educe 0.8.1

This crate offers procedural macros designed to facilitate the swift implementation of Rust's built-in traits.
Documentation 
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

use syn::{Data, DeriveInput, ExprPath, Fields, Meta, Type};

use super::{
    TraitHandler,
    models::{FieldAttributeBuilder, TypeAttributeBuilder},
};
use crate::{
    Trait,
    common::{bound::BOUND_EXCEPTIONS_HASH, ident_index::IdentOrIndex, quote_mixed},
    trait_handlers::TraitHandlerContext,
};

/// Generates the `Hash` implementation for an enum.
pub(crate) struct HashEnumHandler;

impl TraitHandler for HashEnumHandler {
    #[inline]
    fn trait_meta_handler<'a>(
        ast: &'a DeriveInput,
        _ctx: &mut TraitHandlerContext<'a>,
        token_stream: &mut proc_macro2::TokenStream,
        traits: &[Trait],
        meta: &Meta,
    ) -> syn::Result<()> {
        let generated_impl_attributes =
            crate::common::attributes::generated_impl_attributes(&ast.attrs);

        let type_attribute =
            TypeAttributeBuilder {
                enable_flag: true, enable_unsafe: false, enable_bound: true
            }
            .build_from_hash_meta(meta)?;

        let mut hash_types: Vec<&Type> = Vec::new();

        let mut hash_token_stream = proc_macro2::TokenStream::new();

        let mut arms_token_stream = proc_macro2::TokenStream::new();

        if let Data::Enum(data) = &ast.data {
            let built_in_hash: ExprPath =
                syn::parse2(quote_mixed!(::core::hash::Hash::hash)).unwrap();

            for (variant_index, variant) in data.variants.iter().enumerate() {
                let _ = TypeAttributeBuilder {
                    enable_flag:   false,
                    enable_unsafe: false,
                    enable_bound:  false,
                }
                .build_from_attributes(&variant.attrs, traits)?;

                let variant_ident = &variant.ident;

                if let Fields::Unit = &variant.fields {
                    arms_token_stream.extend(quote_mixed! {
                        Self::#variant_ident => {
                            ::core::hash::Hash::hash(&#variant_index, state);
                        }
                    });

                    continue;
                }

                let mut pattern_token_stream = proc_macro2::TokenStream::new();
                let mut block_token_stream = proc_macro2::TokenStream::new();

                for (index, field) in variant.fields.iter().enumerate() {
                    let field_attribute = FieldAttributeBuilder {
                        enable_ignore: true,
                        enable_method: true,
                    }
                    .build_from_attributes(&field.attrs, traits)?;

                    let field_name =
                        IdentOrIndex::from_ident_with_index(field.ident.as_ref(), index);

                    if field_attribute.ignore {
                        pattern_token_stream.extend(field_name.to_field(&quote_mixed!(_)));

                        continue;
                    }

                    let field_name_var = field_name.to_binding("_v_");

                    pattern_token_stream
                        .extend(field_name.to_field(&quote_mixed!(#field_name_var)));

                    let hash = field_attribute.method.as_ref().unwrap_or_else(|| {
                        hash_types.push(&field.ty);
                        &built_in_hash
                    });

                    block_token_stream.extend(quote_mixed!( #hash(#field_name_var, state); ));
                }

                let pattern = if let Fields::Named(_) = &variant.fields {
                    quote_mixed!(Self::#variant_ident { #pattern_token_stream })
                } else {
                    quote_mixed!(Self::#variant_ident ( #pattern_token_stream ))
                };

                arms_token_stream.extend(quote_mixed! {
                    #pattern => {
                        ::core::hash::Hash::hash(&#variant_index, state);

                        #block_token_stream
                    }
                });
            }
        }

        if !arms_token_stream.is_empty() {
            hash_token_stream.extend(quote_mixed! {
                match self {
                    #arms_token_stream
                }
            });
        }

        let ident = &ast.ident;
        let hasher_ident = crate::common::generics::UsedIdents::new(ast).select("H");

        let bound = type_attribute.bound.into_where_predicates_by_generic_parameters_check_types(
            &ast.generics.params,
            &syn::parse2(quote_mixed!(::core::hash::Hash)).unwrap(),
            &hash_types,
            &ast.ident,
            &BOUND_EXCEPTIONS_HASH,
        );

        let generics = crate::common::generics::with_predicates(ast.generics.clone(), bound);

        let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();

        token_stream.extend(quote_mixed! {
            #generated_impl_attributes
            impl #impl_generics ::core::hash::Hash for #ident #ty_generics #where_clause {
                #[inline]
                fn hash<#hasher_ident: ::core::hash::Hasher>(&self, state: &mut #hasher_ident) {
                    #hash_token_stream
                }
            }
        });

        Ok(())
    }
}