvalue);
-                    let rvalue = Rvalue::Ref(region, BorrowKind::Shared, val_for_guard);
+                    let rvalue = Rvalue::Ref(re_erased, BorrowKind::Shared, val_for_guard);
                     self.cfg
                         .push_assign(block, source_info, &ref_for_guard, rvalue);
                 }
@@ -1450,6 +1450,8 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
             block, bindings
         );
 
+
+        let re_erased = self.hir.tcx().types.re_erased;
         // Assign each of the bindings. This may trigger moves out of the candidate.
         for binding in bindings {
             let source_info = self.source_info(binding.span);
@@ -1460,8 +1462,8 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                 BindingMode::ByValue => {
                     Rvalue::Use(self.consume_by_copy_or_move(binding.source.clone()))
                 }
-                BindingMode::ByRef(region, borrow_kind) => {
-                    Rvalue::Ref(region, borrow_kind, binding.source.clone())
+                BindingMode::ByRef(borrow_kind) => {
+                    Rvalue::Ref(re_erased, borrow_kind, binding.source.clone())
                 }
             };
             self.cfg.push_assign(block, source_info, &local, rvalue);
@@ -1507,7 +1509,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
         let tcx = self.hir.tcx();
         let binding_mode = match mode {
             BindingMode::ByValue => ty::BindingMode::BindByValue(mutability.into()),
-            BindingMode::ByRef { .. } => ty::BindingMode::BindByReference(mutability.into()),
+            BindingMode::ByRef(_) => ty::BindingMode::BindByReference(mutability.into()),
         };
         debug!("declare_binding: user_ty={:?}", user_ty);
         let local = LocalDecl::<'tcx> {
@@ -1545,7 +1547,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
             let ref_for_guard = self.local_decls.push(LocalDecl::<'tcx> {
                 // See previous comment.
                 mutability: Mutability::Not,
-                ty: tcx.mk_imm_ref(tcx.types.re_empty, var_ty),
+                ty: tcx.mk_imm_ref(tcx.types.re_erased, var_ty),
                 user_ty: UserTypeProjections::none(),
                 name: Some(name),
                 source_info,
@@ -1614,7 +1616,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
 
         for (matched_place, borrow_kind) in all_fake_borrows {
             let borrowed_input =
-                Rvalue::Ref(tcx.types.re_empty, borrow_kind, matched_place.clone());
+                Rvalue::Ref(tcx.types.re_erased, borrow_kind, matched_place.clone());
             let borrowed_input_ty = borrowed_input.ty(&self.local_decls, tcx);
             let borrowed_input_temp = self.temp(borrowed_input_ty, source_info.span);
             self.cfg.push_assign(
diff --git a/src/librustc_mir/build/matches/test.rs b/src/librustc_mir/build/matches/test.rs
index aae3de68aaa..696c173b048 100644
--- a/src/librustc_mir/build/matches/test.rs
+++ b/src/librustc_mir/build/matches/test.rs
@@ -304,17 +304,16 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                     let (mty, method) = self.hir.trait_method(eq_def_id, "eq", ty, &[ty.into()]);
                     let method = self.hir.tcx().intern_lazy_const(ty::LazyConst::Evaluated(method));
 
+                    let re_erased = self.hir.tcx().types.re_erased;
                     // take the argument by reference
-                    let region_scope = self.topmost_scope();
-                    let region = self.hir.tcx().mk_region(ty::ReScope(region_scope));
                     let tam = ty::TypeAndMut {
                         ty,
                         mutbl: Mutability::MutImmutable,
                     };
-                    let ref_ty = self.hir.tcx().mk_ref(region, tam);
+                    let ref_ty = self.hir.tcx().mk_ref(re_erased, tam);
 
                     // let lhs_ref_place = &lhs;
-                    let ref_rvalue = Rvalue::Ref(region, BorrowKind::Shared, place);
+                    let ref_rvalue = Rvalue::Ref(re_erased, BorrowKind::Shared, place);
                     let lhs_ref_place = self.temp(ref_ty, test.span);
                     self.cfg.push_assign(block, source_info, &lhs_ref_place, ref_rvalue);
                     let val = Operand::Move(lhs_ref_place);
@@ -324,7 +323,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                     self.cfg.push_assign(block, source_info, &rhs_place, Rvalue::Use(expect));
 
