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Auto merge of #9386 - smoelius:further-enhance-needless-borrow, r=Jarcho

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Further enhance `needless_borrow`, mildly refactor `redundant_clone`

This PR does the following:
* Moves some code from `redundant_clone` into a new `clippy_utils` module called `mir`, and wraps that code in a function called `dropped_without_further_use`.
* Relaxes the "is copyable" condition condition from #9136 by also suggesting to remove borrows from values dropped without further use. The changes involve the just mentioned function.
* Separates `redundant_clone` into modules.

Strictly speaking, the last bullet is independent of the others. `redundant_clone` is somewhat hairy, IMO. Separating it into modules makes it slightly less so, by helping to delineate what depends upon what.

I've tried to break everything up into digestible commits.

r? `@Jarcho`

(`@Jarcho` I hope you don't mind.)

changelog: continuation of #9136
This commit is contained in:
bors 2022-10-08 21:24:54 +00:00
commit 272bbfb857
22 changed files with 879 additions and 504 deletions
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99
clippy_lints/src/dereference.rs
View file

@ -1,4 +1,5 @@
use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_hir_and_then};
use clippy_utils::mir::{enclosing_mir, expr_local, local_assignments, used_exactly_once, PossibleBorrowerMap};
use clippy_utils::source::{snippet_with_applicability, snippet_with_context};
use clippy_utils::sugg::has_enclosing_paren;
use clippy_utils::ty::{expr_sig, is_copy, peel_mid_ty_refs, ty_sig, variant_of_res};
@ -11,13 +12,16 @@ use rustc_data_structures::fx::FxIndexMap;
use rustc_errors::Applicability;
use rustc_hir::intravisit::{walk_ty, Visitor};
use rustc_hir::{
self as hir, def_id::DefId, BindingAnnotation, Body, BodyId, BorrowKind, Closure, Expr, ExprKind, FnRetTy,
GenericArg, HirId, ImplItem, ImplItemKind, Item, ItemKind, Local, MatchSource, Mutability, Node, Pat, PatKind,
Path, QPath, TraitItem, TraitItemKind, TyKind, UnOp,
self as hir,
def_id::{DefId, LocalDefId},
BindingAnnotation, Body, BodyId, BorrowKind, Closure, Expr, ExprKind, FnRetTy, GenericArg, HirId, ImplItem,
ImplItemKind, Item, ItemKind, Local, MatchSource, Mutability, Node, Pat, PatKind, Path, QPath, TraitItem,
TraitItemKind, TyKind, UnOp,
};
use rustc_index::bit_set::BitSet;
use rustc_infer::infer::TyCtxtInferExt;
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::mir::{Rvalue, StatementKind};
use rustc_middle::ty::adjustment::{Adjust, Adjustment, AutoBorrow, AutoBorrowMutability};
use rustc_middle::ty::{
self, Binder, BoundVariableKind, EarlyBinder, FnSig, GenericArgKind, List, ParamTy, PredicateKind,
@ -141,7 +145,7 @@ declare_clippy_lint! {
"dereferencing when the compiler would automatically dereference"
}
impl_lint_pass!(Dereferencing => [
impl_lint_pass!(Dereferencing<'_> => [
EXPLICIT_DEREF_METHODS,
NEEDLESS_BORROW,
REF_BINDING_TO_REFERENCE,
@ -149,7 +153,7 @@ impl_lint_pass!(Dereferencing => [
]);
#[derive(Default)]
pub struct Dereferencing {
pub struct Dereferencing<'tcx> {
state: Option<(State, StateData)>,
// While parsing a `deref` method call in ufcs form, the path to the function is itself an
@ -170,11 +174,16 @@ pub struct Dereferencing {
/// e.g. `m!(x) | Foo::Bar(ref x)`
ref_locals: FxIndexMap<HirId, Option<RefPat>>,
/// Stack of (body owner, `PossibleBorrowerMap`) pairs. Used by
/// `needless_borrow_impl_arg_position` to determine when a borrowed expression can instead
/// be moved.
