556 lines
22 KiB
Rust
556 lines
22 KiB
Rust
// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use ast::{self, TokenTree};
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use codemap::{Span, DUMMY_SP};
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use ext::base::{DummyResult, ExtCtxt, MacResult, SyntaxExtension};
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use ext::base::{NormalTT, TTMacroExpander};
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use ext::tt::macro_parser::{Success, Error, Failure};
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use ext::tt::macro_parser::{MatchedSeq, MatchedNonterminal};
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use ext::tt::macro_parser::parse;
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use parse::lexer::new_tt_reader;
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use parse::parser::Parser;
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use parse::token::{self, special_idents, gensym_ident, NtTT, Token};
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use parse::token::Token::*;
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use print;
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use ptr::P;
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use util::small_vector::SmallVector;
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use std::cell::RefCell;
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use std::rc::Rc;
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use std::iter::once;
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struct ParserAnyMacro<'a> {
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parser: RefCell<Parser<'a>>,
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/// Span of the expansion site of the macro this parser is for
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site_span: Span,
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/// The ident of the macro we're parsing
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macro_ident: ast::Ident
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}
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impl<'a> ParserAnyMacro<'a> {
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/// Make sure we don't have any tokens left to parse, so we don't
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/// silently drop anything. `allow_semi` is so that "optional"
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/// semicolons at the end of normal expressions aren't complained
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/// about e.g. the semicolon in `macro_rules! kapow { () => {
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/// panic!(); } }` doesn't get picked up by .parse_expr(), but it's
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/// allowed to be there.
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fn ensure_complete_parse(&self, allow_semi: bool, context: &str) {
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let mut parser = self.parser.borrow_mut();
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if allow_semi && parser.token == token::Semi {
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panictry!(parser.bump())
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}
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if parser.token != token::Eof {
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let token_str = parser.this_token_to_string();
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let msg = format!("macro expansion ignores token `{}` and any \
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following",
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token_str);
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let span = parser.span;
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parser.span_err(span, &msg[..]);
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let msg = format!("caused by the macro expansion here; the usage \
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of `{}!` is likely invalid in {} context",
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self.macro_ident, context);
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parser.span_note(self.site_span, &msg[..]);
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}
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}
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}
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impl<'a> MacResult for ParserAnyMacro<'a> {
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fn make_expr(self: Box<ParserAnyMacro<'a>>) -> Option<P<ast::Expr>> {
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let ret = panictry!(self.parser.borrow_mut().parse_expr());
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self.ensure_complete_parse(true, "expression");
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Some(ret)
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}
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fn make_pat(self: Box<ParserAnyMacro<'a>>) -> Option<P<ast::Pat>> {
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let ret = panictry!(self.parser.borrow_mut().parse_pat());
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self.ensure_complete_parse(false, "pattern");
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Some(ret)
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}
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fn make_items(self: Box<ParserAnyMacro<'a>>) -> Option<SmallVector<P<ast::Item>>> {
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let mut ret = SmallVector::zero();
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while let Some(item) = panictry!(self.parser.borrow_mut().parse_item()) {
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ret.push(item);
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}
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self.ensure_complete_parse(false, "item");
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Some(ret)
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}
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fn make_impl_items(self: Box<ParserAnyMacro<'a>>)
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-> Option<SmallVector<P<ast::ImplItem>>> {
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let mut ret = SmallVector::zero();
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loop {
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let mut parser = self.parser.borrow_mut();
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match parser.token {
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token::Eof => break,
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_ => ret.push(panictry!(parser.parse_impl_item()))
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}
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}
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self.ensure_complete_parse(false, "item");
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Some(ret)
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}
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fn make_stmts(self: Box<ParserAnyMacro<'a>>)
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-> Option<SmallVector<P<ast::Stmt>>> {
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let mut ret = SmallVector::zero();
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loop {
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let mut parser = self.parser.borrow_mut();
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match parser.token {
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token::Eof => break,
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_ => match parser.parse_stmt() {
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Ok(maybe_stmt) => match maybe_stmt {
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Some(stmt) => ret.push(stmt),
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None => (),
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},
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Err(_) => break,
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}
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}
