src/librustc_mir/dataflow/move_paths/abs_domain.rs

   1 // Copyright 2012-2016 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! The move-analysis portion of borrowck needs to work in an abstract
  12 //! domain of lifted Lvalues.  Most of the Lvalue variants fall into a
  13 //! one-to-one mapping between the concrete and abstract (e.g. a
  14 //! field-deref on a local-variable, `x.field`, has the same meaning
  15 //! in both domains). Indexed-Projections are the exception: `a[x]`
  16 //! needs to be treated as mapping to the same move path as `a[y]` as
  17 //! well as `a[13]`, et cetera.
  18 //!
  19 //! (In theory the analysis could be extended to work with sets of
  20 //! paths, so that `a[0]` and `a[13]` could be kept distinct, while
  21 //! `a[x]` would still overlap them both. But that is not this
  22 //! representation does today.)
  23
  24 use rustc::mir::LvalueElem;
  25 use rustc::mir::{Operand, ProjectionElem};
  26
  27 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
  28 pub struct AbstractOperand;
  29 pub type AbstractElem<'tcx> =
  30     ProjectionElem<'tcx, AbstractOperand>;
  31
  32 pub trait Lift {
  33     type Abstract;
  34     fn lift(&self) -> Self::Abstract;
  35 }
  36 impl<'tcx> Lift for Operand<'tcx> {
  37     type Abstract = AbstractOperand;
  38     fn lift(&self) -> Self::Abstract { AbstractOperand }
  39 }
  40 impl<'tcx> Lift for LvalueElem<'tcx> {
  41     type Abstract = AbstractElem<'tcx>;
  42     fn lift(&self) -> Self::Abstract {
  43         match *self {
  44             ProjectionElem::Deref =>
  45                 ProjectionElem::Deref,
  46             ProjectionElem::Field(ref f, ty) =>
  47                 ProjectionElem::Field(f.clone(), ty.clone()),
  48             ProjectionElem::Index(ref i) =>
  49                 ProjectionElem::Index(i.lift()),
  50             ProjectionElem::Subslice {from, to} =>
  51                 ProjectionElem::Subslice { from: from, to: to },
  52             ProjectionElem::ConstantIndex {offset,min_length,from_end} =>
  53                 ProjectionElem::ConstantIndex {
  54                     offset: offset,
  55                     min_length: min_length,
  56                     from_end: from_end
  57                 },
  58             ProjectionElem::Downcast(a, u) =>
  59                 ProjectionElem::Downcast(a.clone(), u.clone()),
  60         }
  61     }
  62 }