possible_borrowers: Vec<(LocalDefId, PossibleBorrowerMap<'tcx, 'tcx>)>,
// `IntoIterator` for arrays requires Rust 1.53.
msrv: Option<RustcVersion>,
}
impl Dereferencing {
impl<'tcx> Dereferencing<'tcx> {
#[must_use]
pub fn new(msrv: Option<RustcVersion>) -> Self {
Self {
@ -244,7 +253,7 @@ struct RefPat {
hir_id: HirId,
}
impl<'tcx> LateLintPass<'tcx> for Dereferencing {
impl<'tcx> LateLintPass<'tcx> for Dereferencing<'tcx> {
#[expect(clippy::too_many_lines)]
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
// Skip path expressions from deref calls. e.g. `Deref::deref(e)`
@ -278,7 +287,7 @@ impl<'tcx> LateLintPass<'tcx> for Dereferencing {
match (self.state.take(), kind) {
(None, kind) => {
let expr_ty = typeck.expr_ty(expr);
let (position, adjustments) = walk_parents(cx, expr, self.msrv);
let (position, adjustments) = walk_parents(cx, &mut self.possible_borrowers, expr, self.msrv);
match kind {
RefOp::Deref => {
if let Position::FieldAccess {
@ -550,6 +559,12 @@ impl<'tcx> LateLintPass<'tcx> for Dereferencing {
}
fn check_body_post(&mut self, cx: &LateContext<'tcx>, body: &'tcx Body<'_>) {
if self.possible_borrowers.last().map_or(false, |&(local_def_id, _)| {
local_def_id == cx.tcx.hir().body_owner_def_id(body.id())
}) {
self.possible_borrowers.pop();
}
if Some(body.id()) == self.current_body {
for pat in self.ref_locals.drain(..).filter_map(|(_, x)| x) {
let replacements = pat.replacements;
@ -682,6 +697,7 @@ impl Position {
#[expect(clippy::too_many_lines)]
fn walk_parents<'tcx>(
cx: &LateContext<'tcx>,
possible_borrowers: &mut Vec<(LocalDefId, PossibleBorrowerMap<'tcx, 'tcx>)>,
e: &'tcx Expr<'_>,
msrv: Option<RustcVersion>,
) -> (Position, &'tcx [Adjustment<'tcx>]) {
@ -796,7 +812,16 @@ fn walk_parents<'tcx>(
Some(hir_ty) => binding_ty_auto_deref_stability(cx, hir_ty, precedence, ty.bound_vars()),
None => {
if let ty::Param(param_ty) = ty.skip_binder().kind() {
needless_borrow_impl_arg_position(cx, parent, i, *param_ty, e, precedence, msrv)
needless_borrow_impl_arg_position(
cx,
possible_borrowers,
parent,
i,
*param_ty,
e,
precedence,
msrv,
)
} else {
ty_auto_deref_stability(cx, cx.tcx.erase_late_bound_regions(ty), precedence)
.position_for_arg()
@ -844,7 +869,16 @@ fn walk_parents<'tcx>(
args.iter().position(|arg| arg.hir_id == child_id).map(|i| {
let ty = cx.tcx.fn_sig(id).skip_binder().inputs()[i + 1];
if let ty::Param(param_ty) = ty.kind() {
needless_borrow_impl_arg_position(cx, parent, i + 1, *param_ty, e, precedence, msrv)
needless_borrow_impl_arg_position(
cx,
possible_borrowers,
parent,
i + 1,
*param_ty,
e,
precedence,
msrv,
)
} else {
ty_auto_deref_stability(
cx,
@ -1018,8 +1052,10 @@ fn ty_contains_infer(ty: &hir::Ty<'_>) -> bool {
// If the conditions are met, returns `Some(Position::ImplArg(..))`; otherwise, returns `None`.
