Viewing file:  lambda-uneval2.C (1.72 KB) -rw-r--r--
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// { dg-do compile { target c++20 } }
// ill-formed, no diagnostic required: the two expressions are
// functionally equivalent but not equivalent
template <int N> void foo(const char (&s)[([]{}, N)]);
template <int N> void foo(const char (&s)[([]{}, N)]);
// two different declarations because the non-dependent portions are not
// considered equivalent
template <class T> void spam(decltype([]{}) (*s)[sizeof(T)]);
template <class T> void spam(decltype([]{}) (*s)[sizeof(T)]);
template <class T>
using A = decltype([] { });
// A<int> and A<char> refer to different closure types
template <class T>
auto f(T) -> decltype([]() { T::invalid; } ()); // { dg-error "invalid" }
void f(...);
template <class T, unsigned = sizeof([]() { T::invalid; })> // { dg-error "invalid" }
void g(T);
void g(...);
template <class T>
auto h(T) -> decltype([x = T::invalid]() { });
void h(...);
template <class T>
auto i(T) -> decltype([]() -> typename T::invalid { });
void i(...);
template <class T>
auto j(T t) -> decltype([](auto x) -> decltype(x.invalid) { } (t));
void j(...);
template <class,class> struct different {};
template <class T> struct different<T,T> { typename T::invalid t; };
template <class,class> struct same;
template <class T> struct same<T,T> {};
int main()
{
foo<1>(""); // { dg-error "ambiguous" }
spam<char>(nullptr); // { dg-error "ambiguous" }
different<A<int>,A<char>>();
same<A<int>,A<int>>();
f(0); // error: invalid expression not part of the immediate context
g(0); // error: invalid expression not part of the immediate context
h(0); // error: invalid expression not part of the immediate context
i(0); // error: invalid expression not part of the immediate context
j(0); // deduction fails on #1, calls #2
}
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