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Improve handling of move and swap by alias checker

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Closes issue #541.
Closes issue #591
This commit is contained in:
Marijn Haverbeke 2011-07-07 10:21:14 +02:00
parent 130006cdda
commit 007a736642
1 changed files with 24 additions and 10 deletions
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34
src/comp/middle/alias.rs
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@ -14,14 +14,14 @@ import std::option::some;
import std::option::none;
import std::option::is_none;
// This is not an alias-analyser (though it would merit from becoming one, or
// at getting input from one, to be more precise). It is a pass that checks
// getting input from one, to be more precise). It is a pass that checks
// whether aliases are used in a safe way. Beyond that, though it doesn't have
// a lot to do with aliases, it also checks whether assignments are valid
// (using an lval, which is actually mutable), since it already has all the
// information needed to do that (and the typechecker, which would be a
// logical place for such a check, doesn't).
tag valid { valid; overwritten(span, ast::path); val_taken(span, ast::path); }
type restrict =
@ -40,12 +40,10 @@ type ctx = rec(@ty::ctxt tcx,
std::map::hashmap[node_id, local_info] local_map);
fn check_crate(@ty::ctxt tcx, &@ast::crate crate) {
auto cx =
@rec(tcx=tcx,
// Stores information about object fields and function
// arguments that's otherwise not easily available.
local_map=std::map::new_int_hash());
auto cx = @rec(tcx=tcx,
// Stores information about object fields and function
// arguments that's otherwise not easily available.
local_map=std::map::new_int_hash());
auto v =
@rec(visit_fn=bind visit_fn(cx, _, _, _, _, _, _, _),
visit_item=bind visit_item(cx, _, _, _),
@ -117,9 +115,11 @@ fn visit_expr(@ctx cx, &@ast::expr ex, &scope sc, &vt[scope] v) {
case (ast::expr_swap(?lhs, ?rhs)) {
check_lval(cx, lhs, sc, v);
check_lval(cx, rhs, sc, v);
handled = false;
}
case (ast::expr_move(?dest, ?src)) {
check_assign(cx, dest, src, sc, v);
check_move_rhs(cx, src, sc, v);
}
case (ast::expr_assign(?dest, ?src)) {
check_assign(cx, dest, src, sc, v);
@ -369,7 +369,6 @@ fn check_var(&ctx cx, &@ast::expr ex, &ast::path p, ast::node_id id,
auto my_defnum = ast::def_id_of_def(def)._1;
auto var_t = ty::expr_ty(*cx.tcx, ex);
for (restrict r in sc) {
// excludes variables introduced since the alias was made
if (my_defnum < r.block_defnum) {
for (ty::t t in r.tys) {
@ -399,7 +398,6 @@ fn check_lval(&@ctx cx, &@ast::expr dest, &scope sc, &vt[scope] v) {
r.ok = overwritten(dest.span, p);
}
}
check_var(*cx, dest, p, dest.id, true, sc);
}
case (_) {
auto root = expr_root(*cx, dest, false);
@ -420,6 +418,22 @@ fn check_lval(&@ctx cx, &@ast::expr dest, &scope sc, &vt[scope] v) {
}
}
fn check_move_rhs(&@ctx cx, &@ast::expr src, &scope sc, &vt[scope] v) {
alt (src.node) {
case (ast::expr_path(?p)) {
check_lval(cx, src, sc, v);
}
case (_) {
auto root = expr_root(*cx, src, false);
// Not a path and no-derefs means this is a temporary.
if (vec::len(root.ds) != 0u) {
cx.tcx.sess.span_err
(src.span, "moving out of a data structure");
}
}
}
}
fn check_assign(&@ctx cx, &@ast::expr dest, &@ast::expr src, &scope sc,
&vt[scope] v) {
visit_expr(cx, src, sc, v);