// The "is copyable" condition is to avoid the case where removing the `&` means `e` would have to
// be moved, but it cannot be.
#[expect(clippy::too_many_arguments)]
fn needless_borrow_impl_arg_position<'tcx>(
cx: &LateContext<'tcx>,
possible_borrowers: &mut Vec<(LocalDefId, PossibleBorrowerMap<'tcx, 'tcx>)>,
parent: &Expr<'tcx>,
arg_index: usize,
param_ty: ParamTy,
@ -1082,10 +1118,13 @@ fn needless_borrow_impl_arg_position<'tcx>(
// elements are modified each time `check_referent` is called.
let mut substs_with_referent_ty = substs_with_expr_ty.to_vec();
let mut check_referent = |referent| {
let mut check_reference_and_referent = |reference, referent| {
let referent_ty = cx.typeck_results().expr_ty(referent);
if !is_copy(cx, referent_ty) {
if !is_copy(cx, referent_ty)
&& (referent_ty.has_significant_drop(cx.tcx, cx.param_env)
|| !referent_used_exactly_once(cx, possible_borrowers, reference))
{
return false;
}
@ -1127,7 +1166,7 @@ fn needless_borrow_impl_arg_position<'tcx>(
let mut needless_borrow = false;
while let ExprKind::AddrOf(_, _, referent) = expr.kind {
if !check_referent(referent) {
if !check_reference_and_referent(expr, referent) {
break;
}
expr = referent;
@ -1155,6 +1194,36 @@ fn has_ref_mut_self_method(cx: &LateContext<'_>, trait_def_id: DefId) -> bool {
})
}
fn referent_used_exactly_once<'a, 'tcx>(
cx: &'a LateContext<'tcx>,
possible_borrowers: &mut Vec<(LocalDefId, PossibleBorrowerMap<'tcx, 'tcx>)>,
reference: &Expr<'tcx>,
) -> bool {
let mir = enclosing_mir(cx.tcx, reference.hir_id);
if let Some(local) = expr_local(cx.tcx, reference)
&& let [location] = *local_assignments(mir, local).as_slice()
&& let StatementKind::Assign(box (_, Rvalue::Ref(_, _, place))) =
mir.basic_blocks[location.block].statements[location.statement_index].kind
&& !place.has_deref()
{
let body_owner_local_def_id = cx.tcx.hir().enclosing_body_owner(reference.hir_id);
if possible_borrowers
.last()
.map_or(true, |&(local_def_id, _)| local_def_id != body_owner_local_def_id)
{
possible_borrowers.push((body_owner_local_def_id, PossibleBorrowerMap::new(cx, mir)));
}
let possible_borrower = &mut possible_borrowers.last_mut().unwrap().1;
// If `only_borrowers` were used here, the `copyable_iterator::warn` test would fail. The reason is
// that `PossibleBorrowerVisitor::visit_terminator` considers `place.local` a possible borrower of
// itself. See the comment in that method for an explanation as to why.
possible_borrower.bounded_borrowers(&[local], &[local, place.local], place.local, location)
&& used_exactly_once(mir, place.local).unwrap_or(false)
} else {
false
}
}
// Iteratively replaces `param_ty` with `new_ty` in `substs`, and similarly for each resulting
// projected type that is a type parameter. Returns `false` if replacing the types would have an
// effect on the function signature beyond substituting `new_ty` for `param_ty`.
