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//@ check-pass
#![allow(dead_code)]
trait Structure<E>: Sized where E: Encoding {
type RefTarget: ?Sized;
type FfiPtr;
unsafe fn borrow_from_ffi_ptr<'a>(ptr: Self::FfiPtr) -> Option<&'a Self::RefTarget>;
}
enum Slice {}
impl<E> Structure<E> for Slice where E: Encoding {
type RefTarget = [E::Unit];
type FfiPtr = (*const E::FfiUnit, usize);
unsafe fn borrow_from_ffi_ptr<'a>(_ptr: Self::FfiPtr) -> Option<&'a Self::RefTarget> {
panic!()
}
}
trait Encoding {
type Unit: Unit;
type FfiUnit;
}
trait Unit {}
enum Utf16 {}
impl Encoding for Utf16 {
type Unit = Utf16Unit;
type FfiUnit = u16;
}
struct Utf16Unit(pub u16);
impl Unit for Utf16Unit {}
struct SUtf16Str {
_data: <Slice as Structure<Utf16>>::RefTarget,
}
impl SUtf16Str {
pub unsafe fn from_ptr<'a>(ptr: <Slice as Structure<Utf16>>::FfiPtr)
-> Option<&'a Self> {
std::mem::transmute::<Option<&[<Utf16 as Encoding>::Unit]>, _>(
<Slice as Structure<Utf16>>::borrow_from_ffi_ptr(ptr))
}
}
fn main() {
const TEXT_U16: &'static [u16] = &[];
let _ = unsafe { SUtf16Str::from_ptr((TEXT_U16.as_ptr(), TEXT_U16.len())).unwrap() };
}
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