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}
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self.ensure_complete_parse(false, "statement");
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Some(ret)
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}
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fn make_ty(self: Box<ParserAnyMacro<'a>>) -> Option<P<ast::Ty>> {
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let ret = panictry!(self.parser.borrow_mut().parse_ty());
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self.ensure_complete_parse(false, "type");
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Some(ret)
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}
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}
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struct MacroRulesMacroExpander {
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name: ast::Ident,
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imported_from: Option<ast::Ident>,
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lhses: Vec<TokenTree>,
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rhses: Vec<TokenTree>,
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valid: bool,
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}
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impl TTMacroExpander for MacroRulesMacroExpander {
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fn expand<'cx>(&self,
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cx: &'cx mut ExtCtxt,
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sp: Span,
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arg: &[TokenTree])
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-> Box<MacResult+'cx> {
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if !self.valid {
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return DummyResult::any(sp);
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}
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generic_extension(cx,
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sp,
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self.name,
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self.imported_from,
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arg,
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&self.lhses,
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&self.rhses)
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}
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}
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/// Given `lhses` and `rhses`, this is the new macro we create
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fn generic_extension<'cx>(cx: &'cx ExtCtxt,
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sp: Span,
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name: ast::Ident,
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imported_from: Option<ast::Ident>,
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arg: &[TokenTree],
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lhses: &[TokenTree],
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rhses: &[TokenTree])
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-> Box<MacResult+'cx> {
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if cx.trace_macros() {
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println!("{}! {{ {} }}",
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name,
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print::pprust::tts_to_string(arg));
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}
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// Which arm's failure should we report? (the one furthest along)
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let mut best_fail_spot = DUMMY_SP;
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let mut best_fail_msg = "internal error: ran no matchers".to_string();
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for (i, lhs) in lhses.iter().enumerate() { // try each arm's matchers
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let lhs_tt = match *lhs {
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TokenTree::Delimited(_, ref delim) => &delim.tts[..],
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_ => cx.span_bug(sp, "malformed macro lhs")
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};
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match TokenTree::parse(cx, lhs_tt, arg) {
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Success(named_matches) => {
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let rhs = match rhses[i] {
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// ignore delimiters
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TokenTree::Delimited(_, ref delimed) => delimed.tts.clone(),
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_ => cx.span_bug(sp, "malformed macro rhs"),
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};
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// rhs has holes ( `$id` and `$(...)` that need filled)
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let trncbr = new_tt_reader(&cx.parse_sess().span_diagnostic,
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Some(named_matches),
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imported_from,
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rhs);
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let mut p = Parser::new(cx.parse_sess(), cx.cfg(), Box::new(trncbr));
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panictry!(p.check_unknown_macro_variable());
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// Let the context choose how to interpret the result.
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// Weird, but useful for X-macros.
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return Box::new(ParserAnyMacro {
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parser: RefCell::new(p),
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// Pass along the original expansion site and the name of the macro
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// so we can print a useful error message if the parse of the expanded
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// macro leaves unparsed tokens.
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site_span: sp,
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macro_ident: name
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})
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}
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Failure(sp, ref msg) => if sp.lo >= best_fail_spot.lo {
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best_fail_spot = sp;
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best_fail_msg = (*msg).clone();
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},
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Error(err_sp, ref msg) => {
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cx.span_fatal(err_sp.substitute_dummy(sp), &msg[..])
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}
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}
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}
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cx.span_fatal(best_fail_spot.substitute_dummy(sp), &best_fail_msg[..]);
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}
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// Note that macro-by-example's input is also matched against a token tree:
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// $( $lhs:tt => $rhs:tt );+
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//
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// Holy self-referential!
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/// Converts a `macro_rules!` invocation into a syntax extension.
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pub fn compile<'cx>(cx: &'cx mut ExtCtxt,
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def: &ast::MacroDef) -> SyntaxExtension {
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let lhs_nm = gensym_ident("lhs");
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let rhs_nm = gensym_ident("rhs");
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// The pattern that macro_rules matches.