                     // let rhs_ref_place = &rhs_place;
-                    let ref_rvalue = Rvalue::Ref(region, BorrowKind::Shared, rhs_place);
+                    let ref_rvalue = Rvalue::Ref(re_erased, BorrowKind::Shared, rhs_place);
                     let rhs_ref_place = self.temp(ref_ty, test.span);
                     self.cfg.push_assign(block, source_info, &rhs_ref_place, ref_rvalue);
                     let expect = Operand::Move(rhs_ref_place);
diff --git a/src/librustc_mir/hair/cx/expr.rs b/src/librustc_mir/hair/cx/expr.rs
index 532e6783f2f..eb536fbcf69 100644
--- a/src/librustc_mir/hair/cx/expr.rs
+++ b/src/librustc_mir/hair/cx/expr.rs
@@ -124,7 +124,6 @@ fn apply_adjustment<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
                                   }),
                 span,
                 kind: ExprKind::Borrow {
-                    region: deref.region,
                     borrow_kind: deref.mutbl.to_borrow_kind(),
                     arg: expr.to_ref(),
                 },
@@ -132,32 +131,24 @@ fn apply_adjustment<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 
             overloaded_place(cx, hir_expr, adjustment.target, Some(call), vec![expr.to_ref()])
         }
-        Adjust::Borrow(AutoBorrow::Ref(r, m)) => {
+        Adjust::Borrow(AutoBorrow::Ref(_, m)) => {
             ExprKind::Borrow {
-                region: r,
                 borrow_kind: m.to_borrow_kind(),
                 arg: expr.to_ref(),
             }
         }
         Adjust::Borrow(AutoBorrow::RawPtr(m)) => {
             // Convert this to a suitable `&foo` and
-            // then an unsafe coercion. Limit the region to be just this
-            // expression.
-            let region = ty::ReScope(region::Scope {
-                id: hir_expr.hir_id.local_id,
-                data: region::ScopeData::Node
-            });
-            let region = cx.tcx.mk_region(region);
+            // then an unsafe coercion.
             expr = Expr {
                 temp_lifetime,
-                ty: cx.tcx.mk_ref(region,
+                ty: cx.tcx.mk_ref(cx.tcx.types.re_erased,
                                   ty::TypeAndMut {
                                     ty: expr.ty,
                                     mutbl: m,
                                   }),
                 span,
                 kind: ExprKind::Borrow {
-                    region,
                     borrow_kind: m.to_borrow_kind(),
                     arg: expr.to_ref(),
                 },
@@ -323,12 +314,7 @@ fn make_mirror_unadjusted<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
         }
 
         hir::ExprKind::AddrOf(mutbl, ref expr) => {
-            let region = match expr_ty.sty {
-                ty::Ref(r, _, _) => r,
-                _ => span_bug!(expr.span, "type of & not region"),
-            };
             ExprKind::Borrow {
-                region,
                 borrow_kind: mutbl.to_borrow_kind(),
                 arg: expr.to_ref(),
             }
@@ -1222,7 +1208,6 @@ fn capture_freevar<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
                 ty: freevar_ty,
                 span: closure_expr.span,
                 kind: ExprKind::Borrow {
-                    region: upvar_borrow.region,
                     borrow_kind,
                     arg: captured_var.to_ref(),
                 },
diff --git a/src/librustc_mir/hair/mod.rs b/src/librustc_mir/hair/mod.rs
index 676b9845748..e902423cd30 100644
--- a/src/librustc_mir/hair/mod.rs
+++ b/src/librustc_mir/hair/mod.rs
@@ -9,7 +9,7 @@ use rustc::hir::def_id::DefId;
 use rustc::infer::canonical::Canonical;
 use rustc::middle::region;
 use rustc::ty::subst::Substs;
-use rustc::ty::{AdtDef, UpvarSubsts, Region, Ty, Const, LazyConst, UserTypeAnnotation};
+use rustc::ty::{AdtDef, UpvarSubsts, Ty, Const, LazyConst, UserTypeAnnotation};
 use rustc::ty::layout::VariantIdx;
 use rustc::hir;
 use syntax::ast;
@@ -235,7 +235,6 @@ pub enum ExprKind<'tcx> {
         id: DefId,
     },
     Borrow {
-        region: Region<'tcx>,
         borrow_kind: BorrowKind,
         arg: ExprRef<'tcx>,
     },
diff --git a/src/librustc_mir/hair/pattern/mod.rs b/src/librustc_mir/hair/pattern/mod.rs
index 761bca21fec..8991a90737c 100644
--- a/src/librustc_mir/hair/pattern/mod.rs
+++ b/src/librustc_mir/hair/pattern/mod.rs
@@ -39,9 +39,9 @@ pub enum PatternError {
 }
 
