macro_rules! print_entity { ($x: expr) => { { println!("Object type: {}\nDeclared name: {}\n") } } } For reference of definition, consider:
let the_foo: MyBar = MyBar::new(); In the case of the macro above, the "Declared name" value should equal the_foo. The struct type should equal TheBar. How can this be done?
print_entity!(the_foo); If you only need that for debugging, you can get the compiler to print an error message with the type like this:
let foo: () = 1i32; which gives the following error:
error[E0308]: mismatched types --> src/main.rs:24:15 | 24 | let foo: () = 1i32; | ^^^^ expected (), found i32 | = note: expected type `()` found type `i32` Or, building on @Denys Séguret's comment, you need to define a trait and implement it for every type you may want to print (this can be made easier with a macro too):
trait TypeToStr { fn get_type_str (&self) -> &'static str; } macro_rules! impl_type_to_str { ($($T: ty),+) => { $( impl TypeToStr for $T { fn get_type_str (&self) -> &'static str { stringify!($T) } } )* } } impl_type_to_str!(i32, f64); macro_rules! print_type { ($e: expr) => { println!("{} has type {}", stringify!($e), $e.get_type_str()); } } fn main() { print_type!(1i32); print_type!(3.14f64); } 
the_foo) is easy. To get the type would probably be best achieved by declaring a trait, similar toDebugand implementing it. Are you after something like thedbg!macro ?exprcan take arbitrary expressions. What is the declared name inprint_entity!(some_var + 100 * another_var)?