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 //! For more information about how MIR-based region-checking works,
15 //! see the [rustc guide].
17 //! [rustc guide]: https://rust-lang-nursery.github.io/rustc-guide/mir/borrowck.html
19 use ich::{StableHashingContext, NodeIdHashingMode};
20 use util::nodemap::{FxHashMap, FxHashSet};
25 use rustc_data_structures::sync::Lrc;
28 use syntax_pos::{Span, DUMMY_SP};
30 use ty::query::Providers;
33 use hir::def_id::DefId;
34 use hir::intravisit::{self, Visitor, NestedVisitorMap};
35 use hir::{Block, Arm, Pat, PatKind, Stmt, Expr, Local};
36 use rustc_data_structures::indexed_vec::Idx;
37 use rustc_data_structures::stable_hasher::{HashStable, StableHasher,
40 /// Scope represents a statically-describable scope that can be
41 /// used to bound the lifetime/region for values.
43 /// `Node(node_id)`: Any AST node that has any scope at all has the
44 /// `Node(node_id)` scope. Other variants represent special cases not
45 /// immediately derivable from the abstract syntax tree structure.
47 /// `DestructionScope(node_id)` represents the scope of destructors
48 /// implicitly-attached to `node_id` that run immediately after the
49 /// expression for `node_id` itself. Not every AST node carries a
50 /// `DestructionScope`, but those that are `terminating_scopes` do;
51 /// see discussion with `ScopeTree`.
53 /// `Remainder(BlockRemainder { block, statement_index })` represents
54 /// the scope of user code running immediately after the initializer
55 /// expression for the indexed statement, until the end of the block.
57 /// So: the following code can be broken down into the scopes beneath:
60 /// let a = f().g( 'b: { let x = d(); let y = d(); x.h(y) } ) ;
64 /// +---------+ (R10.)
66 /// +----------+ (M8.)
67 /// +----------------------+ (R7.)
69 /// +----------+ (M5.)
70 /// +-----------------------------------+ (M4.)
71 /// +--------------------------------------------------+ (M3.)
73 /// +-----------------------------------------------------------+ (M1.)
75 /// (M1.): Node scope of the whole `let a = ...;` statement.
76 /// (M2.): Node scope of the `f()` expression.
77 /// (M3.): Node scope of the `f().g(..)` expression.
78 /// (M4.): Node scope of the block labeled `'b:`.
79 /// (M5.): Node scope of the `let x = d();` statement
80 /// (D6.): DestructionScope for temporaries created during M5.
81 /// (R7.): Remainder scope for block `'b:`, stmt 0 (let x = ...).
82 /// (M8.): Node scope of the `let y = d();` statement.
83 /// (D9.): DestructionScope for temporaries created during M8.
84 /// (R10.): Remainder scope for block `'b:`, stmt 1 (let y = ...).
85 /// (D11.): DestructionScope for temporaries and bindings from block `'b:`.
86 /// (D12.): DestructionScope for temporaries created during M1 (e.g. f()).
89 /// Note that while the above picture shows the destruction scopes
90 /// as following their corresponding node scopes, in the internal
91 /// data structures of the compiler the destruction scopes are
92 /// represented as enclosing parents. This is sound because we use the
93 /// enclosing parent relationship just to ensure that referenced
94 /// values live long enough; phrased another way, the starting point
95 /// of each range is not really the important thing in the above
96 /// picture, but rather the ending point.
98 /// FIXME (pnkfelix): This currently derives `PartialOrd` and `Ord` to
99 /// placate the same deriving in `ty::FreeRegion`, but we may want to
100 /// actually attach a more meaningful ordering to scopes than the one
101 /// generated via deriving here.
103 /// Scope is a bit-packed to save space - if `code` is SCOPE_DATA_REMAINDER_MAX
104 /// or less, it is a `ScopeData::Remainder`, otherwise it is a type specified
105 /// by the bitpacking.
106 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, Copy, RustcEncodable, RustcDecodable)]
108 pub(crate) id: hir::ItemLocalId,
112 const SCOPE_DATA_NODE: u32 = !0;
113 const SCOPE_DATA_CALLSITE: u32 = !1;
114 const SCOPE_DATA_ARGUMENTS: u32 = !2;
115 const SCOPE_DATA_DESTRUCTION: u32 = !3;
116 const SCOPE_DATA_REMAINDER_MAX: u32 = !4;
118 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, Debug, Copy, RustcEncodable, RustcDecodable)]
120 Node(hir::ItemLocalId),
122 // Scope of the call-site for a function or closure
123 // (outlives the arguments as well as the body).
124 CallSite(hir::ItemLocalId),
126 // Scope of arguments passed to a function or closure
127 // (they outlive its body).
128 Arguments(hir::ItemLocalId),
130 // Scope of destructors for temporaries of node-id.
131 Destruction(hir::ItemLocalId),
133 // Scope following a `let id = expr;` binding in a block.
134 Remainder(BlockRemainder)
137 /// Represents a subscope of `block` for a binding that is introduced
138 /// by `block.stmts[first_statement_index]`. Such subscopes represent
139 /// a suffix of the block. Note that each subscope does not include
140 /// the initializer expression, if any, for the statement indexed by
141 /// `first_statement_index`.
143 /// For example, given `{ let (a, b) = EXPR_1; let c = EXPR_2; ... }`:
145 /// * the subscope with `first_statement_index == 0` is scope of both
146 /// `a` and `b`; it does not include EXPR_1, but does include
147 /// everything after that first `let`. (If you want a scope that
148 /// includes EXPR_1 as well, then do not use `Scope::Remainder`,
149 /// but instead another `Scope` that encompasses the whole block,
150 /// e.g. `Scope::Node`.
152 /// * the subscope with `first_statement_index == 1` is scope of `c`,
153 /// and thus does not include EXPR_2, but covers the `...`.
154 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, RustcEncodable,
155 RustcDecodable, Debug, Copy)]
156 pub struct BlockRemainder {
157 pub block: hir::ItemLocalId,
158 pub first_statement_index: FirstStatementIndex,
161 newtype_index!(FirstStatementIndex
164 MAX = SCOPE_DATA_REMAINDER_MAX
167 impl From<ScopeData> for Scope {
169 fn from(scope_data: ScopeData) -> Self {
170 let (id, code) = match scope_data {
171 ScopeData::Node(id) => (id, SCOPE_DATA_NODE),
172 ScopeData::CallSite(id) => (id, SCOPE_DATA_CALLSITE),
173 ScopeData::Arguments(id) => (id, SCOPE_DATA_ARGUMENTS),
174 ScopeData::Destruction(id) => (id, SCOPE_DATA_DESTRUCTION),
175 ScopeData::Remainder(r) => (r.block, r.first_statement_index.index() as u32)
181 impl fmt::Debug for Scope {
182 fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
183 fmt::Debug::fmt(&self.data(), formatter)
187 #[allow(non_snake_case)]
190 pub fn data(self) -> ScopeData {
192 SCOPE_DATA_NODE => ScopeData::Node(self.id),
193 SCOPE_DATA_CALLSITE => ScopeData::CallSite(self.id),
194 SCOPE_DATA_ARGUMENTS => ScopeData::Arguments(self.id),
195 SCOPE_DATA_DESTRUCTION => ScopeData::Destruction(self.id),
196 idx => ScopeData::Remainder(BlockRemainder {
198 first_statement_index: FirstStatementIndex::new(idx as usize)
204 pub fn Node(id: hir::ItemLocalId) -> Self {
205 Self::from(ScopeData::Node(id))
209 pub fn CallSite(id: hir::ItemLocalId) -> Self {
210 Self::from(ScopeData::CallSite(id))
214 pub fn Arguments(id: hir::ItemLocalId) -> Self {
215 Self::from(ScopeData::Arguments(id))
219 pub fn Destruction(id: hir::ItemLocalId) -> Self {
220 Self::from(ScopeData::Destruction(id))
224 pub fn Remainder(r: BlockRemainder) -> Self {
225 Self::from(ScopeData::Remainder(r))
230 /// Returns a item-local id associated with this scope.
232 /// NB: likely to be replaced as API is refined; e.g. pnkfelix
233 /// anticipates `fn entry_node_id` and `fn each_exit_node_id`.
234 pub fn item_local_id(&self) -> hir::ItemLocalId {
238 pub fn node_id(&self, tcx: TyCtxt, scope_tree: &ScopeTree) -> ast::NodeId {
239 match scope_tree.root_body {
241 tcx.hir.hir_to_node_id(hir::HirId {
243 local_id: self.item_local_id()
246 None => ast::DUMMY_NODE_ID
250 /// Returns the span of this Scope. Note that in general the
251 /// returned span may not correspond to the span of any node id in
253 pub fn span(&self, tcx: TyCtxt, scope_tree: &ScopeTree) -> Span {
254 let node_id = self.node_id(tcx, scope_tree);
255 if node_id == ast::DUMMY_NODE_ID {
258 let span = tcx.hir.span(node_id);
259 if let ScopeData::Remainder(r) = self.data() {
260 if let hir::map::NodeBlock(ref blk) = tcx.hir.get(node_id) {
261 // Want span for scope starting after the
262 // indexed statement and ending at end of
263 // `blk`; reuse span of `blk` and shift `lo`
264 // forward to end of indexed statement.
266 // (This is the special case aluded to in the
267 // doc-comment for this method)
269 let stmt_span = blk.stmts[r.first_statement_index.index()].span;
271 // To avoid issues with macro-generated spans, the span
272 // of the statement must be nested in that of the block.
273 if span.lo() <= stmt_span.lo() && stmt_span.lo() <= span.hi() {
274 return Span::new(stmt_span.lo(), span.hi(), span.ctxt());
282 pub type ScopeDepth = u32;
284 /// The region scope tree encodes information about region relationships.
285 #[derive(Default, Debug)]
286 pub struct ScopeTree {
287 /// If not empty, this body is the root of this region hierarchy.
288 root_body: Option<hir::HirId>,
290 /// The parent of the root body owner, if the latter is an
291 /// an associated const or method, as impls/traits can also
292 /// have lifetime parameters free in this body.
293 root_parent: Option<ast::NodeId>,
295 /// `parent_map` maps from a scope id to the enclosing scope id;
296 /// this is usually corresponding to the lexical nesting, though
297 /// in the case of closures the parent scope is the innermost
298 /// conditional expression or repeating block. (Note that the
299 /// enclosing scope id for the block associated with a closure is
300 /// the closure itself.)
301 parent_map: FxHashMap<Scope, (Scope, ScopeDepth)>,
303 /// `var_map` maps from a variable or binding id to the block in
304 /// which that variable is declared.
305 var_map: FxHashMap<hir::ItemLocalId, Scope>,
307 /// maps from a node-id to the associated destruction scope (if any)
308 destruction_scopes: FxHashMap<hir::ItemLocalId, Scope>,
310 /// `rvalue_scopes` includes entries for those expressions whose cleanup scope is
311 /// larger than the default. The map goes from the expression id
312 /// to the cleanup scope id. For rvalues not present in this
313 /// table, the appropriate cleanup scope is the innermost
314 /// enclosing statement, conditional expression, or repeating
315 /// block (see `terminating_scopes`).
316 /// In constants, None is used to indicate that certain expressions
317 /// escape into 'static and should have no local cleanup scope.
318 rvalue_scopes: FxHashMap<hir::ItemLocalId, Option<Scope>>,
320 /// Encodes the hierarchy of fn bodies. Every fn body (including
321 /// closures) forms its own distinct region hierarchy, rooted in
322 /// the block that is the fn body. This map points from the id of
323 /// that root block to the id of the root block for the enclosing
324 /// fn, if any. Thus the map structures the fn bodies into a
325 /// hierarchy based on their lexical mapping. This is used to
326 /// handle the relationships between regions in a fn and in a
327 /// closure defined by that fn. See the "Modeling closures"
328 /// section of the README in infer::region_constraints for
330 closure_tree: FxHashMap<hir::ItemLocalId, hir::ItemLocalId>,
332 /// If there are any `yield` nested within a scope, this map
333 /// stores the `Span` of the last one and its index in the
334 /// postorder of the Visitor traversal on the HIR.
336 /// HIR Visitor postorder indexes might seem like a peculiar
337 /// thing to care about. but it turns out that HIR bindings
338 /// and the temporary results of HIR expressions are never
339 /// storage-live at the end of HIR nodes with postorder indexes
340 /// lower than theirs, and therefore don't need to be suspended
341 /// at yield-points at these indexes.
343 /// For an example, suppose we have some code such as:
344 /// ```rust,ignore (example)
345 /// foo(f(), yield y, bar(g()))
348 /// With the HIR tree (calls numbered for expository purposes)
350 /// Call#0(foo, [Call#1(f), Yield(y), Call#2(bar, Call#3(g))])
353 /// Obviously, the result of `f()` was created before the yield
354 /// (and therefore needs to be kept valid over the yield) while
355 /// the result of `g()` occurs after the yield (and therefore
356 /// doesn't). If we want to infer that, we can look at the
357 /// postorder traversal:
359 /// `foo` `f` Call#1 `y` Yield `bar` `g` Call#3 Call#2 Call#0
362 /// In which we can easily see that `Call#1` occurs before the yield,
363 /// and `Call#3` after it.
