library: C++23 — deducing this for some recursive lambdas (#229)

* tests/infra: move to c++23 (std pins, g++-14 in CI, deducing this in tests)

* revert deducing this in member-function lambdas (gcc 14/15 bug PR118291)

* library: c++23 deducing this for all 22 recursive lambdas; tester.sh to c++23

* revert deducing this in member-function lambdas (gcc 14/15 bug PR118291)

* suppress clang-tidy suspicious-call-argument false positive in min_plus dnc; generalize NOLINT strip in update_main

* [auto-verifier] verify commit a12b59b

* [auto-verifier] verify commit ce89ffc

---------

Co-authored-by: Cameron Custer <cam@augmentcode.com>
Co-authored-by: GitHub <noreply@github.com>

Author: 3 people

.verify-helper/timestamps.remote.json

@@ -1,7 +1,7 @@
 {
 "tests/library_checker_aizu_tests/convolution/gcd_convolution.test.cpp": "2026-07-06 13:10:16 -0700",
 "tests/library_checker_aizu_tests/convolution/lcm_convolution.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/convolution/min_plus_convolution.test.cpp": "2026-07-06 13:10:16 -0700",
+"tests/library_checker_aizu_tests/convolution/min_plus_convolution.test.cpp": "2026-07-06 22:52:18 -0700",
 "tests/library_checker_aizu_tests/convolution/xor_convolution.test.cpp": "2026-07-06 13:10:16 -0700",
 "tests/library_checker_aizu_tests/data_structures/binary_search_example.test.cpp": "2026-07-06 13:10:16 -0700",
 "tests/library_checker_aizu_tests/data_structures/binary_trie.test.cpp": "2026-07-06 11:00:20 -0700",
@@ -30,7 +30,7 @@
 "tests/library_checker_aizu_tests/data_structures/lazy_segment_tree_inc_constructor.test.cpp": "2026-07-06 13:10:16 -0700",
 "tests/library_checker_aizu_tests/data_structures/merge_sort_tree.test.cpp": "2026-07-06 13:10:16 -0700",
 "tests/library_checker_aizu_tests/data_structures/mode_query.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/data_structures/permutation_tree.test.cpp": "2026-07-06 22:18:09 -0700",
+"tests/library_checker_aizu_tests/data_structures/permutation_tree.test.cpp": "2026-07-07 09:17:02 -0700",
 "tests/library_checker_aizu_tests/data_structures/persistent_queue_tree.test.cpp": "2026-07-06 13:10:16 -0700",
 "tests/library_checker_aizu_tests/data_structures/persistent_seg_tree.test.cpp": "2026-07-06 13:10:16 -0700",
 "tests/library_checker_aizu_tests/data_structures/pq_ds_undo_sliding_window.test.cpp": "2026-07-06 13:10:16 -0700",
@@ -49,39 +49,39 @@
 "tests/library_checker_aizu_tests/dsu/dsu_bipartite.test.cpp": "2026-07-06 13:10:16 -0700",
 "tests/library_checker_aizu_tests/dsu/dsu_weighted_aizu.test.cpp": "2026-07-06 13:49:19 -0700",
 "tests/library_checker_aizu_tests/dsu/dsu_weighted_lib_checker.test.cpp": "2026-07-06 13:49:19 -0700",
-"tests/library_checker_aizu_tests/dsu/kruskal_tree_aizu.test.cpp": "2026-07-06 22:18:09 -0700",
+"tests/library_checker_aizu_tests/dsu/kruskal_tree_aizu.test.cpp": "2026-07-07 09:17:02 -0700",
 "tests/library_checker_aizu_tests/dsu/line_tree_aizu.test.cpp": "2026-07-06 13:10:16 -0700",
 "tests/library_checker_aizu_tests/dsu/line_tree_lib_checker.test.cpp": "2026-07-06 13:10:16 -0700",
 "tests/library_checker_aizu_tests/dsu/range_parallel_dsu.test.cpp": "2026-07-06 13:10:16 -0700",
 "tests/library_checker_aizu_tests/flow/hungarian.test.cpp": "2026-07-06 13:09:48 -0700",
