[GNATS 24679] Spurious diagnostic for is_constructible expected an expression.

[jhsedg]

Customer bug ID

type_traits/test/has_nothrow_copy_test.cpp, gnats/24679.C

Description

​This is a reduced test case:
​template <class T, T val> struct integral_constant {
​ static const bool value = val;
​};
​struct is_constructible_imp {
​ template <typename T, typename, typename = decltype(new T())>
​ static char test1(int);
​};
​template <class...> struct is_constructible;
​template <class T, class Arg>
​struct is_constructible<T, Arg>
​ : integral_constant<bool, integral_constant<bool, 0>::value &&
​ (is_constructible_imp::test1<T, Arg>(0))> {};
​template struct is_copy_constructible : is_constructible<T, T> {};
​template
​struct has_nothrow_copy_constructor
​ : integral_constant<bool, is_copy_constructible::value> {};
​has_nothrow_copy_constructor<int[]> value;
​
​fe_only -DTEST_NUMBER=1 --c++20 --gnu_version 110100 -tused -w Test_name.c
​"Test_name.c", line 14: error: expected an expression
​ (is_constructible_imp::test1<T, Arg>(0))> {};
​ ^
​ detected during:
​ instantiation of class "is_constructible<T, Arg> [with T=int [],
​ Arg=int []]" at line 15
​ instantiation of class "is_copy_constructible [with T=int []]"
​ at line 18
​ instantiation of class "has_nothrow_copy_constructor [with T=int
​ []]" at line 19
​
​"Test_name.c", line 14: error: expected a ")"
​ (is_constructible_imp::test1<T, Arg>(0))> {};
​ ^
​ detected during:
​ instantiation of class "is_constructible<T, Arg> [with T=int [],
​ Arg=int []]" at line 15
​ instantiation of class "is_copy_constructible [with T=int []]"
​ at line 18
​ instantiation of class "has_nothrow_copy_constructor [with T=int
​ []]" at line 19
​
​"Test_name.c", line 14: error: expected a ">"
​ (is_constructible_imp::test1<T, Arg>(0))> {};
​ ^
​ detected during:
​ instantiation of class "is_constructible<T, Arg> [with T=int [],
​ Arg=int []]" at line 15
​ instantiation of class "is_copy_constructible [with T=int []]"
​ at line 18
​ instantiation of class "has_nothrow_copy_constructor [with T=int
​ []]" at line 19
​
​"Test_name.c", line 18: error: class "is_copy_constructible<int []>" has no
​ member "value"
​ : integral_constant<bool, is_copy_constructible::value> {};
​ ^
​ detected during instantiation of class
​ "has_nothrow_copy_constructor [with T=int []]" at line
​ 19
​
​4 errors detected in the compilation of "Test_name.c".
​24679.C:fp::FAIL--NO PREVIOUS OUTPUT: