438 lines
17 KiB
Rust
438 lines
17 KiB
Rust
// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// Finds items that are externally reachable, to determine which items
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// need to have their metadata (and possibly their AST) serialized.
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// All items that can be referred to through an exported name are
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// reachable, and when a reachable thing is inline or generic, it
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// makes all other generics or inline functions that it references
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// reachable as well.
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use hir::CodegenFnAttrs;
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use hir::map as hir_map;
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use hir::def::Def;
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use hir::def_id::{DefId, CrateNum};
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use rustc_data_structures::sync::Lrc;
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use ty::{self, TyCtxt};
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use ty::maps::Providers;
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use middle::privacy;
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use session::config;
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use util::nodemap::{NodeSet, FxHashSet};
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use rustc_target::spec::abi::Abi;
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use syntax::ast;
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use syntax::attr;
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use hir;
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use hir::def_id::LOCAL_CRATE;
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use hir::intravisit::{Visitor, NestedVisitorMap};
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use hir::itemlikevisit::ItemLikeVisitor;
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use hir::intravisit;
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// Returns true if the given set of generics implies that the item it's
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// associated with must be inlined.
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fn generics_require_inlining(generics: &hir::Generics) -> bool {
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generics.params.iter().any(|param| param.is_type_param())
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}
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// Returns true if the given item must be inlined because it may be
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// monomorphized or it was marked with `#[inline]`. This will only return
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// true for functions.
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fn item_might_be_inlined(item: &hir::Item, attrs: CodegenFnAttrs) -> bool {
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if attrs.requests_inline() {
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return true
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}
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match item.node {
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hir::ItemImpl(_, _, _, ref generics, ..) |
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hir::ItemFn(.., ref generics, _) => {
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generics_require_inlining(generics)
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}
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_ => false,
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}
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}
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fn method_might_be_inlined<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
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impl_item: &hir::ImplItem,
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impl_src: DefId) -> bool {
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let codegen_fn_attrs = tcx.codegen_fn_attrs(impl_item.hir_id.owner_def_id());
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if codegen_fn_attrs.requests_inline() ||
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generics_require_inlining(&impl_item.generics) {
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return true
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}
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if let Some(impl_node_id) = tcx.hir.as_local_node_id(impl_src) {
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match tcx.hir.find(impl_node_id) {
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Some(hir_map::NodeItem(item)) =>
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item_might_be_inlined(&item, codegen_fn_attrs),
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Some(..) | None =>
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span_bug!(impl_item.span, "impl did is not an item")
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}
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} else {
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span_bug!(impl_item.span, "found a foreign impl as a parent of a local method")
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}
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}
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// Information needed while computing reachability.
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struct ReachableContext<'a, 'tcx: 'a> {
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// The type context.
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tcx: TyCtxt<'a, 'tcx, 'tcx>,
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tables: &'a ty::TypeckTables<'tcx>,
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// The set of items which must be exported in the linkage sense.
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reachable_symbols: NodeSet,
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// A worklist of item IDs. Each item ID in this worklist will be inlined
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// and will be scanned for further references.
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worklist: Vec<ast::NodeId>,
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// Whether any output of this compilation is a library
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any_library: bool,
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}
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impl<'a, 'tcx> Visitor<'tcx> for ReachableContext<'a, 'tcx> {
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fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
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NestedVisitorMap::None
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}
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fn visit_nested_body(&mut self, body: hir::BodyId) {
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let old_tables = self.tables;
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self.tables = self.tcx.body_tables(body);
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let body = self.tcx.hir.body(body);
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self.visit_body(body);
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self.tables = old_tables;
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}
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fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
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let def = match expr.node {
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hir::ExprPath(ref qpath) => {
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Some(self.tables.qpath_def(qpath, expr.hir_id))
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}
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hir::ExprMethodCall(..) => {
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Some(self.tables.type_dependent_defs()[expr.hir_id])
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}
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_ => None
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};
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match def {
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Some(Def::Local(node_id)) | Some(Def::Upvar(node_id, ..)) => {
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self.reachable_symbols.insert(node_id);
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}
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Some(def) => {
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let def_id = def.def_id();
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if let Some(node_id) = self.tcx.hir.as_local_node_id(def_id) {
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if self.def_id_represents_local_inlined_item(def_id) {
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self.worklist.push(node_id);
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} else {
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match def {
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// If this path leads to a constant, then we need to
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// recurse into the constant to continue finding
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// items that are reachable.
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Def::Const(..) | Def::AssociatedConst(..) => {
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self.worklist.push(node_id);
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}
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// If this wasn't a static, then the destination is
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// surely reachable.
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_ => {
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self.reachable_symbols.insert(node_id);
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}
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}
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}
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}
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}
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_ => {}
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}
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intravisit::walk_expr(self, expr)
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}
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}
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impl<'a, 'tcx> ReachableContext<'a, 'tcx> {
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// Returns true if the given def ID represents a local item that is
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// eligible for inlining and false otherwise.
