How to fix Rust E0277 Display not implemented

The error E0277 occurs because the type you are trying to format with {} does not implement the std::fmt::Display trait. Add a Display bound to your generic type parameter or implement the trait for your custom type. For generic functions, add T: Display to the type constraints:

use std::fmt::Display;

fn print_value<T: Display>(value: T) {
    println!("The value is: {}", value);
}

For custom structs, implement the trait manually:

use std::fmt;

struct MyStruct {
    value: i32,
}

impl fmt::Display for MyStruct {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "MyStruct({})", self.value)
    }
}

If you only need to see the value for debugging and don't need custom formatting, use the {:?} format specifier instead, which requires the Debug trait.

The Rust E0277 Display not implemented error means Rust doesn't know how to turn your data into a string for printing. Think of it like trying to speak a language you haven't learned yet; the computer needs a specific set of rules (the Display trait) to translate your data into text. You fix it by either teaching the computer those rules for your specific data type or by telling the function that it only accepts data types that already know how to speak.