1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! Helper routines used for fragmenting structural paths due to moves for
12 //! tracking drop obligations. Please see the extensive comments in the
13 //! section "Structural fragments" in `doc.rs`.
15 use self::Fragment::*;
18 use middle::borrowck::{LoanPath};
19 use middle::borrowck::LoanPathKind::{LpVar, LpUpvar, LpDowncast, LpExtend};
20 use middle::borrowck::LoanPathElem::{LpDeref, LpInterior};
21 use middle::borrowck::move_data::{InvalidMovePathIndex};
22 use middle::borrowck::move_data::{MoveData, MovePathIndex};
24 use middle::mem_categorization as mc;
25 use util::ppaux::{Repr, UserString};
32 use syntax::attr::AttrMetaMethods;
33 use syntax::codemap::Span;
35 #[deriving(PartialEq, Eq, PartialOrd, Ord)]
37 // This represents the path described by the move path index
40 // This represents the collection of all but one of the elements
41 // from an array at the path described by the move path index.
42 // Note that attached MovePathIndex should have mem_categorization
43 // of InteriorElement (i.e. array dereference `[]`).
44 AllButOneFrom(MovePathIndex),
48 fn loan_path_repr<'tcx>(&self, move_data: &MoveData<'tcx>, tcx: &ty::ctxt<'tcx>) -> String {
49 let repr = |mpi| move_data.path_loan_path(mpi).repr(tcx);
51 Just(mpi) => repr(mpi),
52 AllButOneFrom(mpi) => format!("$(allbutone {})", repr(mpi)),
56 fn loan_path_user_string<'tcx>(&self,
57 move_data: &MoveData<'tcx>,
58 tcx: &ty::ctxt<'tcx>) -> String {
59 let user_string = |mpi| move_data.path_loan_path(mpi).user_string(tcx);
61 Just(mpi) => user_string(mpi),
62 AllButOneFrom(mpi) => format!("$(allbutone {})", user_string(mpi)),
67 pub struct FragmentSets {
68 /// During move_data construction, `moved_leaf_paths` tracks paths
69 /// that have been used directly by being moved out of. When
70 /// move_data construction has been completed, `moved_leaf_paths`
71 /// tracks such paths that are *leaf fragments* (e.g. `a.j` if we
72 /// never move out any child like `a.j.x`); any parent paths
73 /// (e.g. `a` for the `a.j` example) are moved over to
74 /// `parents_of_fragments`.
75 moved_leaf_paths: Vec<MovePathIndex>,
77 /// `assigned_leaf_paths` tracks paths that have been used
78 /// directly by being overwritten, but is otherwise much like
79 /// `moved_leaf_paths`.
80 assigned_leaf_paths: Vec<MovePathIndex>,
82 /// `parents_of_fragments` tracks paths that are definitely
83 /// parents of paths that have been moved.
85 /// FIXME(pnkfelix) probably do not want/need
86 /// `parents_of_fragments` at all, if we can avoid it.
88 /// Update: I do not see a way to to avoid it. Maybe just remove
89 /// above fixme, or at least document why doing this may be hard.
90 parents_of_fragments: Vec<MovePathIndex>,
92 /// During move_data construction (specifically the
93 /// fixup_fragment_sets call), `unmoved_fragments` tracks paths
94 /// that have been "left behind" after a sibling has been moved or
95 /// assigned. When move_data construction has been completed,
96 /// `unmoved_fragments` tracks paths that were *only* results of
97 /// being left-behind, and never directly moved themselves.
