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Move region_scope_tree query to librustc_passes.

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This commit is contained in:
Camille GILLOT 2019-12-29 10:59:15 +01:00
parent ca5a10f53e
commit afcd5c16b7
4 changed files with 682 additions and 718 deletions
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src/librustc/middle/region.rs Normal file
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//! This file builds up the `ScopeTree`, which describes
//! the parent links in the region hierarchy.
//!
//! For more information about how MIR-based region-checking works,
//! see the [rustc guide].
//!
//! [rustc guide]: https://rust-lang.github.io/rustc-guide/mir/borrowck.html
use crate::hir;
use crate::hir::def_id::DefId;
use crate::hir::Node;
use crate::ich::{NodeIdHashingMode, StableHashingContext};
use crate::ty::{self, DefIdTree, TyCtxt};
use crate::util::nodemap::FxHashMap;
use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
use rustc_index::vec::Idx;
use rustc_macros::HashStable;
use syntax_pos::{Span, DUMMY_SP};
use std::fmt;
/// Represents a statically-describable scope that can be used to
/// bound the lifetime/region for values.
///
/// `Node(node_id)`: Any AST node that has any scope at all has the
/// `Node(node_id)` scope. Other variants represent special cases not
/// immediately derivable from the abstract syntax tree structure.
///
/// `DestructionScope(node_id)` represents the scope of destructors
/// implicitly-attached to `node_id` that run immediately after the
/// expression for `node_id` itself. Not every AST node carries a
/// `DestructionScope`, but those that are `terminating_scopes` do;
/// see discussion with `ScopeTree`.
///
/// `Remainder { block, statement_index }` represents
/// the scope of user code running immediately after the initializer
/// expression for the indexed statement, until the end of the block.
///
/// So: the following code can be broken down into the scopes beneath:
///
/// ```text
/// let a = f().g( 'b: { let x = d(); let y = d(); x.h(y) } ) ;
///
/// +-+ (D12.)
/// +-+ (D11.)
/// +---------+ (R10.)
/// +-+ (D9.)
/// +----------+ (M8.)
/// +----------------------+ (R7.)
/// +-+ (D6.)
/// +----------+ (M5.)
/// +-----------------------------------+ (M4.)
/// +--------------------------------------------------+ (M3.)
/// +--+ (M2.)
/// +-----------------------------------------------------------+ (M1.)
///
/// (M1.): Node scope of the whole `let a = ...;` statement.
/// (M2.): Node scope of the `f()` expression.
/// (M3.): Node scope of the `f().g(..)` expression.
/// (M4.): Node scope of the block labeled `'b:`.
/// (M5.): Node scope of the `let x = d();` statement
/// (D6.): DestructionScope for temporaries created during M5.
/// (R7.): Remainder scope for block `'b:`, stmt 0 (let x = ...).
/// (M8.): Node scope of the `let y = d();` statement.
/// (D9.): DestructionScope for temporaries created during M8.
/// (R10.): Remainder scope for block `'b:`, stmt 1 (let y = ...).
/// (D11.): DestructionScope for temporaries and bindings from block `'b:`.
/// (D12.): DestructionScope for temporaries created during M1 (e.g., f()).
/// ```
///
/// Note that while the above picture shows the destruction scopes
/// as following their corresponding node scopes, in the internal
/// data structures of the compiler the destruction scopes are
/// represented as enclosing parents. This is sound because we use the
/// enclosing parent relationship just to ensure that referenced
/// values live long enough; phrased another way, the starting point
/// of each range is not really the important thing in the above
/// picture, but rather the ending point.
//
// FIXME(pnkfelix): this currently derives `PartialOrd` and `Ord` to
// placate the same deriving in `ty::FreeRegion`, but we may want to
// actually attach a more meaningful ordering to scopes than the one
// generated via deriving here.
#[derive(
Clone,
PartialEq,
PartialOrd,
Eq,
Ord,
Hash,
Copy,
RustcEncodable,
RustcDecodable,
HashStable
)]
pub struct Scope {
pub id: hir::ItemLocalId,
pub data: ScopeData,
}
impl fmt::Debug for Scope {
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
match self.data {
ScopeData::Node => write!(fmt, "Node({:?})", self.id),
ScopeData::CallSite => write!(fmt, "CallSite({:?})", self.id),
ScopeData::Arguments => write!(fmt, "Arguments({:?})", self.id),
ScopeData::Destruction => write!(fmt, "Destruction({:?})", self.id),
ScopeData::Remainder(fsi) => write!(
fmt,
"Remainder {{ block: {:?}, first_statement_index: {}}}",
self.id,
fsi.as_u32(),
),
}
}
}
#[derive(
Clone,
PartialEq,
PartialOrd,
Eq,
Ord,
Hash,
Debug,
Copy,
RustcEncodable,
RustcDecodable,
HashStable
)]
pub enum ScopeData {
Node,
/// Scope of the call-site for a function or closure
/// (outlives the arguments as well as the body).
CallSite,
/// Scope of arguments passed to a function or closure
/// (they outlive its body).
Arguments,
/// Scope of destructors for temporaries of node-id.
Destruction,
/// Scope following a `let id = expr;` binding in a block.
Remainder(FirstStatementIndex),
}
rustc_index::newtype_index! {
/// Represents a subscope of `block` for a binding that is introduced
/// by `block.stmts[first_statement_index]`. Such subscopes represent
/// a suffix of the block. Note that each subscope does not include
/// the initializer expression, if any, for the statement indexed by
/// `first_statement_index`.
///
/// For example, given `{ let (a, b) = EXPR_1; let c = EXPR_2; ... }`:
///
/// * The subscope with `first_statement_index == 0` is scope of both
/// `a` and `b`; it does not include EXPR_1, but does include
/// everything after that first `let`. (If you want a scope that
/// includes EXPR_1 as well, then do not use `Scope::Remainder`,
/// but instead another `Scope` that encompasses the whole block,
/// e.g., `Scope::Node`.
///
/// * The subscope with `first_statement_index == 1` is scope of `c`,
/// and thus does not include EXPR_2, but covers the `...`.
pub struct FirstStatementIndex {
derive [HashStable]
}
}
// compilation error if size of `ScopeData` is not the same as a `u32`
static_assert_size!(ScopeData, 4);
impl Scope {
/// Returns a item-local ID associated with this scope.
