1 use crate::hir::place::{
2 Place as HirPlace, PlaceBase as HirPlaceBase, ProjectionKind as HirProjectionKind,
8 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
10 use rustc_hir::def_id::{DefId, LocalDefId};
11 use rustc_span::{Span, Symbol};
13 use super::{Ty, TyCtxt};
15 use self::BorrowKind::*;
17 // Captures are represented using fields inside a structure.
18 // This represents accessing self in the closure structure
19 pub const CAPTURE_STRUCT_LOCAL: mir::Local = mir::Local::from_u32(1);
33 pub struct UpvarPath {
34 pub hir_id: hir::HirId,
37 /// Upvars do not get their own `NodeId`. Instead, we use the pair of
38 /// the original var ID (that is, the root variable that is referenced
39 /// by the upvar) and the ID of the closure expression.
40 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable, TypeFoldable, HashStable)]
42 pub var_path: UpvarPath,
43 pub closure_expr_id: LocalDefId,
47 pub fn new(var_hir_id: hir::HirId, closure_def_id: LocalDefId) -> UpvarId {
48 UpvarId { var_path: UpvarPath { hir_id: var_hir_id }, closure_expr_id: closure_def_id }
52 /// Information describing the capture of an upvar. This is computed
53 /// during `typeck`, specifically by `regionck`.
54 #[derive(PartialEq, Clone, Debug, Copy, TyEncodable, TyDecodable, TypeFoldable, HashStable)]
55 pub enum UpvarCapture {
56 /// Upvar is captured by value. This is always true when the
57 /// closure is labeled `move`, but can also be true in other cases
58 /// depending on inference.
61 /// Upvar is captured by reference.
65 pub type UpvarListMap = FxHashMap<DefId, FxIndexMap<hir::HirId, UpvarId>>;
66 pub type UpvarCaptureMap = FxHashMap<UpvarId, UpvarCapture>;
68 /// Given the closure DefId this map provides a map of root variables to minimum
69 /// set of `CapturedPlace`s that need to be tracked to support all captures of that closure.
70 pub type MinCaptureInformationMap<'tcx> = FxHashMap<DefId, RootVariableMinCaptureList<'tcx>>;
72 /// Part of `MinCaptureInformationMap`; Maps a root variable to the list of `CapturedPlace`.
73 /// Used to track the minimum set of `Place`s that need to be captured to support all
74 /// Places captured by the closure starting at a given root variable.
76 /// This provides a convenient and quick way of checking if a variable being used within
77 /// a closure is a capture of a local variable.
78 pub type RootVariableMinCaptureList<'tcx> = FxIndexMap<hir::HirId, MinCaptureList<'tcx>>;
80 /// Part of `MinCaptureInformationMap`; List of `CapturePlace`s.
81 pub type MinCaptureList<'tcx> = Vec<CapturedPlace<'tcx>>;
83 /// Represents the various closure traits in the language. This
84 /// will determine the type of the environment (`self`, in the
85 /// desugaring) argument that the closure expects.
87 /// You can get the environment type of a closure using
88 /// `tcx.closure_env_ty()`.
89 #[derive(Clone, Copy, PartialOrd, Ord, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)]
91 pub enum ClosureKind {
92 // Warning: Ordering is significant here! The ordering is chosen
93 // because the trait Fn is a subtrait of FnMut and so in turn, and
94 // hence we order it so that Fn < FnMut < FnOnce.
100 impl<'tcx> ClosureKind {
101 // This is the initial value used when doing upvar inference.
102 pub const LATTICE_BOTTOM: ClosureKind = ClosureKind::Fn;
104 /// Returns `true` if a type that impls this closure kind
105 /// must also implement `other`.
106 pub fn extends(self, other: ty::ClosureKind) -> bool {
109 (ClosureKind::Fn, ClosureKind::Fn)
110 | (ClosureKind::Fn, ClosureKind::FnMut)
111 | (ClosureKind::Fn, ClosureKind::FnOnce)
112 | (ClosureKind::FnMut, ClosureKind::FnMut)
113 | (ClosureKind::FnMut, ClosureKind::FnOnce)
114 | (ClosureKind::FnOnce, ClosureKind::FnOnce)
118 /// Returns the representative scalar type for this closure kind.
119 /// See `Ty::to_opt_closure_kind` for more details.
120 pub fn to_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
122 ClosureKind::Fn => tcx.types.i8,
123 ClosureKind::FnMut => tcx.types.i16,
124 ClosureKind::FnOnce => tcx.types.i32,
128 pub fn from_def_id(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ClosureKind> {
129 if Some(def_id) == tcx.lang_items().fn_once_trait() {
130 Some(ClosureKind::FnOnce)
131 } else if Some(def_id) == tcx.lang_items().fn_mut_trait() {
132 Some(ClosureKind::FnMut)
133 } else if Some(def_id) == tcx.lang_items().fn_trait() {
134 Some(ClosureKind::Fn)
141 /// A composite describing a `Place` that is captured by a closure.
142 #[derive(PartialEq, Clone, Debug, TyEncodable, TyDecodable, TypeFoldable, HashStable)]
143 pub struct CapturedPlace<'tcx> {
144 /// The `Place` that is captured.
145 pub place: HirPlace<'tcx>,
147 /// `CaptureKind` and expression(s) that resulted in such capture of `place`.
148 pub info: CaptureInfo,
150 /// Represents if `place` can be mutated or not.
151 pub mutability: hir::Mutability,
153 /// Region of the resulting reference if the upvar is captured by ref.
154 pub region: Option<ty::Region<'tcx>>,
157 impl<'tcx> CapturedPlace<'tcx> {
158 pub fn to_string(&self, tcx: TyCtxt<'tcx>) -> String {
159 place_to_string_for_capture(tcx, &self.place)
162 /// Returns a symbol of the captured upvar, which looks like `name__field1__field2`.
163 fn to_symbol(&self, tcx: TyCtxt<'tcx>) -> Symbol {
164 let hir_id = match self.place.base {
165 HirPlaceBase::Upvar(upvar_id) => upvar_id.var_path.hir_id,
166 base => bug!("Expected an upvar, found {:?}", base),
168 let mut symbol = tcx.hir().name(hir_id).as_str().to_string();
170 let mut ty = self.place.base_ty;
171 for proj in self.place.projections.iter() {
173 HirProjectionKind::Field(idx, variant) => match ty.kind() {
174 ty::Tuple(_) => write!(&mut symbol, "__{}", idx).unwrap(),
175 ty::Adt(def, ..) => {
179 def.variant(variant).fields[idx as usize].name.as_str(),
184 bug!("Unexpected type {:?} for `Field` projection", ty)
188 // Ignore derefs for now, as they are likely caused by
189 // autoderefs that don't appear in the original code.
190 HirProjectionKind::Deref => {}
191 proj => bug!("Unexpected projection {:?} in captured place", proj),
196 Symbol::intern(&symbol)
199 /// Returns the hir-id of the root variable for the captured place.
200 /// e.g., if `a.b.c` was captured, would return the hir-id for `a`.
201 pub fn get_root_variable(&self) -> hir::HirId {
202 match self.place.base {
203 HirPlaceBase::Upvar(upvar_id) => upvar_id.var_path.hir_id,
204 base => bug!("Expected upvar, found={:?}", base),
208 /// Returns the `LocalDefId` of the closure that captured this Place
209 pub fn get_closure_local_def_id(&self) -> LocalDefId {
210 match self.place.base {
211 HirPlaceBase::Upvar(upvar_id) => upvar_id.closure_expr_id,
212 base => bug!("expected upvar, found={:?}", base),
216 /// Return span pointing to use that resulted in selecting the captured path
217 pub fn get_path_span(&self, tcx: TyCtxt<'tcx>) -> Span {
218 if let Some(path_expr_id) = self.info.path_expr_id {
219 tcx.hir().span(path_expr_id)
220 } else if let Some(capture_kind_expr_id) = self.info.capture_kind_expr_id {
221 tcx.hir().span(capture_kind_expr_id)
223 // Fallback on upvars mentioned if neither path or capture expr id is captured
225 // Safe to unwrap since we know this place is captured by the closure, therefore the closure must have upvars.
226 tcx.upvars_mentioned(self.get_closure_local_def_id()).unwrap()
227 [&self.get_root_variable()]
232 /// Return span pointing to use that resulted in selecting the current capture kind
233 pub fn get_capture_kind_span(&self, tcx: TyCtxt<'tcx>) -> Span {
234 if let Some(capture_kind_expr_id) = self.info.capture_kind_expr_id {
235 tcx.hir().span(capture_kind_expr_id)
236 } else if let Some(path_expr_id) = self.info.path_expr_id {
237 tcx.hir().span(path_expr_id)
239 // Fallback on upvars mentioned if neither path or capture expr id is captured
241 // Safe to unwrap since we know this place is captured by the closure, therefore the closure must have upvars.
242 tcx.upvars_mentioned(self.get_closure_local_def_id()).unwrap()
243 [&self.get_root_variable()]
249 fn symbols_for_closure_captures<'tcx>(
251 def_id: (LocalDefId, DefId),
253 let typeck_results = tcx.typeck(def_id.0);
254 let captures = typeck_results.closure_min_captures_flattened(def_id.1);
255 captures.into_iter().map(|captured_place| captured_place.to_symbol(tcx)).collect()
258 /// Return true if the `proj_possible_ancestor` represents an ancestor path
259 /// to `proj_capture` or `proj_possible_ancestor` is same as `proj_capture`,
260 /// assuming they both start off of the same root variable.
262 /// **Note:** It's the caller's responsibility to ensure that both lists of projections
263 /// start off of the same root variable.
265 /// Eg: 1. `foo.x` which is represented using `projections=[Field(x)]` is an ancestor of
266 /// `foo.x.y` which is represented using `projections=[Field(x), Field(y)]`.
267 /// Note both `foo.x` and `foo.x.y` start off of the same root variable `foo`.
268 /// 2. Since we only look at the projections here function will return `bar.x` as an a valid
269 /// ancestor of `foo.x.y`. It's the caller's responsibility to ensure that both projections
270 /// list are being applied to the same root variable.
271 pub fn is_ancestor_or_same_capture(
272 proj_possible_ancestor: &[HirProjectionKind],
273 proj_capture: &[HirProjectionKind],
275 // We want to make sure `is_ancestor_or_same_capture("x.0.0", "x.0")` to return false.
276 // Therefore we can't just check if all projections are same in the zipped iterator below.
277 if proj_possible_ancestor.len() > proj_capture.len() {
281 proj_possible_ancestor.iter().zip(proj_capture).all(|(a, b)| a == b)
284 /// Part of `MinCaptureInformationMap`; describes the capture kind (&, &mut, move)
285 /// for a particular capture as well as identifying the part of the source code
286 /// that triggered this capture to occur.
287 #[derive(PartialEq, Clone, Debug, Copy, TyEncodable, TyDecodable, TypeFoldable, HashStable)]
288 pub struct CaptureInfo {
289 /// Expr Id pointing to use that resulted in selecting the current capture kind
293 /// let mut t = (0,1);
296 /// println!("{t}"); // L1
300 /// `capture_kind_expr_id` will point to the use on L2 and `path_expr_id` will point to the
303 /// If the user doesn't enable feature `capture_disjoint_fields` (RFC 2229) then, it is
304 /// possible that we don't see the use of a particular place resulting in capture_kind_expr_id being
305 /// None. In such case we fallback on uvpars_mentioned for span.
316 /// In this example, if `capture_disjoint_fields` is **not** set, then x will be captured,
317 /// but we won't see it being used during capture analysis, since it's essentially a discard.
318 pub capture_kind_expr_id: Option<hir::HirId>,
319 /// Expr Id pointing to use that resulted the corresponding place being captured
321 /// See `capture_kind_expr_id` for example.
