From 3b9d15f49fe043d42b2715dc5041f23ed7f56c5c Mon Sep 17 00:00:00 2001
From: "Jordan Maples [MSFT]" <49793787+JordanMaples@users.noreply.github.com>
Date: Wed, 5 Feb 2020 17:02:23 -0800
Subject: [PATCH] reverting changes to gsl::index

---
 include/gsl/gsl_util  | 13 +++++++------
 tests/at_tests.cpp    | 26 +++++++++++++++++---------
 tests/utils_tests.cpp |  2 +-
 3 files changed, 25 insertions(+), 16 deletions(-)

diff --git a/include/gsl/gsl_util b/include/gsl/gsl_util
index 53141e6..d1f7f33 100644
--- a/include/gsl/gsl_util
+++ b/include/gsl/gsl_util
@@ -49,7 +49,7 @@ namespace gsl
 //
 
 // index type for all container indexes/subscripts/sizes
-using index = std::size_t;
+using index = std::ptrdiff_t;
 
 // final_action allows you to ensure something gets run at the end of a scope
 template <class F>
@@ -129,8 +129,8 @@ GSL_SUPPRESS(bounds.4) // NO-FORMAT: attribute
 GSL_SUPPRESS(bounds.2) // NO-FORMAT: attribute
 constexpr T& at(T (&arr)[N], const index i)
 {
-    Expects(i >= 0 && i < N);
-    return arr[i];
+    Expects(i >= 0 && i < narrow_cast<index>(N));
+    return arr[narrow_cast<std::size_t>(i)];
 }
 
 template <class Cont>
@@ -138,15 +138,16 @@ GSL_SUPPRESS(bounds.4) // NO-FORMAT: attribute
 GSL_SUPPRESS(bounds.2) // NO-FORMAT: attribute
 constexpr auto at(Cont& cont, const index i) -> decltype(cont[cont.size()])
 {
-    Expects(i >= 0 && i < cont.size());
-    return cont[i];
+    Expects(i >= 0 && i < narrow_cast<index>(cont.size()));
+    using size_type = decltype(cont.size());
+    return cont[narrow_cast<size_type>(i)];
 }
 
 template <class T>
 GSL_SUPPRESS(bounds.1) // NO-FORMAT: attribute
 constexpr T at(const std::initializer_list<T> cont, const index i)
 {
-    Expects(i >= 0 && i < cont.size());
+    Expects(i >= 0 && i < narrow_cast<index>(cont.size()));
     return *(cont.begin() + i);
 }
 
diff --git a/tests/at_tests.cpp b/tests/at_tests.cpp
index 0580301..be2c7b8 100644
--- a/tests/at_tests.cpp
+++ b/tests/at_tests.cpp
@@ -33,7 +33,7 @@ TEST(at_tests, static_array)
     int a[4] = {1, 2, 3, 4};
     const int(&c_a)[4] = a;
 
-    for (std::size_t i = 0; i < 4; ++i) {
+    for (int i = 0; i < 4; ++i) {
         EXPECT_TRUE(&gsl::at(a, i) == &a[i]);
         EXPECT_TRUE(&gsl::at(c_a, i) == &a[i]);
     }
@@ -43,7 +43,9 @@ TEST(at_tests, static_array)
         std::abort();
     });
 
+    EXPECT_DEATH(gsl::at(a, -1), deathstring);
     EXPECT_DEATH(gsl::at(a, 4), deathstring);
+    EXPECT_DEATH(gsl::at(c_a, -1), deathstring);
     EXPECT_DEATH(gsl::at(c_a, 4), deathstring);
 }
 
@@ -52,7 +54,7 @@ TEST(at_tests, std_array)
     std::array<int, 4> a = {1, 2, 3, 4};
     const std::array<int, 4>& c_a = a;
 
-    for (std::size_t i = 0; i < 4; ++i) {
+    for (int i = 0; i < 4; ++i) {
         EXPECT_TRUE(&gsl::at(a, i) == &a[static_cast<std::size_t>(i)]);
         EXPECT_TRUE(&gsl::at(c_a, i) == &a[static_cast<std::size_t>(i)]);
     }
@@ -62,7 +64,9 @@ TEST(at_tests, std_array)
         std::abort();
     });
 
