feat: implement manual_is_ascii_check lint

modify

fix: allow unused in test code

fix: types in doc comment

Update clippy_lints/src/manual_is_ascii_check.rs

Co-authored-by: Fridtjof Stoldt <xFrednet@gmail.com>

Update clippy_lints/src/manual_is_ascii_check.rs

Co-authored-by: Fridtjof Stoldt <xFrednet@gmail.com>

Update clippy_lints/src/manual_is_ascii_check.rs

Co-authored-by: Fridtjof Stoldt <xFrednet@gmail.com>

fix ui test result

fix: unnecessary format!

chore: apply feedbacks

* check msrvs also for const fn
* check applicability manually
* modify documents

3 files changed, 160 insertions, 0 deletions

diff --git a/clippy_lints/src/declared_lints.rs b/clippy_lints/src/declared_lints.rs
index f4fc2bd3330..448b12f1b0a 100644
--- a/clippy_lints/src/declared_lints.rs
+++ b/clippy_lints/src/declared_lints.rs
@@ -251,6 +251,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
     crate::manual_bits::MANUAL_BITS_INFO,
     crate::manual_clamp::MANUAL_CLAMP_INFO,
     crate::manual_instant_elapsed::MANUAL_INSTANT_ELAPSED_INFO,
+    crate::manual_is_ascii_check::MANUAL_IS_ASCII_CHECK_INFO,
     crate::manual_let_else::MANUAL_LET_ELSE_INFO,
     crate::manual_non_exhaustive::MANUAL_NON_EXHAUSTIVE_INFO,
     crate::manual_rem_euclid::MANUAL_REM_EUCLID_INFO,
diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index 197d8f2dc08..fe05f2a13f9 100644
--- a/clippy_lints/src/lib.rs
+++ b/clippy_lints/src/lib.rs
@@ -173,6 +173,7 @@ mod manual_async_fn;
 mod manual_bits;
 mod manual_clamp;
 mod manual_instant_elapsed;
+mod manual_is_ascii_check;
 mod manual_let_else;
 mod manual_non_exhaustive;
 mod manual_rem_euclid;
@@ -918,6 +919,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_late_pass(|_| Box::new(missing_trait_methods::MissingTraitMethods));
     store.register_late_pass(|_| Box::new(from_raw_with_void_ptr::FromRawWithVoidPtr));
     store.register_late_pass(|_| Box::new(suspicious_xor_used_as_pow::ConfusingXorAndPow));
+    store.register_late_pass(move |_| Box::new(manual_is_ascii_check::ManualIsAsciiCheck::new(msrv)));
     // add lints here, do not remove this comment, it's used in `new_lint`
 }
 
diff --git a/clippy_lints/src/manual_is_ascii_check.rs b/clippy_lints/src/manual_is_ascii_check.rs
new file mode 100644
index 00000000000..3a6b693f766
--- /dev/null
+++ b/clippy_lints/src/manual_is_ascii_check.rs
@@ -0,0 +1,157 @@
+use rustc_ast::LitKind::{Byte, Char};
+use rustc_errors::Applicability;
+use rustc_hir::{Expr, ExprKind, PatKind, RangeEnd};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_semver::RustcVersion;
+use rustc_session::{declare_tool_lint, impl_lint_pass};
+use rustc_span::{def_id::DefId, sym};
+
+use clippy_utils::{
+    diagnostics::span_lint_and_sugg, in_constant, macros::root_macro_call, meets_msrv, msrvs, source::snippet,
+};
+
+declare_clippy_lint! {
+    /// ### What it does
+    /// Suggests to use dedicated built-in methods,
+    /// `is_ascii_(lowercase|uppercase|digit)` for checking on corresponding ascii range
+    ///
+    /// ### Why is this bad?
+    /// Using the built-in functions is more readable and makes it
+    /// clear that it's not a specific subset of characters, but all
+    /// ASCII (lowercase|uppercase|digit) characters.
+    /// ### Example
+    /// ```rust
+    /// fn main() {
+    ///     assert!(matches!('x', 'a'..='z'));
+    ///     assert!(matches!(b'X', b'A'..=b'Z'));
+    ///     assert!(matches!('2', '0'..='9'));
+    ///     assert!(matches!('x', 'A'..='Z' | 'a'..='z'));
+    /// }
+    /// ```
+    /// Use instead:
+    /// ```rust
+    /// fn main() {
+    ///     assert!('x'.is_ascii_lowercase());
+    ///     assert!(b'X'.is_ascii_uppercase());
+    ///     assert!('2'.is_ascii_digit());
+    ///     assert!('x'.is_ascii_alphabetic());
+    /// }
+    /// ```
+    #[clippy::version = "1.66.0"]
+    pub MANUAL_IS_ASCII_CHECK,
+    style,
+    "use dedicated method to check ascii range"
+}
+impl_lint_pass!(ManualIsAsciiCheck => [MANUAL_IS_ASCII_CHECK]);
+
+pub struct ManualIsAsciiCheck {
+    msrv: Option<RustcVersion>,
+}
+
+impl ManualIsAsciiCheck {
+    #[must_use]
+    pub fn new(msrv: Option<RustcVersion>) -> Self {
+        Self { msrv }
+    }
+}
+
+#[derive(Debug, PartialEq)]
+enum CharRange {
+    /// 'a'..='z' | b'a'..=b'z'
+    LowerChar,
+    /// 'A'..='Z' | b'A'..=b'Z'
+    UpperChar,
+    /// AsciiLower | AsciiUpper
+    FullChar,
+    /// '0..=9'
+    Digit,
+    Otherwise,
+}
+
+impl<'tcx> LateLintPass<'tcx> for ManualIsAsciiCheck {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+        if !meets_msrv(self.msrv, msrvs::IS_ASCII_DIGIT) {
+            return;
+        }
+
+        if in_constant(cx, expr.hir_id) && !meets_msrv(self.msrv, msrvs::IS_ASCII_DIGIT_CONST) {
+            return;
+        }
+
+        let Some(macro_call) = root_macro_call(expr.span) else { return };
+
+        if is_matches_macro(cx, macro_call.def_id) {
+            if let ExprKind::Match(recv, [arm, ..], _) = expr.kind {
+                let range = check_pat(&arm.pat.kind);
+
+                if let Some(sugg) = match range {
+                    CharRange::UpperChar => Some("is_ascii_uppercase"),
+                    CharRange::LowerChar => Some("is_ascii_lowercase"),
+                    CharRange::FullChar => Some("is_ascii_alphabetic"),
+                    CharRange::Digit => Some("is_ascii_digit"),
+                    CharRange::Otherwise => None,
+                } {
+                    let mut applicability = Applicability::MaybeIncorrect;
+                    let default_snip = "..";
+                    // `snippet_with_applicability` may set applicability to `MaybeIncorrect` for
+                    // macro span, so we check applicability manually by comaring `recv` is not default.
+                    let recv = snippet(cx, recv.span, default_snip);
+
+                    if recv != default_snip {
+                        applicability = Applicability::MachineApplicable;
+                    }
+
+                    span_lint_and_sugg(
+                        cx,
+                        MANUAL_IS_ASCII_CHECK,
+                        macro_call.span,
+                        "manual check for common ascii range",
+                        "try",
+                        format!("{recv}.{sugg}()"),
+                        applicability,
+                    );
+                }
+            }
+        }
+    }
+
+    extract_msrv_attr!(LateContext);
+}
+
+fn check_pat(pat_kind: &PatKind<'_>) -> CharRange {
+    match pat_kind {
+        PatKind::Or(pats) => {
+            let ranges = pats.iter().map(|p| check_pat(&p.kind)).collect::<Vec<_>>();
+
+            if ranges.len() == 2 && ranges.contains(&CharRange::UpperChar) && ranges.contains(&CharRange::LowerChar) {
+                CharRange::FullChar
+            } else {
+                CharRange::Otherwise
+            }
+        },
+        PatKind::Range(Some(start), Some(end), kind) if *kind == RangeEnd::Included => check_range(start, end),
+        _ => CharRange::Otherwise,
+    }
+}
+
+fn check_range(start: &Expr<'_>, end: &Expr<'_>) -> CharRange {
+    if let ExprKind::Lit(start_lit) = &start.kind
+        && let ExprKind::Lit(end_lit) = &end.kind {
+        match (&start_lit.node, &end_lit.node) {
+            (Char('a'), Char('z')) | (Byte(b'a'), Byte(b'z')) => CharRange::LowerChar,
+            (Char('A'), Char('Z')) | (Byte(b'A'), Byte(b'Z')) => CharRange::UpperChar,
+            (Char('0'), Char('9')) | (Byte(b'0'), Byte(b'9')) => CharRange::Digit,
+            _ => CharRange::Otherwise,
+        }
+    } else {
+        CharRange::Otherwise
+    }
+}
+
+fn is_matches_macro(cx: &LateContext<'_>, macro_def_id: DefId) -> bool {
+    if let Some(name) = cx.tcx.get_diagnostic_name(macro_def_id) {
+        return sym::matches_macro == name;
+    }
+
+    false
+}