917 lines
35 KiB
Rust
917 lines
35 KiB
Rust
//! A different sort of visitor for walking fn bodies. Unlike the
|
|
//! normal visitor, which just walks the entire body in one shot, the
|
|
//! `ExprUseVisitor` determines how expressions are being used.
|
|
|
|
use std::slice::from_ref;
|
|
|
|
use hir::def::DefKind;
|
|
use hir::Expr;
|
|
// Export these here so that Clippy can use them.
|
|
pub use rustc_middle::hir::place::{Place, PlaceBase, PlaceWithHirId, Projection};
|
|
|
|
use rustc_data_structures::fx::FxIndexMap;
|
|
use rustc_hir as hir;
|
|
use rustc_hir::def::Res;
|
|
use rustc_hir::def_id::LocalDefId;
|
|
use rustc_hir::PatKind;
|
|
use rustc_index::vec::Idx;
|
|
use rustc_infer::infer::InferCtxt;
|
|
use rustc_middle::hir::place::ProjectionKind;
|
|
use rustc_middle::mir::FakeReadCause;
|
|
use rustc_middle::ty::{self, adjustment, AdtKind, Ty, TyCtxt};
|
|
use rustc_target::abi::VariantIdx;
|
|
use ty::BorrowKind::ImmBorrow;
|
|
|
|
use crate::mem_categorization as mc;
|
|
|
|
/// This trait defines the callbacks you can expect to receive when
|
|
/// employing the ExprUseVisitor.
|
|
pub trait Delegate<'tcx> {
|
|
/// The value found at `place` is moved, depending
|
|
/// on `mode`. Where `diag_expr_id` is the id used for diagnostics for `place`.
|
|
///
|
|
/// Use of a `Copy` type in a ByValue context is considered a use
|
|
/// by `ImmBorrow` and `borrow` is called instead. This is because
|
|
/// a shared borrow is the "minimum access" that would be needed
|
|
/// to perform a copy.
|
|
///
|
|
///
|
|
/// The parameter `diag_expr_id` indicates the HIR id that ought to be used for
|
|
/// diagnostics. Around pattern matching such as `let pat = expr`, the diagnostic
|
|
/// id will be the id of the expression `expr` but the place itself will have
|
|
/// the id of the binding in the pattern `pat`.
|
|
fn consume(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId);
|
|
|
|
/// The value found at `place` is being borrowed with kind `bk`.
|
|
/// `diag_expr_id` is the id used for diagnostics (see `consume` for more details).
|
|
fn borrow(
|
|
&mut self,
|
|
place_with_id: &PlaceWithHirId<'tcx>,
|
|
diag_expr_id: hir::HirId,
|
|
bk: ty::BorrowKind,
|
|
);
|
|
|
|
/// The value found at `place` is being copied.
|
|
/// `diag_expr_id` is the id used for diagnostics (see `consume` for more details).
|
|
fn copy(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId) {
|
|
// In most cases, copying data from `x` is equivalent to doing `*&x`, so by default
|
|
// we treat a copy of `x` as a borrow of `x`.
|
|
self.borrow(place_with_id, diag_expr_id, ty::BorrowKind::ImmBorrow)
|
|
}
|
|
|
|
/// The path at `assignee_place` is being assigned to.
|
|
/// `diag_expr_id` is the id used for diagnostics (see `consume` for more details).
|
|
fn mutate(&mut self, assignee_place: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId);
|
|
|
|
/// The path at `binding_place` is a binding that is being initialized.
|
|
///
|
|
/// This covers cases such as `let x = 42;`
|
|
fn bind(&mut self, binding_place: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId) {
|
|
// Bindings can normally be treated as a regular assignment, so by default we
|
|
// forward this to the mutate callback.
|
|
self.mutate(binding_place, diag_expr_id)
|
|
}
|
|
|
|
/// The `place` should be a fake read because of specified `cause`.
|
|
fn fake_read(
|
|
&mut self,
|
|
place_with_id: &PlaceWithHirId<'tcx>,
|
|
cause: FakeReadCause,
|
|
diag_expr_id: hir::HirId,
|
|
);
|
|
}
|
|
|
|
#[derive(Copy, Clone, PartialEq, Debug)]
|
|
enum ConsumeMode {
|
|
/// reference to x where x has a type that copies
|
|
Copy,
|
|
/// reference to x where x has a type that moves
|
|
Move,
|
|
}
|
|
|
|
#[derive(Copy, Clone, PartialEq, Debug)]
|
|
pub enum MutateMode {
|
|
Init,
|
|
/// Example: `x = y`
|
|
JustWrite,
|
|
/// Example: `x += y`
|
|
WriteAndRead,
|
|
}
|
|
|
|
/// The ExprUseVisitor type
|
|
///
|
|
/// This is the code that actually walks the tree.
