Fix ICE with 'while let (..) = x.iter()'

clippy_lints/src/loops.rs

@@ -488,12 +488,18 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
                 let iter_expr = &method_args[0];
                 let lhs_constructor = last_path_segment(qpath);
                 if method_path.ident.name == "next" && match_trait_method(cx, match_expr, &paths::ITERATOR)
-                    && lhs_constructor.ident.name == "Some" && !is_refutable(cx, &pat_args[0])
-                    && !is_iterator_used_after_while_let(cx, iter_expr)
-                    && !is_nested(cx, expr, &method_args[0])
+                    && lhs_constructor.ident.name == "Some" && (
+                        pat_args.is_empty()
+                        || !is_refutable(cx, &pat_args[0])
+                        && !is_iterator_used_after_while_let(cx, iter_expr)
+                        && !is_nested(cx, expr, &method_args[0]))
                 {
                     let iterator = snippet(cx, method_args[0].span, "_");
-                    let loop_var = snippet(cx, pat_args[0].span, "_");
+                    let loop_var = if pat_args.is_empty() {
+                        "_".to_string()
+                    } else {
+                        snippet(cx, pat_args[0].span, "_").into_owned()
+                    };
                     span_lint_and_sugg(
                         cx,
                         WHILE_LET_ON_ITERATOR,

tests/ui/while_loop.rs

@@ -201,4 +201,13 @@ fn refutable() {
     while let Some(&value) = values.iter().next() {
         values.remove(&value);
     }
+
+    // This should not cause an ICE and suggest:
+    //
+    // for _ in values.iter() {}
+    //
+    // See #2965
+    while let Some(..) = values.iter().next() {
+        values.remove(&1);
+    }
 }

tests/ui/while_loop.stderr

@@ -105,5 +105,11 @@ error: this loop could be written as a `for` loop
 183 |         while let Some(v) = y.next() { // use a for loop here
     |                             ^^^^^^^^ help: try: `for v in y { .. }`
 
-error: aborting due to 11 previous errors
+error: this loop could be written as a `for` loop
+   --> $DIR/while_loop.rs:210:26
+    |
+210 |     while let Some(..) = values.iter().next() {
+    |                          ^^^^^^^^^^^^^^^^^^^^ help: try: `for _ in values.iter() { .. }`
+
+error: aborting due to 12 previous errors