std::experimental::nonesuch
From cppreference.com
< cpp | experimental
C++
Feature test macros (C++20)
Concepts library (C++20)
Metaprogramming library (C++11)
Ranges library (C++20)
Filesystem library (C++17)
Concurrency support library (C++11)
Execution control library (C++26)
Experimental
Filesystem library (filesystem TS)
Library fundamentals (library fundamentals TS)
Library fundamentals 2 (library fundamentals TS v2)
Library fundamentals 3 (library fundamentals TS v3)
Extensions for parallelism (parallelism TS)
Extensions for parallelism 2 (parallelism TS v2)
Extensions for concurrency (concurrency TS)
Extensions for concurrency 2 (concurrency TS v2)
Concepts (concepts TS)
Ranges (ranges TS)
Reflection (reflection TS)
Mathematical special functions (special functions TR)
Defined in header
<experimental/type_traits>
struct nonesuch {
(library fundamentals TS v2)
~nonesuch() = delete;
nonesuch(nonesuch const&) = delete;
void operator=(nonesuch const&) = delete;
std::experimental::nonesuch
is a class type used by std::experimental::detected_t to indicate detection failure.
nonesuch
has no default constructor or initializer-list constructor, and is not an aggregate.
[edit] Notes
nonesuch
cannot be constructed, destroyed, or copied.
[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR | Applied to | Behavior as published | Correct behavior |
---|---|---|---|
LWG 2960 | LFTSv2 | nonesuch may be an aggregate and has an implicit conversion sequence from {}
|
made non-aggregate and removed ICS |