|
|
pub struct ExprUseVisitor<'a, 'tcx> {
|
|
mc: mc::MemCategorizationContext<'a, 'tcx>,
|
|
body_owner: LocalDefId,
|
|
delegate: &'a mut dyn Delegate<'tcx>,
|
|
}
|
|
|
|
/// If the MC results in an error, it's because the type check
|
|
/// failed (or will fail, when the error is uncovered and reported
|
|
/// during writeback). In this case, we just ignore this part of the
|
|
/// code.
|
|
///
|
|
/// Note that this macro appears similar to try!(), but, unlike try!(),
|
|
/// it does not propagate the error.
|
|
macro_rules! return_if_err {
|
|
($inp: expr) => {
|
|
match $inp {
|
|
Ok(v) => v,
|
|
Err(()) => {
|
|
debug!("mc reported err");
|
|
return;
|
|
}
|
|
}
|
|
};
|
|
}
|
|
|
|
impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
|
|
/// Creates the ExprUseVisitor, configuring it with the various options provided:
|
|
///
|
|
/// - `delegate` -- who receives the callbacks
|
|
/// - `param_env` --- parameter environment for trait lookups (esp. pertaining to `Copy`)
|
|
/// - `typeck_results` --- typeck results for the code being analyzed
|
|
pub fn new(
|
|
delegate: &'a mut (dyn Delegate<'tcx> + 'a),
|
|
infcx: &'a InferCtxt<'tcx>,
|
|
body_owner: LocalDefId,
|
|
param_env: ty::ParamEnv<'tcx>,
|
|
typeck_results: &'a ty::TypeckResults<'tcx>,
|
|
) -> Self {
|
|
ExprUseVisitor {
|
|
mc: mc::MemCategorizationContext::new(infcx, param_env, body_owner, typeck_results),
|
|
body_owner,
|
|
delegate,
|
|
}
|
|
}
|
|
|
|
#[instrument(skip(self), level = "debug")]
|
|
pub fn consume_body(&mut self, body: &hir::Body<'_>) {
|
|
for param in body.params {
|
|
let param_ty = return_if_err!(self.mc.pat_ty_adjusted(param.pat));
|
|
debug!("consume_body: param_ty = {:?}", param_ty);
|
|
|
|
let param_place = self.mc.cat_rvalue(param.hir_id, param.pat.span, param_ty);
|
|
|
|
self.walk_irrefutable_pat(¶m_place, param.pat);
|
|
}
|
|
|
|
self.consume_expr(&body.value);
|
|
}
|
|
|
|
fn tcx(&self) -> TyCtxt<'tcx> {
|
|
self.mc.tcx()
|
|
}
|
|
|
|
fn delegate_consume(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId) {
|
|
delegate_consume(&self.mc, self.delegate, place_with_id, diag_expr_id)
|
|
}
|
|
|
|
fn consume_exprs(&mut self, exprs: &[hir::Expr<'_>]) {
|
|
for expr in exprs {
|
|
self.consume_expr(expr);
|
|
}
|
|
}
|
|
|
|
pub fn consume_expr(&mut self, expr: &hir::Expr<'_>) {
|
|
debug!("consume_expr(expr={:?})", expr);
|
|
|
|
let place_with_id = return_if_err!(self.mc.cat_expr(expr));
|
|
self.delegate_consume(&place_with_id, place_with_id.hir_id);
|
|
self.walk_expr(expr);
|
|
}
|
|
|
|
fn mutate_expr(&mut self, expr: &hir::Expr<'_>) {
|
|
let place_with_id = return_if_err!(self.mc.cat_expr(expr));
|
|
self.delegate.mutate(&place_with_id, place_with_id.hir_id);
|
|
self.walk_expr(expr);
|
|
}
|
|
|
|
fn borrow_expr(&mut self, expr: &hir::Expr<'_>, bk: ty::BorrowKind) {
|
|
debug!("borrow_expr(expr={:?}, bk={:?})", expr, bk);
|
|
|
|
let place_with_id = return_if_err!(self.mc.cat_expr(expr));
|
|
self.delegate.borrow(&place_with_id, place_with_id.hir_id, bk);
|
|
|
|
self.walk_expr(expr)
|
|
