Use rust-lang/rfcs#1434.

AndrewKvalheim · AndrewKvalheim · commit 8c9c450d6ef3 · 2019-05-23T17:51:23.000-07:00
diff --git a/grains/src/lib.rs b/grains/src/lib.rs
@@ -1,6 +1,5 @@
 pub fn square(n: u32) -> u64 {
-    // Pending RFC 1303 or RFC 1434
-    if !(1 <= n && n <= 64) {
+    if !((1..=64).contains(&n)) {
         panic!("Square must be between 1 and 64");
     }
 

Original file line number	Diff line number	Diff line change
`@@ -1,6 +1,5 @@`
`1`	`1`	`pub fn square(n: u32) -> u64 {`
`2`		`- // Pending RFC 1303 or RFC 1434`
`3`		`- if !(1 <= n && n <= 64) {`
	`2`	`+ if !((1..=64).contains(&n)) {`
`4`	`3`	`panic!("Square must be between 1 and 64");`
`5`	`4`	`}`
`6`	`5`