-use crate::utils::{
- fn_has_unsatisfiable_preds, has_drop, is_copy, is_type_diagnostic_item, match_def_path, match_type, paths,
- snippet_opt, span_lint_hir, span_lint_hir_and_then, walk_ptrs_ty_depth,
-};
+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, is_type_lang_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, transitive_relation::TransitiveRelation};
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_hir::{def_id, Body, FnDecl, HirId, LangItem};
use rustc_lint::{LateContext, LateLintPass};
-use rustc_middle::mir::{
- self, traversal,
- visit::{MutatingUseContext, NonMutatingUseContext, PlaceContext, Visitor as _},
-};
-use rustc_middle::ty::{self, fold::TypeVisitor, Ty};
-use rustc_mir::dataflow::{Analysis, AnalysisDomain, 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::convert::TryFrom;
-use std::ops::ControlFlow;
macro_rules! unwrap_or_continue {
($x:expr) => {
}
declare_clippy_lint! {
- /// **What it does:** Checks for a redundant `clone()` (and its relatives) which clones an owned
+ /// ### What it does
+ /// Checks for a redundant `clone()` (and its relatives) which clones an owned
/// value that is going to be dropped without further use.
///
- /// **Why is this bad?** It is not always possible for the compiler to eliminate useless
+ /// ### Why is this bad?
+ /// It is not always possible for the compiler to eliminate useless
/// allocations and deallocations generated by redundant `clone()`s.
///
- /// **Known problems:**
- ///
+ /// ### Known problems
/// False-negatives: analysis performed by this lint is conservative and limited.
///
- /// **Example:**
+ /// ### Example
/// ```rust
/// # use std::path::Path;
/// # #[derive(Clone)]
///
/// Path::new("/a/b").join("c").to_path_buf();
/// ```
+ #[clippy::version = "1.32.0"]
pub REDUNDANT_CLONE,
perf,
"`clone()` of an owned value that is going to be dropped immediately"
declare_lint_pass!(RedundantClone => [REDUNDANT_CLONE]);
impl<'tcx> LateLintPass<'tcx> for RedundantClone {
- #[allow(clippy::too_many_lines)]
+ #[expect(clippy::too_many_lines)]
fn check_fn(
&mut self,
cx: &LateContext<'tcx>,
let mir = cx.tcx.optimized_mir(def_id.to_def_id());
- 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);
- vis.visit_body(&mir);
- vis.into_map(cx, maybe_storage_live_result)
- };
-
- for (bb, bbdata) in mir.basic_blocks().iter_enumerated() {
+ let mut possible_borrower = PossibleBorrowerMap::new(cx, mir);
+
+ for (bb, bbdata) in mir.basic_blocks.iter_enumerated() {
let terminator = bbdata.terminator();
if terminator.source_info.span.from_expansion() {
}
// Give up on loops
- if terminator.successors().any(|s| *s == bb) {
+ if terminator.successors().any(|s| s == bb) {
continue;
}
let from_borrow = match_def_path(cx, fn_def_id, &paths::CLONE_TRAIT_METHOD)
|| match_def_path(cx, fn_def_id, &paths::TO_OWNED_METHOD)
|| (match_def_path(cx, fn_def_id, &paths::TO_STRING_METHOD)
- && is_type_diagnostic_item(cx, arg_ty, sym::string_type));
+ && is_type_lang_item(cx, arg_ty, LangItem::String));
let from_deref = !from_borrow
&& (match_def_path(cx, fn_def_id, &paths::PATH_TO_PATH_BUF)
continue;
}
- if let ty::Adt(ref def, _) = arg_ty.kind() {
- if match_def_path(cx, def.did, &paths::MEM_MANUALLY_DROP) {
+ if let ty::Adt(def, _) = arg_ty.kind() {
+ if def.is_manually_drop() {
continue;
}
}
- // `{ cloned = &arg; clone(move cloned); }` or `{ cloned = &arg; to_path_buf(cloned); }`
+ // `{ arg = &cloned; clone(move arg); }` or `{ arg = &cloned; to_path_buf(arg); }`
let (cloned, cannot_move_out) = unwrap_or_continue!(find_stmt_assigns_to(cx, mir, arg, from_borrow, bb));
let loc = mir::Location {
// `arg` is a reference as it is `.deref()`ed in the previous block.