 "tests/library_checker_aizu_tests/flow/min_cost_max_flow.test.cpp": "2026-04-06 14:41:55 -0600",
-"tests/library_checker_aizu_tests/graphs/bcc_callback_aizu_bcc.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/graphs/bcc_callback_aizu_two_edge_cc.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/graphs/bcc_callback_lib_checker_bcc.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/graphs/bcc_callback_lib_checker_two_cc.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/graphs/biconnected_components.test.cpp": "2026-07-06 13:10:16 -0700",
+"tests/library_checker_aizu_tests/graphs/bcc_callback_aizu_bcc.test.cpp": "2026-07-06 22:30:55 -0700",
+"tests/library_checker_aizu_tests/graphs/bcc_callback_aizu_two_edge_cc.test.cpp": "2026-07-06 22:30:55 -0700",
+"tests/library_checker_aizu_tests/graphs/bcc_callback_lib_checker_bcc.test.cpp": "2026-07-06 22:30:55 -0700",
+"tests/library_checker_aizu_tests/graphs/bcc_callback_lib_checker_two_cc.test.cpp": "2026-07-06 22:30:55 -0700",
+"tests/library_checker_aizu_tests/graphs/biconnected_components.test.cpp": "2026-07-06 22:30:55 -0700",
 "tests/library_checker_aizu_tests/graphs/connected_components_of_complement_graph.test.cpp": "2026-07-06 13:10:16 -0700",
 "tests/library_checker_aizu_tests/graphs/dijkstra_aizu.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/graphs/dijkstra_lib_checker.test.cpp": "2026-07-06 22:18:09 -0700",
-"tests/library_checker_aizu_tests/graphs/directed_cycle.test.cpp": "2026-07-06 13:10:16 -0700",
+"tests/library_checker_aizu_tests/graphs/dijkstra_lib_checker.test.cpp": "2026-07-07 09:17:02 -0700",
+"tests/library_checker_aizu_tests/graphs/directed_cycle.test.cpp": "2026-07-06 22:30:55 -0700",
 "tests/library_checker_aizu_tests/graphs/enumerate_triangles.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/graphs/euler_walk_directed.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/graphs/euler_walk_undirected.test.cpp": "2026-07-06 13:10:16 -0700",
+"tests/library_checker_aizu_tests/graphs/euler_walk_directed.test.cpp": "2026-07-06 22:30:55 -0700",
+"tests/library_checker_aizu_tests/graphs/euler_walk_undirected.test.cpp": "2026-07-06 22:30:55 -0700",
 "tests/library_checker_aizu_tests/graphs/hopcroft_karp_aizu.test.cpp": "2026-07-06 13:10:16 -0700",
 "tests/library_checker_aizu_tests/graphs/hopcroft_karp_lib_checker.test.cpp": "2026-07-06 13:10:16 -0700",
 "tests/library_checker_aizu_tests/graphs/mst.test.cpp": "2026-07-06 13:09:48 -0700",
-"tests/library_checker_aizu_tests/graphs/offline_incremental_scc.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/graphs/strongly_connected_components_aizu.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/graphs/strongly_connected_components_lib_checker.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/graphs/two_edge_components.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/handmade_tests/count_paths.test.cpp": "2026-07-06 22:18:09 -0700",
-"tests/library_checker_aizu_tests/handmade_tests/dsu.test.cpp": "2026-07-06 22:18:09 -0700",
-"tests/library_checker_aizu_tests/handmade_tests/edge_cd_small_trees.test.cpp": "2026-07-06 22:18:09 -0700",
+"tests/library_checker_aizu_tests/graphs/offline_incremental_scc.test.cpp": "2026-07-06 22:30:55 -0700",
