Array parameter cannot be used in nested consteval function call

[BertalanD]

Godbolt link

The following snippet does not compile with Clang (trunk), but does with MSVC and GCC:

template<unsigned int N>
consteval int inner(char const (&str)[N]) {
    return str[0];
}

template<unsigned int N>
consteval int func(char const (&str)[N]) {
    auto val = inner(str);
    return val;
}

auto var = func("test");

<source>:8:16: error: call to consteval function 'inner<5U>' is not a constant expression
    auto val = inner(str);
               ^
<source>:12:12: note: in instantiation of function template specialization 'func<5U>' requested here
auto var = func("test");
           ^
<source>:8:22: note: function parameter 'str' with unknown value cannot be used in a constant expression
    auto val = inner(str);
                     ^
<source>:7:33: note: declared here
consteval int func(char const (&str)[N]) {

The issue can be worked around by making inner constexpr instead of consteval.

[llvmbot]

@llvm/issue-subscribers-c-20

[llvmbot]

@llvm/issue-subscribers-clang-frontend

[usx95]

Thanks for the report. Looks like the same issue of #51182

[usx95]

Duplicate of #51182