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<'tcx>(cx: &LateContext<'tcx>, 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(body_id) = cx.tcx.hir().maybe_body_owned_by(closure.hir_id);
16 let closure_body = cx.tcx.hir().body(body_id);
17 if !cx.typeck_results().expr_ty(&closure_body.value).is_unit();
19 if let Some(map_mutated_vars) = mutated_variables(&closure_body.value, cx) {
20 // A variable is used mutably inside of the closure. Suppress the lint.
21 if !map_mutated_vars.is_empty() {
29 "this call to `map()` won't have an effect on the call to `count()`",
31 "make sure you did not confuse `map` with `filter` or `for_each`",