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
extern crate proc_macro;
use proc_macro::TokenStream;
use proc_macro2::TokenStream as TokenStream2;
use quote::{format_ident, quote};
use syn::{parse_macro_input, Fields, Item, Variant};
#[proc_macro_derive(DigEnum)]
pub fn digenum(input: TokenStream) -> TokenStream {
let input = parse_macro_input!(input as Item);
let num = if let Item::Enum(num) = input {
num
} else {
panic!("struct isn't enum")
};
let name = num.ident;
let (impl_gen, ty_gen, where_gen) = num.generics.split_for_impl();
let defs = num.variants.iter().map(gen_fns);
let expanded = quote! {
impl #impl_gen #name #ty_gen #where_gen {
#(#defs)*
}
};
TokenStream::from(expanded)
}
fn gen_fns(v: &Variant) -> TokenStream2 {
let name = &v.ident;
let fields = &v.fields;
let as_name = format_ident!("as_{name}");
let as_mut_name = format_ident!("as_mut_{name}");
let into_name = format_ident!("into_{name}");
if let Fields::Unit = fields {
return TokenStream2::new();
}
let fields = fields.iter().collect::<Vec<_>>();
let first = fields[0];
let entries = (0..fields.len())
.map(|x| format_ident!("_{x}"))
.collect::<Vec<_>>();
let ref_fields = if fields.len() == 1 {
quote! { &#first }
} else {
quote! { (#(&#fields), *) }
};
let mut_fields = if fields.len() == 1 {
quote! { &mut #first }
} else {
quote! { (#(&mut #fields), *) }
};
let fields = if fields.len() == 1 {
quote! { #first }
} else {
quote! { (#(#fields), *) }
};
quote! {
#[allow(non_snake_case)]
pub fn #as_name(&self) -> Option<#ref_fields> {
match self {
Self::#name(#(#entries), *) => Some((#(#entries), *)),
_ => None
}
}
#[allow(non_snake_case)]
pub fn #as_mut_name(&mut self) -> Option<#mut_fields> {
match self {
Self::#name(#(#entries), *) => Some((#(#entries), *)),
_ => None
}
}
#[allow(non_snake_case)]
pub fn #into_name(self) -> Option<#fields> {
match self {
Self::#name(#(#entries), *) => Some((#(#entries), *)),
_ => None
}
}
}
}
#[cfg(test)]
pub mod test;