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
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178

// SPDX-FileCopyrightText: 2017 - 2022 Kamila Borowska <kamila@borowska.pw>
// SPDX-FileCopyrightText: 2018 hcpl <hcpl.prog@gmail.com>
// SPDX-FileCopyrightText: 2019 mara <vmedea@protonmail.com>
// SPDX-FileCopyrightText: 2021 Bruno Corrêa Zimmermann <brunoczim@gmail.com>
// SPDX-FileCopyrightText: 2021 Dietrich <dietrich@teilgedanken.de>
//
// SPDX-License-Identifier: MIT OR Apache-2.0

//! Procedural macro implementing `#[derive(Enum)]`
//!
//! This is supposed to used with `enum-map` crate, which provides the
//! actual usage documentation.

mod derive_enum;
mod derive_struct;

use proc_macro2::TokenStream;
use quote::quote;
use syn::{Data, DeriveInput, Type};

/// Derive macro generating an implementation of trait `Enum`.
///
/// When using a derive, enum maps are maintained in the order in which
/// enum variants are declared. This is reflected in the value returned
/// by `Enum::into_usize`, iterators of enum map as well as
/// `EnumMap::as_slice` method.
///
/// # Examples
///
/// ## Enums Without Payload
/// ```
/// use enum_map::Enum;
///
/// #[derive(Enum, Debug, PartialEq, Eq)]
/// enum A {
///     B,
///     C,
///     D,
/// }
///
/// assert_eq!(A::B.into_usize(), 0);
/// assert_eq!(A::C.into_usize(), 1);
/// assert_eq!(A::D.into_usize(), 2);
///
/// assert_eq!(A::from_usize(0), A::B);
/// assert_eq!(A::from_usize(1), A::C);
/// assert_eq!(A::from_usize(2), A::D);
/// ```
///
/// ## Enums With Payload
///
/// ```
/// use enum_map::Enum;
///
/// #[derive(Enum, Debug, PartialEq, Eq)]
/// enum A {
///     B,
///     C,
///     D,
/// }
///
/// #[derive(Enum, Debug, PartialEq, Eq)]
/// enum X {
///     Y,
///     Z,
/// }
///
/// #[derive(Enum, Debug, PartialEq, Eq)]
/// enum Foo {
///     Bar(bool, A),
///     Empty,
///     Baz { fa: A, fx: X },
/// }
///
/// assert_eq!(Foo::Bar(false, A::B).into_usize(), 0);
/// assert_eq!(Foo::Bar(false, A::D).into_usize(), 4);
/// assert_eq!(Foo::Bar(true, A::B).into_usize(), 1);
/// assert_eq!(Foo::Bar(true, A::C).into_usize(), 3);
/// assert_eq!(Foo::Empty.into_usize(), 6);
/// assert_eq!(Foo::Baz { fa: A::B, fx: X::Y }.into_usize(), 7);
/// assert_eq!(Foo::Baz { fa: A::B, fx: X::Z }.into_usize(), 10);
/// assert_eq!(Foo::Baz { fa: A::D, fx: X::Y }.into_usize(), 9);
///
/// assert_eq!(Foo::from_usize(0), Foo::Bar(false, A::B));
/// assert_eq!(Foo::from_usize(4), Foo::Bar(false, A::D));
/// assert_eq!(Foo::from_usize(1), Foo::Bar(true, A::B));
/// assert_eq!(Foo::from_usize(3), Foo::Bar(true, A::C));
/// assert_eq!(Foo::from_usize(6), Foo::Empty);
/// assert_eq!(Foo::from_usize(7), Foo::Baz { fa: A::B, fx: X::Y });
/// assert_eq!(Foo::from_usize(10), Foo::Baz { fa: A::B, fx: X::Z });
/// assert_eq!(Foo::from_usize(9), Foo::Baz { fa: A::D, fx: X::Y });
///
/// ```
///
/// ## Structs
///
/// ```
/// use enum_map::Enum;
///
/// #[derive(Enum, Debug, PartialEq, Eq)]
/// enum A {
///     B,
///     C,
///     D,
/// }
///
/// #[derive(Enum, Debug, PartialEq, Eq)]
/// enum X {
///     Y,
///     Z,
/// }
///
/// #[derive(Enum, Debug, PartialEq, Eq)]
/// struct Foo {
///     bar: bool,
///     baz: A,
///     end: X,
/// }
///
/// assert_eq!(Foo { bar: false, baz: A::B, end: X::Y }.into_usize(), 0);
/// assert_eq!(Foo { bar: true, baz: A::B, end: X::Y }.into_usize(), 1);
/// assert_eq!(Foo { bar: false, baz: A::D, end: X::Y }.into_usize(), 4);
/// assert_eq!(Foo { bar: true, baz: A::C, end: X::Z }.into_usize(), 9);
///
/// assert_eq!(Foo::from_usize(0), Foo { bar: false, baz: A::B, end: X::Y });
/// assert_eq!(Foo::from_usize(1), Foo { bar: true, baz: A::B, end: X::Y });
/// assert_eq!(Foo::from_usize(4), Foo { bar: false, baz: A::D, end: X::Y });
/// assert_eq!(Foo::from_usize(9), Foo { bar: true, baz: A::C, end: X::Z });
/// ```
///
/// ## Tuple Structs
///
/// ```
/// use enum_map::Enum;
///
/// #[derive(Enum, Debug, PartialEq, Eq)]
/// enum A {
///     B,
///     C,
///     D,
/// }
///
/// #[derive(Enum, Debug, PartialEq, Eq)]
/// enum X {
///     Y,
///     Z,
/// }
///
/// #[derive(Enum, Debug, PartialEq, Eq)]
/// struct Foo(bool, A, X);
///
/// assert_eq!(Foo(false, A::B, X::Y ).into_usize(), 0);
/// assert_eq!(Foo(true, A::B, X::Y ).into_usize(), 1);
/// assert_eq!(Foo(false, A::D, X::Y ).into_usize(), 4);
/// assert_eq!(Foo(true, A::C, X::Z ).into_usize(), 9);
///
/// assert_eq!(Foo::from_usize(0), Foo(false, A::B, X::Y));
/// assert_eq!(Foo::from_usize(1), Foo(true, A::B, X::Y));
/// assert_eq!(Foo::from_usize(4), Foo(false, A::D, X::Y));
/// assert_eq!(Foo::from_usize(9), Foo(true, A::C, X::Z));
#[proc_macro_derive(Enum)]
pub fn derive_enum_map(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
    let input: DeriveInput = syn::parse(input).unwrap();

    let result = match input.data {
        Data::Enum(data_enum) => derive_enum::generate(input.ident, data_enum),
        Data::Struct(data_struct) => derive_struct::generate(input.ident, data_struct),
        _ => quote! { compile_error! {"#[derive(Enum)] is only defined for enums and structs"} },
    };

    result.into()
}

fn type_length(ty: &Type) -> TokenStream {
    quote! {
        <#ty as ::enum_map::Enum>::LENGTH
    }
}