proc_macro_roids 0.8.0

Traits and functions to make writing proc macros more ergonomic.
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

use syn::{DeriveInput, Fields, FieldsUnnamed};

use crate::DeriveInputStructExt;

const ERR_MUST_BE_UNIT_OR_UNNAMED: &str = "Macro must be used on either a unit struct or tuple struct.\n\
     This derive does not work on structs with named fields.";

/// Indicates this type may have `FieldsUnnamed` appended to it.
pub trait FieldsUnnamedAppend {
    /// Appends the specified `fields_unnamed` to this type.
    fn append_unnamed(&mut self, fields_unnamed: FieldsUnnamed);
}

impl FieldsUnnamedAppend for DeriveInput {
    fn append_unnamed(&mut self, fields_unnamed: FieldsUnnamed) {
        self.fields_mut().append_unnamed(fields_unnamed);
    }
}

impl FieldsUnnamedAppend for Fields {
    fn append_unnamed(&mut self, fields_unnamed: FieldsUnnamed) {
        match self {
            Fields::Named(_) => panic!("{}", ERR_MUST_BE_UNIT_OR_UNNAMED),
            Fields::Unit => *self = Fields::from(fields_unnamed),
            Fields::Unnamed(self_fields_unnamed) => {
                self_fields_unnamed.append_unnamed(fields_unnamed)
            }
        }
    }
}

impl FieldsUnnamedAppend for FieldsUnnamed {
    fn append_unnamed(&mut self, fields_unnamed: FieldsUnnamed) {
        self.unnamed.extend(fields_unnamed.unnamed);
    }
}

#[cfg(test)]
mod tests {
    use syn::{parse_quote, DeriveInput, Fields, FieldsUnnamed};

    use super::FieldsUnnamedAppend;

    #[test]
    fn append_fields_unnamed_to_fields_unnamed() {
        let mut fields: FieldsUnnamed = parse_quote!((u32, i32));
        let fields_additional: FieldsUnnamed = parse_quote!((i64, usize));
        let fields_expected: FieldsUnnamed = parse_quote!((u32, i32, i64, usize));

        fields.append_unnamed(fields_additional);

        assert_eq!(fields_expected, fields);
    }

    #[test]
    fn append_fields_unnamed_to_fields_unit() {
        let mut fields = Fields::Unit;
        let fields_additional: FieldsUnnamed = parse_quote!((i64, usize));
        let fields_expected: Fields = Fields::Unnamed(parse_quote!((i64, usize)));

        fields.append_unnamed(fields_additional);

        assert_eq!(fields_expected, fields);
    }

    #[test]
    #[should_panic(
        expected = "Macro must be used on either a unit struct or tuple struct.\n\
                    This derive does not work on structs with named fields."
    )]
    fn append_fields_unnamed_to_fields_unnamed_panics() {
        let mut fields: Fields = Fields::Named(parse_quote!({ a: u32, b: i32 }));
        let fields_additional: FieldsUnnamed = parse_quote!((i64, usize));

        fields.append_unnamed(fields_additional);
    }

    #[test]
    fn append_fields_unnamed_to_struct_unnamed() {
        let mut ast: DeriveInput = parse_quote! {
            struct StructUnnamed(u32, i32);
        };

        let fields_additional: FieldsUnnamed = parse_quote!((i64, usize));
        ast.append_unnamed(fields_additional);

        let ast_expected: DeriveInput = parse_quote! {
            struct StructUnnamed(u32, i32, i64, usize);
        };
        assert_eq!(ast_expected, ast);
    }

    #[test]
    fn append_fields_unnamed_to_struct_unit() {
        let mut ast: DeriveInput = parse_quote! {
            struct StructUnit;
        };

        let fields_additional: FieldsUnnamed = parse_quote!((i64, usize));
        ast.append_unnamed(fields_additional);

        let ast_expected: DeriveInput = parse_quote! {
            struct StructUnit(i64, usize);
        };
        assert_eq!(ast_expected, ast);
    }
}