| use clippy_utils::diagnostics::{span_lint_and_help, span_lint_and_sugg, span_lint_and_then}; |
| use clippy_utils::source::{snippet, snippet_with_applicability, snippet_with_context}; |
| use clippy_utils::sugg::Sugg; |
| use clippy_utils::ty::{is_copy, is_type_diagnostic_item, same_type_and_consts}; |
| use clippy_utils::{get_parent_expr, is_trait_method, is_ty_alias, match_def_path, path_to_local, paths}; |
| use if_chain::if_chain; |
| use rustc_errors::Applicability; |
| use rustc_hir::def::DefKind; |
| use rustc_hir::def_id::DefId; |
| use rustc_hir::{BindingAnnotation, Expr, ExprKind, HirId, MatchSource, Node, PatKind}; |
| use rustc_infer::infer::TyCtxtInferExt; |
| use rustc_infer::traits::Obligation; |
| use rustc_lint::{LateContext, LateLintPass}; |
| use rustc_middle::traits::ObligationCause; |
| use rustc_middle::ty::{self, EarlyBinder, GenericArg, GenericArgsRef, Ty, TypeVisitableExt}; |
| use rustc_session::{declare_tool_lint, impl_lint_pass}; |
| use rustc_span::{sym, Span}; |
| use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt; |
| |
| declare_clippy_lint! { |
| /// ### What it does |
| /// Checks for `Into`, `TryInto`, `From`, `TryFrom`, or `IntoIter` calls |
| /// which uselessly convert to the same type. |
| /// |
| /// ### Why is this bad? |
| /// Redundant code. |
| /// |
| /// ### Example |
| /// ```rust |
| /// // format!() returns a `String` |
| /// let s: String = format!("hello").into(); |
| /// ``` |
| /// |
| /// Use instead: |
| /// ```rust |
| /// let s: String = format!("hello"); |
| /// ``` |
| #[clippy::version = "1.45.0"] |
| pub USELESS_CONVERSION, |
| complexity, |
| "calls to `Into`, `TryInto`, `From`, `TryFrom`, or `IntoIter` which perform useless conversions to the same type" |
| } |
| |
| #[derive(Default)] |
| pub struct UselessConversion { |
| try_desugar_arm: Vec<HirId>, |
| expn_depth: u32, |
| } |
| |
| impl_lint_pass!(UselessConversion => [USELESS_CONVERSION]); |
| |
| enum MethodOrFunction { |
| Method, |
| Function, |
| } |
| |
| impl MethodOrFunction { |
| /// Maps the argument position in `pos` to the parameter position. |
| /// For methods, `self` is skipped. |
| fn param_pos(self, pos: usize) -> usize { |
| match self { |
| MethodOrFunction::Method => pos + 1, |
| MethodOrFunction::Function => pos, |
| } |
| } |
| } |
| |
| /// Returns the span of the `IntoIterator` trait bound in the function pointed to by `fn_did`, |
| /// iff all of the bounds also hold for the type of the `.into_iter()` receiver. |
| /// ```ignore |
| /// pub fn foo<I>(i: I) |
| /// where I: IntoIterator<Item=i32> + ExactSizeIterator |
| /// ^^^^^^^^^^^^^^^^^ this extra bound stops us from suggesting to remove `.into_iter()` ... |
| /// { |
| /// assert_eq!(i.len(), 3); |
| /// } |
| /// |
| /// pub fn bar() { |
| /// foo([1, 2, 3].into_iter()); |
| /// ^^^^^^^^^^^^ ... here, because `[i32; 3]` is not `ExactSizeIterator` |
| /// } |
| /// ``` |
| fn into_iter_bound<'tcx>( |
| cx: &LateContext<'tcx>, |
| fn_did: DefId, |
| into_iter_did: DefId, |
| into_iter_receiver: Ty<'tcx>, |
| param_index: u32, |
| node_args: GenericArgsRef<'tcx>, |
