971 lines
33 KiB
Rust
971 lines
33 KiB
Rust
// Copyright 2012 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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/*!
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This file actually contains two passes related to regions. The first
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pass builds up the `scope_map`, which describes the parent links in
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the region hierarchy. The second pass infers which types must be
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region parameterized.
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*/
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use driver::session::Session;
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use metadata::csearch;
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use middle::resolve;
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use middle::ty::{region_variance, rv_covariant, rv_invariant};
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use middle::ty::{rv_contravariant, FreeRegion};
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use middle::ty;
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use core::hashmap::{HashMap, HashSet};
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use syntax::ast_map;
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use syntax::codemap::span;
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use syntax::print::pprust;
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use syntax::parse::token::special_idents;
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use syntax::{ast, visit};
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pub type parent = Option<ast::node_id>;
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/**
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The region maps encode information about region relationships.
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- `scope_map` maps from:
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- an expression to the expression or block encoding the maximum
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(static) lifetime of a value produced by that expression. This is
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generally the innermost call, statement, match, or block.
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- a variable or binding id to the block in which that variable is declared.
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- `free_region_map` maps from:
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- a free region `a` to a list of free regions `bs` such that
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`a <= b for all b in bs`
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- the free region map is populated during type check as we check
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each function. See the function `relate_free_regions` for
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more information.
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*/
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pub struct RegionMaps {
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priv scope_map: HashMap<ast::node_id, ast::node_id>,
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priv free_region_map: HashMap<FreeRegion, ~[FreeRegion]>,
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}
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pub struct ctxt {
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sess: Session,
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def_map: resolve::DefMap,
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// Generated maps:
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region_maps: @mut RegionMaps,
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// Generally speaking, expressions are parented to their innermost
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// enclosing block. But some kinds of expressions serve as
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// parents: calls, methods, etc. In addition, some expressions
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// serve as parents by virtue of where they appear. For example,
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// the condition in a while loop is always a parent. In those
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// cases, we add the node id of such an expression to this set so
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// that when we visit it we can view it as a parent.
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root_exprs: @mut HashSet<ast::node_id>,
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// The parent scope is the innermost block, statement, call, or match
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// expression during the execution of which the current expression
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// will be evaluated. Generally speaking, the innermost parent
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// scope is also the closest suitable ancestor in the AST tree.
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//
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// There is a subtle point concerning call arguments. Imagine
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// you have a call:
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//
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// { // block a
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// foo( // call b
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// x,
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// y);
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// }
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//
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// In what lifetime are the expressions `x` and `y` evaluated? At
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// first, I imagine the answer was the block `a`, as the arguments
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// are evaluated before the call takes place. But this turns out
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// to be wrong. The lifetime of the call must encompass the
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// argument evaluation as well.
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//
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// The reason is that evaluation of an earlier argument could
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// create a borrow which exists during the evaluation of later
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// arguments. Consider this torture test, for example,
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//
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// fn test1(x: @mut ~int) {
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// foo(&**x, *x = ~5);
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// }
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//
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// Here, the first argument `&**x` will be a borrow of the `~int`,
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// but the second argument overwrites that very value! Bad.
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// (This test is borrowck-pure-scope-in-call.rs, btw)
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parent: parent,
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}
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pub impl RegionMaps {
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fn relate_free_regions(&mut self,
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sub: FreeRegion,
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sup: FreeRegion)
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{
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match self.free_region_map.find_mut(&sub) {
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Some(sups) => {
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if !sups.contains(&sup) {
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sups.push(sup);
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}
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return;
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}
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None => {}
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}
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debug!("relate_free_regions(sub=%?, sup=%?)", sub, sup);
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self.free_region_map.insert(sub, ~[sup]);
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}
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fn record_parent(&mut self,
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sub: ast::node_id,
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sup: ast::node_id)
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{
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debug!("record_parent(sub=%?, sup=%?)", sub, sup);
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self.scope_map.insert(sub, sup);
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}
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fn opt_encl_scope(&self,
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id: ast::node_id) -> Option<ast::node_id>
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{
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//! Returns the narrowest scope that encloses `id`, if any.
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self.scope_map.find(&id).map(|&x| *x)
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}
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fn encl_scope(&self,
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id: ast::node_id) -> ast::node_id
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{
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//! Returns the narrowest scope that encloses `id`, if any.
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match self.scope_map.find(&id) {
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Some(&r) => r,
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None => { fail!(fmt!("No enclosing scope for id %?", id)); }
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}
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}
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fn encl_region(&self,
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id: ast::node_id) -> ty::Region
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{
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//! Returns the narrowest scope region that encloses `id`, if any.
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ty::re_scope(self.encl_scope(id))
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}
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fn is_sub_scope(&self,
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sub_scope: ast::node_id,
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superscope: ast::node_id) -> bool
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{
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/*!
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* Returns true if `sub_scope` is equal to or is lexically
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* nested inside `superscope` and false otherwise.
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*/
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let mut sub_scope = sub_scope;
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while superscope != sub_scope {
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match self.scope_map.find(&sub_scope) {
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None => return false,
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Some(&scope) => sub_scope = scope
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}
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}
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return true;
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}
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fn sub_free_region(&self,
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sub: FreeRegion,
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sup: FreeRegion) -> bool
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{
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/*!
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* Determines whether two free regions have a subregion relationship
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* by walking the graph encoded in `free_region_map`. Note that
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* it is possible that `sub != sup` and `sub <= sup` and `sup <= sub`
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* (that is, the user can give two different names to the same lifetime).
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*/
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if sub == sup {
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return true;
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}
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// Do a little breadth-first-search here. The `queue` list
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// doubles as a way to detect if we've seen a particular FR
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// before. Note that we expect this graph to be an *extremely
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// shallow* tree.
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let mut queue = ~[sub];
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let mut i = 0;
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while i < queue.len() {
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match self.free_region_map.find(&queue[i]) {
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Some(parents) => {
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for parents.each |parent| {
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if *parent == sup {
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return true;
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}
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if !queue.contains(parent) {
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queue.push(*parent);
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}
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}
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}
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None => {}
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}
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i += 1;
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}
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return false;
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}
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fn is_subregion_of(&self,
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sub_region: ty::Region,
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super_region: ty::Region) -> bool
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{
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/*!
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* Determines whether one region is a subregion of another. This is
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* intended to run *after inference* and sadly the logic is somewhat
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* duplicated with the code in infer.rs.
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*/
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debug!("is_subregion_of(sub_region=%?, super_region=%?)",
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sub_region, super_region);
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sub_region == super_region || {
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match (sub_region, super_region) {
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(_, ty::re_static) => {
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true
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}
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(ty::re_scope(sub_scope), ty::re_scope(super_scope)) => {
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self.is_sub_scope(sub_scope, super_scope)
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}
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(ty::re_scope(sub_scope), ty::re_free(ref fr)) => {
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self.is_sub_scope(sub_scope, fr.scope_id)
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}
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(ty::re_free(sub_fr), ty::re_free(super_fr)) => {
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self.sub_free_region(sub_fr, super_fr)
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}
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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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}
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fn nearest_common_ancestor(&self,
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scope_a: ast::node_id,
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scope_b: ast::node_id) -> Option<ast::node_id>
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{
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/*!
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* Finds the nearest common ancestor (if any) of two scopes. That
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* is, finds the smallest scope which is greater than or equal to
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* both `scope_a` and `scope_b`.
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*/
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if scope_a == scope_b { return Some(scope_a); }
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let a_ancestors = ancestors_of(self, scope_a);
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let b_ancestors = ancestors_of(self, scope_b);
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let mut a_index = vec::len(a_ancestors) - 1u;
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let mut b_index = vec::len(b_ancestors) - 1u;
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// Here, ~[ab]_ancestors is a vector going from narrow to broad.
