mirror of
https://github.com/rust-lang/rust.git
synced 2024-11-01 06:51:58 +00:00
Treat enums with one variant specially in borrowck: #2573
This commit is contained in:
parent
1655c1a825
commit
d1ec1d4abb
@ -238,11 +238,13 @@ enum ptr_kind {uniq_ptr, gc_ptr, region_ptr, unsafe_ptr}
|
||||
// I am coining the term "components" to mean "pieces of a data
|
||||
// structure accessible without a dereference":
|
||||
enum comp_kind {
|
||||
comp_tuple, comp_res, comp_variant,
|
||||
comp_field(str, // name of field
|
||||
comp_tuple, // elt in a tuple
|
||||
comp_res, // data for a resource
|
||||
comp_variant(ast::def_id), // internals to a variant of given enum
|
||||
comp_field(str, // name of field
|
||||
ast::mutability), // declared mutability of field
|
||||
comp_index(ty::t, // type of vec/str/etc being deref'd
|
||||
ast::mutability) // mutability of vec content
|
||||
comp_index(ty::t, // type of vec/str/etc being deref'd
|
||||
ast::mutability) // mutability of vec content
|
||||
}
|
||||
|
||||
// We pun on *T to mean both actual deref of a ptr as well
|
||||
@ -411,7 +413,7 @@ impl to_str_methods for borrowck_ctxt {
|
||||
comp_index(*) { "[]" }
|
||||
comp_tuple { "()" }
|
||||
comp_res { "<res>" }
|
||||
comp_variant { "<enum>" }
|
||||
comp_variant(_) { "<enum>" }
|
||||
}
|
||||
}
|
||||
|
||||
@ -468,7 +470,7 @@ impl to_str_methods for borrowck_ctxt {
|
||||
cat_comp(_, comp_field(*)) { mut_str + " field" }
|
||||
cat_comp(_, comp_tuple) { "tuple content" }
|
||||
cat_comp(_, comp_res) { "resource content" }
|
||||
cat_comp(_, comp_variant) { "enum content" }
|
||||
cat_comp(_, comp_variant(_)) { "enum content" }
|
||||
cat_comp(_, comp_index(t, _)) {
|
||||
alt ty::get(t).struct {
|
||||
ty::ty_vec(*) | ty::ty_evec(*) {
|
||||
@ -514,7 +516,7 @@ impl to_str_methods for borrowck_ctxt {
|
||||
// mutable structure.
|
||||
fn inherent_mutability(ck: comp_kind) -> mutability {
|
||||
alt ck {
|
||||
comp_tuple | comp_res | comp_variant {m_imm}
|
||||
comp_tuple | comp_res | comp_variant(_) {m_imm}
|
||||
comp_field(_, m) | comp_index(_, m) {m}
|
||||
}
|
||||
}
|
@ -67,8 +67,8 @@ fn opt_deref_kind(t: ty::t) -> option<deref_kind> {
|
||||
some(deref_ptr(unsafe_ptr))
|
||||
}
|
||||
|
||||
ty::ty_enum(*) {
|
||||
some(deref_comp(comp_variant))
|
||||
ty::ty_enum(did, _) {
|
||||
some(deref_comp(comp_variant(did)))
|
||||
}
|
||||
|
||||
ty::ty_res(*) {
|
||||
@ -275,10 +275,12 @@ impl public_methods for borrowck_ctxt {
|
||||
}
|
||||
}
|
||||
|
||||
fn cat_variant<N: ast_node>(arg: N, cmt: cmt) -> cmt {
|
||||
fn cat_variant<N: ast_node>(arg: N,
|
||||
enum_did: ast::def_id,
|
||||
cmt: cmt) -> cmt {
|
||||
@{id: arg.id(), span: arg.span(),
|
||||
cat: cat_comp(cmt, comp_variant),
|
||||
lp: cmt.lp.map { |l| @lp_comp(l, comp_variant) },
|
||||
cat: cat_comp(cmt, comp_variant(enum_did)),
|
||||
lp: cmt.lp.map { |l| @lp_comp(l, comp_variant(enum_did)) },
|
||||
mutbl: cmt.mutbl, // imm iff in an immutable context
|
||||
ty: self.tcx.ty(arg)}
|
||||
}
|
||||
|
@ -338,8 +338,16 @@ impl methods for gather_loan_ctxt {
|
||||
}
|
||||
ast::pat_enum(_, some(subpats)) {
|
||||
// variant(x, y, z)
|
||||
let enum_did = alt self.bccx.tcx.def_map
|
||||
.find(pat.id) {
|
||||
some(ast::def_variant(enum_did, _)) {enum_did}
|
||||
e {tcx.sess.span_bug(pat.span,
|
||||
#fmt["resolved to %?, \
|
||||
not variant", e])}
|
||||
};
|
||||
|
||||
for subpats.each { |subpat|
|
||||
let subcmt = self.bccx.cat_variant(subpat, cmt);
|
||||
let subcmt = self.bccx.cat_variant(subpat, enum_did, cmt);
|
||||
self.gather_pat(subcmt, subpat, arm_id, alt_id);
|
||||
}
|
||||
}
|
||||
|
@ -65,24 +65,23 @@ impl loan_methods for loan_ctxt {
|
||||
// that case, it must also be embedded in an immutable
|
||||
// location, or else the whole structure could be
|
||||
// overwritten and the component along with it.
