/
macro_rules.rs
273 lines (250 loc) · 9.98 KB
/
macro_rules.rs
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// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use ast::{Ident, Matcher_, Matcher, MatchTok, MatchNonterminal, MatchSeq, TtDelimited};
use ast;
use codemap::{Span, Spanned, DUMMY_SP};
use ext::base::{ExtCtxt, MacResult, MacroDef};
use ext::base::{NormalTT, TTMacroExpander};
use ext::tt::macro_parser::{Success, Error, Failure};
use ext::tt::macro_parser::{NamedMatch, MatchedSeq, MatchedNonterminal};
use ext::tt::macro_parser::{parse, parse_or_else};
use parse::lexer::new_tt_reader;
use parse::parser::Parser;
use parse::attr::ParserAttr;
use parse::token::{special_idents, gensym_ident};
use parse::token::{FAT_ARROW, SEMI, NtMatchers, NtTT, EOF};
use parse::token;
use print;
use ptr::P;
use util::small_vector::SmallVector;
use std::cell::RefCell;
use std::rc::Rc;
struct ParserAnyMacro<'a> {
parser: RefCell<Parser<'a>>,
}
impl<'a> ParserAnyMacro<'a> {
/// Make sure we don't have any tokens left to parse, so we don't
/// silently drop anything. `allow_semi` is so that "optional"
/// semicolons at the end of normal expressions aren't complained
/// about e.g. the semicolon in `macro_rules! kapow( () => {
/// fail!(); } )` doesn't get picked up by .parse_expr(), but it's
/// allowed to be there.
fn ensure_complete_parse(&self, allow_semi: bool) {
let mut parser = self.parser.borrow_mut();
if allow_semi && parser.token == SEMI {
parser.bump()
}
if parser.token != EOF {
let token_str = parser.this_token_to_string();
let msg = format!("macro expansion ignores token `{}` and any \
following",
token_str);
let span = parser.span;
parser.span_err(span, msg.as_slice());
}
}
}
impl<'a> MacResult for ParserAnyMacro<'a> {
fn make_expr(self: Box<ParserAnyMacro<'a>>) -> Option<P<ast::Expr>> {
let ret = self.parser.borrow_mut().parse_expr();
self.ensure_complete_parse(true);
Some(ret)
}
fn make_pat(self: Box<ParserAnyMacro<'a>>) -> Option<P<ast::Pat>> {
let ret = self.parser.borrow_mut().parse_pat();
self.ensure_complete_parse(false);
Some(ret)
}
fn make_items(self: Box<ParserAnyMacro<'a>>) -> Option<SmallVector<P<ast::Item>>> {
let mut ret = SmallVector::zero();
loop {
let mut parser = self.parser.borrow_mut();
// so... do outer attributes attached to the macro invocation
// just disappear? This question applies to make_methods, as
// well.
match parser.parse_item_with_outer_attributes() {
Some(item) => ret.push(item),
None => break
}
}
self.ensure_complete_parse(false);
Some(ret)
}
fn make_methods(self: Box<ParserAnyMacro<'a>>) -> Option<SmallVector<P<ast::Method>>> {
let mut ret = SmallVector::zero();
loop {
let mut parser = self.parser.borrow_mut();
match parser.token {
EOF => break,
_ => {
let attrs = parser.parse_outer_attributes();
ret.push(parser.parse_method(attrs, ast::Inherited))
}
}
}
self.ensure_complete_parse(false);
Some(ret)
}
fn make_stmt(self: Box<ParserAnyMacro<'a>>) -> Option<P<ast::Stmt>> {
let attrs = self.parser.borrow_mut().parse_outer_attributes();
let ret = self.parser.borrow_mut().parse_stmt(attrs);
self.ensure_complete_parse(true);
Some(ret)
}
}
struct MacroRulesMacroExpander {
name: Ident,
lhses: Vec<Rc<NamedMatch>>,
rhses: Vec<Rc<NamedMatch>>,
}
impl TTMacroExpander for MacroRulesMacroExpander {
fn expand<'cx>(&self,
cx: &'cx mut ExtCtxt,
sp: Span,
arg: &[ast::TokenTree])
-> Box<MacResult+'cx> {
generic_extension(cx,
sp,
self.name,
arg,
self.lhses.as_slice(),
self.rhses.as_slice())
}
}
struct MacroRulesDefiner {
def: Option<MacroDef>
}
impl MacResult for MacroRulesDefiner {
fn make_def(&mut self) -> Option<MacroDef> {
Some(self.def.take().expect("empty MacroRulesDefiner"))
}
}
/// Given `lhses` and `rhses`, this is the new macro we create
fn generic_extension<'cx>(cx: &'cx ExtCtxt,
sp: Span,
name: Ident,
arg: &[ast::TokenTree],
lhses: &[Rc<NamedMatch>],
rhses: &[Rc<NamedMatch>])
-> Box<MacResult+'cx> {
if cx.trace_macros() {
println!("{}! {{ {} }}",
token::get_ident(name),
print::pprust::tts_to_string(arg));
}
// Which arm's failure should we report? (the one furthest along)
let mut best_fail_spot = DUMMY_SP;
let mut best_fail_msg = "internal error: ran no matchers".to_string();
for (i, lhs) in lhses.iter().enumerate() { // try each arm's matchers
match **lhs {
MatchedNonterminal(NtMatchers(ref mtcs)) => {
// `None` is because we're not interpolating
let arg_rdr = new_tt_reader(&cx.parse_sess().span_diagnostic,
None,
arg.iter()
.map(|x| (*x).clone())
.collect());
match parse(cx.parse_sess(), cx.cfg(), arg_rdr, mtcs.as_slice()) {
Success(named_matches) => {
let rhs = match *rhses[i] {
// okay, what's your transcriber?