@ -1439,8 +1508,8 @@ fn report<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, state: State, data
}
}
impl Dereferencing {
fn check_local_usage<'tcx>(&mut self, cx: &LateContext<'tcx>, e: &Expr<'tcx>, local: HirId) {
impl<'tcx> Dereferencing<'tcx> {
fn check_local_usage(&mut self, cx: &LateContext<'tcx>, e: &Expr<'tcx>, local: HirId) {
if let Some(outer_pat) = self.ref_locals.get_mut(&local) {
if let Some(pat) = outer_pat {
// Check for auto-deref

9
clippy_lints/src/lib.rs
View file

@ -38,7 +38,6 @@ extern crate rustc_infer;
extern crate rustc_lexer;
extern crate rustc_lint;
extern crate rustc_middle;
extern crate rustc_mir_dataflow;
extern crate rustc_parse;
extern crate rustc_session;
extern crate rustc_span;
@ -418,7 +417,7 @@ pub fn register_pre_expansion_lints(store: &mut rustc_lint::LintStore, sess: &Se
let msrv = conf.msrv.as_ref().and_then(|s| {
parse_msrv(s, None, None).or_else(|| {
sess.err(&format!(
sess.err(format!(
"error reading Clippy's configuration file. `{s}` is not a valid Rust version"
));
None
@ -434,7 +433,7 @@ fn read_msrv(conf: &Conf, sess: &Session) -> Option<RustcVersion> {
.and_then(|v| parse_msrv(&v, None, None));
let clippy_msrv = conf.msrv.as_ref().and_then(|s| {
parse_msrv(s, None, None).or_else(|| {
sess.err(&format!(
sess.err(format!(
"error reading Clippy's configuration file. `{s}` is not a valid Rust version"
));
None
@ -445,7 +444,7 @@ fn read_msrv(conf: &Conf, sess: &Session) -> Option<RustcVersion> {
if let Some(clippy_msrv) = clippy_msrv {
// if both files have an msrv, let's compare them and emit a warning if they differ
if clippy_msrv != cargo_msrv {
sess.warn(&format!(
sess.warn(format!(
"the MSRV in `clippy.toml` and `Cargo.toml` differ; using `{clippy_msrv}` from `clippy.toml`"
));
}
@ -474,7 +473,7 @@ pub fn read_conf(sess: &Session) -> Conf {
let TryConf { conf, errors, warnings } = utils::conf::read(&file_name);
// all conf errors are non-fatal, we just use the default conf in case of error
for error in errors {
sess.err(&format!(
sess.err(format!(
"error reading Clippy's configuration file `{}`: {}",
file_name.display(),
format_error(error)

2
clippy_lints/src/nonstandard_macro_braces.rs
View file

@ -266,7 +266,7 @@ impl<'de> Deserialize<'de> for MacroMatcher {
.iter()
.find(|b| b.0 == brace)
.map(|(o, c)| ((*o).to_owned(), (*c).to_owned()))
.ok_or_else(|| de::Error::custom(&format!("expected one of `(`, `{{`, `[` found `{brace}`")))?,
.ok_or_else(|| de::Error::custom(format!("expected one of `(`, `{{`, `[` found `{brace}`")))?,
})
}
}

454
clippy_lints/src/redundant_clone.rs
View file

@ -1,25 +1,18 @@
use clippy_utils::diagnostics::{span_lint_hir, span_lint_hir_and_then};
use clippy_utils::mir::{visit_local_usage, LocalUsage, PossibleBorrowerMap};
use clippy_utils::source::snippet_opt;
use clippy_utils::ty::{has_drop, is_copy, is_type_diagnostic_item, walk_ptrs_ty_depth};
use clippy_utils::{fn_has_unsatisfiable_preds, match_def_path, paths};
use if_chain::if_chain;
use rustc_data_structures::fx::FxHashMap;
use rustc_errors::Applicability;
use rustc_hir::intravisit::FnKind;
use rustc_hir::{def_id, Body, FnDecl, HirId};
use rustc_index::bit_set::{BitSet, HybridBitSet};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::mir::{
self, traversal,
visit::{MutatingUseContext, NonMutatingUseContext, PlaceContext, Visitor as _},
Mutability,
};