///
/// N.B., likely to be replaced as API is refined; e.g., pnkfelix
/// anticipates `fn entry_node_id` and `fn each_exit_node_id`.
pub fn item_local_id(&self) -> hir::ItemLocalId {
self.id
}
pub fn hir_id(&self, scope_tree: &ScopeTree) -> hir::HirId {
match scope_tree.root_body {
Some(hir_id) => hir::HirId { owner: hir_id.owner, local_id: self.item_local_id() },
None => hir::DUMMY_HIR_ID,
}
}
/// Returns the span of this `Scope`. Note that in general the
/// returned span may not correspond to the span of any `NodeId` in
/// the AST.
pub fn span(&self, tcx: TyCtxt<'_>, scope_tree: &ScopeTree) -> Span {
let hir_id = self.hir_id(scope_tree);
if hir_id == hir::DUMMY_HIR_ID {
return DUMMY_SP;
}
let span = tcx.hir().span(hir_id);
if let ScopeData::Remainder(first_statement_index) = self.data {
if let Node::Block(ref blk) = tcx.hir().get(hir_id) {
// Want span for scope starting after the
// indexed statement and ending at end of
// `blk`; reuse span of `blk` and shift `lo`
// forward to end of indexed statement.
//
// (This is the special case aluded to in the
// doc-comment for this method)
let stmt_span = blk.stmts[first_statement_index.index()].span;
// To avoid issues with macro-generated spans, the span
// of the statement must be nested in that of the block.
if span.lo() <= stmt_span.lo() && stmt_span.lo() <= span.hi() {
return Span::new(stmt_span.lo(), span.hi(), span.ctxt());
}
}
}
span
}
}
pub type ScopeDepth = u32;
/// The region scope tree encodes information about region relationships.
#[derive(Default, Debug)]
pub struct ScopeTree {
/// If not empty, this body is the root of this region hierarchy.
pub root_body: Option<hir::HirId>,
/// The parent of the root body owner, if the latter is an
/// an associated const or method, as impls/traits can also
/// have lifetime parameters free in this body.
pub root_parent: Option<hir::HirId>,
/// Maps from a scope ID to the enclosing scope id;
/// this is usually corresponding to the lexical nesting, though
/// in the case of closures the parent scope is the innermost
/// conditional expression or repeating block. (Note that the
/// enclosing scope ID for the block associated with a closure is
/// the closure itself.)
pub parent_map: FxHashMap<Scope, (Scope, ScopeDepth)>,
/// Maps from a variable or binding ID to the block in which that
/// variable is declared.
var_map: FxHashMap<hir::ItemLocalId, Scope>,
/// Maps from a `NodeId` to the associated destruction scope (if any).
destruction_scopes: FxHashMap<hir::ItemLocalId, Scope>,
/// `rvalue_scopes` includes entries for those expressions whose
/// cleanup scope is larger than the default. The map goes from the
/// expression ID to the cleanup scope id. For rvalues not present in
/// this table, the appropriate cleanup scope is the innermost
/// enclosing statement, conditional expression, or repeating
/// block (see `terminating_scopes`).
/// In constants, None is used to indicate that certain expressions
/// escape into 'static and should have no local cleanup scope.
rvalue_scopes: FxHashMap<hir::ItemLocalId, Option<Scope>>,
/// Encodes the hierarchy of fn bodies. Every fn body (including
/// closures) forms its own distinct region hierarchy, rooted in
/// the block that is the fn body. This map points from the ID of
/// that root block to the ID of the root block for the enclosing
/// fn, if any. Thus the map structures the fn bodies into a
/// hierarchy based on their lexical mapping. This is used to
/// handle the relationships between regions in a fn and in a
/// closure defined by that fn. See the "Modeling closures"
/// section of the README in infer::region_constraints for
/// more details.
closure_tree: FxHashMap<hir::ItemLocalId, hir::ItemLocalId>,
/// If there are any `yield` nested within a scope, this map
/// stores the `Span` of the last one and its index in the
/// postorder of the Visitor traversal on the HIR.
///
/// HIR Visitor postorder indexes might seem like a peculiar
/// thing to care about. but it turns out that HIR bindings
/// and the temporary results of HIR expressions are never
/// storage-live at the end of HIR nodes with postorder indexes
/// lower than theirs, and therefore don't need to be suspended
/// at yield-points at these indexes.
///
/// For an example, suppose we have some code such as:
/// ```rust,ignore (example)
/// foo(f(), yield y, bar(g()))
/// ```
///
/// With the HIR tree (calls numbered for expository purposes)
/// ```
/// Call#0(foo, [Call#1(f), Yield(y), Call#2(bar, Call#3(g))])
/// ```
///
/// Obviously, the result of `f()` was created before the yield
/// (and therefore needs to be kept valid over the yield) while
/// the result of `g()` occurs after the yield (and therefore
/// doesn't). If we want to infer that, we can look at the
/// postorder traversal:
/// ```plain,ignore
/// `foo` `f` Call#1 `y` Yield `bar` `g` Call#3 Call#2 Call#0
/// ```
///
/// In which we can easily see that `Call#1` occurs before the yield,
/// and `Call#3` after it.
///
/// To see that this method works, consider:
///
/// Let `D` be our binding/temporary and `U` be our other HIR node, with
/// `HIR-postorder(U) < HIR-postorder(D)` (in our example, U would be
/// the yield and D would be one of the calls). Let's show that
/// `D` is storage-dead at `U`.
///
/// Remember that storage-live/storage-dead refers to the state of
/// the *storage*, and does not consider moves/drop flags.
///
/// Then:
/// 1. From the ordering guarantee of HIR visitors (see
/// `rustc::hir::intravisit`), `D` does not dominate `U`.
/// 2. Therefore, `D` is *potentially* storage-dead at `U` (because
/// we might visit `U` without ever getting to `D`).
/// 3. However, we guarantee that at each HIR point, each
/// binding/temporary is always either always storage-live
/// or always storage-dead. This is what is being guaranteed
/// by `terminating_scopes` including all blocks where the
/// count of executions is not guaranteed.
/// 4. By `2.` and `3.`, `D` is *statically* storage-dead at `U`,
/// QED.
///
/// This property ought to not on (3) in an essential way -- it
/// is probably still correct even if we have "unrestricted" terminating
/// scopes. However, why use the complicated proof when a simple one
/// works?
///
/// A subtle thing: `box` expressions, such as `box (&x, yield 2, &y)`. It
/// might seem that a `box` expression creates a `Box<T>` temporary
/// when it *starts* executing, at `HIR-preorder(BOX-EXPR)`. That might
/// be true in the MIR desugaring, but it is not important in the semantics.
///
/// The reason is that semantically, until the `box` expression returns,
/// the values are still owned by their containing expressions. So
/// we'll see that `&x`.
pub yield_in_scope: FxHashMap<Scope, YieldData>,
/// The number of visit_expr and visit_pat calls done in the body.
