Ichthyostega
b8cf274de6
due to switching from ADL extension points to member functions, we now need to detect a "state core" type in a different fashion. The specific twist is that we can not spell out the full signature in all cases, since the result type will be formed as a consequence of this type detection. Thus there are now additional detectors to probe for the presence of a specific function name only, and the distinction between members and member functions has been sharpened.
226 lines
9.3 KiB
C++
226 lines
9.3 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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public:
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double funny (char, char, string);
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void funky() const;
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short fuzzy (float, float);
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long long fuzzy();
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double fully;
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};
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class Fishy
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{
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/** @note private function can never be detected */
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long long fuzzy();
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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 demonstrate some details regarding detection of functions within a type.
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* The purpose of these metaprogramming techniques is to write generic containers,
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* handlers, iterators etc, which automatically adapt themselves to the abilities
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* of their payload type. To give an example, we may investigate the argument type
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* of a functor or lambda, and then compose it with a suitable adapter or converter
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* to work with the given data.
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*
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* However, when it comes to detecting the presence of a specific function, there
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* are some complexities and variations to consider. Sometimes we only want to check
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* for the presence of some function, while in other cases we also want to verify
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* the exact signature of that function. Moreover, some of these detection techniques
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* break down whenever there is overload ambiguity; thus we might need to resort to
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* an alternative, not so strict test to get past such limitations.
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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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META_DETECT_FUNCTION (double, funny, (char, char, string));
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META_DETECT_FUNCTION (long long, fuzzy, (void));
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META_DETECT_FUNCTION_NAME (funny);
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META_DETECT_FUNCTION_NAME (funky);
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META_DETECT_FUNCTION_NAME (fuzzy);
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META_DETECT_FUNCTION_NAME (fully);
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META_DETECT_MEMBER(funny);
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META_DETECT_MEMBER(funky);
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META_DETECT_MEMBER(fuzzy);
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META_DETECT_MEMBER(fully);
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META_DETECT_FUNCTION_ARGLESS (funny);
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META_DETECT_FUNCTION_ARGLESS (funky);
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META_DETECT_FUNCTION_ARGLESS (fuzzy);
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void
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run (Arg)
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{
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detect_freeFunctionADL_ExtensionPoint();
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detect_memberFunctionVariations();
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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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void
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detect_freeFunctionADL_ExtensionPoint()
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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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CHECK ( not HasExtensionPoint_fun<Fishy const&>::value );
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}
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/** @test cover variations of member function detection
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* - detect an explicitly given full signature
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* - detect just the presence of a function _name_
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* - distinguish this from detecting a _member_
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* - detect especially a member function without arguments
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* @note some corner cases are demonstrated here as well:
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* - private functions can not be detected
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* - detection fails on ambiguity due to overloads
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*/
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void
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detect_memberFunctionVariations()
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{
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CHECK ( HasFunSig_funny<Cheesy> ::value ); // explicit function signature detected
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CHECK ( HasFunSig_funny<Cheesy const> ::value ); // const qualifier is irrelevant
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CHECK ( not HasFunSig_funny<Cheesy const&> ::value ); // but reference does not work, obviously
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CHECK ( HasFunSig_fuzzy<Cheesy> ::value ); // explicit function signature detected, overload is irrelevant
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CHECK ( HasFunName_funny<Cheesy> ::value ); // function name detected (arguments irrelevant)
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CHECK ( HasFunName_funky<Cheesy> ::value ); // detected irrespective of const modifier
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CHECK ( not HasFunName_fuzzy<Cheesy> ::value ); // function name fuzzy *not* detected due to overload ambiguity
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CHECK ( not HasFunName_fully<Cheesy> ::value ); // name fully is a member, not a function
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CHECK ( HasMember_funny<Cheesy> ::value ); // 'funny' is not only a function, it is also a member
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CHECK ( HasMember_funky<Cheesy> ::value );
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CHECK ( not HasMember_fuzzy<Cheesy> ::value ); // WARNING: member 'fuzzy' *not* detected due to overload ambiguity
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CHECK ( HasMember_fully<Cheesy> ::value ); // 'fully' is not a function, but it is detected as member here
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CHECK ( not HasArglessFun_funny<Cheesy> ::value ); // there is no argument less function 'funny' (it takes arguments)
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CHECK ( HasArglessFun_funky<Cheesy> ::value ); // but an argument-less 'funky'
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CHECK ( HasArglessFun_fuzzy<Cheesy> ::value ); // and one of the 'fuzzy' overloads also takes no arguments
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CHECK ( not HasFunSig_fuzzy<Fishy> ::value ); // Fishy::fuzzy() is private and can thus never be detected
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CHECK ( not HasFunSig_funny<Fishy> ::value ); // and no fun with Fishy beyond that...
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CHECK ( not HasFunName_funny<Fishy> ::value );
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CHECK ( not HasFunName_funky<Fishy> ::value );
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CHECK ( not HasFunName_fuzzy<Fishy> ::value );
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CHECK ( not HasFunName_fully<Fishy> ::value );
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CHECK ( not HasMember_funny<Fishy> ::value );
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CHECK ( not HasMember_funky<Fishy> ::value );
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CHECK ( not HasMember_fuzzy<Fishy> ::value );
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CHECK ( not HasMember_fully<Fishy> ::value );
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CHECK ( not HasArglessFun_funny<Fishy> ::value );
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CHECK ( not HasArglessFun_funky<Fishy> ::value );
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CHECK ( not HasArglessFun_fuzzy<Fishy> ::value );
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CHECK ( not HasFunSig_fuzzy<short> ::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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