clippy_lints/src/to_digit_is_some.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 if_chain::if_chain;
   5 use rustc_errors::Applicability;
   6 use rustc_hir as hir;
   7 use rustc_lint::{LateContext, LateLintPass};
   8 use rustc_middle::ty;
   9 use rustc_session::{declare_lint_pass, declare_tool_lint};
  10
  11 declare_clippy_lint! {
  12     /// ### What it does
  13     /// Checks for `.to_digit(..).is_some()` on `char`s.
  14     ///
  15     /// ### Why is this bad?
  16     /// This is a convoluted way of checking if a `char` is a digit. It's
  17     /// more straight forward to use the dedicated `is_digit` method.
  18     ///
  19     /// ### Example
  20     /// ```rust
  21     /// # let c = 'c';
  22     /// # let radix = 10;
  23     /// let is_digit = c.to_digit(radix).is_some();
  24     /// ```
  25     /// can be written as:
  26     /// ```
  27     /// # let c = 'c';
  28     /// # let radix = 10;
  29     /// let is_digit = c.is_digit(radix);
  30     /// ```
  31     #[clippy::version = "1.41.0"]
  32     pub TO_DIGIT_IS_SOME,
  33     style,
  34     "`char.is_digit()` is clearer"
  35 }
  36
  37 declare_lint_pass!(ToDigitIsSome => [TO_DIGIT_IS_SOME]);
  38
  39 impl<'tcx> LateLintPass<'tcx> for ToDigitIsSome {
  40     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
  41         if_chain! {
  42             if let hir::ExprKind::MethodCall(is_some_path, to_digit_expr, [], _) = &expr.kind;
  43             if is_some_path.ident.name.as_str() == "is_some";
  44             then {
  45                 let match_result = match &to_digit_expr.kind {
  46                     hir::ExprKind::MethodCall(to_digits_path, char_arg, [radix_arg], _) => {
  47                         if_chain! {
  48                             if to_digits_path.ident.name.as_str() == "to_digit";
  49                             let char_arg_ty = cx.typeck_results().expr_ty_adjusted(char_arg);
  50                             if *char_arg_ty.kind() == ty::Char;
  51                             then {
  52                                 Some((true, *char_arg, radix_arg))
  53                             } else {
  54                                 None
  55                             }
  56                         }
  57                     }
  58                     hir::ExprKind::Call(to_digits_call, to_digit_args) => {
  59                         if_chain! {
  60                             if let [char_arg, radix_arg] = *to_digit_args;
  61                             if let hir::ExprKind::Path(to_digits_path) = &to_digits_call.kind;
  62                             if let to_digits_call_res = cx.qpath_res(to_digits_path, to_digits_call.hir_id);
  63                             if let Some(to_digits_def_id) = to_digits_call_res.opt_def_id();
  64                             if match_def_path(cx, to_digits_def_id, &["core", "char", "methods", "<impl char>", "to_digit"]);
  65                             then {
  66                                 Some((false, char_arg, radix_arg))
  67                             } else {
  68                                 None
  69                             }
  70                         }
  71                     }
  72                     _ => None
  73                 };
  74
  75                 if let Some((is_method_call, char_arg, radix_arg)) = match_result {
  76                     let mut applicability = Applicability::MachineApplicable;
  77                     let char_arg_snip = snippet_with_applicability(cx, char_arg.span, "_", &mut applicability);
  78                     let radix_snip = snippet_with_applicability(cx, radix_arg.span, "_", &mut applicability);
  79
  80                     span_lint_and_sugg(
  81                         cx,
  82                         TO_DIGIT_IS_SOME,
  83                         expr.span,
  84                         "use of `.to_digit(..).is_some()`",
  85                         "try this",
  86                         if is_method_call {
  87                             format!("{}.is_digit({})", char_arg_snip, radix_snip)
  88                         } else {
  89                             format!("char::is_digit({}, {})", char_arg_snip, radix_snip)
  90                         },
  91                         applicability,
  92                     );
  93                 }
  94             }
  95         }
  96     }
  97 }