Add null violation checks for std::unique_ptr, std::shared_ptr, `…

…std::optional` and `std::expected` to prevent UB (hsutter#945)

* `assert_not_null` now verifies std::unique_ptr, std::shared_ptr, std::optional and std::expected in addition to the original null pointer check

These states are considered to be "null" and will result in a violation error:

- std::unique_ptr that owns nothing
- std::shared_ptr with no managed object
- std::optional with no value
- std::expected containing an unexpected value

* Update test-results for clang & gcc

* Update some more clang & gcc test results

include/cpp2util.h

@@ -240,6 +240,9 @@
     #ifndef CPP2_NO_EXCEPTIONS
         #include <exception>
     #endif
+    #ifdef __cpp_lib_expected
+        #include <expected>
+    #endif
     #if defined(__cpp_lib_format) || (defined(_MSC_VER) && _MSC_VER >= 1929)
         #include <format>
     #endif
@@ -451,19 +454,67 @@ auto inline Testing = contract_group(
 );
 
 
-//  Null pointer deref checking
+//  Check for invalid dereference or indirection which would result in undefined behavior.
+// 
+//     - Null pointer
+//     - std::unique_ptr that owns nothing
+//     - std::shared_ptr with no managed object
+//     - std::optional with no value
+//     - std::expected containing an unexpected value
+// 
+//  Note: For naming simplicity we consider all the above cases to be "null" states so that
+//        we can write: `*assert_not_null(object)`.
 //
-auto assert_not_null(auto&& p CPP2_SOURCE_LOCATION_PARAM_WITH_DEFAULT) -> decltype(auto)
+template<typename T>
+concept UniquePtr = std::is_same_v<T, std::unique_ptr<typename T::element_type, typename T::deleter_type>>;
+
+template<typename T>
+concept SharedPtr = std::is_same_v<T, std::shared_ptr<typename T::element_type>>;
+
+template<typename T>
+concept Optional = std::is_same_v<T, std::optional<typename T::value_type>>;
+
+#ifdef __cpp_lib_expected
+
+template<typename T>
+concept Expected = std::is_same_v<T, std::expected<typename T::value_type, typename T::error_type>>;
+
+#endif
+
+auto assert_not_null(auto&& arg CPP2_SOURCE_LOCATION_PARAM_WITH_DEFAULT) -> decltype(auto)
 {
     //  NOTE: This "!= T{}" test may or may not work for STL iterators. The standard
     //        doesn't guarantee that using == and != will reliably report whether an
     //        STL iterator has the default-constructed value. So use it only for raw *...
-    if constexpr (std::is_pointer_v<CPP2_TYPEOF(p)>) {
-        if (p == CPP2_TYPEOF(p){}) {
+    if constexpr (std::is_pointer_v<CPP2_TYPEOF(arg)>) {
+        if (arg == CPP2_TYPEOF(arg){}) {
             Null.report_violation("dynamic null dereference attempt detected" CPP2_SOURCE_LOCATION_ARG);
         };
     }
-    return CPP2_FORWARD(p);
+    else if constexpr (UniquePtr<CPP2_TYPEOF(arg)>) {
+        if (!arg) {
+            Null.report_violation("std::unique_ptr is empty" CPP2_SOURCE_LOCATION_ARG);
+        }
+    }
+    else if constexpr (SharedPtr<CPP2_TYPEOF(arg)>) {
+        if (!arg) {
+            Null.report_violation("std::shared_ptr is empty" CPP2_SOURCE_LOCATION_ARG);
+        }
+    }
+    else if constexpr (Optional<CPP2_TYPEOF(arg)>) {
+        if (!arg.has_value()) {
+            Null.report_violation("std::optional does not contain a value" CPP2_SOURCE_LOCATION_ARG);
+        }
+    }
+#ifdef __cpp_lib_expected
+    else if constexpr (Expected<CPP2_TYPEOF(arg)>) {
+        if (!arg.has_value()) {
+            Null.report_violation("std::expected has an unexpected value" CPP2_SOURCE_LOCATION_ARG);
+        }
+    }
+#endif
+
+    return CPP2_FORWARD(arg);
 }
 