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// The grammar for macro_rules! is:
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// $( $lhs:tt => $rhs:tt );+
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// ...quasiquoting this would be nice.
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// These spans won't matter, anyways
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let match_lhs_tok = MatchNt(lhs_nm, special_idents::tt, token::Plain, token::Plain);
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let match_rhs_tok = MatchNt(rhs_nm, special_idents::tt, token::Plain, token::Plain);
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let argument_gram = vec!(
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TokenTree::Sequence(DUMMY_SP,
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Rc::new(ast::SequenceRepetition {
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tts: vec![
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TokenTree::Token(DUMMY_SP, match_lhs_tok),
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TokenTree::Token(DUMMY_SP, token::FatArrow),
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TokenTree::Token(DUMMY_SP, match_rhs_tok)],
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separator: Some(token::Semi),
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op: ast::OneOrMore,
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num_captures: 2
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})),
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//to phase into semicolon-termination instead of
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//semicolon-separation
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TokenTree::Sequence(DUMMY_SP,
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Rc::new(ast::SequenceRepetition {
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tts: vec![TokenTree::Token(DUMMY_SP, token::Semi)],
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separator: None,
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op: ast::ZeroOrMore,
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num_captures: 0
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})));
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// Parse the macro_rules! invocation (`none` is for no interpolations):
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let arg_reader = new_tt_reader(&cx.parse_sess().span_diagnostic,
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None,
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None,
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def.body.clone());
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let argument_map = match parse(cx.parse_sess(),
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cx.cfg(),
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arg_reader,
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&argument_gram) {
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Success(m) => m,
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Failure(sp, str) | Error(sp, str) => {
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panic!(cx.parse_sess().span_diagnostic
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.span_fatal(sp.substitute_dummy(def.span), &str[..]));
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}
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};
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let mut valid = true;
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// Extract the arguments:
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let lhses = match **argument_map.get(&lhs_nm.name).unwrap() {
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MatchedSeq(ref s, _) => {
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s.iter().map(|m| match **m {
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MatchedNonterminal(NtTT(ref tt)) => (**tt).clone(),
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_ => cx.span_bug(def.span, "wrong-structured lhs")
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}).collect()
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}
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_ => cx.span_bug(def.span, "wrong-structured lhs")
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};
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for lhs in &lhses {
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check_lhs_nt_follows(cx, lhs, def.span);
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}
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let rhses = match **argument_map.get(&rhs_nm.name).unwrap() {
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MatchedSeq(ref s, _) => {
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s.iter().map(|m| match **m {
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MatchedNonterminal(NtTT(ref tt)) => (**tt).clone(),
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_ => cx.span_bug(def.span, "wrong-structured rhs")
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}).collect()
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}
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_ => cx.span_bug(def.span, "wrong-structured rhs")
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};
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for rhs in &rhses {
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valid &= check_rhs(cx, rhs);
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}
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let exp: Box<_> = Box::new(MacroRulesMacroExpander {
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name: def.ident,
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imported_from: def.imported_from,
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lhses: lhses,
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rhses: rhses,
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valid: valid,
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});
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NormalTT(exp, Some(def.span), def.allow_internal_unstable)
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}
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fn check_lhs_nt_follows(cx: &mut ExtCtxt, lhs: &TokenTree, sp: Span) {
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// lhs is going to be like TokenTree::Delimited(...), where the
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// entire lhs is those tts. Or, it can be a "bare sequence", not wrapped in parens.
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match lhs {
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&TokenTree::Delimited(_, ref tts) => {
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check_matcher(cx, tts.tts.iter(), &Eof);
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},
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tt @ &TokenTree::Sequence(..) => {
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check_matcher(cx, Some(tt).into_iter(), &Eof);
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},
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_ => cx.span_err(sp, "invalid macro matcher; matchers must be contained \
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in balanced delimiters or a repetition indicator")
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};
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// we don't abort on errors on rejection, the driver will do that for us
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// after parsing/expansion. we can report every error in every macro this way.
