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 //! This file builds up the `ScopeTree`, which describes
12 //! the parent links in the region hierarchy.
14 //! Most of the documentation on regions can be found in
15 //! `middle/infer/region_inference/README.md`
17 use ich::{StableHashingContext, NodeIdHashingMode};
18 use util::nodemap::{FxHashMap, FxHashSet};
26 use syntax_pos::{Span, DUMMY_SP};
28 use ty::maps::Providers;
31 use hir::def_id::DefId;
32 use hir::intravisit::{self, Visitor, NestedVisitorMap};
33 use hir::{Block, Arm, Pat, PatKind, Stmt, Expr, Local};
34 use rustc_data_structures::indexed_vec::Idx;
35 use rustc_data_structures::stable_hasher::{HashStable, StableHasher,
38 /// Scope represents a statically-describable scope that can be
39 /// used to bound the lifetime/region for values.
41 /// `Node(node_id)`: Any AST node that has any scope at all has the
42 /// `Node(node_id)` scope. Other variants represent special cases not
43 /// immediately derivable from the abstract syntax tree structure.
45 /// `DestructionScope(node_id)` represents the scope of destructors
46 /// implicitly-attached to `node_id` that run immediately after the
47 /// expression for `node_id` itself. Not every AST node carries a
48 /// `DestructionScope`, but those that are `terminating_scopes` do;
49 /// see discussion with `ScopeTree`.
51 /// `Remainder(BlockRemainder { block, statement_index })` represents
52 /// the scope of user code running immediately after the initializer
53 /// expression for the indexed statement, until the end of the block.
55 /// So: the following code can be broken down into the scopes beneath:
57 /// let a = f().g( 'b: { let x = d(); let y = d(); x.h(y) } ) ;
62 /// +---------+ (R10.)
64 /// +----------+ (M8.)
65 /// +----------------------+ (R7.)
67 /// +----------+ (M5.)
68 /// +-----------------------------------+ (M4.)
69 /// +--------------------------------------------------+ (M3.)
71 /// +-----------------------------------------------------------+ (M1.)
73 /// (M1.): Node scope of the whole `let a = ...;` statement.
74 /// (M2.): Node scope of the `f()` expression.
75 /// (M3.): Node scope of the `f().g(..)` expression.
76 /// (M4.): Node scope of the block labeled `'b:`.
77 /// (M5.): Node scope of the `let x = d();` statement
78 /// (D6.): DestructionScope for temporaries created during M5.
79 /// (R7.): Remainder scope for block `'b:`, stmt 0 (let x = ...).
80 /// (M8.): Node scope of the `let y = d();` statement.
81 /// (D9.): DestructionScope for temporaries created during M8.
82 /// (R10.): Remainder scope for block `'b:`, stmt 1 (let y = ...).
83 /// (D11.): DestructionScope for temporaries and bindings from block `'b:`.
84 /// (D12.): DestructionScope for temporaries created during M1 (e.g. f()).
86 /// Note that while the above picture shows the destruction scopes
87 /// as following their corresponding node scopes, in the internal
88 /// data structures of the compiler the destruction scopes are
89 /// represented as enclosing parents. This is sound because we use the
90 /// enclosing parent relationship just to ensure that referenced
91 /// values live long enough; phrased another way, the starting point
92 /// of each range is not really the important thing in the above
93 /// picture, but rather the ending point.
95 /// FIXME (pnkfelix): This currently derives `PartialOrd` and `Ord` to
96 /// placate the same deriving in `ty::FreeRegion`, but we may want to
97 /// actually attach a more meaningful ordering to scopes than the one
98 /// generated via deriving here.
100 /// Scope is a bit-packed to save space - if `code` is SCOPE_DATA_REMAINDER_MAX
101 /// or less, it is a `ScopeData::Remainder`, otherwise it is a type specified
102 /// by the bitpacking.
103 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, Copy, RustcEncodable, RustcDecodable)]
105 pub(crate) id: hir::ItemLocalId,
109 const SCOPE_DATA_NODE: u32 = !0;
110 const SCOPE_DATA_CALLSITE: u32 = !1;
111 const SCOPE_DATA_ARGUMENTS: u32 = !2;
112 const SCOPE_DATA_DESTRUCTION: u32 = !3;
113 const SCOPE_DATA_REMAINDER_MAX: u32 = !4;
115 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, Debug, Copy, RustcEncodable, RustcDecodable)]
117 Node(hir::ItemLocalId),
119 // Scope of the call-site for a function or closure
120 // (outlives the arguments as well as the body).
121 CallSite(hir::ItemLocalId),
123 // Scope of arguments passed to a function or closure
124 // (they outlive its body).
125 Arguments(hir::ItemLocalId),
127 // Scope of destructors for temporaries of node-id.
128 Destruction(hir::ItemLocalId),
130 // Scope following a `let id = expr;` binding in a block.
131 Remainder(BlockRemainder)
134 /// Represents a subscope of `block` for a binding that is introduced
135 /// by `block.stmts[first_statement_index]`. Such subscopes represent
136 /// a suffix of the block. Note that each subscope does not include
137 /// the initializer expression, if any, for the statement indexed by
138 /// `first_statement_index`.
140 /// For example, given `{ let (a, b) = EXPR_1; let c = EXPR_2; ... }`:
142 /// * the subscope with `first_statement_index == 0` is scope of both
143 /// `a` and `b`; it does not include EXPR_1, but does include
144 /// everything after that first `let`. (If you want a scope that
145 /// includes EXPR_1 as well, then do not use `Scope::Remainder`,
146 /// but instead another `Scope` that encompasses the whole block,
147 /// e.g. `Scope::Node`.
149 /// * the subscope with `first_statement_index == 1` is scope of `c`,
150 /// and thus does not include EXPR_2, but covers the `...`.