 //  Subscript bounds checking

regression-tests/pure2-assert-expected-not-null.cpp2

@@ -0,0 +1,21 @@
+
+fine: () -> int =
+{
+    up:= unique.new<int>(1);
+    sp:= shared.new<int>(2);
+    op: std::optional<int> = (3);
+    ex: std::expected<int, bool> = (4);
+
+    return up* + sp* + op* + ex*;
+}
+
+bad_expected_access: () -> int =
+{
+    ex: std::expected<int, bool> = std::unexpected(false);
+    return ex*;
+}
+
+main: () -> int =
+{
+    return fine() + bad_expected_access();
+}

regression-tests/pure2-assert-optional-not-null.cpp2

@@ -0,0 +1,20 @@
+
+fine: () -> int =
+{
+    up:= unique.new<int>(1);
+    sp:= shared.new<int>(2);
+    op: std::optional<int> = (3);
+
+    return up* + sp* + op*;
+}
+
+bad_optional_access: () -> int =
+{
+    op: std::optional<int> = std::nullopt;
+    return op*;
+}
+
+main: () -> int =
+{
+    return fine() + bad_optional_access();
+}

regression-tests/pure2-assert-shared-ptr-not-null.cpp2

@@ -0,0 +1,21 @@
+
+fine: () -> int =
+{
+    up:= unique.new<int>(1);
+    sp:= shared.new<int>(2);
+    op: std::optional<int> = (3);
+
+    return up* + sp* + op*;
+}
+
+bad_shared_ptr_access: () -> int =
+{
+    sp:= std::make_shared<int>(1);
+    sp.reset();
+    return sp*;
+}
+
+main: () -> int =
+{
+    return fine() + bad_shared_ptr_access();
+}

regression-tests/pure2-assert-unique-ptr-not-null.cpp2

@@ -0,0 +1,21 @@
+
+fine: () -> int =
+{
+    up:= unique.new<int>(1);
+    sp:= shared.new<int>(2);
+    op: std::optional<int> = (3);
+
+    return up* + sp* + op*;
+}
+
+bad_unique_ptr_access: () -> int =
+{
+    up:= std::make_unique<int>(1);
+    up.reset();
+    return up*;
+}
+
+main: () -> int =
+{
+    return fine() + bad_unique_ptr_access();
+}

regression-tests/test-results/apple-clang-14/pure2-assert-expected-not-null.cpp.output

@@ -0,0 +1,19 @@
+pure2-assert-expected-not-null.cpp2:7:10: error: no member named 'expected' in namespace 'std'
+    std::expected<int,bool> ex {4}; 
+    ~~~~~^
+pure2-assert-expected-not-null.cpp2:7:22: error: expected '(' for function-style cast or type construction
+    std::expected<int,bool> ex {4}; 
+                  ~~~^
+pure2-assert-expected-not-null.cpp2:9:165: error: use of undeclared identifier 'ex'
+    return *cpp2::assert_not_null(std::move(up)) + *cpp2::assert_not_null(std::move(sp)) + *cpp2::assert_not_null(std::move(op)) + *cpp2::assert_not_null(std::move(ex)); 
+                                                                                                                                                                    ^
+pure2-assert-expected-not-null.cpp2:14:10: error: no member named 'expected' in namespace 'std'
+    std::expected<int,bool> ex {std::unexpected(false)}; 
+    ~~~~~^
+pure2-assert-expected-not-null.cpp2:14:22: error: expected '(' for function-style cast or type construction
+    std::expected<int,bool> ex {std::unexpected(false)}; 
+                  ~~~^
+pure2-assert-expected-not-null.cpp2:15:45: error: use of undeclared identifier 'ex'
+    return *cpp2::assert_not_null(std::move(ex)); 
+                                            ^
+6 errors generated.

regression-tests/test-results/apple-clang-14/pure2-assert-optional-not-null.cpp.execution