/// Used to sanity check visit_expr/visit_pat call count when
/// calculating generator interiors.
pub body_expr_count: FxHashMap<hir::BodyId, usize>,
}
#[derive(Debug, Copy, Clone, RustcEncodable, RustcDecodable, HashStable)]
pub struct YieldData {
/// The `Span` of the yield.
pub span: Span,
/// The number of expressions and patterns appearing before the `yield` in the body plus one.
pub expr_and_pat_count: usize,
pub source: hir::YieldSource,
}
impl<'tcx> ScopeTree {
pub fn record_scope_parent(&mut self, child: Scope, parent: Option<(Scope, ScopeDepth)>) {
debug!("{:?}.parent = {:?}", child, parent);
if let Some(p) = parent {
let prev = self.parent_map.insert(child, p);
assert!(prev.is_none());
}
// Record the destruction scopes for later so we can query them.
if let ScopeData::Destruction = child.data {
self.destruction_scopes.insert(child.item_local_id(), child);
}
}
pub fn each_encl_scope<E>(&self, mut e: E)
where
E: FnMut(Scope, Scope),
{
for (&child, &parent) in &self.parent_map {
e(child, parent.0)
}
}
pub fn each_var_scope<E>(&self, mut e: E)
where
E: FnMut(&hir::ItemLocalId, Scope),
{
for (child, &parent) in self.var_map.iter() {
e(child, parent)
}
}
pub fn opt_destruction_scope(&self, n: hir::ItemLocalId) -> Option<Scope> {
self.destruction_scopes.get(&n).cloned()
}
/// Records that `sub_closure` is defined within `sup_closure`. These IDs
/// should be the ID of the block that is the fn body, which is
/// also the root of the region hierarchy for that fn.
pub fn record_closure_parent(
&mut self,
sub_closure: hir::ItemLocalId,
sup_closure: hir::ItemLocalId,
) {
debug!(
"record_closure_parent(sub_closure={:?}, sup_closure={:?})",
sub_closure, sup_closure
);
assert!(sub_closure != sup_closure);
let previous = self.closure_tree.insert(sub_closure, sup_closure);
assert!(previous.is_none());
}
pub fn record_var_scope(&mut self, var: hir::ItemLocalId, lifetime: Scope) {
debug!("record_var_scope(sub={:?}, sup={:?})", var, lifetime);
assert!(var != lifetime.item_local_id());
self.var_map.insert(var, lifetime);
}
pub fn record_rvalue_scope(&mut self, var: hir::ItemLocalId, lifetime: Option<Scope>) {
debug!("record_rvalue_scope(sub={:?}, sup={:?})", var, lifetime);
if let Some(lifetime) = lifetime {
assert!(var != lifetime.item_local_id());
}
self.rvalue_scopes.insert(var, lifetime);
}
/// Returns the narrowest scope that encloses `id`, if any.
pub fn opt_encl_scope(&self, id: Scope) -> Option<Scope> {
self.parent_map.get(&id).cloned().map(|(p, _)| p)
}
/// Returns the narrowest scope that encloses `id`, if any.
#[allow(dead_code)] // used in cfg
pub fn encl_scope(&self, id: Scope) -> Scope {
self.opt_encl_scope(id).unwrap()
}
/// Returns the lifetime of the local variable `var_id`
pub fn var_scope(&self, var_id: hir::ItemLocalId) -> Scope {
self.var_map
.get(&var_id)
.cloned()
.unwrap_or_else(|| bug!("no enclosing scope for id {:?}", var_id))
}
/// Returns the scope when the temp created by `expr_id` will be cleaned up.
pub fn temporary_scope(&self, expr_id: hir::ItemLocalId) -> Option<Scope> {
// Check for a designated rvalue scope.
if let Some(&s) = self.rvalue_scopes.get(&expr_id) {
debug!("temporary_scope({:?}) = {:?} [custom]", expr_id, s);
return s;
}
// Otherwise, locate the innermost terminating scope
// if there's one. Static items, for instance, won't
// have an enclosing scope, hence no scope will be
// returned.
let mut id = Scope { id: expr_id, data: ScopeData::Node };
while let Some(&(p, _)) = self.parent_map.get(&id) {
match p.data {
ScopeData::Destruction => {
debug!("temporary_scope({:?}) = {:?} [enclosing]", expr_id, id);
return Some(id);
}
_ => id = p,
}
}
debug!("temporary_scope({:?}) = None", expr_id);
return None;
}
/// Returns the lifetime of the variable `id`.
pub fn var_region(&self, id: hir::ItemLocalId) -> ty::RegionKind {
let scope = ty::ReScope(self.var_scope(id));
debug!("var_region({:?}) = {:?}", id, scope);
scope
}
pub fn scopes_intersect(&self, scope1: Scope, scope2: Scope) -> bool {
self.is_subscope_of(scope1, scope2) || self.is_subscope_of(scope2, scope1)
}
/// Returns `true` if `subscope` is equal to or is lexically nested inside `superscope`, and
/// `false` otherwise.
pub fn is_subscope_of(&self, subscope: Scope, superscope: Scope) -> bool {
let mut s = subscope;
debug!("is_subscope_of({:?}, {:?})", subscope, superscope);
while superscope != s {
match self.opt_encl_scope(s) {
None => {
debug!("is_subscope_of({:?}, {:?}, s={:?})=false", subscope, superscope, s);
return false;
}
Some(scope) => s = scope,
}
}
debug!("is_subscope_of({:?}, {:?})=true", subscope, superscope);
return true;
}
/// Returns the ID of the innermost containing body.
pub fn containing_body(&self, mut scope: Scope) -> Option<hir::ItemLocalId> {
loop {
if let ScopeData::CallSite = scope.data {
return Some(scope.item_local_id());
}
scope = self.opt_encl_scope(scope)?;
}
}
/// Finds the nearest common ancestor of two scopes. That is, finds the
/// smallest scope which is greater than or equal to both `scope_a` and
/// `scope_b`.
pub fn nearest_common_ancestor(&self, scope_a: Scope, scope_b: Scope) -> Scope {
if scope_a == scope_b {
return scope_a;
}
let mut a = scope_a;
let mut b = scope_b;
// Get the depth of each scope's parent. If either scope has no parent,
// it must be the root, which means we can stop immediately because the
// root must be the nearest common ancestor. (In practice, this is
// moderately common.)
let (parent_a, parent_a_depth) = match self.parent_map.get(&a) {
Some(pd) => *pd,
None => return a,
};
let (parent_b, parent_b_depth) = match self.parent_map.get(&b) {
Some(pd) => *pd,
None => return b,
};
if parent_a_depth > parent_b_depth {
// `a` is lower than `b`. Move `a` up until it's at the same depth
// as `b`. The first move up is trivial because we already found
// `parent_a` above; the loop does the remaining N-1 moves.