323 pub path_expr_id: Option<hir::HirId>,
325 /// Capture mode that was selected
326 pub capture_kind: UpvarCapture,
329 pub fn place_to_string_for_capture<'tcx>(tcx: TyCtxt<'tcx>, place: &HirPlace<'tcx>) -> String {
330 let mut curr_string: String = match place.base {
331 HirPlaceBase::Upvar(upvar_id) => tcx.hir().name(upvar_id.var_path.hir_id).to_string(),
332 _ => bug!("Capture_information should only contain upvars"),
335 for (i, proj) in place.projections.iter().enumerate() {
337 HirProjectionKind::Deref => {
338 curr_string = format!("*{}", curr_string);
340 HirProjectionKind::Field(idx, variant) => match place.ty_before_projection(i).kind() {
341 ty::Adt(def, ..) => {
342 curr_string = format!(
345 def.variant(variant).fields[idx as usize].name.as_str()
349 curr_string = format!("{}.{}", curr_string, idx);
353 "Field projection applied to a type other than Adt or Tuple: {:?}.",
354 place.ty_before_projection(i).kind()
358 proj => bug!("{:?} unexpected because it isn't captured", proj),
365 #[derive(Clone, PartialEq, Debug, TyEncodable, TyDecodable, TypeFoldable, Copy, HashStable)]
366 pub enum BorrowKind {
367 /// Data must be immutable and is aliasable.
370 /// Data must be immutable but not aliasable. This kind of borrow
371 /// cannot currently be expressed by the user and is used only in
372 /// implicit closure bindings. It is needed when the closure
373 /// is borrowing or mutating a mutable referent, e.g.:
376 /// let x: &mut isize = ...;
377 /// let y = || *x += 5;
380 /// If we were to try to translate this closure into a more explicit
381 /// form, we'd encounter an error with the code as written:
384 /// struct Env { x: & &mut isize }
385 /// let x: &mut isize = ...;
386 /// let y = (&mut Env { &x }, fn_ptr); // Closure is pair of env and fn
387 /// fn fn_ptr(env: &mut Env) { **env.x += 5; }
390 /// This is then illegal because you cannot mutate a `&mut` found
391 /// in an aliasable location. To solve, you'd have to translate with
392 /// an `&mut` borrow:
395 /// struct Env { x: &mut &mut isize }
396 /// let x: &mut isize = ...;
397 /// let y = (&mut Env { &mut x }, fn_ptr); // changed from &x to &mut x
398 /// fn fn_ptr(env: &mut Env) { **env.x += 5; }
401 /// Now the assignment to `**env.x` is legal, but creating a
402 /// mutable pointer to `x` is not because `x` is not mutable. We
403 /// could fix this by declaring `x` as `let mut x`. This is ok in
404 /// user code, if awkward, but extra weird for closures, since the
405 /// borrow is hidden.
407 /// So we introduce a "unique imm" borrow -- the referent is
408 /// immutable, but not aliasable. This solves the problem. For
409 /// simplicity, we don't give users the way to express this
410 /// borrow, it's just used when translating closures.
413 /// Data is mutable and not aliasable.
418 pub fn from_mutbl(m: hir::Mutability) -> BorrowKind {
420 hir::Mutability::Mut => MutBorrow,
421 hir::Mutability::Not => ImmBorrow,
425 /// Returns a mutability `m` such that an `&m T` pointer could be used to obtain this borrow
426 /// kind. Because borrow kinds are richer than mutabilities, we sometimes have to pick a
427 /// mutability that is stronger than necessary so that it at least *would permit* the borrow in
429 pub fn to_mutbl_lossy(self) -> hir::Mutability {
431 MutBorrow => hir::Mutability::Mut,
432 ImmBorrow => hir::Mutability::Not,
434 // We have no type corresponding to a unique imm borrow, so
435 // use `&mut`. It gives all the capabilities of a `&uniq`
436 // and hence is a safe "over approximation".
437 UniqueImmBorrow => hir::Mutability::Mut,
442 pub fn provide(providers: &mut ty::query::Providers) {
443 *providers = ty::query::Providers { symbols_for_closure_captures, ..*providers }