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// The end of each vector will be the item where the scope is
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// defined; if there are any common ancestors, then the tails of
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// the vector will be the same. So basically we want to walk
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// backwards from the tail of each vector and find the first point
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// where they diverge. If one vector is a suffix of the other,
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// then the corresponding scope is a superscope of the other.
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if a_ancestors[a_index] != b_ancestors[b_index] {
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return None;
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}
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loop {
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// Loop invariant: a_ancestors[a_index] == b_ancestors[b_index]
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// for all indices between a_index and the end of the array
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if a_index == 0u { return Some(scope_a); }
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if b_index == 0u { return Some(scope_b); }
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a_index -= 1u;
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b_index -= 1u;
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if a_ancestors[a_index] != b_ancestors[b_index] {
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return Some(a_ancestors[a_index + 1u]);
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}
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}
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fn ancestors_of(self: &RegionMaps, scope: ast::node_id)
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-> ~[ast::node_id]
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{
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let mut result = ~[scope];
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let mut scope = scope;
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loop {
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match self.scope_map.find(&scope) {
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None => return result,
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Some(&superscope) => {
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result.push(superscope);
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scope = superscope;
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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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/// Extracts that current parent from cx, failing if there is none.
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pub fn parent_id(cx: ctxt, span: span) -> ast::node_id {
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match cx.parent {
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None => {
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cx.sess.span_bug(span, "crate should not be parent here");
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}
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Some(parent_id) => {
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parent_id
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}
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}
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}
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/// Records the current parent (if any) as the parent of `child_id`.
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pub fn record_parent(cx: ctxt, child_id: ast::node_id) {
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for cx.parent.each |parent_id| {
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cx.region_maps.record_parent(child_id, *parent_id);
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}
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}
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pub fn resolve_block(blk: &ast::blk, cx: ctxt, visitor: visit::vt<ctxt>) {
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// Record the parent of this block.
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record_parent(cx, blk.node.id);
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// Descend.
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let new_cx: ctxt = ctxt {parent: Some(blk.node.id),.. cx};
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visit::visit_block(blk, new_cx, visitor);
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}
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pub fn resolve_arm(arm: &ast::arm, cx: ctxt, visitor: visit::vt<ctxt>) {
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visit::visit_arm(arm, cx, visitor);
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}
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pub fn resolve_pat(pat: @ast::pat, cx: ctxt, visitor: visit::vt<ctxt>) {
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match pat.node {
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ast::pat_ident(*) => {
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let defn_opt = cx.def_map.find(&pat.id);
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match defn_opt {
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Some(&ast::def_variant(_,_)) => {
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/* Nothing to do; this names a variant. */
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}
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_ => {
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/* This names a local. Bind it to the containing scope. */
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record_parent(cx, pat.id);
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}
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}
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}
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_ => { /* no-op */ }
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}
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visit::visit_pat(pat, cx, visitor);
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}
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pub fn resolve_stmt(stmt: @ast::stmt, cx: ctxt, visitor: visit::vt<ctxt>) {
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match stmt.node {
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ast::stmt_decl(*) => {
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visit::visit_stmt(stmt, cx, visitor);
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}
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// This code has to be kept consistent with trans::base::trans_stmt
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ast::stmt_expr(_, stmt_id) |
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ast::stmt_semi(_, stmt_id) => {
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record_parent(cx, stmt_id);
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let mut expr_cx = cx;
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expr_cx.parent = Some(stmt_id);
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visit::visit_stmt(stmt, expr_cx, visitor);
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}
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ast::stmt_mac(*) => cx.sess.bug(~"unexpanded macro")
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}
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}
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pub fn resolve_expr(expr: @ast::expr, cx: ctxt, visitor: visit::vt<ctxt>) {
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record_parent(cx, expr.id);
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let mut new_cx = cx;
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match expr.node {
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// Calls or overloadable operators
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// FIXME #3387
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// ast::expr_index(*) | ast::expr_binary(*) |
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// ast::expr_unary(*) |
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ast::expr_call(*) | ast::expr_method_call(*) => {
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debug!("node %d: %s", expr.id, pprust::expr_to_str(expr,
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cx.sess.intr()));
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new_cx.parent = Some(expr.id);
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}
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ast::expr_match(*) => {
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debug!("node %d: %s", expr.id, pprust::expr_to_str(expr,
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cx.sess.intr()));
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new_cx.parent = Some(expr.id);
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}
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ast::expr_while(cond, _) => {
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new_cx.root_exprs.insert(cond.id);
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}
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_ => {}
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};
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if new_cx.root_exprs.contains(&expr.id) {
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new_cx.parent = Some(expr.id);
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}
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visit::visit_expr(expr, new_cx, visitor);
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}
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pub fn resolve_local(local: @ast::local,
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cx: ctxt,
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visitor: visit::vt<ctxt>) {
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record_parent(cx, local.node.id);
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visit::visit_local(local, cx, visitor);
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}
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pub fn resolve_item(item: @ast::item, cx: ctxt, visitor: visit::vt<ctxt>) {
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// Items create a new outer block scope as far as we're concerned.
