src/tools/clippy/clippy_lints/src/to_digit_is_some.rs

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