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
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
#![feature(proc_macro_hygiene)]
extern crate proc_macro;
extern crate proc_macro2;
mod resyn;
use proc_macro::TokenStream;
use quote::quote;
use syn;
#[proc_macro]
pub fn named_return(item: TokenStream) -> TokenStream {
let input = syn::parse_macro_input!(item as resyn::item_fn::ItemFn);
let vis = &input.vis;
let constness = &input.constness;
let unsafety = &input.unsafety;
let ident = &input.ident;
let decl = &input.decl;
let block = &input.block;
let generics = &decl.generics;
let inputs = &decl.inputs;
let _output = &decl.output;
let output_simple: syn::ReturnType = decl.output.clone().into();
type Cp<T> = syn::punctuated::Punctuated<T, syn::token::Comma>;
use resyn::item_fn::fn_decl::return_type::Captures;
let captures: Option<Captures> = decl.output.clone().into();
let (cap_names, cap_types): (Option<Cp<syn::Pat>>, Option<Cp<syn::Type>>) = match captures {
Some(ref caps) => {
use syn::punctuated::Pair;
let (names, types) = caps
.iter()
.map(|arg_cap| {
let name = Pair::new(
arg_cap.pat.clone(),
Some(syn::token::Comma {
spans: arg_cap.colon_token.spans,
}),
);
let ty = Pair::new(
arg_cap.ty.clone(),
Some(syn::token::Comma {
spans: arg_cap.colon_token.spans,
}),
);
(name, ty)
})
.unzip();
(Some(names), Some(types))
}
None => (None, None),
};
let block_prefix = if captures.is_some() {
Some(quote!(let (#cap_names) : (#cap_types) ;))
} else {
None
};
let new_block = if block_prefix.is_some() {
quote!({
#block_prefix
#block
})
} else {
quote!(#block)
};
let reparsed = quote! {
#vis #constness #unsafety fn #ident #generics ( #inputs ) #output_simple #new_block
};
let tokens = quote! {
#reparsed
};
tokens.into()
}
#[proc_macro_attribute]
pub fn named_return_attr(_attr: TokenStream, item: TokenStream) -> TokenStream {
named_return(item)
}