1 use clippy_utils::diagnostics::span_lint_and_help;
2 use clippy_utils::usage::mutated_variables;
3 use clippy_utils::{expr_or_init, is_trait_method};
4 use if_chain::if_chain;
6 use rustc_lint::LateContext;
9 use super::SUSPICIOUS_MAP;
11 pub fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, count_recv: &hir::Expr<'_>, map_arg: &hir::Expr<'_>) {
13 if is_trait_method(cx, count_recv, sym::Iterator);
14 let closure = expr_or_init(cx, map_arg);
15 if let Some(def_id) = cx.tcx.hir().opt_local_def_id(closure.hir_id);
16 if let Some(body_id) = cx.tcx.hir().maybe_body_owned_by(def_id);
17 let closure_body = cx.tcx.hir().body(body_id);
18 if !cx.typeck_results().expr_ty(closure_body.value).is_unit();
20 if let Some(map_mutated_vars) = mutated_variables(closure_body.value, cx) {
21 // A variable is used mutably inside of the closure. Suppress the lint.
22 if !map_mutated_vars.is_empty() {
30 "this call to `map()` won't have an effect on the call to `count()`",
32 "make sure you did not confuse `map` with `filter`, `for_each` or `inspect`",