Auto merge of #28608 - eddyb:no-place-for-an-old-box, r=pnkfelix

While this is technically a [breaking-change], there is no excuse for touching `HEAP`.
r? @pnkfelix

Author: bors

src/liballoc/boxed.rs

@@ -80,11 +80,10 @@ use core::raw::{TraitObject};
 /// use std::boxed::HEAP;
 ///
 /// fn main() {
-///     let foo = box(HEAP) 5;
+///     let foo: Box<i32> = in HEAP { 5 };
 ///     let foo = box 5;
 /// }
 /// ```
-#[lang = "exchange_heap"]
 #[unstable(feature = "box_heap",
            reason = "may be renamed; uncertain about custom allocator design",
            issue = "27779")]

src/librustc/middle/cfg/construct.rs

@@ -344,13 +344,12 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
                 self.straightline(expr, pred, [r, l].iter().map(|&e| &**e))
             }
 
-            hir::ExprBox(Some(ref l), ref r) |
             hir::ExprIndex(ref l, ref r) |
             hir::ExprBinary(_, ref l, ref r) => { // NB: && and || handled earlier
                 self.straightline(expr, pred, [l, r].iter().map(|&e| &**e))
             }
 
-            hir::ExprBox(None, ref e) |
+            hir::ExprBox(ref e) |
             hir::ExprAddrOf(_, ref e) |
             hir::ExprCast(ref e, _) |
             hir::ExprUnary(_, ref e) |

src/librustc/middle/check_const.rs

@@ -568,8 +568,7 @@ fn check_expr<'a, 'tcx>(v: &mut CheckCrateVisitor<'a, 'tcx>,
                             "user-defined operators are not allowed in {}s", v.msg());
             }
         }
-        hir::ExprBox(..) |
-        hir::ExprUnary(hir::UnUniq, _) => {
+        hir::ExprBox(_) => {
             v.add_qualif(ConstQualif::NOT_CONST);
             if v.mode != Mode::Var {
                 span_err!(v.tcx.sess, e.span, E0010,

src/librustc/middle/expr_use_visitor.rs

@@ -280,13 +280,11 @@ impl<'d,'t,'a,'tcx> ExprUseVisitor<'d,'t,'a,'tcx> {
                typer: &'t infer::InferCtxt<'a, 'tcx>)
                -> ExprUseVisitor<'d,'t,'a,'tcx>
     {
-        let result = ExprUseVisitor {
+        ExprUseVisitor {
             typer: typer,
             mc: mc::MemCategorizationContext::new(typer),
             delegate: delegate,
-        };
-
-        result
+        }
     }
 
     pub fn walk_fn(&mut self,
@@ -544,17 +542,8 @@ impl<'d,'t,'a,'tcx> ExprUseVisitor<'d,'t,'a,'tcx> {
                 self.walk_captures(expr)
             }
 
-            hir::ExprBox(ref place, ref base) => {
-                match *place {
-                    Some(ref place) => self.consume_expr(&**place),
-                    None => {}
-                }
+            hir::ExprBox(ref base) => {
                 self.consume_expr(&**base);
-                if place.is_some() {
-                    self.tcx().sess.span_bug(
-                        expr.span,
-                        "box with explicit place remains after expansion");
-                }
             }
         }
     }

src/librustc/middle/lang_items.rs

@@ -341,7 +341,6 @@ lets_do_this! {
     EhUnwindResumeLangItem,          "eh_unwind_resume",        eh_unwind_resume;
     MSVCTryFilterLangItem,           "msvc_try_filter",         msvc_try_filter;
 
-    ExchangeHeapLangItem,            "exchange_heap",           exchange_heap;
     OwnedBoxLangItem,                "owned_box",               owned_box;
 
