auto_enums_derive 0.5.4

This library provides an attribute macro like a wrapper of `#[derive]`, implementing the supported traits and passing unsupported traits to `#[derive]`.
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

use proc_macro2::TokenStream;

use crate::utils::*;

pub(crate) const NAME: &[&str] = &["Transpose"];

// Implementing this with `Into` requires many type annotations.
pub(crate) fn derive(data: &Data, stack: &mut Stack<ItemImpl>) -> Result<()> {
    check_fields(data)?;

    stack.push(transpose_option(data)?);
    stack.push(transpose_result(data)?);
    stack.push(transpose_ok(data)?);
    stack.push(transpose_err(data)?);

    Ok(())
}

fn check_fields(data: &Data) -> Result<()> {
    let generics = data.generics();
    let fields = data.fields();
    let comma = if generics.params.empty_or_trailing() {
        quote!(,)
    } else {
        TokenStream::new()
    };
    if quote!(#generics).to_string() != quote!(<#(#fields),*#comma>).to_string() {
        Err(err!(data.span, "all fields need to be generics"))?;
    }

    Ok(())
}

fn transpose_option(data: &Data) -> Result<ItemImpl> {
    let ident = data.ident();
    let fields = data.fields();

    let mut impls = data.impl_with_capacity(1)?;

    let ty_generics = fields.iter().map(|f| quote!(::core::option::Option<#f>));
    *impls.self_ty() = parse_quote!(#ident<#(#ty_generics),*>)?;

    let transpose = data
        .variants()
        .iter()
        .map(|v| quote!(#ident::#v(x) => x.map(#ident::#v)));

    impls.push_item(parse_quote! {
        #[inline]
        fn transpose(self) -> ::core::option::Option<#ident<#(#fields),*>> {
            match self { #(#transpose,)* }
        }
    }?);

    Ok(impls.build_item())
}

fn transpose_result(data: &Data) -> Result<ItemImpl> {
    let fields = data.fields();

    let mut impls = data.impl_with_capacity(1)?;

    let err_fields: &Stack<_> = &(0..fields.len())
        .map(|i| {
            let id = &format!("__E{}", i);
            impls.push_generic_param(param_ident(id));
            ident(id)
        })
        .collect();

    let ident = data.ident();
    let ty_generics = fields
        .iter()
        .zip(err_fields.iter())
        .map(|(f, ef)| quote!(::core::result::Result<#f, #ef>));
    *impls.self_ty() = parse_quote!(#ident<#(#ty_generics),*>)?;

    let transpose = data
        .variants()
        .iter()
        .map(|v| quote!(#ident::#v(x) => x.map(#ident::#v).map_err(#ident::#v)));

    impls.push_item(parse_quote! {
        #[inline]
        fn transpose(self) -> ::core::result::Result<#ident<#(#fields),*>, #ident<#(#err_fields),*>> {
            match self { #(#transpose,)* }
        }
    }?);

    Ok(impls.build_item())
}

fn transpose_ok(data: &Data) -> Result<ItemImpl> {
    let ident = data.ident();
    let fields = data.fields();

    let mut impls = data.impl_with_capacity(1)?;

    impls.push_generic_param(param_ident("__E"));

    let ty_generics = fields
        .iter()
        .map(|f| quote!(::core::result::Result<#f, __E>));
    *impls.self_ty() = parse_quote!(#ident<#(#ty_generics),*>)?;

    let transpose = data
        .variants()
        .iter()
        .map(|v| quote!(#ident::#v(x) => x.map(#ident::#v)));
    impls.push_item(parse_quote! {
        #[inline]
        fn transpose_ok(self) -> ::core::result::Result<#ident<#(#fields),*>, __E> {
            match self { #(#transpose,)* }
        }
    }?);

    Ok(impls.build_item())
}

fn transpose_err(data: &Data) -> Result<ItemImpl> {
    let ident = data.ident();
    let fields = data.fields();

    let mut impls = data.impl_with_capacity(1)?;

    impls.push_generic_param(param_ident("__T"));

    let ty_generics = fields
        .iter()
        .map(|f| quote!(::core::result::Result<__T, #f>));
    *impls.self_ty() = parse_quote!(#ident<#(#ty_generics),*>)?;

    let transpose = data
        .variants()
        .iter()
        .map(|v| quote!(#ident::#v(x) => x.map_err(#ident::#v)));
    impls.push_item(parse_quote! {
        #[inline]
        fn transpose_err(self) -> ::core::result::Result<__T, #ident<#(#fields),*>> {
            match self { #(#transpose,)* }
        }
    }?);

    Ok(impls.build_item())
}