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
use crate::utils::{
add_extra_generic_param, numbered_vars, AttrParams, DeriveType, MultiFieldData,
State,
};
use proc_macro2::TokenStream;
use quote::{quote, ToTokens};
use syn::{DeriveInput, Result};
use crate::utils::HashMap;
#[allow(clippy::cognitive_complexity)]
pub fn expand(input: &DeriveInput, trait_name: &'static str) -> Result<TokenStream> {
let state = State::with_attr_params(
input,
trait_name,
quote!(::core::convert),
String::from("try_into"),
AttrParams {
enum_: vec!["ignore", "owned", "ref", "ref_mut"],
variant: vec!["ignore", "owned", "ref", "ref_mut"],
struct_: vec!["ignore", "owned", "ref", "ref_mut"],
field: vec!["ignore"],
},
)?;
if state.derive_type != DeriveType::Enum {
panic!("Only enums can derive TryInto");
}
let mut variants_per_types = HashMap::default();
for variant_state in state.enabled_variant_data().variant_states {
let multi_field_data = variant_state.enabled_fields_data();
let MultiFieldData {
variant_info,
field_types,
..
} = multi_field_data.clone();
for ref_type in variant_info.ref_types() {
variants_per_types
.entry((ref_type, field_types.clone()))
.or_insert_with(Vec::new)
.push(multi_field_data.clone());
}
}
let mut tokens = TokenStream::new();
for ((ref_type, ref original_types), ref multi_field_datas) in variants_per_types {
let input_type = &input.ident;
let pattern_ref = ref_type.pattern_ref();
let lifetime = ref_type.lifetime();
let reference_with_lifetime = ref_type.reference_with_lifetime();
let mut matchers = vec![];
let vars = &numbered_vars(original_types.len(), "");
for multi_field_data in multi_field_datas {
let patterns: Vec<_> =
vars.iter().map(|var| quote!(#pattern_ref #var)).collect();
matchers.push(
multi_field_data.matcher(&multi_field_data.field_indexes, &patterns),
);
}
let vars = if vars.len() == 1 {
quote!(#(#vars)*)
} else {
quote!((#(#vars),*))
};
let output_type = if original_types.len() == 1 {
format!("{}", quote!(#(#original_types)*))
} else {
let types = original_types
.iter()
.map(|t| format!("{}", quote!(#t)))
.collect::<Vec<_>>();
format!("({})", types.join(", "))
};
let variant_names = multi_field_datas
.iter()
.map(|d| {
format!(
"{}",
d.variant_name.expect("Somehow there was no variant name")
)
})
.collect::<Vec<_>>()
.join(", ");
let message =
format!("Only {} can be converted to {}", variant_names, output_type);
let generics_impl;
let (_, ty_generics, where_clause) = input.generics.split_for_impl();
let (impl_generics, _, _) = if ref_type.is_ref() {
generics_impl = add_extra_generic_param(&input.generics, lifetime.clone());
generics_impl.split_for_impl()
} else {
input.generics.split_for_impl()
};
let try_from = quote! {
impl#impl_generics ::core::convert::TryFrom<#reference_with_lifetime #input_type#ty_generics> for
(#(#reference_with_lifetime #original_types),*) #where_clause {
type Error = &'static str;
#[allow(unused_variables)]
#[inline]
fn try_from(value: #reference_with_lifetime #input_type#ty_generics) -> ::core::result::Result<Self, Self::Error> {
match value {
#(#matchers)|* => ::core::result::Result::Ok(#vars),
_ => ::core::result::Result::Err(#message),
}
}
}
};
try_from.to_tokens(&mut tokens)
}
Ok(tokens)
}