Features: Add cxx_inline_namespaces.

Help/variable/CMAKE_CXX_KNOWN_FEATURES.rst

@@ -87,6 +87,11 @@ The features known to this version of CMake are:
 
   .. _N2540: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2540.htm
 
+``cxx_inline_namespaces``
+  Inline namespaces, as defined in N2535_.
+
+  .. _N2535: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2535.htm
+
 ``cxx_lambdas``
   Lambda functions, as defined in N2927_.
 

Modules/Compiler/GNU-CXX-FeatureTests.cmake

@@ -41,6 +41,7 @@ set(_cmake_feature_test_cxx_auto_type "${GNU44_CXX11}")
 set(_cmake_feature_test_cxx_defaulted_functions "${GNU44_CXX11}")
 set(_cmake_feature_test_cxx_deleted_functions "${GNU44_CXX11}")
 set(_cmake_feature_test_cxx_generalized_initializers "${GNU44_CXX11}")
+set(_cmake_feature_test_cxx_inline_namespaces "${GNU44_CXX11}")
 set(_cmake_feature_test_cxx_strong_enums "${GNU44_CXX11}")
 set(_cmake_feature_test_cxx_trailing_return_types "${GNU44_CXX11}")
 set(_cmake_feature_test_cxx_unicode_literals "${GNU44_CXX11}")

Source/cmMakefile.cxx

@@ -57,6 +57,7 @@
   F(cxx_final) \
   F(cxx_generalized_initializers) \
   F(cxx_inheriting_constructors) \
+  F(cxx_inline_namespaces) \
   F(cxx_lambdas) \
   F(cxx_noexcept) \
   F(cxx_nonstatic_member_init) \

Tests/CompileFeatures/cxx_inline_namespaces.cpp

@@ -0,0 +1,26 @@
+namespace Lib
+{
+inline namespace Lib_1
+{
+  template <typename T> class A;
+}
+
+template <typename T> void g(T);
+}
+
+struct MyClass {
+
+};
+namespace Lib
+{
+template<>
+class A<MyClass> {
+
+};
+}
+
+void someFunc()
+{
+  Lib::A<MyClass> a;
+  g(a);  // ok, Lib is an associated namespace of A
+}