rust/src/librustc/middle/freevars.rs

133 lines
4.7 KiB
Rust

// 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.
// A pass that annotates for each loops and functions with the free
// variables that they contain.
use syntax::print::pprust::path_to_str;
use std::map::*;
use option::*;
use syntax::{ast, ast_util, visit};
use syntax::codemap::span;
export annotate_freevars;
export freevar_map;
export freevar_info;
export freevar_entry;
export get_freevars;
export has_freevars;
// A vector of defs representing the free variables referred to in a function.
// (The def_upvar will already have been stripped).
#[auto_serialize]
#[auto_deserialize]
type freevar_entry = {
def: ast::def, //< The variable being accessed free.
span: span //< First span where it is accessed (there can be multiple)
};
type freevar_info = @~[@freevar_entry];
type freevar_map = HashMap<ast::node_id, freevar_info>;
// Searches through part of the AST for all references to locals or
// upvars in this frame and returns the list of definition IDs thus found.
// Since we want to be able to collect upvars in some arbitrary piece
// of the AST, we take a walker function that we invoke with a visitor
// in order to start the search.
fn collect_freevars(def_map: resolve::DefMap, blk: ast::blk)
-> freevar_info {
let seen = HashMap();
let refs = @mut ~[];
fn ignore_item(_i: @ast::item, &&_depth: int, _v: visit::vt<int>) { }
let walk_expr = fn@(expr: @ast::expr, &&depth: int, v: visit::vt<int>) {
match expr.node {
ast::expr_fn(proto, _, _, _) => {
if proto != ast::ProtoBare {
visit::visit_expr(expr, depth + 1, v);
}
}
ast::expr_fn_block(*) => {
visit::visit_expr(expr, depth + 1, v);
}
ast::expr_path(*) => {
let mut i = 0;
match def_map.find(expr.id) {
None => fail ~"path not found",
Some(df) => {
let mut def = df;
while i < depth {
match copy def {
ast::def_upvar(_, inner, _, _) => { def = *inner; }
_ => break
}
i += 1;
}
if i == depth { // Made it to end of loop
let dnum = ast_util::def_id_of_def(def).node;
if !seen.contains_key(dnum) {
refs.push(@{def:def, span:expr.span});
seen.insert(dnum, ());
}
}
}
}
}
_ => visit::visit_expr(expr, depth, v)
}
};
let v = visit::mk_vt(@{visit_item: ignore_item, visit_expr: walk_expr,
.. *visit::default_visitor()});
(v.visit_block)(blk, 1, v);
return @*refs;
}
// Build a map from every function and for-each body to a set of the
// freevars contained in it. The implementation is not particularly
// efficient as it fully recomputes the free variables at every
// node of interest rather than building up the free variables in
// one pass. This could be improved upon if it turns out to matter.
fn annotate_freevars(def_map: resolve::DefMap, crate: @ast::crate) ->
freevar_map {
let freevars = HashMap();
let walk_fn = fn@(_fk: visit::fn_kind, _decl: ast::fn_decl,
blk: ast::blk, _sp: span, nid: ast::node_id) {
let vars = collect_freevars(def_map, blk);
freevars.insert(nid, vars);
};
let visitor =
visit::mk_simple_visitor(@{visit_fn: walk_fn,
.. *visit::default_simple_visitor()});
visit::visit_crate(*crate, (), visitor);
return freevars;
}
fn get_freevars(tcx: ty::ctxt, fid: ast::node_id) -> freevar_info {
match tcx.freevars.find(fid) {
None => fail ~"get_freevars: " + int::str(fid) + ~" has no freevars",
Some(d) => return d
}
}
fn has_freevars(tcx: ty::ctxt, fid: ast::node_id) -> bool {
return vec::len(*get_freevars(tcx, fid)) != 0u;
}
// Local Variables:
// mode: rust
// fill-column: 78;
// indent-tabs-mode: nil
// c-basic-offset: 4
// buffer-file-coding-system: utf-8-unix
// End: