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use crate::hir::place::{
Place as HirPlace, PlaceBase as HirPlaceBase, ProjectionKind as HirProjectionKind,
};
use crate::{mir, ty};
use std::fmt::Write;
use crate::query::Providers;
use rustc_data_structures::fx::FxIndexMap;
use rustc_hir as hir;
use rustc_hir::def_id::LocalDefId;
use rustc_span::def_id::LocalDefIdMap;
use rustc_span::symbol::Ident;
use rustc_span::{Span, Symbol};
use super::TyCtxt;
use self::BorrowKind::*;
/// Captures are represented using fields inside a structure.
/// This represents accessing self in the closure structure
pub const CAPTURE_STRUCT_LOCAL: mir::Local = mir::Local::from_u32(1);
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable, HashStable)]
#[derive(TypeFoldable, TypeVisitable)]
pub struct UpvarPath {
pub hir_id: hir::HirId,
}
/// Upvars do not get their own `NodeId`. Instead, we use the pair of
/// the original var ID (that is, the root variable that is referenced
/// by the upvar) and the ID of the closure expression.
#[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable, HashStable)]
#[derive(TypeFoldable, TypeVisitable)]
pub struct UpvarId {
pub var_path: UpvarPath,
pub closure_expr_id: LocalDefId,
}
impl UpvarId {
pub fn new(var_hir_id: hir::HirId, closure_def_id: LocalDefId) -> UpvarId {
UpvarId { var_path: UpvarPath { hir_id: var_hir_id }, closure_expr_id: closure_def_id }
}
}
/// Information describing the capture of an upvar. This is computed
/// during `typeck`, specifically by `regionck`.
#[derive(PartialEq, Clone, Debug, Copy, TyEncodable, TyDecodable, HashStable)]
#[derive(TypeFoldable, TypeVisitable)]
pub enum UpvarCapture {
/// Upvar is captured by value. This is always true when the
/// closure is labeled `move`, but can also be true in other cases
/// depending on inference.
ByValue,
/// Upvar is captured by reference.
ByRef(BorrowKind),
}
/// Given the closure DefId this map provides a map of root variables to minimum
/// set of `CapturedPlace`s that need to be tracked to support all captures of that closure.
pub type MinCaptureInformationMap<'tcx> = LocalDefIdMap<RootVariableMinCaptureList<'tcx>>;
/// Part of `MinCaptureInformationMap`; Maps a root variable to the list of `CapturedPlace`.
/// Used to track the minimum set of `Place`s that need to be captured to support all
/// Places captured by the closure starting at a given root variable.
///
/// This provides a convenient and quick way of checking if a variable being used within
/// a closure is a capture of a local variable.
pub type RootVariableMinCaptureList<'tcx> = FxIndexMap<hir::HirId, MinCaptureList<'tcx>>;
/// Part of `MinCaptureInformationMap`; List of `CapturePlace`s.
pub type MinCaptureList<'tcx> = Vec<CapturedPlace<'tcx>>;
/// A composite describing a `Place` that is captured by a closure.
#[derive(PartialEq, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
#[derive(TypeFoldable, TypeVisitable)]
pub struct CapturedPlace<'tcx> {
/// Name and span where the binding happens.
pub var_ident: Ident,
/// The `Place` that is captured.
pub place: HirPlace<'tcx>,
/// `CaptureKind` and expression(s) that resulted in such capture of `place`.
pub info: CaptureInfo,
/// Represents if `place` can be mutated or not.
pub mutability: hir::Mutability,
/// Region of the resulting reference if the upvar is captured by ref.
pub region: Option<ty::Region<'tcx>>,
}
impl<'tcx> CapturedPlace<'tcx> {
pub fn to_string(&self, tcx: TyCtxt<'tcx>) -> String {
place_to_string_for_capture(tcx, &self.place)
}
/// Returns a symbol of the captured upvar, which looks like `name__field1__field2`.
pub fn to_symbol(&self) -> Symbol {
let mut symbol = self.var_ident.to_string();
let mut ty = self.place.base_ty;
for proj in self.place.projections.iter() {
match proj.kind {
HirProjectionKind::Field(idx, variant) => match ty.kind() {
ty::Tuple(_) => write!(&mut symbol, "__{}", idx.index()).unwrap(),
ty::Adt(def, ..) => {
write!(
&mut symbol,
"__{}",
def.variant(variant).fields[idx].name.as_str(),
)
.unwrap();
}
ty => {
bug!("Unexpected type {:?} for `Field` projection", ty)
}
},
// Ignore derefs for now, as they are likely caused by
// autoderefs that don't appear in the original code.
HirProjectionKind::Deref => {}
// Just change the type to the hidden type, so we can actually project.
HirProjectionKind::OpaqueCast => {}
proj => bug!("Unexpected projection {:?} in captured place", proj),
}
ty = proj.ty;
}
Symbol::intern(&symbol)
}
/// Returns the hir-id of the root variable for the captured place.
/// e.g., if `a.b.c` was captured, would return the hir-id for `a`.
pub fn get_root_variable(&self) -> hir::HirId {
match self.place.base {
HirPlaceBase::Upvar(upvar_id) => upvar_id.var_path.hir_id,
base => bug!("Expected upvar, found={:?}", base),
}
}
/// Returns the `LocalDefId` of the closure that captured this Place
pub fn get_closure_local_def_id(&self) -> LocalDefId {
match self.place.base {
HirPlaceBase::Upvar(upvar_id) => upvar_id.closure_expr_id,
base => bug!("expected upvar, found={:?}", base),
}
}
/// Return span pointing to use that resulted in selecting the captured path
pub fn get_path_span(&self, tcx: TyCtxt<'tcx>) -> Span {
if let Some(path_expr_id) = self.info.path_expr_id {
tcx.hir().span(path_expr_id)
} else if let Some(capture_kind_expr_id) = self.info.capture_kind_expr_id {
tcx.hir().span(capture_kind_expr_id)
} else {
// Fallback on upvars mentioned if neither path or capture expr id is captured
// Safe to unwrap since we know this place is captured by the closure, therefore the closure must have upvars.
tcx.upvars_mentioned(self.get_closure_local_def_id()).unwrap()
[&self.get_root_variable()]
.span
}
}
/// Return span pointing to use that resulted in selecting the current capture kind
pub fn get_capture_kind_span(&self, tcx: TyCtxt<'tcx>) -> Span {
if let Some(capture_kind_expr_id) = self.info.capture_kind_expr_id {
tcx.hir().span(capture_kind_expr_id)
} else if let Some(path_expr_id) = self.info.path_expr_id {
tcx.hir().span(path_expr_id)
} else {
// Fallback on upvars mentioned if neither path or capture expr id is captured
// Safe to unwrap since we know this place is captured by the closure, therefore the closure must have upvars.
tcx.upvars_mentioned(self.get_closure_local_def_id()).unwrap()
[&self.get_root_variable()]
.span
}
}
pub fn is_by_ref(&self) -> bool {
match self.info.capture_kind {
ty::UpvarCapture::ByValue => false,
ty::UpvarCapture::ByRef(..) => true,
}
}
}
#[derive(Copy, Clone, Debug, HashStable)]
pub struct ClosureTypeInfo<'tcx> {
user_provided_sig: ty::CanonicalPolyFnSig<'tcx>,
captures: &'tcx [&'tcx ty::CapturedPlace<'tcx>],
kind_origin: Option<&'tcx (Span, HirPlace<'tcx>)>,
}
fn closure_typeinfo<'tcx>(tcx: TyCtxt<'tcx>, def: LocalDefId) -> ClosureTypeInfo<'tcx> {
debug_assert!(tcx.is_closure_like(def.to_def_id()));
let typeck_results = tcx.typeck(def);
let user_provided_sig = typeck_results.user_provided_sigs[&def];
let captures = typeck_results.closure_min_captures_flattened(def);
let captures = tcx.arena.alloc_from_iter(captures);
let hir_id = tcx.local_def_id_to_hir_id(def);
let kind_origin = typeck_results.closure_kind_origins().get(hir_id);
ClosureTypeInfo { user_provided_sig, captures, kind_origin }
}
impl<'tcx> TyCtxt<'tcx> {
pub fn closure_kind_origin(self, def_id: LocalDefId) -> Option<&'tcx (Span, HirPlace<'tcx>)> {
self.closure_typeinfo(def_id).kind_origin
}
pub fn closure_user_provided_sig(self, def_id: LocalDefId) -> ty::CanonicalPolyFnSig<'tcx> {
self.closure_typeinfo(def_id).user_provided_sig
}
pub fn closure_captures(self, def_id: LocalDefId) -> &'tcx [&'tcx ty::CapturedPlace<'tcx>] {
if !self.is_closure_like(def_id.to_def_id()) {
return &[];
};
self.closure_typeinfo(def_id).captures
}
}
/// Return true if the `proj_possible_ancestor` represents an ancestor path
/// to `proj_capture` or `proj_possible_ancestor` is same as `proj_capture`,
/// assuming they both start off of the same root variable.