@@ -0,0 +1,2 @@
+Null safety violation: std::optional does not contain a value
+libc++abi: terminating

regression-tests/test-results/apple-clang-14/pure2-assert-shared-ptr-not-null.cpp.execution

@@ -0,0 +1,2 @@
+Null safety violation: std::shared_ptr is empty
+libc++abi: terminating

regression-tests/test-results/apple-clang-14/pure2-assert-unique-ptr-not-null.cpp.execution

@@ -0,0 +1,2 @@
+Null safety violation: std::unique_ptr is empty
+libc++abi: terminating

regression-tests/test-results/clang-12/mixed-bugfix-for-ufcs-non-local.cpp.output

@@ -1,118 +1,118 @@
 mixed-bugfix-for-ufcs-non-local.cpp2:13:12: error: a lambda expression cannot appear in this context
 template<t<CPP2_UFCS_NONLOCAL(f)(o)> UnnamedTypeParam1_1> bool inline constexpr v0 = false;// Fails on GCC ([GCC109781][]) and Clang 12 (a lambda expression cannot appear in this context)
            ^
-../../../include/cpp2util.h:885:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
+../../../include/cpp2util.h:936:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
 #define CPP2_UFCS_NONLOCAL(...)                           CPP2_UFCS_(,(),,__VA_ARGS__)
                                                           ^
-../../../include/cpp2util.h:866:53: note: expanded from macro 'CPP2_UFCS_'
+../../../include/cpp2util.h:917:53: note: expanded from macro 'CPP2_UFCS_'
 #define CPP2_UFCS_(LAMBDADEFCAPT,QUALID,TEMPKW,...) \
                                                     ^
 mixed-bugfix-for-ufcs-non-local.cpp2:15:3: error: a lambda expression cannot appear in this context
 t<CPP2_UFCS_NONLOCAL(f)(o)> inline constexpr v1 = t<true>();// Fails on Clang 12 (lambda in unevaluated context).
   ^
-../../../include/cpp2util.h:885:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
+../../../include/cpp2util.h:936:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
 #define CPP2_UFCS_NONLOCAL(...)                           CPP2_UFCS_(,(),,__VA_ARGS__)
                                                           ^
-../../../include/cpp2util.h:866:53: note: expanded from macro 'CPP2_UFCS_'
+../../../include/cpp2util.h:917:53: note: expanded from macro 'CPP2_UFCS_'
 #define CPP2_UFCS_(LAMBDADEFCAPT,QUALID,TEMPKW,...) \
                                                     ^
 mixed-bugfix-for-ufcs-non-local.cpp2:21:12: error: a lambda expression cannot appear in this context
 template<t<CPP2_UFCS_NONLOCAL(f)(o)> UnnamedTypeParam1_2> auto g() -> void;
            ^
-../../../include/cpp2util.h:885:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
+../../../include/cpp2util.h:936:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
 #define CPP2_UFCS_NONLOCAL(...)                           CPP2_UFCS_(,(),,__VA_ARGS__)
                                                           ^
-../../../include/cpp2util.h:866:53: note: expanded from macro 'CPP2_UFCS_'
+../../../include/cpp2util.h:917:53: note: expanded from macro 'CPP2_UFCS_'
 #define CPP2_UFCS_(LAMBDADEFCAPT,QUALID,TEMPKW,...) \
                                                     ^
 mixed-bugfix-for-ufcs-non-local.cpp2:23:36: error: a lambda expression cannot appear in this context
 auto g([[maybe_unused]] cpp2::in<t<CPP2_UFCS_NONLOCAL(f)(o)>> unnamed_param_1) -> void;
                                    ^
-../../../include/cpp2util.h:885:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
+../../../include/cpp2util.h:936:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
 #define CPP2_UFCS_NONLOCAL(...)                           CPP2_UFCS_(,(),,__VA_ARGS__)
                                                           ^
-../../../include/cpp2util.h:866:53: note: expanded from macro 'CPP2_UFCS_'
+../../../include/cpp2util.h:917:53: note: expanded from macro 'CPP2_UFCS_'
 #define CPP2_UFCS_(LAMBDADEFCAPT,QUALID,TEMPKW,...) \
                                                     ^
