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use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::match_def_path;
use clippy_utils::source::snippet_with_applicability;
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::ty;
use rustc_session::{declare_lint_pass, declare_tool_lint};
declare_clippy_lint! {
/// ### What it does
/// Checks for `.to_digit(..).is_some()` on `char`s.
///
/// ### Why is this bad?
/// This is a convoluted way of checking if a `char` is a digit. It's
/// more straight forward to use the dedicated `is_digit` method.
///
/// ### Example
/// ```rust
/// # let c = 'c';
/// # let radix = 10;
/// let is_digit = c.to_digit(radix).is_some();
/// ```
/// can be written as:
/// ```
/// # let c = 'c';
/// # let radix = 10;
/// let is_digit = c.is_digit(radix);
/// ```
#[clippy::version = "1.41.0"]
pub TO_DIGIT_IS_SOME,
style,
"`char.is_digit()` is clearer"
}
declare_lint_pass!(ToDigitIsSome => [TO_DIGIT_IS_SOME]);
impl<'tcx> LateLintPass<'tcx> for ToDigitIsSome {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
if_chain! {
if let hir::ExprKind::MethodCall(is_some_path, to_digit_expr, [], _) = &expr.kind;
if is_some_path.ident.name.as_str() == "is_some";
then {
let match_result = match &to_digit_expr.kind {
hir::ExprKind::MethodCall(to_digits_path, char_arg, [radix_arg], _) => {
if_chain! {
if to_digits_path.ident.name.as_str() == "to_digit";
let char_arg_ty = cx.typeck_results().expr_ty_adjusted(char_arg);
if *char_arg_ty.kind() == ty::Char;
then {
Some((true, *char_arg, radix_arg))
} else {
None
}
}
}
hir::ExprKind::Call(to_digits_call, to_digit_args) => {
if_chain! {
if let [char_arg, radix_arg] = *to_digit_args;
if let hir::ExprKind::Path(to_digits_path) = &to_digits_call.kind;
if let to_digits_call_res = cx.qpath_res(to_digits_path, to_digits_call.hir_id);
if let Some(to_digits_def_id) = to_digits_call_res.opt_def_id();
if match_def_path(cx, to_digits_def_id, &["core", "char", "methods", "<impl char>", "to_digit"]);
then {
Some((false, char_arg, radix_arg))
} else {
None
}
}
}
_ => None
};
if let Some((is_method_call, char_arg, radix_arg)) = match_result {
let mut applicability = Applicability::MachineApplicable;
let char_arg_snip = snippet_with_applicability(cx, char_arg.span, "_", &mut applicability);
let radix_snip = snippet_with_applicability(cx, radix_arg.span, "_", &mut applicability);
span_lint_and_sugg(
cx,
TO_DIGIT_IS_SOME,
expr.span,
"use of `.to_digit(..).is_some()`",
"try this",
if is_method_call {
format!("{}.is_digit({})", char_arg_snip, radix_snip)
} else {
format!("char::is_digit({}, {})", char_arg_snip, radix_snip)
},
applicability,
);
}
}
}
}
}
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