1use proc_macro::{token_stream, Group, TokenStream, TokenTree};
4
5pub(crate) fn try_ident(it: &mut token_stream::IntoIter) -> Option<String> {
6    if let Some(TokenTree::Ident(ident)) = it.next() {
7        Some(ident.to_string())
8    } else {
9        None
10    }
11}
12
13pub(crate) fn try_literal(it: &mut token_stream::IntoIter) -> Option<String> {
14    if let Some(TokenTree::Literal(literal)) = it.next() {
15        Some(literal.to_string())
16    } else {
17        None
18    }
19}
20
21pub(crate) fn try_string(it: &mut token_stream::IntoIter) -> Option<String> {
22    try_literal(it).and_then(|string| {
23        if string.starts_with('\"') && string.ends_with('\"') {
24            let content = &string[1..string.len() - 1];
25            if content.contains('\\') {
26                panic!("Escape sequences in string literals not yet handled");
27            }
28            Some(content.to_string())
29        } else if string.starts_with("r\"") {
30            panic!("Raw string literals are not yet handled");
31        } else {
32            None
33        }
34    })
35}
36
37pub(crate) fn expect_ident(it: &mut token_stream::IntoIter) -> String {
38    try_ident(it).expect("Expected Ident")
39}
40
41pub(crate) fn expect_punct(it: &mut token_stream::IntoIter) -> char {
42    if let TokenTree::Punct(punct) = it.next().expect("Reached end of token stream for Punct") {
43        punct.as_char()
44    } else {
45        panic!("Expected Punct");
46    }
47}
48
49pub(crate) fn expect_string(it: &mut token_stream::IntoIter) -> String {
50    try_string(it).expect("Expected string")
51}
52
53pub(crate) fn expect_string_ascii(it: &mut token_stream::IntoIter) -> String {
54    let string = try_string(it).expect("Expected string");
55    assert!(string.is_ascii(), "Expected ASCII string");
56    string
57}
58
59pub(crate) fn expect_group(it: &mut token_stream::IntoIter) -> Group {
60    if let TokenTree::Group(group) = it.next().expect("Reached end of token stream for Group") {
61        group
62    } else {
63        panic!("Expected Group");
64    }
65}
66
67pub(crate) fn expect_end(it: &mut token_stream::IntoIter) {
68    if it.next().is_some() {
69        panic!("Expected end");
70    }
71}
72
73pub(crate) struct Generics {
95    pub(crate) decl_generics: Vec<TokenTree>,
99    pub(crate) impl_generics: Vec<TokenTree>,
103    pub(crate) ty_generics: Vec<TokenTree>,
108}
109
110pub(crate) fn parse_generics(input: TokenStream) -> (Generics, Vec<TokenTree>) {
114    let mut decl_generics = vec![];
116    let mut impl_generics = vec![];
118    let mut ty_generics = vec![];
120    let mut rest = vec![];
122    let mut nesting = 0;
124    let mut toks = input.into_iter();
125    let mut at_start = true;
127    let mut skip_until_comma = false;
128    while let Some(tt) = toks.next() {
129        if nesting == 1 && matches!(&tt, TokenTree::Punct(p) if p.as_char() == '>') {
130            break;
132        } else if nesting >= 1 {
133            decl_generics.push(tt.clone());
134        }
135        match tt.clone() {
136            TokenTree::Punct(p) if p.as_char() == '<' => {
137                if nesting >= 1 && !skip_until_comma {
138                    impl_generics.push(tt);
140                }
141                nesting += 1;
142            }
143            TokenTree::Punct(p) if p.as_char() == '>' => {
144                if nesting == 0 {
146                    break;
147                } else {
148                    nesting -= 1;
149                    if nesting >= 1 && !skip_until_comma {
150                        impl_generics.push(tt);
152                    }
153                }
154            }
155            TokenTree::Punct(p) if skip_until_comma && p.as_char() == ',' => {
156                if nesting == 1 {
157                    impl_generics.push(tt.clone());
158                    impl_generics.push(tt);
159                    skip_until_comma = false;
160                }
161            }
162            _ if !skip_until_comma => {
163                match nesting {
164                    0 => rest.push(tt),
166                    1 => {
167                        match tt.clone() {
169                            TokenTree::Ident(i) if at_start && i.to_string() == "const" => {
170                                let Some(name) = toks.next() else {
171                                    break;
173                                };
174                                impl_generics.push(tt);
175                                impl_generics.push(name.clone());
176                                ty_generics.push(name.clone());
177                                decl_generics.push(name);
178                                at_start = false;
179                            }
180                            TokenTree::Ident(_) if at_start => {
181                                impl_generics.push(tt.clone());
182                                ty_generics.push(tt);
183                                at_start = false;
184                            }
185                            TokenTree::Punct(p) if p.as_char() == ',' => {
186                                impl_generics.push(tt.clone());
187                                ty_generics.push(tt);
188                                at_start = true;
189                            }
190                            TokenTree::Punct(p) if p.as_char() == '\'' && at_start => {
192                                impl_generics.push(tt.clone());
193                                ty_generics.push(tt);
194                            }
195                            TokenTree::Punct(p) if p.as_char() == '=' => {
197                                skip_until_comma = true;
198                            }
199                            _ => impl_generics.push(tt),
200                        }
201                    }
202                    _ => impl_generics.push(tt),
203                }
204            }
205            _ => {}
206        }
207    }
208    rest.extend(toks);
209    (
210        Generics {
211            impl_generics,
212            decl_generics,
213            ty_generics,
214        },
215        rest,
216    )
217}