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 pub TO_DIGIT_IS_SOME, 32 style, 33 "`char.is_digit()` is clearer" 34 } 35 36 declare_lint_pass!(ToDigitIsSome => [TO_DIGIT_IS_SOME]); 37 38 impl<'tcx> LateLintPass<'tcx> for ToDigitIsSome { check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>)39 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) { 40 if_chain! { 41 if let hir::ExprKind::MethodCall(is_some_path, _, is_some_args, _) = &expr.kind; 42 if is_some_path.ident.name.as_str() == "is_some"; 43 if let [to_digit_expr] = &**is_some_args; 44 then { 45 let match_result = match &to_digit_expr.kind { 46 hir::ExprKind::MethodCall(to_digits_path, _, to_digit_args, _) => { 47 if_chain! { 48 if let [char_arg, radix_arg] = &**to_digit_args; 49 if to_digits_path.ident.name.as_str() == "to_digit"; 50 let char_arg_ty = cx.typeck_results().expr_ty_adjusted(char_arg); 51 if *char_arg_ty.kind() == ty::Char; 52 then { 53 Some((true, char_arg, radix_arg)) 54 } else { 55 None 56 } 57 } 58 } 59 hir::ExprKind::Call(to_digits_call, to_digit_args) => { 60 if_chain! { 61 if let [char_arg, radix_arg] = &**to_digit_args; 62 if let hir::ExprKind::Path(to_digits_path) = &to_digits_call.kind; 63 if let to_digits_call_res = cx.qpath_res(to_digits_path, to_digits_call.hir_id); 64 if let Some(to_digits_def_id) = to_digits_call_res.opt_def_id(); 65 if match_def_path(cx, to_digits_def_id, &["core", "char", "methods", "<impl char>", "to_digit"]); 66 then { 67 Some((false, char_arg, radix_arg)) 68 } else { 69 None 70 } 71 } 72 } 73 _ => None 74 }; 75 76 if let Some((is_method_call, char_arg, radix_arg)) = match_result { 77 let mut applicability = Applicability::MachineApplicable; 78 let char_arg_snip = snippet_with_applicability(cx, char_arg.span, "_", &mut applicability); 79 let radix_snip = snippet_with_applicability(cx, radix_arg.span, "_", &mut applicability); 80 81 span_lint_and_sugg( 82 cx, 83 TO_DIGIT_IS_SOME, 84 expr.span, 85 "use of `.to_digit(..).is_some()`", 86 "try this", 87 if is_method_call { 88 format!("{}.is_digit({})", char_arg_snip, radix_snip) 89 } else { 90 format!("char::is_digit({}, {})", char_arg_snip, radix_snip) 91 }, 92 applicability, 93 ); 94 } 95 } 96 } 97 } 98 } 99