| ) -> Option<Span> { |
| let param_env = cx.tcx.param_env(fn_did); |
| let mut into_iter_span = None; |
| |
| for (pred, span) in cx.tcx.explicit_predicates_of(fn_did).predicates { |
| if let ty::ClauseKind::Trait(tr) = pred.kind().skip_binder() { |
| if tr.self_ty().is_param(param_index) { |
| if tr.def_id() == into_iter_did { |
| into_iter_span = Some(*span); |
| } else { |
| let tr = cx.tcx.erase_regions(tr); |
| if tr.has_escaping_bound_vars() { |
| return None; |
| } |
| |
| // Substitute generics in the predicate and replace the IntoIterator type parameter with the |
| // `.into_iter()` receiver to see if the bound also holds for that type. |
| let args = cx.tcx.mk_args_from_iter(node_args.iter().enumerate().map(|(i, arg)| { |
| if i == param_index as usize { |
| GenericArg::from(into_iter_receiver) |
| } else { |
| arg |
| } |
| })); |
| |
| let predicate = EarlyBinder::bind(tr).instantiate(cx.tcx, args); |
| let obligation = Obligation::new(cx.tcx, ObligationCause::dummy(), param_env, predicate); |
| if !cx |
| .tcx |
| .infer_ctxt() |
| .build() |
| .predicate_must_hold_modulo_regions(&obligation) |
| { |
| return None; |
| } |
| } |
| } |
| } |
| } |
| |
| into_iter_span |
| } |
| |
| /// Extracts the receiver of a `.into_iter()` method call. |
| fn into_iter_call<'hir>(cx: &LateContext<'_>, expr: &'hir Expr<'hir>) -> Option<&'hir Expr<'hir>> { |
| if let ExprKind::MethodCall(name, recv, _, _) = expr.kind |
| && is_trait_method(cx, expr, sym::IntoIterator) |
| && name.ident.name == sym::into_iter |
| { |
| Some(recv) |
| } else { |
| None |
| } |
| } |
| |
| /// Same as [`into_iter_call`], but tries to look for the innermost `.into_iter()` call, e.g.: |
| /// `foo.into_iter().into_iter()` |
| /// ^^^ we want this expression |
| fn into_iter_deep_call<'hir>(cx: &LateContext<'_>, mut expr: &'hir Expr<'hir>) -> (&'hir Expr<'hir>, usize) { |
| let mut depth = 0; |
| while let Some(recv) = into_iter_call(cx, expr) { |
| expr = recv; |
| depth += 1; |
| } |
| (expr, depth) |
| } |
| |
| #[expect(clippy::too_many_lines)] |
| impl<'tcx> LateLintPass<'tcx> for UselessConversion { |
| fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) { |
| if e.span.from_expansion() { |
| self.expn_depth += 1; |
| return; |
| } |
| |
| if Some(&e.hir_id) == self.try_desugar_arm.last() { |
| return; |
| } |
| |
| match e.kind { |
| ExprKind::Match(_, arms, MatchSource::TryDesugar(_)) => { |
| let (ExprKind::Ret(Some(e)) | ExprKind::Break(_, Some(e))) = arms[0].body.kind else { |
| return; |
| }; |
| if let ExprKind::Call(_, [arg, ..]) = e.kind { |
| self.try_desugar_arm.push(arg.hir_id); |
| } |
| }, |
| |
| ExprKind::MethodCall(name, recv, ..) => { |
| if is_trait_method(cx, e, sym::Into) && name.ident.as_str() == "into" { |
| let a = cx.typeck_results().expr_ty(e); |
| let b = cx.typeck_results().expr_ty(recv); |
| if same_type_and_consts(a, b) { |
| let mut app = Applicability::MachineApplicable; |
| let sugg = snippet_with_context(cx, recv.span, e.span.ctxt(), "<expr>", &mut app).0; |
| span_lint_and_sugg( |
| cx, |
| USELESS_CONVERSION, |
| e.span, |