365 /// To see that this method works, consider:
367 /// Let `D` be our binding/temporary and `U` be our other HIR node, with
368 /// `HIR-postorder(U) < HIR-postorder(D)` (in our example, U would be
369 /// the yield and D would be one of the calls). Let's show that
370 /// `D` is storage-dead at `U`.
372 /// Remember that storage-live/storage-dead refers to the state of
373 /// the *storage*, and does not consider moves/drop flags.
376 /// 1. From the ordering guarantee of HIR visitors (see
377 /// `rustc::hir::intravisit`), `D` does not dominate `U`.
378 /// 2. Therefore, `D` is *potentially* storage-dead at `U` (because
379 /// we might visit `U` without ever getting to `D`).
380 /// 3. However, we guarantee that at each HIR point, each
381 /// binding/temporary is always either always storage-live
382 /// or always storage-dead. This is what is being guaranteed
383 /// by `terminating_scopes` including all blocks where the
384 /// count of executions is not guaranteed.
385 /// 4. By `2.` and `3.`, `D` is *statically* storage-dead at `U`,
388 /// I don't think this property relies on `3.` in an essential way - it
389 /// is probably still correct even if we have "unrestricted" terminating
390 /// scopes. However, why use the complicated proof when a simple one
393 /// A subtle thing: `box` expressions, such as `box (&x, yield 2, &y)`. It
394 /// might seem that a `box` expression creates a `Box<T>` temporary
395 /// when it *starts* executing, at `HIR-preorder(BOX-EXPR)`. That might
396 /// be true in the MIR desugaring, but it is not important in the semantics.
398 /// The reason is that semantically, until the `box` expression returns,
399 /// the values are still owned by their containing expressions. So
400 /// we'll see that `&x`.
401 yield_in_scope: FxHashMap<Scope, (Span, usize)>,
403 /// The number of visit_expr and visit_pat calls done in the body.
404 /// Used to sanity check visit_expr/visit_pat call count when
405 /// calculating generator interiors.
406 body_expr_count: FxHashMap<hir::BodyId, usize>,
409 #[derive(Debug, Copy, Clone)]
411 /// the root of the current region tree. This is typically the id
412 /// of the innermost fn body. Each fn forms its own disjoint tree
413 /// in the region hierarchy. These fn bodies are themselves
414 /// arranged into a tree. See the "Modeling closures" section of
415 /// the README in infer::region_constraints for more
417 root_id: Option<hir::ItemLocalId>,
419 /// The scope that contains any new variables declared, plus its depth in
421 var_parent: Option<(Scope, ScopeDepth)>,
423 /// Region parent of expressions, etc., plus its depth in the scope tree.
424 parent: Option<(Scope, ScopeDepth)>,
427 struct RegionResolutionVisitor<'a, 'tcx: 'a> {
428 tcx: TyCtxt<'a, 'tcx, 'tcx>,
430 // The number of expressions and patterns visited in the current body
431 expr_and_pat_count: usize,
433 // Generated scope tree:
434 scope_tree: ScopeTree,
438 /// `terminating_scopes` is a set containing the ids of each
439 /// statement, or conditional/repeating expression. These scopes
440 /// are calling "terminating scopes" because, when attempting to
441 /// find the scope of a temporary, by default we search up the
442 /// enclosing scopes until we encounter the terminating scope. A
443 /// conditional/repeating expression is one which is not
444 /// guaranteed to execute exactly once upon entering the parent
445 /// scope. This could be because the expression only executes
446 /// conditionally, such as the expression `b` in `a && b`, or
447 /// because the expression may execute many times, such as a loop
448 /// body. The reason that we distinguish such expressions is that,
449 /// upon exiting the parent scope, we cannot statically know how
450 /// many times the expression executed, and thus if the expression
451 /// creates temporaries we cannot know statically how many such
452 /// temporaries we would have to cleanup. Therefore we ensure that
453 /// the temporaries never outlast the conditional/repeating
454 /// expression, preventing the need for dynamic checks and/or
455 /// arbitrary amounts of stack space. Terminating scopes end
456 /// up being contained in a DestructionScope that contains the
457 /// destructor's execution.
458 terminating_scopes: FxHashSet<hir::ItemLocalId>,
461 struct ExprLocatorVisitor {
463 result: Option<usize>,
464 expr_and_pat_count: usize,
467 // This visitor has to have the same visit_expr calls as RegionResolutionVisitor
468 // since `expr_count` is compared against the results there.
469 impl<'tcx> Visitor<'tcx> for ExprLocatorVisitor {
470 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
471 NestedVisitorMap::None
474 fn visit_pat(&mut self, pat: &'tcx Pat) {
475 intravisit::walk_pat(self, pat);
477 self.expr_and_pat_count += 1;
479 if pat.hir_id == self.hir_id {
480 self.result = Some(self.expr_and_pat_count);
484 fn visit_expr(&mut self, expr: &'tcx Expr) {
485 debug!("ExprLocatorVisitor - pre-increment {} expr = {:?}",
486 self.expr_and_pat_count,
489 intravisit::walk_expr(self, expr);
491 self.expr_and_pat_count += 1;
493 debug!("ExprLocatorVisitor - post-increment {} expr = {:?}",
494 self.expr_and_pat_count,
497 if expr.hir_id == self.hir_id {
498 self.result = Some(self.expr_and_pat_count);
503 impl<'tcx> ScopeTree {
504 pub fn record_scope_parent(&mut self, child: Scope, parent: Option<(Scope, ScopeDepth)>) {
505 debug!("{:?}.parent = {:?}", child, parent);
507 if let Some(p) = parent {
508 let prev = self.parent_map.insert(child, p);
509 assert!(prev.is_none());
512 // record the destruction scopes for later so we can query them
513 if let ScopeData::Destruction(n) = child.data() {
514 self.destruction_scopes.insert(n, child);
518 pub fn each_encl_scope<E>(&self, mut e:E) where E: FnMut(Scope, Scope) {
519 for (&child, &parent) in &self.parent_map {
524 pub fn each_var_scope<E>(&self, mut e:E) where E: FnMut(&hir::ItemLocalId, Scope) {
525 for (child, &parent) in self.var_map.iter() {
530 pub fn opt_destruction_scope(&self, n: hir::ItemLocalId) -> Option<Scope> {
531 self.destruction_scopes.get(&n).cloned()
534 /// Records that `sub_closure` is defined within `sup_closure`. These ids
535 /// should be the id of the block that is the fn body, which is
536 /// also the root of the region hierarchy for that fn.