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let new_cx: ctxt = ctxt {parent: None,.. cx};
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visit::visit_item(item, new_cx, visitor);
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}
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pub fn resolve_fn(fk: &visit::fn_kind,
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decl: &ast::fn_decl,
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body: &ast::blk,
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sp: span,
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id: ast::node_id,
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cx: ctxt,
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visitor: visit::vt<ctxt>) {
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let fn_cx = match *fk {
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visit::fk_item_fn(*) | visit::fk_method(*) => {
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// Top-level functions are a root scope.
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ctxt {parent: Some(id),.. cx}
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}
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visit::fk_anon(*) | visit::fk_fn_block(*) => {
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// Closures continue with the inherited scope.
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cx
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}
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};
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// Record the ID of `self`.
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match *fk {
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visit::fk_method(_, _, method) => {
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cx.region_maps.record_parent(method.self_id, body.node.id);
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}
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_ => {}
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}
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debug!("visiting fn with body %d. cx.parent: %? \
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fn_cx.parent: %?",
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body.node.id, cx.parent, fn_cx.parent);
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for decl.inputs.each |input| {
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cx.region_maps.record_parent(input.id, body.node.id);
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}
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visit::visit_fn(fk, decl, body, sp, id, fn_cx, visitor);
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}
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pub fn resolve_crate(sess: Session,
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def_map: resolve::DefMap,
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crate: @ast::crate) -> @mut RegionMaps
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{
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let region_maps = @mut RegionMaps {
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scope_map: HashMap::new(),
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free_region_map: HashMap::new()
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};
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let cx: ctxt = ctxt {sess: sess,
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def_map: def_map,
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region_maps: region_maps,
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root_exprs: @mut HashSet::new(),
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parent: None};
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let visitor = visit::mk_vt(@visit::Visitor {
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visit_block: resolve_block,
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visit_item: resolve_item,
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visit_fn: resolve_fn,
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visit_arm: resolve_arm,
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visit_pat: resolve_pat,
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visit_stmt: resolve_stmt,
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visit_expr: resolve_expr,
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visit_local: resolve_local,
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.. *visit::default_visitor()
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});
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visit::visit_crate(crate, cx, visitor);
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return region_maps;
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}
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|
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// ___________________________________________________________________________
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// Determining region parameterization
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//
|
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// Infers which type defns must be region parameterized---this is done
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// by scanning their contents to see whether they reference a region
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// type, directly or indirectly. This is a fixed-point computation.
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//
|
|
// We do it in two passes. First we walk the AST and construct a map
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|
// from each type defn T1 to other defns which make use of it. For example,
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// if we have a type like:
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//
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// type S = *int;
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// type T = S;
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//
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// Then there would be a map entry from S to T. During the same walk,
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// we also construct add any types that reference regions to a set and
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// a worklist. We can then process the worklist, propagating indirect
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// dependencies until a fixed point is reached.