}
|
|
|
|
fn select_from_expr(&mut self, expr: &hir::Expr<'_>) {
|
|
self.walk_expr(expr)
|
|
}
|
|
|
|
pub fn walk_expr(&mut self, expr: &hir::Expr<'_>) {
|
|
debug!("walk_expr(expr={:?})", expr);
|
|
|
|
self.walk_adjustment(expr);
|
|
|
|
match expr.kind {
|
|
hir::ExprKind::Path(_) => {}
|
|
|
|
hir::ExprKind::Type(subexpr, _) => self.walk_expr(subexpr),
|
|
|
|
hir::ExprKind::Unary(hir::UnOp::Deref, base) => {
|
|
// *base
|
|
self.select_from_expr(base);
|
|
}
|
|
|
|
hir::ExprKind::Field(base, _) => {
|
|
// base.f
|
|
self.select_from_expr(base);
|
|
}
|
|
|
|
hir::ExprKind::Index(lhs, rhs) => {
|
|
// lhs[rhs]
|
|
self.select_from_expr(lhs);
|
|
self.consume_expr(rhs);
|
|
}
|
|
|
|
hir::ExprKind::Call(callee, args) => {
|
|
// callee(args)
|
|
self.consume_expr(callee);
|
|
self.consume_exprs(args);
|
|
}
|
|
|
|
hir::ExprKind::MethodCall(.., receiver, args, _) => {
|
|
// callee.m(args)
|
|
self.consume_expr(receiver);
|
|
self.consume_exprs(args);
|
|
}
|
|
|
|
hir::ExprKind::Struct(_, fields, ref opt_with) => {
|
|
self.walk_struct_expr(fields, opt_with);
|
|
}
|
|
|
|
hir::ExprKind::Tup(exprs) => {
|
|
self.consume_exprs(exprs);
|
|
}
|
|
|
|
hir::ExprKind::If(ref cond_expr, ref then_expr, ref opt_else_expr) => {
|
|
self.consume_expr(cond_expr);
|
|
self.consume_expr(then_expr);
|
|
if let Some(ref else_expr) = *opt_else_expr {
|
|
self.consume_expr(else_expr);
|
|
}
|
|
}
|
|
|
|
hir::ExprKind::Let(hir::Let { pat, init, .. }) => {
|
|
self.walk_local(init, pat, None, |t| t.borrow_expr(init, ty::ImmBorrow))
|
|
}
|
|
|
|
hir::ExprKind::Match(ref discr, arms, _) => {
|
|
let discr_place = return_if_err!(self.mc.cat_expr(discr));
|
|
self.maybe_read_scrutinee(
|
|
discr,
|
|
discr_place.clone(),
|
|
arms.iter().map(|arm| arm.pat),
|
|
);
|
|
|
|
// treatment of the discriminant is handled while walking the arms.
|
|
for arm in arms {
|
|
self.walk_arm(&discr_place, arm);
|
|
}
|
|
}
|
|
|
|
hir::ExprKind::Array(exprs) => {
|
|
self.consume_exprs(exprs);
|
|
}
|
|
|
|
hir::ExprKind::AddrOf(_, m, ref base) => {
|
|
// &base
|
|
// make sure that the thing we are pointing out stays valid
|
|
// for the lifetime `scope_r` of the resulting ptr:
|
|
let bk = ty::BorrowKind::from_mutbl(m);
|
|
self.borrow_expr(base, bk);
|
|
}
|
|
|
|
hir::ExprKind::InlineAsm(asm) => {
|
|
for (op, _op_sp) in asm.operands {
|
|
match op {
|
|
hir::InlineAsmOperand::In { expr, .. } => self.consume_expr(expr),
|
|
hir::InlineAsmOperand::Out { expr: Some(expr), .. }
|
|
| hir::InlineAsmOperand::InOut { expr, .. } => {
|
|
self.mutate_expr(expr);
|
|
}
|
|
hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
|
|
self.consume_expr(in_expr);
|
|
if let Some(out_expr) = out_expr {
|
|
self.mutate_expr(out_expr);
|
|
}
|
|
}
|
|
hir::InlineAsmOperand::Out { expr: None, .. }
|
|
| hir::InlineAsmOperand::Const { .. }
|
|
| hir::InlineAsmOperand::SymFn { .. }
|
|
| hir::InlineAsmOperand::SymStatic { .. } => {}
|
|
}
|
|
}
|
|
}
|
|
|
|
hir::ExprKind::Continue(..)
|
|
| hir::ExprKind::Lit(..)
|
|
| hir::ExprKind::ConstBlock(..)