151 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, RustcEncodable,
152 RustcDecodable, Debug, Copy)]
153 pub struct BlockRemainder {
154 pub block: hir::ItemLocalId,
155 pub first_statement_index: FirstStatementIndex,
158 newtype_index!(FirstStatementIndex
161 MAX = SCOPE_DATA_REMAINDER_MAX
164 impl From<ScopeData> for Scope {
166 fn from(scope_data: ScopeData) -> Self {
167 let (id, code) = match scope_data {
168 ScopeData::Node(id) => (id, SCOPE_DATA_NODE),
169 ScopeData::CallSite(id) => (id, SCOPE_DATA_CALLSITE),
170 ScopeData::Arguments(id) => (id, SCOPE_DATA_ARGUMENTS),
171 ScopeData::Destruction(id) => (id, SCOPE_DATA_DESTRUCTION),
172 ScopeData::Remainder(r) => (r.block, r.first_statement_index.index() as u32)
178 impl fmt::Debug for Scope {
179 fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
180 fmt::Debug::fmt(&self.data(), formatter)
184 #[allow(non_snake_case)]
187 pub fn data(self) -> ScopeData {
189 SCOPE_DATA_NODE => ScopeData::Node(self.id),
190 SCOPE_DATA_CALLSITE => ScopeData::CallSite(self.id),
191 SCOPE_DATA_ARGUMENTS => ScopeData::Arguments(self.id),
192 SCOPE_DATA_DESTRUCTION => ScopeData::Destruction(self.id),
193 idx => ScopeData::Remainder(BlockRemainder {
195 first_statement_index: FirstStatementIndex::new(idx as usize)
201 pub fn Node(id: hir::ItemLocalId) -> Self {
202 Self::from(ScopeData::Node(id))
206 pub fn CallSite(id: hir::ItemLocalId) -> Self {
207 Self::from(ScopeData::CallSite(id))
211 pub fn Arguments(id: hir::ItemLocalId) -> Self {
212 Self::from(ScopeData::Arguments(id))
216 pub fn Destruction(id: hir::ItemLocalId) -> Self {
217 Self::from(ScopeData::Destruction(id))
221 pub fn Remainder(r: BlockRemainder) -> Self {
222 Self::from(ScopeData::Remainder(r))
227 /// Returns a item-local id associated with this scope.
229 /// NB: likely to be replaced as API is refined; e.g. pnkfelix
230 /// anticipates `fn entry_node_id` and `fn each_exit_node_id`.
231 pub fn item_local_id(&self) -> hir::ItemLocalId {
235 pub fn node_id(&self, tcx: TyCtxt, scope_tree: &ScopeTree) -> ast::NodeId {
236 match scope_tree.root_body {
238 tcx.hir.hir_to_node_id(hir::HirId {
240 local_id: self.item_local_id()
243 None => ast::DUMMY_NODE_ID
247 /// Returns the span of this Scope. Note that in general the
248 /// returned span may not correspond to the span of any node id in
250 pub fn span(&self, tcx: TyCtxt, scope_tree: &ScopeTree) -> Span {
251 let node_id = self.node_id(tcx, scope_tree);
252 if node_id == ast::DUMMY_NODE_ID {
255 let span = tcx.hir.span(node_id);
256 if let ScopeData::Remainder(r) = self.data() {
257 if let hir::map::NodeBlock(ref blk) = tcx.hir.get(node_id) {
258 // Want span for scope starting after the
259 // indexed statement and ending at end of
260 // `blk`; reuse span of `blk` and shift `lo`
261 // forward to end of indexed statement.
263 // (This is the special case aluded to in the
264 // doc-comment for this method)
266 let stmt_span = blk.stmts[r.first_statement_index.index()].span;
268 // To avoid issues with macro-generated spans, the span
269 // of the statement must be nested in that of the block.
270 if span.lo() <= stmt_span.lo() && stmt_span.lo() <= span.hi() {
271 return Span::new(stmt_span.lo(), span.hi(), span.ctxt());
279 /// The region scope tree encodes information about region relationships.
280 #[derive(Default, Debug)]
281 pub struct ScopeTree {
282 /// If not empty, this body is the root of this region hierarchy.
283 root_body: Option<hir::HirId>,
285 /// The parent of the root body owner, if the latter is an
286 /// an associated const or method, as impls/traits can also
287 /// have lifetime parameters free in this body.
288 root_parent: Option<ast::NodeId>,
290 /// `parent_map` maps from a scope id to the enclosing scope id;
291 /// this is usually corresponding to the lexical nesting, though
292 /// in the case of closures the parent scope is the innermost
293 /// conditional expression or repeating block. (Note that the
294 /// enclosing scope id for the block associated with a closure is
295 /// the closure itself.)
296 parent_map: FxHashMap<Scope, Scope>,
298 /// `var_map` maps from a variable or binding id to the block in
299 /// which that variable is declared.
300 var_map: FxHashMap<hir::ItemLocalId, Scope>,
302 /// maps from a node-id to the associated destruction scope (if any)
303 destruction_scopes: FxHashMap<hir::ItemLocalId, Scope>,
305 /// `rvalue_scopes` includes entries for those expressions whose cleanup scope is
306 /// larger than the default. The map goes from the expression id
307 /// to the cleanup scope id. For rvalues not present in this
308 /// table, the appropriate cleanup scope is the innermost
309 /// enclosing statement, conditional expression, or repeating
310 /// block (see `terminating_scopes`).
311 /// In constants, None is used to indicate that certain expressions
312 /// escape into 'static and should have no local cleanup scope.
313 rvalue_scopes: FxHashMap<hir::ItemLocalId, Option<Scope>>,
315 /// Encodes the hierarchy of fn bodies. Every fn body (including
316 /// closures) forms its own distinct region hierarchy, rooted in
317 /// the block that is the fn body. This map points from the id of
318 /// that root block to the id of the root block for the enclosing
319 /// fn, if any. Thus the map structures the fn bodies into a
320 /// hierarchy based on their lexical mapping. This is used to
321 /// handle the relationships between regions in a fn and in a
322 /// closure defined by that fn. See the "Modeling closures"
323 /// section of the README in infer::region_inference for
325 closure_tree: FxHashMap<hir::ItemLocalId, hir::ItemLocalId>,
327 /// If there are any `yield` nested within a scope, this map
328 /// stores the `Span` of the last one and its index in the
329 /// postorder of the Visitor traversal on the HIR.
331 /// HIR Visitor postorder indexes might seem like a peculiar
332 /// thing to care about. but it turns out that HIR bindings
333 /// and the temporary results of HIR expressions are never
334 /// storage-live at the end of HIR nodes with postorder indexes
335 /// lower than theirs, and therefore don't need to be suspended
336 /// at yield-points at these indexes.