98 unmoved_fragments: Vec<Fragment>,
102 pub fn new() -> FragmentSets {
104 unmoved_fragments: Vec::new(),
105 moved_leaf_paths: Vec::new(),
106 assigned_leaf_paths: Vec::new(),
107 parents_of_fragments: Vec::new(),
111 pub fn add_move(&mut self, path_index: MovePathIndex) {
112 self.moved_leaf_paths.push(path_index);
115 pub fn add_assignment(&mut self, path_index: MovePathIndex) {
116 self.assigned_leaf_paths.push(path_index);
120 pub fn instrument_move_fragments<'tcx>(this: &MoveData<'tcx>,
121 tcx: &ty::ctxt<'tcx>,
124 let (span_err, print) = {
125 let attrs : &[ast::Attribute];
126 attrs = match tcx.map.find(id) {
127 Some(ast_map::NodeItem(ref item)) =>
128 item.attrs.as_slice(),
129 Some(ast_map::NodeImplItem(&ast::MethodImplItem(ref m))) =>
131 Some(ast_map::NodeTraitItem(&ast::ProvidedMethod(ref m))) =>
137 attrs.iter().any(|a| a.check_name("rustc_move_fragments"));
138 let print = tcx.sess.debugging_opt(config::PRINT_MOVE_FRAGMENTS);
143 if !span_err && !print { return; }
145 let instrument_all_paths = |kind, vec_rc: &Vec<MovePathIndex>| {
146 for (i, mpi) in vec_rc.iter().enumerate() {
147 let render = || this.path_loan_path(*mpi).user_string(tcx);
149 tcx.sess.span_err(sp, format!("{}: `{}`", kind, render()).as_slice());
152 println!("id:{} {}[{}] `{}`", id, kind, i, render());
157 let instrument_all_fragments = |kind, vec_rc: &Vec<Fragment>| {
158 for (i, f) in vec_rc.iter().enumerate() {
159 let render = || f.loan_path_user_string(this, tcx);
161 tcx.sess.span_err(sp, format!("{}: `{}`", kind, render()).as_slice());
164 println!("id:{} {}[{}] `{}`", id, kind, i, render());
169 let fragments = this.fragments.borrow();
170 instrument_all_paths("moved_leaf_path", &fragments.moved_leaf_paths);
171 instrument_all_fragments("unmoved_fragment", &fragments.unmoved_fragments);
172 instrument_all_paths("parent_of_fragments", &fragments.parents_of_fragments);
173 instrument_all_paths("assigned_leaf_path", &fragments.assigned_leaf_paths);
176 /// Normalizes the fragment sets in `this`; i.e., removes duplicate entries, constructs the set of
177 /// parents, and constructs the left-over fragments.
179 /// Note: "left-over fragments" means paths that were not directly referenced in moves nor
180 /// assignments, but must nonetheless be tracked as potential drop obligations.
181 pub fn fixup_fragment_sets<'tcx>(this: &MoveData<'tcx>, tcx: &ty::ctxt<'tcx>) {
183 let mut fragments = this.fragments.borrow_mut();
185 // Swap out contents of fragments so that we can modify the fields
186 // without borrowing the common fragments.
187 let mut unmoved = mem::replace(&mut fragments.unmoved_fragments, vec![]);
188 let mut parents = mem::replace(&mut fragments.parents_of_fragments, vec![]);
189 let mut moved = mem::replace(&mut fragments.moved_leaf_paths, vec![]);
190 let mut assigned = mem::replace(&mut fragments.assigned_leaf_paths, vec![]);
192 let path_lps = |mpis: &[MovePathIndex]| -> Vec<String> {
193 mpis.iter().map(|mpi| this.path_loan_path(*mpi).repr(tcx)).collect()
196 let frag_lps = |fs: &[Fragment]| -> Vec<String> {
197 fs.iter().map(|f| f.loan_path_repr(this, tcx)).collect()
200 // First, filter out duplicates
203 debug!("fragments 1 moved: {}", path_lps(moved.as_slice()));
207 debug!("fragments 1 assigned: {}", path_lps(assigned.as_slice()));
209 // Second, build parents from the moved and assigned.
210 for m in moved.iter() {
211 let mut p = this.path_parent(*m);
212 while p != InvalidMovePathIndex {
214 p = this.path_parent(p);
217 for a in assigned.iter() {
218 let mut p = this.path_parent(*a);
219 while p != InvalidMovePathIndex {
221 p = this.path_parent(p);
227 debug!("fragments 2 parents: {}", path_lps(parents.as_slice()));
229 // Third, filter the moved and assigned fragments down to just the non-parents
230 moved.retain(|f| non_member(*f, parents.as_slice()));
231 debug!("fragments 3 moved: {}", path_lps(moved.as_slice()));
233 assigned.retain(|f| non_member(*f, parents.as_slice()));
234 debug!("fragments 3 assigned: {}", path_lps(assigned.as_slice()));
236 // Fourth, build the leftover from the moved, assigned, and parents.
237 for m in moved.iter() {
238 let lp = this.path_loan_path(*m);
239 add_fragment_siblings(this, tcx, &mut unmoved, lp, None);
241 for a in assigned.iter() {
242 let lp = this.path_loan_path(*a);
243 add_fragment_siblings(this, tcx, &mut unmoved, lp, None);
245 for p in parents.iter() {
246 let lp = this.path_loan_path(*p);
247 add_fragment_siblings(this, tcx, &mut unmoved, lp, None);
252 debug!("fragments 4 unmoved: {}", frag_lps(unmoved.as_slice()));
254 // Fifth, filter the leftover fragments down to its core.
