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[Sema] Restructure and extend the testing of template pack deduction #79881

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Jan 30, 2024
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[Sema] Restructure and extend the testing of template pack deduction #79881

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51 changes: 28 additions & 23 deletions clang/test/SemaTemplate/deduction.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -414,6 +414,34 @@ namespace deduction_substitution_failure {
int bi = B<char, char>; // expected-note {{during template argument deduction for variable template partial specialization 'B<T, typename Fail<T>::error>' [with T = char]}}
}

namespace deduce_pack_from_argument {
template <typename... T>
void separator(args_tag<T...>, T..., int, T...) {}
template <typename... T>
void separator_dependent(args_tag<T...>, type_identity_t<T>..., int, type_identity_t<T>...) {}
template <typename... Y, typename... T>
void separator_multiple_parameters(args_tag<Y...>, args_tag<T...>, type_identity_t<T>..., int mid, type_identity_t<T>...) {}

void test_separator() {
separator(args_tag<int, int>{}, 4, 8, 42, 16, 25);
separator(args_tag<>{}, 42);
separator_dependent(args_tag<int, int>{}, 4, 8, 42, 16, 25);
separator_dependent(args_tag<>{}, 42);
separator_multiple_parameters(args_tag<const int, const int>{}, args_tag<int, int>{}, 8, 9, 15, 16, 23);
}

template <typename... Y, typename... T> void no_separator(args_tag<T...>, T..., T...) {}
template <typename... Y, typename... T>
void no_separator_dependent(args_tag<Y...>, args_tag<T...>, type_identity_t<T>..., type_identity_t<T>...) {}

void test_no_separator() {
no_separator(args_tag<int, int>{}, 1, 2, 3, 4);
no_separator(args_tag<>{});
no_separator_dependent(args_tag<const int, const int>{}, args_tag<int, int>{}, 8, 9, 15, 16);
no_separator_dependent(args_tag<>{}, args_tag<>{});
}
}

namespace deduction_after_explicit_pack {
template<typename ...T, typename U> int *f(T ...t, int &r, U *u) {
return u;
Expand Down Expand Up @@ -442,29 +470,6 @@ namespace deduction_after_explicit_pack {
i<int, int>(0, 1, 2, 3, 4, 5); // expected-error {{no match}}
}

template <typename... T>
void bar(args_tag<T...>, type_identity_t<T>..., int mid, type_identity_t<T>...) {}
void call_bar() {
bar(args_tag<int, int>{}, 4, 8, 1001, 16, 23);
}

template <typename... Y, typename... T>
void foo(args_tag<Y...>, args_tag<T...>, type_identity_t<T>..., int mid, type_identity_t<T>...) {}
void call_foo() {
foo(args_tag<const int,const int, const int>{}, args_tag<int, int, int>{}, 4, 8, 9, 15, 16, 23, 1);
}

template <typename... Y, typename... T>
void foo2(args_tag<Y...>, args_tag<T...>, type_identity_t<T>..., type_identity_t<T>...) {}
void call_foo2() {
foo2(args_tag<const int,const int, const int>{}, args_tag<int, int, int>{}, 4, 8, 9, 15, 16, 23);
}

template <typename... Y, typename... T> void baz(args_tag<T...>, T..., T...) {}
void call_baz() {
baz(args_tag<int, int>{}, 1, 2, 3, 4);
}

// GCC alarmingly accepts this by deducing T={int} by matching the second
// parameter against the first argument, then passing the first argument
// through the first parameter.
Expand Down