338 /// For an example, suppose we have some code such as:
339 /// ```rust,ignore (example)
340 /// foo(f(), yield y, bar(g()))
343 /// With the HIR tree (calls numbered for expository purposes)
345 /// Call#0(foo, [Call#1(f), Yield(y), Call#2(bar, Call#3(g))])
348 /// Obviously, the result of `f()` was created before the yield
349 /// (and therefore needs to be kept valid over the yield) while
350 /// the result of `g()` occurs after the yield (and therefore
351 /// doesn't). If we want to infer that, we can look at the
352 /// postorder traversal:
354 /// `foo` `f` Call#1 `y` Yield `bar` `g` Call#3 Call#2 Call#0
357 /// In which we can easily see that `Call#1` occurs before the yield,
358 /// and `Call#3` after it.
360 /// To see that this method works, consider:
362 /// Let `D` be our binding/temporary and `U` be our other HIR node, with
363 /// `HIR-postorder(U) < HIR-postorder(D)` (in our example, U would be
364 /// the yield and D would be one of the calls). Let's show that
365 /// `D` is storage-dead at `U`.
367 /// Remember that storage-live/storage-dead refers to the state of
368 /// the *storage*, and does not consider moves/drop flags.
371 /// 1. From the ordering guarantee of HIR visitors (see
372 /// `rustc::hir::intravisit`), `D` does not dominate `U`.
373 /// 2. Therefore, `D` is *potentially* storage-dead at `U` (because
374 /// we might visit `U` without ever getting to `D`).
375 /// 3. However, we guarantee that at each HIR point, each
376 /// binding/temporary is always either always storage-live
377 /// or always storage-dead. This is what is being guaranteed
378 /// by `terminating_scopes` including all blocks where the
379 /// count of executions is not guaranteed.
380 /// 4. By `2.` and `3.`, `D` is *statically* storage-dead at `U`,
383 /// I don't think this property relies on `3.` in an essential way - it
384 /// is probably still correct even if we have "unrestricted" terminating
385 /// scopes. However, why use the complicated proof when a simple one
388 /// A subtle thing: `box` expressions, such as `box (&x, yield 2, &y)`. It
389 /// might seem that a `box` expression creates a `Box<T>` temporary
390 /// when it *starts* executing, at `HIR-preorder(BOX-EXPR)`. That might
391 /// be true in the MIR desugaring, but it is not important in the semantics.
393 /// The reason is that semantically, until the `box` expression returns,
394 /// the values are still owned by their containing expressions. So
395 /// we'll see that `&x`.
396 yield_in_scope: FxHashMap<Scope, (Span, usize)>,
398 /// The number of visit_expr and visit_pat calls done in the body.
399 /// Used to sanity check visit_expr/visit_pat call count when
400 /// calculating generator interiors.
401 body_expr_count: FxHashMap<hir::BodyId, usize>,
404 #[derive(Debug, Copy, Clone)]
406 /// the root of the current region tree. This is typically the id
407 /// of the innermost fn body. Each fn forms its own disjoint tree
408 /// in the region hierarchy. These fn bodies are themselves
409 /// arranged into a tree. See the "Modeling closures" section of
410 /// the README in infer::region_inference for more
412 root_id: Option<hir::ItemLocalId>,
414 /// the scope that contains any new variables declared
415 var_parent: Option<Scope>,
417 /// region parent of expressions etc
418 parent: Option<Scope>,
421 struct RegionResolutionVisitor<'a, 'tcx: 'a> {
422 tcx: TyCtxt<'a, 'tcx, 'tcx>,
424 // The number of expressions and patterns visited in the current body
425 expr_and_pat_count: usize,
427 // Generated scope tree:
428 scope_tree: ScopeTree,
432 /// `terminating_scopes` is a set containing the ids of each
433 /// statement, or conditional/repeating expression. These scopes
434 /// are calling "terminating scopes" because, when attempting to
435 /// find the scope of a temporary, by default we search up the
436 /// enclosing scopes until we encounter the terminating scope. A
437 /// conditional/repeating expression is one which is not
438 /// guaranteed to execute exactly once upon entering the parent
439 /// scope. This could be because the expression only executes
440 /// conditionally, such as the expression `b` in `a && b`, or
441 /// because the expression may execute many times, such as a loop
442 /// body. The reason that we distinguish such expressions is that,
443 /// upon exiting the parent scope, we cannot statically know how
444 /// many times the expression executed, and thus if the expression
445 /// creates temporaries we cannot know statically how many such
446 /// temporaries we would have to cleanup. Therefore we ensure that
447 /// the temporaries never outlast the conditional/repeating
448 /// expression, preventing the need for dynamic checks and/or
449 /// arbitrary amounts of stack space. Terminating scopes end
450 /// up being contained in a DestructionScope that contains the
451 /// destructor's execution.
452 terminating_scopes: FxHashSet<hir::ItemLocalId>,
456 impl<'tcx> ScopeTree {
457 pub fn record_scope_parent(&mut self, child: Scope, parent: Option<Scope>) {
458 debug!("{:?}.parent = {:?}", child, parent);
460 if let Some(p) = parent {
461 let prev = self.parent_map.insert(child, p);
462 assert!(prev.is_none());
465 // record the destruction scopes for later so we can query them
466 if let ScopeData::Destruction(n) = child.data() {
467 self.destruction_scopes.insert(n, child);
471 pub fn each_encl_scope<E>(&self, mut e:E) where E: FnMut(Scope, Scope) {
472 for (&child, &parent) in &self.parent_map {
477 pub fn each_var_scope<E>(&self, mut e:E) where E: FnMut(&hir::ItemLocalId, Scope) {
478 for (child, &parent) in self.var_map.iter() {
483 pub fn opt_destruction_scope(&self, n: hir::ItemLocalId) -> Option<Scope> {
484 self.destruction_scopes.get(&n).cloned()
487 /// Records that `sub_closure` is defined within `sup_closure`. These ids
488 /// should be the id of the block that is the fn body, which is
489 /// also the root of the region hierarchy for that fn.
