| use super::implicit_clone::is_clone_like; |
| use super::unnecessary_iter_cloned::{self, is_into_iter}; |
| use clippy_utils::diagnostics::span_lint_and_sugg; |
| use clippy_utils::msrvs::{self, Msrv}; |
| use clippy_utils::source::snippet_opt; |
| use clippy_utils::ty::{get_iterator_item_ty, implements_trait, is_copy, peel_mid_ty_refs}; |
| use clippy_utils::visitors::find_all_ret_expressions; |
| use clippy_utils::{fn_def_id, get_parent_expr, is_diag_item_method, is_diag_trait_item, return_ty}; |
| use rustc_errors::Applicability; |
| use rustc_hir::{def_id::DefId, BorrowKind, Expr, ExprKind, ItemKind, Node}; |
| use rustc_hir_typeck::{FnCtxt, Inherited}; |
| use rustc_infer::infer::TyCtxtInferExt; |
| use rustc_lint::LateContext; |
| use rustc_middle::mir::Mutability; |
| use rustc_middle::ty::adjustment::{Adjust, Adjustment, OverloadedDeref}; |
| use rustc_middle::ty::subst::{GenericArg, GenericArgKind, SubstsRef}; |
| use rustc_middle::ty::{self, Clause, EarlyBinder, ParamTy, PredicateKind, ProjectionPredicate, TraitPredicate, Ty}; |
| use rustc_span::{sym, Symbol}; |
| use rustc_trait_selection::traits::{query::evaluate_obligation::InferCtxtExt as _, Obligation, ObligationCause}; |
| |
| use super::UNNECESSARY_TO_OWNED; |
| |
| pub fn check<'tcx>( |
| cx: &LateContext<'tcx>, |
| expr: &'tcx Expr<'tcx>, |
| method_name: Symbol, |
| receiver: &'tcx Expr<'_>, |
| args: &'tcx [Expr<'_>], |
| msrv: &Msrv, |
| ) { |
| if_chain! { |
| if let Some(method_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id); |
| if args.is_empty(); |
| then { |
| if is_cloned_or_copied(cx, method_name, method_def_id) { |
| unnecessary_iter_cloned::check(cx, expr, method_name, receiver); |
| } else if is_to_owned_like(cx, expr, method_name, method_def_id) { |
| // At this point, we know the call is of a `to_owned`-like function. The functions |
| // `check_addr_of_expr` and `check_call_arg` determine whether the call is unnecessary |
| // based on its context, that is, whether it is a referent in an `AddrOf` expression, an |
| // argument in a `into_iter` call, or an argument in the call of some other function. |
| if check_addr_of_expr(cx, expr, method_name, method_def_id, receiver) { |
| return; |
| } |
| if check_into_iter_call_arg(cx, expr, method_name, receiver, msrv) { |
| return; |
| } |
| check_other_call_arg(cx, expr, method_name, receiver); |
| } |
| } |
| } |
| } |
| |
| /// Checks whether `expr` is a referent in an `AddrOf` expression and, if so, determines whether its |
| /// call of a `to_owned`-like function is unnecessary. |
| #[allow(clippy::too_many_lines)] |
| fn check_addr_of_expr( |
| cx: &LateContext<'_>, |
| expr: &Expr<'_>, |
| method_name: Symbol, |
| method_def_id: DefId, |
| receiver: &Expr<'_>, |
| ) -> bool { |
| if_chain! { |
| if let Some(parent) = get_parent_expr(cx, expr); |
| if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, _) = parent.kind; |
| let adjustments = cx.typeck_results().expr_adjustments(parent).iter().collect::<Vec<_>>(); |
| if let |
| // For matching uses of `Cow::from` |
| [ |
| Adjustment { |
| kind: Adjust::Deref(None), |
| target: referent_ty, |
| }, |
| Adjustment { |
| kind: Adjust::Borrow(_), |
| target: target_ty, |
| }, |
| ] |
| // For matching uses of arrays |
| | [ |
| Adjustment { |
| kind: Adjust::Deref(None), |
| target: referent_ty, |
| }, |
| Adjustment { |
| kind: Adjust::Borrow(_), |
| .. |
| }, |
| Adjustment { |
| kind: Adjust::Pointer(_), |
| target: target_ty, |
| }, |
| ] |
| // For matching everything else |
| | [ |
| Adjustment { |
| kind: Adjust::Deref(None), |
| target: referent_ty, |
| }, |
| Adjustment { |
