Can I detect if an expression is a mutable variable using Rust's macro repetition?

Question

macro_rules! log {
    ($($x:expr),*) => {
        {
            $(
             //how to detect $x in the Macro repetition?

            )*
        }
    };
}

I don't want to use ($($x:ident),*). The log! macro can log the expression and then I want to match the variable type.

Answer 1

Macros only can access token streams, and cannot say anything more about those tokens, apart from what is explicitly given to the macro.

For example, consider this code:

fn main() {
    let mut foo: i32 = 1;
    my_macro!(foo);
}

The only information available to the macro my_macro is the input token foo. It can match that foo is is an identifier but it can't say anything more about it. The fact that there is mutable binding called foo, or that this binding is an i32 are just not available inside the macro.