Don't use auto in some ranges algos. (#4841)

fsb4000 · hewillk · StephanTLavavej · web-flow · commit a537ec5e47a2 · 2024-08-07T23:19:59.000-07:00
Co-authored-by: Hewill Kang &lt;67143766+hewillk@users.noreply.github.com&gt;
Co-authored-by: Stephan T. Lavavej &lt;stl@nuwen.net&gt;
diff --git a/stl/inc/algorithm b/stl/inc/algorithm
@@ -7781,7 +7781,7 @@ namespace ranges {
     void _Rotate_one_right(_It _First, _It _Mid, _It _Last) {
         // exchanges the range [_First, _Mid) with [_Mid, _Last)
         _STL_INTERNAL_CHECK(_RANGES next(_Mid) == _Last);
-        auto _Temp = _RANGES iter_move(_Mid);
+        iter_value_t<_It> _Temp(_RANGES iter_move(_Mid));
         _RANGES _Move_backward_common(_First, _STD move(_Mid), _STD move(_Last));
         *_First = _STD move(_Temp);
     }
@@ -7790,7 +7790,7 @@ namespace ranges {
     void _Rotate_one_left(_It _First, _It _Mid, _It _Last) {
         // exchanges the range [_First, _Mid) with [_Mid, _Last)
         _STL_INTERNAL_CHECK(_RANGES next(_First) == _Mid);
-        auto _Temp   = _RANGES iter_move(_First);
+        iter_value_t<_It> _Temp(_RANGES iter_move(_First));
         auto _Result = _RANGES _Move_unchecked(_STD move(_Mid), _STD move(_Last), _STD move(_First));
         *_Result.out = _STD move(_Temp);
     }
@@ -10286,7 +10286,7 @@ namespace ranges {
                 }
 
                 while (++_UFirst != _ULast) { // process one or two elements
-                    auto _Prev = *_UFirst;
+                    _Vty _Prev(*_UFirst);
                     if (++_UFirst == _ULast) { // process last element
                         if (_STD invoke(_Pred, _STD invoke(_Proj, _Prev), _STD invoke(_Proj, _Found.min))) {
                             _Found.min = _STD move(_Prev);
diff --git a/tests/std/test.lst b/tests/std/test.lst
@@ -236,6 +236,7 @@ tests\GH_003840_tellg_when_reading_lf_file_in_text_mode
 tests\GH_003867_output_nan
 tests\GH_004023_mdspan_fwd_prod_overflow
 tests\GH_004040_container_nonmember_functions
+tests\GH_004108_some_ranges_algos_construct_wrong_type
 tests\GH_004109_iter_value_t_direct_initialization
 tests\GH_004129_conversion_in_new_numeric_algorithms
 tests\GH_004201_chrono_formatter
diff --git a/tests/std/tests/GH_004108_some_ranges_algos_construct_wrong_type/env.lst b/tests/std/tests/GH_004108_some_ranges_algos_construct_wrong_type/env.lst
@@ -0,0 +1,4 @@
+# Copyright (c) Microsoft Corporation.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+RUNALL_INCLUDE ..\usual_20_matrix.lst
diff --git a/tests/std/tests/GH_004108_some_ranges_algos_construct_wrong_type/test.compile.pass.cpp b/tests/std/tests/GH_004108_some_ranges_algos_construct_wrong_type/test.compile.pass.cpp
@@ -0,0 +1,63 @@
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include <algorithm>
+#include <cstddef>
+#include <ranges>
+
+using namespace std;
+
+namespace gh4108 {
+    struct RRef {
+        RRef(RRef&&) = delete;
+    };
+
+    struct Val {
+        Val(const RRef&);
+        auto operator<=>(const Val&) const = default;
+    };
+
+    struct I {
+        using value_type      = Val;
+        using difference_type = ptrdiff_t;
+        Val& operator*() const;
+        I& operator++();
+        I operator++(int);
+        I& operator--();
+        I operator--(int);
+        bool operator==(const I&) const;
+        friend RRef&& iter_move(const I&);
+    };
+
+    // GH-4108 <algorithm>: ranges::inplace_merge accidentally constructed remove_cvref_t<iter_rvalue_reference_t<I>>
+    void test_gh_4108() {
+        ranges::inplace_merge(I{}, I{}, I{});
+    }
+} // namespace gh4108
+
+namespace gh4102 {
+    struct Ref {
+        Ref(const Ref&)                    = delete;
+        auto operator<=>(const Ref&) const = default;
+    };
+
+    struct Val {
+        Val() = default;
+        Val(const Ref&);
+        auto operator<=>(const Val&) const = default;
+    };
+
+    struct I {
+        using value_type      = Val;
+        using difference_type = ptrdiff_t;
+        const Ref& operator*() const;
+        I& operator++();
+        void operator++(int);
+        bool operator==(const I&) const;
+    };
+
+    // GH-4102 <algorithm>: ranges::minmax accidentally constructed remove_cvref_t<iter_reference_t<I>>
+    void test_gh_4102() {
+        [[maybe_unused]] auto result = ranges::minmax(ranges::subrange<I, I>{});
+    }
+} // namespace gh4102