| kind: Adjust::Deref(Some(OverloadedDeref { .. })), |
| .. |
| }, |
| Adjustment { |
| kind: Adjust::Borrow(_), |
| target: target_ty, |
| }, |
| ] = adjustments[..]; |
| let receiver_ty = cx.typeck_results().expr_ty(receiver); |
| let (target_ty, n_target_refs) = peel_mid_ty_refs(*target_ty); |
| let (receiver_ty, n_receiver_refs) = peel_mid_ty_refs(receiver_ty); |
| // Only flag cases satisfying at least one of the following three conditions: |
| // * the referent and receiver types are distinct |
| // * the referent/receiver type is a copyable array |
| // * the method is `Cow::into_owned` |
| // This restriction is to ensure there is no overlap between `redundant_clone` and this |
| // lint. It also avoids the following false positive: |
| // https://github.com/rust-lang/rust-clippy/issues/8759 |
| // Arrays are a bit of a corner case. Non-copyable arrays are handled by |
| // `redundant_clone`, but copyable arrays are not. |
| if *referent_ty != receiver_ty |
| || (matches!(referent_ty.kind(), ty::Array(..)) && is_copy(cx, *referent_ty)) |
| || is_cow_into_owned(cx, method_name, method_def_id); |
| if let Some(receiver_snippet) = snippet_opt(cx, receiver.span); |
| then { |
| if receiver_ty == target_ty && n_target_refs >= n_receiver_refs { |
| span_lint_and_sugg( |
| cx, |
| UNNECESSARY_TO_OWNED, |
| parent.span, |
| &format!("unnecessary use of `{method_name}`"), |
| "use", |
| format!( |
| "{:&>width$}{receiver_snippet}", |
| "", |
| width = n_target_refs - n_receiver_refs |
| ), |
| Applicability::MachineApplicable, |
| ); |
| return true; |
| } |
| if_chain! { |
| if let Some(deref_trait_id) = cx.tcx.get_diagnostic_item(sym::Deref); |
| if implements_trait(cx, receiver_ty, deref_trait_id, &[]); |
| if cx.get_associated_type(receiver_ty, deref_trait_id, "Target") == Some(target_ty); |
| then { |
| if n_receiver_refs > 0 { |
| span_lint_and_sugg( |
| cx, |
| UNNECESSARY_TO_OWNED, |
| parent.span, |
| &format!("unnecessary use of `{method_name}`"), |
| "use", |
| receiver_snippet, |
| Applicability::MachineApplicable, |
| ); |
| } else { |
| span_lint_and_sugg( |
| cx, |
| UNNECESSARY_TO_OWNED, |
| expr.span.with_lo(receiver.span.hi()), |
| &format!("unnecessary use of `{method_name}`"), |
| "remove this", |
| String::new(), |
| Applicability::MachineApplicable, |
| ); |
| } |
| return true; |
| } |
| } |
| if_chain! { |
| if let Some(as_ref_trait_id) = cx.tcx.get_diagnostic_item(sym::AsRef); |
| if implements_trait(cx, receiver_ty, as_ref_trait_id, &[GenericArg::from(target_ty)]); |
| then { |
| span_lint_and_sugg( |
| cx, |
| UNNECESSARY_TO_OWNED, |
| parent.span, |
| &format!("unnecessary use of `{method_name}`"), |
| "use", |
| format!("{receiver_snippet}.as_ref()"), |
| Applicability::MachineApplicable, |
| ); |
| return true; |
| } |
| } |
| } |
| } |
| false |
| } |
| |
| /// Checks whether `expr` is an argument in an `into_iter` call and, if so, determines whether its |
| /// call of a `to_owned`-like function is unnecessary. |
| fn check_into_iter_call_arg( |
| cx: &LateContext<'_>, |
| expr: &Expr<'_>, |
| method_name: Symbol, |
| receiver: &Expr<'_>, |
| msrv: &Msrv, |
| ) -> bool { |
| if_chain! { |
| if let Some(parent) = get_parent_expr(cx, expr); |
| if let Some(callee_def_id) = fn_def_id(cx, parent); |
| if is_into_iter(cx, callee_def_id); |
| if let Some(iterator_trait_id) = cx.tcx.get_diagnostic_item(sym::Iterator); |
| let parent_ty = cx.typeck_results().expr_ty(parent); |
| if implements_trait(cx, parent_ty, iterator_trait_id, &[]); |
| if let Some(item_ty) = get_iterator_item_ty(cx, parent_ty); |
| if let Some(receiver_snippet) = snippet_opt(cx, receiver.span); |
| then { |