|
|
| hir::ExprKind::Err => {}
|
|
|
|
hir::ExprKind::Loop(blk, ..) => {
|
|
self.walk_block(blk);
|
|
}
|
|
|
|
hir::ExprKind::Unary(_, lhs) => {
|
|
self.consume_expr(lhs);
|
|
}
|
|
|
|
hir::ExprKind::Binary(_, lhs, rhs) => {
|
|
self.consume_expr(lhs);
|
|
self.consume_expr(rhs);
|
|
}
|
|
|
|
hir::ExprKind::Block(blk, _) => {
|
|
self.walk_block(blk);
|
|
}
|
|
|
|
hir::ExprKind::Break(_, ref opt_expr) | hir::ExprKind::Ret(ref opt_expr) => {
|
|
if let Some(expr) = *opt_expr {
|
|
self.consume_expr(expr);
|
|
}
|
|
}
|
|
|
|
hir::ExprKind::Assign(lhs, rhs, _) => {
|
|
self.mutate_expr(lhs);
|
|
self.consume_expr(rhs);
|
|
}
|
|
|
|
hir::ExprKind::Cast(base, _) => {
|
|
self.consume_expr(base);
|
|
}
|
|
|
|
hir::ExprKind::DropTemps(expr) => {
|
|
self.consume_expr(expr);
|
|
}
|
|
|
|
hir::ExprKind::AssignOp(_, lhs, rhs) => {
|
|
if self.mc.typeck_results.is_method_call(expr) {
|
|
self.consume_expr(lhs);
|
|
} else {
|
|
self.mutate_expr(lhs);
|
|
}
|
|
self.consume_expr(rhs);
|
|
}
|
|
|
|
hir::ExprKind::Repeat(base, _) => {
|
|
self.consume_expr(base);
|
|
}
|
|
|
|
hir::ExprKind::Closure { .. } => {
|
|
self.walk_captures(expr);
|
|
}
|
|
|
|
hir::ExprKind::Box(ref base) => {
|
|
self.consume_expr(base);
|
|
}
|
|
|
|
hir::ExprKind::Yield(value, _) => {
|
|
self.consume_expr(value);
|
|
}
|
|
}
|
|
}
|
|
|
|
fn walk_stmt(&mut self, stmt: &hir::Stmt<'_>) {
|
|
match stmt.kind {
|
|
hir::StmtKind::Local(hir::Local { pat, init: Some(expr), els, .. }) => {
|
|
self.walk_local(expr, pat, *els, |_| {})
|
|
}
|
|
|
|
hir::StmtKind::Local(_) => {}
|
|
|
|
hir::StmtKind::Item(_) => {
|
|
// We don't visit nested items in this visitor,
|
|
// only the fn body we were given.
|
|
}
|
|
|
|
hir::StmtKind::Expr(ref expr) | hir::StmtKind::Semi(ref expr) => {
|
|
self.consume_expr(expr);
|
|
}
|
|
}
|
|
}
|
|
|
|
fn maybe_read_scrutinee<'t>(
|
|
&mut self,
|
|
discr: &Expr<'_>,
|
|
discr_place: PlaceWithHirId<'tcx>,
|
|
pats: impl Iterator<Item = &'t hir::Pat<'t>>,
|
|
) {
|
|
// Matching should not always be considered a use of the place, hence
|
|
// discr does not necessarily need to be borrowed.
|
|
// We only want to borrow discr if the pattern contain something other
|
|
// than wildcards.
|
|
let ExprUseVisitor { ref mc, body_owner: _, delegate: _ } = *self;
|
|
let mut needs_to_be_read = false;
|
|
for pat in pats {
|
|
return_if_err!(mc.cat_pattern(discr_place.clone(), pat, |place, pat| {
|
|
match &pat.kind {
|
|
PatKind::Binding(.., opt_sub_pat) => {
|
|
// If the opt_sub_pat is None, than the binding does not count as
|
|
// a wildcard for the purpose of borrowing discr.
|
|
if opt_sub_pat.is_none() {
|
|
needs_to_be_read = true;
|
|
}
|
|
}
|
|
PatKind::Path(qpath) => {
|
|
// A `Path` pattern is just a name like `Foo`. This is either a
|
|
// named constant or else it refers to an ADT variant
|
|
|
|
let res = self.mc.typeck_results.qpath_res(qpath, pat.hir_id);
|
|
match res {
|
|
Res::Def(DefKind::Const, _) | Res::Def(DefKind::AssocConst, _) => {
|
|
// Named constants have to be equated with the value
|
|
// being matched, so that's a read of the value being matched.
|
|
//
|
|
// FIXME: We don't actually reads for ZSTs.
|
|
needs_to_be_read = true;
|
|
}
|
|
_ => {
|
|
// Otherwise, this is a struct/enum variant, and so it's
|
|
// only a read if we need to read the discriminant.
|
|
needs_to_be_read |= is_multivariant_adt(place.place.ty());
|
|
}
|
|
}
|
|
}
|
|
PatKind::TupleStruct(..) | PatKind::Struct(..) | PatKind::Tuple(..) => {
|
|
// For `Foo(..)`, `Foo { ... }` and `(...)` patterns, check if we are matching
|
|
// against a multivariant enum or struct. In that case, we have to read
|
|
// the discriminant. Otherwise this kind of pattern doesn't actually
|
|
// read anything (we'll get invoked for the `...`, which may indeed
|
|
// perform some reads).
|
|
|
|
let place_ty = place.place.ty();
|
|
needs_to_be_read |= is_multivariant_adt(place_ty);
|
|
}
|
|
PatKind::Lit(_) | PatKind::Range(..) => {
|
|
// If the PatKind is a Lit or a Range then we want
|
|
// to borrow discr.
|
|
needs_to_be_read = true;
|
|
}
|
|
PatKind::Or(_)
|
|
| PatKind::Box(_)
|
|
| PatKind::Slice(..)
|
|
| PatKind::Ref(..)
