diff options
| -rw-r--r-- | clippy_lints/src/assigning_clones.rs | 496 |
1 files changed, 176 insertions, 320 deletions
diff --git a/clippy_lints/src/assigning_clones.rs b/clippy_lints/src/assigning_clones.rs index 05ea74b0d53..84e3eb53cc0 100644 --- a/clippy_lints/src/assigning_clones.rs +++ b/clippy_lints/src/assigning_clones.rs @@ -1,18 +1,16 @@ use clippy_config::msrvs::{self, Msrv}; use clippy_utils::diagnostics::span_lint_and_then; -use clippy_utils::macros::HirNode; use clippy_utils::mir::{enclosing_mir, PossibleBorrowerMap}; use clippy_utils::sugg::Sugg; -use clippy_utils::{is_trait_method, local_is_initialized, path_to_local}; +use clippy_utils::{is_diag_trait_item, last_path_segment, local_is_initialized, path_to_local}; use rustc_errors::Applicability; use rustc_hir::{self as hir, Expr, ExprKind}; use rustc_lint::{LateContext, LateLintPass}; use rustc_middle::mir; use rustc_middle::ty::{self, Instance, Mutability}; use rustc_session::impl_lint_pass; -use rustc_span::def_id::DefId; use rustc_span::symbol::sym; -use rustc_span::{ExpnKind, Span, SyntaxContext}; +use rustc_span::{Span, SyntaxContext}; declare_clippy_lint! { /// ### What it does @@ -68,165 +66,82 @@ impl AssigningClones { impl_lint_pass!(AssigningClones => [ASSIGNING_CLONES]); impl<'tcx> LateLintPass<'tcx> for AssigningClones { - fn check_expr(&mut self, cx: &LateContext<'tcx>, assign_expr: &'tcx Expr<'_>) { - // Do not fire the lint in macros - let ctxt = assign_expr.span().ctxt(); - let expn_data = ctxt.outer_expn_data(); - match expn_data.kind { - ExpnKind::AstPass(_) | ExpnKind::Desugaring(_) | ExpnKind::Macro(..) => return, - ExpnKind::Root => {}, - } - - let ExprKind::Assign(lhs, rhs, _span) = assign_expr.kind else { - return; - }; - - let Some(call) = extract_call(cx, rhs) else { - return; - }; - - if is_ok_to_suggest(cx, lhs, &call, &self.msrv) { - suggest(cx, ctxt, assign_expr, lhs, &call); - } - } - - extract_msrv_attr!(LateContext); -} - -// Try to resolve the call to `Clone::clone` or `ToOwned::to_owned`. -fn extract_call<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> Option<CallCandidate<'tcx>> { - let fn_def_id = clippy_utils::fn_def_id(cx, expr)?; - - // Fast paths to only check method calls without arguments or function calls with a single argument - let (target, kind, resolved_method) = match expr.kind { - ExprKind::MethodCall(path, receiver, [], _span) => { - let args = cx.typeck_results().node_args(expr.hir_id); - - // If we could not resolve the method, don't apply the lint - let Ok(Some(resolved_method)) = Instance::resolve(cx.tcx, cx.param_env, fn_def_id, args) else { - return None; - }; - if is_trait_method(cx, expr, sym::Clone) && path.ident.name == sym::clone { - (TargetTrait::Clone, CallKind::MethodCall { receiver }, resolved_method) - } else if is_trait_method(cx, expr, sym::ToOwned) && path.ident.name.as_str() == "to_owned" { - (TargetTrait::ToOwned, CallKind::MethodCall { receiver }, resolved_method) - } else { - return None; + fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) { + if let ExprKind::Assign(lhs, rhs, _) = e.kind + && let typeck = cx.typeck_results() + && let (call_kind, fn_name, fn_id, fn_arg, fn_gen_args) = match rhs.kind { + ExprKind::Call(f, [arg]) + if let ExprKind::Path(fn_path) = &f.kind + && let