| if unnecessary_iter_cloned::check_for_loop_iter(cx, parent, method_name, receiver, true) { |
| return true; |
| } |
| let cloned_or_copied = if is_copy(cx, item_ty) && msrv.meets(msrvs::ITERATOR_COPIED) { |
| "copied" |
| } else { |
| "cloned" |
| }; |
| // The next suggestion may be incorrect because the removal of the `to_owned`-like |
| // function could cause the iterator to hold a reference to a resource that is used |
| // mutably. See https://github.com/rust-lang/rust-clippy/issues/8148. |
| span_lint_and_sugg( |
| cx, |
| UNNECESSARY_TO_OWNED, |
| parent.span, |
| &format!("unnecessary use of `{method_name}`"), |
| "use", |
| format!("{receiver_snippet}.iter().{cloned_or_copied}()"), |
| Applicability::MaybeIncorrect, |
| ); |
| return true; |
| } |
| } |
| false |
| } |
| |
| /// Checks whether `expr` is an argument in a function call and, if so, determines whether its call |
| /// of a `to_owned`-like function is unnecessary. |
| fn check_other_call_arg<'tcx>( |
| cx: &LateContext<'tcx>, |
| expr: &'tcx Expr<'tcx>, |
| method_name: Symbol, |
| receiver: &'tcx Expr<'tcx>, |
| ) -> bool { |
| if_chain! { |
| if let Some((maybe_call, maybe_arg)) = skip_addr_of_ancestors(cx, expr); |
| if let Some((callee_def_id, _, recv, call_args)) = get_callee_substs_and_args(cx, maybe_call); |
| let fn_sig = cx.tcx.fn_sig(callee_def_id).subst_identity().skip_binder(); |
| if let Some(i) = recv.into_iter().chain(call_args).position(|arg| arg.hir_id == maybe_arg.hir_id); |
| if let Some(input) = fn_sig.inputs().get(i); |
| let (input, n_refs) = peel_mid_ty_refs(*input); |
| if let (trait_predicates, _) = get_input_traits_and_projections(cx, callee_def_id, input); |
| if let Some(sized_def_id) = cx.tcx.lang_items().sized_trait(); |
| if let [trait_predicate] = trait_predicates |
| .iter() |
| .filter(|trait_predicate| trait_predicate.def_id() != sized_def_id) |
| .collect::<Vec<_>>()[..]; |
| if let Some(deref_trait_id) = cx.tcx.get_diagnostic_item(sym::Deref); |
| if let Some(as_ref_trait_id) = cx.tcx.get_diagnostic_item(sym::AsRef); |
| if trait_predicate.def_id() == deref_trait_id || trait_predicate.def_id() == as_ref_trait_id; |
| let receiver_ty = cx.typeck_results().expr_ty(receiver); |
| // We can't add an `&` when the trait is `Deref` because `Target = &T` won't match |
| // `Target = T`. |
| if let Some((n_refs, receiver_ty)) = if n_refs > 0 || is_copy(cx, receiver_ty) { |
| Some((n_refs, receiver_ty)) |
| } else if trait_predicate.def_id() != deref_trait_id { |
| Some((1, cx.tcx.mk_ref( |
| cx.tcx.lifetimes.re_erased, |
| ty::TypeAndMut { |
| ty: receiver_ty, |
| mutbl: Mutability::Not, |
| }, |
| ))) |
| } else { |
| None |
| }; |
| if can_change_type(cx, maybe_arg, receiver_ty); |
| if let Some(receiver_snippet) = snippet_opt(cx, receiver.span); |
| then { |
| span_lint_and_sugg( |
| cx, |
| UNNECESSARY_TO_OWNED, |
| maybe_arg.span, |
| &format!("unnecessary use of `{method_name}`"), |
| "use", |
| format!("{:&>n_refs$}{receiver_snippet}", ""), |
| Applicability::MachineApplicable, |
| ); |
| return true; |
| } |
| } |
| false |
| } |
| |
| /// Walks an expression's ancestors until it finds a non-`AddrOf` expression. Returns the first such |
| /// expression found (if any) along with the immediately prior expression. |
| fn skip_addr_of_ancestors<'tcx>( |
| cx: &LateContext<'tcx>, |
| mut expr: &'tcx Expr<'tcx>, |
| ) -> Option<(&'tcx Expr<'tcx>, &'tcx Expr<'tcx>)> { |
| while let Some(parent) = get_parent_expr(cx, expr) { |
| if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, _) = parent.kind { |
| expr = parent; |
| } else { |
| return Some((parent, expr)); |
| } |
| } |
| None |