|
|
| PatKind::Wild => {
|
|
// If the PatKind is Or, Box, Slice or Ref, the decision is made later
|
|
// as these patterns contains subpatterns
|
|
// If the PatKind is Wild, the decision is made based on the other patterns being
|
|
// examined
|
|
}
|
|
}
|
|
}));
|
|
}
|
|
|
|
if needs_to_be_read {
|
|
self.borrow_expr(discr, ty::ImmBorrow);
|
|
} else {
|
|
let closure_def_id = match discr_place.place.base {
|
|
PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id),
|
|
_ => None,
|
|
};
|
|
|
|
self.delegate.fake_read(
|
|
&discr_place,
|
|
FakeReadCause::ForMatchedPlace(closure_def_id),
|
|
discr_place.hir_id,
|
|
);
|
|
|
|
// We always want to walk the discriminant. We want to make sure, for instance,
|
|
// that the discriminant has been initialized.
|
|
self.walk_expr(discr);
|
|
}
|
|
}
|
|
|
|
fn walk_local<F>(
|
|
&mut self,
|
|
expr: &hir::Expr<'_>,
|
|
pat: &hir::Pat<'_>,
|
|
els: Option<&hir::Block<'_>>,
|
|
mut f: F,
|
|
) where
|
|
F: FnMut(&mut Self),
|
|
{
|
|
self.walk_expr(expr);
|
|
let expr_place = return_if_err!(self.mc.cat_expr(expr));
|
|
f(self);
|
|
if let Some(els) = els {
|
|
// borrowing because we need to test the discriminant
|
|
self.maybe_read_scrutinee(expr, expr_place.clone(), from_ref(pat).iter());
|
|
self.walk_block(els)
|
|
}
|
|
self.walk_irrefutable_pat(&expr_place, &pat);
|
|
}
|
|
|
|
/// Indicates that the value of `blk` will be consumed, meaning either copied or moved
|
|
/// depending on its type.
|
|
fn walk_block(&mut self, blk: &hir::Block<'_>) {
|
|
debug!("walk_block(blk.hir_id={})", blk.hir_id);
|
|
|
|
for stmt in blk.stmts {
|
|
self.walk_stmt(stmt);
|
|
}
|
|
|
|
if let Some(ref tail_expr) = blk.expr {
|
|
self.consume_expr(tail_expr);
|
|
}
|
|
}
|
|
|
|
fn walk_struct_expr<'hir>(
|
|
&mut self,
|
|
fields: &[hir::ExprField<'_>],
|
|
opt_with: &Option<&'hir hir::Expr<'_>>,
|
|
) {
|
|
// Consume the expressions supplying values for each field.
|
|
for field in fields {
|
|
self.consume_expr(field.expr);
|
|
}
|
|
|
|
let with_expr = match *opt_with {
|
|
Some(w) => &*w,
|
|
None => {
|
|
return;
|
|
}
|
|
};
|
|
|
|
let with_place = return_if_err!(self.mc.cat_expr(with_expr));
|
|
|
|
// Select just those fields of the `with`
|
|
// expression that will actually be used
|
|
match with_place.place.ty().kind() {
|
|
ty::Adt(adt, substs) if adt.is_struct() => {
|
|
// Consume those fields of the with expression that are needed.
|
|
for (f_index, with_field) in adt.non_enum_variant().fields.iter().enumerate() {
|
|
let is_mentioned = fields.iter().any(|f| {
|
|
self.tcx().field_index(f.hir_id, self.mc.typeck_results) == f_index
|
|
});
|
|
if !is_mentioned {
|
|
let field_place = self.mc.cat_projection(
|
|
&*with_expr,
|
|
with_place.clone(),
|
|
with_field.ty(self.tcx(), substs),
|
|
ProjectionKind::Field(f_index as u32, VariantIdx::new(0)),
|
|
);
|
|
self.delegate_consume(&field_place, field_place.hir_id);
|
|
}
|
|
}
|
|
}
|
|
_ => {
|
|
// the base expression should always evaluate to a
|
|
// struct; however, when EUV is run during typeck, it
|
|
// may not. This will generate an error earlier in typeck,
|
|
// so we can just ignore it.
|
|
if !self.tcx().sess.has_errors().is_some() {
|
|
span_bug!(with_expr.span, "with expression doesn't evaluate to a struct");
|
|
}
|
|
}
|
|
}
|
|
|
|
// walk the with expression so that complex expressions
|
|
// are properly handled.
|
|
self.walk_expr(with_expr);
|
|
}
|
|
|
|
/// Invoke the appropriate delegate calls for anything that gets
|
|
/// consumed or borrowed as part of the automatic adjustment
|
|
/// process.
|
|
fn walk_adjustment(&mut self, expr: &hir::Expr<'_>) {
|
|
let adjustments = self.mc.typeck_results.expr_adjustments(expr);
|
|
let mut place_with_id = return_if_err!(self.mc.cat_expr_unadjusted(expr));
|
|
for adjustment in adjustments {
|
|
debug!("walk_adjustment expr={:?} adj={:?}", expr, adjustment);
|
|
match adjustment.kind {
|
|
adjustment::Adjust::NeverToAny
|
|
| adjustment::Adjust::Pointer(_)
|
|
| adjustment::Adjust::DynStar => {
|
|
// Creating a closure/fn-pointer or unsizing consumes
|
|
// the input and stores it into the resulting rvalue.
