--- /dev/null
+use crate::utils::{is_type_diagnostic_item, match_trait_method, paths, snippet, span_lint_and_sugg};
+use if_chain::if_chain;
+use rustc_errors::Applicability;
+use rustc_hir as hir;
+use rustc_lint::LateContext;
+use rustc_middle::ty;
+use rustc_span::symbol::sym;
+
+use super::MAP_COLLECT_RESULT_UNIT;
+
+pub(super) fn check(
+ cx: &LateContext<'_>,
+ expr: &hir::Expr<'_>,
+ map_args: &[hir::Expr<'_>],
+ collect_args: &[hir::Expr<'_>],
+) {
+ if_chain! {
+ // called on Iterator
+ if let [map_expr] = collect_args;
+ if match_trait_method(cx, map_expr, &paths::ITERATOR);
+ // return of collect `Result<(),_>`
+ let collect_ret_ty = cx.typeck_results().expr_ty(expr);
+ if is_type_diagnostic_item(cx, collect_ret_ty, sym::result_type);
+ if let ty::Adt(_, substs) = collect_ret_ty.kind();
+ if let Some(result_t) = substs.types().next();
+ if result_t.is_unit();
+ // get parts for snippet
+ if let [iter, map_fn] = map_args;
+ then {
+ span_lint_and_sugg(
+ cx,
+ MAP_COLLECT_RESULT_UNIT,
+ expr.span,
+ "`.map().collect()` can be replaced with `.try_for_each()`",
+ "try this",
+ format!(
+ "{}.try_for_each({})",
+ snippet(cx, iter.span, ".."),
+ snippet(cx, map_fn.span, "..")
+ ),
+ Applicability::MachineApplicable,
+ );
+ }
+ }
+}