a = parent_a;
for _ in 0..(parent_a_depth - parent_b_depth - 1) {
a = self.parent_map.get(&a).unwrap().0;
}
} else if parent_b_depth > parent_a_depth {
// `b` is lower than `a`.
b = parent_b;
for _ in 0..(parent_b_depth - parent_a_depth - 1) {
b = self.parent_map.get(&b).unwrap().0;
}
} else {
// Both scopes are at the same depth, and we know they're not equal
// because that case was tested for at the top of this function. So
// we can trivially move them both up one level now.
assert!(parent_a_depth != 0);
a = parent_a;
b = parent_b;
}
// Now both scopes are at the same level. We move upwards in lockstep
// until they match. In practice, this loop is almost always executed
// zero times because `a` is almost always a direct ancestor of `b` or
// vice versa.
while a != b {
a = self.parent_map.get(&a).unwrap().0;
b = self.parent_map.get(&b).unwrap().0;
}
a
}
/// Assuming that the provided region was defined within this `ScopeTree`,
/// returns the outermost `Scope` that the region outlives.
pub fn early_free_scope(&self, tcx: TyCtxt<'tcx>, br: &ty::EarlyBoundRegion) -> Scope {
let param_owner = tcx.parent(br.def_id).unwrap();
let param_owner_id = tcx.hir().as_local_hir_id(param_owner).unwrap();
let scope = tcx
.hir()
.maybe_body_owned_by(param_owner_id)
.map(|body_id| tcx.hir().body(body_id).value.hir_id.local_id)
.unwrap_or_else(|| {
// The lifetime was defined on node that doesn't own a body,
// which in practice can only mean a trait or an impl, that
// is the parent of a method, and that is enforced below.
if Some(param_owner_id) != self.root_parent {
tcx.sess.delay_span_bug(
DUMMY_SP,
&format!(
"free_scope: {:?} not recognized by the \
region scope tree for {:?} / {:?}",
param_owner,
self.root_parent.map(|id| tcx.hir().local_def_id(id)),
self.root_body.map(|hir_id| DefId::local(hir_id.owner))
),
);
}
// The trait/impl lifetime is in scope for the method's body.
self.root_body.unwrap().local_id
});
Scope { id: scope, data: ScopeData::CallSite }
}
/// Assuming that the provided region was defined within this `ScopeTree`,
/// returns the outermost `Scope` that the region outlives.
pub fn free_scope(&self, tcx: TyCtxt<'tcx>, fr: &ty::FreeRegion) -> Scope {
let param_owner = match fr.bound_region {
ty::BoundRegion::BrNamed(def_id, _) => tcx.parent(def_id).unwrap(),
_ => fr.scope,
};
// Ensure that the named late-bound lifetimes were defined
// on the same function that they ended up being freed in.
assert_eq!(param_owner, fr.scope);
let param_owner_id = tcx.hir().as_local_hir_id(param_owner).unwrap();
let body_id = tcx.hir().body_owned_by(param_owner_id);
Scope { id: tcx.hir().body(body_id).value.hir_id.local_id, data: ScopeData::CallSite }
}
/// Checks whether the given scope contains a `yield`. If so,
/// returns `Some((span, expr_count))` with the span of a yield we found and
/// the number of expressions and patterns appearing before the `yield` in the body + 1.
/// If there a are multiple yields in a scope, the one with the highest number is returned.
pub fn yield_in_scope(&self, scope: Scope) -> Option<YieldData> {
self.yield_in_scope.get(&scope).cloned()
}
/// Gives the number of expressions visited in a body.
/// Used to sanity check visit_expr call count when
/// calculating generator interiors.
pub fn body_expr_count(&self, body_id: hir::BodyId) -> Option<usize> {
self.body_expr_count.get(&body_id).map(|r| *r)
}
}
impl<'a> HashStable<StableHashingContext<'a>> for ScopeTree {
fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
let ScopeTree {
root_body,
root_parent,
ref body_expr_count,
ref parent_map,
ref var_map,
ref destruction_scopes,
ref rvalue_scopes,
ref closure_tree,
ref yield_in_scope,
} = *self;
hcx.with_node_id_hashing_mode(NodeIdHashingMode::HashDefPath, |hcx| {
root_body.hash_stable(hcx, hasher);
root_parent.hash_stable(hcx, hasher);
});
body_expr_count.hash_stable(hcx, hasher);
parent_map.hash_stable(hcx, hasher);
var_map.hash_stable(hcx, hasher);
destruction_scopes.hash_stable(hcx, hasher);
rvalue_scopes.hash_stable(hcx, hasher);
closure_tree.hash_stable(hcx, hasher);
yield_in_scope.hash_stable(hcx, hasher);
}
}

1
src/librustc_interface/passes.rs
View File

@ -686,7 +686,6 @@ pub fn default_provide(providers: &mut ty::query::Providers<'_>) {
stability::provide(providers);
rustc_passes::provide(providers);
rustc_traits::provide(providers);
middle::region::provide(providers);
rustc_metadata::provide(providers);
lint::provide(providers);
rustc_lint::provide(providers);

2
src/librustc_passes/lib.rs
View File

@ -31,6 +31,7 @@ mod lib_features;
mod liveness;
pub mod loops;
mod reachable;
mod region;
pub fn provide(providers: &mut Providers<'_>) {
check_const::provide(providers);
@ -41,4 +42,5 @@ pub fn provide(providers: &mut Providers<'_>) {
liveness::provide(providers);
intrinsicck::provide(providers);
reachable::provide(providers);
region::provide(providers);
}

727
src/librustc_passes/region.rs
View File

@ -6,362 +6,22 @@
//!
//! [rustc guide]: https://rust-lang.github.io/rustc-guide/mir/borrowck.html
use crate::hir;
use crate::hir::def_id::DefId;
use crate::hir::intravisit::{self, NestedVisitorMap, Visitor};
use crate::hir::Node;
use crate::hir::{Arm, Block, Expr, Local, Pat, PatKind, Stmt};
use crate::ich::{NodeIdHashingMode, StableHashingContext};
use crate::ty::query::Providers;
use crate::ty::{self, DefIdTree, TyCtxt};
use crate::util::nodemap::{FxHashMap, FxHashSet};
use rustc::hir;
use rustc::hir::def_id::DefId;
use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
use rustc::hir::Node;
use rustc::hir::{Arm, Block, Expr, Local, Pat, PatKind, Stmt};
use rustc::middle::region::*;
use rustc::ty::query::Providers;
use rustc::ty::TyCtxt;
use rustc::util::nodemap::FxHashSet;
use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
use rustc_index::vec::Idx;
use rustc_macros::HashStable;
use syntax::source_map;
use syntax_pos::{Span, DUMMY_SP};
use syntax_pos::Span;
use std::fmt;
use std::mem;
/// Represents a statically-describable scope that can be used to
/// bound the lifetime/region for values.
///
/// `Node(node_id)`: Any AST node that has any scope at all has the
/// `Node(node_id)` scope. Other variants represent special cases not
/// immediately derivable from the abstract syntax tree structure.
///
/// `DestructionScope(node_id)` represents the scope of destructors
/// implicitly-attached to `node_id` that run immediately after the
/// expression for `node_id` itself. Not every AST node carries a
/// `DestructionScope`, but those that are `terminating_scopes` do;
/// see discussion with `ScopeTree`.
///
/// `Remainder { block, statement_index }` represents
/// the scope of user code running immediately after the initializer
/// expression for the indexed statement, until the end of the block.
///
/// So: the following code can be broken down into the scopes beneath:
///
/// ```text
/// let a = f().g( 'b: { let x = d(); let y = d(); x.h(y) } ) ;
///
/// +-+ (D12.)
/// +-+ (D11.)
/// +---------+ (R10.)
/// +-+ (D9.)
/// +----------+ (M8.)
/// +----------------------+ (R7.)
/// +-+ (D6.)
/// +----------+ (M5.)
/// +-----------------------------------+ (M4.)
/// +--------------------------------------------------+ (M3.)
/// +--+ (M2.)
/// +-----------------------------------------------------------+ (M1.)
///
/// (M1.): Node scope of the whole `let a = ...;` statement.
/// (M2.): Node scope of the `f()` expression.
/// (M3.): Node scope of the `f().g(..)` expression.
/// (M4.): Node scope of the block labeled `'b:`.
/// (M5.): Node scope of the `let x = d();` statement
/// (D6.): DestructionScope for temporaries created during M5.
/// (R7.): Remainder scope for block `'b:`, stmt 0 (let x = ...).
/// (M8.): Node scope of the `let y = d();` statement.
/// (D9.): DestructionScope for temporaries created during M8.
/// (R10.): Remainder scope for block `'b:`, stmt 1 (let y = ...).
/// (D11.): DestructionScope for temporaries and bindings from block `'b:`.
/// (D12.): DestructionScope for temporaries created during M1 (e.g., f()).
/// ```
///
/// Note that while the above picture shows the destruction scopes
/// as following their corresponding node scopes, in the internal
/// data structures of the compiler the destruction scopes are
/// represented as enclosing parents. This is sound because we use the
/// enclosing parent relationship just to ensure that referenced
/// values live long enough; phrased another way, the starting point
/// of each range is not really the important thing in the above
/// picture, but rather the ending point.
//
// FIXME(pnkfelix): this currently derives `PartialOrd` and `Ord` to
// placate the same deriving in `ty::FreeRegion`, but we may want to
// actually attach a more meaningful ordering to scopes than the one
// generated via deriving here.
#[derive(
Clone,
PartialEq,
PartialOrd,
Eq,
Ord,
Hash,
Copy,
RustcEncodable,
RustcDecodable,
HashStable
)]
pub struct Scope {
pub id: hir::ItemLocalId,
pub data: ScopeData,
}
impl fmt::Debug for Scope {
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
match self.data {
ScopeData::Node => write!(fmt, "Node({:?})", self.id),
ScopeData::CallSite => write!(fmt, "CallSite({:?})", self.id),
ScopeData::Arguments => write!(fmt, "Arguments({:?})", self.id),
ScopeData::Destruction => write!(fmt, "Destruction({:?})", self.id),
ScopeData::Remainder(fsi) => write!(
fmt,
"Remainder {{ block: {:?}, first_statement_index: {}}}",
self.id,
fsi.as_u32(),
),
}
}
}
#[derive(
Clone,
PartialEq,
PartialOrd,
Eq,
Ord,
Hash,
Debug,
Copy,
RustcEncodable,
RustcDecodable,
HashStable
)]
pub enum ScopeData {
Node,
/// Scope of the call-site for a function or closure
/// (outlives the arguments as well as the body).
CallSite,
/// Scope of arguments passed to a function or closure
/// (they outlive its body).
Arguments,
/// Scope of destructors for temporaries of node-id.
Destruction,
/// Scope following a `let id = expr;` binding in a block.
Remainder(FirstStatementIndex),
}
rustc_index::newtype_index! {
/// Represents a subscope of `block` for a binding that is introduced
/// by `block.stmts[first_statement_index]`. Such subscopes represent
/// a suffix of the block. Note that each subscope does not include
/// the initializer expression, if any, for the statement indexed by
/// `first_statement_index`.
///
/// For example, given `{ let (a, b) = EXPR_1; let c = EXPR_2; ... }`:
///
/// * The subscope with `first_statement_index == 0` is scope of both
/// `a` and `b`; it does not include EXPR_1, but does include
/// everything after that first `let`. (If you want a scope that
/// includes EXPR_1 as well, then do not use `Scope::Remainder`,
/// but instead another `Scope` that encompasses the whole block,
/// e.g., `Scope::Node`.
///
/// * The subscope with `first_statement_index == 1` is scope of `c`,
/// and thus does not include EXPR_2, but covers the `...`.
pub struct FirstStatementIndex {
derive [HashStable]
}
}
// compilation error if size of `ScopeData` is not the same as a `u32`
static_assert_size!(ScopeData, 4);
impl Scope {
/// Returns a item-local ID associated with this scope.
///
/// N.B., likely to be replaced as API is refined; e.g., pnkfelix
/// anticipates `fn entry_node_id` and `fn each_exit_node_id`.
pub fn item_local_id(&self) -> hir::ItemLocalId {
self.id
}
pub fn hir_id(&self, scope_tree: &ScopeTree) -> hir::HirId {
match scope_tree.root_body {
Some(hir_id) => hir::HirId { owner: hir_id.owner, local_id: self.item_local_id() },
None => hir::DUMMY_HIR_ID,
}
}
/// Returns the span of this `Scope`. Note that in general the
/// returned span may not correspond to the span of any `NodeId` in
/// the AST.
pub fn span(&self, tcx: TyCtxt<'_>, scope_tree: &ScopeTree) -> Span {
let hir_id = self.hir_id(scope_tree);
if hir_id == hir::DUMMY_HIR_ID {
return DUMMY_SP;
}
let span = tcx.hir().span(hir_id);
if let ScopeData::Remainder(first_statement_index) = self.data {
if let Node::Block(ref blk) = tcx.hir().get(hir_id) {
// Want span for scope starting after the
// indexed statement and ending at end of
// `blk`; reuse span of `blk` and shift `lo`
// forward to end of indexed statement.
