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