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pub type region_paramd_items = @mut HashMap<ast::node_id, region_variance>;
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#[deriving(Eq)]
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pub struct region_dep {
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ambient_variance: region_variance,
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id: ast::node_id
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}
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pub type dep_map = @mut HashMap<ast::node_id, @mut ~[region_dep]>;
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pub struct DetermineRpCtxt {
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sess: Session,
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ast_map: ast_map::map,
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def_map: resolve::DefMap,
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region_paramd_items: region_paramd_items,
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dep_map: dep_map,
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worklist: ~[ast::node_id],
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// the innermost enclosing item id
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item_id: ast::node_id,
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// true when we are within an item but not within a method.
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// see long discussion on region_is_relevant().
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anon_implies_rp: bool,
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// encodes the context of the current type; invariant if
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// mutable, covariant otherwise
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ambient_variance: region_variance,
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}
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pub fn join_variance(variance1: region_variance,
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variance2: region_variance)
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-> region_variance {
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match (variance1, variance2) {
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(rv_invariant, _) => {rv_invariant}
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(_, rv_invariant) => {rv_invariant}
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(rv_covariant, rv_contravariant) => {rv_invariant}
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(rv_contravariant, rv_covariant) => {rv_invariant}
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(rv_covariant, rv_covariant) => {rv_covariant}
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(rv_contravariant, rv_contravariant) => {rv_contravariant}
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}
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}
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/// Combines the ambient variance with the variance of a
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/// particular site to yield the final variance of the reference.
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///
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/// Example: if we are checking function arguments then the ambient
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/// variance is contravariant. If we then find a `&'r T` pointer, `r`
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/// appears in a co-variant position. This implies that this
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/// occurrence of `r` is contra-variant with respect to the current
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/// item, and hence the function returns `rv_contravariant`.
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pub fn add_variance(ambient_variance: region_variance,
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variance: region_variance)
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-> region_variance {
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match (ambient_variance, variance) {
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(rv_invariant, _) => rv_invariant,
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(_, rv_invariant) => rv_invariant,
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(rv_covariant, c) => c,
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(c, rv_covariant) => c,
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(rv_contravariant, rv_contravariant) => rv_covariant
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}
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}
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pub impl DetermineRpCtxt {
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fn add_variance(&self, variance: region_variance) -> region_variance {
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add_variance(self.ambient_variance, variance)
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}
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/// Records that item `id` is region-parameterized with the
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/// variance `variance`. If `id` was already parameterized, then
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/// the new variance is joined with the old variance.
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fn add_rp(&mut self, id: ast::node_id, variance: region_variance) {
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assert!(id != 0);
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let old_variance = self.region_paramd_items.find(&id).
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map_consume(|x| *x);
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let joined_variance = match old_variance {
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None => variance,
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Some(v) => join_variance(v, variance)
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};
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debug!("add_rp() variance for %s: %? == %? ^ %?",
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ast_map::node_id_to_str(self.ast_map, id,
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self.sess.parse_sess.interner),
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joined_variance, old_variance, variance);
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if Some(joined_variance) != old_variance {
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let region_paramd_items = self.region_paramd_items;
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region_paramd_items.insert(id, joined_variance);
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self.worklist.push(id);
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}
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}
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/// Indicates that the region-parameterization of the current item
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/// is dependent on the region-parameterization of the item
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/// `from`. Put another way, it indicates that the current item
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/// contains a value of type `from`, so if `from` is
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/// region-parameterized, so is the current item.
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fn add_dep(&mut self, from: ast::node_id) {
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debug!("add dependency from %d -> %d (%s -> %s) with variance %?",
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from, self.item_id,
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ast_map::node_id_to_str(self.ast_map, from,
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self.sess.parse_sess.interner),
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ast_map::node_id_to_str(self.ast_map, self.item_id,
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self.sess.parse_sess.interner),
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copy self.ambient_variance);
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let vec = match self.dep_map.find(&from) {
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Some(&vec) => vec,
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None => {
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let vec = @mut ~[];
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let dep_map = self.dep_map;
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dep_map.insert(from, vec);
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vec
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}
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};
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let dep = region_dep {
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ambient_variance: self.ambient_variance,
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id: self.item_id
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};
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if !vec.contains(&dep) { vec.push(dep); }
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}
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// Determines whether a reference to a region that appears in the
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// AST implies that the enclosing type is region-parameterized (RP).
