SafeMin/SafeMax: Fix wrong return type when given two enum arguments

webrtc/base/safe_minmax_unittest.cc

 /*
  *  Copyright 2017 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 44 matching lines @@
 static_assert(TypeCheckMinMax< uint8_t, uint64_t,  uint8_t, uint64_t>(), "");
 static_assert(TypeCheckMinMax< int64_t,   int8_t,  int64_t,  int64_t>(), "");
 static_assert(TypeCheckMinMax< int64_t,  uint8_t,  int64_t,  int64_t>(), "");
 static_assert(TypeCheckMinMax< int64_t,  int64_t,  int64_t,  int64_t>(), "");
 static_assert(TypeCheckMinMax< int64_t, uint64_t,  int64_t, uint64_t>(), "");
 static_assert(TypeCheckMinMax<uint64_t,   int8_t,   int8_t, uint64_t>(), "");
 static_assert(TypeCheckMinMax<uint64_t,  uint8_t,  uint8_t, uint64_t>(), "");
 static_assert(TypeCheckMinMax<uint64_t,  int64_t,  int64_t, uint64_t>(), "");
 static_assert(TypeCheckMinMax<uint64_t, uint64_t, uint64_t, uint64_t>(), "");
 
-// SafeMin/SafeMax: Check that we can use enum types.
 enum DefaultE { kFoo = -17 };
 enum UInt8E : uint8_t { kBar = 17 };
-static_assert(TypeCheckMinMax<unsigned, DefaultE,     int, unsigned>(), "");
-static_assert(TypeCheckMinMax<unsigned,   UInt8E, uint8_t, unsigned>(), "");
-static_assert(TypeCheckMinMax<DefaultE,   UInt8E,     int,      int>(), "");
+
+// SafeMin/SafeMax: Check that we can use enum types.
+static_assert(TypeCheckMinMax<unsigned, unsigned, unsigned, unsigned>(), "");
+static_assert(TypeCheckMinMax<unsigned, DefaultE,      int, unsigned>(), "");
+static_assert(TypeCheckMinMax<unsigned,   UInt8E,  uint8_t, unsigned>(), "");
+static_assert(TypeCheckMinMax<DefaultE, unsigned,      int, unsigned>(), "");
+static_assert(TypeCheckMinMax<DefaultE, DefaultE,      int,      int>(), "");
+static_assert(TypeCheckMinMax<DefaultE,   UInt8E,      int,      int>(), "");

[kwiberg-webrtc, 2017/06/02 10:14:03]

This (line 74) is the test that failed without the code change in this CL.

+static_assert(TypeCheckMinMax<  UInt8E, unsigned,  uint8_t, unsigned>(), "");
+static_assert(TypeCheckMinMax<  UInt8E, DefaultE,     int,       int>(), "");
+static_assert(TypeCheckMinMax<  UInt8E,   UInt8E,  uint8_t,  uint8_t>(), "");
 
 using ld = long double;
 
 // SafeMin/SafeMax: Check that all floating-point combinations give the
 // correct result type.
 static_assert(TypeCheckMinMax< float,  float,  float,  float>(), "");
 static_assert(TypeCheckMinMax< float, double, double, double>(), "");
 static_assert(TypeCheckMinMax< float,     ld,     ld,     ld>(), "");
 static_assert(TypeCheckMinMax<double,  float, double, double>(), "");
 static_assert(TypeCheckMinMax<double, double, double, double>(), "");
@@ skipping 51 matching lines @@
 int32_t  TestMinRef(  int32_t a,  int32_t b) { return std::min(a, b); }
 uint32_t TestMinRef( uint32_t a, uint32_t b) { return std::min(a, b); }
 int32_t  TestMinSafe( int32_t a,  int32_t b) { return SafeMin(a, b); }
 int32_t  TestMinSafe( int32_t a, uint32_t b) { return SafeMin(a, b); }
 int32_t  TestMinSafe(uint32_t a,  int32_t b) { return SafeMin(a, b); }
 uint32_t TestMinSafe(uint32_t a, uint32_t b) { return SafeMin(a, b); }
 
 // clang-format on
 
 }  // namespace rtc