89 lines
3.0 KiB
Rust
89 lines
3.0 KiB
Rust
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// Copyright 2017 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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//! Code to extract the free regions declared on a function and the
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//! relationships between them. For example:
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//!
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//! ```
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//! fn foo<'a, 'b, 'c: 'b>() { }
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//! ```
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//!
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//! here we would be returning a map assigning each of `{'a, 'b, 'c}`
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//! to an index, as well as the `FreeRegionMap` which can compute
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//! relationships between them.
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//!
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//! The code in this file doesn't *do anything* with those results; it
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//! just returns them for other code to use.
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use rustc::infer::InferCtxt;
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use rustc::middle::free_region::FreeRegionMap;
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use rustc::mir::transform::MirSource;
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use rustc::ty;
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use rustc::ty::subst::Substs;
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use rustc::util::nodemap::FxHashMap;
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#[derive(Debug)]
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pub struct FreeRegions<'tcx> {
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/// Given a free region defined on this function (either early- or
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/// late-bound), this maps it to its internal region index. The
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/// corresponding variable will be "capped" so that it cannot
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/// grow.
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pub indices: FxHashMap<ty::Region<'tcx>, usize>,
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/// The map from the typeck tables telling us how to relate free regions.
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pub free_region_map: &'tcx FreeRegionMap<'tcx>,
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}
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pub fn free_regions<'a, 'gcx, 'tcx>(
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infcx: &InferCtxt<'a, 'gcx, 'tcx>,
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source: MirSource,
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) -> FreeRegions<'tcx> {
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debug!("free_regions(source={:?})", source);
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let item_id = source.item_id();
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let item_def_id = infcx.tcx.hir.local_def_id(item_id);
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let mut indices = FxHashMap();
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// Extract the early regions.
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let item_substs = Substs::identity_for_item(infcx.tcx, item_def_id);
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for item_subst in item_substs {
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if let Some(region) = item_subst.as_region() {
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insert_free_region(&mut indices, region);
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}
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}
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// Extract the late-bound regions. Use the liberated fn sigs,
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// where the late-bound regions will have been converted into free
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// regions, and add them to the map.
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let fn_hir_id = infcx.tcx.hir.node_to_hir_id(item_id);
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let tables = infcx.tcx.typeck_tables_of(item_def_id);
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let fn_sig = tables.liberated_fn_sigs()[fn_hir_id].clone();
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infcx
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.tcx
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.for_each_free_region(&fn_sig.inputs_and_output, |region| {
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if let ty::ReFree(_) = *region {
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insert_free_region(&mut indices, region);
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}
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});
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debug!("free_regions: indices={:#?}", indices);
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FreeRegions { indices, free_region_map: &tables.free_region_map }
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}
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fn insert_free_region<'tcx>(
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free_regions: &mut FxHashMap<ty::Region<'tcx>, usize>,
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region: ty::Region<'tcx>,
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) {
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let len = free_regions.len();
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free_regions.entry(region).or_insert(len);
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}
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