src/librustc_mir/borrow_check/place_ext.rs

   1 // Copyright 2012-2014 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 use rustc::hir;
  12 use rustc::mir::ProjectionElem;
  13 use rustc::mir::{Local, Mir, Place};
  14 use rustc::ty::{self, TyCtxt};
  15
  16 /// Extension methods for the `Place` type.
  17 crate trait PlaceExt<'tcx> {
  18     /// True if this is a deref of a raw pointer.
  19     fn is_unsafe_place(&self, tcx: TyCtxt<'_, '_, 'tcx>, mir: &Mir<'tcx>) -> bool;
  20
  21     /// If this is a place like `x.f.g`, returns the local
  22     /// `x`. Returns `None` if this is based in a static.
  23     fn root_local(&self) -> Option<Local>;
  24 }
  25
  26 impl<'tcx> PlaceExt<'tcx> for Place<'tcx> {
  27     fn is_unsafe_place(&self, tcx: TyCtxt<'_, '_, 'tcx>, mir: &Mir<'tcx>) -> bool {
  28         match self {
  29             Place::Local(_) => false,
  30             Place::Static(static_) => {
  31                 tcx.is_static(static_.def_id) == Some(hir::Mutability::MutMutable)
  32             }
  33             Place::Projection(proj) => match proj.elem {
  34                 ProjectionElem::Field(..)
  35                 | ProjectionElem::Downcast(..)
  36                 | ProjectionElem::Subslice { .. }
  37                 | ProjectionElem::ConstantIndex { .. }
  38                 | ProjectionElem::Index(_) => proj.base.is_unsafe_place(tcx, mir),
  39                 ProjectionElem::Deref => {
  40                     let ty = proj.base.ty(mir, tcx).to_ty(tcx);
  41                     match ty.sty {
  42                         ty::TyRawPtr(..) => true,
  43                         _ => proj.base.is_unsafe_place(tcx, mir),
  44                     }
  45                 }
  46             },
  47         }
  48     }
  49
  50     fn root_local(&self) -> Option<Local> {
  51         let mut p = self;
  52         loop {
  53             match p {
  54                 Place::Projection(pi) => p = &pi.base,
  55                 Place::Static(_) => return None,
  56                 Place::Local(l) => return Some(*l),
  57             }
  58         }
  59     }
  60 }