1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41

//! Contains many type aliases for PhantomData with different lifetime variances.
//! 
//! These aliases can be constructed in these ways:
//! 
//! - `PhantomData`
//!
//! - `Variance::<T>::default()`
//! 
//! - `value.ty_()` constructs VariantPhantom
//! - `value.ty_d()` constructs VariantDropPhantom
//! - `value.ty_inv()` constructs InvariantPhantom
//! - `value. ty_inv_ref()` constructs InvariantRefPhantom
//! 
//!
//!
//! Phantom type        lifetime variance       type variance
//!
//! VariantDropPhantom  -                       variant (with drop check)
//! VariantPhantom      -                       variant
//! InvariantRefPhantom invariant               - 
//! InvariantPhantom    -                       invariant


use std_::cell::Cell;
use std_::marker::PhantomData;

/// Type alias for a variant PhantomData with drop check.
pub type VariantDropPhantom<T>=
    PhantomData<T>;

/// Type alias for a variant PhantomData withhout drop-check.
pub type VariantPhantom<T>=
    PhantomData<fn()->T>;

/// Type alias for an invariant PhantomData.
pub type InvariantPhantom<T>=
    PhantomData<fn(T)->T>;

/// Type alias for an PhantomData with an invariant lifetime.
pub type InvariantRefPhantom<'a,T>=
    PhantomData<Cell<&'a T>>;