Remove ExprKind::While from HIR.

21 files changed, 114 insertions, 272 deletions

diff --git a/src/librustc/cfg/construct.rs b/src/librustc/cfg/construct.rs
index a132575b0c6..f81d1869413 100644
--- a/src/librustc/cfg/construct.rs
+++ b/src/librustc/cfg/construct.rs
@@ -165,48 +165,6 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
                 self.add_ast_node(expr.hir_id.local_id, &[blk_exit])
             }
 
-            hir::ExprKind::While(ref cond, ref body, _) => {
-                //
-                //         [pred]
-                //           |
-                //           v 1
-                //       [loopback] <--+ 5
-                //           |         |
-                //           v 2       |
-                //   +-----[cond]      |
-                //   |       |         |
-                //   |       v 4       |
-                //   |     [body] -----+
-                //   v 3
-                // [expr]
-                //
-                // Note that `break` and `continue` statements
-                // may cause additional edges.
-
-                let loopback = self.add_dummy_node(&[pred]);              // 1
-
-                // Create expr_exit without pred (cond_exit)
-                let expr_exit = self.add_ast_node(expr.hir_id.local_id, &[]);         // 3
-
-                // The LoopScope needs to be on the loop_scopes stack while evaluating the
-                // condition and the body of the loop (both can break out of the loop)
-                self.loop_scopes.push(LoopScope {
-                    loop_id: expr.hir_id.local_id,
-                    continue_index: loopback,
-                    break_index: expr_exit
-                });
-
-                let cond_exit = self.expr(&cond, loopback);             // 2
-
-                // Add pred (cond_exit) to expr_exit
-                self.add_contained_edge(cond_exit, expr_exit);
-
-                let body_exit = self.block(&body, cond_exit);          // 4
-                self.add_contained_edge(body_exit, loopback);            // 5
-                self.loop_scopes.pop();
-                expr_exit
-            }
-
             hir::ExprKind::Loop(ref body, _, _) => {
                 //
                 //     [pred]
diff --git a/src/librustc/hir/intravisit.rs b/src/librustc/hir/intravisit.rs
index 9c05f18762d..2d82314f86a 100644
--- a/src/librustc/hir/intravisit.rs
+++ b/src/librustc/hir/intravisit.rs
@@ -1026,11 +1026,6 @@ pub fn walk_expr<'v, V: Visitor<'v>>(visitor: &mut V, expression: &'v Expr) {
         ExprKind::DropTemps(ref subexpression) => {
             visitor.visit_expr(subexpression);
         }
-        ExprKind::While(ref subexpression, ref block, ref opt_label) => {
-            walk_list!(visitor, visit_label, opt_label);
-            visitor.visit_expr(subexpression);
-            visitor.visit_block(block);
-        }
         ExprKind::Loop(ref block, ref opt_label, _) => {
             walk_list!(visitor, visit_label, opt_label);
             visitor.visit_block(block);
diff --git a/src/librustc/hir/lowering.rs b/src/librustc/hir/lowering.rs
index ef05b57fb8f..011808a7ff9 100644
--- a/src/librustc/hir/lowering.rs
+++ b/src/librustc/hir/lowering.rs
@@ -4461,11 +4461,11 @@ impl<'a> LoweringContext<'a> {
                     };
 
                     // `match <sub_expr> { ... }`
-                    let arms = hir_vec![pat_arm, break_arm];
-                    let match_expr = self.expr(
+                    let match_expr = self.expr_match(
                         sub_expr.span,
-                        hir::ExprKind::Match(sub_expr, arms, hir::MatchSource::WhileLetDesugar),
-                        ThinVec::new(),
+                        sub_expr,
+                        hir_vec![pat_arm, break_arm],
+                        hir::MatchSource::WhileLetDesugar,
                     );
 