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}
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fn check_rhs(cx: &mut ExtCtxt, rhs: &TokenTree) -> bool {
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match *rhs {
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TokenTree::Delimited(..) => return true,
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_ => cx.span_err(rhs.get_span(), "macro rhs must be delimited")
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}
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false
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}
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// returns the last token that was checked, for TokenTree::Sequence. this gets used later on.
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fn check_matcher<'a, I>(cx: &mut ExtCtxt, matcher: I, follow: &Token)
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-> Option<(Span, Token)> where I: Iterator<Item=&'a TokenTree> {
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use print::pprust::token_to_string;
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let mut last = None;
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// 2. For each token T in M:
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let mut tokens = matcher.peekable();
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while let Some(token) = tokens.next() {
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last = match *token {
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TokenTree::Token(sp, MatchNt(ref name, ref frag_spec, _, _)) => {
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// ii. If T is a simple NT, look ahead to the next token T' in
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// M. If T' is in the set FOLLOW(NT), continue. Else; reject.
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if can_be_followed_by_any(&frag_spec.name.as_str()) {
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continue
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} else {
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let next_token = match tokens.peek() {
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// If T' closes a complex NT, replace T' with F
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Some(&&TokenTree::Token(_, CloseDelim(_))) => follow.clone(),
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Some(&&TokenTree::Token(_, ref tok)) => tok.clone(),
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Some(&&TokenTree::Sequence(sp, _)) => {
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// Be conservative around sequences: to be
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// more specific, we would need to
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// consider FIRST sets, but also the
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// possibility that the sequence occurred
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// zero times (in which case we need to
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// look at the token that follows the
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// sequence, which may itself be a sequence,
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// and so on).
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cx.span_err(sp,
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&format!("`${0}:{1}` is followed by a \
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sequence repetition, which is not \
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allowed for `{1}` fragments",
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name, frag_spec)
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);
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Eof
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},
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// die next iteration
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Some(&&TokenTree::Delimited(_, ref delim)) => delim.close_token(),
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// else, we're at the end of the macro or sequence
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None => follow.clone()
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};
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let tok = if let TokenTree::Token(_, ref tok) = *token {
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tok
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} else {
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unreachable!()
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};
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// If T' is in the set FOLLOW(NT), continue. Else, reject.
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match (&next_token, is_in_follow(cx, &next_token, &frag_spec.name.as_str())) {
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(_, Err(msg)) => {
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cx.span_err(sp, &msg);
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continue
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}
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(&Eof, _) => return Some((sp, tok.clone())),
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(_, Ok(true)) => continue,
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(next, Ok(false)) => {
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cx.span_err(sp, &format!("`${0}:{1}` is followed by `{2}`, which \
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is not allowed for `{1}` fragments",
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name, frag_spec,
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token_to_string(next)));
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continue
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},
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}
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}
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},
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TokenTree::Sequence(sp, ref seq) => {
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// iii. Else, T is a complex NT.
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match seq.separator {
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// If T has the form $(...)U+ or $(...)U* for some token U,
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// run the algorithm on the contents with F set to U. If it
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// accepts, continue, else, reject.
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Some(ref u) => {
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let last = check_matcher(cx, seq.tts.iter(), u);
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match last {
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// Since the delimiter isn't required after the last
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// repetition, make sure that the *next* token is
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// sane. This doesn't actually compute the FIRST of
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// the rest of the matcher yet, it only considers
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// single tokens and simple NTs. This is imprecise,
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// but conservatively correct.
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Some((span, tok)) => {
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let fol = match tokens.peek() {
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Some(&&TokenTree::Token(_, ref tok)) => tok.clone(),
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Some(&&TokenTree::Delimited(_, ref delim)) =>
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delim.close_token(),
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Some(_) => {
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cx.span_err(sp, "sequence repetition followed by \
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another sequence repetition, which is not allowed");
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Eof
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},
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None => Eof
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};
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check_matcher(cx, once(&TokenTree::Token(span, tok.clone())),
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&fol)
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},
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None => last,
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}
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},
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// If T has the form $(...)+ or $(...)*, run the algorithm
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// on the contents with F set to the token following the
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// sequence. If it accepts, continue, else, reject.