use rustc_middle::ty::{self, visit::TypeVisitor, Ty};
use rustc_mir_dataflow::{Analysis, AnalysisDomain, CallReturnPlaces, GenKill, GenKillAnalysis, ResultsCursor};
use rustc_middle::mir;
use rustc_middle::ty::{self, Ty};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::source_map::{BytePos, Span};
use rustc_span::sym;
use std::ops::ControlFlow;
macro_rules! unwrap_or_continue {
($x:expr) => {
@ -89,21 +82,7 @@ impl<'tcx> LateLintPass<'tcx> for RedundantClone {
let mir = cx.tcx.optimized_mir(def_id.to_def_id());
let possible_origin = {
let mut vis = PossibleOriginVisitor::new(mir);
vis.visit_body(mir);
vis.into_map(cx)
};
let maybe_storage_live_result = MaybeStorageLive
.into_engine(cx.tcx, mir)
.pass_name("redundant_clone")
.iterate_to_fixpoint()
.into_results_cursor(mir);
let mut possible_borrower = {
let mut vis = PossibleBorrowerVisitor::new(cx, mir, possible_origin);
vis.visit_body(mir);
vis.into_map(cx, maybe_storage_live_result)
};
let mut possible_borrower = PossibleBorrowerMap::new(cx, mir);
for (bb, bbdata) in mir.basic_blocks.iter_enumerated() {
let terminator = bbdata.terminator();
@ -374,403 +353,40 @@ struct CloneUsage {
/// Whether the clone value is mutated.
clone_consumed_or_mutated: bool,
}
fn visit_clone_usage(cloned: mir::Local, clone: mir::Local, mir: &mir::Body<'_>, bb: mir::BasicBlock) -> CloneUsage {
struct V {
cloned: mir::Local,
clone: mir::Local,
result: CloneUsage,
}
impl<'tcx> mir::visit::Visitor<'tcx> for V {
fn visit_basic_block_data(&mut self, block: mir::BasicBlock, data: &mir::BasicBlockData<'tcx>) {
let statements = &data.statements;
for (statement_index, statement) in statements.iter().enumerate() {
self.visit_statement(statement, mir::Location { block, statement_index });
}
self.visit_terminator(
data.terminator(),
mir::Location {
block,
statement_index: statements.len(),
},
);
}
fn visit_place(&mut self, place: &mir::Place<'tcx>, ctx: PlaceContext, loc: mir::Location) {
let local = place.local;
if local == self.cloned
&& !matches!(
ctx,
PlaceContext::MutatingUse(MutatingUseContext::Drop) | PlaceContext::NonUse(_)
)
{
self.result.cloned_used = true;
self.result.cloned_consume_or_mutate_loc = self.result.cloned_consume_or_mutate_loc.or_else(|| {
matches!(
ctx,
PlaceContext::NonMutatingUse(NonMutatingUseContext::Move)
| PlaceContext::MutatingUse(MutatingUseContext::Borrow)
)
.then(|| loc)
});
} else if local == self.clone {
match ctx {
PlaceContext::NonMutatingUse(NonMutatingUseContext::Move)
| PlaceContext::MutatingUse(MutatingUseContext::Borrow) => {
self.result.clone_consumed_or_mutated = true;
},
_ => {},
}
}
}
}
let init = CloneUsage {
cloned_used: false,
cloned_consume_or_mutate_loc: None,
// Consider non-temporary clones consumed.
// TODO: Actually check for mutation of non-temporaries.
clone_consumed_or_mutated: mir.local_kind(clone) != mir::LocalKind::Temp,
};
traversal::ReversePostorder::new(mir, bb)
.skip(1)
.fold(init, |usage, (tbb, tdata)| {
// Short-circuit
if (usage.cloned_used && usage.clone_consumed_or_mutated) ||
// Give up on loops
tdata.terminator().successors().any(|s| s == bb)
{
return CloneUsage {
cloned_used: true,
clone_consumed_or_mutated: true,
..usage
};
}
let mut v = V {
cloned,
clone,
result: usage,
};
v.visit_basic_block_data(tbb, tdata);
v.result
})
}
/// Determines liveness of each local purely based on `StorageLive`/`Dead`.