+"tests/library_checker_aizu_tests/graphs/strongly_connected_components_aizu.test.cpp": "2026-07-06 22:30:55 -0700",
+"tests/library_checker_aizu_tests/graphs/strongly_connected_components_lib_checker.test.cpp": "2026-07-06 22:30:55 -0700",
+"tests/library_checker_aizu_tests/graphs/two_edge_components.test.cpp": "2026-07-06 22:30:55 -0700",
+"tests/library_checker_aizu_tests/handmade_tests/count_paths.test.cpp": "2026-07-06 22:44:57 -0700",
+"tests/library_checker_aizu_tests/handmade_tests/dsu.test.cpp": "2026-07-07 09:17:02 -0700",
+"tests/library_checker_aizu_tests/handmade_tests/edge_cd_small_trees.test.cpp": "2026-07-06 22:30:55 -0700",
 "tests/library_checker_aizu_tests/handmade_tests/fib_matrix_expo.test.cpp": "2026-07-06 13:10:16 -0700",
 "tests/library_checker_aizu_tests/handmade_tests/functional_graph.test.cpp": "2026-07-06 22:43:37 -0700",
 "tests/library_checker_aizu_tests/handmade_tests/hilbert_mos.test.cpp": "2026-07-06 13:10:16 -0700",
 "tests/library_checker_aizu_tests/handmade_tests/kd_bit.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/handmade_tests/kth_par.test.cpp": "2026-07-06 13:10:16 -0700",
+"tests/library_checker_aizu_tests/handmade_tests/kth_par.test.cpp": "2026-07-06 22:44:57 -0700",
 "tests/library_checker_aizu_tests/handmade_tests/manacher.test.cpp": "2026-07-06 13:10:16 -0700",
 "tests/library_checker_aizu_tests/handmade_tests/merge_st_and_wavelet.test.cpp": "2026-07-06 13:10:16 -0700",
 "tests/library_checker_aizu_tests/handmade_tests/mobius.test.cpp": "2026-07-06 13:10:16 -0700",
@@ -92,7 +92,7 @@
 "tests/library_checker_aizu_tests/handmade_tests/sa_find_subarray.test.cpp": "2026-07-06 13:10:16 -0700",
 "tests/library_checker_aizu_tests/handmade_tests/seg_tree_find.test.cpp": "2026-07-06 13:10:16 -0700",
 "tests/library_checker_aizu_tests/handmade_tests/seg_tree_find_small.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/handmade_tests/seg_tree_midpoint.test.cpp": "2026-07-06 22:18:09 -0700",
+"tests/library_checker_aizu_tests/handmade_tests/seg_tree_midpoint.test.cpp": "2026-07-07 09:17:02 -0700",
 "tests/library_checker_aizu_tests/handmade_tests/xor_basis_walk.test.cpp": "2026-07-06 13:10:16 -0700",
 "tests/library_checker_aizu_tests/loops/chooses.test.cpp": "2026-07-06 13:10:16 -0700",
 "tests/library_checker_aizu_tests/loops/quotients.test.cpp": "2026-07-06 13:10:16 -0700",
@@ -132,23 +132,23 @@
 "tests/library_checker_aizu_tests/strings/suffix_array_short.test.cpp": "2026-04-12 06:15:25 -0600",
 "tests/library_checker_aizu_tests/strings/trie.test.cpp": "2026-07-06 13:10:16 -0700",
 "tests/library_checker_aizu_tests/strings/wildcard_pattern_matching.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/trees/cd_count_paths_per_length.test.cpp": "2026-07-06 22:18:09 -0700",
-"tests/library_checker_aizu_tests/trees/edge_cd_contour_range_query.test.cpp": "2026-07-06 22:43:37 -0700",
-"tests/library_checker_aizu_tests/trees/edge_cd_contour_range_update.test.cpp": "2026-07-06 22:43:37 -0700",
-"tests/library_checker_aizu_tests/trees/edge_cd_count_paths_per_length.test.cpp": "2026-07-06 22:18:09 -0700",
-"tests/library_checker_aizu_tests/trees/edge_cd_reroot_dp.test.cpp": "2026-07-06 22:18:09 -0700",