Some(id) = typeck.qpath_res(fn_path, f.hir_id).opt_def_id() => + { + (CallKind::Ufcs, last_path_segment(fn_path).ident.name, id, arg, typeck.node_args(f.hir_id)) + }, + ExprKind::MethodCall(name, recv, [], _) if let Some(id) = typeck.type_dependent_def_id(rhs.hir_id) => { + (CallKind::Method, name.ident.name, id, recv, typeck.node_args(rhs.hir_id)) + }, + _ => return, } - }, - ExprKind::Call(function, [arg]) => { - let kind = cx.typeck_results().node_type(function.hir_id).kind(); - - // If we could not resolve the method, don't apply the lint - let Ok(Some(resolved_method)) = (match kind { - ty::FnDef(_, args) => Instance::resolve(cx.tcx, cx.param_env, fn_def_id, args), - _ => Ok(None), - }) else { - return None; - }; - if cx.tcx.is_diagnostic_item(sym::to_owned_method, fn_def_id) { - ( - TargetTrait::ToOwned, - CallKind::FunctionCall { self_arg: arg }, - resolved_method, - ) - } else if let Some(trait_did) = cx.tcx.trait_of_item(fn_def_id) - && cx.tcx.is_diagnostic_item(sym::Clone, trait_did) - { - ( - TargetTrait::Clone, - CallKind::FunctionCall { self_arg: arg }, - resolved_method, - ) - } else { - return None; + && let ctxt = e.span.ctxt() + // Don't lint in macros. + && ctxt.is_root() + && let which_trait = match fn_name { + sym::clone if is_diag_trait_item(cx, fn_id, sym::Clone) => CloneTrait::Clone, + _ if fn_name.as_str() == "to_owned" + && is_diag_trait_item(cx, fn_id, sym::ToOwned) + && self.msrv.meets(msrvs::CLONE_INTO) => + { + CloneTrait::ToOwned + }, + _ => return, } - }, - _ => return None, - }; - - Some(CallCandidate { - span: expr.span, - target, - kind, - method_def_id: resolved_method.def_id(), - }) -} - -// Return true if we find that the called method has a custom implementation and isn't derived or -// provided by default by the corresponding trait. -fn is_ok_to_suggest<'tcx>(cx: &LateContext<'tcx>, lhs: &Expr<'tcx>, call: &CallCandidate<'tcx>, msrv: &Msrv) -> bool { - // For calls to .to_owned we suggest using .clone_into(), which was only stablilized in 1.63. - // If the current MSRV is below that, don't suggest the lint. - if !msrv.meets(msrvs::CLONE_INTO) && matches!(call.target, TargetTrait::ToOwned) { - return false; - } - - // If the left-hand side is a local variable, it might be uninitialized at this point. - // In that case we do not want to suggest the lint. - if let Some(local) = path_to_local(lhs) { - // TODO: This check currently bails if the local variable has no initializer. - // That is overly conservative - the lint should fire even if there was no initializer, - // but the variable has been initialized before `lhs` was evaluated. - if !local_is_initialized(cx, local) { - return false; - } - } - - let Some(impl_block) = cx.tcx.impl_of_method(call.method_def_id) else { - return false; - }; - - // If the method implementation comes from #[derive(Clone)], then don't suggest the lint. - // Automatically generated Clone impls do not currently override `clone_from`. - // See e.g. https://github.com/rust-lang/rust/pull/98445#issuecomment-1190681305 for more details. - if cx.tcx.is_builtin_derived(impl_block) { - return false; - } - - // If the call expression is inside an impl block that contains the method invoked by the - // call expression, we bail out to avoid suggesting something that could result in endless - // recursion. - if let Some(local_block_id) = impl_block.as_local() - && let Some(block) = cx.tcx.hir_node_by_def_id(local_block_id).as_owner() - { - let impl_block_owner = block.def_id(); - if cx - .tcx - .hir() - .parent_id_iter(lhs.hir_id) - .any(|parent| parent.owner == impl_block_owner) + && let Ok(Some(resolved_fn)) = Instance::resolve(cx.tcx, cx.param_env, fn_id, fn_gen_args) + // TODO: This check currently bails if the local variable has no initializer. + // That is overly conservative - the lint should fire even if there was no initializer, + // but the variable has been initialized before `lhs` was evaluated. + && path_to_local(lhs).map_or(true, |lhs| local_is_initialized(cx, lhs)) + && let Some(resolved_impl) = cx.tcx.impl_of_method(resolved_fn.def_id()) + // Derived forms don't implement `clone_from`/`clone_into`. + // See https://github.com/rust-lang/rust/pull/98445#issuecomment-1190681305 + && !cx.tcx.is_builtin_derived(resolved_impl) + // Don't suggest calling a function we're implementing. + && resolved_impl.as_local().map_or(true, |block_id| { + cx.tcx.hir().parent_owner_iter(e.hir_id).all(|(id, _)| id.def_id != block_id) + }) + && let resolved_assoc_items = cx.tcx.associated_items(resolved_impl) + // Only suggest if `clone_from`/`clone_into` is explicitly implemented + && resolved_assoc_items.in_definition_order().any(|assoc| + match which_trait { + CloneTrait::Clone => assoc.name == sym::clone_from, + CloneTrait::ToOwned => assoc.name.as_str() == "clone_into", + } + ) + && !clone_source_borrows_from_dest(cx, lhs, rhs.span) { - return false; + span_lint_and_then( + cx, + ASSIGNING_CLONES, + e.span, + match which_trait { + CloneTrait::Clone => "assigning the result of `Clone::clone()` may be inefficient", + CloneTrait::ToOwned => "assigning the result of `ToOwned::to_owned()` may be inefficient", + }, + |diag| { + let mut app = Applicability::Unspecified; + diag.span_suggestion( + e.span, + match which_trait { + CloneTrait::Clone => "use `clone_from()`", + CloneTrait::ToOwned => "use `clone_into()`", + }, + build_sugg(cx, ctxt, lhs, fn_arg, which_trait, call_kind, &mut app), + app, + ); + }, + ); } } - // Find the function for which we want to check that it is implemented. - let provided_fn = match call.target { - TargetTrait::Clone => cx.tcx.get_diagnostic_item(sym::Clone).and_then(|clone| { - cx.tcx - .provided_trait_methods(clone) - .find(|item| item.name == sym::clone_from) - }), - TargetTrait::ToOwned => cx.tcx.get_diagnostic_item(sym::ToOwned).and_then(|to_owned| { - cx.tcx - .provided_trait_methods(to_owned) - .find(|item| item.name.as_str() == "clone_into") - }), - }; - let Some(provided_fn) = provided_fn else { - return false; - }; - - if clone_source_borrows_from_dest(cx, lhs, call.span) { - return false; - } - - // Now take a look if the impl block defines an implementation for the method that we're interested - // in. If not, then we're using a default implementation, which is not interesting, so we will - // not suggest the lint. - let implemented_fns = cx.tcx.impl_item_implementor_ids(impl_block); - implemented_fns.contains_key(&provided_fn.def_id) + extract_msrv_attr!