Rust Quick Start Guide

Patterns assign values to variable names

When we use a variable name in a pattern, it matches any value and the matched value is stored in the variable. That means that if we were to try this:

let x = 5;let source6 = DemoStruct {id: 7, name: String::from("oops"), probability: 0.26};if let DemoStruct { id: x, name: _, probability: _ } = source6 {    println!("The pattern matched, x is {}", x);}

We do not get a pattern that compares the source6.id value to the value of x (five in this case), we don't get what we expect.

Instead, we get an error saying that the pattern is irrefutable:

Irrefutable means the pattern will never fail to match, which ...