                     // `[opt_ident]: loop { ... }`
@@ -4479,10 +4479,46 @@ impl<'a> LoweringContext<'a> {
                     loop_expr
                 } else {
                     self.with_loop_scope(e.id, |this| {
-                        hir::ExprKind::While(
-                            this.with_loop_condition_scope(|this| P(this.lower_expr(cond))),
-                            this.lower_block(body, false),
+                        // We desugar: `'label: while $cond $body` into:
+                        //
+                        // ```
+                        // 'label: loop {
+                        //     match DropTemps($cond) {
+                        //         true => $block,
+                        //         _ => break,
+                        //     }
+                        // }
+                        // ```
+
+                        // `true => then`:
+                        let then_pat = this.pat_bool(e.span, true);
+                        let then_blk = this.lower_block(body, false);
+                        let then_expr = this.expr_block(then_blk, ThinVec::new());
+                        let then_arm = this.arm(hir_vec![then_pat], P(then_expr));
+
+                        // `_ => break`:
+                        let else_pat = this.pat_wild(e.span);
+                        let else_expr = this.expr_break(e.span, ThinVec::new());
+                        let else_arm = this.arm(hir_vec![else_pat], else_expr);
+
+                        // Lower condition:
+                        let cond = this.with_loop_condition_scope(|this| this.lower_expr(cond));
+                        // Wrap in a construct equivalent to `{ let _t = $cond; _t }`
+                        // to preserve drop semantics since `if cond { ... }` does not
+                        // let temporaries live outside of `cond`.
+                        let cond = this.expr_drop_temps(cond.span, P(cond), ThinVec::new());
+
+                        let match_expr = this.expr_match(
+                            cond.span,
+                            P(cond),
+                            vec![then_arm, else_arm].into(),
+                            hir::MatchSource::WhileDesugar,
+                        );
+
+                        hir::ExprKind::Loop(
+                            P(this.block_expr(P(match_expr))),
                             this.lower_label(opt_label),
+                            hir::LoopSource::While,
                         )
                     })
                 }
diff --git a/src/librustc/hir/map/mod.rs b/src/librustc/hir/map/mod.rs
index 79b343ecfe2..63f60d0ab95 100644
--- a/src/librustc/hir/map/mod.rs
+++ b/src/librustc/hir/map/mod.rs
@@ -731,7 +731,7 @@ impl<'hir> Map<'hir> {
             match *node {
                 Node::Expr(ref expr) => {
                     match expr.node {
-                        ExprKind::While(..) | ExprKind::Loop(..) | ExprKind::Ret(..) => true,
+                        ExprKind::Loop(..) | ExprKind::Ret(..) => true,
                         _ => false,
                     }
                 }
diff --git a/src/librustc/hir/mod.rs b/src/librustc/hir/mod.rs
index bfbd8398f99..7b760a87238 100644
--- a/src/librustc/hir/mod.rs
+++ b/src/librustc/hir/mod.rs
@@ -1405,7 +1405,6 @@ impl Expr {
             ExprKind::Lit(_) => ExprPrecedence::Lit,
             ExprKind::Type(..) | ExprKind::Cast(..) => ExprPrecedence::Cast,
             ExprKind::DropTemps(ref expr, ..) => expr.precedence(),
-            ExprKind::While(..) => ExprPrecedence::While,
             ExprKind::Loop(..) => ExprPrecedence::Loop,
             ExprKind::Match(..) => ExprPrecedence::Match,
             ExprKind::Closure(..) => ExprPrecedence::Closure,
@@ -1464,7 +1463,6 @@ impl Expr {
             ExprKind::Break(..) |
             ExprKind::Continue(..) |
             ExprKind::Ret(..) |
-            ExprKind::While(..) |
             ExprKind::Loop(..) |
             ExprKind::Assign(..) |
             ExprKind::InlineAsm(..) |
@@ -1532,10 +1530,6 @@ pub enum ExprKind {
     /// This construct only exists to tweak the drop order in HIR lowering.
     /// An example of that is the desugaring of `for` loops.
     DropTemps(P<Expr>),
-    /// A while loop, with an optional label
-    ///
-    /// I.e., `'label: while expr { <block> }`.
-    While(P<Expr>, P<Block>, Option<Label>),
     /// A conditionless loop (can be exited with `break`, `continue`, or `return`).
     ///
     /// I.e., `'label: loop { <block> }`.
@@ -1653,6 +1647,8 @@ pub enum MatchSource {
     IfLetDesugar {
         contains_else_clause: bool,
     },
+    /// A `while _ { .. }` (which was desugared to a `loop { match _ { .. } }`).
+    WhileDesugar,
     /// A `while let _ = _ { .. }` (which was desugared to a
     /// `loop { match _ { .. } }`).
     WhileLetDesugar,
@@ -1669,12 +1665,25 @@ pub enum MatchSource {
 pub enum LoopSource {
     /// A `loop { .. }` loop.
     Loop,
+    /// A `while _ { .. }` loop.
+    While,
     /// A `while let _ = _ { .. }` loop.
     WhileLet,
     /// A `for _ in _ { .. }` loop.
     ForLoop,
 }
 