537 fn record_closure_parent(&mut self,
538 sub_closure: hir::ItemLocalId,
539 sup_closure: hir::ItemLocalId) {
540 debug!("record_closure_parent(sub_closure={:?}, sup_closure={:?})",
541 sub_closure, sup_closure);
542 assert!(sub_closure != sup_closure);
543 let previous = self.closure_tree.insert(sub_closure, sup_closure);
544 assert!(previous.is_none());
547 fn record_var_scope(&mut self, var: hir::ItemLocalId, lifetime: Scope) {
548 debug!("record_var_scope(sub={:?}, sup={:?})", var, lifetime);
549 assert!(var != lifetime.item_local_id());
550 self.var_map.insert(var, lifetime);
553 fn record_rvalue_scope(&mut self, var: hir::ItemLocalId, lifetime: Option<Scope>) {
554 debug!("record_rvalue_scope(sub={:?}, sup={:?})", var, lifetime);
555 if let Some(lifetime) = lifetime {
556 assert!(var != lifetime.item_local_id());
558 self.rvalue_scopes.insert(var, lifetime);
561 pub fn opt_encl_scope(&self, id: Scope) -> Option<Scope> {
562 //! Returns the narrowest scope that encloses `id`, if any.
563 self.parent_map.get(&id).cloned().map(|(p, _)| p)
566 #[allow(dead_code)] // used in cfg
567 pub fn encl_scope(&self, id: Scope) -> Scope {
568 //! Returns the narrowest scope that encloses `id`, if any.
569 self.opt_encl_scope(id).unwrap()
572 /// Returns the lifetime of the local variable `var_id`
573 pub fn var_scope(&self, var_id: hir::ItemLocalId) -> Scope {
574 match self.var_map.get(&var_id) {
576 None => { bug!("no enclosing scope for id {:?}", var_id); }
580 pub fn temporary_scope(&self, expr_id: hir::ItemLocalId) -> Option<Scope> {
581 //! Returns the scope when temp created by expr_id will be cleaned up
583 // check for a designated rvalue scope
584 if let Some(&s) = self.rvalue_scopes.get(&expr_id) {
585 debug!("temporary_scope({:?}) = {:?} [custom]", expr_id, s);
589 // else, locate the innermost terminating scope
590 // if there's one. Static items, for instance, won't
591 // have an enclosing scope, hence no scope will be
593 let mut id = Scope::Node(expr_id);
595 while let Some(&(p, _)) = self.parent_map.get(&id) {
597 ScopeData::Destruction(..) => {
598 debug!("temporary_scope({:?}) = {:?} [enclosing]",
606 debug!("temporary_scope({:?}) = None", expr_id);
610 pub fn var_region(&self, id: hir::ItemLocalId) -> ty::RegionKind {
611 //! Returns the lifetime of the variable `id`.
613 let scope = ty::ReScope(self.var_scope(id));
614 debug!("var_region({:?}) = {:?}", id, scope);
618 pub fn scopes_intersect(&self, scope1: Scope, scope2: Scope)
620 self.is_subscope_of(scope1, scope2) ||
621 self.is_subscope_of(scope2, scope1)
624 /// Returns true if `subscope` is equal to or is lexically nested inside `superscope` and false
626 pub fn is_subscope_of(&self,
630 let mut s = subscope;
631 debug!("is_subscope_of({:?}, {:?})", subscope, superscope);
632 while superscope != s {
633 match self.opt_encl_scope(s) {
635 debug!("is_subscope_of({:?}, {:?}, s={:?})=false",
636 subscope, superscope, s);
639 Some(scope) => s = scope
643 debug!("is_subscope_of({:?}, {:?})=true",
644 subscope, superscope);
649 /// Returns the id of the innermost containing body
650 pub fn containing_body(&self, mut scope: Scope)-> Option<hir::ItemLocalId> {
652 if let ScopeData::CallSite(id) = scope.data() {
656 match self.opt_encl_scope(scope) {
658 Some(parent) => scope = parent,
663 /// Finds the nearest common ancestor of two scopes. That is, finds the
664 /// smallest scope which is greater than or equal to both `scope_a` and
666 pub fn nearest_common_ancestor(&self, scope_a: Scope, scope_b: Scope) -> Scope {
667 if scope_a == scope_b { return scope_a; }
672 // Get the depth of each scope's parent. If either scope has no parent,
673 // it must be the root, which means we can stop immediately because the
674 // root must be the nearest common ancestor. (In practice, this is
675 // moderately common.)
676 let (parent_a, parent_a_depth) = match self.parent_map.get(&a) {
680 let (parent_b, parent_b_depth) = match self.parent_map.get(&b) {
685 if parent_a_depth > parent_b_depth {
686 // `a` is lower than `b`. Move `a` up until it's at the same depth
687 // as `b`. The first move up is trivial because we already found
688 // `parent_a` above; the loop does the remaining N-1 moves.
690 for _ in 0..(parent_a_depth - parent_b_depth - 1) {
691 a = self.parent_map.get(&a).unwrap().0;
693 } else if parent_b_depth > parent_a_depth {
694 // `b` is lower than `a`.
696 for _ in 0..(parent_b_depth - parent_a_depth - 1) {
697 b = self.parent_map.get(&b).unwrap().0;
700 // Both scopes are at the same depth, and we know they're not equal
701 // because that case was tested for at the top of this function. So
702 // we can trivially move them both up one level now.
703 assert!(parent_a_depth != 0);
708 // Now both scopes are at the same level. We move upwards in lockstep
709 // until they match. In practice, this loop is almost always executed
710 // zero times because `a` is almost always a direct ancestor of `b` or
713 a = self.parent_map.get(&a).unwrap().0;
714 b = self.parent_map.get(&b).unwrap().0;
720 /// Assuming that the provided region was defined within this `ScopeTree`,
721 /// returns the outermost `Scope` that the region outlives.
722 pub fn early_free_scope<'a, 'gcx>(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>,
723 br: &ty::EarlyBoundRegion)
725 let param_owner = tcx.parent_def_id(br.def_id).unwrap();
727 let param_owner_id = tcx.hir.as_local_node_id(param_owner).unwrap();
728 let scope = tcx.hir.maybe_body_owned_by(param_owner_id).map(|body_id| {
729 tcx.hir.body(body_id).value.hir_id.local_id
730 }).unwrap_or_else(|| {
731 // The lifetime was defined on node that doesn't own a body,
732 // which in practice can only mean a trait or an impl, that
733 // is the parent of a method, and that is enforced below.