490 fn record_closure_parent(&mut self,
491 sub_closure: hir::ItemLocalId,
492 sup_closure: hir::ItemLocalId) {
493 debug!("record_closure_parent(sub_closure={:?}, sup_closure={:?})",
494 sub_closure, sup_closure);
495 assert!(sub_closure != sup_closure);
496 let previous = self.closure_tree.insert(sub_closure, sup_closure);
497 assert!(previous.is_none());
500 fn closure_is_enclosed_by(&self,
501 mut sub_closure: hir::ItemLocalId,
502 sup_closure: hir::ItemLocalId) -> bool {
504 if sub_closure == sup_closure { return true; }
505 match self.closure_tree.get(&sub_closure) {
506 Some(&s) => { sub_closure = s; }
507 None => { return false; }
512 fn record_var_scope(&mut self, var: hir::ItemLocalId, lifetime: Scope) {
513 debug!("record_var_scope(sub={:?}, sup={:?})", var, lifetime);
514 assert!(var != lifetime.item_local_id());
515 self.var_map.insert(var, lifetime);
518 fn record_rvalue_scope(&mut self, var: hir::ItemLocalId, lifetime: Option<Scope>) {
519 debug!("record_rvalue_scope(sub={:?}, sup={:?})", var, lifetime);
520 if let Some(lifetime) = lifetime {
521 assert!(var != lifetime.item_local_id());
523 self.rvalue_scopes.insert(var, lifetime);
526 pub fn opt_encl_scope(&self, id: Scope) -> Option<Scope> {
527 //! Returns the narrowest scope that encloses `id`, if any.
528 self.parent_map.get(&id).cloned()
531 #[allow(dead_code)] // used in cfg
532 pub fn encl_scope(&self, id: Scope) -> Scope {
533 //! Returns the narrowest scope that encloses `id`, if any.
534 self.opt_encl_scope(id).unwrap()
537 /// Returns the lifetime of the local variable `var_id`
538 pub fn var_scope(&self, var_id: hir::ItemLocalId) -> Scope {
539 match self.var_map.get(&var_id) {
541 None => { bug!("no enclosing scope for id {:?}", var_id); }
545 pub fn temporary_scope(&self, expr_id: hir::ItemLocalId) -> Option<Scope> {
546 //! Returns the scope when temp created by expr_id will be cleaned up
548 // check for a designated rvalue scope
549 if let Some(&s) = self.rvalue_scopes.get(&expr_id) {
550 debug!("temporary_scope({:?}) = {:?} [custom]", expr_id, s);
554 // else, locate the innermost terminating scope
555 // if there's one. Static items, for instance, won't
556 // have an enclosing scope, hence no scope will be
558 let mut id = Scope::Node(expr_id);
560 while let Some(&p) = self.parent_map.get(&id) {
562 ScopeData::Destruction(..) => {
563 debug!("temporary_scope({:?}) = {:?} [enclosing]",
571 debug!("temporary_scope({:?}) = None", expr_id);
575 pub fn var_region(&self, id: hir::ItemLocalId) -> ty::RegionKind {
576 //! Returns the lifetime of the variable `id`.
578 let scope = ty::ReScope(self.var_scope(id));
579 debug!("var_region({:?}) = {:?}", id, scope);
583 pub fn scopes_intersect(&self, scope1: Scope, scope2: Scope)
585 self.is_subscope_of(scope1, scope2) ||
586 self.is_subscope_of(scope2, scope1)
589 /// Returns true if `subscope` is equal to or is lexically nested inside `superscope` and false
591 pub fn is_subscope_of(&self,
595 let mut s = subscope;
596 debug!("is_subscope_of({:?}, {:?})", subscope, superscope);
597 while superscope != s {
598 match self.opt_encl_scope(s) {
600 debug!("is_subscope_of({:?}, {:?}, s={:?})=false",
601 subscope, superscope, s);
604 Some(scope) => s = scope
608 debug!("is_subscope_of({:?}, {:?})=true",
609 subscope, superscope);
614 /// Finds the nearest common ancestor (if any) of two scopes. That is, finds the smallest
615 /// scope which is greater than or equal to both `scope_a` and `scope_b`.
616 pub fn nearest_common_ancestor(&self,
620 if scope_a == scope_b { return scope_a; }
622 // [1] The initial values for `a_buf` and `b_buf` are not used.
623 // The `ancestors_of` function will return some prefix that
624 // is re-initialized with new values (or else fallback to a
625 // heap-allocated vector).
626 let mut a_buf: [Scope; 32] = [scope_a /* [1] */; 32];
627 let mut a_vec: Vec<Scope> = vec![];
628 let mut b_buf: [Scope; 32] = [scope_b /* [1] */; 32];
629 let mut b_vec: Vec<Scope> = vec![];
630 let parent_map = &self.parent_map;
631 let a_ancestors = ancestors_of(parent_map, scope_a, &mut a_buf, &mut a_vec);
632 let b_ancestors = ancestors_of(parent_map, scope_b, &mut b_buf, &mut b_vec);
633 let mut a_index = a_ancestors.len() - 1;
634 let mut b_index = b_ancestors.len() - 1;
636 // Here, [ab]_ancestors is a vector going from narrow to broad.
637 // The end of each vector will be the item where the scope is
638 // defined; if there are any common ancestors, then the tails of
639 // the vector will be the same. So basically we want to walk
640 // backwards from the tail of each vector and find the first point
641 // where they diverge. If one vector is a suffix of the other,
642 // then the corresponding scope is a superscope of the other.
644 if a_ancestors[a_index] != b_ancestors[b_index] {
645 // In this case, the two regions belong to completely
646 // different functions. Compare those fn for lexical
647 // nesting. The reasoning behind this is subtle. See the
648 // "Modeling closures" section of the README in
649 // infer::region_inference for more details.
650 let a_root_scope = a_ancestors[a_index];
651 let b_root_scope = a_ancestors[a_index];
652 return match (a_root_scope.data(), b_root_scope.data()) {
653 (ScopeData::Destruction(a_root_id),
654 ScopeData::Destruction(b_root_id)) => {
655 if self.closure_is_enclosed_by(a_root_id, b_root_id) {
656 // `a` is enclosed by `b`, hence `b` is the ancestor of everything in `a`
658 } else if self.closure_is_enclosed_by(b_root_id, a_root_id) {
659 // `b` is enclosed by `a`, hence `a` is the ancestor of everything in `b`
662 // neither fn encloses the other
667 // root ids are always Node right now
674 // Loop invariant: a_ancestors[a_index] == b_ancestors[b_index]
675 // for all indices between a_index and the end of the array
676 if a_index == 0 { return scope_a; }
677 if b_index == 0 { return scope_b; }
680 if a_ancestors[a_index] != b_ancestors[b_index] {
681 return a_ancestors[a_index + 1];
685 fn ancestors_of<'a, 'tcx>(parent_map: &FxHashMap<Scope, Scope>,
687 buf: &'a mut [Scope; 32],
688 vec: &'a mut Vec<Scope>)
690 // debug!("ancestors_of(scope={:?})", scope);
691 let mut scope = scope;
696 match parent_map.get(&scope) {
697 Some(&superscope) => scope = superscope,
698 _ => return &buf[..i+1]
703 *vec = Vec::with_capacity(64);
704 vec.extend_from_slice(buf);
707 match parent_map.get(&scope) {
708 Some(&superscope) => scope = superscope,
715 /// Assuming that the provided region was defined within this `ScopeTree`,
716 /// returns the outermost `Scope` that the region outlives.