-"tests/library_checker_aizu_tests/trees/hld_aizu1.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/trees/hld_aizu2.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/trees/hld_lib_checker_path.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/trees/hld_lib_checker_subtree_edges.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/trees/hld_lib_checker_subtree_nodes.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/trees/kth_path_hagerup.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/trees/kth_path_ladder.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/trees/kth_path_linear.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/trees/kth_path_tree_lift.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/trees/lca_all_methods_aizu.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/trees/lca_all_methods_lib_checker.test.cpp": "2026-07-06 13:10:16 -0700",
-"tests/library_checker_aizu_tests/trees/shallowest_aizu_tree_height.test.cpp": "2026-07-06 22:18:09 -0700",
-"tests/library_checker_aizu_tests/trees/shallowest_lib_checker_tree_path_composite.test.cpp": "2026-07-06 22:18:09 -0700",
-"tests/library_checker_aizu_tests/trees/subtree_isomorphism.test.cpp": "2026-07-06 13:10:16 -0700"
+"tests/library_checker_aizu_tests/trees/cd_count_paths_per_length.test.cpp": "2026-07-06 22:30:55 -0700",
+"tests/library_checker_aizu_tests/trees/edge_cd_contour_range_query.test.cpp": "2026-07-06 22:30:55 -0700",
+"tests/library_checker_aizu_tests/trees/edge_cd_contour_range_update.test.cpp": "2026-07-06 22:30:55 -0700",
+"tests/library_checker_aizu_tests/trees/edge_cd_count_paths_per_length.test.cpp": "2026-07-06 22:30:55 -0700",
+"tests/library_checker_aizu_tests/trees/edge_cd_reroot_dp.test.cpp": "2026-07-06 22:30:55 -0700",
+"tests/library_checker_aizu_tests/trees/hld_aizu1.test.cpp": "2026-07-06 22:44:57 -0700",
+"tests/library_checker_aizu_tests/trees/hld_aizu2.test.cpp": "2026-07-06 22:44:57 -0700",
+"tests/library_checker_aizu_tests/trees/hld_lib_checker_path.test.cpp": "2026-07-06 22:44:57 -0700",
+"tests/library_checker_aizu_tests/trees/hld_lib_checker_subtree_edges.test.cpp": "2026-07-06 22:44:57 -0700",
+"tests/library_checker_aizu_tests/trees/hld_lib_checker_subtree_nodes.test.cpp": "2026-07-06 22:44:57 -0700",
+"tests/library_checker_aizu_tests/trees/kth_path_hagerup.test.cpp": "2026-07-06 22:44:57 -0700",
+"tests/library_checker_aizu_tests/trees/kth_path_ladder.test.cpp": "2026-07-06 22:44:57 -0700",
+"tests/library_checker_aizu_tests/trees/kth_path_linear.test.cpp": "2026-07-06 22:44:57 -0700",
+"tests/library_checker_aizu_tests/trees/kth_path_tree_lift.test.cpp": "2026-07-06 22:44:57 -0700",
+"tests/library_checker_aizu_tests/trees/lca_all_methods_aizu.test.cpp": "2026-07-06 22:44:57 -0700",
+"tests/library_checker_aizu_tests/trees/lca_all_methods_lib_checker.test.cpp": "2026-07-06 22:44:57 -0700",
+"tests/library_checker_aizu_tests/trees/shallowest_aizu_tree_height.test.cpp": "2026-07-06 22:30:55 -0700",
+"tests/library_checker_aizu_tests/trees/shallowest_lib_checker_tree_path_composite.test.cpp": "2026-07-06 22:30:55 -0700",
+"tests/library_checker_aizu_tests/trees/subtree_isomorphism.test.cpp": "2026-07-06 22:30:55 -0700"
 }

