commit bad8545eeec2e00dc2edd73318b72ad7b97af20e
author Neil MacIntosh <neilmac@microsoft.com> Sun Sep 27 12:43:44 2015 -0700
committer Neil MacIntosh <neilmac@microsoft.com> Sun Sep 27 12:43:44 2015 -0700
tree 760330fd90e6d70e1bcf8a06c5b9e45f73e81f81
parent 599a354b1c02c2e93693692e2ada02105c105ff9
parent 2b6d90436f3f0b0444efc918203663367e823b65

Merge pull request #70 from kernhanda/kernhanda/not_maybe_null

not_null and maybe_null variants should only work on nullptr-assignable types.

include/gsl.h

diff --git a/include/gsl.h b/include/gsl.h
index 23b62a9..fed3b6c 100644
--- a/include/gsl.h
+++ b/include/gsl.h
@@ -108,6 +108,7 @@
 template<class T>
 class not_null
 {
+    static_assert(std::is_assignable<T&, std::nullptr_t>::value, "T cannot be assigned nullptr.");
 public:
     not_null(T t) : ptr_(t) { ensure_invariant(); }
 
@@ -168,6 +169,7 @@
 template<class T>
 class maybe_null_dbg
 {
+    static_assert(std::is_assignable<T&, std::nullptr_t>::value, "T cannot be assigned nullptr.");
 public:
     maybe_null_dbg() : ptr_(nullptr), tested_(false) {}
 
@@ -243,6 +245,7 @@
 template<class T>
 class maybe_null_ret
 {
+    static_assert(std::is_assignable<T&, std::nullptr_t>::value, "T cannot be assigned nullptr.");
 public:
     maybe_null_ret() : ptr_(nullptr) {}
     maybe_null_ret(std::nullptr_t) : ptr_(nullptr) {}

tests/maybenull_tests.cpp

diff --git a/tests/maybenull_tests.cpp b/tests/maybenull_tests.cpp
index 0a9d891..4b74114 100644
--- a/tests/maybenull_tests.cpp
+++ b/tests/maybenull_tests.cpp
@@ -16,6 +16,7 @@
 
 #include <UnitTest++/UnitTest++.h> 
 #include <gsl.h>
+#include <vector>
 
 using namespace Guide;
 
@@ -27,12 +28,24 @@
 {
     TEST(TestMaybeNull1)
     {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        // Forbid non-nullptr assignable types
+        maybe_null_ret<std::vector<int>> f_ret(std::vector<int>{1});
+        maybe_null_ret<std::vector<int>> f_ret(std::vector<int>{1});
+        maybe_null_ret<int> z_ret(10);
+        maybe_null_dbg<std::vector<int>> y_dbg({1,2});
+        maybe_null_dbg<int> z_dbg(10);
+        maybe_null_dbg<std::vector<int>> y_dbg({1,2});
+#endif
         int n = 5;
         maybe_null_dbg<int *> opt_n(&n);
         int result = 0;
         bool threw = false;
 
         CHECK_THROW(result = *opt_n, fail_fast);
+
+        maybe_null_ret<std::shared_ptr<int>> x_ret(std::make_shared<int>(10)); // shared_ptr<int> is nullptr assignable
+        maybe_null_dbg<std::shared_ptr<int>> x_dbg(std::make_shared<int>(10)); // shared_ptr<int> is nullptr assignable
     }
 
     TEST(TestMaybeNull2)

tests/notnull_tests.cpp

diff --git a/tests/notnull_tests.cpp b/tests/notnull_tests.cpp
index 008cbb3..7232840 100644
--- a/tests/notnull_tests.cpp
+++ b/tests/notnull_tests.cpp
@@ -16,6 +16,7 @@
 
 #include <UnitTest++/UnitTest++.h> 
 #include <gsl.h>
+#include <vector>
 
 using namespace Guide;
 
@@ -48,11 +49,18 @@
         not_null<int*> p; // yay...does not compile!
         std::unique_ptr<int> up = std::make_unique<int>(120);
         not_null<int*> p = up;
+
+        // Forbid non-nullptr assignable types
+        not_null<std::vector<int>> f(std::vector<int>{1});
+        not_null<int> z(10);
+        not_null<std::vector<int>> y({1,2});
 #endif
       int i = 12; 
       auto rp = RefCounted<int>(&i);
       not_null<int*> p(rp);
       CHECK(p.get() == &i);
+
+      not_null<std::shared_ptr<int>> x(std::make_shared<int>(10)); // shared_ptr<int> is nullptr assignable
     }
 
     TEST(TestNotNullCasting)