+impl LoopSource {
+    pub fn name(self) -> &'static str {
+        match self {
+            LoopSource::Loop => "loop",
+            LoopSource::While => "while",
+            LoopSource::WhileLet => "while let",
+            LoopSource::ForLoop => "for",
+        }
+    }
+}
+
 #[derive(Copy, Clone, RustcEncodable, RustcDecodable, Debug, HashStable)]
 pub enum LoopIdError {
     OutsideLoopScope,
diff --git a/src/librustc/hir/print.rs b/src/librustc/hir/print.rs
index 573b9add133..367e4dba042 100644
--- a/src/librustc/hir/print.rs
+++ b/src/librustc/hir/print.rs
@@ -1299,16 +1299,6 @@ impl<'a> State<'a> {
                 // Print `}`:
                 self.bclose_maybe_open(expr.span, indent_unit, true);
             }
-            hir::ExprKind::While(ref test, ref blk, opt_label) => {
-                if let Some(label) = opt_label {
-                    self.print_ident(label.ident);
-                    self.word_space(":");
-                }
-                self.head("while");
-                self.print_expr_as_cond(&test);
-                self.s.space();
-                self.print_block(&blk);
-            }
             hir::ExprKind::Loop(ref blk, opt_label, _) => {
                 if let Some(label) = opt_label {
                     self.print_ident(label.ident);
@@ -2289,7 +2279,6 @@ fn expr_requires_semi_to_be_stmt(e: &hir::Expr) -> bool {
     match e.node {
         hir::ExprKind::Match(..) |
         hir::ExprKind::Block(..) |
-        hir::ExprKind::While(..) |
         hir::ExprKind::Loop(..) => false,
         _ => true,
     }
diff --git a/src/librustc/middle/expr_use_visitor.rs b/src/librustc/middle/expr_use_visitor.rs
index 77094604eda..2448db032b9 100644
--- a/src/librustc/middle/expr_use_visitor.rs
+++ b/src/librustc/middle/expr_use_visitor.rs
@@ -487,11 +487,6 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
                 self.walk_block(&blk);
             }
 
-            hir::ExprKind::While(ref cond_expr, ref blk, _) => {
-                self.consume_expr(&cond_expr);
-                self.walk_block(&blk);
-            }
-
             hir::ExprKind::Unary(_, ref lhs) => {
                 self.consume_expr(&lhs);
             }
diff --git a/src/librustc/middle/liveness.rs b/src/librustc/middle/liveness.rs
index c4d60b676b2..3885d1b6f82 100644
--- a/src/librustc/middle/liveness.rs
+++ b/src/librustc/middle/liveness.rs
@@ -93,7 +93,6 @@
 //!   It is the responsibility of typeck to ensure that there are no
 //!   `return` expressions in a function declared as diverging.
 
-use self::LoopKind::*;
 use self::LiveNodeKind::*;
 use self::VarKind::*;
 
@@ -120,14 +119,6 @@ use crate::hir::{Expr, HirId};
 use crate::hir::def_id::DefId;
 use crate::hir::intravisit::{self, Visitor, FnKind, NestedVisitorMap};
 
-/// For use with `propagate_through_loop`.
-enum LoopKind<'a> {
-    /// An endless `loop` loop.
-    LoopLoop,
-    /// A `while` loop, with the given expression as condition.
-    WhileLoop(&'a Expr),
-}
-
 #[derive(Copy, Clone, PartialEq)]
 struct Variable(u32);
 
@@ -517,7 +508,6 @@ fn visit_expr<'tcx>(ir: &mut IrMaps<'tcx>, expr: &'tcx Expr) {
 