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fn def_id_represents_local_inlined_item(&self, def_id: DefId) -> bool {
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let node_id = match self.tcx.hir.as_local_node_id(def_id) {
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Some(node_id) => node_id,
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None => { return false; }
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};
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match self.tcx.hir.find(node_id) {
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Some(hir_map::NodeItem(item)) => {
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match item.node {
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hir::ItemFn(..) =>
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item_might_be_inlined(&item, self.tcx.codegen_fn_attrs(def_id)),
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_ => false,
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}
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}
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Some(hir_map::NodeTraitItem(trait_method)) => {
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match trait_method.node {
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hir::TraitItemKind::Const(_, ref default) => default.is_some(),
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hir::TraitItemKind::Method(_, hir::TraitMethod::Provided(_)) => true,
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hir::TraitItemKind::Method(_, hir::TraitMethod::Required(_)) |
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hir::TraitItemKind::Type(..) => false,
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}
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}
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Some(hir_map::NodeImplItem(impl_item)) => {
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match impl_item.node {
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hir::ImplItemKind::Const(..) => true,
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hir::ImplItemKind::Method(..) => {
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let attrs = self.tcx.codegen_fn_attrs(def_id);
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if generics_require_inlining(&impl_item.generics) ||
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attrs.requests_inline() {
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true
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} else {
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let impl_did = self.tcx
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.hir
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.get_parent_did(node_id);
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// Check the impl. If the generics on the self
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// type of the impl require inlining, this method
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// does too.
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let impl_node_id = self.tcx.hir.as_local_node_id(impl_did).unwrap();
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match self.tcx.hir.expect_item(impl_node_id).node {
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hir::ItemImpl(_, _, _, ref generics, ..) => {
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generics_require_inlining(generics)
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}
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_ => false
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}
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}
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}
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hir::ImplItemKind::Type(_) => false,
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}
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}
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Some(_) => false,
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None => false // This will happen for default methods.
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}
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}
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// Step 2: Mark all symbols that the symbols on the worklist touch.
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fn propagate(&mut self) {
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let mut scanned = FxHashSet();
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while let Some(search_item) = self.worklist.pop() {
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if !scanned.insert(search_item) {
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continue
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}
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if let Some(ref item) = self.tcx.hir.find(search_item) {
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self.propagate_node(item, search_item);
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}
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}
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}
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fn propagate_node(&mut self, node: &hir_map::Node<'tcx>,
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search_item: ast::NodeId) {
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if !self.any_library {
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// If we are building an executable, only explicitly extern
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// types need to be exported.
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if let hir_map::NodeItem(item) = *node {
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let reachable = if let hir::ItemFn(.., abi, _, _) = item.node {
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abi != Abi::Rust
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} else {
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false
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};
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let def_id = self.tcx.hir.local_def_id(item.id);
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let is_extern = self.tcx.codegen_fn_attrs(def_id).contains_extern_indicator();
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if reachable || is_extern {
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self.reachable_symbols.insert(search_item);
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}
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}
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} else {
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// If we are building a library, then reachable symbols will
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// continue to participate in linkage after this product is
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// produced. In this case, we traverse the ast node, recursing on
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// all reachable nodes from this one.
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self.reachable_symbols.insert(search_item);
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}
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match *node {
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hir_map::NodeItem(item) => {
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match item.node {
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hir::ItemFn(.., body) => {
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let def_id = self.tcx.hir.local_def_id(item.id);
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if item_might_be_inlined(&item, self.tcx.codegen_fn_attrs(def_id)) {
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self.visit_nested_body(body);
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}
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}
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// Reachable constants will be inlined into other crates
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// unconditionally, so we need to make sure that their
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// contents are also reachable.
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hir::ItemConst(_, init) => {
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self.visit_nested_body(init);
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}
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// These are normal, nothing reachable about these
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// inherently and their children are already in the
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// worklist, as determined by the privacy pass
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hir::ItemExternCrate(_) | hir::ItemUse(..) |
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hir::ItemTy(..) | hir::ItemStatic(..) |
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hir::ItemMod(..) | hir::ItemForeignMod(..) |
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hir::ItemImpl(..) | hir::ItemTrait(..) | hir::ItemTraitAlias(..) |
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hir::ItemStruct(..) | hir::ItemEnum(..) |
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hir::ItemUnion(..) | hir::ItemGlobalAsm(..) => {}
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}
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}
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hir_map::NodeTraitItem(trait_method) => {
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match trait_method.node {
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hir::TraitItemKind::Const(_, None) |
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hir::TraitItemKind::Method(_, hir::TraitMethod::Required(_)) => {
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// Keep going, nothing to get exported
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}
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hir::TraitItemKind::Const(_, Some(body_id)) |
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hir::TraitItemKind::Method(_, hir::TraitMethod::Provided(body_id)) => {
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self.visit_nested_body(body_id);
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}
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hir::TraitItemKind::Type(..) => {}
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}
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}
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hir_map::NodeImplItem(impl_item) => {
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match impl_item.node {
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hir::ImplItemKind::Const(_, body) => {
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self.visit_nested_body(body);
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}
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hir::ImplItemKind::Method(_, body) => {
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let did = self.tcx.hir.get_parent_did(search_item);
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if method_might_be_inlined(self.tcx, impl_item, did) {
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self.visit_nested_body(body)
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}
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}
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hir::ImplItemKind::Type(_) => {}
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}
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}
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hir_map::NodeExpr(&hir::Expr { node: hir::ExprClosure(.., body, _, _), .. }) => {
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self.visit_nested_body(body);
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}
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// Nothing to recurse on for these
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hir_map::NodeForeignItem(_) |
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hir_map::NodeVariant(_) |
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hir_map::NodeStructCtor(_) |
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hir_map::NodeField(_) |
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hir_map::NodeTy(_) |
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hir_map::NodeMacroDef(_) => {}
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_ => {
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bug!("found unexpected thingy in worklist: {}",
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self.tcx.hir.node_to_string(search_item))
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}
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}
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}
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}
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// Some methods from non-exported (completely private) trait impls still have to be
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// reachable if they are called from inlinable code. Generally, it's not known until
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// monomorphization if a specific trait impl item can be reachable or not. So, we
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// conservatively mark all of them as reachable.