#[derive(Copy, Clone)]
struct MaybeStorageLive;
impl<'tcx> AnalysisDomain<'tcx> for MaybeStorageLive {
type Domain = BitSet<mir::Local>;
const NAME: &'static str = "maybe_storage_live";
fn bottom_value(&self, body: &mir::Body<'tcx>) -> Self::Domain {
// bottom = dead
BitSet::new_empty(body.local_decls.len())
}
fn initialize_start_block(&self, body: &mir::Body<'tcx>, state: &mut Self::Domain) {
for arg in body.args_iter() {
state.insert(arg);
}
}
}
impl<'tcx> GenKillAnalysis<'tcx> for MaybeStorageLive {
type Idx = mir::Local;
fn statement_effect(&self, trans: &mut impl GenKill<Self::Idx>, stmt: &mir::Statement<'tcx>, _: mir::Location) {
match stmt.kind {
mir::StatementKind::StorageLive(l) => trans.gen(l),
mir::StatementKind::StorageDead(l) => trans.kill(l),
_ => (),
}
}
fn terminator_effect(
&self,
_trans: &mut impl GenKill<Self::Idx>,
_terminator: &mir::Terminator<'tcx>,
_loc: mir::Location,
) {
}
fn call_return_effect(
&self,
_trans: &mut impl GenKill<Self::Idx>,
_block: mir::BasicBlock,
_return_places: CallReturnPlaces<'_, 'tcx>,
) {
// Nothing to do when a call returns successfully
}
}
/// Collects the possible borrowers of each local.
/// For example, `b = &a; c = &a;` will make `b` and (transitively) `c`
/// possible borrowers of `a`.
struct PossibleBorrowerVisitor<'a, 'tcx> {
possible_borrower: TransitiveRelation,
body: &'a mir::Body<'tcx>,
cx: &'a LateContext<'tcx>,
possible_origin: FxHashMap<mir::Local, HybridBitSet<mir::Local>>,
}
impl<'a, 'tcx> PossibleBorrowerVisitor<'a, 'tcx> {
fn new(
cx: &'a LateContext<'tcx>,
body: &'a mir::Body<'tcx>,
possible_origin: FxHashMap<mir::Local, HybridBitSet<mir::Local>>,
) -> Self {
Self {
possible_borrower: TransitiveRelation::default(),
cx,
body,
possible_origin,
}
}
fn into_map(
self,
cx: &LateContext<'tcx>,
maybe_live: ResultsCursor<'tcx, 'tcx, MaybeStorageLive>,
) -> PossibleBorrowerMap<'a, 'tcx> {
let mut map = FxHashMap::default();
for row in (1..self.body.local_decls.len()).map(mir::Local::from_usize) {
if is_copy(cx, self.body.local_decls[row].ty) {
continue;
}
let mut borrowers = self.possible_borrower.reachable_from(row, self.body.local_decls.len());
borrowers.remove(mir::Local::from_usize(0));
if !borrowers.is_empty() {
map.insert(row, borrowers);
}
}
let bs = BitSet::new_empty(self.body.local_decls.len());
PossibleBorrowerMap {
map,
maybe_live,
bitset: (bs.clone(), bs),
}
}
}
impl<'a, 'tcx> mir::visit::Visitor<'tcx> for PossibleBorrowerVisitor<'a, 'tcx> {
fn visit_assign(&mut self, place: &mir::Place<'tcx>, rvalue: &mir::Rvalue<'_>, _location: mir::Location) {
let lhs = place.local;
match rvalue {
mir::Rvalue::Ref(_, _, borrowed) => {
self.possible_borrower.add(borrowed.local, lhs);
},
other => {
if ContainsRegion
.visit_ty(place.ty(&self.body.local_decls, self.cx.tcx).ty)
.is_continue()
{
return;
}
rvalue_locals(other, |rhs| {
if lhs != rhs {
self.possible_borrower.add(rhs, lhs);
}
});
},
}
}
fn visit_terminator(&mut self, terminator: &mir::Terminator<'_>, _loc: mir::Location) {
if let mir::TerminatorKind::Call {
args,
destination: mir::Place { local: dest, .. },
..
