use crate::utils::{
- has_drop, is_copy, match_def_path, match_type, paths, snippet_opt, span_lint_hir, span_lint_hir_and_then,
- walk_ptrs_ty_depth,
+ fn_has_unsatisfiable_preds, has_drop, is_copy, is_type_diagnostic_item, match_def_path, paths, snippet_opt,
+ span_lint_hir, span_lint_hir_and_then, walk_ptrs_ty_depth,
};
use if_chain::if_chain;
-use matches::matches;
-use rustc::mir::{
- self, traversal,
- visit::{MutatingUseContext, PlaceContext, Visitor as _},
-};
-use rustc::ty::{self, fold::TypeVisitor, Ty};
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_lint::{LateContext, LateLintPass};
-use rustc_mir::dataflow::generic::{Analysis, AnalysisDomain, GenKill, GenKillAnalysis, ResultsCursor};
-use rustc_mir::dataflow::BottomValue;
+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_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_lint_pass!(RedundantClone => [REDUNDANT_CLONE]);
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for RedundantClone {
+impl<'tcx> LateLintPass<'tcx> for RedundantClone {
#[allow(clippy::too_many_lines)]
fn check_fn(
&mut self,
- cx: &LateContext<'a, 'tcx>,
+ cx: &LateContext<'tcx>,
_: FnKind<'tcx>,
_: &'tcx FnDecl<'_>,
body: &'tcx Body<'_>,
_: HirId,
) {
let def_id = cx.tcx.hir().body_owner_def_id(body.id());
- let mir = cx.tcx.optimized_mir(def_id);
- let mir_read_only = mir.unwrap_read_only();
+
+ // Building MIR for `fn`s with unsatisfiable preds results in ICE.
+ if fn_has_unsatisfiable_preds(cx, def_id.to_def_id()) {
+ return;
+ }
+
+ let mir = cx.tcx.optimized_mir(def_id.to_def_id());
let maybe_storage_live_result = MaybeStorageLive
- .into_engine(cx.tcx, mir, def_id)
+ .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_read_only);
+ vis.visit_body(&mir);
vis.into_map(cx, maybe_storage_live_result)
};
continue;
}
- let (fn_def_id, arg, arg_ty, _) = unwrap_or_continue!(is_call_with_ref_arg(cx, mir, &terminator.kind));
+ let (fn_def_id, arg, arg_ty, clone_ret) =
+ unwrap_or_continue!(is_call_with_ref_arg(cx, mir, &terminator.kind));
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) && match_type(cx, arg_ty, &paths::STRING));
+ || (match_def_path(cx, fn_def_id, &paths::TO_STRING_METHOD)
+ && is_type_diagnostic_item(cx, arg_ty, sym::string_type));
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) {
+ continue;
+ }
+ }
+
// `{ cloned = &arg; clone(move cloned); }` or `{ cloned = &arg; to_path_buf(cloned); }`
let (cloned, cannot_move_out) = unwrap_or_continue!(find_stmt_assigns_to(cx, mir, arg, from_borrow, bb));
statement_index: bbdata.statements.len(),
};
- // Cloned local
- let local = if from_borrow {
+ // `Local` to be cloned, and a local of `clone` call's destination
+ let (local, ret_local) = if from_borrow {
// `res = clone(arg)` can be turned into `res = move arg;`
// if `arg` is the only borrow of `cloned` at this point.