(LateContext); } /// Checks if the data being cloned borrows from the place that is being assigned to: @@ -239,16 +154,6 @@ fn is_ok_to_suggest<'tcx>(cx: &LateContext<'tcx>, lhs: &Expr<'tcx>, call: &CallC /// /// This cannot be written `s2.clone_into(&mut s)` because it has conflicting borrows. fn clone_source_borrows_from_dest(cx: &LateContext<'_>, lhs: &Expr<'_>, call_span: Span) -> bool { - /// If this basic block only exists to drop a local as part of an assignment, returns its - /// successor. Otherwise returns the basic block that was passed in. - fn skip_drop_block(mir: &mir::Body<'_>, bb: mir::BasicBlock) -> mir::BasicBlock { - if let mir::TerminatorKind::Drop { target, .. } = mir.basic_blocks[bb].terminator().kind { - target - } else { - bb - } - } - let Some(mir) = enclosing_mir(cx.tcx, lhs.hir_id) else { return false; }; @@ -267,172 +172,123 @@ fn clone_source_borrows_from_dest(cx: &LateContext<'_>, lhs: &Expr<'_>, call_spa // // bb2: // s = s_temp - for bb in mir.basic_blocks.iter() { - let terminator = bb.terminator(); - - // Look for the to_owned/clone call. - if terminator.source_info.span != call_span { - continue; + if let Some(terminator) = mir.basic_blocks.iter() + .map(mir::BasicBlockData::terminator) + .find(|term| term.source_info.span == call_span) + && let mir::TerminatorKind::Call { ref args, target: Some(assign_bb), .. } = terminator.kind + && let [source] = &**args + && let mir::Operand::Move(source) = &source.node + && let assign_bb = &mir.basic_blocks[assign_bb] + && let assign_bb = match assign_bb.terminator().kind { + // Skip the drop of the assignment's destination. + mir::TerminatorKind::Drop { target, .. } => &mir.basic_blocks[target], + _ => assign_bb, } - - if let mir::TerminatorKind::Call { ref args, target: Some(assign_bb), .. } = terminator.kind - && let [source] = &**args - && let mir::Operand::Move(source) = &source.node - && let assign_bb = skip_drop_block(mir, assign_bb) - // Skip any storage statements as they are just noise - && let Some(assignment) = mir.basic_blocks[assign_bb].statements - .iter() - .find(|stmt| { - !matches!(stmt.kind, mir::StatementKind::StorageDead(_) | mir::StatementKind::StorageLive(_)) - }) - && let mir::StatementKind::Assign(box (borrowed, _)) = &assignment.kind - && let Some(borrowers) = borrow_map.get(&borrowed.local) - && borrowers.contains(source.local) - { - return true; - } - - return false; + // Skip any storage statements as they are just noise + && let Some(assignment) = assign_bb.statements + .iter() + .find(|stmt| { + !matches!(stmt.kind, mir::StatementKind::StorageDead(_) | mir::StatementKind::StorageLive(_)) + }) + && let mir::StatementKind::Assign(box (borrowed, _)) = &assignment.kind + && let Some(borrowers) = borrow_map.get(&borrowed.local) + { + borrowers.contains(source.local) + } else { + false } - false -} - -fn suggest<'tcx>( - cx: &LateContext<'tcx>, - ctxt: SyntaxContext, - assign_expr: &Expr<'tcx>, - lhs: &Expr<'tcx>, - call: &CallCandidate<'tcx>, -) { - span_lint_and_then(cx, ASSIGNING_CLONES, assign_expr.span, call.message(), |diag| { - let mut applicability = Applicability::Unspecified; - - diag.span_suggestion( - assign_expr.span, - call.suggestion_msg(), - call.suggested_replacement(cx, ctxt, lhs, &mut applicability), - applicability, - ); - }); } -#[derive(Copy, Clone, Debug)] -enum CallKind<'tcx> { - MethodCall { receiver: &'tcx Expr<'tcx> }, - FunctionCall { self_arg: &'tcx Expr<'tcx> }, -} - -#[derive(Copy, Clone, Debug)] -enum TargetTrait { +#[derive(Clone, Copy)] +enum CloneTrait { Clone, ToOwned, } -#[derive(Debug)] -struct CallCandidate<'tcx> { - span: Span, - target: TargetTrait, - kind: CallKind<'tcx>, - // DefId of the called method from an impl block that implements the target trait - method_def_id: DefId, +#[derive(Copy, Clone)] +enum CallKind { + Ufcs, + Method, } -impl<'tcx> CallCandidate<'tcx> { - #[inline] - fn message(&self) -> &'static str { - match self.target { - TargetTrait::Clone => "assigning the result of `Clone::clone()` may be inefficient", - TargetTrait::ToOwned => "assigning the result of `ToOwned::to_owned()` may be inefficient", - } - } - - #[inline] - fn suggestion_msg(&self) -> &'static str { - match self.target { - TargetTrait::Clone => "use `clone_from()`", - TargetTrait::ToOwned => "use `clone_into()`", - } - } - - fn suggested_replacement( - &self, - cx: &LateContext<'tcx>, - ctxt: SyntaxContext, - lhs: &Expr<'tcx>, - applicability: &mut Applicability, - ) -> String { - match self.target { - TargetTrait::Clone => { - match self.kind { - CallKind::MethodCall { receiver } => { - let receiver_sugg = if let ExprKind::Unary(hir::UnOp::Deref, ref_expr) = lhs.kind { - // `*lhs = self_expr.clone();` -> `lhs.clone_from(self_expr)` - Sugg::hir_with_applicability(cx, ref_expr, "_", applicability) - } else { - // `lhs = self_expr.clone();` -> `lhs.clone_from(self_expr)` - Sugg::hir_with_applicability(cx, lhs, "_", applicability) - } - .maybe_par(); - - // Determine whether we need to reference the argument to clone_from(). - let clone_receiver_type = cx.typeck_results().expr_ty(receiver); - let clone_receiver_adj_type = cx.typeck_results().expr_ty_adjusted(receiver); - let mut arg_sugg = Sugg::hir_with_context(cx, receiver, ctxt, "_", applicability); - if clone_receiver_type != clone_receiver_adj_type { - // The receiver may have been a value type, so we need to add an `&` to - // be sure the argument to clone_from will be a reference. - arg_sugg = arg_sugg.addr(); - }; - - format!("{receiver_sugg}.clone_from({arg_sugg})") - }, - CallKind::FunctionCall { self_arg, .. } => { - let self_sugg = if let ExprKind::Unary(hir::UnOp::Deref, ref_expr) = lhs.kind { - // `*lhs = Clone::clone(self_expr);` -> `Clone::clone_from(lhs, self_expr)` - Sugg::hir_with_applicability(cx, ref_expr, "_", applicability) - } else { - // `lhs = Clone::clone(self_expr);` -> `Clone::clone_from(&mut lhs, self_expr)` - Sugg::hir_with_applicability(cx, lhs, "_", applicability).mut_addr() - }; - // The RHS had to be exactly correct before the call, there is no auto-deref for function calls. - let rhs_sugg = Sugg::hir_with_context(cx, self_arg, ctxt, "_", applicability); - - format!("Clone::clone_from({self_sugg}, {rhs_sugg})") - }, - } - }, - TargetTrait::ToOwned => { - let rhs_sugg = if let ExprKind::Unary(hir::UnOp::Deref, ref_expr) = lhs.kind { - // `*lhs = rhs.to_owned()` -> `rhs.clone_into(lhs)` - // `*lhs = ToOwned::to_owned(rhs)` -> `ToOwned::clone_into(rhs, lhs)` - let sugg = Sugg::hir_with_applicability(cx, ref_expr, "_", applicability).maybe_par(); - let inner_type = cx.typeck_results().expr_ty(ref_expr); - // If after unwrapping the dereference, the type is not a mutable reference, we add &mut to make it - // deref to a mutable reference. - if matches!