syn/group.rs
1use proc_macro2::{Delimiter, Span};
2
3use crate::error::Result;
4use crate::parse::ParseBuffer;
5use crate::token;
6
7// Not public API.
8#[doc(hidden)]
9pub struct Parens<'a> {
10 pub token: token::Paren,
11 pub content: ParseBuffer<'a>,
12}
13
14// Not public API.
15#[doc(hidden)]
16pub struct Braces<'a> {
17 pub token: token::Brace,
18 pub content: ParseBuffer<'a>,
19}
20
21// Not public API.
22#[doc(hidden)]
23pub struct Brackets<'a> {
24 pub token: token::Bracket,
25 pub content: ParseBuffer<'a>,
26}
27
28// Not public API.
29#[cfg(any(feature = "full", feature = "derive"))]
30#[doc(hidden)]
31pub struct Group<'a> {
32 pub token: token::Group,
33 pub content: ParseBuffer<'a>,
34}
35
36// Not public API.
37#[doc(hidden)]
38pub fn parse_parens<'a>(input: &ParseBuffer<'a>) -> Result<Parens<'a>> {
39 parse_delimited(input, Delimiter::Parenthesis).map(|(span, content)| Parens {
40 token: token::Paren(span),
41 content,
42 })
43}
44
45// Not public API.
46#[doc(hidden)]
47pub fn parse_braces<'a>(input: &ParseBuffer<'a>) -> Result<Braces<'a>> {
48 parse_delimited(input, Delimiter::Brace).map(|(span, content)| Braces {
49 token: token::Brace(span),
50 content,
51 })
52}
53
54// Not public API.
55#[doc(hidden)]
56pub fn parse_brackets<'a>(input: &ParseBuffer<'a>) -> Result<Brackets<'a>> {
57 parse_delimited(input, Delimiter::Bracket).map(|(span, content)| Brackets {
58 token: token::Bracket(span),
59 content,
60 })
61}
62
63#[cfg(any(feature = "full", feature = "derive"))]
64pub(crate) fn parse_group<'a>(input: &ParseBuffer<'a>) -> Result<Group<'a>> {
65 parse_delimited(input, Delimiter::None).map(|(span, content)| Group {
66 token: token::Group(span),
67 content,
68 })
69}
70
71fn parse_delimited<'a>(
72 input: &ParseBuffer<'a>,
73 delimiter: Delimiter,
74) -> Result<(Span, ParseBuffer<'a>)> {
75 input.step(|cursor| {
76 if let Some((content, span, rest)) = cursor.group(delimiter) {
77 let scope = crate::buffer::close_span_of_group(*cursor);
78 let nested = crate::parse::advance_step_cursor(cursor, content);
79 let unexpected = crate::parse::get_unexpected(input);
80 let content = crate::parse::new_parse_buffer(scope, nested, unexpected);
81 Ok(((span, content), rest))
82 } else {
83 let message = match delimiter {
84 Delimiter::Parenthesis => "expected parentheses",
85 Delimiter::Brace => "expected curly braces",
86 Delimiter::Bracket => "expected square brackets",
87 Delimiter::None => "expected invisible group",
88 };
89 Err(cursor.error(message))
90 }
91 })
92}
93
94/// Parse a set of parentheses and expose their content to subsequent parsers.
95///
96/// # Example
97///
98/// ```
99/// # use quote::quote;
100/// #
101/// use syn::{parenthesized, token, Ident, Result, Token, Type};
102/// use syn::parse::{Parse, ParseStream};
103/// use syn::punctuated::Punctuated;
104///
105/// // Parse a simplified tuple struct syntax like:
106/// //
107/// // struct S(A, B);
108/// struct TupleStruct {
109/// struct_token: Token![struct],
110/// ident: Ident,
111/// paren_token: token::Paren,
112/// fields: Punctuated<Type, Token![,]>,
113/// semi_token: Token![;],
114/// }
115///
116/// impl Parse for TupleStruct {
117/// fn parse(input: ParseStream) -> Result<Self> {
118/// let content;
119/// Ok(TupleStruct {
120/// struct_token: input.parse()?,
121/// ident: input.parse()?,
122/// paren_token: parenthesized!(content in input),
123/// fields: content.parse_terminated(Type::parse)?,
124/// semi_token: input.parse()?,
125/// })
126/// }
127/// }
128/// #
129/// # fn main() {
130/// # let input = quote! {
131/// # struct S(A, B);
132/// # };
133/// # syn::parse2::<TupleStruct>(input).unwrap();
134/// # }
135/// ```
136#[macro_export]
137macro_rules! parenthesized {
138 ($content:ident in $cursor:expr) => {
139 match $crate::group::parse_parens(&$cursor) {
140 $crate::export::Ok(parens) => {
141 $content = parens.content;
142 parens.token
143 }
144 $crate::export::Err(error) => {
145 return $crate::export::Err(error);
146 }
147 }
148 };
149}
150
151/// Parse a set of curly braces and expose their content to subsequent parsers.
152///
153/// # Example
154///
155/// ```
156/// # use quote::quote;
157/// #
158/// use syn::{braced, token, Ident, Result, Token, Type};
159/// use syn::parse::{Parse, ParseStream};
160/// use syn::punctuated::Punctuated;
161///
162/// // Parse a simplified struct syntax like:
163/// //
164/// // struct S {
165/// // a: A,
166/// // b: B,
167/// // }
168/// struct Struct {
169/// struct_token: Token![struct],
170/// ident: Ident,
171/// brace_token: token::Brace,
172/// fields: Punctuated<Field, Token![,]>,
173/// }
174///
175/// struct Field {
176/// name: Ident,
177/// colon_token: Token![:],
178/// ty: Type,
179/// }
180///
181/// impl Parse for Struct {
182/// fn parse(input: ParseStream) -> Result<Self> {
183/// let content;
184/// Ok(Struct {
185/// struct_token: input.parse()?,
186/// ident: input.parse()?,
187/// brace_token: braced!(content in input),
188/// fields: content.parse_terminated(Field::parse)?,
189/// })
190/// }
191/// }
192///
193/// impl Parse for Field {
194/// fn parse(input: ParseStream) -> Result<Self> {
195/// Ok(Field {
196/// name: input.parse()?,
197/// colon_token: input.parse()?,
198/// ty: input.parse()?,
199/// })
200/// }
201/// }
202/// #
203/// # fn main() {
204/// # let input = quote! {
205/// # struct S {
206/// # a: A,
207/// # b: B,
208/// # }
209/// # };
210/// # syn::parse2::<Struct>(input).unwrap();
211/// # }
212/// ```
213#[macro_export]
214macro_rules! braced {
215 ($content:ident in $cursor:expr) => {
216 match $crate::group::parse_braces(&$cursor) {
217 $crate::export::Ok(braces) => {
218 $content = braces.content;
219 braces.token
220 }
221 $crate::export::Err(error) => {
222 return $crate::export::Err(error);
223 }
224 }
225 };
226}
227
228/// Parse a set of square brackets and expose their content to subsequent
229/// parsers.
230///
231/// # Example
232///
233/// ```
234/// # use quote::quote;
235/// #
236/// use proc_macro2::TokenStream;
237/// use syn::{bracketed, token, Result, Token};
238/// use syn::parse::{Parse, ParseStream};
239///
240/// // Parse an outer attribute like:
241/// //
242/// // #[repr(C, packed)]
243/// struct OuterAttribute {
244/// pound_token: Token![#],
245/// bracket_token: token::Bracket,
246/// content: TokenStream,
247/// }
248///
249/// impl Parse for OuterAttribute {
250/// fn parse(input: ParseStream) -> Result<Self> {
251/// let content;
252/// Ok(OuterAttribute {
253/// pound_token: input.parse()?,
254/// bracket_token: bracketed!(content in input),
255/// content: content.parse()?,
256/// })
257/// }
258/// }
259/// #
260/// # fn main() {
261/// # let input = quote! {
262/// # #[repr(C, packed)]
263/// # };
264/// # syn::parse2::<OuterAttribute>(input).unwrap();
265/// # }
266/// ```
267#[macro_export]
268macro_rules! bracketed {
269 ($content:ident in $cursor:expr) => {
270 match $crate::group::parse_brackets(&$cursor) {
271 $crate::export::Ok(brackets) => {
272 $content = brackets.content;
273 brackets.token
274 }
275 $crate::export::Err(error) => {
276 return $crate::export::Err(error);
277 }
278 }
279 };
280}