token_parser_derive/
lib.rs

1#![deny(missing_docs)]
2
3/*!
4Derive macros for the token parser.
5**/
6
7use quote::quote;
8use syn::{
9    parse_macro_input, parse_quote, Data, DeriveInput, Fields, GenericParam, Generics,
10    TypeParamBound,
11};
12
13#[proc_macro_derive(Parsable)]
14/// Derive the `Parsable` trait by parsing all unnamed fields in order using the `Parsable` trait.
15pub fn derive_default_parsable(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
16    derive_parsable(input, false)
17}
18
19#[proc_macro_derive(SymbolParsable)]
20/// Derive the `Parsable` trait by parsing all unnamed fields using the `FromStr` trait.
21pub fn derive_symbol_parsable(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
22    derive_parsable(input, true)
23}
24
25fn add_trait_bounds(mut generics: Generics, bound: TypeParamBound) -> Generics {
26    for param in &mut generics.params {
27        if let GenericParam::Type(ref mut type_param) = *param {
28            type_param.bounds.push(bound.clone());
29        }
30    }
31    generics
32}
33
34fn derive_parsable(input: proc_macro::TokenStream, symbol: bool) -> proc_macro::TokenStream {
35    let input = parse_macro_input!(input as DeriveInput);
36    let name = input.ident;
37
38    let trait_bound = if symbol {
39        parse_quote!(std::str::FromStr)
40    } else {
41        parse_quote!(token_parser::Parsable)
42    };
43
44    let generics = add_trait_bounds(input.generics.clone(), trait_bound);
45    let (_, ty_generics, where_clause) = generics.split_for_impl();
46    let mut generics = input.generics;
47    generics.params.push(parse_quote!(C));
48    let (impl_generics, _, _) = generics.split_for_impl();
49
50    if let Data::Struct(data) = input.data {
51        if let Fields::Unnamed(fields) = data.fields {
52            let expression = if symbol {
53                quote! {
54                    if let Ok(result) = name.parse() {
55                        result
56                    } else {
57                        return Err(token_parser::Error::StringParsing)
58                    }
59                }
60            } else {
61                quote!(parser.parse_next(context)?)
62            };
63
64            let expressions = fields.unnamed.into_iter().map(|_| &expression);
65
66            let method = if symbol {
67                quote! {
68                    fn parse_symbol(name: String, context: &C) -> token_parser::Result<Self>
69                }
70            } else {
71                quote! {
72                    fn parse_list(parser: &mut token_parser::Parser, context: &C) -> token_parser::Result<Self>
73                }
74            };
75
76            let expanded = quote! {
77                impl #impl_generics token_parser::Parsable<C> for #name #ty_generics #where_clause {
78                    #method
79                    {
80                        Ok(#name(#( #expressions, )*))
81                    }
82                }
83            };
84
85            proc_macro::TokenStream::from(expanded)
86        } else {
87            panic!("Deriving parser is only available for tuple structs")
88        }
89    } else {
90        panic!("Deriving parser is only available for structs")
91    }
92}
token_parser_derive/lib.rs

token_parser_derive/
lib.rs