       // live nodes required for interesting control flow:
       hir::ExprKind::Match(..) |
-      hir::ExprKind::While(..) |
       hir::ExprKind::Loop(..) => {
         ir.add_live_node_for_node(expr.hir_id, ExprNode(expr.span));
         intravisit::walk_expr(ir, expr);
@@ -1055,14 +1045,10 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
                 })
             }
 
-            hir::ExprKind::While(ref cond, ref blk, _) => {
-                self.propagate_through_loop(expr, WhileLoop(&cond), &blk, succ)
-            }
-
             // Note that labels have been resolved, so we don't need to look
             // at the label ident
             hir::ExprKind::Loop(ref blk, _, _) => {
-                self.propagate_through_loop(expr, LoopLoop, &blk, succ)
+                self.propagate_through_loop(expr, &blk, succ)
             }
 
             hir::ExprKind::Match(ref e, ref arms, _) => {
@@ -1353,13 +1339,14 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
         }
     }
 
-    fn propagate_through_loop(&mut self,
-                              expr: &Expr,
-                              kind: LoopKind<'_>,
-                              body: &hir::Block,
-                              succ: LiveNode)
-                              -> LiveNode {
+    fn propagate_through_loop(
+        &mut self,
+        expr: &Expr,
+        body: &hir::Block,
+        succ: LiveNode
+    ) -> LiveNode {
         /*
+        FIXME: clean up this description.
 
         We model control flow like this:
 
@@ -1377,50 +1364,26 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
 
         */
 
-
         // first iteration:
         let mut first_merge = true;
         let ln = self.live_node(expr.hir_id, expr.span);
         self.init_empty(ln, succ);
-        match kind {
-            LoopLoop => {}
-            _ => {
-                // If this is not a `loop` loop, then it's possible we bypass
-                // the body altogether. Otherwise, the only way is via a `break`
-                // in the loop body.
-                self.merge_from_succ(ln, succ, first_merge);
-                first_merge = false;
-            }
-        }
         debug!("propagate_through_loop: using id for loop body {} {}",
                expr.hir_id, self.ir.tcx.hir().hir_to_pretty_string(body.hir_id));
 
         self.break_ln.insert(expr.hir_id, succ);
 
-        let cond_ln = match kind {
-            LoopLoop => ln,
-            WhileLoop(ref cond) => self.propagate_through_expr(&cond, ln),
-        };
-
-        self.cont_ln.insert(expr.hir_id, cond_ln);
+        self.cont_ln.insert(expr.hir_id, ln);
 
-        let body_ln = self.propagate_through_block(body, cond_ln);
+        let body_ln = self.propagate_through_block(body, ln);
 
         // repeat until fixed point is reached:
         while self.merge_from_succ(ln, body_ln, first_merge) {
             first_merge = false;
-
-            let new_cond_ln = match kind {
-                LoopLoop => ln,
-                WhileLoop(ref cond) => {
-                    self.propagate_through_expr(&cond, ln)
-                }
-            };
-            assert_eq!(cond_ln, new_cond_ln);
-            assert_eq!(body_ln, self.propagate_through_block(body, cond_ln));
+            assert_eq!(body_ln, self.propagate_through_block(body, ln));
         }
 
-        cond_ln
+        ln
     }
 }
 
@@ -1520,7 +1483,7 @@ fn check_expr<'a, 'tcx>(this: &mut Liveness<'a, 'tcx>, expr: &'tcx Expr) {
 
         // no correctness conditions related to liveness
         hir::ExprKind::Call(..) | hir::ExprKind::MethodCall(..) |
-        hir::ExprKind::Match(..) | hir::ExprKind::While(..) | hir::ExprKind::Loop(..) |
+        hir::ExprKind::Match(..) | hir::ExprKind::Loop(..) |
         hir::ExprKind::Index(..) | hir::ExprKind::Field(..) |
         hir::ExprKind::Array(..) | hir::ExprKind::Tup(..) | hir::ExprKind::Binary(..) |
         hir::ExprKind::Cast(..) | hir::ExprKind::DropTemps(..) | hir::ExprKind::Unary(..) |
diff --git a/src/librustc/middle/mem_categorization.rs b/src/librustc/middle/mem_categorization.rs
index 088c862dcb8..66d8a2cc111 100644
--- a/src/librustc/middle/mem_categorization.rs
+++ b/src/librustc/middle/mem_categorization.rs
@@ -696,7 +696,7 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
             hir::ExprKind::Unary(..) | hir::ExprKind::Yield(..) |
             hir::ExprKind::MethodCall(..) | hir::ExprKind::Cast(..) | hir::ExprKind::DropTemps(..) |
             hir::ExprKind::Array(..) | hir::ExprKind::Tup(..) |
-            hir::ExprKind::Binary(..) | hir::ExprKind::While(..) |
+            hir::ExprKind::Binary(..) |
             hir::ExprKind::Block(..) | hir::ExprKind::Loop(..) | hir::ExprKind::Match(..) |
             hir::ExprKind::Lit(..) | hir::ExprKind::Break(..) |
             hir::ExprKind::Continue(..) | hir::ExprKind::Struct(..) | hir::ExprKind::Repeat(..) |
diff --git a/src/librustc/middle/region.rs b/src/librustc/middle/region.rs
index 26ac1275bb9..88c19715811 100644
--- a/src/librustc/middle/region.rs
+++ b/src/librustc/middle/region.rs
@@ -915,11 +915,6 @@ fn resolve_expr<'tcx>(visitor: &mut RegionResolutionVisitor<'tcx>, expr: &'tcx h
                 terminating(body.hir_id.local_id);
             }
 
-            hir::ExprKind::While(ref expr, ref body, _) => {
-                terminating(expr.hir_id.local_id);
-                terminating(body.hir_id.local_id);
-            }
-
             hir::ExprKind::DropTemps(ref expr) => {
                 // `DropTemps(expr)` does not denote a conditional scope.
                 // Rather, we want to achieve the same behavior as `{ let _t = expr; _t }`.
diff --git a/src/librustc/middle/resolve_lifetime.rs b/src/librustc/middle/resolve_lifetime.rs
index 0839a2b435a..3221b41ee1d 100644
--- a/src/librustc/middle/resolve_lifetime.rs
+++ b/src/librustc/middle/resolve_lifetime.rs
@@ -1201,11 +1201,10 @@ fn extract_labels(ctxt: &mut LifetimeContext<'_, '_>, body: &hir::Body) {
     }
 
     fn expression_label(ex: &hir::Expr) -> Option<ast::Ident> {
-        match ex.node {
-            hir::ExprKind::While(.., Some(label)) | hir::ExprKind::Loop(_, Some(label), _) => {
-                Some(label.ident)
-            }
-            _ => None,
+        if let hir::ExprKind::Loop(_, Some(label), _) = ex.node {
+            Some(label.ident)
+        } else {
+            None
         }
     }
 
diff --git a/src/librustc_lint/builtin.rs b/src/librustc_lint/builtin.rs
index 267b09bae35..d98dfb5478a 100644
--- a/src/librustc_lint/builtin.rs
+++ b/src/librustc_lint/builtin.rs
@@ -64,9 +64,25 @@ declare_lint! {
 
 declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
 
+fn as_while_cond(expr: &hir::Expr) -> Option<&hir::Expr> {
+    if let hir::ExprKind::Loop(blk, ..) = &expr.node {
+        if let Some(match_expr) = &blk.expr {
+            if let hir::ExprKind::Match(cond, .., hir::MatchSource::WhileDesugar)
+                = &match_expr.node
+            {
+                if let hir::ExprKind::DropTemps(cond) = &cond.node {
+                    return Some(cond);
+                }
+            }
+        }
+    }
+
+    None
+}
+
 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for WhileTrue {
     fn check_expr(&mut self, cx: &LateContext<'_, '_>, e: &hir::Expr) {
-        if let hir::ExprKind::While(ref cond, ..) = e.node {
+        if let Some(ref cond) = as_while_cond(e) {
             if let hir::ExprKind::Lit(ref lit) = cond.node {
                 if let ast::LitKind::Bool(true) = lit.node {
                     if lit.span.ctxt() == SyntaxContext::empty() {
diff --git a/src/librustc_mir/build/expr/into.rs b/src/librustc_mir/build/expr/into.rs
index 0a2ea78bfd7..e433da904a6 100644
--- a/src/librustc_mir/build/expr/into.rs
+++ b/src/librustc_mir/build/expr/into.rs
@@ -138,19 +138,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 
                 join_block.unit()
             }
-            ExprKind::Loop {
-                condition: opt_cond_expr,
-                body,
-            } => {
-                // [block] --> [loop_block] -/eval. cond./-> [loop_block_end] -1-> [exit_block]
-                //                  ^                               |
-                //                  |                               0
-                //                  |                               |
-                //                  |                               v
-                //           [body_block_end] <-/eval. body/-- [body_block]
-                //
-                // If `opt_cond_expr` is `None`, then the graph is somewhat simplified:
-                //
+            ExprKind::Loop { body } => {
                 // [block]
                 //    |
                 //   [loop_block] -> [body_block] -/eval. body/-> [body_block_end]
@@ -177,33 +165,16 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     destination.clone(),
                     move |this| {
                         // conduct the test, if necessary
-                        let body_block;
-                        if let Some(cond_expr) = opt_cond_expr {
-                            let cond_expr = this.hir.mirror(cond_expr);
-                            let (true_block, false_block)
-                                = this.test_bool(loop_block, cond_expr, source_info);
-                            body_block = true_block;
-
-                            // if the test is false, there's no `break` to assign `destination`, so
-                            // we have to do it
-                            this.cfg.push_assign_unit(false_block, source_info, destination);
-                            this.cfg.terminate(
-                                false_block,
-                                source_info,
-                                TerminatorKind::Goto { target: exit_block },
-                            );
-                        } else {
-                            body_block = this.cfg.start_new_block();
-                            let diverge_cleanup = this.diverge_cleanup();
-                            this.cfg.terminate(
-                                loop_block,
-                                source_info,
-                                TerminatorKind::FalseUnwind {
-                                    real_target: body_block,
-                                    unwind: Some(diverge_cleanup),
-                                },
-                            )
-                        }
+                        let body_block = this.cfg.start_new_block();
+                        let diverge_cleanup = this.diverge_cleanup();
+                        this.cfg.terminate(
+                            loop_block,
+                            source_info,
+                            TerminatorKind::FalseUnwind {
+                                real_target: body_block,
+                                unwind: Some(diverge_cleanup),
+                            },
+                        );
 
                         // The “return” value of the loop body must always be an unit. We therefore
                         // introduce a unit temporary as the destination for the loop body.
diff --git a/src/librustc_mir/hair/cx/expr.rs b/src/librustc_mir/hair/cx/expr.rs
index e7663ddaa98..242afcf5abb 100644
--- a/src/librustc_mir/hair/cx/expr.rs
+++ b/src/librustc_mir/hair/cx/expr.rs
@@ -599,15 +599,8 @@ fn make_mirror_unadjusted<'a, 'tcx>(
                 arms: arms.iter().map(|a| convert_arm(cx, a)).collect(),
             }
         }
-        hir::ExprKind::While(ref cond, ref body, _) => {
-            ExprKind::Loop {
-                condition: Some(cond.to_ref()),
-                body: block::to_expr_ref(cx, body),
-            }
-        }
         hir::ExprKind::Loop(ref body, _, _) => {
             ExprKind::Loop {
-                condition: None,
                 body: block::to_expr_ref(cx, body),
             }
         }
diff --git a/src/librustc_mir/hair/mod.rs b/src/librustc_mir/hair/mod.rs
index 5431a31c4bb..0638cb462f7 100644
--- a/src/librustc_mir/hair/mod.rs
+++ b/src/librustc_mir/hair/mod.rs
@@ -173,7 +173,6 @@ pub enum ExprKind<'tcx> {
         source: ExprRef<'tcx>,
     },
     Loop {
-        condition: Option<ExprRef<'tcx>>,
         body: ExprRef<'tcx>,
     },
     Match {
diff --git a/src/librustc_mir/hair/pattern/check_match.rs b/src/librustc_mir/hair/pattern/check_match.rs
index 915ce9f20d0..d822a26ce59 100644
--- a/src/librustc_mir/hair/pattern/check_match.rs
+++ b/src/librustc_mir/hair/pattern/check_match.rs
@@ -371,7 +371,8 @@ fn check_arms<'a, 'tcx>(
             match is_useful(cx, &seen, &v, LeaveOutWitness) {
                 NotUseful => {
                     match source {
-                        hir::MatchSource::IfDesugar { .. } => bug!(),
+                        hir::MatchSource::IfDesugar { .. } |
+                        hir::MatchSource::WhileDesugar => bug!(),
                         hir::MatchSource::IfLetDesugar { .. } => {
                             cx.tcx.lint_hir(
                                 lint::builtin::IRREFUTABLE_LET_PATTERNS,
diff --git a/src/librustc_passes/loops.rs b/src/librustc_passes/loops.rs
index 616e6974110..afe4c78dcfc 100644
--- a/src/librustc_passes/loops.rs
+++ b/src/librustc_passes/loops.rs
@@ -13,26 +13,9 @@ use syntax_pos::Span;
 use errors::Applicability;
 
