66 lines
1.9 KiB
C++
66 lines
1.9 KiB
C++
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// RUN: %clang_cc1 -std=c++20 -fcxx-exceptions -verify %s
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struct A { int n; };
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template<A a> struct B {
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static constexpr A &v = a; // expected-error {{binding reference of type 'A' to value of type 'const A' drops 'const' qualifier}}
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};
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template<A a> struct C {
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static constexpr const A &v = a;
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};
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// All such template parameters in the program of the same type with the same
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// value denote the same template parameter object.
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template<A a, typename T> void check() {
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static_assert(&a == &T::v); // expected-error {{failed}}
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}
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using T = C<A{1}>;
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template void check<A{1}, T>();
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template void check<A{2}, T>(); // expected-note {{instantiation of}}
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// Different types with the same value are unequal.
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struct A2 { int n; };
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template<A2 a2> struct C2 {
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static constexpr const A2 &v = a2;
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};
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static_assert((void*)&C<A{}>::v != (void*)&C2<A2{}>::v);
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// A template parameter object shall have constant destruction.
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namespace ConstDestruction {
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struct D {
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int n;
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bool can_destroy;
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constexpr ~D() {
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if (!can_destroy)
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throw "oh no"; // expected-note {{subexpression not valid}}
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}
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};
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template<D d>
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void f() {} // expected-note 2{{invalid explicitly-specified argument}}
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void g() {
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f<D{0, true}>();
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f<D{0, false}>(); // expected-error {{no matching function}}
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}
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// We can SFINAE on constant destruction.
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template<typename T> auto h(T t) -> decltype(f<T{1, false}>());
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template<typename T> auto h(T t) -> decltype(f<T{1, true}>());
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void i() {
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h(D());
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// Ensure we don't cache an invalid template argument after we've already
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// seen it in a SFINAE context.
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f<D{1, false}>(); // expected-error {{no matching function}}
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f<D{1, true}>();
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}
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template<D d> struct Z {};
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Z<D{2, true}> z1;
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Z<D{2, false}> z2; // expected-error {{non-type template argument is not a constant expression}} expected-note-re {{in call to '{{.*}}->~D()'}}
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}
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