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Implement basic checking of by-reference bindings

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Issue #918
This commit is contained in:
Marijn Haverbeke 2011-09-15 13:40:28 +02:00
parent 44c6370e6a
commit 8aad16112b
1 changed files with 57 additions and 3 deletions
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60
src/comp/middle/alias.rs
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@ -22,6 +22,7 @@ type binding = @{node_id: node_id,
unsafe_tys: [ty::t],
mutable ok: valid,
mutable copied: copied};
// FIXME it may be worthwhile to use a linked list of bindings instead
type scope = {bs: [binding], ret_style: ast::ret_style};
fn mk_binding(cx: ctx, id: node_id, span: span, root_var: option::t<node_id>,
@ -46,7 +47,8 @@ fn check_crate(tcx: ty::ctxt, crate: @ast::crate) -> copy_map {
copy_map: std::map::new_int_hash()};
let v = @{visit_fn: bind visit_fn(cx, _, _, _, _, _, _, _),
visit_expr: bind visit_expr(cx, _, _, _),
visit_decl: bind visit_decl(cx, _, _, _)
visit_decl: bind visit_decl(cx, _, _, _),
visit_block: bind visit_block(cx, _, _, _)
with *visit::default_visitor::<scope>()};
visit::visit_crate(*crate, {bs: [], ret_style: ast::return_val},
visit::mk_vt(v));
@ -134,8 +136,7 @@ fn visit_decl(cx: @ctx, d: @ast::decl, sc: scope, v: vt<scope>) {
visit::visit_decl(d, sc, v);
alt d.node {
ast::decl_local(locs) {
// FIXME check that init is lvalue
for (style, loc) in locs {
for (_, loc) in locs {
alt loc.node.init {
some(init) {
if init.op == ast::init_move {
@ -150,6 +151,59 @@ fn visit_decl(cx: @ctx, d: @ast::decl, sc: scope, v: vt<scope>) {
}
}
fn visit_block(cx: @ctx, b: ast::blk, sc: scope, v: vt<scope>) {
let ref_locs = [];
for stmt in b.node.stmts {
alt stmt.node {
ast::stmt_decl(@{node: ast::decl_local(ls), _}, _) {
for (st, loc) in ls {
if st == ast::let_ref {
ref_locs += [loc];
}
}
}
_ {}
}
}
if vec::len(ref_locs) > 0u {
let bindings = sc.bs;
for loc in ref_locs { add_bindings_for_let(*cx, bindings, loc); }
visit::visit_block(b, {bs: bindings with sc}, v);
} else {
visit::visit_block(b, sc, v);
}
}
fn add_bindings_for_let(cx: ctx, &bs: [binding], loc: @ast::local) {
alt loc.node.init {
some(init) {
if init.op == ast::init_move {
cx.tcx.sess.span_err
(loc.span, "can not move into a by-reference binding");
}
let root = expr_root(cx.tcx, init.expr, false);
let root_var = path_def_id(cx, root.ex);
// FIXME also allow by-ref function calls
if is_none(root_var) {
cx.tcx.sess.span_err(loc.span, "a reference binding can't be \
rooted in a temporary");
}
for proot in *pattern_roots(cx.tcx, *root.ds, loc.node.pat) {
let bnd = mk_binding(cx, proot.id, proot.span, root_var,
inner_mut(proot.ds));
// Don't implicitly copy explicit references
bnd.copied = not_allowed;
bs += [bnd];
}
}
_ {
cx.tcx.sess.span_err
(loc.span, "by-reference bindings must be initialized");
}
}
}
fn cant_copy(cx: ctx, b: binding) -> bool {
alt b.copied {
not_allowed. { ret true; }