 #[derive(Clone, Copy, Debug, PartialEq)]
-enum LoopKind {
-    Loop(hir::LoopSource),
-    WhileLoop,
-}
-
-impl LoopKind {
-    fn name(self) -> &'static str {
-        match self {
-            LoopKind::Loop(hir::LoopSource::Loop) => "loop",
-            LoopKind::Loop(hir::LoopSource::WhileLet) => "while let",
-            LoopKind::Loop(hir::LoopSource::ForLoop) => "for",
-            LoopKind::WhileLoop => "while",
-        }
-    }
-}
-
-#[derive(Clone, Copy, Debug, PartialEq)]
 enum Context {
     Normal,
-    Loop(LoopKind),
+    Loop(hir::LoopSource),
     Closure,
     LabeledBlock,
     AnonConst,
@@ -71,14 +54,8 @@ impl<'a, 'hir> Visitor<'hir> for CheckLoopVisitor<'a, 'hir> {
 
     fn visit_expr(&mut self, e: &'hir hir::Expr) {
         match e.node {
-            hir::ExprKind::While(ref e, ref b, _) => {
-                self.with_context(Loop(LoopKind::WhileLoop), |v| {
-                    v.visit_expr(&e);
-                    v.visit_block(&b);
-                });
-            }
             hir::ExprKind::Loop(ref b, _, source) => {
-                self.with_context(Loop(LoopKind::Loop(source)), |v| v.visit_block(&b));
+                self.with_context(Loop(source), |v| v.visit_block(&b));
             }
             hir::ExprKind::Closure(_, ref function_decl, b, _, _) => {
                 self.visit_fn_decl(&function_decl);
@@ -117,15 +94,14 @@ impl<'a, 'hir> Visitor<'hir> for CheckLoopVisitor<'a, 'hir> {
                         None
                     } else {
                         Some(match self.hir_map.expect_expr(loop_id).node {
-                            hir::ExprKind::While(..) => LoopKind::WhileLoop,
-                            hir::ExprKind::Loop(_, _, source) => LoopKind::Loop(source),
+                            hir::ExprKind::Loop(_, _, source) => source,
                             ref r => span_bug!(e.span,
                                                "break label resolved to a non-loop: {:?}", r),
                         })
                     };
                     match loop_kind {
                         None |
-                        Some(LoopKind::Loop(hir::LoopSource::Loop)) => (),
+                        Some(hir::LoopSource::Loop) => (),
                         Some(kind) => {
                             struct_span_err!(self.sess, e.span, E0571,
                                              "`break` with value from a `{}` loop",
diff --git a/src/librustc_passes/rvalue_promotion.rs b/src/librustc_passes/rvalue_promotion.rs
index daa64478bca..8ba3a25e394 100644
--- a/src/librustc_passes/rvalue_promotion.rs
+++ b/src/librustc_passes/rvalue_promotion.rs
@@ -520,13 +520,6 @@ fn check_expr_kind<'a, 'tcx>(
             NotPromotable
         }
 