| } |
| |
| /// Checks whether an expression is a function or method call and, if so, returns its `DefId`, |
| /// `Substs`, and arguments. |
| fn get_callee_substs_and_args<'tcx>( |
| cx: &LateContext<'tcx>, |
| expr: &'tcx Expr<'tcx>, |
| ) -> Option<(DefId, SubstsRef<'tcx>, Option<&'tcx Expr<'tcx>>, &'tcx [Expr<'tcx>])> { |
| if_chain! { |
| if let ExprKind::Call(callee, args) = expr.kind; |
| let callee_ty = cx.typeck_results().expr_ty(callee); |
| if let ty::FnDef(callee_def_id, _) = callee_ty.kind(); |
| then { |
| let substs = cx.typeck_results().node_substs(callee.hir_id); |
| return Some((*callee_def_id, substs, None, args)); |
| } |
| } |
| if_chain! { |
| if let ExprKind::MethodCall(_, recv, args, _) = expr.kind; |
| if let Some(method_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id); |
| then { |
| let substs = cx.typeck_results().node_substs(expr.hir_id); |
| return Some((method_def_id, substs, Some(recv), args)); |
| } |
| } |
| None |
| } |
| |
| /// Returns the `TraitPredicate`s and `ProjectionPredicate`s for a function's input type. |
| fn get_input_traits_and_projections<'tcx>( |
| cx: &LateContext<'tcx>, |
| callee_def_id: DefId, |
| input: Ty<'tcx>, |
| ) -> (Vec<TraitPredicate<'tcx>>, Vec<ProjectionPredicate<'tcx>>) { |
| let mut trait_predicates = Vec::new(); |
| let mut projection_predicates = Vec::new(); |
| for predicate in cx.tcx.param_env(callee_def_id).caller_bounds() { |
| match predicate.kind().skip_binder() { |
| PredicateKind::Clause(Clause::Trait(trait_predicate)) => { |
| if trait_predicate.trait_ref.self_ty() == input { |
| trait_predicates.push(trait_predicate); |
| } |
| }, |
| PredicateKind::Clause(Clause::Projection(projection_predicate)) => { |
| if projection_predicate.projection_ty.self_ty() == input { |
| projection_predicates.push(projection_predicate); |
| } |
| }, |
| _ => {}, |
| } |
| } |
| (trait_predicates, projection_predicates) |
| } |
| |
| fn can_change_type<'a>(cx: &LateContext<'a>, mut expr: &'a Expr<'a>, mut ty: Ty<'a>) -> bool { |
| for (_, node) in cx.tcx.hir().parent_iter(expr.hir_id) { |
| match node { |
| Node::Stmt(_) => return true, |
| Node::Block(..) => continue, |
| Node::Item(item) => { |
| if let ItemKind::Fn(_, _, body_id) = &item.kind |
| && let output_ty = return_ty(cx, item.owner_id) |
| && let inherited = Inherited::new(cx.tcx, item.owner_id.def_id) |
| && let fn_ctxt = FnCtxt::new(&inherited, cx.param_env, item.owner_id.def_id) |
| && fn_ctxt.can_coerce(ty, output_ty) |
| { |
| if has_lifetime(output_ty) && has_lifetime(ty) { |
| return false; |
| } |
| let body = cx.tcx.hir().body(*body_id); |
| let body_expr = &body.value; |
| let mut count = 0; |
| return find_all_ret_expressions(cx, body_expr, |_| { count += 1; count <= 1 }); |
| } |
| } |
| Node::Expr(parent_expr) => { |
| if let Some((callee_def_id, call_substs, recv, call_args)) = get_callee_substs_and_args(cx, parent_expr) |
| { |
| // FIXME: the `subst_identity()` below seems incorrect, since we eventually |
| // call `tcx.try_subst_and_normalize_erasing_regions` further down |
| // (i.e., we are explicitly not in the identity context). |
| let fn_sig = cx.tcx.fn_sig(callee_def_id).subst_identity().skip_binder(); |
| if let Some(arg_index) = recv.into_iter().chain(call_args).position(|arg| arg.hir_id == expr.hir_id) |
| && let Some(param_ty) = fn_sig.inputs().get(arg_index) |
| && let ty::Param(ParamTy { index: param_index , ..}) = param_ty.kind() |
| // https://github.com/rust-lang/rust-clippy/issues/9504 and https://github.com/rust-lang/rust-clippy/issues/10021 |
| && (*param_index as usize) < call_substs.len() |
| { |
| if fn_sig |
| .inputs() |