(inner_type.kind(), ty::Ref(_, _, Mutability::Mut)) { - sugg +fn build_sugg<'tcx>( + cx: &LateContext<'tcx>, + ctxt: SyntaxContext, + lhs: &'tcx Expr<'_>, + fn_arg: &'tcx Expr<'_>, + which_trait: CloneTrait, + call_kind: CallKind, + app: &mut Applicability, +) -> String { + match which_trait { + CloneTrait::Clone => { + match call_kind { + CallKind::Method => { + let receiver_sugg = if let ExprKind::Unary(hir::UnOp::Deref, ref_expr) = lhs.kind { + // `*lhs = self_expr.clone();` -> `lhs.clone_from(self_expr)` + Sugg::hir_with_applicability(cx, ref_expr, "_", app) } else { - sugg.mut_addr() + // `lhs = self_expr.clone();` -> `lhs.clone_from(self_expr)` + Sugg::hir_with_applicability(cx, lhs, "_", app) } + .maybe_par(); + + // Determine whether we need to reference the argument to clone_from(). + let clone_receiver_type = cx.typeck_results().expr_ty(fn_arg); + let clone_receiver_adj_type = cx.typeck_results().expr_ty_adjusted(fn_arg); + let mut arg_sugg = Sugg::hir_with_context(cx, fn_arg, ctxt, "_", app); + if clone_receiver_type != clone_receiver_adj_type { + // The receiver may have been a value type, so we need to add an `&` to + // be sure the argument to clone_from will be a reference. + arg_sugg = arg_sugg.addr(); + }; + + format!("{receiver_sugg}.clone_from({arg_sugg})") + }, + CallKind::Ufcs => { + let self_sugg = if let ExprKind::Unary(hir::UnOp::Deref, ref_expr) = lhs.kind { + // `*lhs = Clone::clone(self_expr);` -> `Clone::clone_from(lhs, self_expr)` + Sugg::hir_with_applicability(cx, ref_expr, "_", app) + } else { + // `lhs = Clone::clone(self_expr);` -> `Clone::clone_from(&mut lhs, self_expr)` + Sugg::hir_with_applicability(cx, lhs, "_", app).mut_addr() + }; + // The RHS had to be exactly correct before the call, there is no auto-deref for function calls. + let rhs_sugg = Sugg::hir_with_context(cx, fn_arg, ctxt, "_", app); + + format!("Clone::clone_from({self_sugg}, {rhs_sugg})") + }, + } + }, + CloneTrait::ToOwned => { + let rhs_sugg = if let ExprKind::Unary(hir::UnOp::Deref, ref_expr) = lhs.kind { + // `*lhs = rhs.to_owned()` -> `rhs.clone_into(lhs)` + // `*lhs = ToOwned::to_owned(rhs)` -> `ToOwned::clone_into(rhs, lhs)` + let sugg = Sugg::hir_with_applicability(cx, ref_expr, "_", app).maybe_par(); + let inner_type = cx.typeck_results().expr_ty(ref_expr); + // If after unwrapping the dereference, the type is not a mutable reference, we add &mut to make it + // deref to a mutable reference. + if matches!(inner_type.kind(), ty::Ref(_, _, Mutability::Mut)) { + sugg } else { - // `lhs = rhs.to_owned()` -> `rhs.clone_into(&mut lhs)` - // `lhs = ToOwned::to_owned(rhs)` -> `ToOwned::clone_into(rhs, &mut lhs)` - Sugg::hir_with_applicability(cx, lhs, "_", applicability) - .maybe_par() - .mut_addr() - }; - - match self.kind { - CallKind::MethodCall { receiver } => { - let receiver_sugg = Sugg::hir_with_context(cx, receiver, ctxt, "_", applicability); - format!("{receiver_sugg}.clone_into({rhs_sugg})") - }, - CallKind::FunctionCall { self_arg, .. } => { - let self_sugg = Sugg::hir_with_context(cx, self_arg, ctxt, "_", applicability); - format!("ToOwned::clone_into({self_sugg}, {rhs_sugg})") - }, + sugg.mut_addr() } - }, - } + } else { + // `lhs = rhs.to_owned()` -> `rhs.clone_into(&mut lhs)` + // `lhs = ToOwned::to_owned(rhs)` -> `ToOwned::clone_into(rhs, &mut lhs)` + Sugg::hir_with_applicability(cx, lhs, "_", app).maybe_par().mut_addr() + }; + + match call_kind { + CallKind::Method => { + let receiver_sugg = Sugg::hir_with_context(cx, fn_arg, ctxt, "_", app); + format!("{receiver_sugg}.clone_into({rhs_sugg})") + }, + CallKind::Ufcs => { + let self_sugg = Sugg::hir_with_context(cx, fn_arg, ctxt, "_", app); + format!("ToOwned::clone_into({self_sugg}, {rhs_sugg})") + }, + } + }, } } |