test for overflow-checks=off

Author: RalfJung

tests/run-pass/overflow_checks_off.rs

@@ -0,0 +1,18 @@
+// compile-flags: -C overflow-checks=off
+
+// Check that we correctly implement the intended behavior of these operators
+// when they are not being overflow-checked.
+
+// FIXME: if we call the functions in `std::ops`, we still get the panics.
+// Miri does not implement the codegen-time hack that backs `#[rustc_inherit_overflow_checks]`.
+// use std::ops::*;
+
+fn main() {
+    assert_eq!(-{-0x80i8}, -0x80);
+
+    assert_eq!(0xffu8 + 1, 0_u8);
+    assert_eq!(0u8 - 1, 0xff_u8);
+    assert_eq!(0xffu8 * 2, 0xfe_u8);
+    assert_eq!(1u8 << 9, 2_u8);
+    assert_eq!(2u8 >> 9, 1_u8);
+}