// Look into the predecessor block and find out the source of deref.
- let ps = &mir.predecessors()[bb];
+ let ps = &mir.basic_blocks.predecessors()[bb];
if ps.len() != 1 {
continue;
}
if let Some((pred_fn_def_id, pred_arg, pred_arg_ty, res)) =
is_call_with_ref_arg(cx, mir, &pred_terminator.kind);
if res == cloned;
- if match_def_path(cx, pred_fn_def_id, &paths::DEREF_TRAIT_METHOD);
- if match_type(cx, pred_arg_ty, &paths::PATH_BUF)
- || match_type(cx, pred_arg_ty, &paths::OS_STRING);
+ if cx.tcx.is_diagnostic_item(sym::deref_method, pred_fn_def_id);
+ if is_type_diagnostic_item(cx, pred_arg_ty, sym::PathBuf)
+ || is_type_diagnostic_item(cx, pred_arg_ty, sym::OsString);
then {
(pred_arg, res)
} else {
unwrap_or_continue!(find_stmt_assigns_to(cx, mir, pred_arg, true, ps[0]));
let loc = mir::Location {
block: bb,
- statement_index: mir.basic_blocks()[bb].statements.len(),
+ statement_index: mir.basic_blocks[bb].statements.len(),
};
// This can be turned into `res = move local` if `arg` and `cloned` are not borrowed
(local, deref_clone_ret)
};
- let is_temp = mir.local_kind(ret_local) == mir::LocalKind::Temp;
-
- // 1. `local` can be moved out if it is not used later.
- // 2. If `ret_local` is a temporary and is neither consumed nor mutated, we can remove this `clone`
- // call anyway.
- let (used, consumed_or_mutated) = traversal::ReversePostorder::new(&mir, bb).skip(1).fold(
- (false, !is_temp),
- |(used, consumed), (tbb, tdata)| {
- // Short-circuit
- if (used && consumed) ||
- // Give up on loops
- tdata.terminator().successors().any(|s| *s == bb)
- {
- return (true, true);
+ let clone_usage = if local == ret_local {
+ CloneUsage {
+ cloned_used: false,
+ cloned_consume_or_mutate_loc: None,
+ clone_consumed_or_mutated: true,
+ }
+ } else {
+ let clone_usage = visit_clone_usage(local, ret_local, mir, bb);
+ if clone_usage.cloned_used && clone_usage.clone_consumed_or_mutated {
+ // cloned value is used, and the clone is modified or moved
+ continue;
+ } else if let Some(loc) = clone_usage.cloned_consume_or_mutate_loc {
+ // cloned value is mutated, and the clone is alive.