//
// (This is the special case aluded to in the
// doc-comment for this method)
let stmt_span = blk.stmts[first_statement_index.index()].span;
// To avoid issues with macro-generated spans, the span
// of the statement must be nested in that of the block.
if span.lo() <= stmt_span.lo() && stmt_span.lo() <= span.hi() {
return Span::new(stmt_span.lo(), span.hi(), span.ctxt());
}
}
}
span
}
}
pub type ScopeDepth = u32;
/// The region scope tree encodes information about region relationships.
#[derive(Default, Debug)]
pub struct ScopeTree {
/// If not empty, this body is the root of this region hierarchy.
root_body: Option<hir::HirId>,
/// The parent of the root body owner, if the latter is an
/// an associated const or method, as impls/traits can also
/// have lifetime parameters free in this body.
root_parent: Option<hir::HirId>,
/// Maps from a scope ID to the enclosing scope id;
/// this is usually corresponding to the lexical nesting, though
/// in the case of closures the parent scope is the innermost
/// conditional expression or repeating block. (Note that the
/// enclosing scope ID for the block associated with a closure is
/// the closure itself.)
parent_map: FxHashMap<Scope, (Scope, ScopeDepth)>,
/// Maps from a variable or binding ID to the block in which that
/// variable is declared.
var_map: FxHashMap<hir::ItemLocalId, Scope>,
/// Maps from a `NodeId` to the associated destruction scope (if any).
destruction_scopes: FxHashMap<hir::ItemLocalId, Scope>,
/// `rvalue_scopes` includes entries for those expressions whose
/// cleanup scope is larger than the default. The map goes from the
/// expression ID to the cleanup scope id. For rvalues not present in
/// this table, the appropriate cleanup scope is the innermost
/// enclosing statement, conditional expression, or repeating
/// block (see `terminating_scopes`).
/// In constants, None is used to indicate that certain expressions
/// escape into 'static and should have no local cleanup scope.
rvalue_scopes: FxHashMap<hir::ItemLocalId, Option<Scope>>,
/// Encodes the hierarchy of fn bodies. Every fn body (including
/// closures) forms its own distinct region hierarchy, rooted in
/// the block that is the fn body. This map points from the ID of
/// that root block to the ID of the root block for the enclosing
/// fn, if any. Thus the map structures the fn bodies into a
/// hierarchy based on their lexical mapping. This is used to
/// handle the relationships between regions in a fn and in a
/// closure defined by that fn. See the "Modeling closures"
/// section of the README in infer::region_constraints for
/// more details.
closure_tree: FxHashMap<hir::ItemLocalId, hir::ItemLocalId>,
/// If there are any `yield` nested within a scope, this map
/// stores the `Span` of the last one and its index in the
/// postorder of the Visitor traversal on the HIR.
///
/// HIR Visitor postorder indexes might seem like a peculiar
/// thing to care about. but it turns out that HIR bindings
/// and the temporary results of HIR expressions are never
/// storage-live at the end of HIR nodes with postorder indexes
/// lower than theirs, and therefore don't need to be suspended
/// at yield-points at these indexes.
///
/// For an example, suppose we have some code such as:
/// ```rust,ignore (example)
/// foo(f(), yield y, bar(g()))
/// ```
///
/// With the HIR tree (calls numbered for expository purposes)
/// ```
/// Call#0(foo, [Call#1(f), Yield(y), Call#2(bar, Call#3(g))])
/// ```
///
/// Obviously, the result of `f()` was created before the yield
/// (and therefore needs to be kept valid over the yield) while
/// the result of `g()` occurs after the yield (and therefore
/// doesn't). If we want to infer that, we can look at the
/// postorder traversal:
/// ```plain,ignore
/// `foo` `f` Call#1 `y` Yield `bar` `g` Call#3 Call#2 Call#0
/// ```
///
/// In which we can easily see that `Call#1` occurs before the yield,
/// and `Call#3` after it.
///
/// To see that this method works, consider:
///
/// Let `D` be our binding/temporary and `U` be our other HIR node, with
/// `HIR-postorder(U) < HIR-postorder(D)` (in our example, U would be
/// the yield and D would be one of the calls). Let's show that
/// `D` is storage-dead at `U`.
///
/// Remember that storage-live/storage-dead refers to the state of
/// the *storage*, and does not consider moves/drop flags.
///
/// Then:
/// 1. From the ordering guarantee of HIR visitors (see
/// `rustc::hir::intravisit`), `D` does not dominate `U`.
/// 2. Therefore, `D` is *potentially* storage-dead at `U` (because
/// we might visit `U` without ever getting to `D`).
/// 3. However, we guarantee that at each HIR point, each
/// binding/temporary is always either always storage-live
/// or always storage-dead. This is what is being guaranteed
/// by `terminating_scopes` including all blocks where the
/// count of executions is not guaranteed.
/// 4. By `2.` and `3.`, `D` is *statically* storage-dead at `U`,
/// QED.
///
/// This property ought to not on (3) in an essential way -- it
/// is probably still correct even if we have "unrestricted" terminating
/// scopes. However, why use the complicated proof when a simple one
/// works?
///
/// A subtle thing: `box` expressions, such as `box (&x, yield 2, &y)`. It
/// might seem that a `box` expression creates a `Box<T>` temporary
/// when it *starts* executing, at `HIR-preorder(BOX-EXPR)`. That might
/// be true in the MIR desugaring, but it is not important in the semantics.
///
/// The reason is that semantically, until the `box` expression returns,
/// the values are still owned by their containing expressions. So
/// we'll see that `&x`.
yield_in_scope: FxHashMap<Scope, YieldData>,
/// The number of visit_expr and visit_pat calls done in the body.