///
/// **Note:** It's the caller's responsibility to ensure that both lists of projections
/// start off of the same root variable.
///
/// Eg: 1. `foo.x` which is represented using `projections=[Field(x)]` is an ancestor of
/// `foo.x.y` which is represented using `projections=[Field(x), Field(y)]`.
/// Note both `foo.x` and `foo.x.y` start off of the same root variable `foo`.
/// 2. Since we only look at the projections here function will return `bar.x` as an a valid
/// ancestor of `foo.x.y`. It's the caller's responsibility to ensure that both projections
/// list are being applied to the same root variable.
pub fn is_ancestor_or_same_capture(
proj_possible_ancestor: &[HirProjectionKind],
proj_capture: &[HirProjectionKind],
) -> bool {
// We want to make sure `is_ancestor_or_same_capture("x.0.0", "x.0")` to return false.
// Therefore we can't just check if all projections are same in the zipped iterator below.
if proj_possible_ancestor.len() > proj_capture.len() {
return false;
}
proj_possible_ancestor.iter().zip(proj_capture).all(|(a, b)| a == b)
}
/// Part of `MinCaptureInformationMap`; describes the capture kind (&, &mut, move)
/// for a particular capture as well as identifying the part of the source code
/// that triggered this capture to occur.
#[derive(PartialEq, Clone, Debug, Copy, TyEncodable, TyDecodable, HashStable)]
#[derive(TypeFoldable, TypeVisitable)]
pub struct CaptureInfo {
/// Expr Id pointing to use that resulted in selecting the current capture kind
///
/// Eg:
/// ```rust,no_run
/// let mut t = (0,1);
///
/// let c = || {
/// println!("{t:?}"); // L1
/// t.1 = 4; // L2
/// };
/// ```
/// `capture_kind_expr_id` will point to the use on L2 and `path_expr_id` will point to the
/// use on L1.
///
/// If the user doesn't enable feature `capture_disjoint_fields` (RFC 2229) then, it is
/// possible that we don't see the use of a particular place resulting in capture_kind_expr_id being
/// None. In such case we fallback on uvpars_mentioned for span.
///
/// Eg:
/// ```rust,no_run
/// let x = 5;
///
/// let c = || {
/// let _ = x;
/// };
/// ```
///
/// In this example, if `capture_disjoint_fields` is **not** set, then x will be captured,
/// but we won't see it being used during capture analysis, since it's essentially a discard.
pub capture_kind_expr_id: Option<hir::HirId>,
/// Expr Id pointing to use that resulted the corresponding place being captured
///
/// See `capture_kind_expr_id` for example.