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// This point is subtle. Here are some examples to make it more
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// concrete.
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//
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// 1. impl foo for &int { ... }
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// 2. impl foo for &'self int { ... }
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// 3. impl foo for bar { fn m(@self) -> &'self int { ... } }
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// 4. impl foo for bar { fn m(&self) -> &'self int { ... } }
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// 5. impl foo for bar { fn m(&self) -> &int { ... } }
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//
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// In case 1, the anonymous region is being referenced,
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// but it appears in a context where the anonymous region
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// resolves to self, so the impl foo is RP.
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//
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// In case 2, the self parameter is written explicitly.
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//
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// In case 3, the method refers to the region `self`, so that
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// implies that the impl must be region parameterized. (If the
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// type bar is not region parameterized, that is an error, because
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// the self region is effectively unconstrained, but that is
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// detected elsewhere).
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//
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// In case 4, the method refers to the region `self`, but the
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// `self` region is bound by the `&self` receiver, and so this
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// does not require that `bar` be RP.
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//
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// In case 5, the anonymous region is referenced, but it
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// bound by the method, so it does not refer to self. This impl
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// need not be region parameterized.
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//
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// Normally, & or &self implies that the enclosing item is RP.
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// However, within a function, & is always bound. Within a method
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// with &self type, &self is also bound. We detect those last two
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// cases via flags (anon_implies_rp and self_implies_rp) that are
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// true when the anon or self region implies RP.
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fn region_is_relevant(&self, r: Option<@ast::Lifetime>) -> bool {
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match r {
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None => {
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self.anon_implies_rp
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}
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Some(ref l) if l.ident == special_idents::static => {
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false
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}
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Some(ref l) if l.ident == special_idents::self_ => {
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true
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}
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Some(_) => {
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false
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}
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}
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}
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fn with(@mut self,
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item_id: ast::node_id,
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anon_implies_rp: bool,
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f: &fn()) {
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let old_item_id = self.item_id;
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let old_anon_implies_rp = self.anon_implies_rp;
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self.item_id = item_id;
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self.anon_implies_rp = anon_implies_rp;
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debug!("with_item_id(%d, %b)",
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item_id,
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anon_implies_rp);
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let _i = ::util::common::indenter();
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f();
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self.item_id = old_item_id;
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self.anon_implies_rp = old_anon_implies_rp;
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}
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fn with_ambient_variance(@mut self, variance: region_variance, f: &fn()) {
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let old_ambient_variance = self.ambient_variance;
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self.ambient_variance = self.add_variance(variance);
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f();
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self.ambient_variance = old_ambient_variance;
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}
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}
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pub fn determine_rp_in_item(item: @ast::item,
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cx: @mut DetermineRpCtxt,
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visitor: visit::vt<@mut DetermineRpCtxt>) {
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do cx.with(item.id, true) {
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visit::visit_item(item, cx, visitor);
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}
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}
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pub fn determine_rp_in_fn(fk: &visit::fn_kind,
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decl: &ast::fn_decl,
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body: &ast::blk,
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_: span,
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_: ast::node_id,
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cx: @mut DetermineRpCtxt,
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visitor: visit::vt<@mut DetermineRpCtxt>) {
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do cx.with(cx.item_id, false) {
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do cx.with_ambient_variance(rv_contravariant) {
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for decl.inputs.each |a| {
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(visitor.visit_ty)(a.ty, cx, visitor);
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}
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}
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(visitor.visit_ty)(decl.output, cx, visitor);
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let generics = visit::generics_of_fn(fk);
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(visitor.visit_generics)(&generics, cx, visitor);
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(visitor.visit_block)(body, cx, visitor);
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}
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}
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pub fn determine_rp_in_ty_method(ty_m: &ast::ty_method,
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cx: @mut DetermineRpCtxt,
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visitor: visit::vt<@mut DetermineRpCtxt>) {
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do cx.with(cx.item_id, false) {
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visit::visit_ty_method(ty_m, cx, visitor);
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}
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}
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pub fn determine_rp_in_ty(ty: @ast::Ty,
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cx: @mut DetermineRpCtxt,
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visitor: visit::vt<@mut DetermineRpCtxt>) {
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// we are only interested in types that will require an item to
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// be region-parameterized. if cx.item_id is zero, then this type
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// is not a member of a type defn nor is it a constitutent of an
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// impl etc. So we can ignore it and its components.
