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.
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.
12 use rustc::ty::{self, TyCtxt};
14 use rustc::util::nodemap::FxHashMap;
15 use rustc_data_structures::indexed_vec::{IndexVec};
16 use syntax_pos::{Span};
19 use std::ops::{Index, IndexMut};
21 use self::abs_domain::{AbstractElem, Lift};
25 // This submodule holds some newtype'd Index wrappers that are using
26 // NonZero to ensure that Option<Index> occupies only a single word.
27 // They are in a submodule to impose privacy restrictions; namely, to
28 // ensure that other code does not accidentally access `index.0`
29 // (which is likely to yield a subtle off-by-one error).
30 pub(crate) mod indexes {
32 use std::num::NonZeroUsize;
33 use rustc_data_structures::indexed_vec::Idx;
35 macro_rules! new_index {
36 ($Index:ident, $debug_name:expr) => {
37 #[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
38 pub struct $Index(NonZeroUsize);
41 fn new(idx: usize) -> Self {
42 $Index(NonZeroUsize::new(idx + 1).unwrap())
44 fn index(self) -> usize {
49 impl fmt::Debug for $Index {
50 fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
51 write!(fmt, "{}{}", $debug_name, self.index())
57 /// Index into MovePathData.move_paths
58 new_index!(MovePathIndex, "mp");
60 /// Index into MoveData.moves.
61 new_index!(MoveOutIndex, "mo");
63 /// Index into MoveData.inits.
64 new_index!(InitIndex, "in");
66 /// Index into Borrows.locations
67 new_index!(BorrowIndex, "bw");
70 pub use self::indexes::MovePathIndex;
71 pub use self::indexes::MoveOutIndex;
72 pub use self::indexes::InitIndex;
75 pub fn move_path_index(&self, move_data: &MoveData) -> MovePathIndex {
76 move_data.moves[*self].path
80 /// `MovePath` is a canonicalized representation of a path that is
81 /// moved or assigned to.
83 /// It follows a tree structure.
85 /// Given `struct X { m: M, n: N }` and `x: X`, moves like `drop x.m;`
86 /// move *out* of the place `x.m`.
88 /// The MovePaths representing `x.m` and `x.n` are siblings (that is,
89 /// one of them will link to the other via the `next_sibling` field,
90 /// and the other will have no entry in its `next_sibling` field), and
91 /// they both have the MovePath representing `x` as their parent.
93 pub struct MovePath<'tcx> {
94 pub next_sibling: Option<MovePathIndex>,
95 pub first_child: Option<MovePathIndex>,
96 pub parent: Option<MovePathIndex>,
97 pub place: Place<'tcx>,
100 impl<'tcx> MovePath<'tcx> {
101 pub fn parents(&self, move_paths: &IndexVec<MovePathIndex, MovePath>) -> Vec<MovePathIndex> {
102 let mut parents = Vec::new();
104 let mut curr_parent = self.parent;
105 while let Some(parent_mpi) = curr_parent {
106 parents.push(parent_mpi);
107 curr_parent = move_paths[parent_mpi].parent;
114 impl<'tcx> fmt::Debug for MovePath<'tcx> {
115 fn fmt(&self, w: &mut fmt::Formatter) -> fmt::Result {
116 write!(w, "MovePath {{")?;
117 if let Some(parent) = self.parent {
118 write!(w, " parent: {:?},", parent)?;
120 if let Some(first_child) = self.first_child {
121 write!(w, " first_child: {:?},", first_child)?;
123 if let Some(next_sibling) = self.next_sibling {
124 write!(w, " next_sibling: {:?}", next_sibling)?;
126 write!(w, " place: {:?} }}", self.place)
130 impl<'tcx> fmt::Display for MovePath<'tcx> {
131 fn fmt(&self, w: &mut fmt::Formatter) -> fmt::Result {
132 write!(w, "{:?}", self.place)
137 pub struct MoveData<'tcx> {
138 pub move_paths: IndexVec<MovePathIndex, MovePath<'tcx>>,
139 pub moves: IndexVec<MoveOutIndex, MoveOut>,
140 /// Each Location `l` is mapped to the MoveOut's that are effects
141 /// of executing the code at `l`. (There can be multiple MoveOut's
142 /// for a given `l` because each MoveOut is associated with one
143 /// particular path being moved.)
144 pub loc_map: LocationMap<Vec<MoveOutIndex>>,
145 pub path_map: IndexVec<MovePathIndex, Vec<MoveOutIndex>>,
146 pub rev_lookup: MovePathLookup<'tcx>,
147 pub inits: IndexVec<InitIndex, Init>,
148 /// Each Location `l` is mapped to the Inits that are effects
149 /// of executing the code at `l`.
150 pub init_loc_map: LocationMap<Vec<InitIndex>>,
151 pub init_path_map: IndexVec<MovePathIndex, Vec<InitIndex>>,
154 pub trait HasMoveData<'tcx> {
155 fn move_data(&self) -> &MoveData<'tcx>;
159 pub struct LocationMap<T> {
160 /// Location-indexed (BasicBlock for outer index, index within BB
161 /// for inner index) map.
162 pub(crate) map: IndexVec<BasicBlock, Vec<T>>,
165 impl<T> Index<Location> for LocationMap<T> {
167 fn index(&self, index: Location) -> &Self::Output {
168 &self.map[index.block][index.statement_index]
172 impl<T> IndexMut<Location> for LocationMap<T> {
173 fn index_mut(&mut self, index: Location) -> &mut Self::Output {
174 &mut self.map[index.block][index.statement_index]
178 impl<T> LocationMap<T> where T: Default + Clone {
179 fn new(mir: &Mir) -> Self {
181 map: mir.basic_blocks().iter().map(|block| {
182 vec![T::default(); block.statements.len()+1]
188 /// `MoveOut` represents a point in a program that moves out of some
189 /// L-value; i.e., "creates" uninitialized memory.