 mixed-bugfix-for-ufcs-non-local.cpp2:27:29: error: a lambda expression cannot appear in this context
 [[nodiscard]] auto h() -> t<CPP2_UFCS_NONLOCAL(f)(o)>;
                             ^
-../../../include/cpp2util.h:885:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
+../../../include/cpp2util.h:936:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
 #define CPP2_UFCS_NONLOCAL(...)                           CPP2_UFCS_(,(),,__VA_ARGS__)
                                                           ^
-../../../include/cpp2util.h:866:53: note: expanded from macro 'CPP2_UFCS_'
+../../../include/cpp2util.h:917:53: note: expanded from macro 'CPP2_UFCS_'
 #define CPP2_UFCS_(LAMBDADEFCAPT,QUALID,TEMPKW,...) \
                                                     ^
 mixed-bugfix-for-ufcs-non-local.cpp2:31:12: error: a lambda expression cannot appear in this context
 template<t<CPP2_UFCS_NONLOCAL(f)(o)> UnnamedTypeParam1_3> using a = bool;// Fails on GCC ([GCC109781][]) and Clang 12 (a lambda expression cannot appear in this context)
            ^
-../../../include/cpp2util.h:885:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
+../../../include/cpp2util.h:936:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
 #define CPP2_UFCS_NONLOCAL(...)                           CPP2_UFCS_(,(),,__VA_ARGS__)
                                                           ^
-../../../include/cpp2util.h:866:53: note: expanded from macro 'CPP2_UFCS_'
+../../../include/cpp2util.h:917:53: note: expanded from macro 'CPP2_UFCS_'
 #define CPP2_UFCS_(LAMBDADEFCAPT,QUALID,TEMPKW,...) \
                                                     ^
 mixed-bugfix-for-ufcs-non-local.cpp2:33:12: error: a lambda expression cannot appear in this context
 template<t<CPP2_UFCS_NONLOCAL(f)(o)> UnnamedTypeParam1_4> auto inline constexpr b = false;// Fails on GCC ([GCC109781][]).
            ^
-../../../include/cpp2util.h:885:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
+../../../include/cpp2util.h:936:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
 #define CPP2_UFCS_NONLOCAL(...)                           CPP2_UFCS_(,(),,__VA_ARGS__)
                                                           ^
-../../../include/cpp2util.h:866:53: note: expanded from macro 'CPP2_UFCS_'
+../../../include/cpp2util.h:917:53: note: expanded from macro 'CPP2_UFCS_'
 #define CPP2_UFCS_(LAMBDADEFCAPT,QUALID,TEMPKW,...) \
                                                     ^
 mixed-bugfix-for-ufcs-non-local.cpp2:35:13: error: a lambda expression cannot appear in this context
 using c = t<CPP2_UFCS_NONLOCAL(f)(o)>;// Fails on Clang 12 (lambda in unevaluated context) and Clang 12 (a lambda expression cannot appear in this context)
             ^
-../../../include/cpp2util.h:885:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
+../../../include/cpp2util.h:936:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
 #define CPP2_UFCS_NONLOCAL(...)                           CPP2_UFCS_(,(),,__VA_ARGS__)
                                                           ^
-../../../include/cpp2util.h:866:53: note: expanded from macro 'CPP2_UFCS_'
+../../../include/cpp2util.h:917:53: note: expanded from macro 'CPP2_UFCS_'
 #define CPP2_UFCS_(LAMBDADEFCAPT,QUALID,TEMPKW,...) \
                                                     ^
 mixed-bugfix-for-ufcs-non-local.cpp2:37:29: error: a lambda expression cannot appear in this context
 auto inline constexpr d = t<CPP2_UFCS_NONLOCAL(f)(o)>();// Fails on Clang 12 (lambda in unevaluated context).
                             ^
-../../../include/cpp2util.h:885:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
+../../../include/cpp2util.h:936:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
 #define CPP2_UFCS_NONLOCAL(...)                           CPP2_UFCS_(,(),,__VA_ARGS__)