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if cx.item_id == 0 { return; }
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// if this type directly references a region pointer like &'r ty,
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// add to the worklist/set. Note that &'r ty is contravariant with
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// respect to &r, because &'r ty can be used whereever a *smaller*
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// region is expected (and hence is a supertype of those
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// locations)
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let sess = cx.sess;
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match ty.node {
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ast::ty_rptr(r, _) => {
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debug!("referenced rptr type %s",
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pprust::ty_to_str(ty, sess.intr()));
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if cx.region_is_relevant(r) {
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cx.add_rp(cx.item_id, cx.add_variance(rv_contravariant))
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}
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}
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ast::ty_closure(ref f) => {
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debug!("referenced fn type: %s",
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pprust::ty_to_str(ty, sess.intr()));
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match f.region {
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Some(_) => {
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if cx.region_is_relevant(f.region) {
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cx.add_rp(cx.item_id,
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cx.add_variance(rv_contravariant))
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}
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}
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None => {
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if f.sigil == ast::BorrowedSigil && cx.anon_implies_rp {
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cx.add_rp(cx.item_id,
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cx.add_variance(rv_contravariant));
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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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// if this references another named type, add the dependency
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// to the dep_map. If the type is not defined in this crate,
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// then check whether it is region-parameterized and consider
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// that as a direct dependency.
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match ty.node {
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ast::ty_path(path, id) => {
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match cx.def_map.find(&id) {
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Some(&ast::def_ty(did)) |
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Some(&ast::def_trait(did)) |
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Some(&ast::def_struct(did)) => {
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if did.crate == ast::local_crate {
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if cx.region_is_relevant(path.rp) {
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cx.add_dep(did.node);
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}
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} else {
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let cstore = sess.cstore;
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match csearch::get_region_param(cstore, did) {
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None => {}
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Some(variance) => {
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debug!("reference to external, rp'd type %s",
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pprust::ty_to_str(ty, sess.intr()));
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if cx.region_is_relevant(path.rp) {
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cx.add_rp(cx.item_id, cx.add_variance(variance))
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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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}
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_ => {}
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}
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match ty.node {
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ast::ty_box(mt) | ast::ty_uniq(mt) | ast::ty_vec(mt) |
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ast::ty_rptr(_, mt) | ast::ty_ptr(mt) => {
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visit_mt(mt, cx, visitor);
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}
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ast::ty_path(path, _) => {
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// type parameters are---for now, anyway---always invariant
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do cx.with_ambient_variance(rv_invariant) {
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for path.types.each |tp| {
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(visitor.visit_ty)(*tp, cx, visitor);
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}
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}
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}
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ast::ty_closure(@ast::TyClosure {decl: ref decl, _}) |
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ast::ty_bare_fn(@ast::TyBareFn {decl: ref decl, _}) => {
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// fn() binds the & region, so do not consider &T types that
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// appear *inside* a fn() type to affect the enclosing item:
