#![feature(core_intrinsics)]
fn print_type_of(_: T) {
println!("{}", unsafe { std::intrinsics::type_name::() });
}

fn main() {
print_type_of(32.90); // prints "f64"
print_type_of(vec![1, 2, 4]); // prints "std::vec::Vec"
print_type_of("foo"); // prints "&str"
}

需要切换rustup到nightly版本才能运行cargo run

查看rustup版本

rustup toolchain list

切换到nightly版本

rustup default nightly