 #[derive(Copy, Clone, Debug)]
-pub enum BindingMode<'tcx> {
+pub enum BindingMode {
     ByValue,
-    ByRef(Region<'tcx>, BorrowKind),
+    ByRef(BorrowKind),
 }
 
 #[derive(Clone, Debug)]
@@ -117,7 +117,7 @@ pub enum PatternKind<'tcx> {
     Binding {
         mutability: Mutability,
         name: ast::Name,
-        mode: BindingMode<'tcx>,
+        mode: BindingMode,
         var: ast::NodeId,
         ty: Ty<'tcx>,
         subpattern: Option<Pattern<'tcx>>,
@@ -181,7 +181,7 @@ impl<'tcx> fmt::Display for Pattern<'tcx> {
             PatternKind::Binding { mutability, name, mode, ref subpattern, .. } => {
                 let is_mut = match mode {
                     BindingMode::ByValue => mutability == Mutability::Mut,
-                    BindingMode::ByRef(_, bk) => {
+                    BindingMode::ByRef(bk) => {
                         write!(f, "ref ")?;
                         match bk { BorrowKind::Mut { .. } => true, _ => false }
                     }
@@ -512,12 +512,9 @@ impl<'a, 'tcx> PatternContext<'a, 'tcx> {
 
             PatKind::Binding(_, id, ident, ref sub) => {
                 let var_ty = self.tables.node_id_to_type(pat.hir_id);
-                let region = match var_ty.sty {
-                    ty::Ref(r, _, _) => Some(r),
-                    ty::Error => { // Avoid ICE
-                        return Pattern { span: pat.span, ty, kind: Box::new(PatternKind::Wild) };
-                    }
-                    _ => None,
+                if let ty::Error = var_ty.sty {
+                    // Avoid ICE
+                    return Pattern { span: pat.span, ty, kind: Box::new(PatternKind::Wild) };
                 };
                 let bm = *self.tables.pat_binding_modes().get(pat.hir_id)
                                                          .expect("missing binding mode");
@@ -528,10 +525,10 @@ impl<'a, 'tcx> PatternContext<'a, 'tcx> {
                         (Mutability::Not, BindingMode::ByValue),
                     ty::BindByReference(hir::MutMutable) =>
                         (Mutability::Not, BindingMode::ByRef(
-                            region.unwrap(), BorrowKind::Mut { allow_two_phase_borrow: false })),
+                            BorrowKind::Mut { allow_two_phase_borrow: false })),
                     ty::BindByReference(hir::MutImmutable) =>
                         (Mutability::Not, BindingMode::ByRef(
-                            region.unwrap(), BorrowKind::Shared)),
+                            BorrowKind::Shared)),
                 };
 
                 // A ref x pattern is the same node used for x, and as such it has
@@ -1042,7 +1039,7 @@ macro_rules! CloneImpls {
 
 CloneImpls!{ <'tcx>
     Span, Field, Mutability, ast::Name, ast::NodeId, usize, ty::Const<'tcx>,
-    Region<'tcx>, Ty<'tcx>, BindingMode<'tcx>, &'tcx AdtDef,
+    Region<'tcx>, Ty<'tcx>, BindingMode, &'tcx AdtDef,
     &'tcx Substs<'tcx>, &'tcx Kind<'tcx>, UserTypeAnnotation<'tcx>,
     UserTypeProjection<'tcx>, PatternTypeProjection<'tcx>
 }