MatchedNonterminal(NtTT(ref tt)) => {
match **tt {
// ignore delimiters
TtDelimited(_, ref delimed) => {
let (_, ref tts, _) = **delimed;
tts.clone()
},
_ => cx.span_fatal(sp, "macro rhs must be delimited"),
}
},
_ => cx.span_bug(sp, "bad thing in rhs")
};
// rhs has holes ( `$id` and `$(...)` that need filled)
let trncbr = new_tt_reader(&cx.parse_sess().span_diagnostic,
Some(named_matches),
rhs);
let p = Parser::new(cx.parse_sess(), cx.cfg(), box trncbr);
// Let the context choose how to interpret the result.
// Weird, but useful for X-macros.
return box ParserAnyMacro {
parser: RefCell::new(p),
} as Box<MacResult+'cx>
}
Failure(sp, ref msg) => if sp.lo >= best_fail_spot.lo {
best_fail_spot = sp;
best_fail_msg = (*msg).clone();
},
Error(sp, ref msg) => cx.span_fatal(sp, msg.as_slice())
}
}
_ => cx.bug("non-matcher found in parsed lhses")
}
}
cx.span_fatal(best_fail_spot, best_fail_msg.as_slice());
}
/// This procedure performs the expansion of the
/// macro_rules! macro. It parses the RHS and adds
/// an extension to the current context.
pub fn add_new_extension<'cx>(cx: &'cx mut ExtCtxt,
sp: Span,
name: Ident,
arg: Vec<ast::TokenTree> )
-> Box<MacResult+'cx> {
// these spans won't matter, anyways
fn ms(m: Matcher_) -> Matcher {
Spanned {
node: m.clone(),
span: DUMMY_SP
}
}
let lhs_nm = gensym_ident("lhs");
let rhs_nm = gensym_ident("rhs");
// The pattern that macro_rules matches.
// The grammar for macro_rules! is:
// $( $lhs:mtcs => $rhs:tt );+
// ...quasiquoting this would be nice.
let argument_gram = vec!(
ms(MatchSeq(vec!(
ms(MatchNonterminal(lhs_nm, special_idents::matchers, 0u)),
ms(MatchTok(FAT_ARROW)),
ms(MatchNonterminal(rhs_nm, special_idents::tt, 1u))), Some(SEMI), false, 0u, 2u)),
//to phase into semicolon-termination instead of
//semicolon-separation
ms(MatchSeq(vec!(ms(MatchTok(SEMI))), None, true, 2u, 2u)));
// Parse the macro_rules! invocation (`none` is for no interpolations):
let arg_reader = new_tt_reader(&cx.parse_sess().span_diagnostic,
None,
arg.clone());
let argument_map = parse_or_else(cx.parse_sess(),
cx.cfg(),
arg_reader,
argument_gram);
// Extract the arguments:
let lhses = match *argument_map[lhs_nm] {
MatchedSeq(ref s, _) => /* FIXME (#2543) */ (*s).clone(),
_ => cx.span_bug(sp, "wrong-structured lhs")
};
let rhses = match *argument_map[rhs_nm] {
MatchedSeq(ref s, _) => /* FIXME (#2543) */ (*s).clone(),
_ => cx.span_bug(sp, "wrong-structured rhs")
};
let exp = box MacroRulesMacroExpander {
name: name,
lhses: lhses,
rhses: rhses,
};
box MacroRulesDefiner {
def: Some(MacroDef {
name: token::get_ident(name).to_string(),
ext: NormalTT(exp, Some(sp))
})
} as Box<MacResult+'cx>
}