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369c648399
This attribute applies to a using declaration, and permits importing a declaration without knowing if that declaration exists. This is useful for libc++ C wrapper headers that re-export declarations in std::, in cases where the base C library doesn't provide all declarations. This attribute was proposed in http://lists.llvm.org/pipermail/cfe-dev/2020-June/066038.html. rdar://69313357 Differential Revision: https://reviews.llvm.org/D90188
28 lines
1.2 KiB
C++
28 lines
1.2 KiB
C++
// RUN: %clang_cc1 -std=c++20 -fsyntax-only %s -pedantic -verify
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#define UIE __attribute__((using_if_exists))
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namespace NS {
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typedef int x;
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}
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using NS::x __attribute__((using_if_exists));
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using NS::x [[clang::using_if_exists]]; // expected-warning{{ISO C++ does not allow an attribute list to appear here}}
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[[clang::using_if_exists]] // expected-warning{{ISO C++ does not allow an attribute list to appear here}}
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using NS::not_there,
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NS::not_there2;
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using NS::not_there3, // expected-error {{no member named 'not_there3' in namespace 'NS'}}
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NS::not_there4 [[clang::using_if_exists]]; // expected-warning{{C++ does not allow an attribute list to appear here}}
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[[clang::using_if_exists]] using NS::not_there5 [[clang::using_if_exists]]; // expected-warning 2 {{ISO C++ does not allow}}
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struct Base {};
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struct Derived : Base {
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[[clang::using_if_exists]] using Base::x; // expected-warning {{ISO C++ does not allow an attribute list to appear here}}
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using Base::y [[clang::using_if_exists]]; // expected-warning {{ISO C++ does not allow an attribute list to appear here}}
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[[clang::using_if_exists]] using Base::z, Base::q; // expected-warning {{C++ does not allow an attribute list to appear here}}
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};
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