src/tools/clippy/clippy_lints/src/manual_is_ascii_check.rs

   1 use clippy_utils::msrvs::{self, Msrv};
   2 use clippy_utils::{diagnostics::span_lint_and_sugg, in_constant, macros::root_macro_call, source::snippet};
   3 use rustc_ast::LitKind::{Byte, Char};
   4 use rustc_errors::Applicability;
   5 use rustc_hir::{Expr, ExprKind, PatKind, RangeEnd};
   6 use rustc_lint::{LateContext, LateLintPass};
   7 use rustc_session::{declare_tool_lint, impl_lint_pass};
   8 use rustc_span::{def_id::DefId, sym};
   9
  10 declare_clippy_lint! {
  11     /// ### What it does
  12     /// Suggests to use dedicated built-in methods,
  13     /// `is_ascii_(lowercase|uppercase|digit)` for checking on corresponding ascii range
  14     ///
  15     /// ### Why is this bad?
  16     /// Using the built-in functions is more readable and makes it
  17     /// clear that it's not a specific subset of characters, but all
  18     /// ASCII (lowercase|uppercase|digit) characters.
  19     /// ### Example
  20     /// ```rust
  21     /// fn main() {
  22     ///     assert!(matches!('x', 'a'..='z'));
  23     ///     assert!(matches!(b'X', b'A'..=b'Z'));
  24     ///     assert!(matches!('2', '0'..='9'));
  25     ///     assert!(matches!('x', 'A'..='Z' | 'a'..='z'));
  26     /// }
  27     /// ```
  28     /// Use instead:
  29     /// ```rust
  30     /// fn main() {
  31     ///     assert!('x'.is_ascii_lowercase());
  32     ///     assert!(b'X'.is_ascii_uppercase());
  33     ///     assert!('2'.is_ascii_digit());
  34     ///     assert!('x'.is_ascii_alphabetic());
  35     /// }
  36     /// ```
  37     #[clippy::version = "1.66.0"]
  38     pub MANUAL_IS_ASCII_CHECK,
  39     style,
  40     "use dedicated method to check ascii range"
  41 }
  42 impl_lint_pass!(ManualIsAsciiCheck => [MANUAL_IS_ASCII_CHECK]);
  43
  44 pub struct ManualIsAsciiCheck {
  45     msrv: Msrv,
  46 }
  47
  48 impl ManualIsAsciiCheck {
  49     #[must_use]
  50     pub fn new(msrv: Msrv) -> Self {
  51         Self { msrv }
  52     }
  53 }
  54
  55 #[derive(Debug, PartialEq)]
  56 enum CharRange {
  57     /// 'a'..='z' | b'a'..=b'z'
  58     LowerChar,
  59     /// 'A'..='Z' | b'A'..=b'Z'
  60     UpperChar,
  61     /// AsciiLower | AsciiUpper
  62     FullChar,
  63     /// '0..=9'
  64     Digit,
  65     Otherwise,
  66 }
  67
  68 impl<'tcx> LateLintPass<'tcx> for ManualIsAsciiCheck {
  69     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
  70         if !self.msrv.meets(msrvs::IS_ASCII_DIGIT) {
  71             return;
  72         }
  73
  74         if in_constant(cx, expr.hir_id) && !self.msrv.meets(msrvs::IS_ASCII_DIGIT_CONST) {
  75             return;
  76         }
  77
  78         let Some(macro_call) = root_macro_call(expr.span) else { return };
  79
  80         if is_matches_macro(cx, macro_call.def_id) {
  81             if let ExprKind::Match(recv, [arm, ..], _) = expr.kind {
  82                 let range = check_pat(&arm.pat.kind);
  83
  84                 if let Some(sugg) = match range {
  85                     CharRange::UpperChar => Some("is_ascii_uppercase"),
  86                     CharRange::LowerChar => Some("is_ascii_lowercase"),
  87                     CharRange::FullChar => Some("is_ascii_alphabetic"),
  88                     CharRange::Digit => Some("is_ascii_digit"),
  89                     CharRange::Otherwise => None,
  90                 } {
  91                     let default_snip = "..";
  92                     // `snippet_with_applicability` may set applicability to `MaybeIncorrect` for
  93                     // macro span, so we check applicability manually by comparing `recv` is not default.
  94                     let recv = snippet(cx, recv.span, default_snip);
  95
  96                     let applicability = if recv == default_snip {
  97                         Applicability::HasPlaceholders
  98                     } else {
  99                         Applicability::MachineApplicable
 100                     };
 101
 102                     span_lint_and_sugg(
 103                         cx,
 104                         MANUAL_IS_ASCII_CHECK,
 105                         macro_call.span,
 106                         "manual check for common ascii range",
 107                         "try",
 108                         format!("{recv}.{sugg}()"),
 109                         applicability,
 110                     );
 111                 }
 112             }
 113         }
 114     }
 115
 116     extract_msrv_attr!(LateContext);
 117 }
 118
 119 fn check_pat(pat_kind: &PatKind<'_>) -> CharRange {
 120     match pat_kind {
 121         PatKind::Or(pats) => {
 122             let ranges = pats.iter().map(|p| check_pat(&p.kind)).collect::<Vec<_>>();
 123
 124             if ranges.len() == 2 && ranges.contains(&CharRange::UpperChar) && ranges.contains(&CharRange::LowerChar) {
 125                 CharRange::FullChar
 126             } else {
 127                 CharRange::Otherwise
 128             }
 129         },
 130         PatKind::Range(Some(start), Some(end), kind) if *kind == RangeEnd::Included => check_range(start, end),
 131         _ => CharRange::Otherwise,
 132     }
 133 }
 134
 135 fn check_range(start: &Expr<'_>, end: &Expr<'_>) -> CharRange {
 136     if let ExprKind::Lit(start_lit) = &start.kind
 137         && let ExprKind::Lit(end_lit) = &end.kind {
 138         match (&start_lit.node, &end_lit.node) {
 139             (Char('a'), Char('z')) | (Byte(b'a'), Byte(b'z')) => CharRange::LowerChar,
 140             (Char('A'), Char('Z')) | (Byte(b'A'), Byte(b'Z')) => CharRange::UpperChar,
 141             (Char('0'), Char('9')) | (Byte(b'0'), Byte(b'9')) => CharRange::Digit,
 142             _ => CharRange::Otherwise,
 143         }
 144     } else {
 145         CharRange::Otherwise
 146     }
 147 }
 148
 149 fn is_matches_macro(cx: &LateContext<'_>, macro_def_id: DefId) -> bool {
 150     if let Some(name) = cx.tcx.get_diagnostic_name(macro_def_id) {
 151         return sym::matches_macro == name;
 152     }
 153
 154     false
 155 }