                                                           ^
-../../../include/cpp2util.h:866:53: note: expanded from macro 'CPP2_UFCS_'
+../../../include/cpp2util.h:917:53: note: expanded from macro 'CPP2_UFCS_'
 #define CPP2_UFCS_(LAMBDADEFCAPT,QUALID,TEMPKW,...) \
                                                     ^
 mixed-bugfix-for-ufcs-non-local.cpp2:21:12: error: a lambda expression cannot appear in this context
 template<t<CPP2_UFCS_NONLOCAL(f)(o)> UnnamedTypeParam1_2> auto g() -> void{}// Fails on GCC ([GCC109781][]) and Clang 12 (a lambda expression cannot appear in this context)
            ^
-../../../include/cpp2util.h:885:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
+../../../include/cpp2util.h:936:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
 #define CPP2_UFCS_NONLOCAL(...)                           CPP2_UFCS_(,(),,__VA_ARGS__)
                                                           ^
-../../../include/cpp2util.h:866:53: note: expanded from macro 'CPP2_UFCS_'
+../../../include/cpp2util.h:917:53: note: expanded from macro 'CPP2_UFCS_'
 #define CPP2_UFCS_(LAMBDADEFCAPT,QUALID,TEMPKW,...) \
                                                     ^
 mixed-bugfix-for-ufcs-non-local.cpp2:23:36: error: a lambda expression cannot appear in this context
 auto g([[maybe_unused]] cpp2::in<t<CPP2_UFCS_NONLOCAL(f)(o)>> unnamed_param_1) -> void{}// Fails on Clang 12 (lambda in unevaluated context).
                                    ^
-../../../include/cpp2util.h:885:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
+../../../include/cpp2util.h:936:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
 #define CPP2_UFCS_NONLOCAL(...)                           CPP2_UFCS_(,(),,__VA_ARGS__)
                                                           ^
-../../../include/cpp2util.h:866:53: note: expanded from macro 'CPP2_UFCS_'
+../../../include/cpp2util.h:917:53: note: expanded from macro 'CPP2_UFCS_'
 #define CPP2_UFCS_(LAMBDADEFCAPT,QUALID,TEMPKW,...) \
                                                     ^
 mixed-bugfix-for-ufcs-non-local.cpp2:27:29: error: a lambda expression cannot appear in this context
 [[nodiscard]] auto h() -> t<CPP2_UFCS_NONLOCAL(f)(o)> { return o;  }// Fails on Clang 12 (lambda in unevaluated context).
                             ^
-../../../include/cpp2util.h:885:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
+../../../include/cpp2util.h:936:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
 #define CPP2_UFCS_NONLOCAL(...)                           CPP2_UFCS_(,(),,__VA_ARGS__)
                                                           ^
-../../../include/cpp2util.h:866:53: note: expanded from macro 'CPP2_UFCS_'
+../../../include/cpp2util.h:917:53: note: expanded from macro 'CPP2_UFCS_'
 #define CPP2_UFCS_(LAMBDADEFCAPT,QUALID,TEMPKW,...) \
                                                     ^
 mixed-bugfix-for-ufcs-non-local.cpp2:41:79: error: lambda expression in an unevaluated operand
   inline CPP2_CONSTEXPR bool u::c = [](cpp2::in<std::type_identity_t<decltype(CPP2_UFCS_NONLOCAL(f)(o))>> x) mutable -> auto { return x; }(true);// Fails on Clang 12 (lambda in unevaluated context).
                                                                               ^
-../../../include/cpp2util.h:885:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
+../../../include/cpp2util.h:936:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
 #define CPP2_UFCS_NONLOCAL(...)                           CPP2_UFCS_(,(),,__VA_ARGS__)
                                                           ^
-../../../include/cpp2util.h:866:53: note: expanded from macro 'CPP2_UFCS_'
+../../../include/cpp2util.h:917:53: note: expanded from macro 'CPP2_UFCS_'
 #define CPP2_UFCS_(LAMBDADEFCAPT,QUALID,TEMPKW,...) \
                                                     ^
 13 errors generated.