717 pub fn early_free_scope<'a, 'gcx>(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>,
718 br: &ty::EarlyBoundRegion)
720 let param_owner = tcx.parent_def_id(br.def_id).unwrap();
722 let param_owner_id = tcx.hir.as_local_node_id(param_owner).unwrap();
723 let scope = tcx.hir.maybe_body_owned_by(param_owner_id).map(|body_id| {
724 tcx.hir.body(body_id).value.hir_id.local_id
725 }).unwrap_or_else(|| {
726 // The lifetime was defined on node that doesn't own a body,
727 // which in practice can only mean a trait or an impl, that
728 // is the parent of a method, and that is enforced below.
729 assert_eq!(Some(param_owner_id), self.root_parent,
730 "free_scope: {:?} not recognized by the \
731 region scope tree for {:?} / {:?}",
733 self.root_parent.map(|id| tcx.hir.local_def_id(id)),
734 self.root_body.map(|hir_id| DefId::local(hir_id.owner)));
736 // The trait/impl lifetime is in scope for the method's body.
737 self.root_body.unwrap().local_id
740 Scope::CallSite(scope)
743 /// Assuming that the provided region was defined within this `ScopeTree`,
744 /// returns the outermost `Scope` that the region outlives.
745 pub fn free_scope<'a, 'gcx>(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, fr: &ty::FreeRegion)
747 let param_owner = match fr.bound_region {
748 ty::BoundRegion::BrNamed(def_id, _) => {
749 tcx.parent_def_id(def_id).unwrap()
754 // Ensure that the named late-bound lifetimes were defined
755 // on the same function that they ended up being freed in.
756 assert_eq!(param_owner, fr.scope);
758 let param_owner_id = tcx.hir.as_local_node_id(param_owner).unwrap();
759 let body_id = tcx.hir.body_owned_by(param_owner_id);
760 Scope::CallSite(tcx.hir.body(body_id).value.hir_id.local_id)
763 /// Checks whether the given scope contains a `yield`. If so,
764 /// returns `Some((span, expr_count))` with the span of a yield we found and
765 /// the number of expressions appearing before the `yield` in the body.
766 pub fn yield_in_scope(&self, scope: Scope) -> Option<(Span, usize)> {
767 self.yield_in_scope.get(&scope).cloned()
770 /// Gives the number of expressions visited in a body.
771 /// Used to sanity check visit_expr call count when
772 /// calculating generator interiors.
773 pub fn body_expr_count(&self, body_id: hir::BodyId) -> Option<usize> {
774 self.body_expr_count.get(&body_id).map(|r| *r)
778 /// Records the lifetime of a local variable as `cx.var_parent`
779 fn record_var_lifetime(visitor: &mut RegionResolutionVisitor,
780 var_id: hir::ItemLocalId,
782 match visitor.cx.var_parent {
784 // this can happen in extern fn declarations like
786 // extern fn isalnum(c: c_int) -> c_int
788 Some(parent_scope) =>
789 visitor.scope_tree.record_var_scope(var_id, parent_scope),
793 fn resolve_block<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>, blk: &'tcx hir::Block) {
794 debug!("resolve_block(blk.id={:?})", blk.id);
796 let prev_cx = visitor.cx;
798 // We treat the tail expression in the block (if any) somewhat
799 // differently from the statements. The issue has to do with
800 // temporary lifetimes. Consider the following:
803 // let inner = ... (&bar()) ...;
805 // (... (&foo()) ...) // (the tail expression)
806 // }, other_argument());
808 // Each of the statements within the block is a terminating
809 // scope, and thus a temporary (e.g. the result of calling
810 // `bar()` in the initalizer expression for `let inner = ...;`)
811 // will be cleaned up immediately after its corresponding
812 // statement (i.e. `let inner = ...;`) executes.
814 // On the other hand, temporaries associated with evaluating the
815 // tail expression for the block are assigned lifetimes so that
816 // they will be cleaned up as part of the terminating scope
817 // *surrounding* the block expression. Here, the terminating
818 // scope for the block expression is the `quux(..)` call; so
819 // those temporaries will only be cleaned up *after* both
820 // `other_argument()` has run and also the call to `quux(..)`
821 // itself has returned.
823 visitor.enter_node_scope_with_dtor(blk.hir_id.local_id);
824 visitor.cx.var_parent = visitor.cx.parent;
827 // This block should be kept approximately in sync with
828 // `intravisit::walk_block`. (We manually walk the block, rather
829 // than call `walk_block`, in order to maintain precise
830 // index information.)
832 for (i, statement) in blk.stmts.iter().enumerate() {
833 if let hir::StmtDecl(..) = statement.node {
834 // Each StmtDecl introduces a subscope for bindings
835 // introduced by the declaration; this subscope covers
836 // a suffix of the block . Each subscope in a block
837 // has the previous subscope in the block as a parent,
838 // except for the first such subscope, which has the
839 // block itself as a parent.
841 Scope::Remainder(BlockRemainder {
842 block: blk.hir_id.local_id,
843 first_statement_index: FirstStatementIndex::new(i)
846 visitor.cx.var_parent = visitor.cx.parent;
848 visitor.visit_stmt(statement)
850 walk_list!(visitor, visit_expr, &blk.expr);
853 visitor.cx = prev_cx;
856 fn resolve_arm<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>, arm: &'tcx hir::Arm) {
857 visitor.terminating_scopes.insert(arm.body.hir_id.local_id);
859 if let Some(ref expr) = arm.guard {
860 visitor.terminating_scopes.insert(expr.hir_id.local_id);
863 intravisit::walk_arm(visitor, arm);
866 fn resolve_pat<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>, pat: &'tcx hir::Pat) {
867 visitor.record_child_scope(Scope::Node(pat.hir_id.local_id));
869 // If this is a binding then record the lifetime of that binding.
