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
|
use proc_macro::{Delimiter, Literal, Span, TokenStream, TokenTree};
use crate::{
iter::TokenIter,
to_tokens::ToTokens,
utils::{parse_as_empty, tt_span},
Result,
};
pub(crate) struct Func {
pub(crate) attrs: Vec<Attribute>,
pub(crate) sig: Vec<TokenTree>,
pub(crate) body: TokenTree,
pub(crate) print_const: bool,
}
pub(crate) fn parse_input(input: TokenStream) -> Result<Func> {
let mut input = TokenIter::new(input);
let attrs = parse_attrs(&mut input)?;
let sig = parse_signature(&mut input);
let body = input.next();
parse_as_empty(input)?;
if body.is_none()
|| !sig
.iter()
.any(|tt| if let TokenTree::Ident(i) = tt { i.to_string() == "fn" } else { false })
{
return Err(error!(
Span::call_site(),
"#[const_fn] attribute may only be used on functions"
));
}
if !sig
.iter()
.any(|tt| if let TokenTree::Ident(i) = tt { i.to_string() == "const" } else { false })
{
let span = sig
.iter()
.position(|tt| if let TokenTree::Ident(i) = tt { i.to_string() == "fn" } else { false })
.map(|i| sig[i].span())
.unwrap();
return Err(error!(span, "#[const_fn] attribute may only be used on const functions"));
}
Ok(Func { attrs, sig, body: body.unwrap(), print_const: true })
}
impl ToTokens for Func {
fn to_tokens(&self, tokens: &mut TokenStream) {
self.attrs.iter().for_each(|attr| attr.to_tokens(tokens));
if self.print_const {
self.sig.iter().for_each(|attr| attr.to_tokens(tokens));
} else {
self.sig
.iter()
.filter(
|tt| if let TokenTree::Ident(i) = tt { i.to_string() != "const" } else { true },
)
.for_each(|tt| tt.to_tokens(tokens));
}
self.body.to_tokens(tokens);
}
}
fn parse_signature(input: &mut TokenIter) -> Vec<TokenTree> {
let mut sig = Vec::new();
loop {
match input.peek() {
Some(TokenTree::Group(group)) if group.delimiter() == Delimiter::Brace => break,
None => break,
Some(_) => sig.push(input.next().unwrap()),
}
}
sig
}
fn parse_attrs(input: &mut TokenIter) -> Result<Vec<Attribute>> {
let mut attrs = Vec::new();
loop {
let pound_token = match input.peek() {
Some(TokenTree::Punct(p)) if p.as_char() == '#' => input.next().unwrap(),
_ => break,
};
let group = match input.peek() {
Some(TokenTree::Group(g)) if g.delimiter() == Delimiter::Bracket => {
input.next().unwrap()
}
tt => return Err(error!(tt_span(tt), "expected `[`")),
};
attrs.push(Attribute { pound_token, group });
}
Ok(attrs)
}
pub(crate) struct Attribute {
// `#`
pub(crate) pound_token: TokenTree,
// `[...]`
pub(crate) group: TokenTree,
}
impl ToTokens for Attribute {
fn to_tokens(&self, tokens: &mut TokenStream) {
self.pound_token.to_tokens(tokens);
self.group.to_tokens(tokens);
}
}
pub(crate) struct LitStr {
pub(crate) token: Literal,
value: String,
}
impl LitStr {
pub(crate) fn new(token: Literal) -> Result<Self> {
let value = token.to_string();
// unlike `syn::LitStr`, only accepts `"..."`
if value.starts_with('"') && value.ends_with('"') {
Ok(Self { token, value })
} else {
Err(error!(token.span(), "expected string literal"))
}
}
pub(crate) fn value(&self) -> &str {
&self.value[1..self.value.len() - 1]
}
pub(crate) fn span(&self) -> Span {
self.token.span()
}
}
impl ToTokens for LitStr {
fn to_tokens(&self, tokens: &mut TokenStream) {
self.token.to_tokens(tokens);
}
}
|
