Stabilize the size of incr comp object file names

compiler/rustc_data_structures/src/base_n/tests.rs

@@ -1,9 +1,17 @@
 use super::*;
 
 #[test]
-fn test_encode() {
+fn limits() {
+    assert_eq!(Ok(u128::MAX), u128::from_str_radix(&u128::MAX.to_base(36), 36));
+    assert_eq!(Ok(u64::MAX), u64::from_str_radix(&u64::MAX.to_base(36), 36));
+    assert_eq!(Ok(u32::MAX), u32::from_str_radix(&u32::MAX.to_base(36), 36));
+}
+
+#[test]
+fn test_to_base() {
     fn test(n: u128, base: usize) {
-        assert_eq!(Ok(n), u128::from_str_radix(&encode(n, base), base as u32));
+        assert_eq!(Ok(n), u128::from_str_radix(&n.to_base(base), base as u32));
+        assert_eq!(Ok(n), u128::from_str_radix(&n.to_base_fixed_len(base), base as u32));
     }
 
     for base in 2..37 {