+    EXPECT_DEATH(gsl::at(a, -1), deathstring);
     EXPECT_DEATH(gsl::at(a, 4), deathstring);
+    EXPECT_DEATH(gsl::at(c_a, -1), deathstring);
     EXPECT_DEATH(gsl::at(c_a, 4), deathstring);
 }
 
@@ -71,7 +75,7 @@ TEST(at_tests, std_vector)
     std::vector<int> a = {1, 2, 3, 4};
     const std::vector<int>& c_a = a;
 
-    for (std::size_t i = 0; i < 4; ++i) {
+    for (int i = 0; i < 4; ++i) {
         EXPECT_TRUE(&gsl::at(a, i) == &a[static_cast<std::size_t>(i)]);
         EXPECT_TRUE(&gsl::at(c_a, i) == &a[static_cast<std::size_t>(i)]);
     }
@@ -81,7 +85,9 @@ TEST(at_tests, std_vector)
         std::abort();
     });
 
+    EXPECT_DEATH(gsl::at(a, -1), deathstring);
     EXPECT_DEATH(gsl::at(a, 4), deathstring);
+    EXPECT_DEATH(gsl::at(c_a, -1), deathstring);
     EXPECT_DEATH(gsl::at(c_a, 4), deathstring);
 }
 
@@ -90,8 +96,8 @@ TEST(at_tests, InitializerList)
     const std::initializer_list<int> a = {1, 2, 3, 4};
 
     for (int i = 0; i < 4; ++i) {
-        EXPECT_TRUE(gsl::at(a, static_cast<std::size_t>(i)) == i + 1);
-        EXPECT_TRUE(gsl::at({1, 2, 3, 4}, static_cast<std::size_t>(i)) == i + 1);
+        EXPECT_TRUE(gsl::at(a, i) == i + 1);
+        EXPECT_TRUE(gsl::at({1, 2, 3, 4}, i) == i + 1);
     }
 
     std::set_terminate([] {
@@ -99,7 +105,9 @@ TEST(at_tests, InitializerList)
         std::abort();
     });
 
+    EXPECT_DEATH(gsl::at(a, -1), deathstring);
     EXPECT_DEATH(gsl::at(a, 4), deathstring);
+    EXPECT_DEATH(gsl::at({1, 2, 3, 4}, -1), deathstring);
     EXPECT_DEATH(gsl::at({1, 2, 3, 4}, 4), deathstring);
 }
 
@@ -112,12 +120,12 @@ static constexpr bool test_constexpr()
     const std::array<int, 4>& c_a2 = a2;
 
     for (int i = 0; i < 4; ++i) {
-        if (&gsl::at(a1, static_cast<std::size_t>(i)) != &a1[i]) return false;
-        if (&gsl::at(c_a1, static_cast<std::size_t>(i)) != &a1[i]) return false;
+        if (&gsl::at(a1, i) != &a1[i]) return false;
+        if (&gsl::at(c_a1, i) != &a1[i]) return false;
         // requires C++17:
         // if (&gsl::at(a2, i) != &a2[static_cast<std::size_t>(i)]) return false;
-        if (&gsl::at(c_a2, static_cast<std::size_t>(i)) != &c_a2[static_cast<std::size_t>(i)]) return false;
-        if (gsl::at({1, 2, 3, 4}, static_cast<std::size_t>(i)) != i + 1) return false;
+        if (&gsl::at(c_a2, i) != &c_a2[static_cast<std::size_t>(i)]) return false;
+        if (gsl::at({1, 2, 3, 4}, i) != i + 1) return false;
     }
 
     return true;
diff --git a/tests/utils_tests.cpp b/tests/utils_tests.cpp
index 78bf59d..1fb0fd2 100644
--- a/tests/utils_tests.cpp
+++ b/tests/utils_tests.cpp
@@ -38,7 +38,7 @@ void g() { j += 1; }
 
 TEST(utils_tests, sanity_check_for_gsl_index_typedef)
 {
-    static_assert(std::is_same<gsl::index, std::size_t>::value,
+    static_assert(std::is_same<gsl::index, std::ptrdiff_t>::value,
                   "gsl::index represents wrong arithmetic type");
 }