| .iter() |
| .enumerate() |
| .filter(|(i, _)| *i != arg_index) |
| .any(|(_, ty)| ty.contains(*param_ty)) |
| { |
| return false; |
| } |
| |
| let mut trait_predicates = cx.tcx.param_env(callee_def_id) |
| .caller_bounds().iter().filter(|predicate| { |
| if let PredicateKind::Clause(Clause::Trait(trait_predicate)) |
| = predicate.kind().skip_binder() |
| && trait_predicate.trait_ref.self_ty() == *param_ty |
| { |
| true |
| } else { |
| false |
| } |
| }); |
| |
| let new_subst = cx.tcx.mk_substs_from_iter( |
| call_substs.iter() |
| .enumerate() |
| .map(|(i, t)| |
| if i == (*param_index as usize) { |
| GenericArg::from(ty) |
| } else { |
| t |
| })); |
| |
| if trait_predicates.any(|predicate| { |
| let predicate = EarlyBinder::new(predicate).subst(cx.tcx, new_subst); |
| let obligation = Obligation::new(cx.tcx, ObligationCause::dummy(), cx.param_env, predicate); |
| !cx.tcx.infer_ctxt().build().predicate_must_hold_modulo_regions(&obligation) |
| }) { |
| return false; |
| } |
| |
| let output_ty = fn_sig.output(); |
| if output_ty.contains(*param_ty) { |
| if let Ok(new_ty) = cx.tcx.try_subst_and_normalize_erasing_regions( |
| new_subst, cx.param_env, EarlyBinder::new(output_ty)) { |
| expr = parent_expr; |
| ty = new_ty; |
| continue; |
| } |
| return false; |
| } |
| |
| return true; |
| } |
| } else if let ExprKind::Block(..) = parent_expr.kind { |
| continue; |
| } |
| return false; |
| }, |
| _ => return false, |
| } |
| } |
| |
| false |
| } |
| |
| fn has_lifetime(ty: Ty<'_>) -> bool { |
| ty.walk().any(|t| matches!(t.unpack(), GenericArgKind::Lifetime(_))) |
| } |
| |
| /// Returns true if the named method is `Iterator::cloned` or `Iterator::copied`. |
| fn is_cloned_or_copied(cx: &LateContext<'_>, method_name: Symbol, method_def_id: DefId) -> bool { |
| (method_name.as_str() == "cloned" || method_name.as_str() == "copied") |
| && is_diag_trait_item(cx, method_def_id, sym::Iterator) |
| } |
| |
| /// Returns true if the named method can be used to convert the receiver to its "owned" |
| /// representation. |
| fn is_to_owned_like<'a>(cx: &LateContext<'a>, call_expr: &Expr<'a>, method_name: Symbol, method_def_id: DefId) -> bool { |
| is_clone_like(cx, method_name.as_str(), method_def_id) |
| || is_cow_into_owned(cx, method_name, method_def_id) |
| || is_to_string_on_string_like(cx, call_expr, method_name, method_def_id) |
| } |
| |
| /// Returns true if the named method is `Cow::into_owned`. |
| fn is_cow_into_owned(cx: &LateContext<'_>, method_name: Symbol, method_def_id: DefId) -> bool { |
| method_name.as_str() == "into_owned" && is_diag_item_method(cx, method_def_id, sym::Cow) |
| } |
| |
| /// Returns true if the named method is `ToString::to_string` and it's called on a type that |
| /// is string-like i.e. implements `AsRef<str>` or `Deref<Target = str>`. |
| fn is_to_string_on_string_like<'a>( |
| cx: &LateContext<'_>, |
| call_expr: &'a Expr<'a>, |
| method_name: Symbol, |
| method_def_id: DefId, |
| ) -> bool { |
| if method_name != sym::to_string || !is_diag_trait_item(cx, method_def_id, sym::ToString) { |
| return false; |
| } |
| |
| if let Some(substs) = cx.typeck_results().node_substs_opt(call_expr.hir_id) |
| && let [generic_arg] = substs.as_slice() |
| && let GenericArgKind::Type(ty) = generic_arg.unpack() |
| && let Some(deref_trait_id) = cx.tcx.get_diagnostic_item(sym::Deref) |
| && let Some(as_ref_trait_id) = cx.tcx.get_diagnostic_item(sym::AsRef) |
| && (cx.get_associated_type(ty, deref_trait_id, "Target") == Some(cx.tcx.types.str_) || |
| implements_trait(cx, ty, as_ref_trait_id, &[cx.tcx.types.str_.into()])) { |
| true |
| } else { |
| false |
| } |
| } |
