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
|
use std::collections::HashMap;
use proc_macro2::{Group, TokenStream};
use quote::quote;
use syn::{parenthesized, parse::Parse, Attribute, Error, Ident, LitInt, Token};
struct Collection {
pub id: Ident,
pub count: usize,
}
impl Parse for Collection {
fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
let inner;
parenthesized!(inner in input);
let id: Ident = inner.parse()?;
let _: Token![,] = inner.parse()?;
let count_lit: LitInt = inner.parse()?;
let count: usize = count_lit.base10_parse()?;
if count < 1 {
return Err(Error::new(
count_lit.span(),
"number of type parameters must be >= 1",
));
}
Ok(Self { id, count })
}
}
#[derive(Default)]
pub struct TraitAttrs {
pub blanket_impl_attrs: Vec<TokenStream>,
pub dyn_trait_attrs: Vec<TokenStream>,
pub collections: HashMap<Ident, usize>,
}
impl TraitAttrs {
pub fn parse(attrs: &mut Vec<Attribute>) -> Result<Self, Error> {
let mut parsed = TraitAttrs::default();
// FUTURE: use Vec::drain_filter once it's stable
let mut i = 0;
while i < attrs.len() {
if attrs[i].path.is_ident("blanket_impl_attr") {
let attr = attrs.remove(i);
let group: Group = match syn::parse2(attr.tokens) {
Ok(g) => g,
Err(err) => {
return Err(Error::new(
err.span(),
"expected parenthesis: #[blanket_impl_attr(...)]",
))
}
};
let tokens = group.stream();
parsed.blanket_impl_attrs.push(quote! {#[#tokens]});
} else if attrs[i].path.is_ident("dyn_trait_attr") {
let attr = attrs.remove(i);
let group: Group = match syn::parse2(attr.tokens) {
Ok(g) => g,
Err(err) => {
return Err(Error::new(
err.span(),
"expected parenthesis: #[dyn_trait_attr(...)]",
))
}
};
let tokens = group.stream();
parsed.dyn_trait_attrs.push(quote! {#[#tokens]});
} else if attrs[i].path.is_ident("collection") {
let attr = attrs.remove(i);
let coll: Collection = syn::parse2(attr.tokens)?;
if parsed
.collections
.insert(coll.id.clone(), coll.count)
.is_some()
{
return Err(Error::new(
coll.id.span(),
format_args!(
"collection `{}` is defined multiple times for this trait",
coll.id
),
));
}
} else {
i += 1;
}
}
Ok(parsed)
}
}
|
