'assertion failed: found_namespace_keyword' when parsing C++20 nested inline namespace definition

[cpeterso]

I hit this found_namespace_keyword assertion failure when trying to parse a C++ file compiled with -std=c++20. My C++ file doesn't use any C++20 functionality, but compiling with -std=c++20 pulls in some C++20 std header files that use C++20's nested inline namespaces. In particular:

/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.sdk/usr/include/c++/v1/concepts

namespace ranges::inline __cpo {
  inline constexpr auto swap = __swap::__fn{};
} // namespace ranges::__cpo

Input C/C++ Header

namespace A::inline B { }

Bindgen Invocation

$ bindgen test.cpp -- -std=c++20

or

$ bindgen --enable-cxx-namespaces test.cpp -- -std=c++20

Actual Results

thread 'main' panicked at 'assertion failed: found_namespace_keyword', /Users/chris/.cargo/registry/src/github.com-1ecc6299db9ec823/bindgen-0.60.1/src/ir/context.rs:2127:21
stack backtrace:
   0: rust_begin_unwind
             at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/std/src/panicking.rs:584:5
   1: core::panicking::panic_fmt
             at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/core/src/panicking.rs:142:14
   2: core::panicking::panic
             at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/core/src/panicking.rs:48:5
   3: bindgen::ir::context::BindgenContext::module
   4: <bindgen::ir::item::Item as bindgen::parse::ClangItemParser>::parse
   5: bindgen::clang::visit_children
   6: __ZN5clang8cxcursor13CursorVisitor5VisitE8CXCursorb
   7: __ZN5clang8cxcursor13CursorVisitor23handleDeclForVisitationEPKNS_4DeclE
   8: __ZN5clang8cxcursor13CursorVisitor13VisitChildrenE8CXCursor
   9: _clang_visitChildren
  10: clang_sys::clang_visitChildren
  11: <bindgen::ir::item::Item as bindgen::parse::ClangItemParser>::parse
  12: bindgen::clang::visit_children
  13: __ZN5clang8cxcursor13CursorVisitor5VisitE8CXCursorb
  14: __ZN5clang8cxcursor13CursorVisitor23handleDeclForVisitationEPKNS_4DeclE
  15: __ZN5clang8cxcursor13CursorVisitor13VisitChildrenE8CXCursor
  16: _clang_visitChildren
  17: clang_sys::clang_visitChildren
  18: bindgen::Builder::generate
  19: std::panicking::try
  20: bindgen::main

Expected Results

The nested inline namespace definition should be parsed according to https://en.cppreference.com/w/cpp/language/namespace:

9. nested inline namespace definition: namespace A::B::inline C { ... } is equivalent to namespace A::B { inline namespace C { ... } }. inline may appear in front of every namespace name except the first: namespace A::inline B::C {} is equivalent to namespace A { inline namespace B { namespace C {} } }.