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None => {
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let fol = match tokens.peek() {
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Some(&&TokenTree::Token(_, ref tok)) => tok.clone(),
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Some(&&TokenTree::Delimited(_, ref delim)) => delim.close_token(),
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Some(_) => {
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cx.span_err(sp, "sequence repetition followed by another \
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sequence repetition, which is not allowed");
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Eof
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},
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None => Eof
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};
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check_matcher(cx, seq.tts.iter(), &fol)
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}
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}
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},
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TokenTree::Token(..) => {
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// i. If T is not an NT, continue.
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continue
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},
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TokenTree::Delimited(_, ref tts) => {
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// if we don't pass in that close delimiter, we'll incorrectly consider the matcher
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// `{ $foo:ty }` as having a follow that isn't `RBrace`
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check_matcher(cx, tts.tts.iter(), &tts.close_token())
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}
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}
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}
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last
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}
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/// True if a fragment of type `frag` can be followed by any sort of
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/// token. We use this (among other things) as a useful approximation
|
|
/// for when `frag` can be followed by a repetition like `$(...)*` or
|
|
/// `$(...)+`. In general, these can be a bit tricky to reason about,
|
|
/// so we adopt a conservative position that says that any fragment
|
|
/// specifier which consumes at most one token tree can be followed by
|
|
/// a fragment specifier (indeed, these fragments can be followed by
|
|
/// ANYTHING without fear of future compatibility hazards).
|
|
fn can_be_followed_by_any(frag: &str) -> bool {
|
|
match frag {
|
|
"item" | // always terminated by `}` or `;`
|
|
"block" | // exactly one token tree
|
|
"ident" | // exactly one token tree
|
|
"meta" | // exactly one token tree
|
|
"tt" => // exactly one token tree
|
|
true,
|
|
|
|
_ =>
|
|
false,
|
|
}
|
|
}
|
|
|
|
/// True if `frag` can legally be followed by the token `tok`. For
|
|
/// fragments that can consume an unbounded numbe of tokens, `tok`
|
|
/// must be within a well-defined follow set. This is intended to
|
|
/// guarantee future compatibility: for example, without this rule, if
|
|
/// we expanded `expr` to include a new binary operator, we might
|
|
/// break macros that were relying on that binary operator as a
|
|
/// separator.
|
|
fn is_in_follow(_: &ExtCtxt, tok: &Token, frag: &str) -> Result<bool, String> {
|
|
if let &CloseDelim(_) = tok {
|
|
// closing a token tree can never be matched by any fragment;
|
|
// iow, we always require that `(` and `)` match, etc.
|
|
Ok(true)
|
|
} else {
|
|
match frag {
|
|
"item" => {
|
|
// since items *must* be followed by either a `;` or a `}`, we can
|
|
// accept anything after them
|
|
Ok(true)
|
|
},
|
|
"block" => {
|
|
// anything can follow block, the braces provide an easy boundary to
|
|
// maintain
|
|
Ok(true)
|
|
},
|
|
"stmt" | "expr" => {
|
|
match *tok {
|
|
FatArrow | Comma | Semi => Ok(true),
|
|
_ => Ok(false)
|
|
}
|
|
},
|
|
"pat" => {
|
|
match *tok {
|
|
FatArrow | Comma | Eq => Ok(true),
|
|
Ident(i, _) if i.name.as_str() == "if" || i.name.as_str() == "in" => Ok(true),
|
|
_ => Ok(false)
|
|
}
|
|
},
|
|
"path" | "ty" => {
|
|
match *tok {
|
|
Comma | FatArrow | Colon | Eq | Gt | Semi => Ok(true),
|
|
Ident(i, _) if i.name.as_str() == "as" => Ok(true),
|
|
_ => Ok(false)
|
|
}
|
|
},
|
|
"ident" => {
|
|
// being a single token, idents are harmless
|
|
Ok(true)
|
|
},
|
|
"meta" | "tt" => {
|
|
// being either a single token or a delimited sequence, tt is
|
|
// harmless
|
|
Ok(true)
|
|
},
|
|
_ => Err(format!("invalid fragment specifier `{}`", frag))
|
|
}
|
|
}
|
|
}
|