734 assert_eq!(Some(param_owner_id), self.root_parent,
735 "free_scope: {:?} not recognized by the \
736 region scope tree for {:?} / {:?}",
738 self.root_parent.map(|id| tcx.hir.local_def_id(id)),
739 self.root_body.map(|hir_id| DefId::local(hir_id.owner)));
741 // The trait/impl lifetime is in scope for the method's body.
742 self.root_body.unwrap().local_id
745 Scope::CallSite(scope)
748 /// Assuming that the provided region was defined within this `ScopeTree`,
749 /// returns the outermost `Scope` that the region outlives.
750 pub fn free_scope<'a, 'gcx>(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, fr: &ty::FreeRegion)
752 let param_owner = match fr.bound_region {
753 ty::BoundRegion::BrNamed(def_id, _) => {
754 tcx.parent_def_id(def_id).unwrap()
759 // Ensure that the named late-bound lifetimes were defined
760 // on the same function that they ended up being freed in.
761 assert_eq!(param_owner, fr.scope);
763 let param_owner_id = tcx.hir.as_local_node_id(param_owner).unwrap();
764 let body_id = tcx.hir.body_owned_by(param_owner_id);
765 Scope::CallSite(tcx.hir.body(body_id).value.hir_id.local_id)
768 /// Checks whether the given scope contains a `yield`. If so,
769 /// returns `Some((span, expr_count))` with the span of a yield we found and
770 /// the number of expressions and patterns appearing before the `yield` in the body + 1.
771 /// If there a are multiple yields in a scope, the one with the highest number is returned.
772 pub fn yield_in_scope(&self, scope: Scope) -> Option<(Span, usize)> {
773 self.yield_in_scope.get(&scope).cloned()
776 /// Checks whether the given scope contains a `yield` and if that yield could execute
777 /// after `expr`. If so, it returns the span of that `yield`.
778 /// `scope` must be inside the body.
779 pub fn yield_in_scope_for_expr(&self,
781 expr_hir_id: hir::HirId,
782 body: &'tcx hir::Body) -> Option<Span> {
783 self.yield_in_scope(scope).and_then(|(span, count)| {
784 let mut visitor = ExprLocatorVisitor {
787 expr_and_pat_count: 0,
789 visitor.visit_body(body);
790 if count >= visitor.result.unwrap() {
798 /// Gives the number of expressions visited in a body.
799 /// Used to sanity check visit_expr call count when
800 /// calculating generator interiors.
801 pub fn body_expr_count(&self, body_id: hir::BodyId) -> Option<usize> {
802 self.body_expr_count.get(&body_id).map(|r| *r)
806 /// Records the lifetime of a local variable as `cx.var_parent`
807 fn record_var_lifetime(visitor: &mut RegionResolutionVisitor,
808 var_id: hir::ItemLocalId,
810 match visitor.cx.var_parent {
812 // this can happen in extern fn declarations like
814 // extern fn isalnum(c: c_int) -> c_int
816 Some((parent_scope, _)) =>
817 visitor.scope_tree.record_var_scope(var_id, parent_scope),
821 fn resolve_block<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>, blk: &'tcx hir::Block) {
822 debug!("resolve_block(blk.id={:?})", blk.id);
824 let prev_cx = visitor.cx;
826 // We treat the tail expression in the block (if any) somewhat
827 // differently from the statements. The issue has to do with
828 // temporary lifetimes. Consider the following:
831 // let inner = ... (&bar()) ...;
833 // (... (&foo()) ...) // (the tail expression)
834 // }, other_argument());
836 // Each of the statements within the block is a terminating
837 // scope, and thus a temporary (e.g. the result of calling
838 // `bar()` in the initializer expression for `let inner = ...;`)
839 // will be cleaned up immediately after its corresponding
840 // statement (i.e. `let inner = ...;`) executes.
842 // On the other hand, temporaries associated with evaluating the
843 // tail expression for the block are assigned lifetimes so that
844 // they will be cleaned up as part of the terminating scope
845 // *surrounding* the block expression. Here, the terminating
846 // scope for the block expression is the `quux(..)` call; so
847 // those temporaries will only be cleaned up *after* both
848 // `other_argument()` has run and also the call to `quux(..)`
849 // itself has returned.
851 visitor.enter_node_scope_with_dtor(blk.hir_id.local_id);
852 visitor.cx.var_parent = visitor.cx.parent;
855 // This block should be kept approximately in sync with
856 // `intravisit::walk_block`. (We manually walk the block, rather
857 // than call `walk_block`, in order to maintain precise
858 // index information.)
860 for (i, statement) in blk.stmts.iter().enumerate() {
861 if let hir::StmtDecl(..) = statement.node {
862 // Each StmtDecl introduces a subscope for bindings
863 // introduced by the declaration; this subscope covers
864 // a suffix of the block . Each subscope in a block
865 // has the previous subscope in the block as a parent,
866 // except for the first such subscope, which has the
867 // block itself as a parent.
869 Scope::Remainder(BlockRemainder {
870 block: blk.hir_id.local_id,
871 first_statement_index: FirstStatementIndex::new(i)
874 visitor.cx.var_parent = visitor.cx.parent;
876 visitor.visit_stmt(statement)
878 walk_list!(visitor, visit_expr, &blk.expr);
881 visitor.cx = prev_cx;
884 fn resolve_arm<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>, arm: &'tcx hir::Arm) {
885 visitor.terminating_scopes.insert(arm.body.hir_id.local_id);
887 if let Some(ref expr) = arm.guard {
888 visitor.terminating_scopes.insert(expr.hir_id.local_id);
891 intravisit::walk_arm(visitor, arm);
894 fn resolve_pat<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>, pat: &'tcx hir::Pat) {
895 visitor.record_child_scope(Scope::Node(pat.hir_id.local_id));
897 // If this is a binding then record the lifetime of that binding.
898 if let PatKind::Binding(..) = pat.node {
899 record_var_lifetime(visitor, pat.hir_id.local_id, pat.span);
902 debug!("resolve_pat - pre-increment {} pat = {:?}", visitor.expr_and_pat_count, pat);
904 intravisit::walk_pat(visitor, pat);
906 visitor.expr_and_pat_count += 1;
908 debug!("resolve_pat - post-increment {} pat = {:?}", visitor.expr_and_pat_count, pat);
911 fn resolve_stmt<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>, stmt: &'tcx hir::Stmt) {
912 let stmt_id = visitor.tcx.hir.node_to_hir_id(stmt.node.id()).local_id;
913 debug!("resolve_stmt(stmt.id={:?})", stmt_id);
915 // Every statement will clean up the temporaries created during
916 // execution of that statement. Therefore each statement has an
917 // associated destruction scope that represents the scope of the
918 // statement plus its destructors, and thus the scope for which
919 // regions referenced by the destructors need to survive.
920 visitor.terminating_scopes.insert(stmt_id);
922 let prev_parent = visitor.cx.parent;
923 visitor.enter_node_scope_with_dtor(stmt_id);
925 intravisit::walk_stmt(visitor, stmt);
927 visitor.cx.parent = prev_parent;
930 fn resolve_expr<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>, expr: &'tcx hir::Expr) {
931 debug!("resolve_expr - pre-increment {} expr = {:?}", visitor.expr_and_pat_count, expr);
933 let prev_cx = visitor.cx;
934 visitor.enter_node_scope_with_dtor(expr.hir_id.local_id);
937 let terminating_scopes = &mut visitor.terminating_scopes;
938 let mut terminating = |id: hir::ItemLocalId| {
939 terminating_scopes.insert(id);
942 // Conditional or repeating scopes are always terminating
943 // scopes, meaning that temporaries cannot outlive them.
944 // This ensures fixed size stacks.
946 hir::ExprBinary(codemap::Spanned { node: hir::BiAnd, .. }, _, ref r) |
947 hir::ExprBinary(codemap::Spanned { node: hir::BiOr, .. }, _, ref r) => {
948 // For shortcircuiting operators, mark the RHS as a terminating
949 // scope since it only executes conditionally.
950 terminating(r.hir_id.local_id);
953 hir::ExprIf(ref expr, ref then, Some(ref otherwise)) => {
954 terminating(expr.hir_id.local_id);
955 terminating(then.hir_id.local_id);
956 terminating(otherwise.hir_id.local_id);
959 hir::ExprIf(ref expr, ref then, None) => {
960 terminating(expr.hir_id.local_id);
961 terminating(then.hir_id.local_id);
964 hir::ExprLoop(ref body, _, _) => {
965 terminating(body.hir_id.local_id);
968 hir::ExprWhile(ref expr, ref body, _) => {
969 terminating(expr.hir_id.local_id);
970 terminating(body.hir_id.local_id);
973 hir::ExprMatch(..) => {
974 visitor.cx.var_parent = visitor.cx.parent;
977 hir::ExprAssignOp(..) | hir::ExprIndex(..) |
978 hir::ExprUnary(..) | hir::ExprCall(..) | hir::ExprMethodCall(..) => {
979 // FIXME(https://github.com/rust-lang/rfcs/issues/811) Nested method calls
981 // The lifetimes for a call or method call look as follows:
989 // The idea is that call.callee_id represents *the time when
990 // the invoked function is actually running* and call.id
991 // represents *the time to prepare the arguments and make the
992 // call*. See the section "Borrows in Calls" borrowck/README.md
993 // for an extended explanation of why this distinction is
996 // record_superlifetime(new_cx, expr.callee_id);
1004 // Manually recurse over closures, because they are the only
1005 // case of nested bodies that share the parent environment.
1006 hir::ExprClosure(.., body, _, _) => {
1007 let body = visitor.tcx.hir.body(body);
1008 visitor.visit_body(body);
1011 _ => intravisit::walk_expr(visitor, expr)
1014 visitor.expr_and_pat_count += 1;
1016 debug!("resolve_expr post-increment {}, expr = {:?}", visitor.expr_and_pat_count, expr);
1018 if let hir::ExprYield(..) = expr.node {
1019 // Mark this expr's scope and all parent scopes as containing `yield`.
1020 let mut scope = Scope::Node(expr.hir_id.local_id);
1022 visitor.scope_tree.yield_in_scope.insert(scope,
1023 (expr.span, visitor.expr_and_pat_count));
1025 // Keep traversing up while we can.
1026 match visitor.scope_tree.parent_map.get(&scope) {
1027 // Don't cross from closure bodies to their parent.
1028 Some(&(superscope, _)) => match superscope.data() {
1029 ScopeData::CallSite(_) => break,
1030 _ => scope = superscope
1037 visitor.cx = prev_cx;
1040 fn resolve_local<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>,
1041 pat: Option<&'tcx hir::Pat>,
1042 init: Option<&'tcx hir::Expr>) {
1043 debug!("resolve_local(pat={:?}, init={:?})", pat, init);
1045 let blk_scope = visitor.cx.var_parent.map(|(p, _)| p);
1047 // As an exception to the normal rules governing temporary
1048 // lifetimes, initializers in a let have a temporary lifetime
1049 // of the enclosing block. This means that e.g. a program
1050 // like the following is legal:
1052 // let ref x = HashMap::new();
1054 // Because the hash map will be freed in the enclosing block.
1056 // We express the rules more formally based on 3 grammars (defined
1057 // fully in the helpers below that implement them):
1059 // 1. `E&`, which matches expressions like `&<rvalue>` that
1060 // own a pointer into the stack.
1062 // 2. `P&`, which matches patterns like `ref x` or `(ref x, ref
1063 // y)` that produce ref bindings into the value they are
1064 // matched against or something (at least partially) owned by
1065 // the value they are matched against. (By partially owned,
1066 // I mean that creating a binding into a ref-counted or managed value
1067 // would still count.)
1069 // 3. `ET`, which matches both rvalues like `foo()` as well as places
1070 // based on rvalues like `foo().x[2].y`.
1072 // A subexpression `<rvalue>` that appears in a let initializer
1073 // `let pat [: ty] = expr` has an extended temporary lifetime if
1074 // any of the following conditions are met:
1076 // A. `pat` matches `P&` and `expr` matches `ET`
1077 // (covers cases where `pat` creates ref bindings into an rvalue
1078 // produced by `expr`)
1079 // B. `ty` is a borrowed pointer and `expr` matches `ET`
1080 // (covers cases where coercion creates a borrow)
1081 // C. `expr` matches `E&`
1082 // (covers cases `expr` borrows an rvalue that is then assigned
1083 // to memory (at least partially) owned by the binding)
1085 // Here are some examples hopefully giving an intuition where each
1086 // rule comes into play and why:
1088 // Rule A. `let (ref x, ref y) = (foo().x, 44)`. The rvalue `(22, 44)`
1089 // would have an extended lifetime, but not `foo()`.
