1 // SPDX-License-Identifier: GPL-2.0
2
3 use proc_macro::{token_stream, Group, Punct, Spacing, TokenStream, TokenTree};
4
try_ident(it: &mut token_stream::IntoIter) -> Option<String>5 pub(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
try_literal(it: &mut token_stream::IntoIter) -> Option<String>13 pub(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
try_string(it: &mut token_stream::IntoIter) -> Option<String>21 pub(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
expect_ident(it: &mut token_stream::IntoIter) -> String37 pub(crate) fn expect_ident(it: &mut token_stream::IntoIter) -> String {
38 try_ident(it).expect("Expected Ident")
39 }
40
expect_punct(it: &mut token_stream::IntoIter) -> char41 pub(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
expect_string(it: &mut token_stream::IntoIter) -> String49 pub(crate) fn expect_string(it: &mut token_stream::IntoIter) -> String {
50 try_string(it).expect("Expected string")
51 }
52
expect_string_ascii(it: &mut token_stream::IntoIter) -> String53 pub(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
expect_group(it: &mut token_stream::IntoIter) -> Group59 pub(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
expect_end(it: &mut token_stream::IntoIter)67 pub(crate) fn expect_end(it: &mut token_stream::IntoIter) {
68 if it.next().is_some() {
69 panic!("Expected end");
70 }
71 }
72
73 pub(crate) struct Generics {
74 pub(crate) impl_generics: Vec<TokenTree>,
75 pub(crate) ty_generics: Vec<TokenTree>,
76 }
77
78 /// Parses the given `TokenStream` into `Generics` and the rest.
79 ///
80 /// The generics are not present in the rest, but a where clause might remain.
parse_generics(input: TokenStream) -> (Generics, Vec<TokenTree>)81 pub(crate) fn parse_generics(input: TokenStream) -> (Generics, Vec<TokenTree>) {
82 // `impl_generics`, the declared generics with their bounds.
83 let mut impl_generics = vec![];
84 // Only the names of the generics, without any bounds.
85 let mut ty_generics = vec![];
86 // Tokens not related to the generics e.g. the `where` token and definition.
87 let mut rest = vec![];
88 // The current level of `<`.
89 let mut nesting = 0;
90 let mut toks = input.into_iter();
91 // If we are at the beginning of a generic parameter.
92 let mut at_start = true;
93 for tt in &mut toks {
94 match tt.clone() {
95 TokenTree::Punct(p) if p.as_char() == '<' => {
96 if nesting >= 1 {
97 // This is inside of the generics and part of some bound.
98 impl_generics.push(tt);
99 }
100 nesting += 1;
101 }
102 TokenTree::Punct(p) if p.as_char() == '>' => {
103 // This is a parsing error, so we just end it here.
104 if nesting == 0 {
105 break;
106 } else {
107 nesting -= 1;
108 if nesting >= 1 {
109 // We are still inside of the generics and part of some bound.
110 impl_generics.push(tt);
111 }
112 if nesting == 0 {
113 break;
114 }
115 }
116 }
117 tt => {
118 if nesting == 1 {
119 // Here depending on the token, it might be a generic variable name.
120 match &tt {
121 // Ignore const.
122 TokenTree::Ident(i) if i.to_string() == "const" => {}
123 TokenTree::Ident(_) if at_start => {
124 ty_generics.push(tt.clone());
125 // We also already push the `,` token, this makes it easier to append
126 // generics.
127 ty_generics.push(TokenTree::Punct(Punct::new(',', Spacing::Alone)));
128 at_start = false;
129 }
130 TokenTree::Punct(p) if p.as_char() == ',' => at_start = true,
131 // Lifetimes begin with `'`.
132 TokenTree::Punct(p) if p.as_char() == '\'' && at_start => {
133 ty_generics.push(tt.clone());
134 }
135 _ => {}
136 }
137 }
138 if nesting >= 1 {
139 impl_generics.push(tt);
140 } else if nesting == 0 {
141 // If we haven't entered the generics yet, we still want to keep these tokens.
142 rest.push(tt);
143 }
144 }
145 }
146 }
147 rest.extend(toks);
148 (
149 Generics {
150 impl_generics,
151 ty_generics,
152 },
153 rest,
154 )
155 }
156