From 27ddb001b14928854f0a36d3681fd9ad27db1389 Mon Sep 17 00:00:00 2001
From: Jakub Kuderski <jakub@nod-labs.com>
Date: Sun, 9 Mar 2025 17:40:06 -0400
Subject: [PATCH] [ADT] Use `adl_being`/`end` in `concat`

This is to make sure that ADT helpers consistently use argument
dependent lookup when dealing with input ranges.

This was a part of #87936 but reverted due to buildbot failures.
---
 llvm/include/llvm/ADT/STLExtras.h    | 17 ++++++++---------
 llvm/unittests/ADT/STLExtrasTest.cpp | 10 ++++++++++
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/llvm/include/llvm/ADT/STLExtras.h b/llvm/include/llvm/ADT/STLExtras.h
index fe1d010574e31..59becba6373d4 100644
--- a/llvm/include/llvm/ADT/STLExtras.h
+++ b/llvm/include/llvm/ADT/STLExtras.h
@@ -1112,8 +1112,8 @@ class concat_iterator
   /// We need the full range to know how to switch between each of the
   /// iterators.
   template <typename... RangeTs>
-  explicit concat_iterator(RangeTs &&... Ranges)
-      : Begins(std::begin(Ranges)...), Ends(std::end(Ranges)...) {}
+  explicit concat_iterator(RangeTs &&...Ranges)
+      : Begins(adl_begin(Ranges)...), Ends(adl_end(Ranges)...) {}
 
   using BaseT::operator++;
 
@@ -1142,13 +1142,12 @@ template <typename ValueT, typename... RangeTs> class concat_range {
 public:
   using iterator =
       concat_iterator<ValueT,
-                      decltype(std::begin(std::declval<RangeTs &>()))...>;
+                      decltype(adl_begin(std::declval<RangeTs &>()))...>;
 
 private:
   std::tuple<RangeTs...> Ranges;
 
-  template <size_t... Ns>
-  iterator begin_impl(std::index_sequence<Ns...>) {
+  template <size_t... Ns> iterator begin_impl(std::index_sequence<Ns...>) {
     return iterator(std::get<Ns>(Ranges)...);
   }
   template <size_t... Ns>
@@ -1156,12 +1155,12 @@ template <typename ValueT, typename... RangeTs> class concat_range {
     return iterator(std::get<Ns>(Ranges)...);
   }
   template <size_t... Ns> iterator end_impl(std::index_sequence<Ns...>) {
-    return iterator(make_range(std::end(std::get<Ns>(Ranges)),
-                               std::end(std::get<Ns>(Ranges)))...);
+    return iterator(make_range(adl_end(std::get<Ns>(Ranges)),
+                               adl_end(std::get<Ns>(Ranges)))...);
   }
   template <size_t... Ns> iterator end_impl(std::index_sequence<Ns...>) const {
-    return iterator(make_range(std::end(std::get<Ns>(Ranges)),
-                               std::end(std::get<Ns>(Ranges)))...);
+    return iterator(make_range(adl_end(std::get<Ns>(Ranges)),
+                               adl_end(std::get<Ns>(Ranges)))...);
   }
 
 public:
diff --git a/llvm/unittests/ADT/STLExtrasTest.cpp b/llvm/unittests/ADT/STLExtrasTest.cpp
index e107cb570641b..2b2b4ae9b9e9e 100644
--- a/llvm/unittests/ADT/STLExtrasTest.cpp
+++ b/llvm/unittests/ADT/STLExtrasTest.cpp
@@ -504,6 +504,16 @@ TEST(STLExtrasTest, ConcatRange) {
   EXPECT_EQ(Expected, Test);
 }
 
+TEST(STLExtrasTest, ConcatRangeADL) {
+  // Make sure that we use the `begin`/`end` functions from `some_namespace`,
+  // using ADL.
+  some_namespace::some_struct S0;
+  S0.data = {1, 2};
+  some_namespace::some_struct S1;
+  S1.data = {3, 4};
+  EXPECT_THAT(concat<const int>(S0, S1), ElementsAre(1, 2, 3, 4));
+}
+
 template <typename T> struct Iterator {
   int i = 0;
   T operator*() const { return i; }