clippy_lints/src/methods/unwrap_or_else_default.rs

   1 //! Lint for `some_result_or_option.unwrap_or_else(Default::default)`
   2
   3 use super::UNWRAP_OR_ELSE_DEFAULT;
   4 use clippy_utils::{
   5     diagnostics::span_lint_and_sugg, is_trait_item, source::snippet_with_applicability, ty::is_type_diagnostic_item,
   6 };
   7 use rustc_errors::Applicability;
   8 use rustc_hir as hir;
   9 use rustc_lint::LateContext;
  10 use rustc_span::sym;
  11
  12 pub(super) fn check<'tcx>(
  13     cx: &LateContext<'tcx>,
  14     expr: &'tcx hir::Expr<'_>,
  15     recv: &'tcx hir::Expr<'_>,
  16     u_arg: &'tcx hir::Expr<'_>,
  17 ) {
  18     // something.unwrap_or_else(Default::default)
  19     // ^^^^^^^^^- recv          ^^^^^^^^^^^^^^^^- u_arg
  20     // ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^- expr
  21     let recv_ty = cx.typeck_results().expr_ty(recv);
  22     let is_option = is_type_diagnostic_item(cx, recv_ty, sym::option_type);
  23     let is_result = is_type_diagnostic_item(cx, recv_ty, sym::result_type);
  24
  25     if_chain! {
  26         if is_option || is_result;
  27         if is_trait_item(cx, u_arg, sym::Default);
  28         then {
  29             let mut applicability = Applicability::MachineApplicable;
  30
  31             span_lint_and_sugg(
  32                 cx,
  33                 UNWRAP_OR_ELSE_DEFAULT,
  34                 expr.span,
  35                 "use of `.unwrap_or_else(..)` to construct default value",
  36                 "try",
  37                 format!(
  38                     "{}.unwrap_or_default()",
  39                     snippet_with_applicability(cx, recv.span, "..", &mut applicability)
  40                 ),
  41                 applicability,
  42             );
  43         }
  44     }
  45 }