1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use rustc::ty::subst::Substs;
use rustc::ty::{self, CanonicalTy, ClosureSubsts, GeneratorSubsts, Ty, TypeFoldable};
use rustc::mir::{BasicBlock, Location, Mir, Place, Statement, StatementKind};
use rustc::mir::visit::{MutVisitor, TyContext};
use rustc::infer::{InferCtxt, NLLRegionVariableOrigin};

/// Replaces all free regions appearing in the MIR with fresh
/// inference variables, returning the number of variables created.
pub fn renumber_mir<'tcx>(infcx: &InferCtxt<'_, '_, 'tcx>, mir: &mut Mir<'tcx>) {
    debug!("renumber_mir()");
    debug!("renumber_mir: mir.arg_count={:?}", mir.arg_count);

    let mut visitor = NLLVisitor { infcx };
    visitor.visit_mir(mir);
}

/// Replaces all regions appearing in `value` with fresh inference
/// variables.
pub fn renumber_regions<'tcx, T>(
    infcx: &InferCtxt<'_, '_, 'tcx>,
    value: &T,
) -> T
where
    T: TypeFoldable<'tcx>,
{
    debug!("renumber_regions(value={:?})", value);

    infcx
        .tcx
        .fold_regions(value, &mut false, |_region, _depth| {
            let origin = NLLRegionVariableOrigin::Existential;
            infcx.next_nll_region_var(origin)
        })
}

struct NLLVisitor<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
    infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
}

impl<'a, 'gcx, 'tcx> NLLVisitor<'a, 'gcx, 'tcx> {
    fn renumber_regions<T>(&mut self, value: &T) -> T
    where
        T: TypeFoldable<'tcx>,
    {
        renumber_regions(self.infcx, value)
    }
}

impl<'a, 'gcx, 'tcx> MutVisitor<'tcx> for NLLVisitor<'a, 'gcx, 'tcx> {
    fn visit_ty(&mut self, ty: &mut Ty<'tcx>, ty_context: TyContext) {
        debug!("visit_ty(ty={:?}, ty_context={:?})", ty, ty_context);

        *ty = self.renumber_regions(ty);

        debug!("visit_ty: ty={:?}", ty);
    }

    fn visit_substs(&mut self, substs: &mut &'tcx Substs<'tcx>, location: Location) {
        debug!("visit_substs(substs={:?}, location={:?})", substs, location);

        *substs = self.renumber_regions(&{ *substs });

        debug!("visit_substs: substs={:?}", substs);
    }

    fn visit_region(&mut self, region: &mut ty::Region<'tcx>, location: Location) {
        debug!("visit_region(region={:?}, location={:?})", region, location);

        let old_region = *region;
        *region = self.renumber_regions(&old_region);

        debug!("visit_region: region={:?}", region);
    }

    fn visit_const(&mut self, constant: &mut &'tcx ty::Const<'tcx>, _location: Location) {
        *constant = self.renumber_regions(&*constant);
    }

    fn visit_generator_substs(&mut self,
                              substs: &mut GeneratorSubsts<'tcx>,
                              location: Location) {
        debug!(
            "visit_generator_substs(substs={:?}, location={:?})",
            substs,
            location,
        );

        *substs = self.renumber_regions(substs);

        debug!("visit_generator_substs: substs={:?}", substs);
    }

    fn visit_closure_substs(&mut self, substs: &mut ClosureSubsts<'tcx>, location: Location) {
        debug!(
            "visit_closure_substs(substs={:?}, location={:?})",
            substs,
            location
        );

        *substs = self.renumber_regions(substs);

        debug!("visit_closure_substs: substs={:?}", substs);
    }

    fn visit_ascribe_user_ty(
        &mut self,
        _place: &mut Place<'tcx>,
        _variance: &mut ty::Variance,
        _c_ty: &mut CanonicalTy<'tcx>,
        _location: Location,
    ) {
        // User-assert-ty statements represent types that the user added explicitly.
        // We don't want to erase the regions from these types: rather, we want to
        // add them as constraints at type-check time.
        debug!("visit_user_assert_ty: skipping renumber");
    }

    fn visit_statement(
        &mut self,
        block: BasicBlock,
        statement: &mut Statement<'tcx>,
        location: Location,
    ) {
        if let StatementKind::EndRegion(_) = statement.kind {
            statement.kind = StatementKind::Nop;
        }
        self.super_statement(block, statement, location);
    }
}