///
pub path_expr_id: Option<hir::HirId>,
/// Capture mode that was selected
pub capture_kind: UpvarCapture,
}
pub fn place_to_string_for_capture<'tcx>(tcx: TyCtxt<'tcx>, place: &HirPlace<'tcx>) -> String {
let mut curr_string: String = match place.base {
HirPlaceBase::Upvar(upvar_id) => tcx.hir().name(upvar_id.var_path.hir_id).to_string(),
_ => bug!("Capture_information should only contain upvars"),
};
for (i, proj) in place.projections.iter().enumerate() {
match proj.kind {
HirProjectionKind::Deref => {
curr_string = format!("*{curr_string}");
}
HirProjectionKind::Field(idx, variant) => match place.ty_before_projection(i).kind() {
ty::Adt(def, ..) => {
curr_string = format!(
"{}.{}",
curr_string,
def.variant(variant).fields[idx].name.as_str()
);
}
ty::Tuple(_) => {
curr_string = format!("{}.{}", curr_string, idx.index());
}
_ => {
bug!(
"Field projection applied to a type other than Adt or Tuple: {:?}.",
place.ty_before_projection(i).kind()
)
}
},
proj => bug!("{:?} unexpected because it isn't captured", proj),
}
}
curr_string
}
#[derive(Clone, PartialEq, Debug, TyEncodable, TyDecodable, Copy, HashStable)]
#[derive(TypeFoldable, TypeVisitable)]
pub enum BorrowKind {
/// Data must be immutable and is aliasable.
ImmBorrow,
/// Data must be immutable but not aliasable. This kind of borrow
/// cannot currently be expressed by the user and is used only in
/// implicit closure bindings. It is needed when the closure
/// is borrowing or mutating a mutable referent, e.g.:
///
/// ```
/// let mut z = 3;
/// let x: &mut isize = &mut z;
/// let y = || *x += 5;
/// ```
///
/// If we were to try to translate this closure into a more explicit
/// form, we'd encounter an error with the code as written:
///
/// ```compile_fail,E0594
/// struct Env<'a> { x: &'a &'a mut isize }
/// let mut z = 3;
/// let x: &mut isize = &mut z;
/// let y = (&mut Env { x: &x }, fn_ptr); // Closure is pair of env and fn
/// fn fn_ptr(env: &mut Env) { **env.x += 5; }
/// ```
///
/// This is then illegal because you cannot mutate a `&mut` found
/// in an aliasable location. To solve, you'd have to translate with
/// an `&mut` borrow:
///
/// ```compile_fail,E0596
/// struct Env<'a> { x: &'a mut &'a mut isize }
/// let mut z = 3;
/// let x: &mut isize = &mut z;
/// let y = (&mut Env { x: &mut x }, fn_ptr); // changed from &x to &mut x
/// fn fn_ptr(env: &mut Env) { **env.x += 5; }
/// ```
///
/// Now the assignment to `**env.x` is legal, but creating a
/// mutable pointer to `x` is not because `x` is not mutable. We
/// could fix this by declaring `x` as `let mut x`. This is ok in
/// user code, if awkward, but extra weird for closures, since the
/// borrow is hidden.
///
/// So we introduce a "unique imm" borrow -- the referent is
/// immutable, but not aliasable. This solves the problem. For
/// simplicity, we don't give users the way to express this
/// borrow, it's just used when translating closures.
///
/// FIXME: Rename this to indicate the borrow is actually not immutable.
UniqueImmBorrow,
/// Data is mutable and not aliasable.
MutBorrow,
}
impl BorrowKind {
pub fn from_mutbl(m: hir::Mutability) -> BorrowKind {
match m {
hir::Mutability::Mut => MutBorrow,
hir::Mutability::Not => ImmBorrow,
}
}
/// Returns a mutability `m` such that an `&m T` pointer could be used to obtain this borrow
/// kind. Because borrow kinds are richer than mutabilities, we sometimes have to pick a
/// mutability that is stronger than necessary so that it at least *would permit* the borrow in
/// question.
pub fn to_mutbl_lossy(self) -> hir::Mutability {
match self {
MutBorrow => hir::Mutability::Mut,
ImmBorrow => hir::Mutability::Not,
// We have no type corresponding to a unique imm borrow, so
// use `&mut`. It gives all the capabilities of a `&uniq`
// and hence is a safe "over approximation".
UniqueImmBorrow => hir::Mutability::Mut,
}
}
}
pub fn provide(providers: &mut Providers) {
*providers = Providers { closure_typeinfo, ..*providers }
}