} = &terminator.kind
{
// TODO add doc
// If the call returns something with lifetimes,
// let's conservatively assume the returned value contains lifetime of all the arguments.
// For example, given `let y: Foo<'a> = foo(x)`, `y` is considered to be a possible borrower of `x`.
let mut immutable_borrowers = vec![];
let mut mutable_borrowers = vec![];
for op in args {
match op {
mir::Operand::Copy(p) | mir::Operand::Move(p) => {
if let ty::Ref(_, _, Mutability::Mut) = self.body.local_decls[p.local].ty.kind() {
mutable_borrowers.push(p.local);
} else {
immutable_borrowers.push(p.local);
}
},
mir::Operand::Constant(..) => (),
}
}
let mut mutable_variables: Vec<mir::Local> = mutable_borrowers
.iter()
.filter_map(|r| self.possible_origin.get(r))
.flat_map(HybridBitSet::iter)
.collect();
if ContainsRegion.visit_ty(self.body.local_decls[*dest].ty).is_break() {
mutable_variables.push(*dest);
}
for y in mutable_variables {
for x in &immutable_borrowers {
self.possible_borrower.add(*x, y);
}
for x in &mutable_borrowers {
self.possible_borrower.add(*x, y);
}
}
}
}
}
/// Collect possible borrowed for every `&mut` local.
/// For example, `_1 = &mut _2` generate _1: {_2,...}
/// Known Problems: not sure all borrowed are tracked
struct PossibleOriginVisitor<'a, 'tcx> {
possible_origin: TransitiveRelation,
body: &'a mir::Body<'tcx>,
}
impl<'a, 'tcx> PossibleOriginVisitor<'a, 'tcx> {
fn new(body: &'a mir::Body<'tcx>) -> Self {
Self {
possible_origin: TransitiveRelation::default(),
body,
}
}
fn into_map(self, cx: &LateContext<'tcx>) -> FxHashMap<mir::Local, HybridBitSet<mir::Local>> {
let mut map = FxHashMap::default();
for row in (1..self.body.local_decls.len()).map(mir::Local::from_usize) {
if is_copy(cx, self.body.local_decls[row].ty) {
continue;
}
let mut borrowers = self.possible_origin.reachable_from(row, self.body.local_decls.len());
borrowers.remove(mir::Local::from_usize(0));
if !borrowers.is_empty() {
map.insert(row, borrowers);
}
}
map
}
}
impl<'a, 'tcx> mir::visit::Visitor<'tcx> for PossibleOriginVisitor<'a, 'tcx> {
fn visit_assign(&mut self, place: &mir::Place<'tcx>, rvalue: &mir::Rvalue<'_>, _location: mir::Location) {
let lhs = place.local;
match rvalue {
// Only consider `&mut`, which can modify origin place
mir::Rvalue::Ref(_, rustc_middle::mir::BorrowKind::Mut { .. }, borrowed) |
// _2: &mut _;
// _3 = move _2
mir::Rvalue::Use(mir::Operand::Move(borrowed)) |
// _3 = move _2 as &mut _;
mir::Rvalue::Cast(_, mir::Operand::Move(borrowed), _)
=> {
self.possible_origin.add(lhs, borrowed.local);
},
_ => {},
}
}
}
struct ContainsRegion;
impl TypeVisitor<'_> for ContainsRegion {
type BreakTy = ();
fn visit_region(&mut self, _: ty::Region<'_>) -> ControlFlow<Self::BreakTy> {
ControlFlow::BREAK
}
}
fn rvalue_locals(rvalue: &mir::Rvalue<'_>, mut visit: impl FnMut(mir::Local)) {
use rustc_middle::mir::Rvalue::{Aggregate, BinaryOp, Cast, CheckedBinaryOp, Repeat, UnaryOp, Use};
let mut visit_op = |op: &mir::Operand<'_>| match op {
mir::Operand::Copy(p) | mir::Operand::Move(p) => visit(p.local),
mir::Operand::Constant(..) => (),
};
match rvalue {
Use(op) | Repeat(op, _) | Cast(_, op, _) | UnaryOp(_, op) => visit_op(op),
Aggregate(_, ops) => ops.iter().for_each(visit_op),
BinaryOp(_, box (lhs, rhs)) | CheckedBinaryOp(_, box (lhs, rhs)) => {
visit_op(lhs);
visit_op(rhs);
if let Some((
LocalUsage {
local_use_locs: cloned_use_locs,
local_consume_or_mutate_locs: cloned_consume_or_mutate_locs,
},
_ => (),
}
}
/// Result of `PossibleBorrowerVisitor`.
