Fix missing WhileLet pattern scope

src/librustc_resolve/lib.rs

@@ -2897,8 +2897,10 @@ impl<'a> Resolver<'a> {
             ExprKind::WhileLet(ref pattern, ref subexpression, ref block, label) => {
                 self.with_resolved_label(label, expr.id, |this| {
                     this.visit_expr(subexpression);
+                    this.ribs[ValueNS].push(Rib::new(NormalRibKind));
                     this.resolve_pattern(pattern, PatternSource::WhileLet, &mut FxHashMap());
                     this.visit_block(block);
+                    this.ribs[ValueNS].pop();
                 });
             }
 

src/test/run-pass/issue-40235.rs

@@ -0,0 +1,16 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+fn foo() {}
+
+fn main() {
+    while let Some(foo) = Some(1) { break }
+    foo();
+}