rust/tests/ui/lint/lint-const-item-mutation.rs

//@ check-pass

struct MyStruct {
    field: bool,
    inner_array: [char; 1],
    raw_ptr: *mut u8
}
impl MyStruct {
    fn use_mut(&mut self) {}
}

struct Mutable {
    msg: &'static str,
}
impl Drop for Mutable {
    fn drop(&mut self) {
        println!("{}", self.msg);
    }
}

struct Mutable2 { // this one has drop glue but not a Drop impl
    msg: &'static str,
    other: String,
}

const ARRAY: [u8; 1] = [25];
const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'], raw_ptr: 2 as *mut u8 };
const RAW_PTR: *mut u8 = 1 as *mut u8;
const MUTABLE: Mutable = Mutable { msg: "" };
const MUTABLE2: Mutable2 = Mutable2 { msg: "", other: String::new() };
const VEC: Vec<i32> = Vec::new();
const PTR: *mut () = 1 as *mut _;
const PTR_TO_ARRAY: *mut [u32; 4] = 0x12345678 as _;
const ARRAY_OF_PTR: [*mut u32; 1] = [1 as *mut _];

fn main() {
    ARRAY[0] = 5; //~ WARN attempting to modify
    MY_STRUCT.field = false; //~ WARN attempting to modify
    MY_STRUCT.inner_array[0] = 'b'; //~ WARN attempting to modify
    MY_STRUCT.use_mut(); //~ WARN taking
    &mut MY_STRUCT; //~ WARN taking
    (&mut MY_STRUCT).use_mut(); //~ WARN taking

    // Test that we don't warn when writing through
    // a raw pointer
    // This is U.B., but this test is check-pass,
    // so this never actually executes
    unsafe {
        *RAW_PTR = 0;
        *MY_STRUCT.raw_ptr = 0;
    }

    MUTABLE.msg = "wow"; // no warning, because Drop observes the mutation
    MUTABLE2.msg = "wow"; //~ WARN attempting to modify
    VEC.push(0); //~ WARN taking a mutable reference to a `const` item

    // Test that we don't warn when converting a raw pointer
    // into a mutable reference
    unsafe { &mut *PTR };

    // Test that we don't warn when there's a dereference involved.
    // If we ever 'leave' the const via a deference, we're going
    // to end up modifying something other than the temporary
    unsafe { (*PTR_TO_ARRAY)[0] = 1 };
    unsafe { *ARRAY_OF_PTR[0] = 25; }
}