Ichthyostega
fe3feee67a
such a detector function can be used to enable some template specialisation based on the fact that a target type exposes the desired extension point
129 lines
4 KiB
C++
129 lines
4 KiB
C++
/*
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DuckDetectorExtension(Test) - detecting support for extension points at compile time
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Copyright (C) Lumiera.org
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2017, Hermann Vosseler <Ichthyostega@web.de>
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of
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the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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* *****************************************************/
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/** @file duck-detector-extension-test.cpp
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** unit test \ref DuckDetectorExtension_test
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*/
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#include "lib/test/run.hpp"
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#include "lib/meta/duck-detector.hpp"
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#include "lib/util.hpp"
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#include <string>
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namespace lib {
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namespace meta{
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namespace test{
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using std::string;
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namespace { // test types and definitions to explore....
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void
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fun (long)
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{ }
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int
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fun (string, long)
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{
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return 12;
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}
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void
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fun ()
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{ }
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class Cheesy
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{ };
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class Fishy
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{
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/** @note type Fishy exposes an extension point `fun` */
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friend void fun (Fishy&);
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};
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}//(End) test definitions
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/***********************************************************************************//**
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* @test detect the presence of a free function extension point at compile time.
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* It is a common idiom in C++ to expose an extension point through a free function,
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* which is expected to be picked up by ADL. To mention a prominent example, any type
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* can offer the ability to be _iterated_ by injecting free functions `begin(TY)` and
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* `end(TY)`, to yield a STL compatible iterator.
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*
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* Since such an extension point is used just by invoking the _unqualified_ function
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* with the target type, we can build a meta predicate based on the fact if such an
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* function invocation expression can be formed for the type in question.
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*
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* @note the test really hinges on the ability to form the extension point call.
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* For this reason, some implicit conversions might be involved, and some
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* other conversions won't work (like passing a value to an extension point
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* taking a reference).
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*/
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class DuckDetectorExtension_test : public Test
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{
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META_DETECT_EXTENSION_POINT (funZ);
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META_DETECT_EXTENSION_POINT (fun);
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void
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run (Arg)
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{
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fun ();
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fun (23);
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fun ("FUN", 45);
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CHECK ( not HasExtensionPoint_funZ<long>::value );
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CHECK ( HasExtensionPoint_fun<long> ::value );
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CHECK ( HasExtensionPoint_fun<long&> ::value );
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CHECK ( HasExtensionPoint_fun<long&&> ::value );
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CHECK ( HasExtensionPoint_fun<char> ::value );
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CHECK ( HasExtensionPoint_fun<char&> ::value );
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CHECK ( HasExtensionPoint_fun<char&&> ::value );
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CHECK ( not HasExtensionPoint_fun<string> ::value );
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CHECK ( not HasExtensionPoint_fun<void> ::value );
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CHECK ( not HasExtensionPoint_fun<Cheesy> ::value );
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CHECK ( not HasExtensionPoint_fun<Fishy> ::value );
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CHECK ( HasExtensionPoint_fun<Fishy&> ::value );
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CHECK ( not HasExtensionPoint_fun<Fishy&&> ::value );
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CHECK ( not HasExtensionPoint_fun<Fishy const&>::value );
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}
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};
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/** Register this test class... */
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LAUNCHER (DuckDetectorExtension_test, "unit meta");
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}}} // namespace lib::meta::test
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