255 unmoved.retain(|f| match *f {
256 AllButOneFrom(_) => true,
257 Just(mpi) => non_member(mpi, parents.as_slice()) &&
258 non_member(mpi, moved.as_slice()) &&
259 non_member(mpi, assigned.as_slice())
261 debug!("fragments 5 unmoved: {}", frag_lps(unmoved.as_slice()));
263 // Swap contents back in.
264 fragments.unmoved_fragments = unmoved;
265 fragments.parents_of_fragments = parents;
266 fragments.moved_leaf_paths = moved;
267 fragments.assigned_leaf_paths = assigned;
271 fn non_member(elem: MovePathIndex, set: &[MovePathIndex]) -> bool {
272 match set.binary_search_elem(&elem) {
273 slice::BinarySearchResult::Found(_) => false,
274 slice::BinarySearchResult::NotFound(_) => true,
279 /// Adds all of the precisely-tracked siblings of `lp` as potential move paths of interest. For
280 /// example, if `lp` represents `s.x.j`, then adds moves paths for `s.x.i` and `s.x.k`, the
281 /// siblings of `s.x.j`.
282 fn add_fragment_siblings<'tcx>(this: &MoveData<'tcx>,
283 tcx: &ty::ctxt<'tcx>,
284 gathered_fragments: &mut Vec<Fragment>,
285 lp: Rc<LoanPath<'tcx>>,
286 origin_id: Option<ast::NodeId>) {
288 LpVar(_) | LpUpvar(..) => {} // Local variables have no siblings.
290 // Consuming a downcast is like consuming the original value, so propage inward.
291 LpDowncast(ref loan_parent, _) => {
292 add_fragment_siblings(this, tcx, gathered_fragments, loan_parent.clone(), origin_id);
295 // *LV for OwnedPtr consumes the contents of the box (at
296 // least when it is non-copy...), so propagate inward.
297 LpExtend(ref loan_parent, _, LpDeref(mc::OwnedPtr)) => {
298 add_fragment_siblings(this, tcx, gathered_fragments, loan_parent.clone(), origin_id);
301 // *LV for unsafe and borrowed pointers do not consume their loan path, so stop here.
302 LpExtend(_, _, LpDeref(mc::UnsafePtr(..))) |
303 LpExtend(_, _, LpDeref(mc::Implicit(..))) |
304 LpExtend(_, _, LpDeref(mc::BorrowedPtr(..))) => {}
306 // FIXME(pnkfelix): LV[j] should be tracked, at least in the
307 // sense of we will track the remaining drop obligation of the
308 // rest of the array.
310 // LV[j] is not tracked precisely
311 LpExtend(_, _, LpInterior(mc::InteriorElement(_))) => {
312 let mp = this.move_path(tcx, lp.clone());
313 gathered_fragments.push(AllButOneFrom(mp));
316 // field access LV.x and tuple access LV#k are the cases
317 // we are interested in
318 LpExtend(ref loan_parent, mc,
319 LpInterior(mc::InteriorField(ref field_name))) => {
320 let enum_variant_info = match loan_parent.kind {
321 LpDowncast(ref loan_parent_2, variant_def_id) =>
322 Some((variant_def_id, loan_parent_2.clone())),
323 LpExtend(..) | LpVar(..) | LpUpvar(..) =>
326 add_fragment_siblings_for_extension(
330 loan_parent, mc, field_name, &lp, origin_id, enum_variant_info);
335 /// We have determined that `origin_lp` destructures to LpExtend(parent, original_field_name).
336 /// Based on this, add move paths for all of the siblings of `origin_lp`.