870 if let PatKind::Binding(..) = pat.node {
871 record_var_lifetime(visitor, pat.hir_id.local_id, pat.span);
874 intravisit::walk_pat(visitor, pat);
876 visitor.expr_and_pat_count += 1;
879 fn resolve_stmt<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>, stmt: &'tcx hir::Stmt) {
880 let stmt_id = visitor.tcx.hir.node_to_hir_id(stmt.node.id()).local_id;
881 debug!("resolve_stmt(stmt.id={:?})", stmt_id);
883 // Every statement will clean up the temporaries created during
884 // execution of that statement. Therefore each statement has an
885 // associated destruction scope that represents the scope of the
886 // statement plus its destructors, and thus the scope for which
887 // regions referenced by the destructors need to survive.
888 visitor.terminating_scopes.insert(stmt_id);
890 let prev_parent = visitor.cx.parent;
891 visitor.enter_node_scope_with_dtor(stmt_id);
893 intravisit::walk_stmt(visitor, stmt);
895 visitor.cx.parent = prev_parent;
898 fn resolve_expr<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>, expr: &'tcx hir::Expr) {
899 debug!("resolve_expr(expr.id={:?})", expr.id);
901 let prev_cx = visitor.cx;
902 visitor.enter_node_scope_with_dtor(expr.hir_id.local_id);
905 let terminating_scopes = &mut visitor.terminating_scopes;
906 let mut terminating = |id: hir::ItemLocalId| {
907 terminating_scopes.insert(id);
910 // Conditional or repeating scopes are always terminating
911 // scopes, meaning that temporaries cannot outlive them.
912 // This ensures fixed size stacks.
914 hir::ExprBinary(codemap::Spanned { node: hir::BiAnd, .. }, _, ref r) |
915 hir::ExprBinary(codemap::Spanned { node: hir::BiOr, .. }, _, ref r) => {
916 // For shortcircuiting operators, mark the RHS as a terminating
917 // scope since it only executes conditionally.
918 terminating(r.hir_id.local_id);
921 hir::ExprIf(ref expr, ref then, Some(ref otherwise)) => {
922 terminating(expr.hir_id.local_id);
923 terminating(then.hir_id.local_id);
924 terminating(otherwise.hir_id.local_id);
927 hir::ExprIf(ref expr, ref then, None) => {
928 terminating(expr.hir_id.local_id);
929 terminating(then.hir_id.local_id);
932 hir::ExprLoop(ref body, _, _) => {
933 terminating(body.hir_id.local_id);
936 hir::ExprWhile(ref expr, ref body, _) => {
937 terminating(expr.hir_id.local_id);
938 terminating(body.hir_id.local_id);
941 hir::ExprMatch(..) => {
942 visitor.cx.var_parent = visitor.cx.parent;
945 hir::ExprAssignOp(..) | hir::ExprIndex(..) |
946 hir::ExprUnary(..) | hir::ExprCall(..) | hir::ExprMethodCall(..) => {
947 // FIXME(https://github.com/rust-lang/rfcs/issues/811) Nested method calls
949 // The lifetimes for a call or method call look as follows:
957 // The idea is that call.callee_id represents *the time when
958 // the invoked function is actually running* and call.id
959 // represents *the time to prepare the arguments and make the
960 // call*. See the section "Borrows in Calls" borrowck/README.md
961 // for an extended explanation of why this distinction is
964 // record_superlifetime(new_cx, expr.callee_id);
972 // Manually recurse over closures, because they are the only
973 // case of nested bodies that share the parent environment.
974 hir::ExprClosure(.., body, _, _) => {
975 let body = visitor.tcx.hir.body(body);
976 visitor.visit_body(body);
979 _ => intravisit::walk_expr(visitor, expr)
982 visitor.expr_and_pat_count += 1;
984 if let hir::ExprYield(..) = expr.node {
985 // Mark this expr's scope and all parent scopes as containing `yield`.
986 let mut scope = Scope::Node(expr.hir_id.local_id);
988 visitor.scope_tree.yield_in_scope.insert(scope,
989 (expr.span, visitor.expr_and_pat_count));
991 // Keep traversing up while we can.
992 match visitor.scope_tree.parent_map.get(&scope) {
993 // Don't cross from closure bodies to their parent.
994 Some(&superscope) => match superscope.data() {
995 ScopeData::CallSite(_) => break,
996 _ => scope = superscope
1003 visitor.cx = prev_cx;
1006 fn resolve_local<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>,
1007 pat: Option<&'tcx hir::Pat>,
1008 init: Option<&'tcx hir::Expr>) {
1009 debug!("resolve_local(pat={:?}, init={:?})", pat, init);
1011 let blk_scope = visitor.cx.var_parent;
1013 // As an exception to the normal rules governing temporary
1014 // lifetimes, initializers in a let have a temporary lifetime
1015 // of the enclosing block. This means that e.g. a program
1016 // like the following is legal:
1018 // let ref x = HashMap::new();
1020 // Because the hash map will be freed in the enclosing block.
1022 // We express the rules more formally based on 3 grammars (defined
1023 // fully in the helpers below that implement them):
1025 // 1. `E&`, which matches expressions like `&<rvalue>` that
1026 // own a pointer into the stack.
1028 // 2. `P&`, which matches patterns like `ref x` or `(ref x, ref
1029 // y)` that produce ref bindings into the value they are
1030 // matched against or something (at least partially) owned by
1031 // the value they are matched against. (By partially owned,
1032 // I mean that creating a binding into a ref-counted or managed value
1033 // would still count.)
1035 // 3. `ET`, which matches both rvalues like `foo()` as well as lvalues
1036 // based on rvalues like `foo().x[2].y`.
1038 // A subexpression `<rvalue>` that appears in a let initializer
1039 // `let pat [: ty] = expr` has an extended temporary lifetime if
1040 // any of the following conditions are met:
1042 // A. `pat` matches `P&` and `expr` matches `ET`
1043 // (covers cases where `pat` creates ref bindings into an rvalue
1044 // produced by `expr`)
1045 // B. `ty` is a borrowed pointer and `expr` matches `ET`
1046 // (covers cases where coercion creates a borrow)
1047 // C. `expr` matches `E&`
1048 // (covers cases `expr` borrows an rvalue that is then assigned
1049 // to memory (at least partially) owned by the binding)
1051 // Here are some examples hopefully giving an intuition where each
1052 // rule comes into play and why:
1054 // Rule A. `let (ref x, ref y) = (foo().x, 44)`. The rvalue `(22, 44)`
1055 // would have an extended lifetime, but not `foo()`.
