Add lint almost_complete_letter_range

clippy_lints/src/almost_complete_letter_range.rs

@@ -0,0 +1,100 @@
+use clippy_utils::diagnostics::span_lint_and_then;
+use clippy_utils::source::{trim_span, walk_span_to_context};
+use clippy_utils::{meets_msrv, msrvs};
+use rustc_ast::ast::{Expr, ExprKind, LitKind, Pat, PatKind, RangeEnd, RangeLimits};
+use rustc_errors::Applicability;
+use rustc_lint::{EarlyContext, EarlyLintPass, LintContext};
+use rustc_semver::RustcVersion;
+use rustc_session::{declare_tool_lint, impl_lint_pass};
+use rustc_span::Span;
+
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for ranges which almost include the entire range of letters from 'a' to 'z', but
+    /// don't because they're a half open range.
+    ///
+    /// ### Why is this bad?
+    /// This (`'a'..'z'`) is almost certainly a typo meant to include all letters.
+    ///
+    /// ### Example
+    /// ```rust
+    /// let _ = 'a'..'z';
+    /// ```
+    /// Use instead:
+    /// ```rust
+    /// let _ = 'a'..='z';
+    /// ```
+    #[clippy::version = "1.63.0"]
+    pub ALMOST_COMPLETE_LETTER_RANGE,
+    suspicious,
+    "almost complete letter range"
+}
+impl_lint_pass!(AlmostCompleteLetterRange => [ALMOST_COMPLETE_LETTER_RANGE]);
+
+pub struct AlmostCompleteLetterRange {
+    msrv: Option<RustcVersion>,
+}
+impl AlmostCompleteLetterRange {
+    pub fn new(msrv: Option<RustcVersion>) -> Self {
+        Self { msrv }
+    }
+}
+impl EarlyLintPass for AlmostCompleteLetterRange {
+    fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &Expr) {
+        if let ExprKind::Range(Some(start), Some(end), RangeLimits::HalfOpen) = &e.kind {
+            let ctxt = e.span.ctxt();
+            let sugg = if let Some(start) = walk_span_to_context(start.span, ctxt)
+                && let Some(end) = walk_span_to_context(end.span, ctxt)
+                && meets_msrv(self.msrv, msrvs::RANGE_INCLUSIVE)
+            {
+                Some((trim_span(cx.sess().source_map(), start.between(end)), "..="))
+            } else {
+                None
+            };
+            check_range(cx, e.span, start, end, sugg);
+        }
+    }
+
+    fn check_pat(&mut self, cx: &EarlyContext<'_>, p: &Pat) {
+        if let PatKind::Range(Some(start), Some(end), kind) = &p.kind
+            && matches!(kind.node, RangeEnd::Excluded)
+        {
+            let sugg = if meets_msrv(self.msrv, msrvs::RANGE_INCLUSIVE) {
+                "..="
+            } else {
+                "..."
+            };
+            check_range(cx, p.span, start, end, Some((kind.span, sugg)));
+        }
+    }
+
+    extract_msrv_attr!(EarlyContext);
+}
+
+fn check_range(cx: &EarlyContext<'_>, span: Span, start: &Expr, end: &Expr, sugg: Option<(Span, &str)>) {
+    if let ExprKind::Lit(start_lit) = &start.peel_parens().kind
+        && let ExprKind::Lit(end_lit) = &end.peel_parens().kind
+        && matches!(
+            (&start_lit.kind, &end_lit.kind),
+            (LitKind::Byte(b'a') | LitKind::Char('a'), LitKind::Byte(b'z') | LitKind::Char('z'))
+            | (LitKind::Byte(b'A') | LitKind::Char('A'), LitKind::Byte(b'Z') | LitKind::Char('Z'))
+        )
+    {
+        span_lint_and_then(
+            cx,
+            ALMOST_COMPLETE_LETTER_RANGE,
+            span,
+            "almost complete ascii letter range",
+            |diag| {
+                if let Some((span, sugg)) = sugg {
+                    diag.span_suggestion(
+                        span,
+                        "use an inclusive range",
+                        sugg.to_owned(),
+                        Applicability::MaybeIncorrect,
+                    );
+                }
+            }
+        );
+    }
+}

clippy_lints/src/lib.register_all.rs

@@ -4,6 +4,7 @@
 
 store.register_group(true, "clippy::all", Some("clippy_all"), vec![
     LintId::of(absurd_extreme_comparisons::ABSURD_EXTREME_COMPARISONS),
+    LintId::of(almost_complete_letter_range::ALMOST_COMPLETE_LETTER_RANGE),
     LintId::of(approx_const::APPROX_CONSTANT),
     LintId::of(assertions_on_constants::ASSERTIONS_ON_CONSTANTS),
     LintId::of(assign_ops::ASSIGN_OP_PATTERN),

clippy_lints/src/lib.register_lints.rs

@@ -34,6 +34,7 @@ store.register_lints(&[
     #[cfg(feature = "internal")]
     utils::internal_lints::UNNECESSARY_SYMBOL_STR,
     absurd_extreme_comparisons::ABSURD_EXTREME_COMPARISONS,
+    almost_complete_letter_range::ALMOST_COMPLETE_LETTER_RANGE,
     approx_const::APPROX_CONSTANT,
     arithmetic::FLOAT_ARITHMETIC,
     arithmetic::INTEGER_ARITHMETIC,

clippy_lints/src/lib.register_suspicious.rs

@@ -3,6 +3,7 @@
 // Manual edits will be overwritten.
 
 store.register_group(true, "clippy::suspicious", Some("clippy_suspicious"), vec![
+    LintId::of(almost_complete_letter_range::ALMOST_COMPLETE_LETTER_RANGE),
     LintId::of(assign_ops::MISREFACTORED_ASSIGN_OP),
     LintId::of(attrs::BLANKET_CLIPPY_RESTRICTION_LINTS),
     LintId::of(await_holding_invalid::AWAIT_HOLDING_INVALID_TYPE),

clippy_lints/src/lib.rs

@@ -168,6 +168,7 @@ mod renamed_lints;
 
 // begin lints modules, do not remove this comment, it’s used in `update_lints`
 mod absurd_extreme_comparisons;
+mod almost_complete_letter_range;
 mod approx_const;
 mod arithmetic;
 mod as_conversions;
@@ -911,6 +912,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_early_pass(|| Box::new(duplicate_mod::DuplicateMod::default()));
     store.register_late_pass(|| Box::new(get_first::GetFirst));
     store.register_early_pass(|| Box::new(unused_rounding::UnusedRounding));
+    store.register_early_pass(move || Box::new(almost_complete_letter_range::AlmostCompleteLetterRange::new(msrv)));
     // add lints here, do not remove this comment, it's used in `new_lint`
 }