|
|
self.delegate_consume(&place_with_id, place_with_id.hir_id);
|
|
}
|
|
|
|
adjustment::Adjust::Deref(None) => {}
|
|
|
|
// Autoderefs for overloaded Deref calls in fact reference
|
|
// their receiver. That is, if we have `(*x)` where `x`
|
|
// is of type `Rc<T>`, then this in fact is equivalent to
|
|
// `x.deref()`. Since `deref()` is declared with `&self`,
|
|
// this is an autoref of `x`.
|
|
adjustment::Adjust::Deref(Some(ref deref)) => {
|
|
let bk = ty::BorrowKind::from_mutbl(deref.mutbl);
|
|
self.delegate.borrow(&place_with_id, place_with_id.hir_id, bk);
|
|
}
|
|
|
|
adjustment::Adjust::Borrow(ref autoref) => {
|
|
self.walk_autoref(expr, &place_with_id, autoref);
|
|
}
|
|
}
|
|
place_with_id =
|
|
return_if_err!(self.mc.cat_expr_adjusted(expr, place_with_id, adjustment));
|
|
}
|
|
}
|
|
|
|
/// Walks the autoref `autoref` applied to the autoderef'd
|
|
/// `expr`. `base_place` is the mem-categorized form of `expr`
|
|
/// after all relevant autoderefs have occurred.
|
|
fn walk_autoref(
|
|
&mut self,
|
|
expr: &hir::Expr<'_>,
|
|
base_place: &PlaceWithHirId<'tcx>,
|
|
autoref: &adjustment::AutoBorrow<'tcx>,
|
|
) {
|
|
debug!(
|
|
"walk_autoref(expr.hir_id={} base_place={:?} autoref={:?})",
|
|
expr.hir_id, base_place, autoref
|
|
);
|
|
|
|
match *autoref {
|
|
adjustment::AutoBorrow::Ref(_, m) => {
|
|
self.delegate.borrow(
|
|
base_place,
|
|
base_place.hir_id,
|
|
ty::BorrowKind::from_mutbl(m.into()),
|
|
);
|
|
}
|
|
|
|
adjustment::AutoBorrow::RawPtr(m) => {
|
|
debug!("walk_autoref: expr.hir_id={} base_place={:?}", expr.hir_id, base_place);
|
|
|
|
self.delegate.borrow(base_place, base_place.hir_id, ty::BorrowKind::from_mutbl(m));
|
|
}
|
|
}
|
|
}
|
|
|
|
fn walk_arm(&mut self, discr_place: &PlaceWithHirId<'tcx>, arm: &hir::Arm<'_>) {
|
|
let closure_def_id = match discr_place.place.base {
|
|
PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id),
|
|
_ => None,
|
|
};
|
|
|
|
self.delegate.fake_read(
|
|
discr_place,
|
|
FakeReadCause::ForMatchedPlace(closure_def_id),
|
|
discr_place.hir_id,
|
|
);
|
|
self.walk_pat(discr_place, arm.pat, arm.guard.is_some());
|
|
|
|
if let Some(hir::Guard::If(e)) = arm.guard {
|
|
self.consume_expr(e)
|
|
} else if let Some(hir::Guard::IfLet(ref l)) = arm.guard {
|
|
self.consume_expr(l.init)
|
|
}
|
|
|
|
self.consume_expr(arm.body);
|
|
}
|
|
|
|
/// Walks a pat that occurs in isolation (i.e., top-level of fn argument or
|
|
/// let binding, and *not* a match arm or nested pat.)
|
|
fn walk_irrefutable_pat(&mut self, discr_place: &PlaceWithHirId<'tcx>, pat: &hir::Pat<'_>) {
|
|
let closure_def_id = match discr_place.place.base {
|
|
PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id),
|
|
_ => None,
|
|
};
|
|
|
|
self.delegate.fake_read(
|
|
discr_place,
|
|
FakeReadCause::ForLet(closure_def_id),
|
|
discr_place.hir_id,
|
|
);
|
|
self.walk_pat(discr_place, pat, false);
|
|
}
|
|
|
|
/// The core driver for walking a pattern
|
|
fn walk_pat(
|
|
&mut self,
|
|
discr_place: &PlaceWithHirId<'tcx>,
|
|
pat: &hir::Pat<'_>,
|
|
has_guard: bool,
|
|
) {
|
|
debug!("walk_pat(discr_place={:?}, pat={:?}, has_guard={:?})", discr_place, pat, has_guard);
|
|
|
|
let tcx = self.tcx();
|
|
let ExprUseVisitor { ref mc, body_owner: _, ref mut delegate } = *self;
|
|
return_if_err!(mc.cat_pattern(discr_place.clone(), pat, |place, pat| {
|
|
if let PatKind::Binding(_, canonical_id, ..) = pat.kind {
|
|
debug!("walk_pat: binding place={:?} pat={:?}", place, pat);
|
|
if let Some(bm) =
|
|
mc.typeck_results.extract_binding_mode(tcx.sess, pat.hir_id, pat.span)
|
|
{
|
|
debug!("walk_pat: pat.hir_id={:?} bm={:?}", pat.hir_id, bm);
|
|
|
|
// pat_ty: the type of the binding being produced.