1057 // Rule B. `let x = &foo().x`. The rvalue ``foo()` would have extended
1060 // In some cases, multiple rules may apply (though not to the same
1061 // rvalue). For example:
1063 // let ref x = [&a(), &b()];
1065 // Here, the expression `[...]` has an extended lifetime due to rule
1066 // A, but the inner rvalues `a()` and `b()` have an extended lifetime
1069 if let Some(expr) = init {
1070 record_rvalue_scope_if_borrow_expr(visitor, &expr, blk_scope);
1072 if let Some(pat) = pat {
1073 if is_binding_pat(pat) {
1074 record_rvalue_scope(visitor, &expr, blk_scope);
1079 if let Some(pat) = pat {
1080 visitor.visit_pat(pat);
1082 if let Some(expr) = init {
1083 visitor.visit_expr(expr);
1086 /// True if `pat` match the `P&` nonterminal:
1089 /// | StructName { ..., P&, ... }
1090 /// | VariantName(..., P&, ...)
1091 /// | [ ..., P&, ... ]
1092 /// | ( ..., P&, ... )
1094 fn is_binding_pat(pat: &hir::Pat) -> bool {
1095 // Note that the code below looks for *explicit* refs only, that is, it won't
1096 // know about *implicit* refs as introduced in #42640.
1098 // This is not a problem. For example, consider
1100 // let (ref x, ref y) = (Foo { .. }, Bar { .. });
1102 // Due to the explicit refs on the left hand side, the below code would signal
1103 // that the temporary value on the right hand side should live until the end of
1104 // the enclosing block (as opposed to being dropped after the let is complete).
1106 // To create an implicit ref, however, you must have a borrowed value on the RHS
1107 // already, as in this example (which won't compile before #42640):
1109 // let Foo { x, .. } = &Foo { x: ..., ... };
1113 // let Foo { ref x, .. } = Foo { ... };
1115 // In the former case (the implicit ref version), the temporary is created by the
1116 // & expression, and its lifetime would be extended to the end of the block (due
1117 // to a different rule, not the below code).
1119 PatKind::Binding(hir::BindingAnnotation::Ref, ..) |
1120 PatKind::Binding(hir::BindingAnnotation::RefMut, ..) => true,
1122 PatKind::Struct(_, ref field_pats, _) => {
1123 field_pats.iter().any(|fp| is_binding_pat(&fp.node.pat))
1126 PatKind::Slice(ref pats1, ref pats2, ref pats3) => {
1127 pats1.iter().any(|p| is_binding_pat(&p)) ||
1128 pats2.iter().any(|p| is_binding_pat(&p)) ||
1129 pats3.iter().any(|p| is_binding_pat(&p))
1132 PatKind::TupleStruct(_, ref subpats, _) |
1133 PatKind::Tuple(ref subpats, _) => {
1134 subpats.iter().any(|p| is_binding_pat(&p))
1137 PatKind::Box(ref subpat) => {
1138 is_binding_pat(&subpat)
1145 /// If `expr` matches the `E&` grammar, then records an extended rvalue scope as appropriate:
1148 /// | StructName { ..., f: E&, ... }
1149 /// | [ ..., E&, ... ]
1150 /// | ( ..., E&, ... )
1155 fn record_rvalue_scope_if_borrow_expr<'a, 'tcx>(
1156 visitor: &mut RegionResolutionVisitor<'a, 'tcx>,
1158 blk_id: Option<Scope>)
1161 hir::ExprAddrOf(_, ref subexpr) => {
1162 record_rvalue_scope_if_borrow_expr(visitor, &subexpr, blk_id);
1163 record_rvalue_scope(visitor, &subexpr, blk_id);
1165 hir::ExprStruct(_, ref fields, _) => {
1166 for field in fields {
1167 record_rvalue_scope_if_borrow_expr(
1168 visitor, &field.expr, blk_id);
1171 hir::ExprArray(ref subexprs) |
1172 hir::ExprTup(ref subexprs) => {
1173 for subexpr in subexprs {
1174 record_rvalue_scope_if_borrow_expr(
1175 visitor, &subexpr, blk_id);
1178 hir::ExprCast(ref subexpr, _) => {
1179 record_rvalue_scope_if_borrow_expr(visitor, &subexpr, blk_id)
1181 hir::ExprBlock(ref block) => {
1182 if let Some(ref subexpr) = block.expr {
1183 record_rvalue_scope_if_borrow_expr(
1184 visitor, &subexpr, blk_id);
1191 /// Applied to an expression `expr` if `expr` -- or something owned or partially owned by
1192 /// `expr` -- is going to be indirectly referenced by a variable in a let statement. In that
1193 /// case, the "temporary lifetime" or `expr` is extended to be the block enclosing the `let`
1196 /// More formally, if `expr` matches the grammar `ET`, record the rvalue scope of the matching
1197 /// `<rvalue>` as `blk_id`:
1205 /// Note: ET is intended to match "rvalues or lvalues based on rvalues".
1206 fn record_rvalue_scope<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>,
1208 blk_scope: Option<Scope>) {
1209 let mut expr = expr;
1211 // Note: give all the expressions matching `ET` with the
1212 // extended temporary lifetime, not just the innermost rvalue,
1213 // because in trans if we must compile e.g. `*rvalue()`
1214 // into a temporary, we request the temporary scope of the
1215 // outer expression.
1216 visitor.scope_tree.record_rvalue_scope(expr.hir_id.local_id, blk_scope);
1219 hir::ExprAddrOf(_, ref subexpr) |
1220 hir::ExprUnary(hir::UnDeref, ref subexpr) |
1221 hir::ExprField(ref subexpr, _) |
1222 hir::ExprTupField(ref subexpr, _) |
1223 hir::ExprIndex(ref subexpr, _) => {
1234 impl<'a, 'tcx> RegionResolutionVisitor<'a, 'tcx> {
1235 /// Records the current parent (if any) as the parent of `child_scope`.
1236 fn record_child_scope(&mut self, child_scope: Scope) {
1237 let parent = self.cx.parent;
1238 self.scope_tree.record_scope_parent(child_scope, parent);
1241 /// Records the current parent (if any) as the parent of `child_scope`,
1242 /// and sets `child_scope` as the new current parent.