| &format!("useless conversion to the same type: `{b}`"), |
| "consider removing `.into()`", |
| sugg.into_owned(), |
| app, |
| ); |
| } |
| } |
| if let Some(into_iter_recv) = into_iter_call(cx, e) |
| // Make sure that there is no parent expression, or if there is, make sure it's not a `.into_iter()` call. |
| // The reason for that is that we only want to lint once (the outermost call) |
| // in cases like `foo.into_iter().into_iter()` |
| && get_parent_expr(cx, e) |
| .and_then(|parent| into_iter_call(cx, parent)) |
| .is_none() |
| { |
| if let Some(parent) = get_parent_expr(cx, e) { |
| let parent_fn = match parent.kind { |
| ExprKind::Call(recv, args) |
| if let ExprKind::Path(ref qpath) = recv.kind |
| && let Some(did) = cx.qpath_res(qpath, recv.hir_id).opt_def_id() |
| // make sure that the path indeed points to a fn-like item, so that |
| // `fn_sig` does not ICE. (see #11065) |
| && cx.tcx.opt_def_kind(did).is_some_and(DefKind::is_fn_like) => |
| { |
| Some(( |
| did, |
| args, |
| cx.typeck_results().node_args(recv.hir_id), |
| MethodOrFunction::Function |
| )) |
| } |
| ExprKind::MethodCall(.., args, _) => { |
| cx.typeck_results().type_dependent_def_id(parent.hir_id) |
| .map(|did| { |
| return ( |
| did, |
| args, |
| cx.typeck_results().node_args(parent.hir_id), |
| MethodOrFunction::Method |
| ); |
| }) |
| } |
| _ => None, |
| }; |
| |
| if let Some((parent_fn_did, args, node_args, kind)) = parent_fn |
| && let Some(into_iter_did) = cx.tcx.get_diagnostic_item(sym::IntoIterator) |
| && let sig = cx.tcx.fn_sig(parent_fn_did).skip_binder().skip_binder() |
| && let Some(arg_pos) = args.iter().position(|x| x.hir_id == e.hir_id) |
| && let Some(&into_iter_param) = sig.inputs().get(kind.param_pos(arg_pos)) |
| && let ty::Param(param) = into_iter_param.kind() |
| && let Some(span) = into_iter_bound( |
| cx, |
| parent_fn_did, |
| into_iter_did, |
| cx.typeck_results().expr_ty(into_iter_recv), |
| param.index, |
| node_args |
| ) |
| && self.expn_depth == 0 |
| { |
| // Get the "innermost" `.into_iter()` call, e.g. given this expression: |
| // `foo.into_iter().into_iter()` |
| // ^^^ |
| let (into_iter_recv, depth) = into_iter_deep_call(cx, into_iter_recv); |
| |
| let plural = if depth == 0 { "" } else { "s" }; |
| let mut applicability = Applicability::MachineApplicable; |
| let sugg = snippet_with_applicability(cx, into_iter_recv.span.source_callsite(), "<expr>", &mut applicability).into_owned(); |
| span_lint_and_then(cx, USELESS_CONVERSION, e.span, "explicit call to `.into_iter()` in function argument accepting `IntoIterator`", |diag| { |
| diag.span_suggestion( |
| e.span, |
| format!("consider removing the `.into_iter()`{plural}"), |
| sugg, |
| applicability, |
| ); |
| diag.span_note(span, "this parameter accepts any `IntoIterator`, so you don't need to call `.into_iter()`"); |
| }); |
| |
| // Early return to avoid linting again with contradicting suggestions |
| return; |
| } |
| } |
| |
| if let Some(id) = path_to_local(recv) && |
| let Node::Pat(pat) = cx.tcx.hir().get(id) && |
| let PatKind::Binding(ann, ..) = pat.kind && |
| ann != BindingAnnotation::MUT |
