diff --git a/clippy_lints/src/redundant_clone.rs b/clippy_lints/src/redundant_clone.rs index 37678fac1d21..9656ee64c818 100644 --- a/clippy_lints/src/redundant_clone.rs +++ b/clippy_lints/src/redundant_clone.rs @@ -199,79 +199,72 @@ impl<'tcx> LateLintPass<'tcx> for RedundantClone { (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.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", + String::new(), + 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"); } } } @@ -365,49 +358,97 @@ fn base_local_and_movability<'tcx>( (local, deref || field || slice) } -struct LocalUseVisitor { - used: (mir::Local, bool), - consumed_or_mutated: (mir::Local, bool), +#[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, + /// Whether the clone value is mutated. + clone_consumed_or_mutated: 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_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 }); + } - 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; + self.visit_terminator( + data.terminator(), + mir::Location { + block, + statement_index: statements.len(), + }, + ); } - if local == self.consumed_or_mutated.0 { - match ctx { - PlaceContext::NonMutatingUse(NonMutatingUseContext::Move) - | PlaceContext::MutatingUse(MutatingUseContext::Borrow) => { - self.consumed_or_mutated.1 = true; - }, - _ => {}, + 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`. @@ -623,4 +664,9 @@ impl PossibleBorrowerMap<'_, '_> { self.bitset.0 == self.bitset.1 } + + fn 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) + } } diff --git a/tests/ui/redundant_clone.fixed b/tests/ui/redundant_clone.fixed index ec309109ed52..f5da703cd1de 100644 --- a/tests/ui/redundant_clone.fixed +++ b/tests/ui/redundant_clone.fixed @@ -54,6 +54,7 @@ fn main() { not_consumed(); issue_5405(); manually_drop(); + clone_then_move_cloned(); } #[derive(Clone)] @@ -182,3 +183,26 @@ fn manually_drop() { Arc::from_raw(p); } } + +fn clone_then_move_cloned() { + // issue #5973 + let x = Some(String::new()); + // ok, x is moved while the clone is in use. + assert_eq!(x.clone(), None, "not equal {}", x.unwrap()); + + // issue #5595 + fn foo(_: &Alpha, _: F) {} + let x = Alpha; + // ok, data is moved while the clone is in use. + foo(&x.clone(), move || { + let _ = x; + }); + + // issue #6998 + struct S(String); + impl S { + fn m(&mut self) {} + } + let mut x = S(String::new()); + x.0.clone().chars().for_each(|_| x.m()); +} diff --git a/tests/ui/redundant_clone.rs b/tests/ui/redundant_clone.rs index b57027456e09..fd7f31a1cc5b 100644 --- a/tests/ui/redundant_clone.rs +++ b/tests/ui/redundant_clone.rs @@ -54,6 +54,7 @@ fn main() { not_consumed(); issue_5405(); manually_drop(); + clone_then_move_cloned(); } #[derive(Clone)] @@ -182,3 +183,26 @@ fn manually_drop() { Arc::from_raw(p); } } + +fn clone_then_move_cloned() { + // issue #5973 + let x = Some(String::new()); + // ok, x is moved while the clone is in use. + assert_eq!(x.clone(), None, "not equal {}", x.unwrap()); + + // issue #5595 + fn foo(_: &Alpha, _: F) {} + let x = Alpha; + // ok, data is moved while the clone is in use. + foo(&x.clone(), move || { + let _ = x; + }); + + // issue #6998 + struct S(String); + impl S { + fn m(&mut self) {} + } + let mut x = S(String::new()); + x.0.clone().chars().for_each(|_| x.m()); +} diff --git a/tests/ui/redundant_clone.stderr b/tests/ui/redundant_clone.stderr index 821e7934be8d..529a6de91e26 100644 --- a/tests/ui/redundant_clone.stderr +++ b/tests/ui/redundant_clone.stderr @@ -108,61 +108,61 @@ LL | let _t = tup.0.clone(); | ^^^^^ error: redundant clone - --> $DIR/redundant_clone.rs:62:25 + --> $DIR/redundant_clone.rs:63:25 | LL | if b { (a.clone(), a.clone()) } else { (Alpha, a) } | ^^^^^^^^ help: remove this | note: this value is dropped without further use - --> $DIR/redundant_clone.rs:62:24 + --> $DIR/redundant_clone.rs:63:24 | LL | if b { (a.clone(), a.clone()) } else { (Alpha, a) } | ^ error: redundant clone - --> $DIR/redundant_clone.rs:119:15 + --> $DIR/redundant_clone.rs:120:15 | LL | let _s = s.clone(); | ^^^^^^^^ help: remove this | note: this value is dropped without further use - --> $DIR/redundant_clone.rs:119:14 + --> $DIR/redundant_clone.rs:120:14 | LL | let _s = s.clone(); | ^ error: redundant clone - --> $DIR/redundant_clone.rs:120:15 + --> $DIR/redundant_clone.rs:121:15 | LL | let _t = t.clone(); | ^^^^^^^^ help: remove this | note: this value is dropped without further use - --> $DIR/redundant_clone.rs:120:14 + --> $DIR/redundant_clone.rs:121:14 | LL | let _t = t.clone(); | ^ error: redundant clone - --> $DIR/redundant_clone.rs:130:19 + --> $DIR/redundant_clone.rs:131:19 | LL | let _f = f.clone(); | ^^^^^^^^ help: remove this | note: this value is dropped without further use - --> $DIR/redundant_clone.rs:130:18 + --> $DIR/redundant_clone.rs:131:18 | LL | let _f = f.clone(); | ^ error: redundant clone - --> $DIR/redundant_clone.rs:142:14 + --> $DIR/redundant_clone.rs:143:14 | LL | let y = x.clone().join("matthias"); | ^^^^^^^^ help: remove this | note: cloned value is neither consumed nor mutated - --> $DIR/redundant_clone.rs:142:13 + --> $DIR/redundant_clone.rs:143:13 | LL | let y = x.clone().join("matthias"); | ^^^^^^^^^