C++20 `char8_t[N]` panics (`Not able to resolve array element?: Recurse`); scalar `char8_t` is `u8`

Input C/C++ Header

char8_t S[4];

Bindgen Invocation

$ bindgen input.h -- -x c++ -std=c++20

Actual Results

bindgen 0.72.1 and 0.73.1 abort while parsing the array type:

panicked at bindgen/ir/ty.rs:1196:22:
Not able to resolve array element?: Recurse
panic in a function that cannot unwind
thread caused non-unwinding panic. aborting.

libclang has no CXType_Char8. A char8_t scalar is Unexposed and bindgen canonicalizes it to u8 (char8_t take(char8_t) works). A char8_t array keeps an Unexposed element type; from_clang_ty returns ParseError::Recurse, and the CXType_ConstantArray arm does .expect("Not able to resolve array element?").

The same abort happens for const char8_t S[] = u8"hi";, char8_t a[]; (incomplete), void take(char8_t a[4]);, and char8_t a[2][2];. char16_t S[4] and char32_t S[4] generate [u16; 4] / [u32; 4] and do not abort. A char8_t field or pointer does not abort.

Not #3464 (that is enum class : char8_t enumerator sign). Not #2475 (unicode character macros).

Expected Results

Do not abort. Treat char8_t[N] as [u8; N], matching the scalar char8_t → u8 mapping.

Environment

bindgen: 0.72.1 and 0.73.1 (rust-lang/rust-bindgen 77cbc723)
clang/libclang: Homebrew clang 21.1.8
rustc: 1.97.1
target: aarch64-apple-darwin
OS: macOS

Start by reproducing the bindgen input and invocation from the issue, then inspect bindgen/ir/ty.rs around from_clang_ty and the CXType_ConstantArray handling near line 1196. Trace why scalar char8_t becomes u8 while an array element returns ParseError::Recurse. Done means the listed char8_t array forms no longer abort and the fixed-size case generates [u8; 4].