library/contest/tester.sh

@@ -1,9 +1,9 @@
 # https://github.com/Errichto/youtube/blob/master/testing/s.sh
 # bash tester.sh a naive gen
 
-g++ -std=c++20 -g -D_GLIBCXX_DEBUG -fsanitize=address,undefined $1.cpp -o $1.out
-g++ -std=c++20 $2.cpp -o $2.out
-g++ -std=c++20 $3.cpp -o $3.out
+g++ -std=c++23 -g -D_GLIBCXX_DEBUG -fsanitize=address,undefined $1.cpp -o $1.out
+g++ -std=c++23 $2.cpp -o $2.out
+g++ -std=c++23 $3.cpp -o $3.out
 
 for((i = 1; ; ++i))
 do

library/convolution/min_plus_convolution_convex_and_arbitrary.hpp

@@ -9,7 +9,7 @@ vi min_plus(const vi& convex, const vi& arbitrary) {
   int n = sz(convex);
   int m = sz(arbitrary);
   vi res(n + m - 1, INT_MAX);
-  auto dnc = [&](auto&& dnc, int res_le, int res_ri,
+  auto dnc = [&](this auto&& dnc, int res_le, int res_ri,
                int arb_le, int arb_ri) {
     if (res_le >= res_ri) return;
     int mid_res = (res_le + res_ri) / 2;
@@ -22,10 +22,10 @@ vi min_plus(const vi& convex, const vi& arbitrary) {
         op_arb = i;
       }
     }
-    dnc(dnc, res_le, mid_res, arb_le,
-      min(arb_ri, op_arb + 1));
-    dnc(dnc, mid_res + 1, res_ri, op_arb, arb_ri);
+    dnc(res_le, mid_res, arb_le, min(arb_ri, op_arb + 1));
+    // NOLINTNEXTLINE(readability-suspicious-call-argument)
+    dnc(mid_res + 1, res_ri, op_arb, arb_ri);
   };
-  dnc(dnc, 0, n + m - 1, 0, m);
+  dnc(0, n + m - 1, 0, m);
   return res;
 }

library/graphs/bcc_callback.hpp

@@ -44,11 +44,11 @@
 void bcc(const auto& g, auto f) {
   int n = sz(g), q = 0, s = 0;
   vi t(n), st(n);
-  auto dfs = [&](auto&& dfs, int u) -> int {
+  auto dfs = [&](this auto&& dfs, int u) -> int {
     int l = t[u] = ++q;
     for (int v : g[u]) {
       int siz = s, lu = 0;
-      l = min(l, t[v] ?: (lu = dfs(dfs, st[s++] = v)));
+      l = min(l, t[v] ?: (lu = dfs(st[s++] = v)));
       if (lu >= t[u]) {
         st[s++] = u;
         f({siz + all(st) - n + s});
@@ -57,5 +57,5 @@ void bcc(const auto& g, auto f) {
     }
     return l;
   };
-  rep(i, 0, n) if (!t[i]) dfs(dfs, i);
+  rep(i, 0, n) if (!t[i]) dfs(i);
 }

library/graphs/euler_path.hpp

@@ -16,15 +16,15 @@
 vector<pii> euler_path(auto& g, int m, int s) {
   vi vis(m);
   vector<pii> path;
-  auto dfs = [&](auto&& dfs, int u, int eu) -> void {
+  auto dfs = [&](this auto&& dfs, int u, int eu) -> void {
     while (!empty(g[u])) {
       auto [v, ev] = g[u].back();
       g[u].pop_back();
-      if (!vis[ev]) vis[ev] = 1, dfs(dfs, v, ev);
+      if (!vis[ev]) vis[ev] = 1, dfs(v, ev);
     }
     path.emplace_back(u, eu);
   };
-  dfs(dfs, s, -1);
+  dfs(s, -1);
   ranges::reverse(path);
   return path;
 }

library/graphs/scc.hpp

@@ -11,18 +11,17 @@
 auto scc(const auto& g) {
   int n = sz(g), num_sccs = 0, q = 0, s = 0;
   vi scc_id(n, -1), tin(n), st(n);
-  auto dfs = [&](auto&& dfs, int u) -> int {
+  auto dfs = [&](this auto&& dfs, int u) -> int {
     int low = tin[u] = ++q;
     st[s++] = u;
     for (int v : g[u])
-      if (scc_id[v] < 0)
-        low = min(low, tin[v] ?: dfs(dfs, v));
+      if (scc_id[v] < 0) low = min(low, tin[v] ?: dfs(v));
     if (tin[u] == low) {
       while (scc_id[u] < 0) scc_id[st[--s]] = num_sccs;
       num_sccs++;
     }
     return low;
   };
-  rep(i, 0, n) if (!tin[i]) dfs(dfs, i);
+  rep(i, 0, n) if (!tin[i]) dfs(i);
   return pair{num_sccs, scc_id};
 }

library/graphs/strongly_connected_components/add_edges_strongly_connected.hpp

@@ -29,12 +29,12 @@ vector<pii> extra_edges(const auto& g, int num_sccs,
     zero_in[scc_id[v]] = 0;
   }
   vector<bool> vis(num_sccs);
-  auto dfs = [&](auto&& dfs, int u) {
+  auto dfs = [&](this auto&& dfs, int u) {
     if (empty(scc_g[u])) return u;
     for (int v : scc_g[u])
       if (!vis[v]) {
         vis[v] = 1;
-        int zero_out = dfs(dfs, v);
+        int zero_out = dfs(v);
         if (zero_out != -1) return zero_out;
       }
     return -1;
@@ -43,7 +43,7 @@ vector<pii> extra_edges(const auto& g, int num_sccs,
   vi in_unused;
   rep(i, 0, num_sccs) if (zero_in[i]) {
     vis[i] = 1;
-    int zero_out = dfs(dfs, i);
+    int zero_out = dfs(i);
     if (zero_out != -1) edges.emplace_back(zero_out, i);
     else in_unused.push_back(i);
   }

