rust/src/librustc/middle/pat_util.rs

// 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 middle::ty::{CopyValue, MoveValue, ReadValue};

use syntax::ast::*;
use syntax::ast_util;
use syntax::ast_util::{path_to_ident, respan, walk_pat};
use syntax::fold;
use syntax::fold::*;
use syntax::codemap::span;
use std::map::HashMap;

export pat_binding_ids, pat_bindings, pat_id_map, PatIdMap;
export pat_is_variant_or_struct, pat_is_binding, pat_is_binding_or_wild;
export pat_is_const;
export arms_have_by_move_bindings;

type PatIdMap = std::map::HashMap<ident, node_id>;

// This is used because same-named variables in alternative patterns need to
// use the node_id of their namesake in the first pattern.
fn pat_id_map(dm: resolve::DefMap, pat: @pat) -> PatIdMap {
    let map = std::map::HashMap();
    do pat_bindings(dm, pat) |_bm, p_id, _s, n| {
      map.insert(path_to_ident(n), p_id);
    };
    return map;
}

fn pat_is_variant_or_struct(dm: resolve::DefMap, pat: @pat) -> bool {
    match pat.node {
        pat_enum(_, _) | pat_ident(_, _, None) | pat_struct(*) => {
            match dm.find(pat.id) {
                Some(def_variant(*)) | Some(def_class(*)) => true,
                _ => false
            }
        }
        _ => false
    }
}

fn pat_is_const(dm: resolve::DefMap, pat: &pat) -> bool {
    match pat.node {
        pat_ident(_, _, None) => {
            match dm.find(pat.id) {
                Some(def_const(*)) => true,
                _ => false
            }
        }
        _ => false
    }
}

fn pat_is_binding(dm: resolve::DefMap, pat: @pat) -> bool {
    match pat.node {
        pat_ident(*) => {
            !pat_is_variant_or_struct(dm, pat) &&
            !pat_is_const(dm, pat)
        }
        _ => false
    }
}

fn pat_is_binding_or_wild(dm: resolve::DefMap, pat: @pat) -> bool {
    match pat.node {
        pat_ident(*) => pat_is_binding(dm, pat),
        pat_wild => true,
        _ => false
    }
}

fn pat_bindings(dm: resolve::DefMap, pat: @pat,
                it: fn(binding_mode, node_id, span, @path)) {
    do walk_pat(pat) |p| {
        match p.node {
          pat_ident(binding_mode, pth, _) if pat_is_binding(dm, p) => {
            it(binding_mode, p.id, p.span, pth);
          }
          _ => {}
        }
    }
}

fn pat_binding_ids(dm: resolve::DefMap, pat: @pat) -> ~[node_id] {
    let mut found = ~[];
    pat_bindings(dm, pat, |_bm, b_id, _sp, _pt| found.push(b_id) );
    return found;
}

fn arms_have_by_move_bindings(tcx: ty::ctxt, +arms: &[arm]) -> bool {
    for arms.each |arm| {
        for arm.pats.each |pat| {
            let mut found = false;
            do pat_bindings(tcx.def_map, *pat)
                    |binding_mode, node_id, span, _path| {
                match binding_mode {
                    bind_by_move => found = true,
                    bind_infer => {
                        match tcx.value_modes.find(node_id) {
                            Some(MoveValue) => found = true,
                            Some(CopyValue) | Some(ReadValue) => {}
                            None => {
                                tcx.sess.span_bug(span, ~"pat binding not in \
                                                          value mode map");
                            }
                        }
                    }
                    bind_by_ref(*) | bind_by_value => {}
                }
            }
            if found { return true; }
        }
    }
    return false;
}