https://bugs.llvm.org/show_bug.cgi?id=46218
Bug ID: 46218
Summary: Concepts: cannot find matching function when requires
clause contains invalid expression
Product: clang
Version: trunk
Hardware: All
OS: All
Status: NEW
Severity: enhancement
Priority: P
Component: C++2a
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected],
[email protected], [email protected]
Clang cannot find matching function constrained on a concept when its requires
clause has invalid expression but would otherwise evaluate to true. Code
compiles correctly with MSVC 19.27.28826.0 and GCC 10.1 but not Clang 10.
>From https://en.cppreference.com/w/cpp/language/constraints:
The substitution of template arguments into a requires-expression used in a
declaration of a templated entity may result in the formation of invalid types
or expressions in its requirements, or the violation of semantic constraints of
those requirements. In such cases, the requires-expression evaluates to false
and does not cause the program to be ill-formed. The substitution and semantic
constraint checking proceeds in lexical order and stops when a condition that
determines the result of the requires-expression is encountered. If
substitution (if any) and semantic constraint checking succeed, the
requires-expression evaluates to true.
#include <concepts>
struct S {
double value;
};
template <class T>
concept fp_or_value = requires (T x) {
requires std::floating_point<decltype(x.value)> || std::floating_point<T>;
};
template <fp_or_value T>
void test(T x) {}
int main() {
double x = 1.0;
test(x);
}
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