zyn_core/ast/
group_node.rs

1use proc_macro2::Delimiter;
2use proc_macro2::Ident;
3use proc_macro2::Span;
4use proc_macro2::TokenStream;
5
6use quote::quote;
7
8use syn::parse::Parse;
9use syn::parse::ParseStream;
10
11use crate::template::Template;
12
13use crate::Expand;
14
15/// A delimited group in a zyn template: `(...)`, `[...]`, or `{...}`.
16///
17/// The body is expanded recursively and wrapped in the appropriate delimiter.
18pub struct GroupNode {
19    /// Source span.
20    pub span: Span,
21    /// The delimiter kind: parenthesis, bracket, or brace.
22    pub delimiter: Delimiter,
23    /// The template body inside the delimiters.
24    pub body: Box<Template>,
25}
26
27impl GroupNode {
28    pub fn span(&self) -> Span {
29        self.span
30    }
31}
32
33impl Parse for GroupNode {
34    fn parse(input: ParseStream) -> syn::Result<Self> {
35        if input.peek(syn::token::Paren) {
36            let content;
37            let paren = syn::parenthesized!(content in input);
38            let body = content.parse::<Template>()?;
39
40            Ok(Self {
41                span: paren.span.join(),
42                delimiter: Delimiter::Parenthesis,
43                body: Box::new(body),
44            })
45        } else if input.peek(syn::token::Bracket) {
46            let content;
47            let bracket = syn::bracketed!(content in input);
48            let body = content.parse::<Template>()?;
49
50            Ok(Self {
51                span: bracket.span.join(),
52                delimiter: Delimiter::Bracket,
53                body: Box::new(body),
54            })
55        } else {
56            Err(input.error("expected a delimited group"))
57        }
58    }
59}
60
61impl Expand for GroupNode {
62    fn expand(&self, output: &Ident, idents: &mut crate::ident::Iter) -> TokenStream {
63        let inner = idents.next().unwrap();
64        let body_expanded = self.body.expand(&inner, idents);
65
66        let delim = match self.delimiter {
67            Delimiter::Parenthesis => {
68                quote! { ::zyn::proc_macro2::Delimiter::Parenthesis }
69            }
70            Delimiter::Bracket => quote! { ::zyn::proc_macro2::Delimiter::Bracket },
71            Delimiter::Brace => quote! { ::zyn::proc_macro2::Delimiter::Brace },
72            Delimiter::None => quote! { ::zyn::proc_macro2::Delimiter::None },
73        };
74
75        quote! {
76            {
77                let mut #inner = ::zyn::proc_macro2::TokenStream::new();
78                #body_expanded
79                ::zyn::quote::ToTokens::to_tokens(
80                    &::zyn::proc_macro2::Group::new(#delim, #inner),
81                    &mut #output,
82                );
83            }
84        }
85    }
86}
zyn_core/ast/group_node.rs

zyn_core/ast/
group_node.rs
