thiserror-impl 1.0.25

Implementation detail of the `thiserror` crate
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

use crate::ast::{Enum, Field, Struct, Variant};
use syn::{Member, Type};

impl Struct<'_> {
    pub(crate) fn from_field(&self) -> Option<&Field> {
        from_field(&self.fields)
    }

    pub(crate) fn source_field(&self) -> Option<&Field> {
        source_field(&self.fields)
    }

    pub(crate) fn backtrace_field(&self) -> Option<&Field> {
        backtrace_field(&self.fields)
    }
}

impl Enum<'_> {
    pub(crate) fn has_source(&self) -> bool {
        self.variants
            .iter()
            .any(|variant| variant.source_field().is_some() || variant.attrs.transparent.is_some())
    }

    pub(crate) fn has_backtrace(&self) -> bool {
        self.variants
            .iter()
            .any(|variant| variant.backtrace_field().is_some())
    }

    pub(crate) fn has_display(&self) -> bool {
        self.attrs.display.is_some()
            || self.attrs.transparent.is_some()
            || self
                .variants
                .iter()
                .any(|variant| variant.attrs.display.is_some())
            || self
                .variants
                .iter()
                .all(|variant| variant.attrs.transparent.is_some())
    }
}

impl Variant<'_> {
    pub(crate) fn from_field(&self) -> Option<&Field> {
        from_field(&self.fields)
    }

    pub(crate) fn source_field(&self) -> Option<&Field> {
        source_field(&self.fields)
    }

    pub(crate) fn backtrace_field(&self) -> Option<&Field> {
        backtrace_field(&self.fields)
    }
}

impl Field<'_> {
    pub(crate) fn is_backtrace(&self) -> bool {
        type_is_backtrace(self.ty)
    }
}

fn from_field<'a, 'b>(fields: &'a [Field<'b>]) -> Option<&'a Field<'b>> {
    for field in fields {
        if field.attrs.from.is_some() {
            return Some(&field);
        }
    }
    None
}

fn source_field<'a, 'b>(fields: &'a [Field<'b>]) -> Option<&'a Field<'b>> {
    for field in fields {
        if field.attrs.from.is_some() || field.attrs.source.is_some() {
            return Some(&field);
        }
    }
    for field in fields {
        match &field.member {
            Member::Named(ident) if ident == "source" => return Some(&field),
            _ => {}
        }
    }
    None
}

fn backtrace_field<'a, 'b>(fields: &'a [Field<'b>]) -> Option<&'a Field<'b>> {
    for field in fields {
        if field.attrs.backtrace.is_some() {
            return Some(&field);
        }
    }
    for field in fields {
        if field.is_backtrace() {
            return Some(&field);
        }
    }
    None
}

fn type_is_backtrace(ty: &Type) -> bool {
    let path = match ty {
        Type::Path(ty) => &ty.path,
        _ => return false,
    };

    let last = path.segments.last().unwrap();
    last.ident == "Backtrace" && last.arguments.is_empty()
}