Power-of-two int tests

Most of these have to be deleted; the various power_of_two functions use
`intrinsics::ctlz_nonzero` internally, so they can't be made const
before rust-lang#66275 is merged.

Author: 9999years

src/test/ui/consts/const-int-pow-rpass.rs

@@ -1,11 +1,47 @@
 // run-pass
+// #![feature(const_int_pow)]
+#![feature(wrapping_next_power_of_two)]
 
 const IS_POWER_OF_TWO_A: bool = 0u32.is_power_of_two();
 const IS_POWER_OF_TWO_B: bool = 32u32.is_power_of_two();
 const IS_POWER_OF_TWO_C: bool = 33u32.is_power_of_two();
 
+const NEXT_POWER_OF_TWO_A: u32 = 0u32.next_power_of_two();
+const NEXT_POWER_OF_TWO_B: u8 = 2u8.next_power_of_two();
+const NEXT_POWER_OF_TWO_C: u8 = 3u8.next_power_of_two();
+const NEXT_POWER_OF_TWO_D: u8 = 127u8.next_power_of_two();
+
+const CHECKED_NEXT_POWER_OF_TWO_A: Option<u32> = 0u32.checked_next_power_of_two();
+const CHECKED_NEXT_POWER_OF_TWO_B: Option<u8> = 2u8.checked_next_power_of_two();
+const CHECKED_NEXT_POWER_OF_TWO_C: Option<u8> = 3u8.checked_next_power_of_two();
+const CHECKED_NEXT_POWER_OF_TWO_D: Option<u8> = 127u8.checked_next_power_of_two();
+const CHECKED_NEXT_POWER_OF_TWO_E: Option<u8> = 129u8.checked_next_power_of_two();
+
+const WRAPPING_NEXT_POWER_OF_TWO_A: u32 = 0u32.wrapping_next_power_of_two();
+const WRAPPING_NEXT_POWER_OF_TWO_B: u8 = 2u8.wrapping_next_power_of_two();
+const WRAPPING_NEXT_POWER_OF_TWO_C: u8 = 3u8.wrapping_next_power_of_two();
+const WRAPPING_NEXT_POWER_OF_TWO_D: u8 = 127u8.wrapping_next_power_of_two();
+const WRAPPING_NEXT_POWER_OF_TWO_E: u8 = u8::max_value().wrapping_next_power_of_two();
+
 fn main() {
     assert!(!IS_POWER_OF_TWO_A);
     assert!(IS_POWER_OF_TWO_B);
     assert!(!IS_POWER_OF_TWO_C);
+
+    assert_eq!(NEXT_POWER_OF_TWO_A, 2);
+    assert_eq!(NEXT_POWER_OF_TWO_B, 2);
+    assert_eq!(NEXT_POWER_OF_TWO_C, 4);
+    assert_eq!(NEXT_POWER_OF_TWO_D, 128);
+
+    assert_eq!(CHECKED_NEXT_POWER_OF_TWO_A, Some(2));
+    assert_eq!(CHECKED_NEXT_POWER_OF_TWO_B, Some(2));
+    assert_eq!(CHECKED_NEXT_POWER_OF_TWO_C, Some(4));
+    assert_eq!(CHECKED_NEXT_POWER_OF_TWO_D, Some(128));
+    assert_eq!(CHECKED_NEXT_POWER_OF_TWO_E, None);
+
+    assert_eq!(WRAPPING_NEXT_POWER_OF_TWO_A, 2);
+    assert_eq!(WRAPPING_NEXT_POWER_OF_TWO_B, 2);
+    assert_eq!(WRAPPING_NEXT_POWER_OF_TWO_C, 4);
+    assert_eq!(WRAPPING_NEXT_POWER_OF_TWO_D, 128);
+    assert_eq!(WRAPPING_NEXT_POWER_OF_TWO_E, 0);
 }