From eadd9d24dcd7c84c96dcd17234b8aadf9a113bd3 Mon Sep 17 00:00:00 2001
From: flip1995 <hello@philkrones.com>
Date: Sat, 25 Apr 2020 20:51:02 +0200
Subject: [PATCH] Don't trigger while_let_on_iterator when the iterator is
 recreated every iteration

---
 clippy_lints/src/loops.rs | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/clippy_lints/src/loops.rs b/clippy_lints/src/loops.rs
index 56dd2795c60..6e9b7f685eb 100644
--- a/clippy_lints/src/loops.rs
+++ b/clippy_lints/src/loops.rs
@@ -566,6 +566,17 @@ fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
             ) = (pat, &match_expr.kind)
             {
                 let iter_expr = &method_args[0];
+
+                // Don't lint when the iterator is recreated on every iteration
+                if_chain! {
+                    if let ExprKind::MethodCall(..) | ExprKind::Call(..) = iter_expr.kind;
+                    if let Some(iter_def_id) = get_trait_def_id(cx, &paths::ITERATOR);
+                    if implements_trait(cx, cx.tables.expr_ty(iter_expr), iter_def_id, &[]);
+                    then {
+                        return;
+                    }
+                }
+
                 let lhs_constructor = last_path_segment(qpath);
                 if method_path.ident.name == sym!(next)
                     && match_trait_method(cx, match_expr, &paths::ITERATOR)