library/graphs/strongly_connected_components/offline_incremental_scc.hpp

@@ -16,7 +16,7 @@ vi offline_incremental_scc(vector<array<int, 2>> eds,
   vi ids(n, -1), joins(m, m), idx(m), vs(n), scc_id;
   iota(all(idx), 0);
   vector<vi> g;
-  auto dnc = [&](auto&& dnc, auto el, auto er, int tl,
+  auto dnc = [&](this auto&& dnc, auto el, auto er, int tl,
                int tr) {
     g.clear();
     int mid = midpoint(tl, tr);
@@ -42,11 +42,11 @@ vi offline_incremental_scc(vector<array<int, 2>> eds,
       auto& [u, v] = eds[*it];
       u = scc_id[u], v = scc_id[v];
     }
-    dnc(dnc, el, split, tl, mid);
-    dnc(dnc, split, er, mid, tr);
+    dnc(el, split, tl, mid);
+    dnc(split, er, mid, tr);
   };
   // uses -1 as the lower bound to correctly handle
   // self-edges
-  dnc(dnc, all(idx), -1, m);
+  dnc(all(idx), -1, m);
   return joins;
 }

library/graphs/uncommon/bridges.hpp

@@ -18,19 +18,19 @@
 auto bridges(const auto& g, int m) {
   int n = sz(g), num_ccs = 0, q = 0, s = 0;
   vi br_id(n, -1), is_br(m), tin(n), st(n);
-  auto dfs = [&](auto&& dfs, int u, int p) -> int {
+  auto dfs = [&](this auto&& dfs, int u, int p) -> int {
     int low = tin[u] = ++q;
     st[s++] = u;
     for (auto [v, e] : g[u])
       if (e != p && br_id[v] < 0)
-        low = min(low, tin[v] ?: dfs(dfs, v, e));
+        low = min(low, tin[v] ?: dfs(v, e));
     if (tin[u] == low) {
       if (p != -1) is_br[p] = 1;
       while (br_id[u] < 0) br_id[st[--s]] = num_ccs;
       num_ccs++;
     }
     return low;
   };
-  rep(i, 0, n) if (!tin[i]) dfs(dfs, i, -1);
+  rep(i, 0, n) if (!tin[i]) dfs(i, -1);
   return tuple{num_ccs, br_id, is_br};
 }

library/graphs/uncommon/cuts.hpp

@@ -19,14 +19,14 @@
 auto cuts(const auto& g, int m) {
   int n = sz(g), num_bccs = 0, q = 0, s = 0;
   vi bcc_id(m, -1), is_cut(n), tin(n), st(m);
-  auto dfs = [&](auto&& dfs, int u, int p) -> int {
+  auto dfs = [&](this auto&& dfs, int u, int p) -> int {
     int low = tin[u] = ++q;
     for (auto [v, e] : g[u]) {
       assert(u != v);
       if (e == p) continue;
       if (tin[v] < tin[u]) st[s++] = e;
       int lu = -1;
-      low = min(low, tin[v] ?: (lu = dfs(dfs, v, e)));
+      low = min(low, tin[v] ?: (lu = dfs(v, e)));
       if (lu >= tin[u]) {
         is_cut[u] = p >= 0 || tin[u] + 1 < tin[v];
         while (bcc_id[e] < 0) bcc_id[st[--s]] = num_bccs;
@@ -35,6 +35,6 @@ auto cuts(const auto& g, int m) {
     }
     return low;
   };
-  rep(i, 0, n) if (!tin[i]) dfs(dfs, i, -1);
+  rep(i, 0, n) if (!tin[i]) dfs(i, -1);
   return tuple{num_bccs, bcc_id, is_cut};
 }