|
||||
let base_mutbl = alt req_mutbl {
|
||||
m_imm { m_imm }
|
||||
m_const | m_mutbl { m_const }
|
||||
};
|
||||
|
||||
self.loan(cmt_base, base_mutbl);
|
||||
self.ok_with_loan_of(cmt, req_mutbl)
|
||||
self.loan_stable_comp(cmt, cmt_base, req_mutbl)
|
||||
}
|
||||
cat_comp(cmt1, comp_variant) |
|
||||
cat_deref(cmt1, _, uniq_ptr) {
|
||||
// Variant components: the base must be immutable, because
|
||||
// if it is overwritten, the types of the embedded data
|
||||
// could change.
|
||||
//
|
||||
// Unique pointers: the base must be immutable, because if
|
||||
// it is overwritten, the unique content will be freed.
|
||||
self.loan(cmt1, m_imm);
|
||||
self.ok_with_loan_of(cmt, req_mutbl)
|
||||
cat_comp(cmt_base, comp_variant(enum_did)) {
|
||||
// For enums, the memory is unstable if there are multiple
|
||||
// variants, because if the enum value is overwritten then
|
||||
// the memory changes type.
|
||||
if ty::enum_is_univariant(self.bccx.tcx, enum_did) {
|
||||
self.loan_stable_comp(cmt, cmt_base, req_mutbl)
|
||||
} else {
|
||||
self.loan_unstable_deref(cmt, cmt_base, req_mutbl)
|
||||
}
|
||||
}
|
||||
cat_deref(cmt_base, _, uniq_ptr) {
|
||||
// For unique pointers, the memory being pointed out is
|
||||
// unstable because if the unique pointer is overwritten
|
||||
// then the memory is freed.
|
||||
self.loan_unstable_deref(cmt, cmt_base, req_mutbl)
|
||||
}
|
||||
cat_deref(cmt1, _, unsafe_ptr) |
|
||||
cat_deref(cmt1, _, gc_ptr) |
|
||||
@ -94,4 +93,32 @@ impl loan_methods for loan_ctxt {
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// A "stable component" is one where assigning the base of the
|
||||
// component cannot cause the component itself to change types.
|
||||
// Example: record fields.
|
||||
fn loan_stable_comp(cmt: cmt,
|
||||
cmt_base: cmt,
|
||||
req_mutbl: ast::mutability) {
|
||||
let base_mutbl = alt req_mutbl {
|
||||
m_imm { m_imm }
|
||||
m_const | m_mutbl { m_const }
|
||||
};
|
||||
|
||||
self.loan(cmt_base, base_mutbl);
|
||||
self.ok_with_loan_of(cmt, req_mutbl)
|
||||
}
|
||||
|
||||
// An "unstable deref" means a deref of a ptr/comp where, if the
|
||||
// base of the deref is assigned to, pointers into the result of the
|
||||
// deref would be invalidated. Examples: interior of variants, uniques.