/// Used to sanity check visit_expr/visit_pat call count when
/// calculating generator interiors.
body_expr_count: FxHashMap<hir::BodyId, usize>,
}
#[derive(Debug, Copy, Clone, RustcEncodable, RustcDecodable, HashStable)]
pub struct YieldData {
/// The `Span` of the yield.
pub span: Span,
/// The number of expressions and patterns appearing before the `yield` in the body plus one.
pub expr_and_pat_count: usize,
pub source: hir::YieldSource,
}
#[derive(Debug, Copy, Clone)]
pub struct Context {
/// The root of the current region tree. This is typically the id
@ -419,344 +79,6 @@ struct RegionResolutionVisitor<'tcx> {
terminating_scopes: FxHashSet<hir::ItemLocalId>,
}
struct ExprLocatorVisitor {
hir_id: hir::HirId,
result: Option<usize>,
expr_and_pat_count: usize,
}
// This visitor has to have the same `visit_expr` calls as `RegionResolutionVisitor`
// since `expr_count` is compared against the results there.
impl<'tcx> Visitor<'tcx> for ExprLocatorVisitor {
fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
NestedVisitorMap::None
}
fn visit_pat(&mut self, pat: &'tcx Pat<'tcx>) {
intravisit::walk_pat(self, pat);
self.expr_and_pat_count += 1;
if pat.hir_id == self.hir_id {
self.result = Some(self.expr_and_pat_count);
}
}
fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
debug!("ExprLocatorVisitor - pre-increment {} expr = {:?}", self.expr_and_pat_count, expr);
intravisit::walk_expr(self, expr);
self.expr_and_pat_count += 1;
debug!("ExprLocatorVisitor - post-increment {} expr = {:?}", self.expr_and_pat_count, expr);
if expr.hir_id == self.hir_id {
self.result = Some(self.expr_and_pat_count);
}
}
}
impl<'tcx> ScopeTree {
pub fn record_scope_parent(&mut self, child: Scope, parent: Option<(Scope, ScopeDepth)>) {
debug!("{:?}.parent = {:?}", child, parent);
if let Some(p) = parent {
let prev = self.parent_map.insert(child, p);
assert!(prev.is_none());
}
// Record the destruction scopes for later so we can query them.
if let ScopeData::Destruction = child.data {
self.destruction_scopes.insert(child.item_local_id(), child);
}
}
pub fn each_encl_scope<E>(&self, mut e: E)
where
E: FnMut(Scope, Scope),
{
for (&child, &parent) in &self.parent_map {
e(child, parent.0)
}
}
pub fn each_var_scope<E>(&self, mut e: E)
where
E: FnMut(&hir::ItemLocalId, Scope),
{
for (child, &parent) in self.var_map.iter() {
e(child, parent)
}
}
pub fn opt_destruction_scope(&self, n: hir::ItemLocalId) -> Option<Scope> {
self.destruction_scopes.get(&n).cloned()
}
/// Records that `sub_closure` is defined within `sup_closure`. These IDs
/// should be the ID of the block that is the fn body, which is
/// also the root of the region hierarchy for that fn.
fn record_closure_parent(
&mut self,
sub_closure: hir::ItemLocalId,
sup_closure: hir::ItemLocalId,
) {
debug!(
"record_closure_parent(sub_closure={:?}, sup_closure={:?})",
sub_closure, sup_closure
);
assert!(sub_closure != sup_closure);
let previous = self.closure_tree.insert(sub_closure, sup_closure);
assert!(previous.is_none());
}
fn record_var_scope(&mut self, var: hir::ItemLocalId, lifetime: Scope) {
debug!("record_var_scope(sub={:?}, sup={:?})", var, lifetime);
assert!(var != lifetime.item_local_id());
self.var_map.insert(var, lifetime);
}
fn record_rvalue_scope(&mut self, var: hir::ItemLocalId, lifetime: Option<Scope>) {
debug!("record_rvalue_scope(sub={:?}, sup={:?})", var, lifetime);
if let Some(lifetime) = lifetime {
assert!(var != lifetime.item_local_id());
}
self.rvalue_scopes.insert(var, lifetime);
}
/// Returns the narrowest scope that encloses `id`, if any.
pub fn opt_encl_scope(&self, id: Scope) -> Option<Scope> {
self.parent_map.get(&id).cloned().map(|(p, _)| p)
}
/// Returns the narrowest scope that encloses `id`, if any.
#[allow(dead_code)] // used in cfg
pub fn encl_scope(&self, id: Scope) -> Scope {
self.opt_encl_scope(id).unwrap()
}
/// Returns the lifetime of the local variable `var_id`
pub fn var_scope(&self, var_id: hir::ItemLocalId) -> Scope {
self.var_map
.get(&var_id)
.cloned()
.unwrap_or_else(|| bug!("no enclosing scope for id {:?}", var_id))
}
/// Returns the scope when the temp created by `expr_id` will be cleaned up.
pub fn temporary_scope(&self, expr_id: hir::ItemLocalId) -> Option<Scope> {
// Check for a designated rvalue scope.
if let Some(&s) = self.rvalue_scopes.get(&expr_id) {
debug!("temporary_scope({:?}) = {:?} [custom]", expr_id, s);
return s;
}
// Otherwise, locate the innermost terminating scope
// if there's one. Static items, for instance, won't
// have an enclosing scope, hence no scope will be
// returned.
let mut id = Scope { id: expr_id, data: ScopeData::Node };
while let Some(&(p, _)) = self.parent_map.get(&id) {
match p.data {
ScopeData::Destruction => {
debug!("temporary_scope({:?}) = {:?} [enclosing]", expr_id, id);
return Some(id);
}
_ => id = p,
}
}
debug!("temporary_scope({:?}) = None", expr_id);
return None;
}
/// Returns the lifetime of the variable `id`.
pub fn var_region(&self, id: hir::ItemLocalId) -> ty::RegionKind {
let scope = ty::ReScope(self.var_scope(id));
debug!("var_region({:?}) = {:?}", id, scope);
scope
}
pub fn scopes_intersect(&self, scope1: Scope, scope2: Scope) -> bool {
self.is_subscope_of(scope1, scope2) || self.is_subscope_of(scope2, scope1)
}
/// Returns `true` if `subscope` is equal to or is lexically nested inside `superscope`, and
/// `false` otherwise.
pub fn is_subscope_of(&self, subscope: Scope, superscope: Scope) -> bool {
let mut s = subscope;
debug!("is_subscope_of({:?}, {:?})", subscope, superscope);
while superscope != s {
match self.opt_encl_scope(s) {
None => {
debug!("is_subscope_of({:?}, {:?}, s={:?})=false", subscope, superscope, s);
return false;
}
Some(scope) => s = scope,
}
}
debug!("is_subscope_of({:?}, {:?})=true", subscope, superscope);
return true;
}
/// Returns the ID of the innermost containing body.
pub fn containing_body(&self, mut scope: Scope) -> Option<hir::ItemLocalId> {
loop {
if let ScopeData::CallSite = scope.data {
return Some(scope.item_local_id());
}
scope = self.opt_encl_scope(scope)?;
}
}
/// Finds the nearest common ancestor of two scopes. That is, finds the
/// smallest scope which is greater than or equal to both `scope_a` and
/// `scope_b`.