1091 // Rule B. `let x = &foo().x`. The rvalue ``foo()` would have extended
1094 // In some cases, multiple rules may apply (though not to the same
1095 // rvalue). For example:
1097 // let ref x = [&a(), &b()];
1099 // Here, the expression `[...]` has an extended lifetime due to rule
1100 // A, but the inner rvalues `a()` and `b()` have an extended lifetime
1103 if let Some(expr) = init {
1104 record_rvalue_scope_if_borrow_expr(visitor, &expr, blk_scope);
1106 if let Some(pat) = pat {
1107 if is_binding_pat(pat) {
1108 record_rvalue_scope(visitor, &expr, blk_scope);
1113 // Make sure we visit the initializer first, so expr_and_pat_count remains correct
1114 if let Some(expr) = init {
1115 visitor.visit_expr(expr);
1117 if let Some(pat) = pat {
1118 visitor.visit_pat(pat);
1121 /// True if `pat` match the `P&` nonterminal:
1124 /// | StructName { ..., P&, ... }
1125 /// | VariantName(..., P&, ...)
1126 /// | [ ..., P&, ... ]
1127 /// | ( ..., P&, ... )
1129 fn is_binding_pat(pat: &hir::Pat) -> bool {
1130 // Note that the code below looks for *explicit* refs only, that is, it won't
1131 // know about *implicit* refs as introduced in #42640.
1133 // This is not a problem. For example, consider
1135 // let (ref x, ref y) = (Foo { .. }, Bar { .. });
1137 // Due to the explicit refs on the left hand side, the below code would signal
1138 // that the temporary value on the right hand side should live until the end of
1139 // the enclosing block (as opposed to being dropped after the let is complete).
1141 // To create an implicit ref, however, you must have a borrowed value on the RHS
1142 // already, as in this example (which won't compile before #42640):
1144 // let Foo { x, .. } = &Foo { x: ..., ... };
1148 // let Foo { ref x, .. } = Foo { ... };
1150 // In the former case (the implicit ref version), the temporary is created by the
1151 // & expression, and its lifetime would be extended to the end of the block (due
1152 // to a different rule, not the below code).
1154 PatKind::Binding(hir::BindingAnnotation::Ref, ..) |
1155 PatKind::Binding(hir::BindingAnnotation::RefMut, ..) => true,
1157 PatKind::Struct(_, ref field_pats, _) => {
1158 field_pats.iter().any(|fp| is_binding_pat(&fp.node.pat))
1161 PatKind::Slice(ref pats1, ref pats2, ref pats3) => {
1162 pats1.iter().any(|p| is_binding_pat(&p)) ||
1163 pats2.iter().any(|p| is_binding_pat(&p)) ||
1164 pats3.iter().any(|p| is_binding_pat(&p))
1167 PatKind::TupleStruct(_, ref subpats, _) |
1168 PatKind::Tuple(ref subpats, _) => {
1169 subpats.iter().any(|p| is_binding_pat(&p))
1172 PatKind::Box(ref subpat) => {
1173 is_binding_pat(&subpat)
1180 /// If `expr` matches the `E&` grammar, then records an extended rvalue scope as appropriate:
1183 /// | StructName { ..., f: E&, ... }
1184 /// | [ ..., E&, ... ]
1185 /// | ( ..., E&, ... )
1190 fn record_rvalue_scope_if_borrow_expr<'a, 'tcx>(
1191 visitor: &mut RegionResolutionVisitor<'a, 'tcx>,
1193 blk_id: Option<Scope>)
1196 hir::ExprAddrOf(_, ref subexpr) => {
1197 record_rvalue_scope_if_borrow_expr(visitor, &subexpr, blk_id);
1198 record_rvalue_scope(visitor, &subexpr, blk_id);
1200 hir::ExprStruct(_, ref fields, _) => {
1201 for field in fields {
1202 record_rvalue_scope_if_borrow_expr(
1203 visitor, &field.expr, blk_id);
1206 hir::ExprArray(ref subexprs) |
1207 hir::ExprTup(ref subexprs) => {
1208 for subexpr in subexprs {
1209 record_rvalue_scope_if_borrow_expr(
1210 visitor, &subexpr, blk_id);
1213 hir::ExprCast(ref subexpr, _) => {
1214 record_rvalue_scope_if_borrow_expr(visitor, &subexpr, blk_id)
1216 hir::ExprBlock(ref block, _) => {
1217 if let Some(ref subexpr) = block.expr {
1218 record_rvalue_scope_if_borrow_expr(
1219 visitor, &subexpr, blk_id);
1226 /// Applied to an expression `expr` if `expr` -- or something owned or partially owned by
1227 /// `expr` -- is going to be indirectly referenced by a variable in a let statement. In that
1228 /// case, the "temporary lifetime" or `expr` is extended to be the block enclosing the `let`
1231 /// More formally, if `expr` matches the grammar `ET`, record the rvalue scope of the matching
1232 /// `<rvalue>` as `blk_id`:
1240 /// Note: ET is intended to match "rvalues or places based on rvalues".
1241 fn record_rvalue_scope<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>,
1243 blk_scope: Option<Scope>) {
1244 let mut expr = expr;
1246 // Note: give all the expressions matching `ET` with the
1247 // extended temporary lifetime, not just the innermost rvalue,
1248 // because in codegen if we must compile e.g. `*rvalue()`
1249 // into a temporary, we request the temporary scope of the
1250 // outer expression.
1251 visitor.scope_tree.record_rvalue_scope(expr.hir_id.local_id, blk_scope);
1254 hir::ExprAddrOf(_, ref subexpr) |
1255 hir::ExprUnary(hir::UnDeref, ref subexpr) |
1256 hir::ExprField(ref subexpr, _) |
1257 hir::ExprIndex(ref subexpr, _) => {
1268 impl<'a, 'tcx> RegionResolutionVisitor<'a, 'tcx> {
1269 /// Records the current parent (if any) as the parent of `child_scope`.
1270 /// Returns the depth of `child_scope`.
1271 fn record_child_scope(&mut self, child_scope: Scope) -> ScopeDepth {
1272 let parent = self.cx.parent;
1273 self.scope_tree.record_scope_parent(child_scope, parent);
1274 // If `child_scope` has no parent, it must be the root node, and so has
1275 // a depth of 1. Otherwise, its depth is one more than its parent's.
1276 parent.map_or(1, |(_p, d)| d + 1)
1279 /// Records the current parent (if any) as the parent of `child_scope`,
1280 /// and sets `child_scope` as the new current parent.
