rust/src/test/ui/consts/const-eval/ub-enum.rs

// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

#![allow(const_err)] // make sure we cannot allow away the errors tested here

#[repr(usize)]
#[derive(Copy, Clone)]
enum Enum {
    A = 0,
}
union TransmuteEnum {
    a: &'static u8,
    b: Enum,
}

// A pointer is guaranteed non-null
const BAD_ENUM: Enum = unsafe { TransmuteEnum { a: &1 }.b };
//~^ ERROR is undefined behavior

// Invalid enum discriminant
#[repr(usize)]
#[derive(Copy, Clone)]
enum Enum2 {
    A = 2,
}
union TransmuteEnum2 {
    a: usize,
    b: Enum2,
}
const BAD_ENUM2 : Enum2 = unsafe { TransmuteEnum2 { a: 0 }.b };
//~^ ERROR is undefined behavior

// Invalid enum field content (mostly to test printing of apths for enum tuple
// variants and tuples).
union TransmuteChar {
    a: u32,
    b: char,
}
// Need to create something which does not clash with enum layout optimizations.
const BAD_ENUM_CHAR : Option<(char, char)> = Some(('x', unsafe { TransmuteChar { a: !0 }.b }));
//~^ ERROR is undefined behavior

fn main() {
}