src/libsyntax/parse/obsolete.rs

// Copyright 2012-2014 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.

//! Support for parsing unsupported, old syntaxes, for the purpose of reporting errors. Parsing of
//! these syntaxes is tested by compile-test/obsolete-syntax.rs.
//!
//! Obsolete syntax that becomes too hard to parse can be removed.

use ast::{Expr, ExprTup};
use codemap::Span;
use parse::parser;
use parse::token;
use ptr::P;

/// The specific types of unsupported syntax
#[derive(Copy, Clone, PartialEq, Eq, Hash)]
pub enum ObsoleteSyntax {
    ClosureKind,
    ExternCrateString,
}

pub trait ParserObsoleteMethods {
    /// Reports an obsolete syntax non-fatal error.
    fn obsolete(&mut self, sp: Span, kind: ObsoleteSyntax);
    /// Reports an obsolete syntax non-fatal error, and returns
    /// a placeholder expression
    fn obsolete_expr(&mut self, sp: Span, kind: ObsoleteSyntax) -> P<Expr>;
    fn report(&mut self,
              sp: Span,
              kind: ObsoleteSyntax,
              kind_str: &str,
              desc: &str,
              error: bool);
    fn is_obsolete_ident(&mut self, ident: &str) -> bool;
    fn eat_obsolete_ident(&mut self, ident: &str) -> bool;
}

impl<'a> ParserObsoleteMethods for parser::Parser<'a> {
    /// Reports an obsolete syntax non-fatal error.
    fn obsolete(&mut self, sp: Span, kind: ObsoleteSyntax) {
        let (kind_str, desc, error) = match kind {
            ObsoleteSyntax::ClosureKind => (
                "`:`, `&mut:`, or `&:`",
                "rely on inference instead",
                true,
            ),
            ObsoleteSyntax::ExternCrateString => (
                "\"crate-name\"",
                "use an identifier not in quotes instead",
                false, // warning for now
            ),
        };

        self.report(sp, kind, kind_str, desc, error);
    }

    /// Reports an obsolete syntax non-fatal error, and returns
    /// a placeholder expression
    fn obsolete_expr(&mut self, sp: Span, kind: ObsoleteSyntax) -> P<Expr> {
        self.obsolete(sp, kind);
        self.mk_expr(sp.lo, sp.hi, ExprTup(vec![]))
    }

    fn report(&mut self,
              sp: Span,
              kind: ObsoleteSyntax,
              kind_str: &str,
              desc: &str,
              error: bool) {
        if error {
            self.span_err(sp, &format!("obsolete syntax: {}", kind_str));
        } else {
            self.span_warn(sp, &format!("obsolete syntax: {}", kind_str));
        }

        if !self.obsolete_set.contains(&kind) &&
            (error || self.sess.span_diagnostic.handler().can_emit_warnings) {
            self.sess
                .span_diagnostic
                .handler()
                .note(&format!("{}", desc));
            self.obsolete_set.insert(kind);
        }
    }

    fn is_obsolete_ident(&mut self, ident: &str) -> bool {
        match self.token {
            token::Ident(sid, _) => {
                token::get_ident(sid) == ident
            }
            _ => false
        }
    }

    fn eat_obsolete_ident(&mut self, ident: &str) -> bool {
        if self.is_obsolete_ident(ident) {
            panictry!(self.bump());
            true
        } else {
            false
        }
    }
}