continue;
}
- cloned
+ (cloned, clone_ret)
} else {
// `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_read_only.predecessors_for(bb);
+ let ps = &mir.predecessors()[bb];
if ps.len() != 1 {
continue;
}
let pred_terminator = mir[ps[0]].terminator();
// receiver of the `deref()` call
- let pred_arg = if_chain! {
- if let Some((pred_fn_def_id, pred_arg, pred_arg_ty, Some(res))) =
+ let (pred_arg, deref_clone_ret) = if_chain! {
+ 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.local == 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 res == cloned;
+ 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
+ (pred_arg, res)
} else {
continue;
}
continue;
}
- local
+ (local, deref_clone_ret)
};
- // `local` cannot be moved out if it is used later
- let used_later = traversal::ReversePostorder::new(&mir, bb).skip(1).any(|(tbb, tdata)| {
- // Give up on loops
- if tdata.terminator().successors().any(|s| *s == bb) {
- return true;
- }
+ 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 mut vis = LocalUseVisitor {
- local,
- used_other_than_drop: false,
- };
- vis.visit_basic_block_data(tbb, tdata);
- vis.used_other_than_drop
- });
+ 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_later {
+ if !used || !consumed_or_mutated {
let span = terminator.source_info.span;
let scope = terminator.source_info.scope;
let node = mir.source_scopes[scope]
);
let mut app = Applicability::MaybeIncorrect;
- let mut call_snip = &snip[dot + 1..];
+ let call_snip = &snip[dot + 1..];
// Machine applicable when `call_snip` looks like `foobar()`
- if call_snip.ends_with("()") {
- call_snip = call_snip[..call_snip.len()-2].trim();
+ 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", |db| {
- db.span_suggestion(
+ span_lint_hir_and_then(cx, REDUNDANT_CLONE, node, sugg_span, "redundant clone", |diag| {
+ diag.span_suggestion(
sugg_span,
"remove this",
String::new(),
app,
);
- db.span_note(
- span.with_hi(span.lo() + BytePos(u32::try_from(dot).unwrap())),
- "this value is dropped without further use",
- );
+ 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");
/// If `kind` is `y = func(x: &T)` where `T: !Copy`, returns `(DefId of func, x, T, y)`.
fn is_call_with_ref_arg<'tcx>(
- cx: &LateContext<'_, 'tcx>,
+ cx: &LateContext<'tcx>,
mir: &'tcx mir::Body<'tcx>,
kind: &'tcx mir::TerminatorKind<'tcx>,
-) -> Option<(def_id::DefId, mir::Local, Ty<'tcx>, Option<&'tcx mir::Place<'tcx>>)> {
+) -> Option<(def_id::DefId, mir::Local, Ty<'tcx>, mir::Local)> {
if_chain! {
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 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)))
+ Some((def_id, *local, inner_ty, destination.as_ref().map(|(dest, _)| dest)?.as_local()?))
} else {
None
}
/// Finds the first `to = (&)from`, and returns
/// ``Some((from, whether `from` cannot be moved out))``.
fn find_stmt_assigns_to<'tcx>(
- cx: &LateContext<'_, 'tcx>,
+ cx: &LateContext<'tcx>,
mir: &mir::Body<'tcx>,
to_local: mir::Local,
by_ref: bool,
match (by_ref, &*rvalue) {
(true, mir::Rvalue::Ref(_, _, place)) | (false, mir::Rvalue::Use(mir::Operand::Copy(place))) => {
- base_local_and_movability(cx, mir, *place)
+ Some(base_local_and_movability(cx, mir, *place))
},
(false, mir::Rvalue::Ref(_, _, place)) => {
if let [mir::ProjectionElem::Deref] = place.as_ref().projection {
- base_local_and_movability(cx, mir, *place)
+ Some(base_local_and_movability(cx, mir, *place))
} else {
None
}
///
/// Also reports whether given `place` cannot be moved out.
fn base_local_and_movability<'tcx>(
- cx: &LateContext<'_, 'tcx>,
+ cx: &LateContext<'tcx>,
mir: &mir::Body<'tcx>,
place: mir::Place<'tcx>,
-) -> Option<(mir::Local, CannotMoveOut)> {
- use rustc::mir::PlaceRef;
+) -> (mir::Local, CannotMoveOut) {
+ use rustc_middle::mir::PlaceRef;
// Dereference. You cannot move things out from a borrowed value.
let mut deref = false;
// Accessing a field of an ADT that has `Drop`. Moving the field out will cause E0509.
let mut field = false;
+ // If projection is a slice index then clone can be removed only if the
+ // underlying type implements Copy
+ let mut slice = false;
let PlaceRef { local, mut projection } = place.as_ref();
while let [base @ .., elem] = projection {
deref |= matches!(elem, mir::ProjectionElem::Deref);
field |= matches!(elem, mir::ProjectionElem::Field(..))
&& has_drop(cx, mir::Place::ty_from(local, projection, &mir.local_decls, cx.tcx).ty);
+ slice |= matches!(elem, mir::ProjectionElem::Index(..))
