There are some concepts like lifetime that you have to learn. But you can always use unsafe pointer and look at Rust as a modern version of C.
I cannot determine if the syntax of Rust is "better" than that of C.
At least the ISO "C" std. organization publishes a complete syntax of their language.
Perhaps someone knows where there is a complete grammar for the Rust language?
I cannot find one.
Could you elaborate more why the complete grammar of Rust is important for writing a compiler (for any programming langugage) in Rust?
I thought the question was about whether to write a compiler in Rust or C. But it seems you meant writing a parser that parsed the Rust language itself. Or there's something I misunderstand here.