1 // SPDX-License-Identifier: GPL-2.0
2
3 use proc_macro::{Delimiter, Group, TokenStream
4 use std::collections::HashSet;
5 use std::fmt::Write;
6
7 pub(crate) fn vtable(_attr: TokenStream, ts: T
8 let mut tokens: Vec<_> = ts.into_iter().co
9
10 // Scan for the `trait` or `impl` keyword.
11 let is_trait = tokens
12 .iter()
13 .find_map(|token| match token {
14 TokenTree::Ident(ident) => match i
15 "trait" => Some(true),
16 "impl" => Some(false),
17 _ => None,
18 },
19 _ => None,
20 })
21 .expect("#[vtable] attribute should on
22
23 // Retrieve the main body. The main body s
24 let body = match tokens.pop() {
25 Some(TokenTree::Group(group)) if group
26 _ => panic!("cannot locate main body o
27 };
28
29 let mut body_it = body.stream().into_iter(
30 let mut functions = Vec::new();
31 let mut consts = HashSet::new();
32 while let Some(token) = body_it.next() {
33 match token {
34 TokenTree::Ident(ident) if ident.t
35 let fn_name = match body_it.ne
36 Some(TokenTree::Ident(iden
37 // Possibly we've encounte
38 _ => continue,
39 };
40 functions.push(fn_name);
41 }
42 TokenTree::Ident(ident) if ident.t
43 let const_name = match body_it
44 Some(TokenTree::Ident(iden
45 // Possibly we've encounte
46 _ => continue,
47 };
48 consts.insert(const_name);
49 }
50 _ => (),
51 }
52 }
53
54 let mut const_items;
55 if is_trait {
56 const_items = "
57 /// A marker to prevent implem
58 /// attribute when implementin
59 const USE_VTABLE_ATTR: ();
60 "
61 .to_owned();
62
63 for f in functions {
64 let gen_const_name = format!("HAS_
65 // Skip if it's declared already -
66 if consts.contains(&gen_const_name
67 continue;
68 }
69 // We don't know on the implementa
70 // so we have to generate a const
71 write!(
72 const_items,
73 "/// Indicates if the `{f}` me
74 const {gen_const_name}: bool =
75 )
76 .unwrap();
77 consts.insert(gen_const_name);
78 }
79 } else {
80 const_items = "const USE_VTABLE_ATTR:
81
82 for f in functions {
83 let gen_const_name = format!("HAS_
84 if consts.contains(&gen_const_name
85 continue;
86 }
87 write!(const_items, "const {gen_co
88 }
89 }
90
91 let new_body = vec![const_items.parse().un
92 .into_iter()
93 .collect();
94 tokens.push(TokenTree::Group(Group::new(De
95 tokens.into_iter().collect()
96 }
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