Generic bounds with where clauses for readable constraints

Functions with multiple generic parameters and trait bounds become unreadable when all constraints are crammed into angle brackets.

Use where clauses to separate generic parameters from their constraints:

use std::fmt::{Debug, Display};

// Hard to read inline style
fn print_pair_inline<T: Debug + Display, U: Debug + Clone>(a: T, b: U) {
    println!("{} {:?} {:?}", a, b.clone(), b);
}

// Much cleaner with where clause
fn print_pair<T, U>(a: T, b: U)
where
    T: Debug + Display,
    U: Debug + Clone,
{
    println!("{} {:?} {:?}", a, b.clone(), b);
}

// Common bounds in structs
struct Wrapper<T>
where
    T: Clone + Debug,
{
    value: T,
}

impl<T> Wrapper<T>
where
    T: Clone + Debug,
{
    pub fn get(&self) -> T {
        self.value.clone()
    }
}

where clauses align constraints vertically, making them easier to scan. They also allow expressing constraints that cannot be written in angle brackets, such as associated type bounds.