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;
5 use rustc_lint::{LateContext, LateLintPass};
7 use rustc_session::{declare_lint_pass, declare_tool_lint};
10 /// **What it does:** Checks for `.to_digit(..).is_some()` on `char`s.
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.
19 /// let is_digit = c.to_digit(radix).is_some();
21 /// can be written as:
25 /// let is_digit = c.is_digit(radix);
29 "`char.is_digit()` is clearer"
32 declare_lint_pass!(ToDigitIsSome => [TO_DIGIT_IS_SOME]);
34 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ToDigitIsSome {
35 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr<'_>) {
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;
41 let match_result = match &to_digit_expr.kind {
42 hir::ExprKind::MethodCall(to_digits_path, _, to_digit_args) => {
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;
49 Some((true, char_arg, radix_arg))
55 hir::ExprKind::Call(to_digits_call, to_digit_args) => {
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.tables.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"]);
63 Some((false, char_arg, radix_arg))
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);
81 "use of `.to_digit(..).is_some()`",
84 format!("{}.is_digit({})", char_arg_snip, radix_snip)
86 format!("char::is_digit({}, {})", char_arg_snip, radix_snip)