src/tools/clippy/clippy_lints/src/methods/map_collect_result_unit.rs

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