|
|
let pat_ty = return_if_err!(mc.node_ty(pat.hir_id));
|
|
debug!("walk_pat: pat_ty={:?}", pat_ty);
|
|
|
|
let def = Res::Local(canonical_id);
|
|
if let Ok(ref binding_place) = mc.cat_res(pat.hir_id, pat.span, pat_ty, def) {
|
|
delegate.bind(binding_place, binding_place.hir_id);
|
|
}
|
|
|
|
// Subtle: MIR desugaring introduces immutable borrows for each pattern
|
|
// binding when lowering pattern guards to ensure that the guard does not
|
|
// modify the scrutinee.
|
|
if has_guard {
|
|
delegate.borrow(place, discr_place.hir_id, ImmBorrow);
|
|
}
|
|
|
|
// It is also a borrow or copy/move of the value being matched.
|
|
// In a cases of pattern like `let pat = upvar`, don't use the span
|
|
// of the pattern, as this just looks confusing, instead use the span
|
|
// of the discriminant.
|
|
match bm {
|
|
ty::BindByReference(m) => {
|
|
let bk = ty::BorrowKind::from_mutbl(m);
|
|
delegate.borrow(place, discr_place.hir_id, bk);
|
|
}
|
|
ty::BindByValue(..) => {
|
|
debug!("walk_pat binding consuming pat");
|
|
delegate_consume(mc, *delegate, place, discr_place.hir_id);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}));
|
|
}
|
|
|
|
/// Handle the case where the current body contains a closure.
|
|
///
|
|
/// When the current body being handled is a closure, then we must make sure that
|
|
/// - The parent closure only captures Places from the nested closure that are not local to it.
|
|
///
|
|
/// In the following example the closures `c` only captures `p.x` even though `incr`
|
|
/// is a capture of the nested closure
|
|
///
|
|
/// ```
|
|
/// struct P { x: i32 }
|
|
/// let mut p = P { x: 4 };
|
|
/// let c = || {
|
|
/// let incr = 10;
|
|
/// let nested = || p.x += incr;
|
|
/// };
|
|
/// ```
|
|
///
|
|
/// - When reporting the Place back to the Delegate, ensure that the UpvarId uses the enclosing
|
|
/// closure as the DefId.
|
|
fn walk_captures(&mut self, closure_expr: &hir::Expr<'_>) {
|
|
fn upvar_is_local_variable<'tcx>(
|
|
upvars: Option<&'tcx FxIndexMap<hir::HirId, hir::Upvar>>,
|
|
upvar_id: hir::HirId,
|
|
body_owner_is_closure: bool,
|
|
) -> bool {
|
|
upvars.map(|upvars| !upvars.contains_key(&upvar_id)).unwrap_or(body_owner_is_closure)
|
|
}
|
|
|
|
debug!("walk_captures({:?})", closure_expr);
|
|
|
|
let tcx = self.tcx();
|
|
let closure_def_id = tcx.hir().local_def_id(closure_expr.hir_id);
|
|
let upvars = tcx.upvars_mentioned(self.body_owner);
|
|
|
|
// For purposes of this function, generator and closures are equivalent.
|
|
let body_owner_is_closure =
|
|
matches!(tcx.hir().body_owner_kind(self.body_owner), hir::BodyOwnerKind::Closure,);
|
|
|
|
// If we have a nested closure, we want to include the fake reads present in the nested closure.
|
|
if let Some(fake_reads) = self.mc.typeck_results.closure_fake_reads.get(&closure_def_id) {
|
|
for (fake_read, cause, hir_id) in fake_reads.iter() {
|
|
match fake_read.base {
|
|
PlaceBase::Upvar(upvar_id) => {
|
|
if upvar_is_local_variable(
|
|
upvars,
|
|
upvar_id.var_path.hir_id,
|
|
body_owner_is_closure,
|
|
) {
|
|
// The nested closure might be fake reading the current (enclosing) closure's local variables.
|
|
// The only places we want to fake read before creating the parent closure are the ones that
|
|
// are not local to it/ defined by it.
|
|
//
|
|
// ```rust,ignore(cannot-test-this-because-pseudo-code)
|
|
// let v1 = (0, 1);
|
|
// let c = || { // fake reads: v1
|
|
// let v2 = (0, 1);
|
|
// let e = || { // fake reads: v1, v2
|
|
// let (_, t1) = v1;
|
|
// let (_, t2) = v2;
|
|
// }
|
|
// }
|
|
// ```
|
|
// This check is performed when visiting the body of the outermost closure (`c`) and ensures
|
|
// that we don't add a fake read of v2 in c.
