Handle while let desugaring

src/librustc/diagnostics.rs

@@ -150,5 +150,6 @@ register_diagnostics!(
     E0161,
     E0162,
     E0163,
-    E0164
+    E0164,
+    E0165
 )

src/librustc/lint/builtin.rs

@@ -1082,7 +1082,8 @@ impl LintPass for UnnecessaryParens {
             ast::ExprWhile(ref cond, _, _) => (cond, "`while` condition", true),
             ast::ExprMatch(ref head, _, source) => match source {
                 ast::MatchNormal => (head, "`match` head expression", true),
-                ast::MatchIfLetDesugar => (head, "`if let` head expression", true)
+                ast::MatchIfLetDesugar => (head, "`if let` head expression", true),
+                ast::MatchWhileLetDesugar => (head, "`while let` head expression", true),
             },
             ast::ExprRet(Some(ref value)) => (value, "`return` value", false),
             ast::ExprAssign(_, ref value) => (value, "assigned value", false),

src/librustc/middle/cfg/construct.rs

@@ -259,6 +259,10 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
                 expr_exit
             }
 
+            ast::ExprWhileLet(..) => {
+                self.tcx.sess.span_bug(expr.span, "non-desugared ExprWhileLet");
+            }
+
             ast::ExprForLoop(ref pat, ref head, ref body, _) => {
                 //
                 //          [pred]

src/librustc/middle/check_match.rs

@@ -261,20 +261,30 @@ fn check_arms(cx: &MatchCheckCtxt, arms: &[(Vec<P<Pat>>, Option<&Expr>)], source
 
             match is_useful(cx, &seen, v.as_slice(), LeaveOutWitness) {
                 NotUseful => {
-                    if source == MatchIfLetDesugar {
-                        if printed_if_let_err {
-                            // we already printed an irrefutable if-let pattern error.
-                            // We don't want two, that's just confusing.
-                        } else {
+                    match source {
+                        MatchIfLetDesugar => {
+                            if printed_if_let_err {
+                                // we already printed an irrefutable if-let pattern error.
+                                // We don't want two, that's just confusing.
+                            } else {
+                                // find the first arm pattern so we can use its span
+                                let &(ref first_arm_pats, _) = &arms[0];
+                                let first_pat = first_arm_pats.get(0);
+                                let span = first_pat.span;
+                                span_err!(cx.tcx.sess, span, E0162, "irrefutable if-let pattern");
+                                printed_if_let_err = true;
+                            }
+                        },
+
+                        MatchWhileLetDesugar => {
                             // find the first arm pattern so we can use its span
                             let &(ref first_arm_pats, _) = &arms[0];
                             let first_pat = first_arm_pats.get(0);
                             let span = first_pat.span;
-                            span_err!(cx.tcx.sess, span, E0162, "irrefutable if-let pattern");
-                            printed_if_let_err = true;
-                        }
-                    } else {
-                        span_err!(cx.tcx.sess, pat.span, E0001, "unreachable pattern");
+                            span_err!(cx.tcx.sess, span, E0165, "irrefutable while-let pattern");
+                        },
+
+                        _ => span_err!(cx.tcx.sess, pat.span, E0001, "unreachable pattern")
                     }
                 }
                 Useful => (),

src/librustc/middle/expr_use_visitor.rs

@@ -429,6 +429,10 @@ impl<'d,'t,'tcx,TYPER:mc::Typer<'tcx>> ExprUseVisitor<'d,'t,TYPER> {
                 self.walk_block(&**blk);
             }
 
+            ast::ExprWhileLet(..) => {
+                self.tcx().sess.span_bug(expr.span, "non-desugared ExprWhileLet");
+            }
+
             ast::ExprForLoop(ref pat, ref head, ref blk, _) => {
                 // The pattern lives as long as the block.
                 debug!("walk_expr for loop case: blk id={}", blk.id);

src/librustc/middle/liveness.rs

@@ -484,6 +484,9 @@ fn visit_expr(ir: &mut IrMaps, expr: &Expr) {
       ExprIfLet(..) => {
           ir.tcx.sess.span_bug(expr.span, "non-desugared ExprIfLet");
       }
+      ExprWhileLet(..) => {
+          ir.tcx.sess.span_bug(expr.span, "non-desugared ExprWhileLet");
+      }
       ExprForLoop(ref pat, _, _, _) => {
         pat_util::pat_bindings(&ir.tcx.def_map, &**pat, |bm, p_id, sp, path1| {
             debug!("adding local variable {} from for loop with bm {:?}",
@@ -1022,6 +1025,10 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
             self.propagate_through_loop(expr, WhileLoop(&**cond), &**blk, succ)
           }
 
