clippy_lints/src/methods/map_collect_result_unit.rs

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::is_trait_method;
   3 use clippy_utils::source::snippet;
   4 use clippy_utils::ty::is_type_diagnostic_item;
   5 use if_chain::if_chain;
   6 use rustc_errors::Applicability;
   7 use rustc_hir as hir;
   8 use rustc_lint::LateContext;
   9 use rustc_middle::ty;
  10 use rustc_span::symbol::sym;
  11
  12 use super::MAP_COLLECT_RESULT_UNIT;
  13
  14 pub(super) fn check(
  15     cx: &LateContext<'_>,
  16     expr: &hir::Expr<'_>,
  17     map_args: &[hir::Expr<'_>],
  18     collect_args: &[hir::Expr<'_>],
  19 ) {
  20     if_chain! {
  21         // called on Iterator
  22         if let [map_expr] = collect_args;
  23         if is_trait_method(cx, map_expr, sym::Iterator);
  24         // return of collect `Result<(),_>`
  25         let collect_ret_ty = cx.typeck_results().expr_ty(expr);
  26         if is_type_diagnostic_item(cx, collect_ret_ty, sym::result_type);
  27         if let ty::Adt(_, substs) = collect_ret_ty.kind();
  28         if let Some(result_t) = substs.types().next();
  29         if result_t.is_unit();
  30         // get parts for snippet
  31         if let [iter, map_fn] = map_args;
  32         then {
  33             span_lint_and_sugg(
  34                 cx,
  35                 MAP_COLLECT_RESULT_UNIT,
  36                 expr.span,
  37                 "`.map().collect()` can be replaced with `.try_for_each()`",
  38                 "try this",
  39                 format!(
  40                     "{}.try_for_each({})",
  41                     snippet(cx, iter.span, ".."),
  42                     snippet(cx, map_fn.span, "..")
  43                 ),
  44                 Applicability::MachineApplicable,
  45             );
  46         }
  47     }
  48 }