Function is_c_source_file 

pub fn is_c_source_file(file: &ProjectFile) -> bool

Whether file is proven to use plain-C source semantics.

Language::Cpp intentionally serves both C and C++. Headers do not carry a compilation dialect on their own, so only an exact .c source extension is sufficient to reinterpret C++-grammar keyword nodes such as this as C identifiers.

The exact-lowercase-.c rule itself lives in LanguageDialect::for_path, which extraction reads too (a .c file is extracted with C tag scope), so the doctrine has exactly one definition.