+          ExprWhileLet(..) => {
+              self.ir.tcx.sess.span_bug(expr.span, "non-desugared ExprWhileLet");
+          }
+
           ExprForLoop(ref pat, ref head, ref blk, _) => {
             let ln = self.propagate_through_loop(expr, ForLoop(&**pat), &**blk, succ);
             self.propagate_through_expr(&**head, ln)
@@ -1480,6 +1487,9 @@ fn check_expr(this: &mut Liveness, expr: &Expr) {
       ExprIfLet(..) => {
         this.ir.tcx.sess.span_bug(expr.span, "non-desugared ExprIfLet");
       }
+      ExprWhileLet(..) => {
+        this.ir.tcx.sess.span_bug(expr.span, "non-desugared ExprWhileLet");
+      }
     }
 }
 

src/librustc/middle/mem_categorization.rs

@@ -530,6 +530,9 @@ impl<'t,'tcx,TYPER:Typer<'tcx>> MemCategorizationContext<'t,TYPER> {
           ast::ExprIfLet(..) => {
             self.tcx().sess.span_bug(expr.span, "non-desugared ExprIfLet");
           }
+          ast::ExprWhileLet(..) => {
+            self.tcx().sess.span_bug(expr.span, "non-desugared ExprWhileLet");
+          }
         }
     }
 

src/librustc/middle/trans/debuginfo.rs

@@ -3496,6 +3496,11 @@ fn populate_scope_map(cx: &CrateContext,
                 })
             }
 
+            ast::ExprWhileLet(..) => {
+                cx.sess().span_bug(exp.span, "debuginfo::populate_scope_map() - \
+                                              Found unexpanded while-let.");
+            }
+
             ast::ExprForLoop(ref pattern, ref head, ref body, _) => {
                 walk_expr(cx, &**head, scope_stack, scope_map);
 

src/librustc/middle/ty.rs

@@ -3615,6 +3615,9 @@ pub fn expr_kind(tcx: &ctxt, expr: &ast::Expr) -> ExprKind {
         ast::ExprIfLet(..) => {
             tcx.sess.span_bug(expr.span, "non-desugared ExprIfLet");
         }
+        ast::ExprWhileLet(..) => {
+            tcx.sess.span_bug(expr.span, "non-desugared ExprWhileLet");
+        }
 
         ast::ExprLit(ref lit) if lit_is_str(&**lit) => {
             RvalueDpsExpr

src/librustc/middle/typeck/check/mod.rs

@@ -4116,6 +4116,9 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
             fcx.write_nil(id);
         }
       }
+      ast::ExprWhileLet(..) => {
+        tcx.sess.span_bug(expr.span, "non-desugared ExprWhileLet");
+      }
       ast::ExprForLoop(ref pat, ref head, ref block, _) => {
         check_expr(fcx, &**head);
         let typ = lookup_method_for_for_loop(fcx, &**head, expr.id);

src/librustc/util/ppaux.rs

@@ -93,6 +93,9 @@ pub fn explain_region_and_span(cx: &ctxt, region: ty::Region)
                 explain_span(cx, "method call", expr.span)
               },
               ast::ExprMatch(_, _, ast::MatchIfLetDesugar) => explain_span(cx, "if let", expr.span),
+              ast::ExprMatch(_, _, ast::MatchWhileLetDesugar) => {
+                  explain_span(cx, "while let", expr.span)
+              },
               ast::ExprMatch(..) => explain_span(cx, "match", expr.span),
               _ => explain_span(cx, "expression", expr.span)
             }

src/librustc_back/svh.rs

@@ -294,6 +294,7 @@ mod svh_visitor {
 
             // just syntactic artifacts, expanded away by time of SVH.
             ExprIfLet(..)            => unreachable!(),
+            ExprWhileLet(..)         => unreachable!(),
             ExprMac(..)              => unreachable!(),
         }
     }