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#![warn(clippy::transmute_ptr_to_ptr)]
#![allow(clippy::borrow_as_ptr)]
// Make sure we can modify lifetimes, which is one of the recommended uses
// of transmute
// Make sure we can do static lifetime transmutes
unsafe fn transmute_lifetime_to_static<'a, T>(t: &'a T) -> &'static T {
std::mem::transmute::<&'a T, &'static T>(t)
}
// Make sure we can do non-static lifetime transmutes
unsafe fn transmute_lifetime<'a, 'b, T>(t: &'a T, u: &'b T) -> &'b T {
std::mem::transmute::<&'a T, &'b T>(t)
}
struct LifetimeParam<'a> {
s: &'a str,
}
struct GenericParam<T> {
t: T,
}
fn transmute_ptr_to_ptr() {
let ptr = &1u32 as *const u32;
let mut_ptr = &mut 1u32 as *mut u32;
unsafe {
// pointer-to-pointer transmutes; bad
let _: *const f32 = std::mem::transmute(ptr);
let _: *mut f32 = std::mem::transmute(mut_ptr);
// ref-ref transmutes; bad
let _: &f32 = std::mem::transmute(&1u32);
let _: &f64 = std::mem::transmute(&1f32);
// ^ this test is here because both f32 and f64 are the same TypeVariant, but they are not
// the same type
let _: &mut f32 = std::mem::transmute(&mut 1u32);
let _: &GenericParam<f32> = std::mem::transmute(&GenericParam { t: 1u32 });
}
// these are recommendations for solving the above; if these lint we need to update
// those suggestions
let _ = ptr as *const f32;
let _ = mut_ptr as *mut f32;
let _ = unsafe { &*(&1u32 as *const u32 as *const f32) };
let _ = unsafe { &mut *(&mut 1u32 as *mut u32 as *mut f32) };
// transmute internal lifetimes, should not lint
let s = "hello world".to_owned();
let lp = LifetimeParam { s: &s };
let _: &LifetimeParam<'static> = unsafe { std::mem::transmute(&lp) };
let _: &GenericParam<&LifetimeParam<'static>> = unsafe { std::mem::transmute(&GenericParam { t: &lp }) };
}
// dereferencing raw pointers in const contexts, should not lint as it's unstable (issue 5959)
const _: &() = {
struct Zst;
let zst = &Zst;
unsafe { std::mem::transmute::<&'static Zst, &'static ()>(zst) }
};
fn main() {}
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