|
||||
fn loan_unstable_deref(cmt: cmt,
|
||||
cmt_base: cmt,
|
||||
req_mutbl: ast::mutability) {
|
||||
// Variant components: the base must be immutable, because
|
||||
// if it is overwritten, the types of the embedded data
|
||||
// could change.
|
||||
self.loan(cmt_base, m_imm);
|
||||
self.ok_with_loan_of(cmt, req_mutbl)
|
||||
}
|
||||
}
|
||||
|
@ -43,10 +43,19 @@ impl public_methods for borrowck_ctxt {
|
||||
// type never changes.
|
||||
self.preserve(cmt_base, opt_scope_id)
|
||||
}
|
||||
cat_comp(cmt_base, comp_variant) {
|
||||
self.require_imm(cmt, cmt_base, opt_scope_id, err_mut_variant)
|
||||
cat_comp(cmt_base, comp_variant(enum_did)) {
|
||||
if ty::enum_is_univariant(self.tcx, enum_did) {
|
||||
self.preserve(cmt_base, opt_scope_id)
|
||||
} else {
|
||||
// If there are multiple variants: overwriting the
|
||||
// base could cause the type of this memory to change,
|
||||
// so require imm.
|
||||
self.require_imm(cmt, cmt_base, opt_scope_id, err_mut_variant)
|
||||
}
|
||||
}
|
||||
cat_deref(cmt_base, _, uniq_ptr) {
|
||||
// Overwriting the base could cause this memory to be
|
||||
// freed, so require imm.
|
||||
self.require_imm(cmt, cmt_base, opt_scope_id, err_mut_uniq)
|
||||
}
|
||||
cat_deref(_, _, region_ptr) {
|
||||
|
@ -68,7 +68,7 @@ export sty;
|
||||
export subst, subst_tps, substs_is_noop, substs_to_str, substs;
|
||||
export t;
|
||||
export new_ty_hash;
|
||||
export enum_variants, substd_enum_variants;
|
||||
export enum_variants, substd_enum_variants, enum_is_univariant;
|
||||
export iface_methods, store_iface_methods, impl_iface;
|
||||
export enum_variant_with_id;
|
||||
export ty_dtor;
|
||||
@ -2663,6 +2663,10 @@ fn item_path(cx: ctxt, id: ast::def_id) -> ast_map::path {
|
||||
}
|
||||
}
|
||||
|
||||
fn enum_is_univariant(cx: ctxt, id: ast::def_id) -> bool {
|
||||
vec::len(*enum_variants(cx, id)) == 1u
|
||||
}
|
||||
|
||||
fn enum_variants(cx: ctxt, id: ast::def_id) -> @[variant_info] {
|
||||
alt cx.enum_var_cache.find(id) {
|
||||
some(variants) { ret variants; }
|
||||
|
16
src/test/run-pass/borrowck-newtype-issue-2573.rs
Normal file
16
src/test/run-pass/borrowck-newtype-issue-2573.rs
Normal file
@ -0,0 +1,16 @@
|
||||
enum foo = {mut bar: baz};
|
||||
|
||||
enum baz = @{mut baz: int};
|
||||
|
||||
impl quuux for foo {
|
||||
fn frob() {
|
||||
really_impure(self.bar);
|
||||
}
|
||||
}
|
||||
|
||||
// Override default mode so that we are passing by value
|
||||
fn really_impure(++bar: baz) {
|
||||
bar.baz = 3;
|
||||
}
|
||||
|
||||
fn main() {}
|
19
src/test/run-pass/borrowck-univariant-enum.rs
Normal file
19
src/test/run-pass/borrowck-univariant-enum.rs
Normal file
@ -0,0 +1,19 @@
|
||||
enum newtype {
|
||||
newtype(int)
|
||||
}
|
||||
|
||||
fn main() {
|
||||
|
||||
// Test that borrowck treats enums with a single variant
|
||||
// specially.
|
||||
|
||||
let x = @mut 5;
|
||||
let y = @mut newtype(3);
|
||||
let z = alt *y {
|
||||
newtype(b) {
|
||||
*x += 1;
|
||||
*x * b
|
||||
}
|
||||
};
|
||||
assert z == 18;
|
||||
}
|
Loading…
Reference in New Issue
Block a user