-        // Loops (not very meaningful in constants).
-        hir::ExprKind::While(ref expr, ref box_block, ref _option_label) => {
-            let _ = v.check_expr(expr);
-            let _ = v.check_block(box_block);
-            NotPromotable
-        }
-
         hir::ExprKind::Loop(ref box_block, ref _option_label, ref _loop_source) => {
             let _ = v.check_block(box_block);
             NotPromotable
diff --git a/src/librustc_typeck/check/expr.rs b/src/librustc_typeck/check/expr.rs
index 603726dfe23..b02a7c21027 100644
--- a/src/librustc_typeck/check/expr.rs
+++ b/src/librustc_typeck/check/expr.rs
@@ -159,11 +159,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         // Warn for non-block expressions with diverging children.
         match expr.node {
-            ExprKind::Block(..) |
-            ExprKind::Loop(..) | ExprKind::While(..) |
-            ExprKind::Match(..) => {}
-
-            _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression")
+            ExprKind::Block(..) | ExprKind::Loop(..) | ExprKind::Match(..) => {},
+            _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression"),
         }
 
         // Any expression that produces a value of type `!` must have diverged
@@ -245,9 +242,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             ExprKind::Assign(ref lhs, ref rhs) => {
                 self.check_expr_assign(expr, expected, lhs, rhs)
             }
-            ExprKind::While(ref cond, ref body, _) => {
-                self.check_expr_while(cond, body, expr)
-            }
             ExprKind::Loop(ref body, _, source) => {
                 self.check_expr_loop(body, source, expected, expr)
             }
@@ -702,36 +696,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
     }
 
-    fn check_expr_while(
-        &self,
-        cond: &'tcx hir::Expr,
-        body: &'tcx hir::Block,
-        expr: &'tcx hir::Expr
-    ) -> Ty<'tcx> {
-        let ctxt = BreakableCtxt {
-            // Cannot use break with a value from a while loop.
-            coerce: None,
-            may_break: false, // Will get updated if/when we find a `break`.
-        };
-
-        let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
-            self.check_expr_has_type_or_error(&cond, self.tcx.types.bool);
-            let cond_diverging = self.diverges.get();
-            self.check_block_no_value(&body);
-
-            // We may never reach the body so it diverging means nothing.
-            self.diverges.set(cond_diverging);
-        });
-
-        if ctxt.may_break {
-            // No way to know whether it's diverging because
-            // of a `break` or an outer `break` or `return`.
-            self.diverges.set(Diverges::Maybe);
-        }
-
-        self.tcx.mk_unit()
-    }
-
     fn check_expr_loop(
         &self,
         body: &'tcx hir::Block,
@@ -746,6 +710,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 Some(CoerceMany::new(coerce_to))
             }
 
+            hir::LoopSource::While |
             hir::LoopSource::WhileLet |
             hir::LoopSource::ForLoop => {
                 None
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index efe9079e19e..5b19614a5b3 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -3865,7 +3865,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             match expression.node {
                 ExprKind::Call(..) |
                 ExprKind::MethodCall(..) |
-                ExprKind::While(..) |
                 ExprKind::Loop(..) |
                 ExprKind::Match(..) |
                 ExprKind::Block(..) => {
diff --git a/src/librustc_typeck/check/regionck.rs b/src/librustc_typeck/check/regionck.rs
index c66d746d6e0..f9ebe762e52 100644
--- a/src/librustc_typeck/check/regionck.rs
+++ b/src/librustc_typeck/check/regionck.rs
@@ -685,16 +685,6 @@ impl<'a, 'tcx> Visitor<'tcx> for RegionCtxt<'a, 'tcx> {
                 self.set_repeating_scope(repeating_scope);
             }
 
-            hir::ExprKind::While(ref cond, ref body, _) => {
-                let repeating_scope = self.set_repeating_scope(cond.hir_id);
-                self.visit_expr(&cond);
-
-                self.set_repeating_scope(body.hir_id);
-                self.visit_block(&body);
-
-                self.set_repeating_scope(repeating_scope);
-            }
-
             hir::ExprKind::Ret(Some(ref ret_expr)) => {
                 let call_site_scope = self.call_site_scope;
                 debug!(