+ if possible_borrower.local_is_alive_at(ret_local, loc) {
+ continue;
}
+ }
+ clone_usage
+ };
- let mut vis = LocalUseVisitor {
- used: (local, false),
- consumed_or_mutated: (ret_local, false),
- };
- vis.visit_basic_block_data(tbb, tdata);
- (used || vis.used.1, consumed || vis.consumed_or_mutated.1)
- },
- );
-
- if !used || !consumed_or_mutated {
- let span = terminator.source_info.span;
- let scope = terminator.source_info.scope;
- let node = mir.source_scopes[scope]
- .local_data
- .as_ref()
- .assert_crate_local()
- .lint_root;
-
- if_chain! {
- if let Some(snip) = snippet_opt(cx, span);
- if let Some(dot) = snip.rfind('.');
- then {
- let sugg_span = span.with_lo(
- span.lo() + BytePos(u32::try_from(dot).unwrap())
- );
- let mut app = Applicability::MaybeIncorrect;
-
- let call_snip = &snip[dot + 1..];
- // Machine applicable when `call_snip` looks like `foobar()`
- if let Some(call_snip) = call_snip.strip_suffix("()").map(str::trim) {
- if call_snip.as_bytes().iter().all(|b| b.is_ascii_alphabetic() || *b == b'_') {
- app = Applicability::MachineApplicable;
- }
+ let span = terminator.source_info.span;
+ let scope = terminator.source_info.scope;
+ let node = mir.source_scopes[scope]
+ .local_data
+ .as_ref()
+ .assert_crate_local()
+ .lint_root;
+
+ if_chain! {
+ if let Some(snip) = snippet_opt(cx, span);
+ if let Some(dot) = snip.rfind('.');
+ then {
+ let sugg_span = span.with_lo(
+ span.lo() + BytePos(u32::try_from(dot).unwrap())
+ );
+ let mut app = Applicability::MaybeIncorrect;
+
+ let call_snip = &snip[dot + 1..];
+ // Machine applicable when `call_snip` looks like `foobar()`
+ if let Some(call_snip) = call_snip.strip_suffix("()").map(str::trim) {
+ if call_snip.as_bytes().iter().all(|b| b.is_ascii_alphabetic() || *b == b'_') {
+ app = Applicability::MachineApplicable;
}
+ }
- span_lint_hir_and_then(cx, REDUNDANT_CLONE, node, sugg_span, "redundant clone", |diag| {
- diag.span_suggestion(
- sugg_span,
- "remove this",
- String::new(),
- app,
+ span_lint_hir_and_then(cx, REDUNDANT_CLONE, node, sugg_span, "redundant clone", |diag| {
+ diag.span_suggestion(
+ sugg_span,
+ "remove this",
+ "",
+ app,
+ );
+ if clone_usage.cloned_used {
+ diag.span_note(
+ span,
+ "cloned value is neither consumed nor mutated",
);
- if used {
- diag.span_note(
- span,
- "cloned value is neither consumed nor mutated",
- );
- } else {
- diag.span_note(
- span.with_hi(span.lo() + BytePos(u32::try_from(dot).unwrap())),
- "this value is dropped without further use",
- );
- }
- });
- } else {
- span_lint_hir(cx, REDUNDANT_CLONE, node, span, "redundant clone");
- }
+ } else {
+ diag.span_note(
+ span.with_hi(span.lo() + BytePos(u32::try_from(dot).unwrap())),
+ "this value is dropped without further use",
+ );
+ }
+ });
+ } else {
+ span_lint_hir(cx, REDUNDANT_CLONE, node, span, "redundant clone");
}
}
}
if let mir::TerminatorKind::Call { func, args, destination, .. } = kind;
if args.len() == 1;
if let mir::Operand::Move(mir::Place { local, .. }) = &args[0];
- if let ty::FnDef(def_id, _) = *func.ty(&*mir, cx.tcx).kind();
- if let (inner_ty, 1) = walk_ptrs_ty_depth(args[0].ty(&*mir, cx.tcx));
+ if let ty::FnDef(def_id, _) = *func.ty(mir, cx.tcx).kind();
+ if let (inner_ty, 1) = walk_ptrs_ty_depth(args[0].ty(mir, cx.tcx));
if !is_copy(cx, inner_ty);
then {
- Some((def_id, *local, inner_ty, destination.as_ref().map(|(dest, _)| dest)?.as_local()?))
+ Some((def_id, *local, inner_ty, destination.as_local()?))
