Fix compilation error for ranges with ADL begin/end (#2807)

* Use `range_begin`/`end` to get formatted range iterators

* Add test for adl `begin`/`end`

* Apply clang-format

* Simplify tests

include/fmt/ranges.h

@@ -402,8 +402,8 @@ struct formatter<
     auto out = ctx.out();
     *out++ = prefix;
     int i = 0;
-    auto it = std::begin(range);
-    auto end = std::end(range);
+    auto it = detail::range_begin(range);
+    auto end = detail::range_end(range);
     for (; it != end; ++it) {
       if (i > 0) out = detail::write_delimiter(out);
       if (custom_specs_) {

test/ranges-test.cc

@@ -65,6 +65,25 @@ TEST(ranges_test, format_set) {
             "{\"one\", \"two\"}");
 }
 
+namespace adl {
+struct box {
+  int value;
+};
+
+auto begin(const box& b) -> const int* {
+  return &b.value;
+}
+
+auto end(const box& b) -> const int* {
+  return &b.value + 1;
+}
+}  // namespace adl
+
+TEST(ranges_test, format_adl_begin_end) {
+  auto b = adl::box{42};
+  EXPECT_EQ(fmt::format("{}", b), "[42]");
+}
+
 TEST(ranges_test, format_pair) {
   auto p = std::pair<int, float>(42, 1.5f);
   EXPECT_EQ(fmt::format("{}", p), "(42, 1.5)");