1243 fn enter_scope(&mut self, child_scope: Scope) {
1244 self.record_child_scope(child_scope);
1245 self.cx.parent = Some(child_scope);
1248 fn enter_node_scope_with_dtor(&mut self, id: hir::ItemLocalId) {
1249 // If node was previously marked as a terminating scope during the
1250 // recursive visit of its parent node in the AST, then we need to
1251 // account for the destruction scope representing the scope of
1252 // the destructors that run immediately after it completes.
1253 if self.terminating_scopes.contains(&id) {
1254 self.enter_scope(Scope::Destruction(id));
1256 self.enter_scope(Scope::Node(id));
1260 impl<'a, 'tcx> Visitor<'tcx> for RegionResolutionVisitor<'a, 'tcx> {
1261 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1262 NestedVisitorMap::None
1265 fn visit_block(&mut self, b: &'tcx Block) {
1266 resolve_block(self, b);
1269 fn visit_body(&mut self, body: &'tcx hir::Body) {
1270 let body_id = body.id();
1271 let owner_id = self.tcx.hir.body_owner(body_id);
1273 debug!("visit_body(id={:?}, span={:?}, body.id={:?}, cx.parent={:?})",
1275 self.tcx.sess.codemap().span_to_string(body.value.span),
1279 let outer_ec = mem::replace(&mut self.expr_and_pat_count, 0);
1280 let outer_cx = self.cx;
1281 let outer_ts = mem::replace(&mut self.terminating_scopes, FxHashSet());
1282 self.terminating_scopes.insert(body.value.hir_id.local_id);
1284 if let Some(root_id) = self.cx.root_id {
1285 self.scope_tree.record_closure_parent(body.value.hir_id.local_id, root_id);
1287 self.cx.root_id = Some(body.value.hir_id.local_id);
1289 self.enter_scope(Scope::CallSite(body.value.hir_id.local_id));
1290 self.enter_scope(Scope::Arguments(body.value.hir_id.local_id));
1292 // The arguments and `self` are parented to the fn.
1293 self.cx.var_parent = self.cx.parent.take();
1294 for argument in &body.arguments {
1295 self.visit_pat(&argument.pat);
1298 // The body of the every fn is a root scope.
1299 self.cx.parent = self.cx.var_parent;
1300 if let hir::BodyOwnerKind::Fn = self.tcx.hir.body_owner_kind(owner_id) {
1301 self.visit_expr(&body.value);
1303 // Only functions have an outer terminating (drop) scope, while
1304 // temporaries in constant initializers may be 'static, but only
1305 // according to rvalue lifetime semantics, using the same
1306 // syntactical rules used for let initializers.
1308 // E.g. in `let x = &f();`, the temporary holding the result from
1309 // the `f()` call lives for the entirety of the surrounding block.
1311 // Similarly, `const X: ... = &f();` would have the result of `f()`
1312 // live for `'static`, implying (if Drop restrictions on constants
1313 // ever get lifted) that the value *could* have a destructor, but
1314 // it'd get leaked instead of the destructor running during the
1315 // evaluation of `X` (if at all allowed by CTFE).
1317 // However, `const Y: ... = g(&f());`, like `let y = g(&f());`,
1318 // would *not* let the `f()` temporary escape into an outer scope
1319 // (i.e. `'static`), which means that after `g` returns, it drops,
1320 // and all the associated destruction scope rules apply.
1321 self.cx.var_parent = None;
1322 resolve_local(self, None, Some(&body.value));
1325 if body.is_generator {
1326 self.scope_tree.body_expr_count.insert(body_id, self.expr_and_pat_count);
1329 // Restore context we had at the start.
1330 self.expr_and_pat_count = outer_ec;
1332 self.terminating_scopes = outer_ts;
1335 fn visit_arm(&mut self, a: &'tcx Arm) {
1336 resolve_arm(self, a);
1338 fn visit_pat(&mut self, p: &'tcx Pat) {
1339 resolve_pat(self, p);
1341 fn visit_stmt(&mut self, s: &'tcx Stmt) {
1342 resolve_stmt(self, s);
1344 fn visit_expr(&mut self, ex: &'tcx Expr) {
1345 resolve_expr(self, ex);
1347 fn visit_local(&mut self, l: &'tcx Local) {
1348 resolve_local(self, Some(&l.pat), l.init.as_ref().map(|e| &**e));
1352 fn region_scope_tree<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId)
1355 let closure_base_def_id = tcx.closure_base_def_id(def_id);
1356 if closure_base_def_id != def_id {
1357 return tcx.region_scope_tree(closure_base_def_id);
1360 let id = tcx.hir.as_local_node_id(def_id).unwrap();
1361 let scope_tree = if let Some(body_id) = tcx.hir.maybe_body_owned_by(id) {
1362 let mut visitor = RegionResolutionVisitor {
1364 scope_tree: ScopeTree::default(),
1365 expr_and_pat_count: 0,
1371 terminating_scopes: FxHashSet(),
1374 let body = tcx.hir.body(body_id);
1375 visitor.scope_tree.root_body = Some(body.value.hir_id);
1377 // If the item is an associated const or a method,
1378 // record its impl/trait parent, as it can also have
1379 // lifetime parameters free in this body.
1380 match tcx.hir.get(id) {
1381 hir::map::NodeImplItem(_) |
1382 hir::map::NodeTraitItem(_) => {
1383 visitor.scope_tree.root_parent = Some(tcx.hir.get_parent(id));
1388 visitor.visit_body(body);
1392 ScopeTree::default()
1398 pub fn provide(providers: &mut Providers) {
1399 *providers = Providers {
1405 impl<'gcx> HashStable<StableHashingContext<'gcx>> for ScopeTree {
1406 fn hash_stable<W: StableHasherResult>(&self,
1407 hcx: &mut StableHashingContext<'gcx>,
1408 hasher: &mut StableHasher<W>) {
1412 ref body_expr_count,
1415 ref destruction_scopes,
1421 hcx.with_node_id_hashing_mode(NodeIdHashingMode::HashDefPath, |hcx| {
1422 root_body.hash_stable(hcx, hasher);
1423 root_parent.hash_stable(hcx, hasher);
1426 body_expr_count.hash_stable(hcx, hasher);
1427 parent_map.hash_stable(hcx, hasher);
1428 var_map.hash_stable(hcx, hasher);
1429 destruction_scopes.hash_stable(hcx, hasher);
1430 rvalue_scopes.hash_stable(hcx, hasher);
1431 closure_tree.hash_stable(hcx, hasher);
1432 yield_in_scope.hash_stable(hcx, hasher);