     PhantomDataItem,                 "phantom_data",            phantom_data;

src/librustc/middle/liveness.rs

@@ -1147,8 +1147,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
           }
 
           hir::ExprIndex(ref l, ref r) |
-          hir::ExprBinary(_, ref l, ref r) |
-          hir::ExprBox(Some(ref l), ref r) => {
+          hir::ExprBinary(_, ref l, ref r) => {
             let r_succ = self.propagate_through_expr(&**r, succ);
             self.propagate_through_expr(&**l, r_succ)
           }
@@ -1158,7 +1157,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
             e1.as_ref().map_or(succ, |e| self.propagate_through_expr(&**e, succ))
           }
 
-          hir::ExprBox(None, ref e) |
+          hir::ExprBox(ref e) |
           hir::ExprAddrOf(_, ref e) |
           hir::ExprCast(ref e, _) |
           hir::ExprUnary(_, ref e) => {

src/librustc/middle/region.rs

@@ -994,9 +994,6 @@ fn resolve_local(visitor: &mut RegionResolutionVisitor, local: &hir::Local) {
                         visitor, &**subexpr, blk_id);
                 }
             }
-            hir::ExprUnary(hir::UnUniq, ref subexpr) => {
-                record_rvalue_scope_if_borrow_expr(visitor, &**subexpr, blk_id);
-            }
             hir::ExprCast(ref subexpr, _) => {
                 record_rvalue_scope_if_borrow_expr(visitor, &**subexpr, blk_id)
             }

src/librustc_front/fold.rs

@@ -1040,8 +1040,8 @@ pub fn noop_fold_expr<T: Folder>(Expr {id, node, span}: Expr, folder: &mut T) ->
     Expr {
         id: folder.new_id(id),
         node: match node {
-            ExprBox(p, e) => {
-                ExprBox(p.map(|e|folder.fold_expr(e)), folder.fold_expr(e))
+            ExprBox(e) => {
+                ExprBox(folder.fold_expr(e))
             }
             ExprVec(exprs) => {
                 ExprVec(exprs.move_map(|x| folder.fold_expr(x)))

src/librustc_front/hir.rs

@@ -491,8 +491,6 @@ pub type BinOp = Spanned<BinOp_>;
 
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
 pub enum UnOp {
-    /// The `box` operator
-    UnUniq,
     /// The `*` operator for dereferencing
     UnDeref,
     /// The `!` operator for logical inversion
@@ -595,8 +593,8 @@ impl fmt::Debug for Expr {
 
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub enum Expr_ {
-    /// First expr is the place; second expr is the value.
-    ExprBox(Option<P<Expr>>, P<Expr>),
+    /// A `box x` expression.
+    ExprBox(P<Expr>),
     /// An array (`[a, b, c, d]`)
     ExprVec(Vec<P<Expr>>),
     /// A function call

src/librustc_front/lowering.rs

@@ -605,7 +605,6 @@ pub fn lower_constness(c: Constness) -> hir::Constness {
 
 pub fn lower_unop(u: UnOp) -> hir::UnOp {
     match u {
-        UnUniq => hir::UnUniq,
         UnDeref => hir::UnDeref,
         UnNot => hir::UnNot,
         UnNeg => hir::UnNeg,
@@ -694,8 +693,8 @@ pub fn lower_expr(e: &Expr) -> P<hir::Expr> {
     P(hir::Expr {
             id: e.id,
             node: match e.node {
-                ExprBox(ref p, ref e) => {
-                    hir::ExprBox(p.as_ref().map(|e| lower_expr(e)), lower_expr(e))
+                ExprBox(ref e) => {
+                    hir::ExprBox(lower_expr(e))
                 }
                 ExprVec(ref exprs) => {
                     hir::ExprVec(exprs.iter().map(|x| lower_expr(x)).collect())
@@ -818,6 +817,7 @@ pub fn lower_expr(e: &Expr) -> P<hir::Expr> {
                 ExprParen(ref ex) => {
                     return lower_expr(ex);
                 }
+                ExprInPlace(..) |
                 ExprIfLet(..) |
                 ExprWhileLet(..) |
                 ExprForLoop(..) |