191 /// With respect to dataflow analysis:
192 /// - Generated by moves and declaration of uninitialized variables.
193 /// - Killed by assignments to the memory.
194 #[derive(Copy, Clone)]
197 pub path: MovePathIndex,
199 pub source: Location,
202 impl fmt::Debug for MoveOut {
203 fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
204 write!(fmt, "{:?}@{:?}", self.path, self.source)
208 /// `Init` represents a point in a program that initializes some L-value;
209 #[derive(Copy, Clone)]
211 /// path being initialized
212 pub path: MovePathIndex,
213 /// location of initialization
214 pub location: InitLocation,
215 /// Extra information about this initialization
220 /// Initializations can be from an argument or from a statement. Arguments
221 /// do not have locations, in those cases the `Local` is kept..
222 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
223 pub enum InitLocation {
228 /// Additional information about the initialization.
229 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
231 /// Deep init, even on panic
233 /// Only does a shallow init
235 /// This doesn't initialize the variable on panic (and a panic is possible).
239 impl fmt::Debug for Init {
240 fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
241 write!(fmt, "{:?}@{:?} ({:?})", self.path, self.location, self.kind)
246 crate fn span<'gcx>(&self, mir: &Mir<'gcx>) -> Span {
247 match self.location {
248 InitLocation::Argument(local) => mir.local_decls[local].source_info.span,
249 InitLocation::Statement(location) => mir.source_info(location).span,
254 /// Tables mapping from a place to its MovePathIndex.
256 pub struct MovePathLookup<'tcx> {
257 locals: IndexVec<Local, MovePathIndex>,
259 /// projections are made from a base-place and a projection
260 /// elem. The base-place will have a unique MovePathIndex; we use
261 /// the latter as the index into the outer vector (narrowing
262 /// subsequent search so that it is solely relative to that
263 /// base-place). For the remaining lookup, we map the projection
264 /// elem to the associated MovePathIndex.
265 projections: FxHashMap<(MovePathIndex, AbstractElem<'tcx>), MovePathIndex>
270 #[derive(Copy, Clone, Debug)]
271 pub enum LookupResult {
272 Exact(MovePathIndex),
273 Parent(Option<MovePathIndex>)
276 impl<'tcx> MovePathLookup<'tcx> {
277 // Unlike the builder `fn move_path_for` below, this lookup
278 // alternative will *not* create a MovePath on the fly for an
279 // unknown place, but will rather return the nearest available
281 pub fn find(&self, place: &Place<'tcx>) -> LookupResult {
283 Place::Local(local) => LookupResult::Exact(self.locals[local]),
285 Place::Static(..) => LookupResult::Parent(None),
286 Place::Projection(ref proj) => {
287 match self.find(&proj.base) {
288 LookupResult::Exact(base_path) => {
289 match self.projections.get(&(base_path, proj.elem.lift())) {
290 Some(&subpath) => LookupResult::Exact(subpath),
291 None => LookupResult::Parent(Some(base_path))
300 pub fn find_local(&self, local: Local) -> MovePathIndex {
306 pub struct IllegalMoveOrigin<'tcx> {
307 pub(crate) location: Location,
308 pub(crate) kind: IllegalMoveOriginKind<'tcx>,
312 pub(crate) enum IllegalMoveOriginKind<'tcx> {
313 /// Illegal move due to attempt to move from `static` variable.
316 /// Illegal move due to attempt to move from behind a reference.
318 /// The place the reference refers to: if erroneous code was trying to
319 /// move from `(*x).f` this will be `*x`.
320 target_place: Place<'tcx>,
323 /// Illegal move due to attempt to move from field of an ADT that
324 /// implements `Drop`. Rust maintains invariant that all `Drop`
325 /// ADT's remain fully-initialized so that user-defined destructor
326 /// can safely read from all of the ADT's fields.
327 InteriorOfTypeWithDestructor { container_ty: ty::Ty<'tcx> },
329 /// Illegal move due to attempt to move out of a slice or array.
330 InteriorOfSliceOrArray { ty: ty::Ty<'tcx>, is_index: bool, },
334 pub enum MoveError<'tcx> {
335 IllegalMove { cannot_move_out_of: IllegalMoveOrigin<'tcx> },
336 UnionMove { path: MovePathIndex },
339 impl<'tcx> MoveError<'tcx> {
340 fn cannot_move_out_of(location: Location, kind: IllegalMoveOriginKind<'tcx>) -> Self {
341 let origin = IllegalMoveOrigin { location, kind };
342 MoveError::IllegalMove { cannot_move_out_of: origin }
346 impl<'a, 'gcx, 'tcx> MoveData<'tcx> {
347 pub fn gather_moves(mir: &Mir<'tcx>, tcx: TyCtxt<'a, 'gcx, 'tcx>)
348 -> Result<Self, (Self, Vec<(Place<'tcx>, MoveError<'tcx>)>)> {
349 builder::gather_moves(mir, tcx)
352 /// For the move path `mpi`, returns the root local variable (if any) that starts the path.
353 /// (e.g., for a path like `a.b.c` returns `Some(a)`)
354 pub fn base_local(&self, mut mpi: MovePathIndex) -> Option<Local> {
356 let path = &self.move_paths[mpi];
357 if let Place::Local(l) = path.place { return Some(l); }
358 if let Some(parent) = path.parent { mpi = parent; continue } else { return None }