struct PossibleBorrowerMap<'a, 'tcx> {
/// Mapping `Local -> its possible borrowers`
map: FxHashMap<mir::Local, HybridBitSet<mir::Local>>,
maybe_live: ResultsCursor<'a, 'tcx, MaybeStorageLive>,
// Caches to avoid allocation of `BitSet` on every query
bitset: (BitSet<mir::Local>, BitSet<mir::Local>),
}
impl PossibleBorrowerMap<'_, '_> {
/// Returns true if the set of borrowers of `borrowed` living at `at` matches with `borrowers`.
fn only_borrowers(&mut self, borrowers: &[mir::Local], borrowed: mir::Local, at: mir::Location) -> bool {
self.maybe_live.seek_after_primary_effect(at);
self.bitset.0.clear();
let maybe_live = &mut self.maybe_live;
if let Some(bitset) = self.map.get(&borrowed) {
for b in bitset.iter().filter(move |b| maybe_live.contains(*b)) {
self.bitset.0.insert(b);
}
} else {
return false;
LocalUsage {
local_use_locs: _,
local_consume_or_mutate_locs: clone_consume_or_mutate_locs,
},
)) = visit_local_usage(
&[cloned, clone],
mir,
mir::Location {
block: bb,
statement_index: mir.basic_blocks[bb].statements.len(),
},
)
.map(|mut vec| (vec.remove(0), vec.remove(0)))
{
CloneUsage {
cloned_used: !cloned_use_locs.is_empty(),
cloned_consume_or_mutate_loc: cloned_consume_or_mutate_locs.first().copied(),
// Consider non-temporary clones consumed.
// TODO: Actually check for mutation of non-temporaries.
clone_consumed_or_mutated: mir.local_kind(clone) != mir::LocalKind::Temp
|| !clone_consume_or_mutate_locs.is_empty(),
}
self.bitset.1.clear();
for b in borrowers {
self.bitset.1.insert(*b);
} else {
CloneUsage {
cloned_used: true,
cloned_consume_or_mutate_loc: None,
clone_consumed_or_mutated: true,
}
self.bitset.0 == self.bitset.1
}
fn local_is_alive_at(&mut self, local: mir::Local, at: mir::Location) -> bool {
self.maybe_live.seek_after_primary_effect(at);
self.maybe_live.contains(local)
}
}
#[derive(Default)]
struct TransitiveRelation {
relations: FxHashMap<mir::Local, Vec<mir::Local>>,
}
impl TransitiveRelation {
fn add(&mut self, a: mir::Local, b: mir::Local) {
self.relations.entry(a).or_default().push(b);
}
fn reachable_from(&self, a: mir::Local, domain_size: usize) -> HybridBitSet<mir::Local> {
let mut seen = HybridBitSet::new_empty(domain_size);
let mut stack = vec![a];
while let Some(u) = stack.pop() {
if let Some(edges) = self.relations.get(&u) {
for &v in edges {
if seen.insert(v) {
stack.push(v);
}
}
}
}
seen
}
}