337 fn add_fragment_siblings_for_extension<'tcx>(this: &MoveData<'tcx>,
338 tcx: &ty::ctxt<'tcx>,
339 gathered_fragments: &mut Vec<Fragment>,
340 parent_lp: &Rc<LoanPath<'tcx>>,
341 mc: mc::MutabilityCategory,
342 origin_field_name: &mc::FieldName,
343 origin_lp: &Rc<LoanPath<'tcx>>,
344 origin_id: Option<ast::NodeId>,
345 enum_variant_info: Option<(ast::DefId,
346 Rc<LoanPath<'tcx>>)>) {
347 let parent_ty = parent_lp.to_type();
349 let add_fragment_sibling_local = |field_name, variant_did| {
350 add_fragment_sibling_core(
351 this, tcx, gathered_fragments, parent_lp.clone(), mc, field_name, origin_lp,
355 match (&parent_ty.sty, enum_variant_info) {
356 (&ty::ty_tup(ref v), None) => {
357 let tuple_idx = match *origin_field_name {
358 mc::PositionalField(tuple_idx) => tuple_idx,
360 panic!("tuple type {} should not have named fields.",
361 parent_ty.repr(tcx)),
363 let tuple_len = v.len();
364 for i in range(0, tuple_len) {
365 if i == tuple_idx { continue }
366 let field_name = mc::PositionalField(i);
367 add_fragment_sibling_local(field_name, None);
371 (&ty::ty_struct(def_id, ref _substs), None) => {
372 let fields = ty::lookup_struct_fields(tcx, def_id);
373 match *origin_field_name {
374 mc::NamedField(ast_name) => {
375 for f in fields.iter() {
376 if f.name == ast_name {
379 let field_name = mc::NamedField(f.name);
380 add_fragment_sibling_local(field_name, None);
383 mc::PositionalField(tuple_idx) => {
384 for (i, _f) in fields.iter().enumerate() {
388 let field_name = mc::PositionalField(i);
389 add_fragment_sibling_local(field_name, None);
395 (&ty::ty_enum(enum_def_id, ref substs), ref enum_variant_info) => {
397 let mut variants = ty::substd_enum_variants(tcx, enum_def_id, substs);
398 match *enum_variant_info {
399 Some((variant_def_id, ref _lp2)) =>
401 .find(|variant| variant.id == variant_def_id)
402 .expect("enum_variant_with_id(): no variant exists with that ID")
405 assert_eq!(variants.len(), 1);
406 variants.pop().unwrap()
410 match *origin_field_name {
411 mc::NamedField(ast_name) => {
412 let variant_arg_names = variant_info.arg_names.as_ref().unwrap();
413 for variant_arg_ident in variant_arg_names.iter() {
414 if variant_arg_ident.name == ast_name {
417 let field_name = mc::NamedField(variant_arg_ident.name);
418 add_fragment_sibling_local(field_name, Some(variant_info.id));
421 mc::PositionalField(tuple_idx) => {
422 let variant_arg_types = &variant_info.args;
423 for (i, _variant_arg_ty) in variant_arg_types.iter().enumerate() {
427 let field_name = mc::PositionalField(i);
428 add_fragment_sibling_local(field_name, None);
434 ref sty_and_variant_info => {
435 let msg = format!("type {} ({}) is not fragmentable",
436 parent_ty.repr(tcx), sty_and_variant_info);
437 let opt_span = origin_id.and_then(|id|tcx.map.opt_span(id));
438 tcx.sess.opt_span_bug(opt_span, msg.as_slice())
443 /// Adds the single sibling `LpExtend(parent, new_field_name)` of `origin_lp` (the original
445 fn add_fragment_sibling_core<'tcx>(this: &MoveData<'tcx>,
446 tcx: &ty::ctxt<'tcx>,
447 gathered_fragments: &mut Vec<Fragment>,
448 parent: Rc<LoanPath<'tcx>>,
449 mc: mc::MutabilityCategory,
450 new_field_name: mc::FieldName,
451 origin_lp: &Rc<LoanPath<'tcx>>,
452 enum_variant_did: Option<ast::DefId>) -> MovePathIndex {
453 let opt_variant_did = match parent.kind {
454 LpDowncast(_, variant_did) => Some(variant_did),
455 LpVar(..) | LpUpvar(..) | LpExtend(..) => enum_variant_did,
458 let loan_path_elem = LpInterior(mc::InteriorField(new_field_name));
459 let new_lp_type = match new_field_name {
460 mc::NamedField(ast_name) =>
461 ty::named_element_ty(tcx, parent.to_type(), ast_name, opt_variant_did),
462 mc::PositionalField(idx) =>
463 ty::positional_element_ty(tcx, parent.to_type(), idx, opt_variant_did),
465 let new_lp_variant = LpExtend(parent, mc, loan_path_elem);
466 let new_lp = LoanPath::new(new_lp_variant, new_lp_type.unwrap());
467 debug!("add_fragment_sibling_core(new_lp={}, origin_lp={})",
468 new_lp.repr(tcx), origin_lp.repr(tcx));
469 let mp = this.move_path(tcx, Rc::new(new_lp));
471 // Do not worry about checking for duplicates here; we will sort
472 // and dedup after all are added.
473 gathered_fragments.push(Just(mp));