+ && !is_copy(cx, mir::Place::ty_from(local, projection, &mir.local_decls, cx.tcx).ty);
}
- Some((local, deref || field))
+ (local, deref || field || slice)
}
struct LocalUseVisitor {
- local: mir::Local,
- used_other_than_drop: bool,
+ used: (mir::Local, bool),
+ consumed_or_mutated: (mir::Local, bool),
}
impl<'tcx> mir::visit::Visitor<'tcx> for LocalUseVisitor {
let statements = &data.statements;
for (statement_index, statement) in statements.iter().enumerate() {
self.visit_statement(statement, mir::Location { block, statement_index });
-
- // Once flagged, skip remaining statements
- if self.used_other_than_drop {
- return;
- }
}
self.visit_terminator(
);
}
- fn visit_local(&mut self, local: &mir::Local, ctx: PlaceContext, _: mir::Location) {
- match ctx {
- PlaceContext::MutatingUse(MutatingUseContext::Drop) | PlaceContext::NonUse(_) => return,
- _ => {},
+ 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.local {
- self.used_other_than_drop = true;
+ if local == self.consumed_or_mutated.0 {
+ match ctx {
+ PlaceContext::NonMutatingUse(NonMutatingUseContext::Move)
+ | PlaceContext::MutatingUse(MutatingUseContext::Borrow) => {
+ self.consumed_or_mutated.1 = true;
+ },
+ _ => {},
+ }
}
}
}
struct MaybeStorageLive;
impl<'tcx> AnalysisDomain<'tcx> for MaybeStorageLive {
- type Idx = mir::Local;
+ type Domain = BitSet<mir::Local>;
const NAME: &'static str = "maybe_storage_live";
- fn bits_per_block(&self, body: &mir::Body<'tcx>) -> usize {
- body.local_decls.len()
+ 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 BitSet<Self::Idx>) {
+ 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),
_block: mir::BasicBlock,
_func: &mir::Operand<'tcx>,
_args: &[mir::Operand<'tcx>],
- _return_place: &mir::Place<'tcx>,
+ _return_place: mir::Place<'tcx>,
) {
// Nothing to do when a call returns successfully
}
}
-impl BottomValue for MaybeStorageLive {
- /// bottom = dead
- const BOTTOM_VALUE: bool = false;
-}
-
/// 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<'a, 'tcx>,
+ cx: &'a LateContext<'tcx>,
}
impl<'a, 'tcx> PossibleBorrowerVisitor<'a, 'tcx> {
- fn new(cx: &'a LateContext<'a, 'tcx>, body: &'a mir::Body<'tcx>) -> Self {
+ fn new(cx: &'a LateContext<'tcx>, body: &'a mir::Body<'tcx>) -> Self {
Self {
possible_borrower: TransitiveRelation::default(),
cx,
fn into_map(
self,
- cx: &LateContext<'a, 'tcx>,
+ cx: &LateContext<'tcx>,
maybe_live: ResultsCursor<'tcx, 'tcx, MaybeStorageLive>,
) -> PossibleBorrowerMap<'a, 'tcx> {
let mut map = FxHashMap::default();
self.possible_borrower.add(borrowed.local, lhs);
},
other => {
- if !ContainsRegion.visit_ty(place.ty(&self.body.local_decls, self.cx.tcx).ty) {
+ if ContainsRegion
+ .visit_ty(place.ty(&self.body.local_decls, self.cx.tcx).ty)
+ .is_continue()
+ {
return;
}
rvalue_locals(other, |rhs| {
// 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) {
+ if ContainsRegion.visit_ty(&self.body.local_decls[*dest].ty).is_continue() {
return;
}
struct ContainsRegion;
impl TypeVisitor<'_> for ContainsRegion {
- fn visit_region(&mut self, _: ty::Region<'_>) -> bool {
- true
+ 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::mir::Rvalue::*;
+ 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(_, lhs, rhs) | CheckedBinaryOp(_, lhs, rhs) => {
+ BinaryOp(_, box (lhs, rhs)) | CheckedBinaryOp(_, box (lhs, rhs)) => {
visit_op(lhs);
visit_op(rhs);
- },
+ }
_ => (),
}
}
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(at);
+ self.maybe_live.seek_after_primary_effect(at);
self.bitset.0.clear();
let maybe_live = &mut self.maybe_live;