1 // SPDX-License-Identifier: GPL-2.0
2
3 use proc_macro::{token_stream, Group, TokenStream, TokenTree};
4
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
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
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
37 pub(crate) fn expect_ident(it: &mut token_stream::IntoIter) -> String {
38 try_ident(it).expect("Expected Ident")
39 }
40
41 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
49 pub(crate) fn expect_string(it: &mut token_stream::IntoIter) -> String {
50 try_string(it).expect("Expected string")
51 }
52
53 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
59 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
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 /// Parsed generics.
74 ///
75 /// See the field documentation for an explanation what each of the fields represents.
76 ///
77 /// # Examples
78 ///
79 /// ```rust,ignore
80 /// # let input = todo!();
81 /// let (Generics { decl_generics, impl_generics, ty_generics }, rest) = parse_generics(input);
82 /// quote! {
83 /// struct Foo<$($decl_generics)*> {
84 /// // ...
85 /// }
86 ///
87 /// impl<$impl_generics> Foo<$ty_generics> {
88 /// fn foo() {
89 /// // ...
90 /// }
91 /// }
92 /// }
93 /// ```
94 pub(crate) struct Generics {
95 /// The generics with bounds and default values (e.g. `T: Clone, const N: usize = 0`).
96 ///
97 /// Use this on type definitions e.g. `struct Foo<$decl_generics> ...` (or `union`/`enum`).
98 pub(crate) decl_generics: Vec<TokenTree>,
99 /// The generics with bounds (e.g. `T: Clone, const N: usize`).
100 ///
101 /// Use this on `impl` blocks e.g. `impl<$impl_generics> Trait for ...`.
102 pub(crate) impl_generics: Vec<TokenTree>,
103 /// The generics without bounds and without default values (e.g. `T, N`).
104 ///
105 /// Use this when you use the type that is declared with these generics e.g.
106 /// `Foo<$ty_generics>`.
107 pub(crate) ty_generics: Vec<TokenTree>,
108 }
109
110 /// Parses the given `TokenStream` into `Generics` and the rest.
111 ///
112 /// The generics are not present in the rest, but a where clause might remain.
113 pub(crate) fn parse_generics(input: TokenStream) -> (Generics, Vec<TokenTree>) {
114 // The generics with bounds and default values.
115 let mut decl_generics = vec![];
116 // `impl_generics`, the declared generics with their bounds.
117 let mut impl_generics = vec![];
118 // Only the names of the generics, without any bounds.
119 let mut ty_generics = vec![];
120 // Tokens not related to the generics e.g. the `where` token and definition.
121 let mut rest = vec![];
122 // The current level of `<`.
123 let mut nesting = 0;
124 let mut toks = input.into_iter();
125 // If we are at the beginning of a generic parameter.
126 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 // Found the end of the generics.
131 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 // This is inside of the generics and part of some bound.
139 impl_generics.push(tt);
140 }
141 nesting += 1;
142 }
143 TokenTree::Punct(p) if p.as_char() == '>' => {
144 // This is a parsing error, so we just end it here.
145 if nesting == 0 {
146 break;
147 } else {
148 nesting -= 1;
149 if nesting >= 1 && !skip_until_comma {
150 // We are still inside of the generics and part of some bound.
151 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 // If we haven't entered the generics yet, we still want to keep these tokens.
165 0 => rest.push(tt),
166 1 => {
167 // Here depending on the token, it might be a generic variable name.
168 match tt.clone() {
169 TokenTree::Ident(i) if at_start && i.to_string() == "const" => {
170 let Some(name) = toks.next() else {
171 // Parsing error.
172 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 // Lifetimes begin with `'`.
191 TokenTree::Punct(p) if p.as_char() == '\'' && at_start => {
192 impl_generics.push(tt.clone());
193 ty_generics.push(tt);
194 }
195 // Generics can have default values, we skip these.
196 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 }
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