| use rustc_errors::Applicability; |
| use rustc_hir::intravisit::{walk_expr, Visitor}; |
| use rustc_hir::{Block, BlockCheckMode, Closure, Expr, ExprKind, Stmt, StmtKind}; |
| use rustc_lint::{LateContext, LateLintPass}; |
| use rustc_session::declare_lint_pass; |
| use rustc_span::{sym, Span, Symbol}; |
| |
| use clippy_utils::diagnostics::span_lint_and_then; |
| use clippy_utils::is_trait_method; |
| use clippy_utils::source::snippet_with_applicability; |
| use clippy_utils::ty::has_iter_method; |
| |
| declare_clippy_lint! { |
| /// ### What it does |
| /// Checks for usage of `for_each` that would be more simply written as a |
| /// `for` loop. |
| /// |
| /// ### Why is this bad? |
| /// `for_each` may be used after applying iterator transformers like |
| /// `filter` for better readability and performance. It may also be used to fit a simple |
| /// operation on one line. |
| /// But when none of these apply, a simple `for` loop is more idiomatic. |
| /// |
| /// ### Example |
| /// ```no_run |
| /// let v = vec![0, 1, 2]; |
| /// v.iter().for_each(|elem| { |
| /// println!("{}", elem); |
| /// }) |
| /// ``` |
| /// Use instead: |
| /// ```no_run |
| /// let v = vec![0, 1, 2]; |
| /// for elem in v.iter() { |
| /// println!("{}", elem); |
| /// } |
| /// ``` |
| /// |
| /// ### Known Problems |
| /// When doing things such as: |
| /// ```ignore |
| /// let v = vec![0, 1, 2]; |
| /// v.iter().for_each(|elem| unsafe { |
| /// libc::printf(c"%d\n".as_ptr(), elem); |
| /// }); |
| /// ``` |
| /// This lint will not trigger. |
| #[clippy::version = "1.53.0"] |
| pub NEEDLESS_FOR_EACH, |
| pedantic, |
| "using `for_each` where a `for` loop would be simpler" |
| } |
| |
| declare_lint_pass!(NeedlessForEach => [NEEDLESS_FOR_EACH]); |
| |
| impl<'tcx> LateLintPass<'tcx> for NeedlessForEach { |
| fn check_stmt(&mut self, cx: &LateContext<'tcx>, stmt: &'tcx Stmt<'_>) { |
| let (StmtKind::Expr(expr) | StmtKind::Semi(expr)) = stmt.kind else { |
| return; |
| }; |
| |
| if let ExprKind::MethodCall(method_name, for_each_recv, [for_each_arg], _) = expr.kind |
| // Check the method name is `for_each`. |
| && method_name.ident.name == Symbol::intern("for_each") |
| // Check `for_each` is an associated function of `Iterator`. |
| && is_trait_method(cx, expr, sym::Iterator) |
| // Checks the receiver of `for_each` is also a method call. |
| && let ExprKind::MethodCall(_, iter_recv, [], _) = for_each_recv.kind |
| // Skip the lint if the call chain is too long. e.g. `v.field.iter().for_each()` or |
| // `v.foo().iter().for_each()` must be skipped. |
| && matches!( |
| iter_recv.kind, |
| ExprKind::Array(..) | ExprKind::Call(..) | ExprKind::Path(..) |
| ) |
| // Checks the type of the `iter` method receiver is NOT a user defined type. |
| && has_iter_method(cx, cx.typeck_results().expr_ty(iter_recv)).is_some() |
| // Skip the lint if the body is not block because this is simpler than `for` loop. |
| // e.g. `v.iter().for_each(f)` is simpler and clearer than using `for` loop. |
| && let ExprKind::Closure(&Closure { body, .. }) = for_each_arg.kind |
| && let body = cx.tcx.hir().body(body) |
| // Skip the lint if the body is not safe, so as not to suggest `for … in … unsafe {}` |
| // and suggesting `for … in … { unsafe { } }` is a little ugly. |
| && let ExprKind::Block(Block { rules: BlockCheckMode::DefaultBlock, .. }, ..) = body.value.kind |
| { |
| let mut ret_collector = RetCollector::default(); |
| ret_collector.visit_expr(body.value); |
| |
| // Skip the lint if `return` is used in `Loop` in order not to suggest using `'label`. |
| if ret_collector.ret_in_loop { |
| return; |
| } |
| |
| let (mut applicability, ret_suggs) = if ret_collector.spans.is_empty() { |
| (Applicability::MachineApplicable, None) |
| } else { |
| ( |
| Applicability::MaybeIncorrect, |
| Some( |
| ret_collector |
| .spans |
| .into_iter() |
| .map(|span| (span, "continue".to_string())) |
| .collect(), |
| ), |
| ) |
| }; |
| |
| let sugg = format!( |
| "for {} in {} {}", |
| snippet_with_applicability(cx, body.params[0].pat.span, "..", &mut applicability), |
| snippet_with_applicability(cx, for_each_recv.span, "..", &mut applicability), |
| snippet_with_applicability(cx, body.value.span, "..", &mut applicability), |
| ); |
| |
| span_lint_and_then(cx, NEEDLESS_FOR_EACH, stmt.span, "needless use of `for_each`", |diag| { |
| diag.span_suggestion(stmt.span, "try", sugg, applicability); |
| if let Some(ret_suggs) = ret_suggs { |
| diag.multipart_suggestion("...and replace `return` with `continue`", ret_suggs, applicability); |
| } |
| }); |
| } |
| } |
| } |
| |
| /// This type plays two roles. |
| /// 1. Collect spans of `return` in the closure body. |
| /// 2. Detect use of `return` in `Loop` in the closure body. |
| /// |
| /// NOTE: The functionality of this type is similar to |
| /// [`clippy_utils::visitors::find_all_ret_expressions`], but we can't use |
| /// `find_all_ret_expressions` instead of this type. The reasons are: |
| /// 1. `find_all_ret_expressions` passes the argument of `ExprKind::Ret` to a callback, but what we |
| /// need here is `ExprKind::Ret` itself. |
| /// 2. We can't trace current loop depth with `find_all_ret_expressions`. |
| #[derive(Default)] |
| struct RetCollector { |
| spans: Vec<Span>, |
| ret_in_loop: bool, |
| loop_depth: u16, |
| } |
| |
| impl<'tcx> Visitor<'tcx> for RetCollector { |
| fn visit_expr(&mut self, expr: &Expr<'_>) { |
| match expr.kind { |
| ExprKind::Ret(..) => { |
| if self.loop_depth > 0 && !self.ret_in_loop { |
| self.ret_in_loop = true; |
| } |
| |
| self.spans.push(expr.span); |
| }, |
| |
| ExprKind::Loop(..) => { |
| self.loop_depth += 1; |
| walk_expr(self, expr); |
| self.loop_depth -= 1; |
| return; |
| }, |
| |
| _ => {}, |
| } |
| |
| walk_expr(self, expr); |
| } |
| } |