1 use super::utils::clone_or_copy_needed;
2 use clippy_utils::diagnostics::span_lint;
3 use clippy_utils::ty::is_copy;
4 use clippy_utils::usage::mutated_variables;
5 use clippy_utils::{is_lang_ctor, is_trait_method, path_to_local_id};
7 use rustc_hir::intravisit::{walk_expr, Visitor};
8 use rustc_hir::LangItem::{OptionNone, OptionSome};
9 use rustc_lint::LateContext;
13 use super::UNNECESSARY_FILTER_MAP;
14 use super::UNNECESSARY_FIND_MAP;
16 pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, arg: &hir::Expr<'_>, name: &str) {
17 if !is_trait_method(cx, expr, sym::Iterator) {
21 if let hir::ExprKind::Closure(&hir::Closure { body, .. }) = arg.kind {
22 let body = cx.tcx.hir().body(body);
23 let arg_id = body.params[0].pat.hir_id;
24 let mutates_arg = mutated_variables(body.value, cx).map_or(true, |used_mutably| used_mutably.contains(&arg_id));
25 let (clone_or_copy_needed, _) = clone_or_copy_needed(cx, body.params[0].pat, body.value);
27 let (mut found_mapping, mut found_filtering) = check_expression(cx, arg_id, body.value);
29 let mut return_visitor = ReturnVisitor::new(cx, arg_id);
30 return_visitor.visit_expr(body.value);
31 found_mapping |= return_visitor.found_mapping;
32 found_filtering |= return_visitor.found_filtering;
34 let in_ty = cx.typeck_results().node_type(body.params[0].hir_id);
35 let sugg = if !found_filtering {
36 if name == "filter_map" { "map" } else { "map(..).next()" }
37 } else if !found_mapping && !mutates_arg && (!clone_or_copy_needed || is_copy(cx, in_ty)) {
38 match cx.typeck_results().expr_ty(body.value).kind() {
40 if cx.tcx.is_diagnostic_item(sym::Option, adt.did()) && in_ty == subst.type_at(0) =>
42 if name == "filter_map" { "filter" } else { "find" }
51 if name == "filter_map" {
52 UNNECESSARY_FILTER_MAP
57 &format!("this `.{}` can be written more simply using `.{}`", name, sugg),
62 // returns (found_mapping, found_filtering)
63 fn check_expression<'tcx>(cx: &LateContext<'tcx>, arg_id: hir::HirId, expr: &'tcx hir::Expr<'_>) -> (bool, bool) {
65 hir::ExprKind::Call(func, args) => {
66 if let hir::ExprKind::Path(ref path) = func.kind {
67 if is_lang_ctor(cx, path, OptionSome) {
68 if path_to_local_id(&args[0], arg_id) {
69 return (false, false);
76 hir::ExprKind::Block(block, _) => block
79 .map_or((false, false), |expr| check_expression(cx, arg_id, expr)),
80 hir::ExprKind::Match(_, arms, _) => {
81 let mut found_mapping = false;
82 let mut found_filtering = false;
84 let (m, f) = check_expression(cx, arg_id, arm.body);
88 (found_mapping, found_filtering)
90 // There must be an else_arm or there will be a type error
91 hir::ExprKind::If(_, if_arm, Some(else_arm)) => {
92 let if_check = check_expression(cx, arg_id, if_arm);
93 let else_check = check_expression(cx, arg_id, else_arm);
94 (if_check.0 | else_check.0, if_check.1 | else_check.1)
96 hir::ExprKind::Path(path) if is_lang_ctor(cx, path, OptionNone) => (false, true),
101 struct ReturnVisitor<'a, 'tcx> {
102 cx: &'a LateContext<'tcx>,
104 // Found a non-None return that isn't Some(input)
106 // Found a return that isn't Some
107 found_filtering: bool,
110 impl<'a, 'tcx> ReturnVisitor<'a, 'tcx> {
111 fn new(cx: &'a LateContext<'tcx>, arg_id: hir::HirId) -> ReturnVisitor<'a, 'tcx> {
115 found_mapping: false,
116 found_filtering: false,
121 impl<'a, 'tcx> Visitor<'tcx> for ReturnVisitor<'a, 'tcx> {
122 fn visit_expr(&mut self, expr: &'tcx hir::Expr<'_>) {
123 if let hir::ExprKind::Ret(Some(expr)) = &expr.kind {
124 let (found_mapping, found_filtering) = check_expression(self.cx, self.arg_id, expr);
125 self.found_mapping |= found_mapping;
126 self.found_filtering |= found_filtering;
128 walk_expr(self, expr);