regression-tests/test-results/clang-12/pure2-assert-expected-not-null.cpp.output

@@ -0,0 +1,27 @@
+pure2-assert-expected-not-null.cpp2:7:22: error: expected '(' for function-style cast or type construction
+    std::expected<int,bool> ex {4}; 
+                  ~~~^
+pure2-assert-expected-not-null.cpp2:7:10: error: no member named 'expected' in namespace 'std'; did you mean 'unexpected'?
+    std::expected<int,bool> ex {4}; 
+    ~~~~~^~~~~~~~
+         unexpected
+/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/exception:92:8: note: 'unexpected' declared here
+  void unexpected() __attribute__ ((__noreturn__));
+       ^
+pure2-assert-expected-not-null.cpp2:9:165: error: use of undeclared identifier 'ex'
+    return *cpp2::assert_not_null(std::move(up)) + *cpp2::assert_not_null(std::move(sp)) + *cpp2::assert_not_null(std::move(op)) + *cpp2::assert_not_null(std::move(ex)); 
+                                                                                                                                                                    ^
+pure2-assert-expected-not-null.cpp2:14:22: error: expected '(' for function-style cast or type construction
+    std::expected<int,bool> ex {std::unexpected(false)}; 
+                  ~~~^
+pure2-assert-expected-not-null.cpp2:14:10: error: no member named 'expected' in namespace 'std'; did you mean 'unexpected'?
+    std::expected<int,bool> ex {std::unexpected(false)}; 
+    ~~~~~^~~~~~~~
+         unexpected
+/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/exception:92:8: note: 'unexpected' declared here
+  void unexpected() __attribute__ ((__noreturn__));
+       ^
+pure2-assert-expected-not-null.cpp2:15:45: error: use of undeclared identifier 'ex'
+    return *cpp2::assert_not_null(std::move(ex)); 
+                                            ^
+6 errors generated.

regression-tests/test-results/clang-12/pure2-assert-optional-not-null.cpp.execution

@@ -0,0 +1,2 @@
+Null safety violation: std::optional does not contain a value
+terminate called without an active exception

regression-tests/test-results/clang-12/pure2-assert-shared-ptr-not-null.cpp.execution

@@ -0,0 +1,2 @@
+Null safety violation: std::shared_ptr is empty
+terminate called without an active exception

regression-tests/test-results/clang-12/pure2-assert-unique-ptr-not-null.cpp.execution

@@ -0,0 +1,2 @@
+Null safety violation: std::unique_ptr is empty
+terminate called without an active exception

regression-tests/test-results/clang-12/pure2-bugfix-for-ufcs-noexcept.cpp.output

@@ -1,10 +1,10 @@
 pure2-bugfix-for-ufcs-noexcept.cpp2:5:26: error: lambda expression in an unevaluated operand
   static_assert(noexcept(CPP2_UFCS(swap)(t(), t())));// Fails on Clang 12 (lambda in unevaluated context) and GCC 10 (static assertion failed)
                          ^
-../../../include/cpp2util.h:882:59: note: expanded from macro 'CPP2_UFCS'
+../../../include/cpp2util.h:933:59: note: expanded from macro 'CPP2_UFCS'
 #define CPP2_UFCS(...)                                    CPP2_UFCS_(&,(),,__VA_ARGS__)
                                                           ^
-../../../include/cpp2util.h:866:53: note: expanded from macro 'CPP2_UFCS_'
+../../../include/cpp2util.h:917:53: note: expanded from macro 'CPP2_UFCS_'
 #define CPP2_UFCS_(LAMBDADEFCAPT,QUALID,TEMPKW,...) \
                                                     ^
 1 error generated.