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
|
use heck::ToShoutySnakeCase;
use proc_macro2::{Span, TokenStream};
use quote::{format_ident, quote};
use syn::{Data, DeriveInput, Fields, PathArguments, Type, TypeParen};
use crate::helpers::{non_enum_error, HasStrumVariantProperties};
pub fn from_repr_inner(ast: &DeriveInput) -> syn::Result<TokenStream> {
let name = &ast.ident;
let gen = &ast.generics;
let (impl_generics, ty_generics, where_clause) = gen.split_for_impl();
let vis = &ast.vis;
let attrs = &ast.attrs;
let mut discriminant_type: Type = syn::parse("usize".parse().unwrap()).unwrap();
for attr in attrs {
let path = &attr.path;
let tokens = &attr.tokens;
if path.leading_colon.is_some() {
continue;
}
if path.segments.len() != 1 {
continue;
}
let segment = path.segments.first().unwrap();
if segment.ident != "repr" {
continue;
}
if segment.arguments != PathArguments::None {
continue;
}
let typ_paren = match syn::parse2::<Type>(tokens.clone()) {
Ok(Type::Paren(TypeParen { elem, .. })) => *elem,
_ => continue,
};
let inner_path = match &typ_paren {
Type::Path(t) => t,
_ => continue,
};
if let Some(seg) = inner_path.path.segments.last() {
for t in &[
"u8", "u16", "u32", "u64", "usize", "i8", "i16", "i32", "i64", "isize",
] {
if seg.ident == t {
discriminant_type = typ_paren;
break;
}
}
}
}
if gen.lifetimes().count() > 0 {
return Err(syn::Error::new(
Span::call_site(),
"This macro doesn't support enums with lifetimes. \
The resulting enums would be unbounded.",
));
}
let variants = match &ast.data {
Data::Enum(v) => &v.variants,
_ => return Err(non_enum_error()),
};
let mut arms = Vec::new();
let mut constant_defs = Vec::new();
let mut has_additional_data = false;
let mut prev_const_var_ident = None;
for variant in variants {
if variant.get_variant_properties()?.disabled.is_some() {
continue;
}
let ident = &variant.ident;
let params = match &variant.fields {
Fields::Unit => quote! {},
Fields::Unnamed(fields) => {
has_additional_data = true;
let defaults = ::core::iter::repeat(quote!(::core::default::Default::default()))
.take(fields.unnamed.len());
quote! { (#(#defaults),*) }
}
Fields::Named(fields) => {
has_additional_data = true;
let fields = fields
.named
.iter()
.map(|field| field.ident.as_ref().unwrap());
quote! { {#(#fields: ::core::default::Default::default()),*} }
}
};
let const_var_str = format!("{}_DISCRIMINANT", variant.ident).to_shouty_snake_case();
let const_var_ident = format_ident!("{}", const_var_str);
let const_val_expr = match &variant.discriminant {
Some((_, expr)) => quote! { #expr },
None => match &prev_const_var_ident {
Some(prev) => quote! { #prev + 1 },
None => quote! { 0 },
},
};
constant_defs.push(quote! {const #const_var_ident: #discriminant_type = #const_val_expr;});
arms.push(quote! {v if v == #const_var_ident => ::core::option::Option::Some(#name::#ident #params)});
prev_const_var_ident = Some(const_var_ident);
}
arms.push(quote! { _ => ::core::option::Option::None });
let const_if_possible = if has_additional_data {
quote! {}
} else {
#[rustversion::before(1.46)]
fn filter_by_rust_version(_: TokenStream) -> TokenStream {
quote! {}
}
#[rustversion::since(1.46)]
fn filter_by_rust_version(s: TokenStream) -> TokenStream {
s
}
filter_by_rust_version(quote! { const })
};
Ok(quote! {
#[allow(clippy::use_self)]
impl #impl_generics #name #ty_generics #where_clause {
#[doc = "Try to create [Self] from the raw representation"]
#vis #const_if_possible fn from_repr(discriminant: #discriminant_type) -> Option<#name #ty_generics> {
#(#constant_defs)*
match discriminant {
#(#arms),*
}
}
}
})
}
|