|
|
continue;
|
|
}
|
|
}
|
|
_ => {
|
|
bug!(
|
|
"Do not know how to get HirId out of Rvalue and StaticItem {:?}",
|
|
fake_read.base
|
|
);
|
|
}
|
|
};
|
|
self.delegate.fake_read(
|
|
&PlaceWithHirId { place: fake_read.clone(), hir_id: *hir_id },
|
|
*cause,
|
|
*hir_id,
|
|
);
|
|
}
|
|
}
|
|
|
|
if let Some(min_captures) = self.mc.typeck_results.closure_min_captures.get(&closure_def_id)
|
|
{
|
|
for (var_hir_id, min_list) in min_captures.iter() {
|
|
if upvars.map_or(body_owner_is_closure, |upvars| !upvars.contains_key(var_hir_id)) {
|
|
// The nested closure might be capturing the current (enclosing) closure's local variables.
|
|
// We check if the root variable is ever mentioned within the enclosing closure, if not
|
|
// then for the current body (if it's a closure) these aren't captures, we will ignore them.
|
|
continue;
|
|
}
|
|
for captured_place in min_list {
|
|
let place = &captured_place.place;
|
|
let capture_info = captured_place.info;
|
|
|
|
let place_base = if body_owner_is_closure {
|
|
// Mark the place to be captured by the enclosing closure
|
|
PlaceBase::Upvar(ty::UpvarId::new(*var_hir_id, self.body_owner))
|
|
} else {
|
|
// If the body owner isn't a closure then the variable must
|
|
// be a local variable
|
|
PlaceBase::Local(*var_hir_id)
|
|
};
|
|
let place_with_id = PlaceWithHirId::new(
|
|
capture_info.path_expr_id.unwrap_or(
|
|
capture_info.capture_kind_expr_id.unwrap_or(closure_expr.hir_id),
|
|
),
|
|
place.base_ty,
|
|
place_base,
|
|
place.projections.clone(),
|
|
);
|
|
|
|
match capture_info.capture_kind {
|
|
ty::UpvarCapture::ByValue => {
|
|
self.delegate_consume(&place_with_id, place_with_id.hir_id);
|
|
}
|
|
ty::UpvarCapture::ByRef(upvar_borrow) => {
|
|
self.delegate.borrow(
|
|
&place_with_id,
|
|
place_with_id.hir_id,
|
|
upvar_borrow,
|
|
);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn copy_or_move<'a, 'tcx>(
|
|
mc: &mc::MemCategorizationContext<'a, 'tcx>,
|
|
place_with_id: &PlaceWithHirId<'tcx>,
|
|
) -> ConsumeMode {
|
|
if !mc.type_is_copy_modulo_regions(
|
|
place_with_id.place.ty(),
|
|
mc.tcx().hir().span(place_with_id.hir_id),
|
|
) {
|
|
ConsumeMode::Move
|
|
} else {
|
|
ConsumeMode::Copy
|
|
}
|
|
}
|
|
|
|
// - If a place is used in a `ByValue` context then move it if it's not a `Copy` type.
|
|
// - If the place that is a `Copy` type consider it an `ImmBorrow`.
|
|
fn delegate_consume<'a, 'tcx>(
|
|
mc: &mc::MemCategorizationContext<'a, 'tcx>,
|
|
delegate: &mut (dyn Delegate<'tcx> + 'a),
|
|
place_with_id: &PlaceWithHirId<'tcx>,
|
|
diag_expr_id: hir::HirId,
|
|
) {
|
|
debug!("delegate_consume(place_with_id={:?})", place_with_id);
|
|
|
|
let mode = copy_or_move(mc, place_with_id);
|
|
|
|
match mode {
|
|
ConsumeMode::Move => delegate.consume(place_with_id, diag_expr_id),
|
|
ConsumeMode::Copy => delegate.copy(place_with_id, diag_expr_id),
|
|
}
|
|
}
|
|
|
|
fn is_multivariant_adt(ty: Ty<'_>) -> bool {
|
|
if let ty::Adt(def, _) = ty.kind() {
|
|
// Note that if a non-exhaustive SingleVariant is defined in another crate, we need
|
|
// to assume that more cases will be added to the variant in the future. This mean
|
|
// that we should handle non-exhaustive SingleVariant the same way we would handle
|
|
// a MultiVariant.
|
|
// If the variant is not local it must be defined in another crate.
|
|
let is_non_exhaustive = match def.adt_kind() {
|
|
AdtKind::Struct | AdtKind::Union => {
|
|
def.non_enum_variant().is_field_list_non_exhaustive()
|
|
}
|
|
AdtKind::Enum => def.is_variant_list_non_exhaustive(),
|
|
};
|
|
def.variants().len() > 1 || (!def.did().is_local() && is_non_exhaustive)
|
|
} else {
|
|
false
|
|
}
|
|
}
|