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use clippy_utils::diagnostics::span_lint_and_help;
use clippy_utils::usage::mutated_variables;
use clippy_utils::{expr_or_init, is_trait_method};
use if_chain::if_chain;
use rustc_hir as hir;
use rustc_lint::LateContext;
use rustc_span::sym;
use super::SUSPICIOUS_MAP;
pub fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, count_recv: &hir::Expr<'_>, map_arg: &hir::Expr<'_>) {
if_chain! {
if is_trait_method(cx, count_recv, sym::Iterator);
if let hir::ExprKind::Closure(closure) = expr_or_init(cx, map_arg).kind;
let closure_body = cx.tcx.hir().body(closure.body);
if !cx.typeck_results().expr_ty(closure_body.value).is_unit();
then {
if let Some(map_mutated_vars) = mutated_variables(closure_body.value, cx) {
// A variable is used mutably inside of the closure. Suppress the lint.
if !map_mutated_vars.is_empty() {
return;
}
}
span_lint_and_help(
cx,
SUSPICIOUS_MAP,
expr.span,
"this call to `map()` won't have an effect on the call to `count()`",
None,
"make sure you did not confuse `map` with `filter`, `for_each` or `inspect`",
);
}
}
}
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