} else {
None
}
by_ref: bool,
bb: mir::BasicBlock,
) -> Option<(mir::Local, CannotMoveOut)> {
- let rvalue = mir.basic_blocks()[bb].statements.iter().rev().find_map(|stmt| {
+ let rvalue = mir.basic_blocks[bb].statements.iter().rev().find_map(|stmt| {
if let mir::StatementKind::Assign(box (mir::Place { local, .. }, v)) = &stmt.kind {
return if *local == to_local { Some(v) } else { None };
}
None
})?;
- match (by_ref, &*rvalue) {
+ match (by_ref, rvalue) {
(true, mir::Rvalue::Ref(_, _, place)) | (false, mir::Rvalue::Use(mir::Operand::Copy(place))) => {
Some(base_local_and_movability(cx, mir, *place))
},
(local, deref || field || slice)
}
-struct LocalUseVisitor {
- used: (mir::Local, bool),
- consumed_or_mutated: (mir::Local, bool),
-}
-
-impl<'tcx> mir::visit::Visitor<'tcx> for LocalUseVisitor {
- 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, _: mir::Location) {
- let local = place.local;
-
- if local == self.used.0
- && !matches!(
- ctx,
- PlaceContext::MutatingUse(MutatingUseContext::Drop) | PlaceContext::NonUse(_)
- )
- {
- self.used.1 = true;
- }
-
- if local == self.consumed_or_mutated.0 {
- match ctx {
- PlaceContext::NonMutatingUse(NonMutatingUseContext::Move)
- | PlaceContext::MutatingUse(MutatingUseContext::Borrow) => {
- self.consumed_or_mutated.1 = true;
- },
- _ => {},
- }
- }
- }
-}
-
-/// 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,
- _in_out: &mut impl GenKill<Self::Idx>,
- _block: mir::BasicBlock,
- _func: &mir::Operand<'tcx>,
- _args: &[mir::Operand<'tcx>],
- _return_place: mir::Place<'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<mir::Local>,
- body: &'a mir::Body<'tcx>,
- cx: &'a LateContext<'tcx>,
-}
-
-impl<'a, 'tcx> PossibleBorrowerVisitor<'a, 'tcx> {
- fn new(cx: &'a LateContext<'tcx>, body: &'a mir::Body<'tcx>) -> Self {
- Self {
- possible_borrower: TransitiveRelation::default(),
- cx,
- body,
- }
- }
-
- 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 borrowers = self.possible_borrower.reachable_from(&row);
- if !borrowers.is_empty() {
- let mut bs = HybridBitSet::new_empty(self.body.local_decls.len());
- for &c in borrowers {
- if c != mir::Local::from_usize(0) {
- bs.insert(c);
- }
- }
-
- if !bs.is_empty() {
- map.insert(row, bs);
- }
- }
- }
-
- let bs = BitSet::new_empty(self.body.local_decls.len());
- PossibleBorrowerMap {
- map,
- maybe_live,
- bitset: (bs.clone(), bs),
- }
- }
+#[derive(Default)]
+struct CloneUsage {
+ /// Whether the cloned value is used after the clone.
+ cloned_used: bool,
+ /// The first location where the cloned value is consumed or mutated, if any.
+ cloned_consume_or_mutate_loc: Option<mir::Location>,
+ /// Whether the clone value is mutated.
+ clone_consumed_or_mutated: bool,
}
-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: Some((mir::Place { local: dest, .. }, _)),
- ..
- } = &terminator.kind
- {
- // 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`.
- if ContainsRegion.visit_ty(&self.body.local_decls[*dest].ty).is_continue() {
- return;
- }
-
- for op in args {
- match op {
- mir::Operand::Copy(p) | mir::Operand::Move(p) => {
- self.possible_borrower.add(p.local, *dest);
- },
- _ => (),
- }
- }
- }
- }
-}
-
-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),
- _ => (),
- };
-
- 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);
- }
- _ => (),
- }
-}
-
-/// 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;
+fn visit_clone_usage(cloned: mir::Local, clone: mir::Local, mir: &mir::Body<'_>, bb: mir::BasicBlock) -> CloneUsage {
+ if let Some((
+ LocalUsage {
+ local_use_locs: cloned_use_locs,
+ local_consume_or_mutate_locs: cloned_consume_or_mutate_locs,
+ },
+ 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
}
}
projects / rust.git / blobdiff