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Fix #2979: inference for lifetimes of & expressions

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What we now do is to create a region variable for each &
expression (and also each borrow).  The lifetime of this
variable will be checked by borrowck to ensure it is not greater
than the lifetime of the underlying data.  This both leads to
shorter lifetimes in some cases but also longer in others,
such as taking the address to the interior of unique boxes
tht are rooted in region pointers (e.g., returning a pointer
to the interior of a sendable map).

This may lead to issue #2977 if the rvalue is not POD, because
we may drop the data in trans sooner than borrowck expects us
to.  Need to work out precisely where that fix ought to occur.
This commit is contained in:
Niko Matsakis 2012-07-26 08:51:57 -07:00
parent 6ef13e76e9
commit 5d32d03b89
34 changed files with 717 additions and 320 deletions
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26
src/rustc/middle/astencode.rs
View file

@ -436,21 +436,6 @@ impl of tr for method_origin {
}
}
// ______________________________________________________________________
// Encoding and decoding of borrow
trait read_borrow_helper {
fn read_borrow(xcx: extended_decode_ctxt) -> ty::borrow;
}
impl helper of read_borrow_helper for ebml::ebml_deserializer {
fn read_borrow(xcx: extended_decode_ctxt) -> ty::borrow {
let borrow = ty::deserialize_borrow(self);
{scope_id: xcx.tr_id(borrow.scope_id),
mutbl: borrow.mutbl}
}
}
// ______________________________________________________________________
// Encoding and decoding vtable_res
@ -766,11 +751,13 @@ fn encode_side_tables_for_id(ecx: @e::encode_ctxt,
}
}
do option::iter(tcx.borrowings.find(id)) |borrow| {
do option::iter(tcx.borrowings.find(id)) |_borrow| {
do ebml_w.tag(c::tag_table_borrowings) {
ebml_w.id(id);
do ebml_w.tag(c::tag_table_val) {
ty::serialize_borrow(ebml_w, borrow)
// N.B. We don't actually serialize borrows as, in
// trans, we only care whether a value is borrowed or
// not.
}
}
}
@ -890,7 +877,10 @@ fn decode_side_tables(xcx: extended_decode_ctxt,
dcx.maps.vtable_map.insert(id,
val_dsr.read_vtable_res(xcx));
} else if tag == (c::tag_table_borrowings as uint) {
let borrow = val_dsr.read_borrow(xcx);
// N.B.: we don't actually *serialize* borrows because, in
// trans, the only thing we care about is whether a value was
// borrowed or not.
let borrow = {region: ty::re_static, mutbl: ast::m_imm};
dcx.tcx.borrowings.insert(id, borrow);
} else {
xcx.dcx.tcx.sess.bug(