clippy_lints/src/methods/needless_option_take.rs

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::match_def_path;
   3 use clippy_utils::source::snippet_with_applicability;
   4 use clippy_utils::ty::is_type_diagnostic_item;
   5 use rustc_errors::Applicability;
   6 use rustc_hir::Expr;
   7 use rustc_lint::LateContext;
   8 use rustc_span::sym;
   9
  10 use super::NEEDLESS_OPTION_TAKE;
  11
  12 pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, recv: &'tcx Expr<'_>) {
  13     // Checks if expression type is equal to sym::Option and if the expr is not a syntactic place
  14     if !recv.is_syntactic_place_expr() && is_expr_option(cx, recv) && has_expr_as_ref_path(cx, recv) {
  15         let mut applicability = Applicability::MachineApplicable;
  16         span_lint_and_sugg(
  17             cx,
  18             NEEDLESS_OPTION_TAKE,
  19             expr.span,
  20             "called `Option::take()` on a temporary value",
  21             "try",
  22             format!(
  23                 "{}",
  24                 snippet_with_applicability(cx, recv.span, "..", &mut applicability)
  25             ),
  26             applicability,
  27         );
  28     }
  29 }
  30
  31 fn is_expr_option(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
  32     let expr_type = cx.typeck_results().expr_ty(expr);
  33     is_type_diagnostic_item(cx, expr_type, sym::Option)
  34 }
  35
  36 fn has_expr_as_ref_path(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
  37     if let Some(ref_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id) {
  38         return match_def_path(cx, ref_id, &["core", "option", "Option", "as_ref"]);
  39     }
  40     false
  41 }