Error when using unicode character literals

bindgen panics when it encounters a character literal with a Unicode escape sequence representing a codepoint greater than 128.

Input C/C++ Header

#define OK 'a'
#define PANIC_CHAR_16 u'\uAC00'
#define PANIC_CHAR_32 U'\uAC00'

Bindgen Invocation

$ bindgen input.h -- -x c++
$ cargo run -p bindgen-cli -- input.h -- -x c++

Actual Results

thread 'main' panicked at 'assertion failed: `(left == right)`
  left: `3`,
 right: `1`', /Users/paxbun/.cargo/registry/src/github.com-1ecc6299db9ec823/bindgen-0.60.1/src/ir/var.rs:235:33
stack backtrace:
   0: _rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::panicking::assert_failed_inner
   3: core::panicking::assert_failed
   4: <bindgen::ir::var::Var as bindgen::parse::ClangSubItemParser>::parse
   5: <bindgen::ir::item::Item as bindgen::parse::ClangItemParser>::parse
   6: bindgen::parse_one
   7: bindgen::clang::visit_children
   8: __ZN5clang8cxcursor13CursorVisitor5VisitE8CXCursorb
   9: __ZN5clang8cxcursor13CursorVisitor25visitPreprocessedEntitiesINS_19PreprocessingRecord8iteratorEEEbT_S5_RS3_NS_6FileIDE
  10: __ZN5clang8cxcursor13CursorVisitor13VisitChildrenE8CXCursor
  11: _clang_visitChildren
  12: clang_sys::clang_visitChildren
  13: bindgen::Builder::generate
  14: std::panicking::try
  15: bindgen::main
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

Expected Results

/* automatically generated by rust-bindgen 0.64.0 */

pub const OK: u8 = 97u8;
pub const PANIC_CHAR_16: u16 = 44032; // u16 because its counterpart is char16_t
pub const PANIC_CHAR_32: u32 = 44032; // u32 similarly

Reproduce the panic with the C++ header and bindgen invocation in the issue, then inspect src/ir/var.rs around the reported assertion at line 235. Trace how the u'\uAC00' and U'\uAC00' literals are parsed; done means generation completes and produces u16 and u32 constants with value 44032, without regressing the plain 'a' case.