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
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134

use std::fmt::{self, Debug};
use std::hash::Hash;

pub(crate) mod tree;
pub(crate) use tree::Tree;

pub(crate) mod nfa;
pub(crate) use nfa::Nfa;

pub(crate) mod dfa;
pub(crate) use dfa::Dfa;

#[derive(Debug)]
pub(crate) struct Uninhabited;

/// An instance of a byte is either initialized to a particular value, or uninitialized.
#[derive(Hash, Eq, PartialEq, Clone, Copy)]
pub(crate) enum Byte {
    Uninit,
    Init(u8),
}

impl fmt::Debug for Byte {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match &self {
            Self::Uninit => f.write_str("??u8"),
            Self::Init(b) => write!(f, "{b:#04x}u8"),
        }
    }
}

pub(crate) trait Def: Debug + Hash + Eq + PartialEq + Copy + Clone {
    fn has_safety_invariants(&self) -> bool;
}
pub trait Ref: Debug + Hash + Eq + PartialEq + Copy + Clone {
    fn min_align(&self) -> usize;

    fn size(&self) -> usize;

    fn is_mutable(&self) -> bool;
}

impl Def for ! {
    fn has_safety_invariants(&self) -> bool {
        unreachable!()
    }
}

impl Ref for ! {
    fn min_align(&self) -> usize {
        unreachable!()
    }
    fn size(&self) -> usize {
        unreachable!()
    }
    fn is_mutable(&self) -> bool {
        unreachable!()
    }
}

#[cfg(feature = "rustc")]
pub mod rustc {
    use std::fmt::{self, Write};

    use rustc_middle::mir::Mutability;
    use rustc_middle::ty::layout::{LayoutCx, LayoutError};
    use rustc_middle::ty::{self, Ty, TyCtxt};
    use rustc_target::abi::Layout;

    /// A reference in the layout.
    #[derive(Debug, Hash, Eq, PartialEq, Clone, Copy)]
    pub struct Ref<'tcx> {
        pub lifetime: ty::Region<'tcx>,
        pub ty: Ty<'tcx>,
        pub mutability: Mutability,
        pub align: usize,
        pub size: usize,
    }

    impl<'tcx> super::Ref for Ref<'tcx> {
        fn min_align(&self) -> usize {
            self.align
        }

        fn size(&self) -> usize {
            self.size
        }

        fn is_mutable(&self) -> bool {
            match self.mutability {
                Mutability::Mut => true,
                Mutability::Not => false,
            }
        }
    }
    impl<'tcx> Ref<'tcx> {}

    impl<'tcx> fmt::Display for Ref<'tcx> {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            f.write_char('&')?;
            if self.mutability == Mutability::Mut {
                f.write_str("mut ")?;
            }
            self.ty.fmt(f)
        }
    }

    /// A visibility node in the layout.
    #[derive(Debug, Hash, Eq, PartialEq, Clone, Copy)]
    pub enum Def<'tcx> {
        Adt(ty::AdtDef<'tcx>),
        Variant(&'tcx ty::VariantDef),
        Field(&'tcx ty::FieldDef),
        Primitive,
    }

    impl<'tcx> super::Def for Def<'tcx> {
        fn has_safety_invariants(&self) -> bool {
            // Rust presently has no notion of 'unsafe fields', so for now we
            // make the conservative assumption that everything besides
            // primitive types carry safety invariants.
            self != &Self::Primitive
        }
    }

    pub(crate) fn layout_of<'tcx>(
        cx: LayoutCx<'tcx, TyCtxt<'tcx>>,
        ty: Ty<'tcx>,
    ) -> Result<Layout<'tcx>, &'tcx LayoutError<'tcx>> {
        use rustc_middle::ty::layout::LayoutOf;
        let ty = cx.tcx.erase_regions(ty);
        cx.layout_of(ty).map(|tl| tl.layout)
    }
}