1281 fn enter_scope(&mut self, child_scope: Scope) {
1282 let child_depth = self.record_child_scope(child_scope);
1283 self.cx.parent = Some((child_scope, child_depth));
1286 fn enter_node_scope_with_dtor(&mut self, id: hir::ItemLocalId) {
1287 // If node was previously marked as a terminating scope during the
1288 // recursive visit of its parent node in the AST, then we need to
1289 // account for the destruction scope representing the scope of
1290 // the destructors that run immediately after it completes.
1291 if self.terminating_scopes.contains(&id) {
1292 self.enter_scope(Scope::Destruction(id));
1294 self.enter_scope(Scope::Node(id));
1298 impl<'a, 'tcx> Visitor<'tcx> for RegionResolutionVisitor<'a, 'tcx> {
1299 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1300 NestedVisitorMap::None
1303 fn visit_block(&mut self, b: &'tcx Block) {
1304 resolve_block(self, b);
1307 fn visit_body(&mut self, body: &'tcx hir::Body) {
1308 let body_id = body.id();
1309 let owner_id = self.tcx.hir.body_owner(body_id);
1311 debug!("visit_body(id={:?}, span={:?}, body.id={:?}, cx.parent={:?})",
1313 self.tcx.sess.codemap().span_to_string(body.value.span),
1317 let outer_ec = mem::replace(&mut self.expr_and_pat_count, 0);
1318 let outer_cx = self.cx;
1319 let outer_ts = mem::replace(&mut self.terminating_scopes, FxHashSet());
1320 self.terminating_scopes.insert(body.value.hir_id.local_id);
1322 if let Some(root_id) = self.cx.root_id {
1323 self.scope_tree.record_closure_parent(body.value.hir_id.local_id, root_id);
1325 self.cx.root_id = Some(body.value.hir_id.local_id);
1327 self.enter_scope(Scope::CallSite(body.value.hir_id.local_id));
1328 self.enter_scope(Scope::Arguments(body.value.hir_id.local_id));
1330 // The arguments and `self` are parented to the fn.
1331 self.cx.var_parent = self.cx.parent.take();
1332 for argument in &body.arguments {
1333 self.visit_pat(&argument.pat);
1336 // The body of the every fn is a root scope.
1337 self.cx.parent = self.cx.var_parent;
1338 if let hir::BodyOwnerKind::Fn = self.tcx.hir.body_owner_kind(owner_id) {
1339 self.visit_expr(&body.value);
1341 // Only functions have an outer terminating (drop) scope, while
1342 // temporaries in constant initializers may be 'static, but only
1343 // according to rvalue lifetime semantics, using the same
1344 // syntactical rules used for let initializers.
1346 // E.g. in `let x = &f();`, the temporary holding the result from
1347 // the `f()` call lives for the entirety of the surrounding block.
1349 // Similarly, `const X: ... = &f();` would have the result of `f()`
1350 // live for `'static`, implying (if Drop restrictions on constants
1351 // ever get lifted) that the value *could* have a destructor, but
1352 // it'd get leaked instead of the destructor running during the
1353 // evaluation of `X` (if at all allowed by CTFE).
1355 // However, `const Y: ... = g(&f());`, like `let y = g(&f());`,
1356 // would *not* let the `f()` temporary escape into an outer scope
1357 // (i.e. `'static`), which means that after `g` returns, it drops,
1358 // and all the associated destruction scope rules apply.
1359 self.cx.var_parent = None;
1360 resolve_local(self, None, Some(&body.value));
1363 if body.is_generator {
1364 self.scope_tree.body_expr_count.insert(body_id, self.expr_and_pat_count);
1367 // Restore context we had at the start.
1368 self.expr_and_pat_count = outer_ec;
1370 self.terminating_scopes = outer_ts;
1373 fn visit_arm(&mut self, a: &'tcx Arm) {
1374 resolve_arm(self, a);
1376 fn visit_pat(&mut self, p: &'tcx Pat) {
1377 resolve_pat(self, p);
1379 fn visit_stmt(&mut self, s: &'tcx Stmt) {
1380 resolve_stmt(self, s);
1382 fn visit_expr(&mut self, ex: &'tcx Expr) {
1383 resolve_expr(self, ex);
1385 fn visit_local(&mut self, l: &'tcx Local) {
1386 resolve_local(self, Some(&l.pat), l.init.as_ref().map(|e| &**e));
1390 fn region_scope_tree<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId)
1393 let closure_base_def_id = tcx.closure_base_def_id(def_id);
1394 if closure_base_def_id != def_id {
1395 return tcx.region_scope_tree(closure_base_def_id);
1398 let id = tcx.hir.as_local_node_id(def_id).unwrap();
1399 let scope_tree = if let Some(body_id) = tcx.hir.maybe_body_owned_by(id) {
1400 let mut visitor = RegionResolutionVisitor {
1402 scope_tree: ScopeTree::default(),
1403 expr_and_pat_count: 0,
1409 terminating_scopes: FxHashSet(),
1412 let body = tcx.hir.body(body_id);
1413 visitor.scope_tree.root_body = Some(body.value.hir_id);
1415 // If the item is an associated const or a method,
1416 // record its impl/trait parent, as it can also have
1417 // lifetime parameters free in this body.
1418 match tcx.hir.get(id) {
1419 hir::map::NodeImplItem(_) |
1420 hir::map::NodeTraitItem(_) => {
1421 visitor.scope_tree.root_parent = Some(tcx.hir.get_parent(id));
1426 visitor.visit_body(body);
1430 ScopeTree::default()
1433 Lrc::new(scope_tree)
1436 pub fn provide(providers: &mut Providers) {
1437 *providers = Providers {
1443 impl<'a> HashStable<StableHashingContext<'a>> for ScopeTree {
1444 fn hash_stable<W: StableHasherResult>(&self,
1445 hcx: &mut StableHashingContext<'a>,
1446 hasher: &mut StableHasher<W>) {
1450 ref body_expr_count,
1453 ref destruction_scopes,
1459 hcx.with_node_id_hashing_mode(NodeIdHashingMode::HashDefPath, |hcx| {
1460 root_body.hash_stable(hcx, hasher);
1461 root_parent.hash_stable(hcx, hasher);
1464 body_expr_count.hash_stable(hcx, hasher);
1465 parent_map.hash_stable(hcx, hasher);
1466 var_map.hash_stable(hcx, hasher);
1467 destruction_scopes.hash_stable(hcx, hasher);
1468 rvalue_scopes.hash_stable(hcx, hasher);
1469 closure_tree.hash_stable(hcx, hasher);
1470 yield_in_scope.hash_stable(hcx, hasher);