1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
#![recursion_limit = "256"]
extern crate proc_macro;
extern crate proc_macro2;
#[macro_use]
extern crate syn;
#[macro_use]
extern crate quote;

mod decl;
mod parser;

use decl::*;

use syn::parse::{Error, Parse, ParseStream, Result};
use syn::punctuated::Punctuated;
use syn::{token, Ident, LitInt, Type, Attribute};

#[doc(hidden)]
#[proc_macro]
pub fn pomelo_impl(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
    let Decls(decls) = parse_macro_input!(input);
    match pomelo_impl2(decls) {
        Ok(x) => x,
        Err(e) => e.to_compile_error().into(),
    }
}

fn pomelo_impl2(decls: Vec<Decl>) -> syn::Result<proc_macro::TokenStream> {
    let mut pomelo = parser::Pomelo::new_from_decls(decls)?;
    let expanded = pomelo.build()?;
    let name = pomelo.module_name();
    let x = quote! {
        mod #name {
            #expanded
        }
    };
    Ok(x.into())
}

struct Decls(Vec<Decl>);

impl Parse for Decls {
    fn parse(input: ParseStream) -> Result<Decls> {
        let mut decls = Vec::new();
        while !input.is_empty() {
            decls.push(input.parse()?);
        }
        Ok(Decls(decls))
    }
}

mod kw {
    custom_keyword!(module);
    custom_keyword!(include);
    custom_keyword!(syntax_error);
    custom_keyword!(parse_fail);
    custom_keyword!(stack_overflow);
    custom_keyword!(left);
    custom_keyword!(right);
    custom_keyword!(nonassoc);
    custom_keyword!(default_type);
    custom_keyword!(extra_argument);
    custom_keyword!(error);
    custom_keyword!(start_symbol);
    custom_keyword!(fallback);
    custom_keyword!(wildcard);
    custom_keyword!(token_class);
    custom_keyword!(token);
    custom_keyword!(verbose);
    custom_keyword!(extra_token);
    custom_keyword!(stack_size);
    custom_keyword!(parser);
}

