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;
7 use rustc_lint::{LateContext, LateLintPass};
9 use rustc_session::{declare_lint_pass, declare_tool_lint};
11 declare_clippy_lint! {
12 /// **What it does:** Checks for `.to_digit(..).is_some()` on `char`s.
14 /// **Why is this bad?** This is a convoluted way of checking if a `char` is a digit. It's
15 /// more straight forward to use the dedicated `is_digit` method.
21 /// let is_digit = c.to_digit(radix).is_some();
23 /// can be written as:
27 /// let is_digit = c.is_digit(radix);
31 "`char.is_digit()` is clearer"
34 declare_lint_pass!(ToDigitIsSome => [TO_DIGIT_IS_SOME]);
36 impl<'tcx> LateLintPass<'tcx> for ToDigitIsSome {
37 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
39 if let hir::ExprKind::MethodCall(is_some_path, _, is_some_args, _) = &expr.kind;
40 if is_some_path.ident.name.as_str() == "is_some";
41 if let [to_digit_expr] = &**is_some_args;
43 let match_result = match &to_digit_expr.kind {
44 hir::ExprKind::MethodCall(to_digits_path, _, to_digit_args, _) => {
46 if let [char_arg, radix_arg] = &**to_digit_args;
47 if to_digits_path.ident.name.as_str() == "to_digit";
48 let char_arg_ty = cx.typeck_results().expr_ty_adjusted(char_arg);
49 if *char_arg_ty.kind() == ty::Char;
51 Some((true, char_arg, radix_arg))
57 hir::ExprKind::Call(to_digits_call, to_digit_args) => {
59 if let [char_arg, radix_arg] = &**to_digit_args;
60 if let hir::ExprKind::Path(to_digits_path) = &to_digits_call.kind;
61 if let to_digits_call_res = cx.qpath_res(to_digits_path, to_digits_call.hir_id);
62 if let Some(to_digits_def_id) = to_digits_call_res.opt_def_id();
63 if match_def_path(cx, to_digits_def_id, &["core", "char", "methods", "<impl char>", "to_digit"]);
65 Some((false, char_arg, radix_arg))
74 if let Some((is_method_call, char_arg, radix_arg)) = match_result {
75 let mut applicability = Applicability::MachineApplicable;
76 let char_arg_snip = snippet_with_applicability(cx, char_arg.span, "_", &mut applicability);
77 let radix_snip = snippet_with_applicability(cx, radix_arg.span, "_", &mut applicability);
83 "use of `.to_digit(..).is_some()`",
86 format!("{}.is_digit({})", char_arg_snip, radix_snip)
88 format!("char::is_digit({}, {})", char_arg_snip, radix_snip)