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// FIXME: One possible strategy for pruning the reachable set is to avoid marking impl
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// items of non-exported traits (or maybe all local traits?) unless their respective
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// trait items are used from inlinable code through method call syntax or UFCS, or their
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// trait is a lang item.
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struct CollectPrivateImplItemsVisitor<'a, 'tcx: 'a> {
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tcx: TyCtxt<'a, 'tcx, 'tcx>,
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access_levels: &'a privacy::AccessLevels,
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worklist: &'a mut Vec<ast::NodeId>,
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}
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impl<'a, 'tcx: 'a> ItemLikeVisitor<'tcx> for CollectPrivateImplItemsVisitor<'a, 'tcx> {
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fn visit_item(&mut self, item: &hir::Item) {
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// Anything which has custom linkage gets thrown on the worklist no
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// matter where it is in the crate.
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if attr::contains_name(&item.attrs, "linkage") {
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self.worklist.push(item.id);
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}
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// We need only trait impls here, not inherent impls, and only non-exported ones
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if let hir::ItemImpl(.., Some(ref trait_ref), _, ref impl_item_refs) = item.node {
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if !self.access_levels.is_reachable(item.id) {
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for impl_item_ref in impl_item_refs {
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self.worklist.push(impl_item_ref.id.node_id);
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}
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let trait_def_id = match trait_ref.path.def {
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Def::Trait(def_id) => def_id,
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_ => unreachable!()
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};
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if !trait_def_id.is_local() {
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return
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}
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for default_method in self.tcx.provided_trait_methods(trait_def_id) {
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let node_id = self.tcx
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.hir
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.as_local_node_id(default_method.def_id)
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.unwrap();
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self.worklist.push(node_id);
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}
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}
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}
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}
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fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem) {}
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fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem) {
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// processed in visit_item above
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}
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}
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// We introduce a new-type here, so we can have a specialized HashStable
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// implementation for it.
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#[derive(Clone)]
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pub struct ReachableSet(pub Lrc<NodeSet>);
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fn reachable_set<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, crate_num: CrateNum) -> ReachableSet {
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debug_assert!(crate_num == LOCAL_CRATE);
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let access_levels = &tcx.privacy_access_levels(LOCAL_CRATE);
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let any_library = tcx.sess.crate_types.borrow().iter().any(|ty| {
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*ty == config::CrateTypeRlib || *ty == config::CrateTypeDylib ||
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*ty == config::CrateTypeProcMacro
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});
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let mut reachable_context = ReachableContext {
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tcx,
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tables: &ty::TypeckTables::empty(None),
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reachable_symbols: NodeSet(),
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worklist: Vec::new(),
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any_library,
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};
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// Step 1: Seed the worklist with all nodes which were found to be public as
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// a result of the privacy pass along with all local lang items and impl items.
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// If other crates link to us, they're going to expect to be able to
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// use the lang items, so we need to be sure to mark them as
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// exported.
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for (id, _) in &access_levels.map {
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reachable_context.worklist.push(*id);
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}
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for item in tcx.lang_items().items().iter() {
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if let Some(did) = *item {
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if let Some(node_id) = tcx.hir.as_local_node_id(did) {
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reachable_context.worklist.push(node_id);
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}
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}
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}
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{
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let mut collect_private_impl_items = CollectPrivateImplItemsVisitor {
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tcx,
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access_levels,
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worklist: &mut reachable_context.worklist,
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};
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tcx.hir.krate().visit_all_item_likes(&mut collect_private_impl_items);
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}
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// Step 2: Mark all symbols that the symbols on the worklist touch.
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reachable_context.propagate();
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// Return the set of reachable symbols.
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ReachableSet(Lrc::new(reachable_context.reachable_symbols))
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}
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pub fn provide(providers: &mut Providers) {
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*providers = Providers {
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reachable_set,
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..*providers
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};
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}
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