impl Parse for Decl {
    fn parse(input: ParseStream) -> Result<Decl> {
        if input.peek(Token![%]) {
            input.parse::<Token![%]>()?;
            let lookahead = input.lookahead1();
            if lookahead.peek(Token![type]) {
                // %type ident type;
                input.parse::<Token![type]>()?;
                let attrs = input.call(Attribute::parse_outer)?;
                let ident = input.parse::<Ident>()?;
                let lookahead = input.lookahead1();
                let typ = if lookahead.peek(Token![;]) {
                    None
                } else {
                    Some(input.parse::<Type>()?)
                };
                input.parse::<Token![;]>()?;
                Ok(Decl::Type(attrs, ident, typ))
            } else if lookahead.peek(kw::module) {
                input.parse::<kw::module>()?;
                // %module ident;
                let ident = input.parse::<Ident>()?;
                input.parse::<Token![;]>()?;
                Ok(Decl::Module(ident))
            } else if lookahead.peek(kw::include) {
                // %include { rust-items } [;]
                input.parse::<kw::include>()?;
                let code;
                braced!(code in input);
                let mut items = Vec::new();
                while !code.is_empty() {
                    items.push(code.parse()?);
                }
                if input.peek(Token![;]) {
                    input.parse::<Token![;]>()?;
                }
                Ok(Decl::Include(items))
            } else if lookahead.peek(kw::syntax_error) {
                // %syntax_error { rust-block }
                input.parse::<kw::syntax_error>()?;
                let code = input.parse()?;
                if input.peek(Token![;]) {
                    input.parse::<Token![;]>()?;
                }
                Ok(Decl::SyntaxError(code))
            } else if lookahead.peek(kw::parse_fail) {
                // %parse_fail { rust-block }
                input.parse::<kw::parse_fail>()?;
                let code = input.parse()?;
                if input.peek(Token![;]) {
                    input.parse::<Token![;]>()?;
                }
                Ok(Decl::ParseFail(code))
            } else if lookahead.peek(kw::stack_overflow) {
                // %stack_overflow { rust-block }
                input.parse::<kw::stack_overflow>()?;
                let code = input.parse()?;
                if input.peek(Token![;]) {
                    input.parse::<Token![;]>()?;
                }
                Ok(Decl::StackOverflow(code))
            } else if lookahead.peek(kw::left) {
                // %left token1 token2 ... ;
                input.parse::<kw::left>()?;
                let mut toks = Vec::new();
                while !input.peek(Token![;]) {
                    toks.push(input.parse()?);
                }
                input.parse::<Token![;]>()?;
                Ok(Decl::Assoc(Associativity::Left, toks))
            } else if lookahead.peek(kw::right) {
                // %right token1 token2 ... ;
                input.parse::<kw::right>()?;
                let mut toks = Vec::new();
                while !input.peek(Token![;]) {
                    toks.push(input.parse()?);
                }
                input.parse::<Token![;]>()?;
                Ok(Decl::Assoc(Associativity::Right, toks))
            } else if lookahead.peek(kw::nonassoc) {
                // %nonassoc token1 token2 ... ;
                input.parse::<kw::nonassoc>()?;
                let mut toks = Vec::new();
                while !input.peek(Token![;]) {
                    toks.push(input.parse()?);
                }
                input.parse::<Token![;]>()?;
                Ok(Decl::Assoc(Associativity::None, toks))
            } else if lookahead.peek(kw::default_type) {
                // %default_type type;
                input.parse::<kw::default_type>()?;
                let typ = input.parse()?;
                input.parse::<Token![;]>()?;
                Ok(Decl::DefaultType(typ))
            } else if lookahead.peek(kw::extra_argument) {
                // %extra_argument type;
                input.parse::<kw::extra_argument>()?;
                let typ = input.parse()?;
                input.parse::<Token![;]>()?;
                Ok(Decl::ExtraArgument(typ))
            } else if lookahead.peek(kw::error) {
                // %error type;
                input.parse::<kw::error>()?;
                let typ = input.parse()?;
                input.parse::<Token![;]>()?;
                Ok(Decl::Error(typ))
            } else if lookahead.peek(kw::start_symbol) {
                // %start_symbol id;
                input.parse::<kw::start_symbol>()?;
                let id = input.parse()?;
                input.parse::<Token![;]>()?;
                Ok(Decl::StartSymbol(id))
            } else if lookahead.peek(kw::fallback) {
                // %fallback id_fall id1 id2 ... ;
                input.parse::<kw::fallback>()?;
                let fallback = input.parse()?;
                let mut ids = Vec::new();
                while !input.peek(Token![;]) {
                    ids.push(input.parse()?);
                }
                input.parse::<Token![;]>()?;
                Ok(Decl::Fallback(fallback, ids))
            } else if lookahead.peek(kw::wildcard) {
                // %wildcard id;
                input.parse::<kw::wildcard>()?;
                let id = input.parse()?;
                input.parse::<Token![;]>()?;
                Ok(Decl::Wildcard(id))
            } else if lookahead.peek(kw::token_class) {
                // %token_class tk id1 id2... ;
                input.parse::<kw::token_class>()?;
                let tk = input.parse()?;
                let mut ids = Vec::new();
                while !input.peek(Token![;]) {
                    ids.push(input.parse()?);
                }
                input.parse::<Token![;]>()?;
                Ok(Decl::TokenClass(tk, ids))
            } else if lookahead.peek(kw::token) {
                // %token enum;
                input.parse::<kw::token>()?;
                let e = input.parse()?;
                input.parse::<Token![;]>()?;
                Ok(Decl::Token(e))
            } else if lookahead.peek(kw::extra_token) {
                // %extra_token type;
                input.parse::<kw::extra_token>()?;
                let typ = input.parse()?;
                input.parse::<Token![;]>()?;
                Ok(Decl::ExtraToken(typ))
            } else if lookahead.peek(kw::stack_size) {
                // %stack_size limit [type];
                input.parse::<kw::stack_size>()?;
                let limit = input.parse::<LitInt>()?.base10_parse::<usize>()?;
                let typ = if input.peek(Token![;]) {
                    None
                } else {
                    Some(input.parse()?)
                };
                input.parse::<Token![;]>()?;
                Ok(Decl::StackSize(limit, typ))
            } else if lookahead.peek(kw::verbose) {
                // %verbose;
                input.parse::<kw::verbose>()?;
                input.parse::<Token![;]>()?;
                Ok(Decl::Verbose)
            } else if lookahead.peek(kw::parser) {
                // %parser struct;
                input.parse::<kw::parser>()?;
                let e = input.parse()?;
                input.parse::<Token![;]>()?;
                Ok(Decl::Parser(e))
            } else {
                Err(lookahead.error())
            }
        } else {
            // rule: id ::= rhs1 rhs2 ... [[precedence]] [ { code } ] [;]
            // rhs:  id1|id2[?][(alias)]
            let lhs = input
                .parse::<Ident>()
                .map_err(|e| Error::new(e.span(), "% or identifier expected"))?;
            input.parse::<Token![::]>()?;
            input.parse::<Token![=]>()?;
            let mut rhs = Vec::new();
            loop {
                let lookahead = input.lookahead1();
                if !lookahead.peek(Ident) {
                    break;
                }
                //rhs
                let toks = Punctuated::<Ident, Token![|]>::parse_separated_nonempty(input)?;
                let toks = toks.into_iter().collect();
                let optional = if input.peek(Token![?]) {
                    input.parse::<Token![?]>()?;
                    true
                } else {
                    false
                };
                let alias = if input.peek(token::Paren) {
                    let sub;
                    parenthesized!(sub in input);
                    Some(sub.parse()?)
                } else {
                    None
                };
                rhs.push((toks, optional, alias));
            }
            let prec = if input.peek(token::Bracket) {
                let sub;
                bracketed!(sub in input);
                Some(sub.parse()?)
            } else {
                None
            };
            let action = if input.peek(token::Brace) {
                Some(input.parse()?)
            } else {
                None
            };
            if input.peek(Token![;]) {
                input.parse::<Token![;]>()?;
            }
            Ok(Decl::Rule {
                lhs,
                rhs,
                action,
                prec,
            })
        }
    }
}