pub fn nearest_common_ancestor(&self, scope_a: Scope, scope_b: Scope) -> Scope {
if scope_a == scope_b {
return scope_a;
}
let mut a = scope_a;
let mut b = scope_b;
// Get the depth of each scope's parent. If either scope has no parent,
// it must be the root, which means we can stop immediately because the
// root must be the nearest common ancestor. (In practice, this is
// moderately common.)
let (parent_a, parent_a_depth) = match self.parent_map.get(&a) {
Some(pd) => *pd,
None => return a,
};
let (parent_b, parent_b_depth) = match self.parent_map.get(&b) {
Some(pd) => *pd,
None => return b,
};
if parent_a_depth > parent_b_depth {
// `a` is lower than `b`. Move `a` up until it's at the same depth
// as `b`. The first move up is trivial because we already found
// `parent_a` above; the loop does the remaining N-1 moves.
a = parent_a;
for _ in 0..(parent_a_depth - parent_b_depth - 1) {
a = self.parent_map.get(&a).unwrap().0;
}
} else if parent_b_depth > parent_a_depth {
// `b` is lower than `a`.
b = parent_b;
for _ in 0..(parent_b_depth - parent_a_depth - 1) {
b = self.parent_map.get(&b).unwrap().0;
}
} else {
// Both scopes are at the same depth, and we know they're not equal
// because that case was tested for at the top of this function. So
// we can trivially move them both up one level now.
assert!(parent_a_depth != 0);
a = parent_a;
b = parent_b;
}
// Now both scopes are at the same level. We move upwards in lockstep
// until they match. In practice, this loop is almost always executed
// zero times because `a` is almost always a direct ancestor of `b` or
// vice versa.
while a != b {
a = self.parent_map.get(&a).unwrap().0;
b = self.parent_map.get(&b).unwrap().0;
}
a
}
/// Assuming that the provided region was defined within this `ScopeTree`,
/// returns the outermost `Scope` that the region outlives.
pub fn early_free_scope(&self, tcx: TyCtxt<'tcx>, br: &ty::EarlyBoundRegion) -> Scope {
let param_owner = tcx.parent(br.def_id).unwrap();
let param_owner_id = tcx.hir().as_local_hir_id(param_owner).unwrap();
let scope = tcx
.hir()
.maybe_body_owned_by(param_owner_id)
.map(|body_id| tcx.hir().body(body_id).value.hir_id.local_id)
.unwrap_or_else(|| {
// The lifetime was defined on node that doesn't own a body,
// which in practice can only mean a trait or an impl, that
// is the parent of a method, and that is enforced below.
if Some(param_owner_id) != self.root_parent {
tcx.sess.delay_span_bug(
DUMMY_SP,
&format!(
"free_scope: {:?} not recognized by the \
region scope tree for {:?} / {:?}",
param_owner,
self.root_parent.map(|id| tcx.hir().local_def_id(id)),
self.root_body.map(|hir_id| DefId::local(hir_id.owner))
),
);
}
// The trait/impl lifetime is in scope for the method's body.
self.root_body.unwrap().local_id
});
Scope { id: scope, data: ScopeData::CallSite }
}
/// Assuming that the provided region was defined within this `ScopeTree`,
/// returns the outermost `Scope` that the region outlives.
pub fn free_scope(&self, tcx: TyCtxt<'tcx>, fr: &ty::FreeRegion) -> Scope {
let param_owner = match fr.bound_region {
ty::BoundRegion::BrNamed(def_id, _) => tcx.parent(def_id).unwrap(),
_ => fr.scope,
};
// Ensure that the named late-bound lifetimes were defined
// on the same function that they ended up being freed in.
assert_eq!(param_owner, fr.scope);
let param_owner_id = tcx.hir().as_local_hir_id(param_owner).unwrap();
let body_id = tcx.hir().body_owned_by(param_owner_id);
Scope { id: tcx.hir().body(body_id).value.hir_id.local_id, data: ScopeData::CallSite }
}
/// Checks whether the given scope contains a `yield`. If so,
/// returns `Some((span, expr_count))` with the span of a yield we found and
/// the number of expressions and patterns appearing before the `yield` in the body + 1.
/// If there a are multiple yields in a scope, the one with the highest number is returned.
pub fn yield_in_scope(&self, scope: Scope) -> Option<YieldData> {
self.yield_in_scope.get(&scope).cloned()
}
/// Checks whether the given scope contains a `yield` and if that yield could execute
/// after `expr`. If so, it returns the span of that `yield`.
/// `scope` must be inside the body.
pub fn yield_in_scope_for_expr(
&self,
scope: Scope,
expr_hir_id: hir::HirId,
body: &'tcx hir::Body<'tcx>,
) -> Option<Span> {
self.yield_in_scope(scope).and_then(|YieldData { span, expr_and_pat_count, .. }| {
let mut visitor =
ExprLocatorVisitor { hir_id: expr_hir_id, result: None, expr_and_pat_count: 0 };
visitor.visit_body(body);
if expr_and_pat_count >= visitor.result.unwrap() { Some(span) } else { None }
})
}
/// Gives the number of expressions visited in a body.
/// Used to sanity check visit_expr call count when
/// calculating generator interiors.
pub fn body_expr_count(&self, body_id: hir::BodyId) -> Option<usize> {
self.body_expr_count.get(&body_id).map(|r| *r)
}
}
/// Records the lifetime of a local variable as `cx.var_parent`
fn record_var_lifetime(
visitor: &mut RegionResolutionVisitor<'_>,
@ -1505,32 +827,3 @@ fn region_scope_tree(tcx: TyCtxt<'_>, def_id: DefId) -> &ScopeTree {
pub fn provide(providers: &mut Providers<'_>) {
*providers = Providers { region_scope_tree, ..*providers };
}
impl<'a> HashStable<StableHashingContext<'a>> for ScopeTree {
fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
let ScopeTree {
root_body,
root_parent,
ref body_expr_count,
ref parent_map,
ref var_map,
ref destruction_scopes,
ref rvalue_scopes,
ref closure_tree,
ref yield_in_scope,
} = *self;
hcx.with_node_id_hashing_mode(NodeIdHashingMode::HashDefPath, |hcx| {
root_body.hash_stable(hcx, hasher);
root_parent.hash_stable(hcx, hasher);
});
body_expr_count.hash_stable(hcx, hasher);
parent_map.hash_stable(hcx, hasher);
var_map.hash_stable(hcx, hasher);
destruction_scopes.hash_stable(hcx, hasher);
rvalue_scopes.hash_stable(hcx, hasher);
closure_tree.hash_stable(hcx, hasher);
yield_in_scope.hash_stable(hcx, hasher);
}
}