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do cx.with(cx.item_id, false) {
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// parameters are contravariant
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do cx.with_ambient_variance(rv_contravariant) {
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for decl.inputs.each |a| {
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(visitor.visit_ty)(a.ty, cx, visitor);
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}
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}
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(visitor.visit_ty)(decl.output, cx, visitor);
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}
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}
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_ => {
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visit::visit_ty(ty, cx, visitor);
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}
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}
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fn visit_mt(mt: ast::mt,
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cx: @mut DetermineRpCtxt,
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visitor: visit::vt<@mut DetermineRpCtxt>) {
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// mutability is invariant
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if mt.mutbl == ast::m_mutbl {
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do cx.with_ambient_variance(rv_invariant) {
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(visitor.visit_ty)(mt.ty, cx, visitor);
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}
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} else {
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(visitor.visit_ty)(mt.ty, cx, visitor);
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}
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}
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}
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pub fn determine_rp_in_struct_field(
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cm: @ast::struct_field,
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cx: @mut DetermineRpCtxt,
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visitor: visit::vt<@mut DetermineRpCtxt>) {
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match cm.node.kind {
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ast::named_field(_, ast::struct_mutable, _) => {
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do cx.with_ambient_variance(rv_invariant) {
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visit::visit_struct_field(cm, cx, visitor);
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}
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}
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ast::named_field(_, ast::struct_immutable, _) |
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ast::unnamed_field => {
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visit::visit_struct_field(cm, cx, visitor);
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}
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}
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}
|
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|
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pub fn determine_rp_in_crate(sess: Session,
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ast_map: ast_map::map,
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def_map: resolve::DefMap,
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crate: @ast::crate)
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-> region_paramd_items {
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let cx = @mut DetermineRpCtxt {
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sess: sess,
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ast_map: ast_map,
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def_map: def_map,
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region_paramd_items: @mut HashMap::new(),
|
|
dep_map: @mut HashMap::new(),
|
|
worklist: ~[],
|
|
item_id: 0,
|
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anon_implies_rp: false,
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ambient_variance: rv_covariant
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|
};
|
|
|
|
// Gather up the base set, worklist and dep_map
|
|
let visitor = visit::mk_vt(@visit::Visitor {
|
|
visit_fn: determine_rp_in_fn,
|
|
visit_item: determine_rp_in_item,
|
|
visit_ty: determine_rp_in_ty,
|
|
visit_ty_method: determine_rp_in_ty_method,
|
|
visit_struct_field: determine_rp_in_struct_field,
|
|
.. *visit::default_visitor()
|
|
});
|
|
visit::visit_crate(crate, cx, visitor);
|
|
|
|
// Propagate indirect dependencies
|
|
//
|
|
// Each entry in the worklist is the id of an item C whose region
|
|
// parameterization has been updated. So we pull ids off of the
|
|
// worklist, find the current variance, and then iterate through
|
|
// all of the dependent items (that is, those items that reference
|
|
// C). For each dependent item D, we combine the variance of C
|
|
// with the ambient variance where the reference occurred and then
|
|
// update the region-parameterization of D to reflect the result.
|
|
{
|
|
let cx = &mut *cx;
|
|
while cx.worklist.len() != 0 {
|
|
let c_id = cx.worklist.pop();
|
|
let c_variance = *cx.region_paramd_items.get(&c_id);
|
|
debug!("popped %d from worklist", c_id);
|
|
match cx.dep_map.find(&c_id) {
|
|
None => {}
|
|
Some(deps) => {
|
|
for deps.each |dep| {
|
|
let v = add_variance(dep.ambient_variance, c_variance);
|
|
cx.add_rp(dep.id, v);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
debug!("%s", {
|
|
debug!("Region variance results:");
|
|
let region_paramd_items = cx.region_paramd_items;
|
|
for region_paramd_items.each |&key, &value| {
|
|
debug!("item %? (%s) is parameterized with variance %?",
|
|
key,
|
|
ast_map::node_id_to_str(ast_map, key,
|
|
sess.parse_sess.interner),
|
|
value);
|
|
}
|
|
"----"
|
|
});
|
|
|
|
// return final set
|
|
return cx.region_paramd_items;
|
|
}
|