| { |
| // Do not remove .into_iter() applied to a non-mutable local variable used in |
| // a larger expression context as it would differ in mutability. |
| return; |
| } |
| |
| let a = cx.typeck_results().expr_ty(e); |
| let b = cx.typeck_results().expr_ty(recv); |
| |
| // If the types are identical then .into_iter() can be removed, unless the type |
| // implements Copy, in which case .into_iter() returns a copy of the receiver and |
| // cannot be safely omitted. |
| if same_type_and_consts(a, b) && !is_copy(cx, b) { |
| let sugg = snippet(cx, recv.span, "<expr>").into_owned(); |
| span_lint_and_sugg( |
| cx, |
| USELESS_CONVERSION, |
| e.span, |
| &format!("useless conversion to the same type: `{b}`"), |
| "consider removing `.into_iter()`", |
| sugg, |
| Applicability::MachineApplicable, // snippet |
| ); |
| } |
| } |
| if_chain! { |
| if is_trait_method(cx, e, sym::TryInto) && name.ident.name == sym::try_into; |
| let a = cx.typeck_results().expr_ty(e); |
| let b = cx.typeck_results().expr_ty(recv); |
| if is_type_diagnostic_item(cx, a, sym::Result); |
| if let ty::Adt(_, args) = a.kind(); |
| if let Some(a_type) = args.types().next(); |
| if same_type_and_consts(a_type, b); |
| |
| then { |
| span_lint_and_help( |
| cx, |
| USELESS_CONVERSION, |
| e.span, |
| &format!("useless conversion to the same type: `{b}`"), |
| None, |
| "consider removing `.try_into()`", |
| ); |
| } |
| } |
| }, |
| |
| ExprKind::Call(path, [arg]) => { |
| if_chain! { |
| if let ExprKind::Path(ref qpath) = path.kind; |
| if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id(); |
| if !is_ty_alias(qpath); |
| then { |
| let a = cx.typeck_results().expr_ty(e); |
| let b = cx.typeck_results().expr_ty(arg); |
| if_chain! { |
| if match_def_path(cx, def_id, &paths::TRY_FROM); |
| if is_type_diagnostic_item(cx, a, sym::Result); |
| if let ty::Adt(_, args) = a.kind(); |
| if let Some(a_type) = args.types().next(); |
| if same_type_and_consts(a_type, b); |
| |
| then { |
| let hint = format!("consider removing `{}()`", snippet(cx, path.span, "TryFrom::try_from")); |
| span_lint_and_help( |
| cx, |
| USELESS_CONVERSION, |
| e.span, |
| &format!("useless conversion to the same type: `{b}`"), |
| None, |
| &hint, |
| ); |
| } |
| } |
| |
| if_chain! { |
| if cx.tcx.is_diagnostic_item(sym::from_fn, def_id); |
| if same_type_and_consts(a, b); |
| |
| then { |
| let mut app = Applicability::MachineApplicable; |
| let sugg = Sugg::hir_with_context(cx, arg, e.span.ctxt(), "<expr>", &mut app).maybe_par(); |
| let sugg_msg = |
| format!("consider removing `{}()`", snippet(cx, path.span, "From::from")); |
| span_lint_and_sugg( |
| cx, |
| USELESS_CONVERSION, |
| e.span, |
| &format!("useless conversion to the same type: `{b}`"), |
| &sugg_msg, |
| sugg.to_string(), |
| app, |
| ); |
| } |
| } |
| } |
| } |
| }, |
| |
| _ => {}, |
| } |
| } |
| |
| fn check_expr_post(&mut self, _: &LateContext<'tcx>, e: &'tcx Expr<'_>) { |
| if Some(&e.hir_id) == self.try_desugar_arm.last() { |
| self.try_desugar_arm.pop(); |
| } |
| if e.span.from_expansion() { |
| self.expn_depth -= 1; |
| } |
| } |
| } |
